о а сорасреобкй

Published for the ее peed and
the National Science Foundation, Washington, D. С.
by Amerind Publishing Co. Ру. Ltd., New Delhi oe

This book is the first Russian work on
living mole rats and the first compendium
on fossil mole rats (Spalacidae) of the
world.

The family Spalacidae is one of the least
studied groups among the rodents of the
old world. Quite a number of works have
been devoted to the taxonomy of living
and fossil representatives of Spalacidae;
however, the major portion of these pub-
lications are in the form of preliminary
reports describing in detail new species
and subspecies.

The only major account by Mehely
(1909) on present-day mole rats published
in the beginning of the century, has be-
come out-of-date. All this has led to a
considerable complication and confusion
in the classification of the family.

Sufficient data have accumulated during
the last decade on fossil Spalacidae found
near the Black Sea and the Azov Sea of
the USSR, and some countries of western
Europe like southern Poland, Czecho-
slovakia, Hungary, and Rumania. A further
study of this material showed that the
remains of mole rats, if identified with
highest accuracy, could be of great impor-
tance in the stratigraphical break-up of

(Contd. on back flap)

Аа :
a tee М

ТТ 72-52009

AKADEMIYA NAUK SSSR
Zoologicheskii Institut
Novaya Seriya No. 99

ACADEMY OF SCIENCES OF THE USSR
Zoological Institute
New Series No. 99

FAUNA OF THE USSR:
MAMMALS

MOLE RATS, SPALACIDAE

(FAUNA SSSR: MLEKOPITAYUSHCHIE
SLEPYSHOVYE, SPALACIDAE)
VoL. 3, No. 3

У. A. TOPACHEVSKII

Nauka Publishers, Leningrad Section,
Leningrad, 1969

TRANSLATED FROM RUSSIAN

Published for the Smithsonian Institution and
the National Science Foundation, Washington, D.C.
by Amerind Publishing Co. Pvt. Ltd., New Delhi
1976

© 1976 Amerind Publishing Co. Pvt. Ltd., New Delhi

Translated and Published for the Smithsonian Institution,
pursuant to an agreement with the National

Science Foundation, Washington, D. C.

by Amerind Publishing Co. Pvt. Ltd.,

66 Janpath, New Delhi

Translator: Dr. Jayant Honmode
General Editor: Dr. V. S. Kothekar

Available from the U.S. Department of Commerce
National Technical Information Service
Springfield, Virginia 22161

Printed at Eastend Printers, Calcutta, India
Production: M. L. Gidwani

UDC 599.321: 569.321

The book reviews fossil and present-day mole rats of the family Spala-
cidae (Rodentia, Mammalia) from all over the world. The general charac-
teristics of the family, the basic adaptive characteristics of its ancestors
and the occurrence of basic adaptations in phylogeny and postembryonic
ontogeny are given. Data are presented on the distribution of this group
in the past and at present. The phylogeny of the family has been worked
out. A reconstruction of the taxonomy of mole rats has been made. A
separation of subfamilies and certain genera has been done for the first
time. A description of new taxa of different ranks has been given. IIlus-
trations—87. Tables—2. Bibliography—210 names.

Editor-in-Chief
ACADEMICIAN B. E. BYKHOVSKII

Editorial Board
I. М. Gromov (EDITOR FOR THE VOLUME),
А. $. MONCHADSKII, О. A. SKARLATO,
A. A. STRELKOV, А. A. SHTAKEL’ BERG

FOREWORD

This book is the first Russian work on living mole rats and the first
compendium on fossil mole rats (Spalacidae) of the world.

The family Spalacidae is one of the least studied groups among the
rodents of the old world. Quite a number of works have been devoted to
the taxonomy of living and fossil representatives of Spalacidae; however,
the major portion of these publications are in the form of preliminary
reports describing in detail new species and subspecies. In the majority
of such cases, the descriptions are not based on detailed research and
hence they constitute sporadic efforts. If to this is added the incomplete-
ness of precise criteria in the identification of species, sub-genera, and
genera not to mention subfamilies, then the abundant synonyms appear-
ing in special literature becomes clear. The only major account by Mehely
(1909) on present-day mole rats published in the beginning of the century,
has become out-of-date. All this has led to a considerable complication
and confusion in the classification of the family. The plan of Mehely, or
its variation made by Ognev (1947) without additions and reconstructions,
is mainly used in the work of foreign specialists and also by many zoolo-
gists at home. Though old, it is quite adequate and coordinates the sub-
generic categories and the species composition of the group as a whole.
But in practical textbooks, like guides on the rodents and the mammalian
fauna of the USSR and, also, in individual works on the mammalian
fauna of the USSR, greatly simplified variations of this scheme have been
used and as a result, many species appear to have been demoted to the
level of subspecies without proper justification.

Moreover, the mole rat family has a specific economic significance
because all its present representatives are the destroyers of field and garden
crops, forage crops, and garden and forest plantations. The destruction
brought about by the Spalacidae is increasing in the southern region of the
USSR under conditions of intensive field-protecting forest belts. In addi-
tion, the mole rats act as hosts to both endo- and ecto-parasites which, in
their turn, are either pathogenic to man and farm animals, or are carriers
of transmissible diseases.

Sufficient data have accumulated during the last decade on fossil Spala-
cidae found near the Black Sea and the Azov Sea of the USSR, and some
countries of western Europe like southern Poland, Czechoslovakia,
Hungary, and Rumania. A further study of this material showed that
the remains of mole rats, if identified with highest accuracy, could be of

vi

great importance in the stratigraphical breakup of Neocenic and Anthro-
pogenic continental deposits in the southern region of the European part
of the USSR and adjacent territories. Taking into consideration also the
Pontiac origin of the Mediterranean Sea and the present distribution of
Spalacidae, it is self-evident that the evolution and geographical distri-
bution of the family in the past, and at present, were dictated by a distinct
influence—mainly by the contours (Sarmatian, Miocean, and Pontiac
Seas) of these basins during their entire geological history. As a result,
data on the past and present distribution of individual representatives of
the group, based on the firm foundation of a natural system, can greatly
aid in paleogeographical profiles so important in geological practice.

Finally, a detailed study of this group of rodents, absolutely specialized
for an underground mode of life, has great theoretical interest because
it is accompanied by an interpretation of the adaptive significance of most
of the important systemic traits and, also, the main stages of their develop-
ment and the direction of that development in phylogeny. A study of
individual morphological structures associated with the specificity of a
burrowing cycle in mole rats can also serve as the starting point for
further work in the field of simulation of such systems into operative
practice.

As such, a monographical study on mole rats at this stage is, in our
opinion, justified. Naturally, maximum attention should be paid to the
taxonomy and phylogeny of Spalacidae because they are the least studied
members of the group as a whole.

Many serious difficulties arose during the writing of this book. In addi-
tion to the above-mentioned incompleteness of specific criteria for the
separation of taxa, starting from the subfamily and ending with species
identified by various synonyms at every possible taxonomical level, the
formation of a general compendium for fossil and living forms also rests
on the problems of taxonomy and parataxonomy. This contradiction
between zoological and paleozoological classifications can only be resolved
by bringing all the different taxonomical groups of fossil and living organ-
isms under a uniform criterion. Considering this, the author has made an
attempt in the present work to describe, wherever possible, subfamilies, .
genera, subgenera, and species at one level, and has also included the
fossil forms.

Naturally, the development of a unified classification at this time should
be based on a very clear understanding of the main trends of specialization
in this group during evolution, because the taxonomic subgrouping within
the group reflects, in fact, the varying degree of this specialization. In
this regard, the specialization of mole rats for obtaining food exclusively in
underground conditions accompanied by a greatly developed adaptability
for burrowing, will be the dominant factor. The specificity of the burrow-

Vii

ing cycle of Spalacidae consists of digging with incisors, and throwing
the dug out earth from the burrows and food inlets with the help of
specific movements of the head and the anterior girdle of the links. In
this way the formation of the natural system of mole rats is firmly related
to an intensive study of the comparative and evolutionary aspects of
structural modifications in the skeletal and muscular system which helps
in the burrowing cycle, with a maximum interpolation of data obtained
on living and fossil forms. The first in this category of systems is the
whole mechanism of the masticatory apparatus of the mole rat, which is
the basic organ for burrowing, and also a number of structures which
assist in the second stage of the burrowing cycle, i.e. the throwing out
of earth combined with complex morphological features of the skull,
the neck, the thoracic parts of the vertebral column, and the anterior
girdle of the links which help in bringing about a specific coordination
in the movements of the atlantal axial-cranial, shoulder, and elbow joints
(in conjunction with movements and defensive functions). It is also very
important in taxonomy to study the mechanisms associated exclusively
with feeding, primarily the structural development of permanent cheek
teeth during evolution. However, these developments depend mainly upon
the formation of the burrowing structures of the masticatory apparatus
as a whole and, in my opinion, should be studied together with the latter.

Along with other mechanisms forming the general complex of burrow-
ing adaptations, the structure of the masticatory apparatus has been
mainly considered as the basis of systematics for the Spalacidae. This
has made easier the preparation of a single classification for fossil and
living forms because these structures have been more fully studied in
present forms, and better preserved than other organs in fossil individuals
of the group.

It is expedient to point out that the original systematics of Spalacidae
proposed in this manual are, naturally, far from perfect. However, at the
present stage of research based on specific factual data on this group as
a whole, it seems to us that it is quite up-to-date and reflects the coordi-
nation and correlation of taxonomical subdivisions of different taxono-
mical levels in the whole family.

The commonly used methods of morphometry have been used in this
work. The explanation of different measurements, indices, and similarly
some of the specific details in the structure of the skull, lower jaw, teeth,
and bones of the skeleton, have been explained through figures wherever
necessary in the course of description. The abstract numbers in the text
indicate the indices in percents. The number of examples taken for measure-
ments, in the majority of cases, coincides with similar material available
to us.

The so-called geochronological scheme for the Neocene and Anthro-

Vill

pogen of Europe has been used by the author as in all his previous works.
Its correlation with other schemes presently in vogue in literature is
depicted in Figure 38.

Data from research on living representatives of this family from all
over the world, and almost all the fossil forms, have been used while
writing this monograph. Data which could not be obtained, especially on
fossil mole rats from a number of places under excavation in western
Europe, have been taken from literature. The author has made collections
of fossil and present-day Spalacidae which are preserved in the following
institutions of the Soviet Union and abroad:

. Institute of Zoology AN Ukraine SSR;

. Institute of Zoology AN SSSR;

. Zoological Museum of Moscow State University;

. Zoological Museum of Kiev, Odessa, and Chernovits State Univer-
sities;

5. Institute of Zoology AN Moldavian SSR;

6. Zoological Museum in the University of Humboldt in Berlin (German

Democratic Republic);
7. Storing places in the USSR, Great Britain, France, and the United
Arab Republic.

The present work has been carried out on behalf of the Institute of
Zoology AN Ukraine SSR. The author is grateful to I. M. Gromov, Head
of the Department of Mammals of this Institute, for acting as a consultant
and giving constant direction and assistance in obtaining scientific data
from different zoological institutes in this country and abroad; and also,
to all the co-workers of this laboratory who contributed to the successful
publication of this work. We are greatly indebted to the Head of the
Department of Paleozoology of the Institute of Zoology AN Ukraine
SSR; to corresponding member of the AN Ukraine SSR, Professor I. G.
Pidoplichko, for invaluable consultation and help in the work; and also
to all the colleagues and co-workers of this department who have taken
part in the collecting and processing of data. The author is likewise grateful
to Professor V. G. Geptner, Professor A. P. Korneeva, and scientific
workers E. I. Yangolenko and M. N. Lozan for granting access to data
collected by them. Sincere appreciation is expressed to Professor A. A.
Strelkov who examined the manuscript of this book.

The majority of the figures have been drawn by S. L. Shmuilovich,
artist of the Department of Mammals of the Institute of Zoology AN
SSSR, and part of the illustrations have been drawn by the author.

BRWN =

CONTENTS

Foreword
Taxonomical Index of Species

PART I: INTRODUCTION

A SHORT MORPHOLOGICAL DESCRIPTION OF THE FAMILY
SPALACIDAE
GENERAL NATURE OF THE MAJOR ADAPTATIONS OF MOLE RATS
Adaptive Characteristics of the External Features, Hair
and Sense Organs
Morpho-functional Characteristics of the Dentition of
Mole Rats with Reference to Adaptation toward Bur-
rowing and Feeding
Arrangement of the Skeletal and Muscular Systems of the
Skull and the Postcranial Skeleton of Mole Rats for
Transportation and Throwing out of Soil with the Help
of the Head
Certain Characteristics in the Structure of the Limbs of
Mole Rats Related to Adaptations for Ejecting
Loosened Earth during the Process of Digging
A Short Account of Adaptive Changes of Certain Struc-
tures of the Skull and the Skeleton in the Evolution of
Mole Rats
CHANGES IN CERTAIN STRUCTURE OF THE SKULL OF MOLE
RATS DUE TO AGE. SEXUAL DIMORPHISM
ECOLOGICAL FEATURES OF MOLE RATS, THEIR REPRODUCTION
AND SIGNIFICANCE TO HUMAN BEINGS
Habitat and Population Numbers
Burrows
Food
Reproduction
Mode of Life
Foes, Parasites and Epidemiological Significance
Significance of Mole Rats for Man

28

32

46

61

64
12

80
80
85
90
93
95
96
OS

X

A SHORT OUTLINE OF THE GEOGRAPHICAL DISTRIBUTION OF
MOLE RATS ue 100

AN OUTLINE OF THE PHYLOGENY AND GEOLOGICAL HISTORY
OF MOLE RATS. IMPORTANCE OF THE REMAINS OF SPALA-
CIDAE FOR A STRATIGRAPHIC DESCRIPTION OF NEOCENE AND

ANTHROPOGENE CONTINENTAL DEPOSITS OF EUROPE ie 1D}
CLASSIFICATION an 130
BIBLIOGRAPHY ae 134

PART II: TAXONOMY 151-301

Index of Latin Names 303

Вы

TAXONOMICAL INDEX OF SPECIES

FAMILY SPALACIDAE
1. Subfamily Prospalacinae
1. Genus Prospalax Mehely

. P. priscus (Nehring)
. Р. rumanus Simionescu

2. Subfamily Spalacinae
1. Genus Microspalax
1. Subgenus Microspalax

. ehrenbergi (Nehring)

. compositodontus W. Topachevskii
. Macoveii (Simionescu)

. odessanus W. Topachevskii

аа

2. Subgenus Mesospalax

. nehringi (Satunin)
. leucodon (Nordmann)

<

2. Genus Spalax

. 5. giganteus Nehring

. 5. arenarius Reshetnik

. 5. microphthalmus Gildenstaedt
. 5. polonicus Mehely

. S. graecus Nehring

. S. minor W. Topachevskii

158
162

177
188
192
204

212
222

287
248
256
269
280
290

PART I
INTRODUCTION

MAIN STAGES IN THE HISTORY OF RESEARCH IN THE
TAXONOMY OF MOLE RATS (SPALACIDAE GRAY, 1821)
AND THE MOST IMPORTANT SCHEMES FOR THEIR
CLASSIFICATION

Giildenstaedt (1770) who identified the genus Spalax and described
_ the species of common mole rat (5. microphthalmus Gild.), initiated taxo-
nomical investigations of mole rats.

The family Spalacidae was identified by Gray later (1821). Until then,
Pallas (1778) included mole rats in the genus Mus as a subtype of “‘under-
ground mice’ (Mures subterranei), along with Myospalacinae and the
African Bathyergidae. Illiger (1811), who first proposed dividing the fami-
lies within the limits of the order Rodentia, considered Spalacidae as mice
along with marmots, hamsters, and batiergids. Waterhouse (1839a, 1839b,
1842, 1848), without observing that his series of works appeared twenty
years after the publication of Gray’s (1821), described mole rats as close
to Arvicolidae, and artificially attached beavers and Geomyidae to this
family. However, he subsequently reconsidered this nomenclature and, as
a result, in his later works mole rats were included in the family Muridae
as an independent subtype, Spalacina. Thereafter, until the publication of
a major monograph on rodents by Tullberg (1899), no common approach
was used by different authors to trace out the taxonomical rank of the
group of mole rats. Though the majority of researchers were inclined
like Gray to consider Spalacidae as an independent family of the group
Myoidea (Brandt, 1855; Lilljeborg, 1866; Alston, 1876; Thomas, 1896;
and others), still some authors traced them as a subfamily of the family
Muridae (Gill, 1872). Tullberg (1899) quite clearly determined the posi-
tion of Spalacidae as rodents in the family group Myoidea. Afterwards,
a similar classification was also given by Miller and Gidley (1918), Weber
(1928), Ellerman (1940, 1941, 1949a, 1949), Simpson (1945), Wood (1947),
and subsequently Schaub (1968), I. М. Gromov and А. A. Gureev (1962).
An unsuccessful interpretation of the taxonomical position of this family
is found in the work of Winge (1887, 1941) who joined Spalacidae with
jerboa (Dipodidae) as a subfamily. As will be shown later (page 113), a
little similarity in the structure of the permanent cheekteeth and some
individual skull structures between jerboa (Dipodidae) and mole rats

4

indicate the preservation of ancient traits of the branches which had been
separated long ago, and the genetic proximity of their Eocene ancestors.
Afterwards, the specialization of these trunks of Myoidea continued in
different directions until no basis was left for the joining of the representa-
tives of these groups under one family. An unsuccessful placement of the
family has been done in the latest and major compendium on rodents
fauna of the world by Grasse, Dekeyser and Viret (1959), who artificially
relate Spalacidae and Rhizomyidae to the joint group of Palaeotrogo-
morpha incertae sedis along with Thrynomyidae, Eupetauridae, Petro-
myidae, and Bathyergidae.

Tullberg (1899), and the majority of his predecessors, examined the
family Spalacidae in considerably greater detail than is done at present,
by artificially inserting in this group Rhizomyidae and Myospalacinae—
usually independent taxonomical subdivisions of the rank of subfamily.
The separation of Rhizomyidae and Myospalacinae from the composi-
tion of the family Spalacidae, first as a separate family, and second, as a
subfamily Cricetidae which is close to Microtinae, was kept by Miller
and Gidley (1918) though the prerequisites for this were laid in the still
earlier publications of Brandt (1855), Winge (1887), and Thomas (1896),
who considered Rhizomyidae to be in the family Spalacidae in the form
of independent taxonomical subdivisions (Rhizodontes, Brandt; Rhizo-
myini, Winge; Rhizomyinae, Thomas), and Lilljeborg (1866) in the same
way, as done in the case of Myospalacinae. However, the old scheme of
Tullberg has been used for quite some time by scientists both here (Russia)
and abroad (Mehely, 1909; Weber, 1928; Reshetnik, 1941; Ognev, 1947;
Afanasev et al., 1953).

The basis for generic, subgeneric, and species taxonomy, in addition
to the above-mentioned publication of Giildenstaedt (1770) for modern,
subfossil, and partially fossil representatives of Spalacidae, was laid by the
works of Nordmann (1840, 1858), Nehring (1897, 1898a, 1898b), K. A.
Satunin (1898), and Mehely (1909); and for fossil forms by Mehely (1908),
Simionescu (1930), and Kormos (1932) who, notwithstanding some syno-
nyms, worked out the species and subspecies classification of the group
as a whole and mainly determined its species composition. Of the works
mentioned above, the work of Mehely (1909) deserves special mention
for his synthesis of the uncoordinated knowledge of present mole rats of
the world contained in the works of his predecessors. A basis for the
subgeneric classification of the genus Spalax is laid in this monograph,
though its prerequisites were laid down in the publications of Nehring
(1897) who suggested the separation of small mole rats into a subgenus,
Microspalax. If one adds to this the genus Prospalax described by
Mehely a few years earlier (1908), then the coordination of generic and
subgeneric groups, together with the species composition of the family,

would appear as follows:

Family Spalacidae Gray, 1821

Genus Prospalax Mehely, 1908
P. priscus (Nehring, 1897)

Genus Spalax Giildenstaedt, 1770

Subgenus Microspalax Nehring, 1897
S. ehrenbergi Nehring, 1897
S. fritschi Nehring, 1902

Subgenus Mesospalax Mehely, 1909
S. monticola Nehring, 1898
S. hungaricus Nehring, 1898

Subgenus Macrospalax Mehely, 1909 ( = Spalax s. str.)
S. graecus Nehring, 1898
5. istricus Mehely, 1909
iS. polonicus Mehely, 1909
S. microphthalmus Giildenstaedt, 1770
S. giganteus Nehring, 1897

Afterwards, the fossil representative of the genus Prospalax—Mid-
Pliocene P. rumanus Simionescu—described by Simionescu (1930), and
the fossil Pliocenic European mole rats, close to the recent Afro-
Asiatic M. ehrenbergi, separated into a distinct genus Pliospalax
Kormos by Kormos (1932), were added to the above-mentioned list
[though Simionescu (1930) previously considered his as a form of the
species P. macoveii Simionescu in the genus Prospalax]. Zoologists at
home—V. I. Radugin (1917), K. A. Satunin (1920), and E. G. Reshetnik
(1939, 1941) scrupulously followed the same classification in their works
devoted to the study of the taxonomical position of mole rats of the
fauna of the USSR. The classification of S. I. Ognev (1947) is quite similar
to that of Mehely, differing only in details. Ognev, not knowing about the
recent collections of the Afro-Asiatic M. ehrenbergi, joined the subgenera
Microspalax and Mesospalax without proper basis. In addition to this,
the species composition of the genus Spalax was completed by the new
species, S. arenarius Reshetnik, described earlier by Reshetnik (1939) in
the form of a subspecies, S. polonicus Mehely. A simplified version of
Mehely’s classification has been used in recent reviews by Simpson (1945),
Ellerman (1949a) and Schaub (1958), who add three genera in the composi-
tion of the family—Prospalax Mehely, Pliospalax Kormos, and Spalax
Giildenstaedt. Afterwards, the species composition was filled in with
fossil forms (Topachevskii, 1957a, 1959, 1965). In his last publication,
this author attempted to revise the systemic position of Middle Pliocenic
mole rats from northwest of the Black Sea, separated by Kormos, as has
been indicated above, into an independent genus Pliospalax.

Mehely’s classification, along with subsequent additions, reflects the
level of our present knowledge of this group fairly well. However, it
appears to be an old one today from many angles—primarily due to the
addition of new data on living forms and fossil representatives of the
family. A detailed morpho-taxonomical study of the vast material on fossil
and living mole rats of the world available in the collections of different
institutions of USSR as well as in foreign stores, on the characteristics
of past and present distributions of representatives of individual taxo-
nomic subdivisions, and the phylogenetic relationship between individual
groups within a family, together with the newest paleontological data,
has made it possible to determine that the classification put forth above
has a number of shortcomings such as:

1. The depth of the differences between Prospalax and Spalax (in the
dimensions accepted by Mehely and all subsequent researchers) many
times exceeds the criterion of a genus. Because of this, it is proper to
divide Spalacidae into two independent subfamilies—Prospalacinae (extinct
ancient mole rats) and Spalacinae (living mole rats).

2. The representatives of the subgenera Microspalax and Mesospalax
have some common primitive peculiarities in the structure of the skull and
skeleton, which brings them closer between themselves, and separates them
in principle from those large mole rats of the subgenus Spalax. Because
these traits correspond to the criteria of the genus, two generic groups are
separated further from the composition of the subfamily Spalacinae—
Microspalax Nehring (with subgenera—Nominal and Mesospalax Mehely),
and Spalax Giild.

3. The fossil ‘Pliospalax Kormos, remains of which are found in deposits
of the Middle and Upper Pliocene of the northeast region around the
Black Sea are, in principle, similar to other living Afro-Asiatic repre-
sentatives of the nominal subgenus of the genus Microspalax. Hence, its
separation into an independent genus, as done by Kormos (1932), is
hardly justifiable at the present level of study. In all probability, this
group of mole rats will have to be placed under the above-mentioned
subgenus of the genus Microspalax.

4. The number of present-day species (including the partly fossil) is
unnecessarily overstated. Differences between the following pairs of species
— М. ehrenbergi Nehr. and М. fritschi Nehr.; М. monticola Nehr. and М.
hungaricus Nehr.; and finally, 5. graecus Nehr. and 5. Istricus Mehely—
described by Nehring and Mehely from only single examples, as seen from
investigations of the series, in the majority of cases do not show up in,
for example, the appearance of individual or sharp geographical variability
and, as a result, the second name in the pairs has to be taken as a synonym
for the first. This list contains some other deliberate synonyms. As shown
in the investigations of Reshetnik (1941), M. monticola Nehring has to

be named М. leucodon Nordmann, after Nordmann (1840).

Taking into consideration the facts enumerated above, a reconstituted
classification of the family Spalacidae has been given in the concluding
part of this Introduction, in accordance with the present level of knowledge

(page 130).

A SHORT MORPHOLOGICAL DESCRIPTION
OF THE FAMILY SPALACIDAE

Description: Rodents of average dimensions, having characteristics
greatly adapted to underground life, comprise the family of mole rats,
Spalacidae. The body length of representatives of this group varies from
130 to 350 mm. The body is cylindrical, the feet short, and the neck is
not well defined. The head thickens toward the top and is shaped like a
narrow wedge. On the sides of the head, two skinny borders covered with
hard bristles appear (Figure 1). The rather large eyeballs are hidden under
the skin; the external ear differs from that of other rodents in being a
vestigial skin fold. The large incisors are separate from the oral cavity
(Figure 2), and are not confined to this cavity during digging activity. The
tail is vestigial and not externally visible. The limbs are penta-digital; all
digits are well-developed and have rounded claws. The hair is dense and

Figure 1. Spalax arenarius Resh. Photo by A. I. Gizenko.

weakly differentiated into coarse wool and under wool. The color is
monotonous—from light-gray-straw to an appreciably darker brown. The
majority of mole rats are similarly colored. A few differences are observed
when large numbers of hides are examined. However, the overlapping in
traits between separate species is so dominant that it is practically impos-
sible to differentiate them by color. The giant mole rat is an exception;
its fur color differs from that of other species.

The individuals of the genus Microspalax display the following kinds
of coloring. The upper part of the head, the back, and the sides of mole
rats Ehrenberg and Nehring, are a pale yellow-gray-buff with a light
reddish tinge. The base of the hair is an intense gray. The area around the

Figure 2. Construction of lips in mole rats. x 1.6.

nose and eyes, and near the cheeks, is of a light mouse-gray color. The
ventral part is lighter than the back and is generally mouse-gray. The
short whiskers are pale yellow. There are some specimens with a pre-
dominance of reddish and buff coloring on the back and sides. The young
are always colored a bit darker than the mature and old.

The coloring of the white-toothed mole rat is very similar. However,
the reddish tinges of the back are fainter than in the preceding species.
On the whole, the representatives of the given type are characteristically
buff-gray, sometimes even having a light yellow-buff fur. The front portion
of the head, neck and body is grayer than the back.

Among representatives of the genus Spalax, the Podolsk and Bukovin
mole rats have a similar coloration. There are quite a few similarities also
between the coloration of the above-mentioned species and the white-
toothed mole rat. For example, the posterior section of the head, back,
and sides of a mature common mole rat is characterized by a pale yellow-
gray-buff tinge. The base of the hair is mouse-gray, but as the ends of the

9

hair wear away, the fur assumes a grayish tinge. The anterior portion of
the head and neck is lighter than the back. Sometimes a white patch
with a yellowish tinge is observed in the area of the forehead. The short
whiskers are a pale-white-yellow, and the long ones are a whitish yellow.
The ventral portion in the area of the throat, the chest, and the anterior
portion of the stomach are mouse-gray; in the middle and posterior parts,
it is pale-yellow-buff. The winter fur is up to 14mm in length, and the
summer fur, 10 to 11 mm. In the young, a gray tinge predominates along
with a faint pale-yellow on the hair endings. The ventral part is intensively
gray. According to S. I. Ognev (1947), the common mole rat found around
the Saratov region differed from representatives of this species from the
left bank of the steppes and forest steppes of the Ukrainian Soviet Socialist
Republic, the central regions of the Russian Soviet Federal Socialist
Republic, and the West Caucasus, by a total absence of buff-pale-yellow
tinges in coloration, and by the presence in 80% individuals of a trans-
verse white band in the occipital region, expressed in different degrees
(starting from the base of the nose and proceeding along the forehead
and occiput up to the neck). White fur appears around the mouth and
partially on the cheeks. On the other hand, the ventral side of the body
of the common mole rat from the Saratov region is darker than those
from the region of Ukraine, the central black soils, and the West Cau-
casus. The throat and chest are of an intense gray color. The hair of the
stomach and the surrounding areas is tinged pale-yellow-buff. Irregular
white spots in the region of the chest and the posterior portion of the
belly were observed in many cases. The phenomenon of albinism is rarely
observed in the common mole rat.

In terms of coloration, the sandy mole rat takes a middle position
between the common Podolsk and the Bukovin mole rat on the one hand,
and the giant mole rat on the other. On the whole, this species is usually
lighter in color than representatives of the group microphthalmus. Fre-
quently, the posterior section of the head, back and sides of the body of
mature animals is a pale-yellow-gray color. The base of the hair is gray.
A whitish gray tinge with a pale-yellow tinge is predominant in the region
of the forehead and cheeks. The fur of the ventral region is gray with a
mixture of pale yellow-yellowish lines in the belly.

Finally, the lightest colored form is represented by the giant mole rat.
The back and sides of the body are characteristically an extremely faint
pale-gray, yellow-silver color. The head, in the region of the forehead,
occiput, and cheeks, is of a faint, bright silvery-white tinge, with a slight
yellow coloration. The lower portion of the body is grayer than that of the
upper. The base of the hair is gray. Gray tinges are more predominant in
the coloration of the young.

Data on the moulting of mole rats is extremely inadequate. It is only

10

known that the thick winter fur of the common mole rat changes into a
rather thin summer cover in May to June, and the autumn moulting takes
place in September (Ognev, 1947). In my opinion the spring and autumn
moulting in the Bukovin white-toothed mole rat is rather more pro-
longed. According to E. I. Yangolenko (1965) the spring moulting of
the foregoing species takes place from March to May and the autumn
one from August to November. The change of hair in males takes place
quicker than in females. The young moult later than the older. The most
intensive moulting occurs in March and the autumn moulting takes place
in September. The sequence of moulting in mole rats of different species
is almost similar. Initially the occipital region and the middle of the back
begin to moult, then the shoulders and body, and finally the sides and
belly. Moulting is accompanied by a darkening of the fleshy side of the
hide and formation of black spots.

The skull is wedge-shaped from above and from the sides, with a very
long facial section and a shortened brain area; the length of the facial
section significantly exceeds the brain area. Differing from representatives
of the majority of other families of rodents, except some Oligocenic Cylin-
drodontidae, the occipital surface is highly developed, widened, thickened,
and considerably inclined in front, placing itself in relation to the pro-
longed line of teethrows at approximately a 45° angle. The width of the
occipital surface significantly exceeds the length of the braincase and the
apex of the lambdoid crest is situated approximately at the level of the
winged bone processes (Figure 3). The rostrum is low and wide. Its least
height is significantly less than its width. The nasal bones are long and
narrow; their length is twice that of the upper row of permanent molars,
and more than twice the greatest width of these bones (usually 24 times).
The edges of the nasal bones protrude significantly in front of the edge of
the submaxillary bones (Figure 3). The orbit socket is large; its height is
significantly greater than its width. In addition, the former, as a rule, is
more than the combined length of the two front permanent molars, or
approaches to it. The suborbital canal is present in representatives of the
primitive subfamilies of the ancient mole rats (Prospalacinae) and is
absent in the true mole rats (Spalacinae). Comparatively the zygomatic
arches are poorly developed and are widely placed (Figure 3) with a slight
downward bend. The base of the malar processes of the maxillary bone
is slightly elevated in relation to the alveolar edge (Figure 3). The malar
bone is very small and does not come in contact with the lacrimal. The
supraorbital processes of the frontal bones are absent. In place of the
infraorbital tubercle, there are vestigial short crests. The sagittal and
longitudinal crests are well-developed; moreover, the latter is situated
at the level of the posterior ends of the zygomatic arches and are com-
parable to them in width. The incisorial sockets are significantly shifted

11

backward, and consequently the posterior length of the hard palate
(measured from the posterior edge of the incisorial sockets or cavities)
is less than half of the anterior length (measured from the anterior
edge of the incisorial sockets). The masseter area is narrow (length is
less than the similar area of the two anterior permanent molars), with

F G

Figure 3. Spalax giganteus Nehr. Х1.2.

A—axial skull from above; B—the same from below; C—the same from

the side; C,;—malar angle; D—lower jaw from outer side; E—the same

from inner side; F—rostral section of skull, anterior view (diagrammatic) ;
G—lower jaw, posterior view (diagrammatic).

12

а sharply outlined (in the form of а crest) anterior edge situated at
almost a horizontal level. The crest of its anterior edge never reaches the
sutures between the premaxillary and maxillary bones (Figure 3). In addi-
tion, the anterior edges of the masseter area show a considerable deviation
in the posterior section of the diastemic palate (Figure 3). The planes of
the processes of the winged bones are almost parallel. The winged processes
of the wedge-shaped bones (Figure 4, п) are narrow; the distance between

the anterior boundary of the

fossa pterygoidea and crista

pterygoidea (posterior edge
iii of the for. orbitorotundum)

К
AC ne AN AS does not exceed half the
S ` 52, NY 7) . Е
AS ‘4 VG WOE V anterior width of the nasal

~
SS, | « = bones. The winged fossacoin-
INN cides correspondingly with
Й А the foramen rotundum and
the brain cavity. Differing
from the majority of other
families of the order, there
are two areas on the skull for
articulation with the lower
jaw. The true articulating
area (fossa glenoidea; Figure
4, 1) is placed anteriorly to
the false one (fossa pseudo-
Figure 4. Structure of the articulating surfaces glenoidea; Figure 4, iii) and

of the skull with lower jaw in (A) Spalax and sharply stretched inth
(В) Rhizomys. X1.8. ре ed in the same

<

Of] A у
а AY ; Y, i.
м» 22, tte, 77!"

direction; its length exceeds
i—natural articulating surface; ii—wing-like that of the permanent mol-
process of wedge-shaped bone; iii—false arti- ars. During digging and mas-

culating ae о plate of the ticating, the lower jaw is
fixed on it (anterior posi-

tion). The malar process of the temporal bone is poorly developed and,
consequently, the articulating surface does not extend to the zygomatic
arch (Figure 4). The false articulating fossa is formed by the auditory
bullae and the petromastoideum, and corresponds to the position of the
jaw during mastication and inactivity (the posterior position of the lower
jaw). The combined length of the true and false articulating surfaces is
more than one and a half times the length of the line of permanent molars.
The auditory bullae are small, compact, comparatively thick-walled, and
lie in a horizontal position. Their external edges protrude; the external
auditory meatus is situated approximately at the level of the occipital
condyles and does not project laterally in relation to the occipital surface

13

(Figure 4). The dorsal edge of the bulla is expanded into an articulating
plate (Figure 4, iv), forming the ventral portion of the false articulating
fossa. The mastoid bones are comparatively large, bulging, and placed
low; the proc. mastoideus is external to the proc. paroccipitalis situated
at the same level as the latter; the greatest height of the petromastoideum
exceeds the length of the permanent molar line. The for. magnum is
situated low; its height is approximately more than twice that of the
occipital surface, measured from the upper boundary of the for. magnum
to the apex of the lambdoid crest. The occipital condyles touch each
other. The proc. paroccipitalis is weakly developed (Figure 4).

The lower jaw has an elongated articulating process turning sharply
backward and inward, the longitudinal axis of which corresponds to the
similar one of the horizontal branch (Figure 3). The length of the proc.
condyloideus either exceeds the length of the lower line of permanent
molars or approximates it. The coronary process is long, broad, and bent
like a sickle; its anterior boundary is situated perpendicularly along the
longitudinal axis of the jaw. The coronate articulating pattern is wide;
its greatest width along the chord exceeds the length of the lower line of
permanent molars, or is about equal to it. The alveolar process is always
well-developed, and is less in height than its articulating one (subfamily
Prospalacinae), or approximately equal to it or larger (subfamily Spala-
cinae). The structure and position of the coronary process vary. In
representatives of a primitive subfamily of ancient mole rats, it is situated
at the base of the corresponding process and has a common border with
it; the posterior pattern of the jaw is well-developed (Figure 40). The
length of the coronary process in this case may significantly exceed the
combined length of the two anterior permanent molars; the sella externa
is always absent (Figure 40). In true mole rats, the coronary process is
shortened, displaced laterally and situated on the external wall of the
alveoli; the posterior pattern is absent; the sella externa is always present
(Figure 3).

In the works of the majority of the older authors (Tullberg, 1899;
Mehely, 1909; and others), and also in some of the comparatively recent
reviews on world fauna of rodents (Ellerman, 1940; Grasse, Dekeyser and
Viret, 1955), the dental formula of Spalacidae has been interpreted as
follows: и С Ро М? (total, 16 teeth). This formula has been used until
now in Russian research also (Ognev, 1947; Gromov, 1962; Gromov её
al., 1963). However, Stehlin (1923) is inclined to consider the anterior
molar tooth as Pi (Py according to the scheme in general use, because the
said author stuck to the order of nomenclature of premolar teeth in the
reverse direction). On the whole, the dental formula looks like this:
It Ce Pi М5. This formula was used in subsequent works by Stehlin and
Schaub (1941), and also in Schaub’s most recent review (1958) on fossil

14 Л

rodents of world fauna. Such an interpretation of the dental formula of

mole rats has quite a firm foundation because Stehlin (1923) very confi-

dently proved the fact of the change of the anterior lower molars in Oligo-

cenic rhizomys from the group of Rhizospalacidae which, in all probability,

is the origin of mole rats. The presence of a vestigial additional tooth

situated behind the proposed МЗ (Figure 5) in the upper toothrow of

present-day mole rats of the genus Spalax, observed by us sometime back,

may also serve as a partial proof for this. However, it is not ruled out

‚ that the aforesaid could be an

ah accidental deviation from the

М. normal because the presence of

аш } additional teeth has sometimes

JES IA AAA ASSES 3 ea
been observed in other families of
Е Ns ee rodents and also in hare-like ani-
и 5 го ni ы

in Seale ee Ran ath additional а tooth has к.

и о ance of a small pin with one root

with a sharply reduced crown

resembling P* of some Dipodidae in its general outline. Its alveolus is

very small, almost a superficial fossa; as a result, this tooth is easily lost
during the preparation of skulls.

All the aforesaid confirms, as it were, Stehlin’s idea. However, the
dental formula proposed by him for Spalacidae warrants a review of the
dental formula for all families forming the suborder Myoidea and fore-
most, for the fossilized Eocene Cricetidae among which one is likely to
find common ancestors for Rhizosomidae and mole rats. The latter
(Eocene Cricetidae) do not fall within the purview of the present research.
Hence to avoid unnecessary complications, we will start from the generally
used dental formula naming, for the time being, the fourth molarized
premolar My.

The upper and lower incisors are very strong and wide; their combined
width, and individual width, respectively exceeds the combined length of
the two permanent molars or, in the first instance, is equal to it, and in
the second, is equal to Mi.

The molar teeth have a pterydomidal! structure, and the crown is of
average height. The roots have a tendency to fuse in highly specialized
representatives. The dimension of the teeth increases in a forward direc-
tion. The masticating surface is folded; the original tuberculate type of
its structure becomes evident only at the initial stage, before wearing
starts. Originally, the upper permanent molars were characterized by the
presence of one loop and two tubercles—protocone and hypocone—in
the internal line; there are two to three loops of anterior and posterior

1 The fine tuberculated type of construction of the permanent molars is closer to the
original one for rodents (Stehlin and Schaub, 1951; Gromov, 1962) (Figure 6).

15

openings, the paracone, mesocone, and metacone оп the outer side (Figure
6). However in the majority of cases, the paracone has a tendency to fuse
with the anterior inlet, the metacone with the posterior, and the mesocone
gets reduced, having the greatest development only in the primitive
representatives of the family. The loops, because of their wearing out,
have a tendency to lock into marks as a result of tooth rubbing. The
process of mark formation takes place more quickly in specialized than in
primitive representatives of the family. In phylogenetic lines and with age,
the contour of the surfaces of the permanent molars, in different succes-
sions, takes on a W-, Z-— or S-, Е- and C-type of outline. The lower

Figure 6. Microspalax compositodontus sp. поу., Late
Miocene of South Ukraine.

Upper and lower permanent molars: /—hypocone; 2—
hypoconid; 3—posterior collar; 4—mesocone; 5—meso-
conid; 6—metacone; 7—metaconid; 8—paracone; 9—
anterior collar; 10—protocone; //—protoconid;
12—entoconid.

permanent molars originally have one or, rarely, two (if the vestige of the
anterior loop is to be considered, which happens when the second one is
highly developed) loops, and two tubercles—protoconid and hypoconid
—in the outer side, and one or two loops, anterior and posterior collars,
and a metaconid, mesoconid, and entoconid in the inner side (Figure 6).
As in the upper permanent molars, the structure of the teeth simplifies
with age because of the fusion of the metaconid with the anterior collar,
the entoconid with the posterior collar, reduction in the mesoconid and
the anterior loop of the outer side, with a subsequent locking of the loops
into marks with contours on the surface, principally in the same manner
as in the upper permanent molars.

16

The first cervical vertebra with an acute reduction of the thickened
wings and a comparatively wide dorsal arch (width exceeds approximately
two or more times the width of the ventral arch), has a faint impression of
a neural spine (Figure 45). The articulating surfaces with the skull and
the second cervical vertebra are spread up and significantly enter into the
ventral part. The ends of the pair of articulating areas fuse together on it
(Figure 45). The second cervical vertebra is drawn out slightly antero-
posteriorly, with a highly developed neural spine the upper end of which
is bifurcated (Figure 46); the largest antero-posterior diameter of this
appendix is approximately equal to the length of the body of the vertebra
and the greatest width (transversely) exceeds the width of the tooth-like
appendix. The latter, in its lower border of the articulating surfaces,
contacts the first cervical vertebra. The articulating surfaces for the atlas
fuse together directly under the odontoid process of the axis. The trans-
verse processes are almost completely reduced. The rest of the cervical
vertebrae are spread up with thickened, unbent dorsal arches unfused but
closely fitting to each other and firmly fixed (Figure 7). The neural spines
are almost completely reduced and the transverse ones are hardly apparent.
The sacral bone is formed by a complete fusion of four (genus Spalax), or
five (genus Microspalax), vertebrae. The neural spines are completely

та
Ш | é
ut |. =

Figure 7. Cervical section of the vertebral column without atlas.

A, В, C—Spalax; О, Е, F—Microspalax; A, D—from above;
B, E—from below; C, F—from the side.

17

fused to form the dorsal crest (Microspalax) or exhibit a considerable
tendency for fusion (Spalax) (Figure 49). The transverse processes (wings)
of the sacral bone are not fused because the dorsal sacral openings are
almost completely closed. The cranial and caudal articulating processes
of the second to fourth vertebrae are completely reduced. The lateral
boundaries of the wings (transverse processes) in the region of the third
and fourth vertebrae have dorso-lateral crests.

The sternum is diamond-shaped with a well-developed handle that is
narrow at its end and has a well-developed central crest (Figure 8). The
thin clavicle, which is almost unbent throughout the width of its extremity,
articulates with the scapula and is two and one-half times less than the
width of the acromion process.

``
SS
Ce
7

2222
idl

Sv
77727

2
Gy

В А
BH.

~~ <

Figure 8. Sternum. x3.6.

A, B—Spalax; С, D—Rhizomys; А, C—from below; В, D—from the side.

The scapula is relatively narrow with steadily approaching distalcranial
and caudal borders; the distance between cranial and caudal angles (width
of the proximal extremity) is twice narrower than the length of the bone
measured from the farthest point of the beak-like process. The caudal
border is widened because of the greatly developed caudal ridge (Figure
9). The acromion process is comparatively short; its length does not
exceed one-third the length of the scapula; it ends a little short of the
articulating fossa (a little less distance than the latero-medial cross section
of the latter). The beak-like process is short and flat.

The humerus is strongly flattened in the antero-posterior direction;
its width is more than the deltoid process (proc. deltoideus) by two and a
half times and exceeds the antero-posterior cross section measured at the
same place. The large tubercle is higher than the shoulder head. The

2

18

deltoid ridge is strong, placed laterally, and bent sharply due to a backward
protuberance. The medial epicondyl is sunken, its distal end is located
below the similar trochlea (Figure 10). The epicondylar (supratrochlea)
foramen is absent.

The ulna is particularly large in the arm, with a strongly developed

Figure 9. Scapula. x1.6.

A, C—Rhizomys; B, D—Spalax;

A, B—from the side of the
articulating cavity;

C, D—from the side of the caudal edge.

(Об

RSS

Hl
QO

2777727 ABE |
LL gE

АК

Е

`

А
к

ll

AW

Figure 10. Humerus bone, Figure 11. Radius and ulna bones
anterior. Х 1.6. from the outer side. Хх 1.6.
A—Rhizomys ; B—Spalax. A—Rhizomys; B—Spalax.

19

massive elbow process (olecranon) whose length exceeds one-third of its
entire length. The radius is a short bone, its length being one-third less
than the ulna, with a strongly bent axis (bulging anteriorly) (Figure 11).
The metapodia (metacarpals) and the phalanges of the fingers are short
and broad (Figure 12).

Figure 12. Paw. х2.4.

A—Spalax; B—Rhizomys.

The pelvic bone has a well-developed sciatic ridge and bulge (Figure
49), with a reduced pubic bone, and a very small interlocking foramen;
the height of the foramen is usually twice or more, less than the length of
the articulating fossa; rarely, it is equal to the latter, or exceeds it a little.
The pubic symphysis is delicate, sickle-shaped, and bent (Figure 49). The
base of the seat is always protuberant (convex).

The femur is very strong in the antero-posterior axis, considerably
large, and inclined proximally in relation to its head, with a large tro-
chanter, and a strong, considerably bent lateral ridge (Figure 13). The
lesser trochanter and head of the femur are close to each other. The block
(pulley) for the knee cap (whirl bone) is thick.

20

The big tibia is thick, the proximal end is bent forward and within
latero-medially, with a well-developed ridge—crista tibiae (enemial crest)
which is medial. The fibula is completely fused with the tibia for almost
half of its length. Its upper portion is in the shape of a flattened plate
which, in turn, fuses with the epiphysis of the tibia. The borders of the
fusion of the tibia and fibula are not visible in the first and second case
(proximally or distally). The metapodia (meta-
tarsals) and phalanges of the toes of the feet
are characteristically short, as in the structure
of the wrist.

Comparison. Mole rats represent an early
differentiated group of specialized digging
rodents, separating with Rhizomys of the
branch of hamster-like animals from the
general group somewhere in the Eocene
period. Among the representatives of the
present-day fauna of rodents, the nearest
family appears to be that of the bamboo rat—
Rhizomyidae—though the latter were differ-
entiated from mole rats perhaps during
sufficiently different times even in the Oligo-
Figure 13. Femur, posterior cene. The differences between mole rats and

view. X1.5. Myospalacinae are so great, notwithstanding
some of the convergent similar traits in the
structure of the skull and individual bones
of the postcranial skeleton, related primarily to a similar adaptiveness in
the excavation of earth during digging with the help of the head, that
there is hardly any basis for a close relationship between these families.
Their inclusion in one family (as done by Tullberg, 1899) is still less
correct even if only at the level of independent subfamilies (Thomas,
1897), which found support in the works of some scientists in the USSR
(Ogney, 1947; Afanas’ev et al., 1953). Looking at the aforesaid, we are
restricting ourselves to the comparison of mole rats, because at present
there exists some confusion in the determination of their remains in the
works of paleontologists (Bazhanov and Kozhamkulova, 1960).

Mole rats differ from representatives of the family Rhizomyidae as
follows:

1. By eyes which are hidden under the skin, and by an almost eclipsed
external ear and tail, neither of which are seen externally. In Rhizomyidae,
the eyes are not hidden under the skin, the external ear is well-developed,
and the tail length exceeds the length of the hind feet.

2. By long facial but shortened cranial sections of the skull. The length
of the former considerably exceeds the length of the latter. In bamboo

A—Rhizomys; B—Spalax.

21

rats, the facial portion of the skull is relatively short.

3. By a greatly developed, broadened, and considerably forward slant-
ing occipital surface (situated in relation to the longitudinal axis of the
toothrows at an angle of about 45°, while the apex of the lambdoidal crest
is shifted anteriorly to the level of the processes of the winged bones; the
width of the very surface is more than the length of the cranium). In
Rhizomyidae, the occipital surface is moderately developed, is not broad,
and is slightly inclined forward; it is situated almost perpendicularly in
relation to the longitudinal axis of the toothrows; the apex of the lamb-
doid crest, behind the lateral pharyngeal tubercles, and the width of the
very surface, is distinctly less than the length of the cranial portion (Figure
14).

4. By a lowered, wide rostrum, the width of which is considerably
more than the least height. In the bamboo rat, it is narrow and high; its
least height is considerably more than its width.

5. By elongated, narrow, and forward-protruding nasal bones; their
length exceeds twice or more the length of the upper line of the permanent
molars; the greatest width is more than twice the length (usually two and
one-half times), and the anterior edges are drawn forward in relation to
the anterior borders of the premaxillary bones. In Rhizomyidae, the length
of the nasal bones exceeds less than twice the length of М! to МЗ; their
width is approximately twice less than the length, and the anterior extre-
mities are shifted behind in relation to similar ones for the premaxillary
bones.

6. By a large, relatively narrow, infraorbital foramen. Its height in
Spalacidae is not less than the length of the two anterior permanent molars
and always exceeds the width. In bamboo rats, this foramen is compara-
tively small, and wide; its height only slightly exceeds the length of M+
or is even approximately equal to the latter, and the width is more than
the height.

7. By zygomatic arch that is slender, a little bent down, and situated
relatively low in relation to the toothrows. In bamboo rats, the arch is
strong, wide, strongly bent down, and placed higher in relation to the
toothrows.

8. By the disposition of the lambdoid ridge on the level of the posterior
extremity of the zygomatic arch and a comparatively large prolongation
of the latter; the length of this ridge is a little less than the largest jugal
width, less than one and a half times. In bamboo rats, the posterior base
of the zygomatic arch is considerably bent in front in relation to the lamb-
doid ridge and the total prolongation of the latter is more than twice less
than the width of the skull in the jugal region.

9. By the incisorial openings which are considerably shifted posteriorly,
as a result of which the length of the posterior hard palate exceeds much

22

less than twice the length of the former. In bamboo rats, the anterior
palate is approximately twice shorter than the posterior one.

10. By the narrowed, horizontally situated masticating surface of the
skull, with a sharply contoured (in the shape of a crest) anterior region,
not reaching the suture between the premaxillary and maxillary bones;

indies

. ИР Ke

ny
ily

а
Ss

ИГРОЙ

Е
|
р

ое
4 3

ОО

4 А fp

h, AWN Alls

1 ee y Le ) и
“ai |

Figure 14. Rhizomys sp. Natural size.

A—skull from above (dorsal view); B—the same from below (ventral view);
C—the same from the side (lateral view); D—lower jaw from the outer side.

23

the length of the masticating surface is less than the length of the two
anterior permanent molars. In bamboo rats, this surface is relatively
longer (its length is approximately equal to the length of a full line of M!
to М?), and situated in a vertical hollow; its anterior edge, without any
contoured ridge, always encroaches on the premaxillary bone.

11. By a narrow, winged process of the cuniform (wedge-shaped) bone,
the width of which does not exceed half of the anterior width of the nasal
bones. It is wider in the bamboo rat; its width significantly exceeds half
that of the anterior total width of the nasale, and in some cases exceeds
even their full width.

12. By an unclosed winged depression; largely coinciding with the
orbital foramen and the brain cavity. It is completely or almost completely
closed in Rhizomyidae.

13. By a prolonged, true articulating surface whose length exceeds
the length of the upper line of permanent molars, and additionally, the
jugular process of the temporal bone in Spalacidae, as a result of which
the articulating fossa is not present on the zygomatic arch. In bamboo
rats, the true articulating fossa is shortened (length is less than that of the
line of permanent molars), and the jugular process of the temporal bone
is well-developed, as a result of which a considerable portion of the fossa
glenoidea extends on the zygomatic arch.

14. By the construction of a false articulating fossa which is formed in
Spalacidae by the petromastoideum and the dorsal edges of the auditory
bullae forming an articulating plate. In bamboo rats, the lower jaw in the
extreme posterior position rests exclusively in the thick tympano-turbinals
of the auditory bullae, the articulating plates of the latter ones are absent,
and the mastoid bones do not take part in the formation of the false
articulating fossa.

15. By the protruding external edges of the auditory bullae, as a result
of which the external auditory foramens are situated at about the same
level as the occipital condyles and not laterally in relation to the occipital
surface. In bamboo rats, the external edges of the auditory bullae are
raised, the external foramens are situated at the level of the lambdoid
ridge, and their edges are curled externally in relation to the same ones of
the occipital surface.

16. By a large, low placed petromastoideum; the height of the mastoid
bone exceeds the length of the row of permanent molars, and the
lamellar processes are placed external to the jugular processes at about
the same level as the latter. In bamboo rats, the mastoid bones are short
(their height is considerably less than the length of М! to М3), and raised
(lamellar processes are situated directly under the large, wide proc. par-
occipitalis).

17. By the lower occipital opening, the height of which is less than

24

twice ог more times the height of the occipital surface measured from the
upper edge of the foramen magnum. In bamboo rats, this opening is
comparatively higher; its height is more, though less than twice the height
of the occipital surface.

18. By occipital condyles which contact each other. These do not make
contact in Rhizomyidae.

19. By a strongly slanted posteriorly articulating process of the lower
jaw, the longitudinal axis of which approximately corresponds to the
similar one of the horizontal branch. In bamboo rats, it is placed at a
considerable angle or almost perpendicular in relation to the longitudinal
axis of the horizontal branch.

20. By the almost perpendicular position of the anterior edge of the
coronary process. In Rhizomyidae, it is considerably inclined back.

21. By a wide furrow on the coronary articulating surface; its width
exceeds the length of the lower line of the permanent molars, or is about
equal to it. It is narrow in bamboo rats. Its width is less than the length
of М, to Ms.

22. By a more pronounced tubercular structure of the upper and lower
permanent molars.

23. By the structure of the first cervical vertebra. The atlas has greatly
reduced wings in Spalacidae, is thick with a comparatively wider dorsal
arch (width exceeds twice or more the width of the ventral arch), and
very faint traces of a bony process show. Additionally, the corresponding
pair of surfaces for the condyles of the skull and the articulation with the
second cervical vertebra largely cross the ventral arch, and are in contact
with each other. In bamboo rats, the wings of the atlas are well-developed,
the dorsal arch is bulging and narrow (its width is approximately equal
to the ventral arch) with well-developed traces of a bony process. The
right and left surfaces for articulation with the skull, and the second
‘cervical vertebra, are almost not set in the ventral arch and are not in
contact with each other.

24. By the structure of the second cervical vertebra. The bony process
(neural spine) of this vertebra in mole rats is a little elongated in the
antero-posterior direction, widely spread up, and bifurcated at the end.
The greatest antero-posterior transverse section of this process is approx-
imately equal to the body of the vertebra but the greatest width exceeds
the width of the odentoid process. The latter is characterized by a thick
dorsal surface and is situated above the lower edge of the articulating
surface for articulation with the first cervical vertebra; the surfaces them-
selves fuse together directly under the odentoid process; the transverse
processes are almost completely reduced. In bamboo rats, the bony process
of the second cervical vertebra is strongly elongated in the antero-posterior
direction (the largest antero-posterior transverse section exceeds the length

25

of the body of the vertebra), flattened transversely with an unbifurcated
upper end; its width is less than the width of the dens epistrophei (odentoid
process). There are round contours in the transverse section shifted ven-
trally in relation to the lower edge of the surfaces, not contacting each
other for articulation with the atlas; the transverse processes are well-
developed.

25. By wide, thick, dorsal arches of rest of the cervical vertebrae. The
centra of these vertebrae and their dorsal arches fit closely forming an
immovable part. The bony processes (neural spines) are almost reduced;
the longitudinal ones are hardly marked: In bamboo rats, the dorsal arches
of the cervical vertebrae are thin, bulge very much and are not fitted
closely to each other (the cervical vertebrae are mobile), and the bony
and transverse processes are well-developed.

26. By the bony process (neural spines) of the vertebrae of the sacral
bone being fused or having a tendency to fuse to form the dorsal ridge; by
its unfused wings having almost complete sacral openings, and a complete
reduction of cranial and caudal processes of the second to the fourth
vertebrae. In addition, the lateral edges of the wings of the sacral bone in
the region of the third and fourth vertebrae have latero-dorsal ridges. In
bamboo rats, the bony processes (neural spines) of the vertebrae of the
sacral bone are not fused to form a dorsal ridge; the wings are more
separated; since the sacral openings are oblique, the cranial and caudal
processes of the second to the fourth vertebrae are well-developed, but
the latero-dorsal ridges are absent.

27. By the diamond-shaped (rhomboid) contour of the sternum with a
pointed handle at the end and a well-developed central crest (keel). In
bamboo rats, the sternum is flask-shaped, its handle rounded, and the
central ridge is absent.

28. By a thin, almost straight, clavicle, the width of which is one and a
half times less than the width of the acromion process in the region of
articulation with the scapula. In bamboo rats, this bone is relatively wider
and bent when compared with the same in mole rats; its width is approx-
imately equal to the width of the acromion process at the place of arti-
culation with the scapula.

29. By a relatively narrow scapula, elongated longitudinally, with
subsequently approaching cranial and caudal edges that are wide because
of the well-developed caudal ridge at the caudal edge; by a comparatively
short acromion process ending at a small distance from the articulating
depression (less than the latero-medial transverse section of the latter);
and by a short, widened, beak-like process. The distance between the
cranial and caudal angle of the shoulder blade is more than twice shorter
than its length, and the length of the acromion process does not exceed
one-third the length of the latter. In Rhizomyidae this bone is short and

26

wedge-shaped because its cranial and caudal edges sharply approach in
the direction of the articulating fossa, without the caudal ridge, with a
relatively long acromion process (more than one-third the length of the
scapula), terminating long before the articulating fossa (which exceeds
the latero-medial cross section of the latter), by a long and narrow beak-
like process; the distance between the cranial and caudal angles of the
scapula significantly exceeds half the length of the latter.

30. By the humerus with a greatly compressed diaphysis in an antero-
posterior direction (its width above the deltoid process exceeds one and a
half times or more than its antero-posterior diameter); by a protuberance
under the head of the humerus; by a strong laterally placed and acutely
bent deltoid process with a distally lowered epicondyle, the lower end of
which is placed under the trochlea. In Rhizomyidae, the diaphysis of the
humerus is compressed very little in an antero-posterior direction (its width
exceeds less than one and a half times the antero-posterior diameter); the
proximal section of the large protuberance is placed under the head of the
humerus; the deltoid process is weakly developed, directed anteriorly, and
unbent; and the distal end of the epicondylus medialis is situated above
a similar trochlea.

31. By a long, massive olecranon process of the ulna which consider-
ably exceeds one-third the length of the ulna. In bamboo rats, the height
of the olecranon process easily exceeds one-fourth the length of the ulna,
or is approximately equal to a similar one.

32. By a shortened, strongly anteriorly bent radius; its length is shorter
than the length of the ulna by more than one-third. In Rhizomyidae, the
radius is elongated (shorter than the ulna by less than one-third) and is
almost straight.

33. By the structure of the pelvic bone in which the ischial tubercle
is well-developed; by a reduced pubic bone and a very small acetabulum
(its height is usually twice or more, less than the articulating fossa, rarely
equal to it, or a little exceeds the latter), by long, slender, sabre-shaped
symphoidal branches of the pubic bone, and a bulging base of the seat.
In bamboo rats, the ischial tubercle is vestigial, the pubic bone is well-
developed, the blocked up foramen is large (its height considerably exceeds
the length of the acetabulum), the symphoidal branches of the pubic bone
are short and wide, but the base of the seat is thick.

34. By the structure of the femur bone with an antero-posteriorly
strongly compressed diaphysis; by a large trochanter placed proximally
to the head of the femur; by a strong and considerably externally curved
lateral ridge; by a considerably closer femur head, and a lesser trochanter;
by a compressed block (pulley) for the knee cap. In bamboo rats, the
femur bone is less compressed in the antero-posterior direction, the proxi-
mal edge of the large trochanter is situated at the same level as the head

27

of the femur, with a comparatively weak lateral ridge, widely separated
lesser trochanter, and caput humeri, and a strongly concave block (pulley)
for the patella.

35. By the proximal portion of the large tibia, bent in a latero-medial
direction and by the presence of a well-developed ridge—the large and
medial-tibial ridge (cnemial crest). In bamboo rats, the diaphysis of the
tibia is widened in its upper half and the ridges are hardly marked.

36. By the structure of the fibula. In Spalacidae, it is completely fused
with the tibia almost up to half of its length; its upper portion is in the
form of a wide plate, completely articulating with the tibial epiphysis;
the line of the joining of both bones is not visible. In bamboo rats, the
fibula is fused with the tibia for less than half of the length of the former,
does not form a lamellar widening, and the sutures of the articulation are
always well-defined.

37. By the shortened and widened metapodia and phalanges of the
digits of the paw and foot. These are slender and long in Rhizomyidae.

Family composition. Two subfamilies are included: the ancient mole
rats, Prospalacinae subfam. nov., and the present-day mole rats, Spalacinae
Gray.

GENERAL NATURE OF THE MAJOR
ADAPTATIONS OF MOLE RATS

Mole rats are highly specialized(shrews whose life activities are related
almost entirely to a subterranean way of life. Differing from other burrow-
ing animals which obtain their food on the surface, and for whom under-
ground tunnels act only as hideouts and storehouses for food, Spalacidae
feed mainly on underground parts of vegetation, obtaining them in the
process of constructing a feeding hole and rarely coming out on the surface.
A constant life in underground conditions of absolute darkness, an atmos-
phere lacking in oxygen and saturated with carbon dioxide, specific condi-
tions for obtaining food with limited possibilities for movement because
each movement is accompanied by considerable effort, followed by con-
siderable excavating activity—these have considerably influenced the
external appearance of the animal, the structure of its cover (fur), its sense
organs, respiratory and cardiovascular systems, and have led to a con-
siderable modification of the skeleton and muscular system of the head
and the rest of the body. While studying this, the typical mode of excava-
tion by mole rats has to be taken into consideration; they loosen the soil
with their strong and wide incisors, and transport and throw away the
soil on the surface mainly with the help of the head. Along with this, if
the geological age of the group which has differentiated itself from the
general branch of Rhizomyidae, perhaps in the beginning of the Oligocene

08

period, is taken into consideration, all the adaptations of its representatives
to subterranean living, brought about through so long a period in the
process of stabilizing the selection, are understood. We will consider
below a few important aspects.

ADAPTIVE CHARACTERISTICS OF THE EXTERNAL
FEATURES, HAIR AND SENSE ORGANS

External features. The external features of mole rats are an outstanding
example of the coordination between the form of an animal and its living
conditions. The representatives of this family have a characteristically
cylindrical body because the wide head continues into the body without
a distinct neck. This peculiarity of the external character is reflected in
the structure of the skeleton and can be seen in the shortened and immoy-
ably articulated cervical part of the vertebral column with the sternal
section, details of which will be given below (Figure 49). The constant life
in comparatively narrow and low underground tunnels, accompanied by
intensive excavating activity, is the main reason for an almost complete
reduction of the external ears, preserved in representatives of mole rats
only in the shape of a small skin flap, completely hidden by hair. The
limited activity of the animal leads, similarly, to a considerable shortening
of the tail (a process accompanied by a considerable reduction in the
number of caudal vertebrae), because under these conditions it absolutely
loses its function as an organ of equilibrium. The general tendency in
representatives of mole rats to the aspects mentioned above, as compared
with other burrowing animals, and a tendency toward a reduction in the
length of the anterior and posterior limbs, well adapted for movement
inside horizontal, slanting, and even vertical holes, and for lifting and
fixing loads more than the weight of the animal, can be understood. The
throwing out of the soil from the burrow with the help of the head leads
to its becoming considerably broad and strong, giving it a shovel-shaped
contour.

Hair. The structure and color of the hair of mammals is undoubtedly
very important from the viewpoint of general adaptations which can be
seen from the differences existing in various taxonomical, ecological and
geographical groups of animals in the evolutionary process, expressed in
various forms in ontogeny. The hair is not an exception from this point
of view. It is characterized by the absence of differences in guard hair and
undergrowth, differs in fineness (texture), and easily changes direction at
the slightest touch. The adaptive character of such hair structure in these
specialized shrews can be fully understood by realizing that restriction
in movement of the animal in different directions underground is reduced
to a minimum. Hard and long hair, specifically directed in one direction,

29

would have been a considerable obstacle for movements of this animal in
a direction opposite to its hair; moreover, under the comparatively con-
stant humidity of the burrows and feeding holes, the role of the hair is
restricted to thermal regulation, and its defensive function against direct
effects of humidity is lost. Recently it was proved that the predominant
color of rodents is for camouflaging. This is very true for mole rats also
in which the predominant color is gray, yellowish, grayish-brown (fallow),
yellowish-brown, brown, and other colors, i.e., colors which almost com-
pletely tally with the substrata on which these animals live. The signifi-
cance of the camouflaging coloration of mole rats, inexplicable at first on
looking at their way of life, becomes clear if it is noted that these animals
have to leave their burrows at times. Considering the limited activity of
these animals on the surface, a complete absence of eyesight, and a not
very acute sense of hearing, it takes little imagination to realize what easy
prey to different predators they would be, without their camouflaging
coloration. Olfactory and communicating receptors adapted mainly to
underground food finding, though well-developed, naturally cannot replace
the effectiveness of other analyzing agents, nor guarantee the safety of
the animals on the surface. As in all specialized earth-digging animals
(shrews), and in the majority of burrowing animals, the color of mole rats
has completely lost its property to change sharply according to the seasons
of the year.

Sense organs. As mentioned above, mole rats have well-developed
olfactory and communicating receptors. Sight is completely diminished,
and the hearing capacity is considerably lower than in representatives of
the majority of other families of Myoidea. These peculiarities of sensory
perception come from the way of life these animals lead.

Vibrissae of different types, in addition to a sensitive epithelium on
lips and nose, function as organs of perception in mole rats. Perhaps the
lowering of the distal points of the front and hind limbs also plays a
considerable role in perceiving the surrounding situation.

There are two types of vibrissae in Spalacidae. Orientation when in
the burrow and food holes is most probably achieved with the help of
long bristles distributed diffusely over most of the head. The lateral part
is studded with them, although individual bristles can be observed from
above and below (Figure 15). A similar function is possibly carried out
by the short hairs on the paws and feet (Figure 16). The perception of
objects during burrowing when the head is in the soil is probably achieved
by, in addition to the sensitive epithelium on the nose, the anterior parts
of the lips with the help of the sensitive skin funiculus (cord) extending
from the nose at the side of the head to about two-thirds its length, which
is densely covered with short bristles (Figure 15). Such structures are
absent in other burrowing animals, and this serves as one more example

30

of the narrow specialization of organs of perception toward specific
conditions of underground food collection accompanied by burrowing
activity. They are absent even in highly specialized burrowing animals
such as Rhizomyidae zukor (myospalax spp.) and the mole vole (Ellobius
spp.) among field voles. Most probably these adaptations are inherent
in representatives of the given family of rodents. The innervation of

Figure 15. Head of Microspalax nehringi (Sat.)
from the side, x 1.6,

Figure 16. A—Hand, and B—Foot of Microspalax nehringi (Sat.). 3.6.

Si

whiskers of all types occurs through the superior labialis nerve, originat-
ing from the big infraorbitalis nerve (branches of the maxillaries). In
ancient mole rats, there is a special closed canal through which this nerve
passes.

The olfactory sense is well-developed in mole rats. This is quite evident
from the structure of the nasal cavity; it is constructed for an acute sense
of smell (classification of nasal cavity proposed by Sakharova, 1953);
the nasal cavity is relatively short, the turbinals (nasoturbinal, maxillo-
turbinal and ethmoturbinal) are dense, and close to one another; the
olfactory drums are situated in the posterior part of the cavity and are
highly developed (Figure 17). This structure of the nasal cavity is inherent
in rodents which lead a burrowing and underground life, and is the most
“proper” adaptation of the olfactory organs to such living conditions.
The presence of an acute olfactory sense in mole rats is proven by the
highly developed olfactory lobes in the main brain in these animals which
can be clearly seen in a section of the skull (Figure 17). Further, the ductus

EF “7 ss wa
ZW Rae

at; mt SS
AS RX ох

y SS
>

А SSN |

"---.--

Figure 17. Longitudinal section of skull of
Spalax arenarius Resh. х1.75.

dn—ductus nasopharyngeum; ef—ethmoturbinalia;
nt, mt—naso- and maxillo-turbinalia; /—cerebellum.

nasopharyngeum is relatively broad and straight, and its structure re-
sembles that of rodents who have a “respiratory” type of nasal cavity.
However, this peculiar construction of the nasal cavity in moles has its
own functional explanation. The nasal cavity indicates, perhaps, a greater
adaptation of the respiratory organs of the mole rat toward an increased
CO, content in the burrows, in comparison with simple burrowing animals.
This is expressed, perhaps, in terms of a lowered respiratory rhythm which,
according to Tumanov, is a peculiarity of the venous circulation because
Spalacidae do not have the venous sinuses characteristically present in
other burrowing animals of the group Myoidea.

32

An underground way of life caused the lessening of sight in mole rats,
and because of this the optic receptors underwent significant adaptive
changes. Among the rodents of the old world the living representatives of
this family represent the only group whose eyeballs are completely hidden
under a skin cover. Such a construction has mainly a defensive function.
With this, the optical receptors themselves have changed comparatively
little. The presence of well-developed eyeballs and well-developed optic
nerves in living mole rats, and similarly the corresponding structures in
the skull—large eye sockets, lacrimal fossa, and orbital apertures (Figure 3)
—prove this. All this apparently points to a comparatively recent (in terms
of geologic age) loss of sight in Spalacidae, if ultimately through special
histological studies of the eye, its function of subcutaneous vision (at least
differentiation of light and darkness) is not proven. Such a phenomenon
of differentiation exists in some vertebrates adapted to conditions of
absolute darkness in caves and sea depths.

Hearing is not as well-developed in mole rats as in mice and hamsters;
this can be seen by the presence of comparatively smaller auditory bullae
(length does not exceed one-fourth the condylobasal length of the skull)
with a very small opening to the external ear. Furthermore, as seen above,
the auditory bullae of Spalacidae participate in the formation of false
articulating fossae.

MORPHO-FUNCTIONAL CHARACTERISTICS OF THE DENTITION
OF MOLE RATS WITH REFERENCE TO ADAPTATION TOWARD
BURROWING AND FEEDING

Of all the skull structures of mammals, the teeth are the most important
from a taxonomical point of view. In the majority of cases the character-
istics of structure could be the most important taxonomical traits, allowing
not only a separation of different species and greater taxonomical cate-
gories, but even explaining their genetic relationships, evolutionary pecu-
liarities, and the nature of specialization in individual groups of mammals.
It has to be noted that the jaw apparatus, principally the teeth, is preserved
better than other parts in fossil conditions, and is almost the only source
for objective judgement about the phylogenetic relations of fossil and
present-day forms.

In view of the foregoing facts, we consider it proper to describe in
great detail the adaptive aspects of the dentition of mole rats; moreover,
the taxonomy of the whole family is based on the peculiarities of this
structure.

In the majority of Myoidea with a burrowing or underground mode
of life, the teeth, in addition to their useful trophic functions associated
with nibbling and grinding food, take upon themselves other functions

85

originating from adaptation to digging with incisors. The adaptability of
the teeth for digging becomes important in mole rats; the incisors serve
as basic burrowing structures. The aforementioned peculiarities are them-
selves the leading trends in which a basic change of the bone and muscles
associated with the jaw movement of Spalacidae took place in the process
of adaptive evolution which is primarily directed toward the greatest
“economic’’ comfort, and the restriction of masticating and digging move-
ments. Some defensive adaptations also took place to protect the teeth
from too much wear during direct ground breaking while, similarly, in-
creasing the effective strength of friction on permanent molars, concerned
with earth falling into the mouth cavity and false movements of the lower
jaw which always accompany digging. However, the significance of trophic
and digging specialization in the evolutionary process of mole rats is
absolutely not the same. If it is assumed that the peculiarities of the masti-
catory movements in Spalacidae do not differ principally from similar ones
in Myoidea, the entire typical structure of their masticatory apparatus, as
a result of natural selection acting in the direction of an increased digging
adaptability, would have to be accepted.

The functional adaptations of the masticatory apparatus of mole rats
have been poorly investigated in literature. At present, we actually bank
upon seven sources in which the authors refer to aspects of our subject
in one way or another. Yet, the anatomical characteristics of the bone-
muscle structure forming the masticatory complex of Spalacidae have
been studied in detail. Very superficial information on the general plan
of the structure of teeth, corresponding sections of the skull, of the lower
jaw, and also of the masticatory muscles, can be found in Tullberg’s
review (1899). A sufficiently complete description of the dental system of
mole rats and the structural characteristics of the masticatory parts of
the skull and lower jaw is found in Mehely’s monograph (1909). Mehely
has also studied in detail the anatomy of the muscles attached to the
masticatory complex. However, neither of the authors mentioned has
given the peculiarities of the structures in the masticatory apparatus of
mole rats an adequate functional explanation. B. S. Vinogradov (1926)
has given a short analysis of the adaptive features of the construction of
the bony structure of the masticatory part of the skull and lower jaw of
mole rats as compared to specialized shrews and burrowing animals from
other families. Further, the facts mentioned in this work were elaborated
in a joint paper by B. S. Vinogradov and P. P. Gambaryan (1952) and,
finally, were further developed in a comparatively recent monograph by
P. P. Gambaryan (1960). In this work, P. P. Gambaryan studied the
adaptation of the bony structures of the masticatory apparatus along
with the masticatory muscles. An unsuccessful attempt to give a functional
explanation to the nature of movements and the static position of the

3

34

lower jaw in Spalacidae during the grinding of food and digging was done
comparatively recently by N. N. Vorontsov (1963) who assumed that the
lower jaw in Spalacidae is placed at the extreme posterior position during
digging.

The masticatory apparatus of Spalacidae consists of the following
structures: toothrows including the diastemata, the lower jaw and its
articulating surfaces in the skull, the complex of masticatory muscles and
special structural formations on the skull and lower jaw, the places of
attachment of the masticatory muscles, and finally, the defensive devices
protecting the lines of the permanent molars from too much wear and also
devices for constant restoration or growth of the incisors.

In the complex adaptation of the masticatory apparatus of mole rats
to digging, the differential movements of the lower jaw—concerned with
chewing and grinding foodstuff on the one hand, and digging on the other
—attain a special importance. Digging is achieved by the peculiar arti-
culation of the lower jaw with the skull and, similarly, by the arrangement
of the articulating process, particularly its condyle.

The investigations of B. S. Vinogradov (1926) on the skull of mole rats
showed that in addition to the usual fossa glenoidea, there is one addi-
tional articulating fossa—fossa pseudoglenoidea or fossa posterior—which
is situated behind the actual articulating surface (Figure 4). The false
articulating fossa corresponds to the extreme posterior position of the
lower jaw, when it is not working or during the grinding (crushing) move-
ments, or during completely, or almost completely, closed upper and lower
rows of permanent molars when the gap between the upper and lower
rows of teeth (4/) is less than M,, or approximately equal to it, and
in this position the tips of the posteriorly pushed lower incisors are
situated behind the tips of the upper incisors (Figure 18A and B). During
this, the condyle of the articulating process of the lower jaw is almost
completely situated in the fossa pseudoglenoidea, only slightly touching
by its anterior end the posterior edge of the fossa glenoidea (standstill
position), or during lengthwise masticatory movements it periodically
shifts to the posterior fourth of the latter. In both cases, the tips of the
upper and lower incisors do not touch and do not hinder the masticatory
movement. The apparent form of the false articulating fossa completely
corresponds to the form of the masticatory movements of the lower jaw,
encompassing the shift of the condyle of the articulating process of the
latter, mainly in the horizontal plane, with a little more predominance of
the lengthwise movement than of the transverse one. Thus, the main load
during the masticatory process in mole rats falls on the false articulating
surface and only partially on the posterior portion of the fossa glenoidea.
In fact, the latter determined the adaptive characteristics of the construc-
tion of the fossa pseudoglenoidea which, as has been shown above

35

(page 12), is bound up laterally and from behind by a comparatively
thin petromastoideum, and medially by a special thick-walled articulating
plate of the auditory bulla. This plate, together with the posterior edge of
the true articulating surface, serves as the main support of the lever of the
lower jaw during masticatory movements. The above-mentioned specifi-
cation of the masticatory movements and the related construction of the
false articulating fossa are characteristic peculiarities of Spalacidae, sepa-
rating this group from the majority of Myoidea which lead an underground

Figure 18. Position of the lower jaw. 4/5 of natural dimensions.

A to C—Spalax; D to F—Rhizomys; A, D—during rest and yawning;
В, E—during crushing; С, F—during digging.

36

ог burrowing way of life and dig with the help of incisors. The false arti-
culating surface, though developed to a very small extent, is also found in
the phylogenetically close Rhizomyidae and in convergently identical mole
voles. However in the former, it is formed by a concave surface of the tube
of the auditory bulla, thus differing from Spalacidae, and in the latter, it
is represented by a small fossa on the temporal bone placed behind the
fossa glenoidea. In both cases, the petromastoideum does not take part
in its formation and the articulating plate of the auditory bulla is not
present. Furthermore, the condyles of the lower jaw in Rhizomyidae
extend into the fossa glenoidea in an extreme posterior position, in a
manner which is more pronounced than in mole rats.

The grinding of foodstuff, the chewing of roots, stems, and big leaves
of vegetation, is carried out when the incisors of the lower jaw are in the
medium position and the grinding surfaces of the lower and upper rows
of permanent molars are considerably separated in the lengthwise direction
[41 > 1M,, but less than 1 (M,—M.)], and when the cutting surfaces of
the upper and lower incisors are almost touching; the tips of the upper
incisors are all the same, protruding a little in front in relation to the tips
of the lower incisors (Figure 18B). In such a position of the lower jaw, the
grinding movements are predominant in the sagittal level along the smailer
arches, and also, some lengthwise movements take place in the horizontal
plane. There is practically no longitudinal (up and down) grinding move-
ments. This position of the lower jaw in mole rats was taken as anterior-
most by B. S. Vinogradov (1926) and P. P. Gambaryan (1960). Because of
this, the authors mixed the movements of the grinding and digging cycles,
differentiating the digging movements only by the size of the arch in which
they are carried out (small arches during grinding; larger ones during
digging; Gambaryan, 1960). However, in this position the functional
importance of the anterior half of the fossa glenoidea is not understandable
because the condyle of the lower jaw, irrespective of the dimension of the
arches on which the movements take place, is not shifted to this part of
the natural articulating surface during such movement. So, an assumption
comes up, naturally, that mole rats differ from Rhizomyidae in that the
grinding and digging movements are carried out by the jaw approximately
in one and the same position, and differ from each other only by the size
of the arches; in addition to the two positions described above, there is a
third for the lower jaw—the anteriormost—or the digging position. In
this position, the condyle of the lower jaw shifts to the anterior half
of the fossa glenoidea, the grinding surfaces of the upper and lower
teeth are not in contact because 4/ > 1(M,—Ms5), and the cutting
edges of the lower incisors move considerably forward in relation to
the cutting edges of the incisors of the upper jaw. In this position, the
lower jaw carries out chewing movements of great magnitude (through

37

greater arches), accompanied by considerable displacement in a lengthwise
direction. This type of movement in the mandibular joint is confirmed by
the whole structure of the articulating surface which, in Spalacidae, has
an appearance of a long groove (its length exceeds the length of the row
of permanent molars, or is approximately equal to it) with well-developed
fixtures restricting the lateral displacements, and also by the formation of
the condyle and the whole articulating process of the lower jaw. The
condyle of the articulating process is narrow, strongly elongated in a
lengthwise direction (the width is less than half the length along the cord,
and approximately equal to it or a little exceeds it), with an arched, bent
up articulating surface, but the process itself is relatively long and strongly
inclined posteriorly (situated almost parallel to the lengthwise axis of the
surfaces of the permanent molars). Such a structure of the proc. condy-
loideus allows great movement of the jaw in the sagittal plane and also
its lengthwise displacement while considerably restricting the grinding
movements in a transverse direction.

All the aforesaid is also confirmed by a functional analysis of the
masticatory musculature of Spalacidae. However, before starting an
analysis of the latter, it would be proper to give at least a short account
of its construction because this has not been done by us in the preceding
portion of this work.

The masticatory musculature is very schematically described and drawn
in the major work of Tullberg (1899); more detailed descriptions are given
by Mehely (1909) and Gambaryan (1960). The complex of the masticatory
musculature includes the most complicated muscle M. masseter, the tem-
poral muscle M. temporalis, the wing-like muscle M. pterygoideus, and
the bilateral muscle M. digastricus.

The M. masseter is divided into two layers in Spalacidae, the external
(M. masseter lateralis) and the internal (M. masseter medialis). The
external layer consists of two portions, viz., the superficial one (M. m.
lateralis superficialis) and a deeper one (M. m. lateralis profundus). Finally
the superficial portion is represented by two parts, viz., the anterior (M. m.
1. superficialis anterior) and the posterior (М. m. 1. superficialis posterior).
The former is attached to the anterior ridge of the masseter surface of the
skull, and on the lower jaw it attaches itself on the external edge of the
angular process all along its anterior half (Figure 19; mlsa). The second
portion is attached laterally at one end along the entire zygomatic arch
(starting from the jugal angle), and along the posterior half of the external
edge of the angular process of the lower jaw (Figure 19; mlsp). The fibers
of the superficial portion of the external layer of the masseter muscle are
directed in some instances at an angle of less than 45° in relation to the
longitudinal axis of the grinding surfaces of the permanent molars.

The deep portion of the external layer of the M. masseter is attached

38

to the surface of the whole masseter area and along the whole edge of the
zygomatic arch medially at the place of attachment of the superficial
portion, and to the lower jaw along the edge of the angular process,
including the sella externa above the place of attachment of the М. m. |.
superficialis and along the whole masseter surface of the lower jaw (Figure
19; mlp). Its fibers are directed a little ahead during the posterior position
of the lower jaw with relation to the longitudinal axis of the grinding
surfaces of the toothrows, but at a greater angle than the similar ones for
М. т. |. superficialis.

и
|

|

Figure 19. Structure of (т) masseter, (1) temporal and (4) digastricus
muscles in the mole rat Microspalax ehrenbergi (Nehr.) (by Mehely, 1909).

See text for legend.

39

The inner layer of the masseter muscle (М. m. medialis) divides into
two portions, the anterior (M. m. medialis anterior) and the posterior
(M. m. medialis posterior). The first is attached to the skull on the upper
and partially anterior edges of the suborbital foramen, passes through it,
and becomes attached to the body of the lower jaw under the anterior
permanent molars a little higher than the ridge on the masseter surface,
anterior to the incoming branch (Figure 19; mma); the second originates
from the medial edge of the central and posterior portions of the zygomatic
arch and terminates partly on а special muscular depression on the external
wall of the anterior portion of the incoming branch, and partly on the
ridge on the corono-alveolar furrow (Figure 19; mmp). The fibers of the
anterior portion are directed a little forward during the posterior position
of the lower jaw, though at a greater angle than the similar deeper portions
of the M. m. lateralis profundus, and the fibers of the posterior portion
are arranged almost vertically.

The M. temporalis in mole rats is divided into three parts—parietal
(pars parietalis), lambdoidal (pars lambdoidea) and temporal (pars supra-
zygomaticus). The parietal and lambdoidal parts are the most developed.

The parietal portion of the temporal muscle is attached to the skull
all along the sagittal ridge including its bifurcated suborbital portion, and
on the lower jaw it becomes attached above the anterior ridge of the
masseter area directly under the permanent molars, including the space
between the alveolar edge of the jaw, and by a special branch medially in
relation to the areas of attachment of the anterior portion of the inner
layer of the masseter muscle (Figure 19: tp).

The lambdoidal portion begins its attachment on the lambdoid ridge
on the skull and ends on the coronate process of the lower jaw (Figure
9).

Finally, the temporal portion of the М. temporalis begins its attach-
ment on the lateral edge of the petromastoideum (above the external
auditory meatus) and its direct prolongation, formed by the temporal bone,
ends also on the coronate process of the lower jaw (Figure 19; tz).

The M. pterygoideus divides into two portions, the outer (M. p.
lateralis) and the inner (M. p. medialis). Both portions originate on the
skull from the fossa pterygoidea; moreover, the outer bifurcates into two
strands which are attached to the lower jaw on the medial side of the
articulating surface directly under the condyles (Figure 20; pl), and the
inner one, on the medial side of the angular process below the sella externa
(Figure 20; pm).

The M. digastricus is sufficiently well-developed in mole rats. It starts
from the articulating ridge at the angle of the lower jaw and ends on the
skull attaching to the proc. paroccipitalis (Figure 19; d).

Furthermore, the M. transversus mandibulae is well-developed in

40

Spalacidae, playing the role of an additional fixator (in addition to the
immovable symphoidal junction) of the branches of the lower jaw. This
muscle attaches itself all along between the angles of the jaw and the origin
of the angular process on each of the horizontal branches of the lower jaw
(Figure 20; mtm).

Figure 20. Structure of (р) pterygoideus and (пит) longitudinal muscles
of the mole rat Microspalax ehrenbergi (Nehr.) (by Mehely, 1909).

See text for legend.

Before beginning the functional analysis of the muscles of the masti-
catory complex of Spalacidae, the variability in the load taken by indivi-
dual systems has to be pointed out first. This can be seen from а compari-
son of the relative weights of the individual muscles forming this complex.
Thus, from data by P. P. Gambaryan (1960), the per cent relation of the
weights of individual muscles to the general weight of the skeleton in M.
nehringi (Satunin) is 9.85 for the masseter, 11.02 for the temporal, 1.55 for
the pterygoideus, and finally, 1.01 for the digastricus muscle. Thus, it
becomes clear from the given data that in Spalacidae, the masseter and
temporal muscles attain the greatest development of all the muscles of the
masticatory complex and so most of the load during burrowing is borne
by them. The considerable development of the muscles of these groups is
completely in order for the rodents which have specialized either fully or
partly in burrowing with the help of teeth (Gambaryan, 1960). Hence,
the great importance of the weights of these muscles in comparison with
the majority of burrowing animals from the group Myoidea does not need
further clarification. To some extent, as regards the degree of development
of the masseter muscle, mole rats are analogous only to those specialized
rodents that have a burrowing tendency of the same type such as mole
voles (9.97), long-clawed field voles (Promethea schapoechriteovi Satunin)
(9.12), and rats of the genus Nesokia (9.85) (in the rest of the Myoidea,
the value of this index varies from four to eight); and in respect of the

41

development of the temporal muscle, mole rats have had almost no
parallel among representatives of the group (in mole voles and long-clawed
field voles, the value of this index generally does not exceed five to seven;
in other burrowing animals of the suborder Myoidea, it is considerably
less). At the same time the weight of the muscles pterygoideus and digas-
tricus does not differ significantly from the same muscles in the majority
of other Myoidea. Considering the peculiarities of attachments for these
muscles on the skull and lower jaw, it can be confidently said that they
have the same function in Spalacidae as in other Myoidea, and they bear
similar, comparatively smaller loads. The first muscle allows small horizon-
tal movements of the lower jaw during yawning, and the second one
allows its lowering down during pressing and biting movements.

As has been mentioned already, the development of the masseter and
temporal muscles in Spalacidae is mainly concerned with the type of
burrowing. Their structure and function can be understood only from this
point of view. The morphological peculiarities of the masseter and tem-
poral muscles have been discussed above in detail, and hence we will now
consider only the functional analysis of these systems during different
positions of the lower jaw at the time of mastication.

The structure and peculiarities of the attachments of the majority of
the parts of the masseter muscle are such that they allow maximum move-
ments of the lower jaw along with other important movements of different
Myoidea. This can be seen by the slightly anteriorly placed basic parts of
the masseter in the extreme posterior position of the lower jaw which is
the case during the standstill position and masticating movements. Only
the posterior portion of M. masseter medialis is an exception, fibers of
which are directed vertically in that position of the lower jaw or directed
even a little backward. It looks from this that its role is perhaps restricted
by the movements carried out during the simultaneous contraction of the
right and left muscle—the small transverse movements of the masticatory
cycle. As regards all the remaining parts of the M. masseter, during chew-
ing movements of the lower jaw, apart from the functions characteristic
to the M. M. medialis posterior, it allows a little lengthwise movement of
the latter and, moreover, the Д/ in this case is less than the length of the
lower front permanent molar, or is approximately equal to it. These move-
ments of the lower jaw point to the comparatively lesser loads on the
masseter muscle.

During the average position of the lower jaw, corresponding to the
grinding of foodstuff, biting of roots, stems, and large leaves, the fibers of
the anterior portion of the M. masseter medialis and also of the deeper
portion of the external layer of the masseter muscle, take up a vertical or
almost vertical position, as a result of which their function is almost
exclusively restricted to the movements of the lower jaw. The further

42

forward movements of the jaw are mainly carried out Бу the superficial
layer of the M. masseter lateralis which, as yet, has maintained its position
in relation to the longitudinal axis of the grinding surface of the permanent
molars though the angle of its fiber direction is still acute. The posterior
portion of the M. m. medialis is directed a little behind and perhaps plays
a specific role during the movements of the jaw backward to the original
position. If it is considered that the grinding movements in the above-
described position of the lower jaw are carried out mainly along the small
and medial arches, it becomes clear that the masseter muscle does not
carry the maximum loads in the process of grinding food.

Finally, during the assumption of the extreme anterior position of the
lower jaw, corresponding to burrowing action, all the component parts of
the masseter muscle take up a vertical (or close to it) position, thus con-
siderably enhancing the effort of the biting movements of the burrowing
cycle directed mainly in the sagittal plane and taking place along the
bigger arches. However, it has to be noted that the anterior position of the
superficial layer of the external layer of the masseter muscle preserves the
original tapering (bias). Hence the equivalent force which this part imparts
to the lower jaw will never correspond to the reduced force. Besides, in
the similar position of the lower jaw, the fibers of the deep portion of the
M. m. lateralis and the anterior portion of the inner layer appear to be
tapered; but in the backward direction, they perhaps play a specific role
in its longitudinal movements in the opposite direction. As far as the
function of the posterior portion of the internal layer is concerned, it
remains similar as during the medium position of the jaw. It can also be
assumed that the alternate contraction of the muscles of the right and left
half allows certain transverse movements of the jaw during digging (bur-
rowing). However, the scope (diapason) of such movements is very small.
During this, the condyle of the jaw (mandible) fixes in the external ridge
of the fossa glenoidea which, as was shown above, plays а role of fixator
for specific types of movement in the mandibular joint. During this type
of movement, the masseter muscle takes up the maximum load.

Of the muscles forming the masticatory complex, the temporal muscles
attain the greatest development in mole rats. This is in complete accord
from the viewpoint of adaptation to burrowing because the temporal
muscle is a basic muscle which allows the forward movements of the lower
jaw and, as a result, takes up the main load during digging along with the
corresponding parts of the M. masseter medialis posterior which also
allows the forward movements of the lower jaw from the anteriormost
and medium positions to the original one.

As far as the unpaired transverse muscle of the lower jaw is concerned,
its function is additional to the symphysis of the fixator of the rami of the
lower jaw and has been discussed earlier.

43

Thus, the morpho-functional peculiarities of the structure of the
muscles of the masticatory complex completely confirm the differentiation
of the movements of the mandibular joint already described in the context
of the articulation of the lower jaw with the skull during functionally
different situations corresponding to the process of grinding food, biting
(gnawing), and digging. There is no doubt about the adaptive nature of this
process because along with direct specializations directed toward the per-
fection of the very process of digging, the defensive functions are also
inherent which are primarily concerned with the protection of the teeth
from premature erosion during “‘purposeless” (from a trophic point of
view) forward movements of the lower jaw which accompany digging
activity. The latter, as has been observed, is achieved by either partial or
full non-coincidence of the grinding surfaces of the upper and lower
molar rows.

It is known that the degree of development of the structures becoming
attached to the bone is directly related to the degree of development and
functional characteristics of the muscles to be attached; in other words,
according to the direction and force of the muscular pressure which is ex-
perienced by them. In this regard, the research of М. 5. Lebedkina (1957) is
of much interest since it sufficiently shows that there is a close relationship
of the corresponding structures of the skull to the force and peculiarities
of distribution of masticulatory pressure on the masticatory apparatus of
the Lagomorpha. Looking at these common regularities the functional
importance of all the basic structural characteristics of the skull of Spala-
cidae, which are concerned in one way or another with the influence of the
masticatory muscles, becomes understandable. A general character of the
structure of the skull in all Spalacidae is the presence of a strong sagittal
and a considerably long lambdoid ridge, besides a well-expressed zygo-
matic mastoidal edge. The adaptive nature of these structures becomes
clear if it is considered that they are the sites of attachments of different
parts of the temporal muscle, causing the forward movement of the lower
jaw and thus taking up much of the load during biting movements of the
excavation cycle. Of the three parts of the temporal muscle, the pars
parietalis attains the greatest development because of which the sagittal
ridge is considerably stronger and thicker than the lambdoidal ridge and
the malar-mastoid ridge. Lastly, due to their being considerably weaker
than the pars parietalis, the lambdoid and temporal portions of the tem-
poral muscle are like comparatively thin-walled films. However, the lamb-
doid ridge is considerably inclined forward which, undoubtedly, increases
its tenacity because it considerably substitutes the strength coupled with
the contraction of the lambdoid portion of the temporal muscle directed
in another position of the ridge.

In view of the morpho-functional peculiarities of external layer of the

44

masseter muscle, the structural characteristics of the masseter surface of
the skull, on which the masseter lateralis superficialis anterior and the
masseter lateralis profundus muscle are attached, also become clear. This
surface has a special structure for the attachment of the anterior part of
the external layer of the masseter muscle—the anterior ridge and its other
parts (site for attachment of the masseter lateralis profundus muscle) with
a slight angle in relation to the longitudinal axis of the grinding surfaces
of the rows of the permanent molars. Lastly, the research of N. N. Voront-
sov (1963), carried out on skulls of Cricetidae of different types, serves as
an example for the presence of biting movements in the sagittal plane.
Perhaps the broadening of the jugal process of the mandible and of the
external wall of the suborbital fossa has to be considered as a resistance
to the forces directed toward the fissure and in some individual cases—
also a considerable inclination of the anterior parts of the zygomatic
arches from below—forming the malar angle. The large dimensions of the
suborbital foramen are also most probably correlated with the degree of
development in the masseter medialis anterior muscle passing through
this foramen.

A specific complex of adaptations for digging with the help of incisors,
directly related to the peculiarities of the working of the muscles of the
masticatory apparatus, is observed in the lower jaw also. This is seen
firstly by the presence of well-developed fossae and ridges. The places of
attachment of the pars parietalis of the temporal muscle are on the hori-
zontal branch in the intervening space between the alveolar edge and the
ascending branch of the comparatively high and slightly backwardly in-
clined coronary process and the special corono-alveolar groove (notch),
the upper edge of which has an appearance of a sharp ridge in highly
specialized representatives. There is an attachment of the lambdoidal and
temporal portions of the temporal muscle on the external side of the
coronary process and in the region of the corono-alveolar groove. Signi-
ficant differences in the structure and position of the angular process on
the mandible, which serve as a site of attachment for all the superficial
and partly deeper portions of external layers of the masseter muscle, are
related to the development of mechanisms allowing maximum movement
of the lower jaw in a lengthwise direction in the anteriormost position.
The said process underwent considerable changes during evolution. In
the primitive representatives of the family (subfamily Prospalacinae), it
has a tendency only for shortening and bending outward, and in highly
specialized ones (subfamily Spalacinae), it took the form of a prolonged,
highly developed ridge completely sweeping laterally on the side walls of
the alveolar process. Thus in the lower jaw, as in the skull, the most signi-
ficant adaptive changes took place in the structures providing the most
perfect and “economic” fixation of the musculature from the biomecha-

45

nical point of view, which properly brought up the lower jaw in order to
move it forward, i.e., the adaptive changes took place to enhance the
movements of the burrowing cycle.

As far as the structure of the teeth is concerned, the incisors have been
absolutely changed, particularly the lower ones. The latter is completely
in order because, as has often been mentioned, the incisors take the main
load while burrowing. However, the lower incisors being greatly movable,
should play a larger role than the upper ones. Naturally, the incisors of
mole rats have not lost the function of cutting (gnawing) foodstuff which
is so characteristic of all other rodents. Yet, these adaptations cannot be
taken as the most important ones because the nature of the grinding
movements in Spalacidae does not differ principally from the same in the
majority of representatives of other families of the order.

One of the main adaptive changes in the structure of the incisors
of mole rats, related primarily to an increase in its working surface, can be
seen in the trend of upper and lower teeth toward an increased width in
comparison to the antero-posterior cross section. Because of this, the said
peculiarity of the structure is better expressed in the lower incisors than
in the upper. In addition, the lower incisors of mole rats are less curved
as compared to forms in which the incisors are not adapted to burrowing
which, perhaps, offers the most suitable direction to their working surfaces
and happens to be common to specialized shrews and burrowing animals
in which the process of burrowing in one or the other way is combined
with the incisors.

As has been observed above, the upper incisors, because of their almost
immovable fixation (the degree of mobility completely depends upon the
range of movement of the skull), play mainly a passive role in burrowing.
In fact, their function during burrowing is less than their function during
gnawing and mainly consists of merely chewing lumps of soil cut by the
lower incisors. Because of this, the structure of the upper incisors, with an
exception of the already noted specific peculiarities, is on the whole
similar to the same as in other Myoidea. The lower incisors carrying the
main load, underwent considerably adaptive changes because of their
great mobility, predetermined by the nature of the joint of the lower jaw
with the skull. First of all, the tendency of these teeth for their general
elongation during evolution has to be noted. Thus, the length of the lower
incisors in some very specialized representatives of the family considerably
exceeds the length of the jaw measured from the apex of the symphysis.
This becomes possible because of the elongation of the free end of the
incisor and also by a considerable development of the alveolar process.
As in all rodents, the incisors of mole rats are without roots and are
characterized by constant growth. The posterior portion of the tooth is
the zone of reconstruction and, moreover, the incisor is pushed forward

46

because of its growth. The significance of the highly developed alveolar
process in mole rats is understood in the light of the aforesaid. The high
development is primarily related to the maximum increase in the zone of
development of the incisor which perfectly reconstructs the tooth during
its constant wearing off at the time of burrowing. The alveolar process, as
a site for an attachment of certain muscles of the masticatory complex, has
to be given secondary importance.

The permanent molars of mole rats have been adapted mainly for
feeding on comparatively soft and succulent vegetation (roots, bulbs,
bulbiferous root crops, roots of different plants and, to a lesser extent,
stems, leaves, seeds and tubers). The type of food completely explains the
structure and the presence of permanent molars—only exhibiting a ten-
dency for reduction in the lines from the primitive members to highly
specialized representatives, average height of coronas, comparatively
narrow grinding surfaces, and a predominance of folded structures above
tubercular structures. The latter, along with the form of grinding surfaces
for which little difference in the width and length of the corona is char-
acteristic, and also the disposition of the molars in two rows, would seem
to indicate a probably equal distribution of masticatory movement in
longitudinal and horizontal directions. Most probably the masticatory
movements in mole rats on the whole are ellipsoidal, the largest diameter
of the ellipsis approximately corresponds to the direction of the longi-
tudinal movement of the lower jaw. A reduction in the length of the
toothrows is not only related to the type of food, but also at the same time
represents a defensive device.

Among the other devices in mole rats whose function is to protect the
rows of permanent molars from premature wearing, the presence of pro-
tuberant lips, specific for shrews (burrowing animals) which avoid earth
entering the mouth during burrowing, is foremost, and in accordance with
the latter, the elongated diastema provides a maximum carrying forward
of the burrowing organ, incisors, beyond the masticatory section of the
oral cavity. -

ARRANGEMENT ОЕ THE SKELETAL AND MUSCULAR SYSTEMS ОЕ THE
SKULL AND THE POSTCRANIAL SKELETON OF MOLE RATS FOR TRANS-
PORTATION AND THROWING OUT OF SOIL WITH THE HELP OF THE HEAD

One aspect of the burrowing cycle of mole rats is the transportation
and throwing out of excavated earth from the entrance hole, mainly with
the help of the head. The adaptive significance of ejection of soil is difficult
to evaluate because Spalacidae are characterized by exclusively under-
ground feeding habits and burrowed food tunnels, the length of which
may exceed 300 meters. In burrowing, the soil is thrown out through

47

special exit holes which are situated at a distance of 0.5 to 3.0 meters from
one another all along the length of the feeding tunnel. This hole is con-
nected to them by an almost vertical shaft of three to five cm or more in
depth. The earth accumulates over them in so-called mounds (hills) so
very representative of the burrowing activity of mole rats. The following
data gives an idea of the intensity of soil ejection from burrows and feeding
tunnels. As observed by P. P. Gambaryan (1960), Microspalax nehringi
throws out 21.7 kg of earth in two hours of activity; according to N. M.
Dukel’skaya (1932) who obtained data during a study of the burrowing
activity of Spalax microphthalmus Gild, it was observed that the latter
could eject five kg of soil on the surface within half an hour. In both cases,
observations were made under natural conditions and hence the normal
excavating activity of mole rats may be judged from them. It should be
noted that M. nehringi burrowed tunnels in stony ground where almost
half of the ejected soil contained chips of stones of small and average
dimensions (up to 100 g) and some of them had weights of even more than
200 g.

The transportation of soil from food tunnels consists of two stages: (1)
transportation of soil which has been dug out by the incisors and thrown
by the front and hind feet in a horizontal or slightly inclined direction
toward the outlet; and (2) pushing up the accumulated excavated soil along
the vertical shaft on the outside. Both stages differ by different loads acting
on the neck and head region and the pectoral and pelvic girdles.

In the first case, as has been observed by Gambaryan in M. nehringi
under natural conditions, mole rats never transport portions of earth
weighing more than 0.5 kg in the horizontal or slanting tunnels, and an
accumulated mound of earth of more than five cm. The shafts of accu-
mulated earth found in opening horizontal and vertical tunnels, weights
and dimensions of which exceeded the aforementioned limits, were, in all
cases without exception, proven to be the plugs which mole rats usually
prepare at the end of their use. The earthen plug is usually denser than
the surrounding earth and has some portions of earth excavated by mole
rats. Its thickness may reach 20 cm. Thus, the transport of earth in hori-
zontal and slanting food tunnels is accompanied by an ejection of a com-
paratively small quantity of earth of little weight. During this, the main
load falls on the atlas-skull (occipital) joint and parts of the forelimbs,
although some of it is shared by the hindlimbs. However, the role of the
latter in the said process is very small. A proof of this is provided by the
fact that the weight of the muscles of the pelvic girdle in Spalacidae is
twice (2.2) less than the weight of the muscles of the shoulder girdle.
Besides, compared to burrowing animals of the group Myoidea, the mus-
cles of the hindlimbs of Spalacidae are least developed. Thus, according
to Gambaryan (1960) the relative per cent of the weight of the muscles of

48

the pelvic girdle to the general weight of the skeleton in Spalacidae is
around 29.0 as against 55.3 in Mesocricetus auratus Waterhouse, 67.0 in
Microtus socialis Pall. and 58.0 in Rattus norvegicus Berk. Perhaps the
general weakening of the girdle of the hindlimbs is almost characteristic
of shrews because the same phenomenon is also observed in zukors (34.0),
mole voles (31.0), and also in those burrowing animals which are well
adapted to burrowing like long-clawed field voles (36.0). Accordingly, in
the process of transporting soil along the horizontal and slanting tunnels,
most probably a complex movement comes into play related, firstly, to
the lifting of the head and secondly, to the straightening of the elbow and
shoulder joint. During this, slightly less energy is spent in transporting
comparatively small portions of soil than for throwing out in a few
attempts, larger portions through the vertical outlets, since the lesser
weight of the thrown-out earth in this case is compensated by the con-
siderably longer distance and, consequently, also by the time taken for
the efforts necessary for carrying the soil to the outlet.

The ejection of soil to the surface through the narrow shaft leading to
the surface is accompanied by short but vigorous efforts directed strictly
upward. It is natural that the magnitude of these efforts is determined
not only by the weight of the column of earth to be ejected but also
by the extent of erosion of the wall of the outlet as well as the resis-
tance of the already excavated earth partially adhering to the exit outlet
through which the remaining portion of earth is thrown out. It should be
remembered that while this takes place with one movement, the mole rat
usually throws out quite a few transported portions of earth. Thus, as
observed by P. P. Gambaryan (1960), columns of about 45 cm in height
can be ejected onto the surface by the mole rat; according to A. F. Anisi-
mova (1938), the giant mole rat can throw out an even larger quantity. As
a result, the animal has to make a great effort when ejecting earth through
the outlet though this process is of short duration. It was experimentally
proven that М. nehringi can lift a load of 6.2 kg to a height of 7 ст.
Generally, Spalacidae can easily lift comparatively large loads, 1.е., loads
which exceed by 30 to 40 times the weight of their own body, to a height
of about 8 to 9 cm. Because the outlet shaft is strictly vertical, the complex
movements performed during this should be similar to those accompanied
by the lifting of loads during the experimental situation. Gambaryan
(1953, 1960) with the help of X-ray determined that the individual elements
of the skeleton of a mole rat take the positions shown in Figure 21 during
the process of lifting a load. Thus, it is clear that during the process of
ejecting earth, as well as transporting it, the basic movements are lifting
the head, straightening the elbow and, to a lesser extent, the shoulder
joints. However, it differs from the first stage—ejection of earth from the
burrow accompanied by transportation under conditions of a horizontal

49

or slanting feeding tunnel—in that the posterior extremities do not take
an active part in this work, assuming only the role of body fixators in the
space. During this, the center of gravity of the animal shifts into the region
of the shoulder joints.

Hence, the nature of the movements in the process of transporting and
ejecting earth is the same in principle, differing only by degree of partici-

Be ai ln

D

Figure 21. Skeleton contours of a mole rat lifting a load
(by Gambaryan, 1960).

50

pation of the hind extremities and the magnitude of single loads. Conse-
quently, the main adaptations corresponding to the above-mentioned
specializations must be primarily related to a specific reconstruction of
the skeleton and muscular systems of those sections of the anterior part,
which take up the maximum load in this process. These are the atlal-axial-
skull joint and the shoulder girdle. In addition, the springy and fixed
adaptations of the body, which are related to the similar speciality of ejection
of excavated earth, have to be taken into consideration. These systems
have been very completely studied by P. P. Gambaryan (1960).

The head is lifted by the M. rhomboideus capitis which is a part of
the complex M. rhomboideus, and also by the complex of the dorsal
muscles of the neck in which M. splenius, M. semispinalis capitis and
the M. rectus capitis dorsalis are rather well-developed. The per cent
ratio of the weight of these muscles to the general weight of the
muscles of the extremities in M. nehringi is 35.8, whereas it is only 6.2
for the rest of the muscles in the neck region. In addition, the above-
mentioned muscles of mole rats are considerably better developed than
in all other shrews and burrowing animals of the group Myoidea. Thus,
the relative total weight is 24.26 in zukors; 15.5 in long-clawed field voles;
12.88 in average hamsters; 10.58 in mole voles; 8.0 in rats of the genus
Rattus; and finally, 9.47 in rats of the genus Nesokia. In this way, the
greatest similarity in the development of magnitude for this parameter is
observed between mole rats and zukors for which the ejection of earth
from burrows and food tunnels by the head is characteristic. However,
the characters of specialization in this direction are more strongly dev-
eloped in Spalacidae than in Myospalacinae. It is better to look into the
details of the structure of each of these muscles in order to know their
roles.

Of the muscles concerned with lifting the head, the M. rhomboideus
is the best developed. For example, it is 12.65% of the muscles of the
extremities in M. nehringi. Its relative weight exceeds more than four to
five times the weight of the same muscle in shrews and burrowing animals
from the group Myoidea in which the process of throwing out earth from
burrows is not accompanied by head movements. Thus, the magnitude
of the corresponding index is equal to 3.02 in average hamsters, 4.0 in
long-clawed field voles, 2.48 in mole voles, 1.60 in rats of the genus Rattus,
and 1.52 in rats of the genus Nesokia. However, similarities to mole rats
are, after all, found in zukors (11.21). This muscle in mole rats originates
all along the lambdoid ridge of the skull and terminates on the scapula
covering a major portion of the axis of the latter and about one-fourth of
the nearby fossa, starting from the cranial angle of the scapula (Figure 22).

The M. semispinalis capitis, whose relative weight is 10.29, is less
developed in mole rats. To the degree of its development, it exceeds the

51

same muscle in all other shrews and burrowing animals from the group
Myoidea including even zukors. The magnitude of the ratio of its weight
to the total weight of the muscles of the extremities is 6.17 in zukors,
6.30 in long-clawed field voles, 5.89 in mole voles, 4.87 in average ham-
sters, and finally, 3.82 and 3.86 respectively for rats of genera Rattus
and Nesokia. This muscle originates from the occipital surface of the skull

Figure 22. Muscles of the neck from (A) above and (В) the side, and (С)
of the body in Microspalax nehringi (Sat.) (by Gambaryan, 1960).

I—M. rectus capitis dorsalis major; 2—M. obliquus capitis cranialis;

3—M. obliquus capitis caudalis; 4—M. multifidus cervicalis; 5—M.

longissimus capitis; 6—M. scalenus; 7—M. semispinalis capitis; 8—M.

rhomboideus capitis; 9—M. anconeus longus; /0—М. anconeus lateralis;
11—М. dorsoepitrochlearis; 12—М. serratus ventralis.

medial to the M. rhomboideus capitis and M. splenius and terminates on
the lamellar processes of the first five sternal and transverse processes of
the last two to three (sometimes four) cervical vertebrae (Figure 22).

The M. rectus capitis and M. splenius are almost equally developed
in mole rats. The relative weight of the first is equal to 6.78, and the second,

52

6.08. Both muscles exceed twice or more the same in degree of development
in other shrews and burrowing animals of the suborder Myoidea including
zukors for example, as noted by Gambaryan (1960); the indices of relative
weight for each of these muscles are equal respectively to 3.30 and 3.58 in
zukors, 2.03 and 3.17 in long-clawed field voles; 1.96 and 3.03 in average
hamsters, and 1.39 and 2.70 in compositodontus shrews. The splenius
muscle represents the outer layer of the whole complex of dorsal muscles
in the neck. It originates from the occipital bone, deeper than the rhom-
boid muscle, and terminates in the fascia stretched between the lamellar
processes, neural ridge, and other bony process of the first three to six
thoracic vertebrae, and the dorsal processes of the cervical vertebrae
(Figure 22). The M. rectus capitis originates from the occipital surface of
the skull, deeper and below to the site of the attachment on the M. semispi-
nalis capitis, and terminates on the process of the axis and partially on
the wings of the atlas (Figure 22).

The peculiarities of attachment for all the foregoing muscles show that
they are the flexors of the atlanto-occipital joint; moreover, looking at
the nature of the attachment, the most effective appears to be the rhomboid
muscle of the head. Its considerable development in rodents and shrews
can be explained on the basis of those which have adapted themselves to
eject earth from the burrows and food tunnels with the help of the head,
mainly mole voles and zukors, and can be proven from the above data
about the relative weight of the rhomboideus capitis muscle in individuals
of the above-mentioned families. However, in mole rats as distinct from
Myospalacinae, the bending effort in the said joint increases many times
in view of the additional efforts by similar muscles in the bending complex,
first of all the muscles of the head and also the rectus capitis of the head,
and scalemus muscle which is moderately developed in zukors. The latter
fact indicates a better developed specialization in mole rats compared to
Myospalacinae. The adaptive peculiarities of the construction of individual
structures of the skull and the cervical region of the vertebral column,
and also the peculiarity of articulation of the first with the last in mole rats,
can be understood in the light of the aforesaid.

As already mentioned in previous sections of this work, the presence
of a highly developed, broad, and considerably forward slanting occipital
surface with a well-developed lambdoid ridge, is a specific character of
the skull of Spalacidae. The greatest width of this surface considerably
exceeds the length of the braincase of the skull and the angle of the slant
in relation to the longitudinal axis of the grinding surfaces of the permanent
molars is approximately equal to 45°. The adaptive significance of these
systematic differences is quite clear because the occipital surface, including
the lambdoid ridge, is a site of attachment for all muscles forming the
complex of flexors of the atlanto-occipital joint, whose significance in

53

conjunction with the adaptation for ejecting earth from burrows and feed-
ing tunnels with the help of the head, was shown earlier. The anterior
slant of the occipital surface also has a specific adaptive significance. It
primarily plays a role in the fixation of different sections of the skull, and
experiences considerable muscular tension. It is clear that such a position
of the occipital surface facilitates a substitution of equivalent forces for
the force of traction. It is interesting that such speciality of the skull among
present-day families of the order Rodentia is characteristic only of Spala-
cidae and from fossil representatives, the specialized burrowing animals
with possibly a mode of digging similar to mole rats, the Oligocene Cylin-
drodontidae. Differing from Spalacidae, the zukors have more or less
well-defined structures on the occipital surface with a site for attachment
of the rhomboid muscle of the head; however, because of the moderate
development of all other muscles in the flexor complex of the atlal-axial-
skull joints, the occipital surface is not so wide and has almost no forward
inclination.

The structure of the cervical region of the vertebral column assumes a
special function because of the above-mentioned peculiarities, experien-
cing the direct effect of the load lifted and of the muscular tensions accom-
panying the contraction of the dorsal muscles attached to the neck either
fully or partially. A general shortening of the cervical section and the
resultant reduction in the length of its individual components is an adap-
tive reaction to such influences during the process of evolution. The same
is the case with individual vertebrae which are immovably fixed to each
other and to the thoracic section, while retaining considerable mobility in
the atlanto-occipital joint. The formation of an immovable cervical region
in mole rats is accompanied by a development of the so-called interlocking
joint of the 2nd to 7th cervical and the Ist thoracic vertebra. This is
achieved by way of the cranium-like juxtaposition of comparatively large
articulating surfaces of cranial and caudal articulating facets of adjoining
vertebrae (Figure 7), and by the widening of their dorsal bows, as a result
of which the edges of the latter closely attach to each other in adjoining
vertebrae and also by the formation of special interlocking projections
and concavities on the articulating surfaces of the body of the vertebrae.
Perhaps there are some changes in the structure of the neural spines and
the bony processes of the 2nd to 4th thoracic vertebrae, the site of attach-
ment of M. rectus capitis of the head and M. splenius in the complex of
the above-mentioned adaptations. Thus, the neural spine of the 2nd
cervical vertebra in mole rats is considerably widened in a transverse
direction with a bifurcated upper end, and the neural spines of the afore-
said thoracic vertebrae have a tendency toward a similar widening and
sometimes even to a fork-like bifurcation of the upper ends.

The specificity of movement in the atlanto-occipital, accompanied

54

mainly by the lifting and lowering of the head under considerable 1оа4$, _
brought about the peculiarities of the cranial joint with the Ist cervical
vertebra, and of the latter in turn, with the axis. As has been shown in an
earlier section of this work, a transgression of occipital condyles on the
base of the occipital bone accompanied by a contact of the articulating
surfaces of the right and left condyles in Spalacidae is characteristic.
Corresponding to this, a considerable transgression on the ventral arch
of the atlas of Spalacidae is observed for surfaces for the articulation of
condyles of the skull with their reciprocal contacts. Hereafter the portions
of the occipital condyles of the skull and their corresponding articulating
surfaces on the Ist cervical vertebra, passing over the base of the occipital
bone and ventral arch, differing from the basal ones, will be called
ventral by us. When the head is lowered, the basal and ventral portions
of the occipital condyles and their corresponding surfaces of the Ist
cervical vertebra take equal part in the articulation. This type of arti-
culation of the skull with the vertebral column is maintained also in the
initial stages of the lifting of the head. However, the ventral portions of
the articulating surfaces move apart and only their main portions take
part in the articulation. Thus, the greatest contact of the articulating sur-
faces in the atlanto-occipital joint is made in the initial stages of its bending.
_ The adaptive significance of the above-mentioned peculiarities of arti-
culation of the skull with the atlas in Spalacidae becomes clear, if it is
considered that the initial stage of the bending movement, accompanied
by the lifting or hauling of a load with the help of the head, occurs with
the greatest loads (Gambaryan, 1960). Similar functions are carried out,
as a whole, also by the atlal-axial joint. The increase in the area of the
- contacting surfaces in Spalacidae is also accompanied by an increase in the
ventral sections of the posterior articulating surface of the atlas, and also
of the corresponding articulating surfaces of the 2nd cervical vertebra by
way of its fusing under the odontoid process.

In the adaptation toward ejecting excavated soil from burrows and
feeding tunnels with the help of the head, in addition to the above-men-
tioned characteristics of structure in the skeleto-muscular system of the
atlanto-occipital joint, the specific structural formations of skeletal ele-
ments and muscles of the anterior limbs also play an important role in
Spalacidae. The research of P. P. Gambaryan (1960) is sufficiently con-
vincing that in addition to the aforementioned flexing movements of the
atlanto-occipital joint, the load lifting is accompanied also by a maximum
flexing of the elbow and shoulder joints (Figure 21). It is natural that such
types of movements of the anterior limbs during the process of evolution
are a result of stabilizing selection directed mainly toward the perfection
of mechanisms allowing movement of the type described. This reformation
in Spalacidae is mainly concerned with strengthening the extensor muscles

95

of the elbow and shoulder joints, and also the places of their attachments,
the corresponding point on the skeleton. P. P. Gambaryan (1960) observed
equal muscular tension for the flexing and lifting of the elbow and shoulder
joints (Figure 23). It becomes clear on the basis of the scheme drawn of
the elbow joint extensors that the most appropriate, from a functional
point of view, are the elongated head of the M. anconeus longus and the
M. dorsoepitrochlearis, and to a lesser extent, the lateral and medial heads
(M. anconeus lateralis and M. anconeus medialis); the least appropriate
is the M. epitrochleoanconeus. One end of the M. anconeus longus of the
shoulder is attached all along the caudal edge and caudal surface of the
scapula including the caudal process, and the other end on the olecranon
of the ultra—to be specific, on its apex—and the M. dorsoepitrochlearis
originates on the broadest muscle of the back from its lateral side as a
tendon, ending on the proximal end of the radial process of the radius.
The M. anconeus lateralis and the M. anconeus medialis of the shoulder

Figure 23. Resultant forces of elevation and extension of (A) the shoulder and
elbow joints, and (B) structure of clavicle-shoulder joint of the mole rat Micro-
spalax nehringi (Sat.) (by Gambaryan, 1960).

J—+resultant extension of elbow joint; 2—the same of shoulder joint; 3—equally
effective elevation of shoulder joint; 4—acromion process of scapula; 5—bony
meniscus; 6—clavicle.

originate—the former on the distal part of the large tubercle and partially
on the ridge, and the latter on the humerus—and terminate respectively
on the lateral side of the olecranon right up to its base and its dorsal
surface. Finally, the M. epitrochleoanconeus is attached on the medial
condyle of the shoulder bone on one side and on the apex of the radial
process of the radius from the other.

The research of P. P. Gambaryan (1960) has shown that in Spalacidae
the strengthening of some extensors of the elbow joint, having the most

56

proper direction for equal force, takes place. Firstly, that of the М. dorso-
epitrochlearis and the M. anconeus longus of Spalacidae exceeds twice or
thrice the degree of development for similar muscles in the majority of
highly specialized shrews and burrowing animals of the group Myoidea.
For example, the per cent relation of the weight of the said muscles to the
total weight of muscles in the limbs in Spalacidae is 1.8 against 0.6 in
average hamsters, 0.3 in domestic voles, mole voles, and gray rats, 0.6 in
long-clawed mole voles and finally 0.2 in compositodontus rats. Besides,
the index of the relative weight of this muscle considerably increases in
zukors (1.3), which is, however, related to the similar specialization of the
anterior extremity of the representatives of this subfamily in ejecting
excavated earth from underground burrows. An exactly similar tension is
experienced by the M. anconeus longus in Spalacidae, the relative weight
of which in mole rats is 8.6 against 4.3 in average hamsters, 4.5 in domestic
voles, 6.2 in long-clawed mole voles, 5.8 in mole voles, 3.3 in gray rats,
and 4.2 in rats of the genus Nesokia. In zukors the M. anconeus longus
of the shoulder is better developed than in Spalacidae (9.5). In the opinion
of P. P. Gambaryan (1960), the latter fact is explained, aside from the
specialization for throwing out earth with the help of the head, by the
additional functions of the anterior limbs concerned mainly with loosen-
ing the soil during the process of digging with the claws. As far as
the M. lateral and medial anconeus of the shoulder and the M. epitro-
chleoanconeus are concerned, they are similar in degree of development
in Spalacidae compared to the same in other shrews and burrowing animals
of the group Myoidea. It has been stated above that maximum straightening
of the head in mole rats is simultaneously accompanied by the straightening
of the shoulder joint. Hence, it could be expected that in Spalacidae there is
an opposite action on the effect of the M. anconeus longus which, though
being an extensor of the elbow joint, acts as a flexor for the shoulder joint
simultaneously. The latter is accomplished by the force of the M. rhom-
boideus of the head and also by the M. subclavius and M. supraspinatus,
and the cervical part of the M. acromoitrapezius and the M. serratus ven-
tralis, the role of which in the said process becomes clear only on the basis
of the peculiarities of their attachments. In this connection, a short descrip-
tion of the above-mentioned muscles of the shoulder girdle is given below.
The morpho-functional characteristics of the M. rhomboideus of the skull
have been examined. The M. subclavius originates on the first rib and
terminates in the clavicle and distal part of the acromion process of the
scapula; moreover, this fixation on the scapula is seen exclusively among
rodents in representatives of the families of mole rats and zukors. The
M. supraspinatus starts from the supraspinatus fossa of the scapula and
terminates on the large tubercle of the shoulder bone. The M. acromiotra-
pezius attaches itself by one end to the cervical and first two thoracic

ый

vertebrae (along the median line of the neck, starting from the lambdoid
ridge of the skull) and by the other end on the axis of the scapula, starting
from the axial tubercle up to the metacromion process. Finally, the M.
serratus ventralis originates from the longitudinal processes of the last
four cervical vertebrae and the first seven to nine ribs, terminating on the
medial surface of the cranial edge of the scapula, distal to the site of fixation
of the rhomboid muscle of the head.

Thus, all the muscles mentioned exert an influence on the scapula
because of their disposition against the tension (force) of the M. anconeus
longus of the shoulder equalizing or even enhancing the flexing effect (in
the shoulder joint) and actually forcing the M. anconeus longus to exclu-
sively flex the elbow joint. All these muscles in mole rats are considerably
well-developed. However, of them the rhomboid muscle of the head and
the subclavius muscle are better developed in comparison with other
specialized shrews and burrowing animals of the group Myoidea. Data on
the relative weight of the former have already been given above (page 51).
As far as the latter is concerned, in Spalacidae it is five or more times better
developed than the same muscles of other shrews and burrowing animals
of this group of rodents, exception zukors again. Thus, the per cent
relation of the weight of this muscle to the general weight of the muscu-
lature of the anterior and posterior limbs in Spalacidae is 3.41 against
2.30 in zukors, 0.35 in average hamsters, 0.28 in domestic moles, 0.42 in
long-clawed mole voles, 0.70 in mole voles, 0.19 and 0.30 respectively in
gray and compositodontus rats (Gambaryan, 1960).

All the aforesaid sufficiently explains the structure of individual ele-
ments of the skeleton of the anterior limbs of Spalacidae, directed mainly
toward the perfection of mechanism that arranges the work of muscles
most economical from a biomechanical point of view which, naturally, is
first of all related to the formation of sites of attachments for the muscles.
As has been shown, the sites of the attachment of basic muscle complexes
taking part in the extension of the elbow and shoulder joints during soil
ejection with the help of the head, are mainly the cranial and caudal edges
of the scapula, its acromion process, and also the radial tubercle of the
radius bone. Hence, it is in order that the above enumerated points of the
skeleton of the anterior limbs underwent the greatest changes during the
evolution of mole rats. It is known from previous sections of this work that
the scapula in Spalacidae is elongated, naturally accompanied by a corres-
ponding elongation of its cranial and caudal edges and also of the acro-
mion process. The adaptive significance of such formations is quite clear if
it is assumed that they are accompanied by a maximum development of the
sites of attachments of the enumerated muscular complexes according to
their functions. In addition, it is characteristic for the scapula of representa-
tives of this family (Spalacidae) to have specific structures for the attach-

58

ment of one of the main extensors of the elbow joint, the М. anconeus
longus. The caudal process, absent in the same bones of all other Myoidea
of the old world, even in zukors, is one of them. Moreover, a similar
elongation of the scapula is characteristic only for Myospalacinae, of all
the representatives of fossil and presently living families of the group
Myoidea of the old world; this confirms the correctness of the functional
evaluation of the trait discussed in mole rats as a specialization for throw-
ing out earth from burrows and feeding tunnels with the help of the head.

During the lifting of loads with the head, accompanied in mole rats by
an ejection of dug out earth from burrows and feeding tunnels, great
strength is required, whereas the speed of movement plays a secondary
role. An increase in the strength and function of muscles extending the
elbow joint could be expected in this connection, especially because of a
typical structure of the mechanism of this joint which, as is known, is a
lever of the second type where the point of rest (fulcrum) is situated on
the paw, the olecranon serving as a point of application of force, and the
point of resistance is the site of the support of the shoulder bone in the
forearm. It is natural that the greater the height of the radial process and
the lesser the length of the rest of the part of the radius bone, the more
powerful will be the straightening of the elbow joint though with less speed.
Hence it could be expected in Spalacidae, looking at their specialization,
that the olecranon should be considerably more developed in them than in
shrews and burrowing animals of the group Myoidea in which the process
of ejection of dug up soil is not accompanied by head movements. This
fact has been convincingly shown by P. P. Gambaryan (1960). The per cent
proportion of the length of the olecranon process to the length of the rest
of the ulna in different representatives of Spalacidae is as follows: in M.
nehringi, 53; in Spalax giganteus Nehr., 50; in S. microphthalmus, 60. In
other Myoidea, the magnitude of this index is 21 in the common hamster,
18 in average hamsters, 23 in hoofed lemmings, 19 in true lemmings, 12 in
gray field voles, 19 in water rats, 16 to 19 in rats of the genus Microtus
and some other lemmings, 32 in long-clawed mole voles, 24 to 31 in mole
voles, 12 in forest mice and, finally, 18 and 20 respectively in gray and
compositodontus rats. At the same time, zukors again show a fine example
of a convergent similarity to mole rats in the structure of the olecranon
process which in Myospalacinae is considerably longer than in Spalacidae.
The ratio of its length to the length of the rest of the ulna in representatives
of this family is up to 75.

The straightening of the shoulder and elbow joints in mole rats during
the process of lifting up loads is accompanied by a movement of the body
forward and upward in relation to the limbs. The muscles allowing this
movement also take part in the work of the extension of the shoulder
joint. The forward movement of the body improves the working conditions

59

of the rhomboid muscle of the head which is the main extensor of the
atlanto-occipital joint. The subclavius muscle, the cervical part of the M.
serratus ventralis (already described), and also the M. ectopectoralis con-
siderably help in such a movement. The latter originates along the whole
sternum and terminates on the ridge of the large tubercle of the shoulder
bone. The considerable development of this muscle in mole rats is accom-
panied by a considerable reinforcement of the site of its attachment on
the sternum, firstly by the formation of an elongated median ridge—the
keel. Closely correlated to this process there is a considerable widening
and shortening of the anterior ribs in Spalacidae because of which the
fixation of the sternum is maximum. Besides, as has been mentioned before,
the subclavius muscle originates from the anterior ribs. In the light of the
aforesaid, the considerable reinforcement of the ridge of the large tubercle
of the shoulder bone in Spalacidae (deltoid process) becomes under-
standable.

All the muscles mentioned above increase the power of extending or
straightening of the shoulder joint. Their rather strong development in
Spalacidae leads to a little weakening of the proper extensor of the shoulder
joint, the M. supraspinatus (whose relative weight is 1.3 against 1.6 to 1.9
in other rodents). The predominance of the extension force in the shoulder
joint above the flexion force is so considerable that in Spalacidae, the addi-
tional flexor of this joint—M. spinotrapezius—becomes well-developed
as a compensation. It originates from the neural spines of the second last
thoracic and the anterior lumbar vertebrae, terminating on the tubercle
of the axis of the scapula. The indices of the relative weights of the latter
allow one to examine its excellent development in Spalacidae as compared
to other burrowing Myoidea. Thus, according to Gambaryan (1960), the
value of this index in Spalacidae is 3.90 against 0.89 in average hamsters,
1.74 in long-clawed mole voles, 0.90 in domestic voles, 1.74 in zukors,
1.65 in mole voles, 1.15 in gray rats, and 1.27 in compositodontus rats.

Further, all the muscles mentioned above (M. serratus ventralis, sub-
clavius, and ectopectoralis) play a role as fixators of the body at the time
of lifting a load.

It becomes necessary to examine a number of adaptive structural
formations in the distal points of the anterior limb which obstruct the
compression (flattening) of the feet under the influence of the force of
gravity, as compensatory reactions to the pressure of body weight which
multiplies because of the load to be lifted from the earth. In such cases,
the callus, bearing a specific structure, and also the arched structures
formed by the elements of the carpus and metacarpus which are character-
istic for representatives of this family, act as buffers. As has been shown
in the research of P. P. Gambaryan (1960), the callus of mole rats con- ©
siderably protrudes in relation to the free surface of the paw (Figure 16)

60

and is very thick. The callus does not yield to pressure in a recently dead
animal, whereas it does yield comparatively easily in other rodents. The

Figure 24. Structure of callus
of Microspalax nehringi (Sat.)
(by Gambaryan, 1960).

I—horny layer of epidermis;
2—flat epithelium; 3—cubicle
epithelium; 4—papillary layer;
5—loose connective tissue; 6—
connective tissue septum; 7—
conglomeration of fat cells.

density (thickness) increases because of the
accumulation of fat cells in the layer of the
porous connective tissue formation (Figure
24).

The compression of the paw and the dis-
position of individual elements of the carpus
and metacarpus react in equal degree. The
skeleton of the forefoot of a mole rat is
characterized by the following peculiarities.
The pisiform bone is placed laterally and
prepolex medially (Figure 25). At the apex
of these bones, the aponeurosis of the long,
paw muscle joins with the fibrous tissue of
the callus and the periosteum of these bones.
Two of its strongly developed thickenings
go to the prepolex and the pisiform bone,

and approach the callus as very thin bundles fading into fibrous bundles
of padding in the callus. The pisiform leans against the IV to V carpale

and ulnare on one side and from the
other, against the radius. The prepolex
leans against the fused radiale and
intermediate of the carpals and partly
the fused radius (Figure 25). The distal
portion of the callus spreads out up
to the carpo-metacarpal joint of all
the five metacarpals of the paw. Thus,
an arch (arch cupola) is formed at the
base of the forepaw of mole rats, the
external boundary of which thrusts
through the callus into the carpo-
metacarpal joint, through the sesamoid
bones into the carpal bones, and the
posterior boundary passes through the
prepolex and pisiform bone into the
distal section of the forearm. The pres-
sure passed on through the bones of the
forearm tries to straighten this arch to
which the dense callus offers an obstacle
and the long paw muscle, thus enforced,
approaches the boundary of the arch
in Spalacidae (Gambaryan, 1960).

Figure 25. Scheme of structure of the
wrist of the mole rat Microspalax
nehringi (Sat.) (by Gambaryan, 1960).

A—longitudinal section; B—cross
section. J—thickness of callus; 2, 3—
aspect of palm and long palm mus-
cles; 4—pisiform; 5—ulnae bone of
carpus; 6—prepolex; 7—radiale and
intermediate bones of carpus; 8—
radius; 9—ulna; /0—metacarpus;
11—longitudinal arch of joint; 72—
cross arch of joint.

61

In mole rats as far as the hind limbs are concerned, they carry out very
insignificant lever-like functions during considerably complex process of
ejecting earth from burrows and feeding tunnels, including the adjustment
of the body in space, and during the first stages of burrowing accompanied
directly by digging and transportation of earth in a horizontal or slanting
tunnel, they have a very insignificant influence concerned mainly with
forwarding the body and taking it back. Hence, it would be correct to
explain, perhaps, the specific characteristics of their construction in repre-
tatives of this family while explaining the manner of throwing out the dug
up earth.

CERTAIN CHARACTERISTICS IN THE STRUCTURE OF THE LIMBS OF MOLE
RATS RELATED TO ADAPTATIONS FOR EJECTING LOOSENED EARTH
DURING THE PROCESS OF DIGGING

It is known that the limbs of mole rats do not play a direct part in
loosening soil during the process of digging. However, they are totally
involved in the next stage of the digging cycle, which directly precedes
the stage of ejecting earth from burrows and feeding tunnels and is related
to the throwing back of soil loosened by the incisors. In this complex of
movements, the main load, as in other burrowing rodents, is taken up by
the hind limbs which, in Spalacidae, underwent the greatest change. In
addition, the specialization in this direction has influenced greatly the
structure of the forelimbs, mainly the distal points which play a consider-
able role in the said process.

As shown by the research of B. S. Vinogradov (1946) and P. P. Gam-
baryan (1960), rodents which loosen the soil during digging with the help
of the claws of the forelimbs undergo considerable structural changes
during evolution mainly related to an increase in their dimensions, pre-
dominantly in longitudinal elongation. During this, there is a thickening
of the claw at the same time in a latero-medial direction, often accom-
panied by an almost complete closing of the borders of the claw plate on
the volar surface of the latter with a maximum isolation of the sole plate.
In mole rats which loosen soil with the help of incisors, the claws of the
forelimbs are capable of only throwing it back; because of this, they
appear to be shortened and flattened compared to the claws of rodents
mentioned above. Thus, the height of the claw of the forelimbs in mole
rats is usually less than its width or is approximately equal to it, whereas
in zukors and long-clawed mole voles, the first measurement exceeds the
second by more than one and a half times. The claw plate on the claws of
the forelimbs of Spalacidae somewhat overhangs the volar edges, and
the sole plate is strongly curved (Figure 26). The latter, in turn, consider- |
ably increases the expelling surface of the claw. It must also be noted that

62

the claws of mole voles have exactly the same structure. These are rodents
which, like mole rats, loosen the earth with the help of incisors. The
validity of the functional evaluation of these structures in the construction
of claws for the forelimbs is further confirmed by the fact that despite
the differences in the type of digging, they have the same structure—almost
similar to that of the hindlimbs of all of the above-mentioned burrowing
animals of the group Myoidea. The latter fact is quite understandable
because in mole rats, as in mole voles, zukors and long-clawed mole voles,
the distal components of the hindlimbs, besides acting as a fulcrum, carry
out no other function than that of throwing out dug up soil.

Figure 26. Structure of the claws of the wrist (by Gambaryan, 1960).

A to C—Prometheomys schaposchnikovi Sat.; D to F—Méicrotus arvalis
Pall.; G to —Microspalax nehringi (Sat.); A, D, G—wrist with free side;
В, Е, H—claw of third finger; С, А. I—same, transverse section.

The process of specialization toward loosening soil with the claws of
the forelimbs is usually related to the reinforcement of the whole muscular
complex in rodents—the flexors of the forefoot, mainly the M. flexor
digitorum profundus. In Spalacidae, however, this muscle is not very well
developed because the distal components of the forelimbs are adapted
only for throwing back the already loosened soil. Thus, according to the
data of P. Р. Gambaryan (1960), the ratio of the weight of the М. flexor
digitorum profundus to the total weight of the muscles of the anterior
limbs in Spalacidae lies in the range of 1.40 against 5.87 in zukors, and
4.02 in long-clawed mole voles. Weak development of this muscle is
characteristic of mole voles (1.82) as in Spalacidae. The lesser develop-

63

ment of the flexors of the forefoot in mole rats is, perhaps, in close relation
to the reduced surfaces of their attachment. The latter is mainly due to a
general reduction in the distal components of the forelimbs in representa-
tives of this family.

It should be noted that the specialization of digging with the help of
the claws of the forefeet is accompanied by a reinforcement of the rotator
of the foot, which again does not happen in Spalacidae; the degree of
development of the round pronator and supinator is two to three times
less than the same muscles in zukors and long-clawed mole voles.

As far as the proximal part of the anterior limb is concerned,
rotation is characteristically absent here too. Thus, for example, in Spala-
cidae the shoulder joint underwent considerable changes related to its
conversion from multiaxial to mainly monoaxial. The latter is possible
because of the peculiarities of the structure of the clavicular-scapular joint,
accompanied by the formation of a special bony menisculus (Figure 23),
which is absent in similar joints in other burrowing rodents. The nature of
such a joint restricts the range of movements in the said joint to strictly
the sagittal plane (flexing-extending) which, as has been shown in a pre-
vious section, is mainly related to adaptations toward ejection of earth
from burrows and feeding tunnels with the help of the head.

It has been said above that, in the process of throwing out loosened soil,
the greatest load is taken up by the hindlimbs, which have undergone
maximum changes in mole rats as compared to some other burrowing
rodents. They are mainly related to the fixation of muscle complexes which
take the body behind, while bending the knee joint, and at the same time
pulling it upward. This process is related to a maximum lengthening and
reinforcement of the caudal border of the ischium, and the formation of a
very strong ischiatic tubercle in addition to the ischial ridge. The ischiatic
tubercle and ridge are arranged on the pelvis of mole rats almost in a
longitudinal direction which, perhaps, creates the best condition for work-
ing the aforementioned muscles. The general reinforcement of the ischio-
pubic portion of the pelvic girdle has to be seen as a compensatory reaction
to the formation of a considerable muscular tension in this portion, accom-
panied by a reduction of the pubic bone due to fusion with the ischium,
thus leading to a tendency toward an overgrown closed foramen character-
istic of all representatives of Spalacidae without exception.

In Myoidea, some rearrangement of the mechanism of extension of
the tarso-metatarsal joint, related to an increase in the relative length of
the calcaneous tubercle and strengthening of the M. soleus, has to be
viewed as an adaptation to throwing out soil loosened with the help of
incisors. Thus, the per cent relation of the length of the calcaneous tubercle
to the length of the third metatarsus bone in Spalacidae ranges from 51
to 53 against 43.3 in zukors, 36.0 to 37.0 in mole voles, 35.0 in long-clawed

64

mole voles, 19.0 in average hamsters, 17.4 to 19.5 in voles of the genus
Microtus. From the indices shown above, a general tendency toward
elongation of the calcaneous tubercle is observed from burrowing animals
to shrews of different degrees of specialization. The functional significance
of this phenomenon becomes quite clear if it is considered that at the end
of the calcaneous tubercle a number of muscles make their attachment
(including the M. soleus), the contraction of which brings about the
extension of the tarso-metatarsal joint. On the other hand, the proximal
portion of the fibula is comparatively broader than in other Myoidea,
and serves as a site for the attachment of the M. soleus. The above re-
arrangement of the sites of attachment for this muscle in Spalacidae and
in mole voles is closely related to the degree of its development, because
the relative weight of the M. soleus in representatives of the aforemen-
tioned families, about twice exceeds the same muscles in all other burrow-
ing Myoidea (Gambaryan, 1960).

A SHORT ACCOUNT OF ADAPTIVE CHANGES OF CERTAIN
STRUCTURES OF THE SKULL AND THE SKELETON IN THE
EVOLUTION OF MOLE Rats

It has been seen in earlier sections that the main direction of special-
ization of mole rats in the process of evolution was an adaptation toward
an underground way of life. Aspects of the digging cycle of representatives
of this family, related to the loosening of soil with the help of incisors
and its ejection from burrows and feeding tunnels with the help of the
head, predetermined the greatest changes in the morphology of the mus-
cular system of the skull and the skeleton performing the above process,
mainly of the masticatory apparatus and the mechanisms related to an
extension of the atlanto-occipital, the elbow, and partly, the shoulder
joints. Unfortunately, the paleontological data available at present does
not allow one to carry out a complete phylogenetic analysis of the changes
in all the aforementioned structures. The remains of the mandibular rami
isolated teeth and, to a lesser extent, broken portions of the masticatory
sections of the skull of Spalacidae, are preserved in a fossil condition in
a comparatively better manner and, as a result, offer a very promising
basis for judging the character and trends of similar reconstructions of
the masticatory apparatus, but the trend of changes during the process of
evolution for other systems can be judged only on the basis of indirect
data based primarily on observations of degrees of development for the
various traits in living representatives of the family which have reached
different degrees of specialization toward an underground way of life.
Thus, the selection of the system during an analysis of its adaptive refor-
mation during evolution is predetermined by the researcher, not so much

65

by considering the importance of the system per se in the background of
the whole adaptivity of the group, but by the peculiarities of preservation
of the paleontological material.

In a previous section of this work it was shown that the masticatory
apparatus of mole rats, together with normal feeding functions concerned
with the chewing and grinding of foodstuff, also happens to provide the
first stage of the digging cycle related to loosening the soil. In fact, the
very speciality of the masticatory apparatus for burrowing in rodents of
this family, happens to be the main trend in the evolutionary processes
which determined, finally, all the adaptive characteristics of the skeleton
and muscular systems of the skull. Comparatively minute adaptive changes
of the structures functionally concerned with only normal feeding, mainly
the permanent molars, existed in the phylogenetic morphology of the
family, and existed perhaps in close dependence on the adaptation to bur-
rowing, while possibly playing a specific selective role in the general
process of specialization toward underground feeding habits.

A study of the characteristics of the structure of the masticatory
apparatus in fossil and living representatives of the family, belonging
to different stages of specialization for burrowing, permitted determining
the main adaptive rearrangements of the said systems, and is the result of
a stabilizing selection influencing mole rats mainly in the following basic
directions:

1. A rearrangement of sites of attachment for the muscles of the
masticatory complex related to providing the most suitable conditions
for their working during the burrowing cycle from the viewpoint of
“biomechanics” ;

2. A structural reconstruction of the very burrowing structures—
incisors—directed mainly toward a perfection of their forms and their
quickest replacement in the process of wearing;

3. A perfection of the defensive apparatus protecting the rows of
permanent molars from premature wearing during meaningless move-
ments of the lower jaw.

The changes in the structure of the sites of attachment for the masti-
catory muscles during the evolution of mole rats is achieved in the follow-
ing way. In ancient mole rats the masseter surface of the skull, which
serves as a site for the fixation of the M. masseter lateralis superficialis
anterior and the M. m. lateralis profundus, though positioned in a hori-
zontal plane, however, is not as markedly curved as in present-day mole
rats because its anterior tubercle is almost absent (Figure 40). Further,
during the process of evolution of the family, a tendency toward a relative
enlargement of the suborbital foramen is observed, which is related to the
degree of development of the anterior position of the M. masseter medialis,
which passes through this foramen. Thus, in representatives of this sub-

5

66

family of ancient mole rats, the greatest diameter of the suborbital foramen
easily exceeded the combined length of the two anterior permanent molars,
whereas in living mole rats it is approximately equal to the length of a
full line of М! to МЗ, or exceeds it. The dimensions of the suborbital
foramen in representatives of the genus Microspalax are, on the average,
less than in the more highly specialized Spalax.

Of the structures of the masticatory apparatus of mole rats, the greatest
changes have occurred in the lower jaw during evolution. These rearrange-
ments during evolution are as follows. In very primitive representatives
of the subfamily of ancient mole rats, the lower jaw still maintained the
plan of its construction as in rhyzomyides. This is observed mainly from
the relative independence of the angular process placed on the articulating
process and having a common edge with it (Figure 40), and also from the
lateral position of the apex of the comparatively small alveolar process in
relation to the similar proc. angularis. A certain compensation for that
much of the unspecified structure of the angular process in ancient mole
rats, differing very little in principle from the same structures in Myoidea,
which are not specialized for underground feeding habits, is achieved by
the profuse development of the lower tubercle of the masseter surface.
The angular process loses its contact with the articulated in the highly
specialized representatives of the subfamily of living mole rats because of
the union of the alveolar process on the lateral wall. Additionally, it greatly
loses its independence because it completely adheres to the proc. alveolaris
and also strongly protrudes in front. As a result of such union with the
proc. angularis, the apex is situated laterally to the similar one of the
well-developed alveolar process (Figure 3). It should be noted here that
in more primitive representatives of the genus Microspalax, especially in
fossil Pliocene species, the angular process is characterized by a greater
isolation than in more highly specialized fossil and present-day species of
the genus Spalax. The functional significance of such a reconstruction of
the angular section of the lower jaw during evolution is quite clear, because
the most suitable conditions are produced in this way for strengthening
the respective parts of the external layer of the masseter muscle, which
becomes attached to this process, and finally, for allowing movements of
the lower jaw in the anteriormost position, in addition to accompanying
movements.

Along with the general development of the sites of attachment for the
masticatory complex of muscles, a recent tendency toward increasing the
extent of the natural and false articulating surfaces is observed in the
evolution of mole rats. Thus, for example, the combined length of both
surfaces of the skull serving for the articulation of the lower jaw in the
relatively primitive Microspalax exceeds about two and a half times the
length of the row of permanent molars, whereas in the majority of repre-

67

sentatives of the highly specialized genus Spalax, the former measurement
usually thrice exceeds the first. It has to be stressed, however, that there is
no sharp difference in the degree of development of the given trait between
the above-mentioned genera of mole rats. One of the most primitive repre-
sentatives of the genus Spalax, the Bukovin mole rat, appears to be an
intermediate stage in which the relative measurements of the lengths of
the articulating surfaces approximately coincide with similar ones in the
highly specialized species of the genus Microspalax. The importance of
such reconstructions in the mandibular joint is very clear, viewed from
the development of a rather greater differentiation of the movements of
the digging and trophic cycles accompanied, in addition to the general
development of the digging mechanism, by the development of defensive
structures which protect the rows of permanent molars from premature
wearing (see details on page 33).

It has been seen above that the structural reformations of the digging
structures like incisors, during evolution, were mainly directed toward the
development of a tooth form befitting the animal’s mode of life, and also
the development of special structures, causing the most rapid replacement
of the incisors during the process of intensive wearing. It can be assumed
theoretically that the development of a tooth form, whose basic function
is related to digging in mole rats, is inevitably related to a maximum widen-
ing of its working surface, with an accompanying widening of the tooth
crown. Investigations of the relative width of incisors in fossil and living
representatives of the family which have attained different degrees of
development during evolution in regard to an underground mode of life,
allow one to determine a general trend toward a widening of the upper
and lower incisors, increasing from ancient representatives of the group
to highly specialized ones. This is quite clearly illustrated by the following
data. The least wide incisors are carried by representatives of the Pliocene
subfamily of ancient mole rats (Prospalacinae). Thus, the ratio of the width
of lower incisors to an antero-posterior cross section is 68.6, in Mid-
Pliocene Prospalax rumanus Simionescu 78.4, and in P. priscus (Nehring)
80.8. Among specialized subfamilies of present-day mole rats (Spalacinae),
a species of the genus Microspalax has preserved comparatively narrow
incisors. Hence, the values of corresponding ratios in M. ehrenbergi
(Nehring) are 76.0 to 83.2 to 94.0 for the upper, and 64.0 to 74.5 to 86.2
for the lower teeth; 82.6 to 90.0 to 95.0 and 75.7, 80.6, 84.6, 87.5 in the
Late Miocene-Early Pliocene M. compositodontus sp. nov.; 95.4, 100.0,
100.0 and 70.3 to 86.2 to 93.5 in the Mid-Pliocene M. macoveii (Simio-
nescu); 72.2 to 87.2 to 95.8 and 71.4 to 81.2 to 90.0 in the Mid-Pliocene
M. odessanus sp. nov.; 72.2 to 87.2 to 95.8 and 70.0 to 79.6 to 85.2 in the
presently living M. nehringi (Satunin) and finally 86.4 to 101.5 to 119.0
and 80.0 to 92.1 to 115.0 in the modern М. leucodon (Nordmann). Repre-

68

sentatives of the highly specialized genus Spalax have wider incisors. The
values of the said indices are respectively: 100.0-104.2-108.6 and 90.0-
97.7-104.1 in the Late Pliocene 5. minor W. Topachevskii; 90.9-106.3—
114.0 and 95.2-98.0-108.1 in present-day S. giganteus; 108.3-119.0—
130.0 and 100.0-103.9-109.0 in the modern S. arenarius Reshetnik;
104.0-112.0-120.8 and 100.0-109.5-120.7 in Pleistocene (Glacial epoch)
and present-day 5. microphthalmus; 110.3-119.5-130.7 and 97.0-104.3.-
110.7 in present-day 5. polonicus Mehely; and finally 110.3-115.8-
133.0 and 100.0-101.2—103.0 in present-day and subfossil 5. graecus
Nehring. It has to be stressed, however, that this trait is influenced also
by age variables; moreover, the changes in the above-mentioned types
toward reducing the value of the said index in highly specialized representa-
tives of the genus Spalax take place exclusively due to the young and a
portion of semi-aged animals. This has been discussed in greater detail
in the sections that follow.

As in all other rodents, the incisors of mole rats are characterized by a
constant growth which, in itself, is a compensatory reaction to a rather
intensive wearing out during the life of the animal in comparison to other
teeth. As is known, the zone of development of the incisors is at its pos-
terior portion. During growth, the tooth is progressively pushed out of
the alveoli and during this process, the worn out working parts are re-
stored. The evolution of the mechanism for restoring the wear and tear
of the incisors is, first of all, related to the maximum growth of the general
length of the tooth itself, and with an increase in the extent of its zone
of growth. Thus in specialized shrews and burrowing animals, burrowing
with the help of incisors, the incisors are subjected to a maximum wearing
_ out during their lifetime and are characterized by the largest length in
comparison to the incisors of rodents in which they have only a trophic
function. In some cases of a high degree of specialization (Rhyzomyides,
and especially mole rats, as well as some burrowing animals of the group
Myoidea), the portion of the incisor within the jaw could exceed in length
the portion out of the jaw. In view of this, the elongation of alveoli takes
place due to the formation of alveolar tubercles and, in most specialized
forms, even strong alveolar processes. During this, naturally, the formation
of the latter is accompanied by a maximum increase in the general length
of the zone of restoration of the tooth. Among all other Myoidea of the
old world, the mole rats are forms whose alveolar processes have 4еу-
eloped to the greatest extent. In primitive representatives of the group,
it is usually less developed than in highly specialized ones; the develop-
ment in the length of this process in the evolution of Spalacidae exemplifies
this. In primitive fossil Prospalacinae, the alveolar processes are least
developed. It is considerably lower in height and located laterally in
relation to the angular articulated process. In fact, the proc. alveolaris

69

still maintains its rhyzomyide plan of construction in representatives of
this subfamily. An increased height of the alveolar process is observed
in specialized Spalacinae compared to ancient mole rats; moreover, in
the phylogenetical line in the forms of this subfamily depending upon
the degree of specialization, there is a progressive growth of this trait.
Thus, in representatives of the most primitive subgenus of the genus
Microspalax (within the subfamily of true mole rats), in the European
Pliocene M. macoveii and M. odessanus, and also in present-day North
African and Asiatic M. ehrenbergi, the alveolar process is comparatively
small (approximately equal in height to the articulated one), though the
process of the blending of the angular process with the external wall of the
alveoli is complete (Figure 50). In more specialized representatives of the
genus Microspalax (subgenus Mesospalax), the alveolar process consider-
ably exceeds in height the articulated one (Figure 61). Finally, in the
majority of highly specialized representatives of the genus Spalax the
height of this process considerably exceeds the same for proc. condyloideus.
There is only one exception offered by one species of the genus Spalax—
the present-day S. giganteus, whose degree of development of the alveolar
process is about the same as that in Mesospalax. It has also to be noted
that the general direction of formation for this trait in post-embryonic
development in mole rats completely corresponds to the aforesaid tend-
ency of its development in the evolutionary trend of the family.

Among the devices concerned with digging which also protect the rows
of permanent molars from premature erosion during meaningless and
trophic movements of the lower jaw, the mechanism of the mandibular
joint comes first since, as was shown above, it allows full or partial non-
contact of the rows of permanent molars during the movements of the
digging cycle, and also the adaptation which allows maximum extension
of the digging organs—the incisors—from the oral cavity, thus obstructing
the entrance of soil into the mouth during digging. The latter is related to
the lengthening of the diastema section of the skull and of the lower jaw,
which is also noticed during evolution. Thus, of all the representatives of
the family, the primitive fossil Prospalacinae has the shortest diastema.
The value of the diastema tooth relationship is 151.0 for the upper jaw,
and 66.0, 66.7 for the lower jaw. In the Mid-Pliocenic modern mole
rats of the genus Microspalax (nominal subgenus) a tendency toward a
lengthening of these sections is observed. For example, the value of the
corresponding index of the lower jaw of the Mid-Pliocenic M. macoveii is
equal to 62.5-70.8-75.0, and in the little later Mid-Pliocenic М. odessanus,
62.5-74.4-81.0. The values of the diastema-tooth relationship in the
primitive but presently living M. ehrenbergi are within a very close range
(141.4-179.4—213.5 for upper jaw, and 61.5-77.0-93.4 for the lower jaw).
In more highly specialized modern representatives of the subgenus Meso-

70

spalax, the diastema is longer оп ап average (respectively 160.0—202.7—
247.0, and 70.4-87.0-106.3 in М. nehringi; and 162.5—-207.0-280.3 and
70.0-91.0-125.4 in М. leucodon). Finally, the lengthiest diastema is
carried by representatives of the genus Spalax. Thus, the value of this
index is 194.4—216.0-243.7 for the upper jaw, and 72.4-86.1-102.9 for the
lower jaw in 5. giganteus; and respectively, 178.3-224.6-266.7, and
84.3-111.9-126.6 in 5. arenarius; 177.0-233.8-317.0, and 90.5-114.3-
138.7 in 5. microphthalmus; 198.8—230.4—263.6, and 100.0-109.3—122.0
in 5. polonicus; and finally, 217.0-238.8-258.0, and 82.8—100.3—107.4
in S. graecus. The general trend of changes in this trait in evolution is
confirmed also by the process of its restoration in post-embryonic dev-
elopment. The minimum values of the indices given above for each species
belong exclusively to the young and partly semi-mature animals.

It was shown in previous sections of this work that the adaptations of
the skull and the skeleton, which are functionally related to the ejection of
dug up soil from burrows and feeding tunnels with the help of specific
movements of the head and the factoral girdle of the limbs, play an impor-
tant role in the life of mole rats. The structural modification regarding
this specialization in the evolution of the family is concerned with, firstly,
the reconstruction of the mechanisms for straightening the atlanto-occipital
and elbow joints. Unfortunately, the paleontological material presently
available is insufficient to arrive at firm conclusions about the basic direc-
tion in the evolution of these systems, though some additional information
on contemporary forms which has come into the hands of research workers
gives some starting point for arriving at such conclusions. As shown by
researchers, a general tendency toward the reinforcement of the site of the
muscular attachment is observed during the process of evolution for mole
rats, viz., the flexors of the atlanto-occipital joint. This is particularly
observed in evolutionary changes in the degree of development of the
occipital process. Thus, for example, the least developed occipital process
is observed in the most primitive representatives of the genus Microspalax
(nominal subgenus), the Pliocene M. odessanus, and the contemporary M.
ehrenbergi. Furthermore, a considerable reinforcement of these structures
is seen in representatives of the subgenus Mesospalax within the said genus,
which finally reaches maximum development in the most highly specialized
representatives of the families—the fossil and present-day species of the
genus Spalax. Along with the aforesaid processes in the evolution of the
group, perhaps the changes in the structure of the whole occipital surface
of the skull related to reformations directed fully to the stabilizing selec-
tion in the direction of widening it (occipital surface) and lessening the
angle of its incline in relation to the base of the skull, were also included.
It can also be assumed that during the evolutionary progress of the group
the structures of the cervical and partly of the thoracic sections of the

71

vertebral column underwent considerable changes. Most probably, these
modifications are, as a whole, concerned with the perfection of the afore-
said (see page 46) attaching the protecting adaptations within a family, and
in the highly specialized subfamily of present-day mole rats, are concerned
with changes depending upon the differences in structure of these sections
in Microspalax and Spalax (see page 125). It is highly probable that during
the process of evolution of the group, considerable changes occurred in
the individual structures of the proximal units of the anterior limbs con-
cerned with the sites of attachment for the muscles; for example, the
extensors of the elbow joint whose working attains a great importance as
shown above (see page 54) in the whole complex of the specialization, and
the throwing out of dug up soil from burrows and feeding tunnels, which
is inherent in representatives of this family. The general tendency toward
elongation of the elbow process of the ulna and for strengthening the
caudal ridge of the scapula in very highly specialized representatives, would
seem to point to a genetic development in mole rats.

Of the structures of the masticatory apparatus functionally concerned
with a normal trophic activity and not with digging, first and foremost,
are the permanent molars. During evolution a tendency toward simpli-
fication of their grinding surface is observed, which was caused by a full or
partial reduction of their individual processes—at first the mesocone and
paracone in the upper ones, and the mesoconid and entoconid in the
lower teeth, and also caused by a reduction in the number of roots due
to the fusion of the latter themselves. The evolution of the permanent
molars in representatives of the subfamily of true mole rats can serve as an
illustration of this. Thus, for example, in the most primitive species of the
genus Microspalax, the Mid-Pliocenic M. compositodontus, the front upper
and lower permanent molars have a free mesocone and paracone, the
mesoconid and entoconid forming accordingly the external and internal
forks. The corresponding process is widely placed. Sometimes the width
of the neck of the internal fork of M, is approximately equal to one-third
of the total length of the grinding surface of the tooth, or even exceeds it
(Figure 6). In other species of this subgenus, the mesocone and the meso-
conid exhibit all stages of reduction—even up to full reduction. Thus, the
mesocone almost completely vanishes in the Mid-Pliocenic М. macoyeii
and M. odessanus, not to mention the recent M. ehrenbergi, and the meso-
conid is comparatively highly developed in M. macoveii (preserved in the
teeth of the young and partly in the semi-mature, though it is closer to the
entoconid than in M. compositodontus, Figure 56), and is represented only
by vestiges on similar molars (the initial stages of erosion) in M. odessanus
and M. ehrenbergi (Figure 60). Furthermore, in representatives of another
subgenus of the genus Microspalax, the present-day Mesospalax, the
anterior permanent molars preserved a stage of development almost

72

identical to the same of the Mid-Pliocenic М. odessanus, 1.е., it is char-_
acterized by the presence of an unfused paracone during the initial and
middle stages of erosion, and of a free entoconid only during the very
beginning stage of tooth erosion. Finally in the highly specialized Spalax,
the paracone is fused during all the stages of erosion with the anterior
collar, occurring freely only in very young animals as an exception, and the
entoconid is completely covered by the posterior collar, being preserved
in the form of a small fold only in the initial stage of erosion in the per-
manent molars (Figures 75 and 76).

The general simplification in the structure of the grinding surfaces of
permanent molars during evolutionary processes was, perhaps, accom-
panied by a reduction also in roots. This can be proven by the following
data. Thus, for example, the number of roots in the anterior upper perma-
nent molars in representatives of the genus Microspalax varies from two
to four, and in the most highly developed Spalax, it varies from one to
three.

The changes described above in the structure of permanent molars
most probably reflect the general specialization of representatives of the
group for eating underground portions of vegetation, during which pro-
cess the decrease in the degree of folds of the teeth is compensated to a
certain extent, by an increase in their hypsodont nature.

CHANGES IN CERTAIN STRUCTURE OF THE SKULL OF
MOLE RATS DUE TO AGE. SEXUAL DIMORPHISM

The embryonic development of mole rats has not been studied recently.
Hence in this section, we shall restrict ourselves only to the fixation of
changes in some morphological structures in post-embryonic development.

The changes in the general structure of the body due to age and colora-
tion of hair, except for their absolute measurements, are not very markedly
expressed in mole rats. It can only be said that the young and semi-mature
animals within a population are darker, as a rule, than the mature and
aged. However, some individual structures of the skull and lower jaw
demonstrate very clear changes due to age, which can be detected even
visually, and also in the mean values of a number of indices. In some
cases these changes correspond to the general trends in skull changes
during the evolution of the group; thus in addition to important paleon-
tological material, this data also serves as one more additional source
for an objective examination of the basic trends of development in the
evolution of the family.

Of the structures of the skull in mole rats which undergo the greatest
change in post-embryonic development, the sagittal and lambdoid ridges
are the main ones. These structures are absolutely not developed in the

75)

young, hardly formed in the semi-mature, and reach full development only
in mature and aged animals (Figure 27). The form and dimensions of the
parietal bone are closely related to the degree of development of these
ridges, making it narrower because of the formation of the sagittal ridge
(Table 1), and their combined forms change from being approximately
perpendicular in the young and semi-mature to being mainly trapeze-
shaped (genus Microspalax) or stellate (genus Spalax).

Data are given in Tables | and 2, which characterize the changes in
individual parts of the skull and lower jaw of mole rats in post-embryonic
development. They indicate that changes in the skull due to age are related

A B С О Е

Figure 27. Changes in the axial skull and the lower jaw of mole rats
according to age, Spalax microphthalmus США. x 1.6.

A—young; B—semi-mature; С, D—mature; E—old individuals.

74

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76

to an elongation of the whole rostrum, the lower diastema and nasal
openings, and to a reduced constriction behind the eyes. In addition, the
width of spacing in the molar arches and the relative width and height
of the occipital bone increase because of age. The height of the alveolar
process on the lower jaw and of the horizontal branch considerably
increases, as does the thickness of the latter. The upper and lower incisors
show a tendency for widening. A simplification of the grinding surfaces
of the permanent molars takes place with age due to full or partial dis-
appearance of the individual processes due to erosion, and the fusion of
other processes among themselves accompanied, as a rule, by a closure
of the incoming loop into a mark. The nature of such changes can be
seen at a glance in Figures 28 and 29. It has to be noted here that in highly
specialized forms, the said process terminates at a rather earlier stage of
teeth erosion than in the more primitive types. Detailed schemes of changes
due to age in the structure of the rows of permanent molars in different
representatives of the family have been given in the sections devoted to a
description of individual species.

Thus, in the post-embryonic development of mole rats, as perhaps in
all mammals in general, there is a restoration of the most important
exosomatic structures from the viewpoint of taxonomy in the taxa of
the lines of a family which mainly reflect the peculiarity of the specializa-
tion of the group as a whole, as well as of its individual representatives.
The latter is proven by the fact that all the changes due to age mentioned
above take place, after all, as a result of the activity of the main adapta-
tions and structures related with them, functionally related to the pecu-
liarity of the way of life of mole rats. Furthermore, some of the changes
described above (elongation of diastemic portions, tendency toward a
reinforcement of the ridges on the skull, an increase in the height of the
alveolar process of the lower jaw, and a tendency toward a widening of the
upper and lower incisors, etc.) in the post-embryonic development of the
organism, considerably reflect the change during the evolution of the group.

Sexual dimorphism is not expressed in the external traits. Sexual
differences can be determined only on serial data on the mean values for a
number of traits in the structure of the skull and the lower jaw. Thus, the
skulls of females differ from those of males, in addition to some smaller
absolute measurements, on the average, by a rather shorter diastema and
hard palate, narrowed rostrum, and elongated temporo-parietal sections.
Furthermore, they are less in width in the area of the rostrum and incisors.
The nasal bones anteriorly, and the parietal bones together and indivi-
dually, are also relatively wider. The latter, perhaps, is correlated in
females to a rather weakly developed sagittal ridge, as compared to males.
It should also be noted that the occipital surface in females is placed far
more low. The lower jaw of females differs from that of males, in addition

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78

Figure 28. Changes in the upper row of permanent molars according to age in

Microspalax leucodon monticola Nehr. X5.

О to O—old individuals.

>’

A to E—young; F to /—semi-mature; J to N—mature;

79

to smaller absolute measurements, by a shortened diastema and also by a
relatively lesser height and thickness of the horizontal branch. The skulls
and lower jaws of females occupy, so to speak, middle position regarding

Figure 29. Age differences in the lower permanent molars of mole rats,
Microspalax leucodon monticola Nehr. XS.

A to E—young and semi-mature; F to K—mature; L to O—old individuals.

80

the degree of development for a number of traits mentioned above, bet-
ween the same traits of mature and aged males on one hand and young
animals on the other (Tables 1 and 2).

Of the skeletal bones, sexual dimorphism in mole rats is expressed
only in the construction of the pelvis. In females of the genus Microspalax,
the pelvic (ischial) axis of the said bones is only in contact with the wings
of the sacrum, but in males it fuses completely with the latter. In addition,
the pelvic bones in all representatives of the subfamily Spalacinae, without
exception, are characterized by an absence of a symphysis of the pubic
bones in females (open pelvis) as compared to the closed pelvis in males
(Figure 49).

ECOLOGICAL FEATURES OF MOLE RATS, THEIR
REPRODUCTION AND SIGNIFICANCE TO HUMAN BEINGS

Habitat and population numbers. Present-day mole rats are found mainly
in the arid and semi-arid zones, steppes and forest steppes, and have even
penetrated into the forests. It is very natural that within the foregoing
agroclimatic zones, the habitat of individual species of this family is charac-
terized by specific features. It was recently observed that the main factors
limiting the spread and number of mole rats are adaptive and tropical.
A common characteristic of the present-day Spalacidae, closely related
to the complete underground way of life of all representatives of the family,
is that they prefer soils of moderate density, avoiding quicksands as well
as very dense hard soils. The saline content and humidity of soils play,
in my opinion, an important role because it is known that mole rats are
absent from highly humid, hard and saline soils (nonstructured white
alkaline soil).

A large number of species are very dependent on the composition of
the associated plant community, and further on the availability of abun-
dant edible plants. Sometimes great numbers of mole rats live in places
where there is an abundant grass stand.

The habitat and numbers of individual species of this family have not
been studied regularly. The Afro-Asiatic mole rat of Ehrenberg has been
the least studied. All that is known is that under the arid conditions of
the African border of the Mediterranean Sea (Libya, United Arab Re-
public), the habitat of the species has a mosaic character. The habitat of
Microspalax ehrenbergi is exclusively confined to more or less humic
slopes; in the majority of cases they are greatly attracted to river basins.
They are absent in clay and in sandy deserts. In Mediterranean Asia
(Israel, Lebanon, Jordan, Syria, and Iraq), in my opinion, they live under
conditions similar to those of M. nehringi. The extent and density of their
vertical distribution in hilly areas is not clear.

81

The habitat of the Asia-Minor-trans-Caucasian mole rat Nehring (М.
nehringi) has been studied in detail (Satunin, 1920; Pkhakadze, 1940;
Pogosyan, 1946; Reed, 1958). In the trans-Caucasus this species lives in
the belt of feather grass and beard grass steppes on chestnut soils, at
heights of from 1,400 to 2,400 m above sea level (the population is thickest
at the height of 1,500 to 1,600 m). Reed (1958) observed them living in
northern Iraq in hilly areas at about 250 m above sea level, with an annual
rainfall of 435 mm. According to K. A. Satunin (1920) mole rats Nehring
live in humid valleys between hills covered with high grass stands and
comparatively humid meadows in Caucasia and the mixed region of
Turkey. A number of mole rat dugouts were observed where tulip plants
abounded in plantations. According to the data of V. A. Pkhakadze (1940),
in the Akhalkalak and Tsalkin regions in Georgia (USSR), they select
their habitat in meadows, pastures, and grain fields, living in pairs; their
preference is grain fields. Finally, as A. R. Pogosyan observes (1946) from
the Spitak and Agin regions of Armenian USSR, the mole rat Nehring
is often seen in grain fields and gardens; moreover, with reference to
grain fields, they are usually found more in the cultivated areas than in
uncultivated ones. According to Reed (1958), in northern Iraq, in addition
to the open biotopes, they live on hilly slopes, in shrubs, forest fellings,
and even penetrate into the thick of the forest. Data on the population
density are very scanty. It is only known that in the fields of the Spitak
and Agin regions in Armenian USSR, the population of mole rats Nehring
is considerably high. In some years, the figure may go up to eight to nine
beasts per hectare (Pogosyan, 1946).

The hilly European or white-toothed mole rat (М. leucodon), lives in
the cultivated back steppes, on hill slopes, river banks, and ravines, includ-
ing the roadside areas in the territory northwest of the Black Sea region
in the Ukraine (SSR); Moldavian SSR; and the mixed region of Rumania.
They are abundant in pastures, uncultivated gardens, vineyards, lucerne
fields, and many other grasses, in potato fields, and in sugar cane, onion,
and turnip plantations. Sometimes they are also found around a collective
farm boundary and near residential zones. They also live near the forests
and sometimes enter dense forest. They avoid highly humid marshy regions
in river beds (Averin, Lozan and Rozinskii, 1962). According to E. I.
Yangolenko (1965), within the Soviet territory they live under similar
conditions (in preserved virgin soils, in valleys of rivers and ravines, and
common pastures, as well as other soils which are not suitable for culti-
vation). They abound in hay-mowing grounds and cultivated lands under
grass. Because of a reduction in virgin lands, they have shifted to culti-
vated lands. Seasonal vertical migrations have been observed in the hilly
areas. The density of population is comparatively not high (from one on
ten hectares, to six to eight on one hectare) in the territory of the Ukraine

6

82

and Moldavia. It is considerably higher in the Soviet territory where on
hay-mowing grounds or perennial grasses, it went up to 23 individuals
per hectare.

Data on these aspects of giant mole rats (Spalax giganteus), are ex-
tremely scanty. They live in clay or sandy, semi-arid or arid zones, and
are found in great numbers where humidity is limited—tiver valleys,
hollow lakes, marshy steppes often with bushes, and islandic forests.
Evidences of the digging activity of this species have been found in western
Caucasus in uncultivated steppes, on black soils, and also on untouched
sands (Ognev, 1947).

The sandy mole rat (5. arenarius) inhabits exclusively the area around
the lower Dnieper (Aleskin) sands of the Kherson region (left bank of the
Dnieper River and west of Kakhovka). According to E. G. Reshetnik
(1941), it mainly lives on slightly moist, black sandy soils. It is absent on
the quicksands, devoid of plants, in Kuchugurakh. Characteristic habitats
of this species are abundantly found around the Golopristanskii region
of Kherson. They are particularly abundant where eryngo (Eryngium),
field wormwood, Ukrainian Salsify (Tragapogon sp.), pearly cornflower
(Centaurea sp.), Bermuda grass bungloss (Anchusa sp.), couch grass,
panicle, sedge (Carex), hilander, sheeps fescue, wheat grass (quitch grass),
silky apre (Festuca sp.), and snakeweed (Serozonera sp.) are predominantly
grown. In the majority of cases, the habitat of the sandy mole rat corres-
ponds to that of Scirtopoda telum Licht. It is found around the forest in
the Ivan-Rybalchanskii part of the Black Sea sanctuary and also in birch
groves. It is completely absent from the shores of the Tendrov Gulf,
Tendrov, and the surrounding islands. The number is considerably high
(seven to ten individuals per hectare).

The common mole rat (S. microphthalmus) is a typical resident of flat
steppes and the forest steppes west of the Dnieper River. It lives in the
foothills of the Caucasus. It particularly lives on the slopes of ravines and
in other lower areas, preferring fertile black soil with abundant grass. It
is occasionally found on sandy soils and cultivated lands (stands of peren-
nial grasses, millets, oats, maize, and other field crops, in gardens, melon
fields, and crop-saving forest plantations). Individual burrows were found
in the center of dense forests and populated areas. It avoids clay and very
loose sandy soil subject to aridity and also, very rarely, portions of flood
plains. N. M. Dukel’skaya (1932) gives the following characterization of
a typical, common mole rat habitat around the Petrovskii district of the
Saratov region. These mole rats live mainly in the grassy black soil
steppes, intermittently between the cultivated lands and dense forests.
They prefer those portions of steppes where dandelion, groundnut, and
chicory are predominant. The tilling of steppes brings about a migration
into the adjacent forest ranges, roadsides, and common pastures. After

83

the harvest of perennial grasses, and after tilling, the migration of mole
rats is reversed, but the main complex of burrows is concentrated in the
common pastures. In fields of millets, oats, and other field grains, and
similarly in gardens, there are lesser numbers. Usually, the habitats of
mole rats correspond with that of the speckled suslik (gopher) and the
common field vole. S. I. Ognev (1947) observed the common mole rat in
great numbers in the steppes of the Voronezh region where numerous
dugouts of these rats were concentrated on the slopes of ravines and gorges,
the boundaries of forest, and rarely, in the thick of the forest. The habitats
of mole rats have been observed on grit stone and sandy crests situated
on the border of the forest of Khrenov in the Khrenov region where
savory, wormwood, rabbit cabbage, and feather grass grow. The common
mole rat lives in the left bank steppes and forest steppes in the Ukraine,
under conditions similar to those described above (Reshetnik, 1941).
According to L. B. Beme (1931), the most typical habitats of these mole
rats in the Kuban steppes are portions of virgin lands and deposits on
black soils which have abundant plantations of perennial herbs. Some-
times, it goes particularly to fields of perennial grasses. Evidence of digging
activity, small mounds of earth, are also found on melon fields and in
spring crops, and sometimes (rarely) in winter crops. Finally, according
to K. N. Possikov (cited by Ognev, 1947) they live in open and hedge-
covered slopes of limited humid ravines with black soil under conditions
which exist in the hills of the West and Central Caucasus. It avoids clay
and sandy soils which are subject to intense drying. On plateaus (table-
lands), it is found in considerable numbers in valleys of the Malki and
Baksana Rivers where it lives in flooded fields, glades (clearings), gardens,
kitchen gardens, black thorn growths, plum orchards, areas with barberry,
hawthorn, and in places where somehow black soil predominates over
sandy or clay soils. Information on the density of population under dif-
ferent living conditions is extremely scanty. All that is known is that the
approximate number of common mole rats per hectare in the Kharkov
region may reach up to ten individuals in virgin land slopes in ravines, up
to five to seven in hay fields, and two in cultivated fields (Reshetnik, 1941).

The Podolsk mole rat (5. polonicus) in the right bank steppes and forest
steppes of the USSR lives in virgin land, roadsides, embankments of dirt
roads and railroads, common pastures, slopes of ravines and slopes
covered with bushes, afforestations, protected forest vegetations, forest
creepers, thick forests, nurseries and stands of lucerne, clover, castor,
and cotton. Sometimes it enters into grain fields and kitchen gardens. It
prefers black soil; nevertheless, differing from the common mole rat, it is
found quite often on sandy subsoils. According to K. F. Kessler (1851)
and E. G. Reshetnik (1941), these rodents were found on horizontal
terraces around the Kiev and Zhitomir regions. According to V. I. Abelent-

84

sev (1951), they were found in the right bank steppes of the Ukraine SSR
where an intensive grain industry has developed [observations were carried
out on the soil at the Vladimir Agro-silviculture (agricultural afforestation)
Experimental Station in the Nikolai region and in the Apostol district of
the Dneperpetrovsk region]. The Podolsk mole rat population is very thick
in field protective planting (shelter belt) and the sowings of perennial
grasses, though because of a deep ploughing of these grain fields (up to
27 cm), the majority of the burrows are destroyed and the animals die.
The number of galleries and fresh piles of earth thrown out by mole rats,
counted by Abelentsev in autumn and winter of 1949 and 1950, showed
that the animals are particularly active in winter in forest plantations, but
at the end of March and the beginning of April, digging is concentrated
on plains and the area between the bands where seeds of perennial grasses
are predominant. Mole rats are particularly abundant in field strips where
shrubs have been cut (like shoots of oak, elm, maple, honeysuckle, and
yellow acacia), and where a good stand of grass has come up. Here, the
number of galleries in winter doubled. The number of animals in such
types of bands fluctuates up to four individuals per hectare, in the autumn
months, and up to eight in the summer months. In old shelter belts of
forests where trees of 15 to 47 years have grown, the number per hectare
varies in the range of 0.3 to 1.75 individuals in the spring, and 0.43 to 3.0
in the autumn. It prefers perennial grass stands of three years, or stands of
old lucerne which, perhaps, is due to a greater number of roots and the
density of the soil. The number of 1.3 individuals per hectare is reached
under these conditions. The least density of population of this species is
observed in summer and winter in one-year lucerne stands; moreover, in
winter lucerne, the animals are seen only in pairs at sowing, and toward
autumn reduce to 0.03 to 0.05 individuals per hectare. In fields and
orchards where ploughing is not so deep, the number could increase up
to two to three individuals, and finally, on virgin parts, it reaches about
eight individuals per hectare (Reshetnik, 1941). The autumn migration of
mole rats from between the belts into the afforested plantations is due, in
the opinion of V. I. Abelentsev (1951), to the great degree of soil freezing
in the fields. In the area between belts this happens up to a depth of 70 cm
and only up to 10 cm in the belts themselves. It should be noted that mole
rats inhabit field protecting forest belts from the moment of their planting,
destroying the germinating seeds, shoots, and roots, especially at places
where these belts are cultivated on a badly prepared hard soil. Where soil
is ploughed deeply before cultivation, these animals vanish for two to three
years. The habitation begins because of the hardening of the soil layer and
is accompanied by an intensively damaged root system of trees and shrubs
of many types.

In places very similar to those of the Podolsk mole rat, on the territory

85

of Soviet Bukovina, the Bukovin mole rat—S. graecus—also lives (whose
way of life has not been studied in the territory nearer to Rumania).
According to E. I. Yangolenko (1959, 1965), it lives on virgin land portions,
boundary strips, roadsides (dirt roads), pastures, orchards, sugar cane
plantations, potato fields, stands of perennial grasses, and kitchen gardens.
Seasonal variations are observed in the distribution of this species accord-
ing to biotopes. The habitation of this mole rat in winter and early spring
is in virgin land, low land, and in stands of perennial grasses. Where there
is well-developed grass, habitation is denser. Because of the cultivation
of virgin lands, and the accompanying difficulties in obtaining food, it
migrates to fields and orchards. It is usually found in the field protective
belts of forests and at the edge of forests. It rarely penetrates deep into
forests. The numbers vary depending upon the character of the plantations,
climatic conditions, abundance of food, and human cultivation operations.
On the average, it comes to one to three individuals per hectare on culti-
vated lands, but on virgin lands and stands of perennial grasses, the
number reaches up to twenty individuals per hectare.

Burrows. Differing from burrowing rodents whose burrows are either
only hideouts or stores for food, mole rats, being very specialized earth
diggers, are characterized by absolutely exclusive underground feeding.
Because of this, the construction of their burrows is very complicated
with prolonged feeding entrances built by the animals under the surface
of the soil at a comparatively shallow depth. The construction of the
burrows is very different. It depends upon many factors, the type (species)
of animal, sex and age, duration of use, time of the year, plane of the site,
soil character, level of subsoil water, and abundance of food.

The peculiarities of the construction of burrows are far from completely
studied. At present, no data is available on the construction of the burrows
of the Ehrenberg mole rat. Very scanty information on this subject is
available on the mole rat of Nehring. According to V. A. Pkhakadze
(1940), it is only known that on hilly meadows and pastures, the depth of
burrows reaches up to 80 to 150 cm, and in fields of fallow soil, it is not
more than 100 cm. In the hills of northern Iraq, Reed (1958) found burrows
of mole rats of this type, 75 cm deep. The general length and features of
the construction of food inlets have not been studied. The last mentioned
are usually at a depth of 5 to 40 cm and have a diameter of 6 to 7 cm. In
each burrow, there are one or two nest-like rooms, the dimensions of
which vary somewhere between 20 by 20 or 25 by 12 cm. The nest-like
rooms are abundantly filled with dry vegetation. Besides these nest-like
rooms, the burrows of mole rats contain storerooms, the number and
construction of which is not clear for the given species. As has been said
already in the previous sections, mole rats throw dug up earth on the |
surface during the burrowing process, through comparatively narrow,

86

slanting, or vertical burrows away from the food entries and their branches.
The thrown-up earth accumulates near the outlets of the burrows in the
form of small mounds—the dimensions and position of which, in my
opinion, are important from a species specification point of view, and
which, unfortunately, have not been satisfactorily studied for present-day
mole rats. According to A. R. Pogosyan (1946), the density of the heap
of earth thrown by the mole rat Nehring may reach 13 on 19 М>, and
their dimensions fall within the following ranges: height, 12 to 26 cm;
width, 25 to 120 cm; and length, 26 to 158 cm. Usually the mounds of
earth are of 12 to 20 cm in height, 26 to 64 cm in length, and 25 to 63 cm
in width. The distance between them may range from 25 to 700 cm, but
is most often 83 to 154 cm. No regularities were observed in the disposi-
tions of these heaps. In some instances they were arranged in a line and
sometimes were scattered all over (on three to four places and in different
spaces). According to V. A. Pkhakadze (1940), the nest-like rooms in the
majority of cases are under the largest mound.

Information on the construction of burrows by white-toothed mole
rats is very scanty. According to Yu. У. Averin ef al. (1962), the burrows
of this species consist of slanting entrances (the burrow itself) and hori-
zontal feeding galleries. The galleries are situated at a depth of 5 to 30 cm
and have a diameter of 6 to 9cm. Their total length may exceed 65 to
100 m. At about each 45th m from the feeding entrance, there are three
to four stores. The depth of the burrows is about 17 by 20 cm. The height
is approximately 20 cm (Reshetnik, 1941). It throws the earth in heaps
having a diameter of 20 to 25cm and a height of 25 to 30cm. In the
opinion of Averin ef al. (1962), the position of the heap approximately
corresponds to the common direction of the feeding entrance. As new
feeding entrances are constructed, the older ones become obstructed by
earth. After some time, the animals leave even their nest-like rooms and
dig new ones. The presence of old, grown grass on the thrown up earth is
perhaps an indication that the burrow has been abandoned.

The construction of burrows of the common mole rat has been studied
in detail (Figure 30, Dukel’skaya, 1932; Reshetnik, 1941). The system of
entrances for each burrow of a grown mole rat consists of superficial hori-
zontal feeding alleys and deeper entrances joining the living spaces, storing
spaces, and “‘latrine’’ (not more than 10 to 15 cm of the burrowed branch,
closed with an earthen stopper and filled with excretion). The diameter
of the entrance depends upon the age of the animal (5 to 7 cm for young,
and 8 to 12 for old). The horizontal feeding alleys are zigzag and at a
depth of 10 to 25 cm. Their total length usually varies from 170 to 250 m.
In some instances there are burrows with a total length of feeding alleys
exceeding 350 m. There are vertical entrances from the feeding galleries
to the nest-like rooms, storerooms, and such deeper parts of the burrow,

87

which reach а depth of 120 to 320 cm. Each burrow has at least two vertical
entrances ; sometimes this number reaches four. From the vertical entrances
start, in turn, a number of deep galleries joining the nest-like room and
storehouse. There are one or two nest-like rooms. Their dimensions fall
within the following ranges: length, 25 to 30 cm; width, 18 to 20 cm; and
height, 15 to 18 cm. In one room the remains of food and fresh bedding
are usually found, and in the other, the decaying remains of the latter. In

—

Depth,in т

В

Figure 30. Scheme of a burrow of the common mole rat (by Ognev, 1947).

A—cross section; B—plan.

the opinion of N. M. Dukel’skaya (1932), mole rats use only one nest
room and when it becomes dirty and infested by parasites, they dig a new
one. The bedding in the nest room consists mainly of cereal plants. It is
made of mainly meadow grass with interspersed Koelaria, brome grass
(Bromus sp.), wheat, sheeps fescue (Festuca sp.), and hair-like bentgrass
(Agrostis sp.). The number of storerooms varies from four to nine. They
are situated at a depth of 17 to 160 cm (Ognev, 1947). The shape and
dimensions of the mounds of earth thrown out by the common mole rat

88

vary. The base of the freshly thrown out hillock is round. The mounds
are formed of separate layers of earth and, moreover, some of them even
preserve a cyclindrical form, the diameter of which corresponds to that
of the entrance leading to the exit hold out of which the earth is thrown.
Through drying and atmospheric showers, the mounds become flattened
hillocks. The size of individual mounds varies from 20 by 20 cm to 230 by
240 cm. Mounds of 50 to 60cm in diameter are most frequent. Small
mounds are thrown out in one stroke; larger ones undergo many changes
during their formation and are the result of fusion of many small mounds;
to fill the intervening space, earth is thrown out for quite a long period.
Thus, as observed by N. M. Dukel’skaya, a complex mound was formed
in 39 days. The distance between the mounds was 20 to 1,175 cm (more
frequently 100 to 200 cm). The majority of the mounds are concentrated
in the area of food entrances. The deeper entrances usually have no
external peculiarities; however, in some cases, large mounds of earth have
been noticed near the nest-like rooms indicating the disposition of vertical
entrances. The thrown-out earth is not situated near the main food
entrance. The dug out earth is transported through branches of the bur-
rows, the length of which could reach up to 75 cm and which end by an
exit hole. The main portion of the pushed-out soil comes out through
this. Hence, the direction of the disposition of mounds does not correspond
to the same for the food entrance. N. M. Dukel’skaya (1932) divides the
burrows of common mole rats into the following four groups depending
upon the locations of the thrown-out mounds.

1. The mounds are placed straight along with one or two short
branches. The general prolongation of the area of thrown-out earth is
varied. In individual cases the distance between the two extreme points of
thrown-out earth may be up to 169 m and the number of mounds, 114.

2. The mounds are situated radially in relation to one or two centers.
In this case, some individual large burrows may account for 90 mounds
and the maximum distance between the two extreme points of thrown-out
earth may be about 250 m.

3. The mounds are positioned irregularly. In such a situation, one
burrow may account for more than 100 throw-outs in an area of 100
square meters.

4. A portion of the mounds is placed straight and there are groups of
irregularly placed points of thrown earth. Burrows of this type occupy a
maximum area. For example, a mole rat released on an experimental area
dug out 284 mounds of earth on an area of about 61 hectares during a
period of four months (May 9 to September 12).

In Dukel’skaya’s opinion (1932), burrows of young mole rats differ
considerably at first sight from those of aged ones. Thus, mole rats which
have only just started their independent life, throw out small mounds of

89

earth (diameter, 10 to 30 ст), situated оп a close but haphazard path.
Only in the region of the nest-like room are there one to two large mounds
(40 to 50 cm in diameter). The feeding entrance of the burrow is located at
a depth of 10 to 16 cm and gradually passes into deeper parts, ending in a
depth of 50 to 75 cm. The nest-like place is situate at a depth of 20 to
30 cm and by it the burrow-branch communicates with the food entrance.
However, burrows of such types have also been observed for aged animals
which have recently transferred themselves. The difference lies only in the
dimensions of the thrown-out mounds and in the diameter of the entrance.
As a result, both the young and aged build burrows of the same type. The
burrowing activity of the animal is not always accompanied by an exca-
vation of earth from the burrows because a portion of the soil is used for
closing old entrances with earth stoppers. During the excavation of burrows
made by the common mole rat, a considerable number of old surface
entrances filled with various roots, very rarely occurring in external exca-
vations, were observed. The appearance of abandoned food entrances
begins from the end of spring. Thus, according to Dukel’skaya (1932) all
food entrances are still joined with each other in the spring. Starting from
the latter half of May, the earth stoppers begin to appear isolating indivi-
dual portions of the entrances. The number of abandoned food entrances
increases in the summer months.

The temperature of burrows varies at small intervals depending upon
the depth of the burrow and the temperature on the soil surface. According
to L. B. Beme (cited by Ognev, 1947) the temperature of the food entrance
of the mole rat in June and July varied within 5°C (23.5 to 28.7°), whereas
on the soil surface, the difference of temperature was 14°C (23 to 37°).

The construction of burrows by the Podolsk mole rat is similar in
principle to that of the common mole rat. However, V. I. Abelentsev
(1951) indicates that the length of the burrow-branches of food entrances
leading to the hole through which earth is thrown out, does not exceed
25 cm in this species, under conditions of the right bank steppes of the
Ukraine SSR. Hence, the earth mounds thrown out by the Podolsk mole
rat are usually situated at a distance of 10 to 25 cm from the main food
entrance. The form of the food entrances is quite varied, as in the case of
the common mole rat. Straight or slanting galleries are found often, but
rarely in the form of radial lines and least of all, circular. The general
length of food entrances is in the range of 10 to 275 m, the depth is 13 to
21 cm, and the diameter is 6 to 7 cm for the young, but 8 to 12 cm for the
mature. The depth of the vertical entrances leading to the nest-like rooms,
storerooms, and the “Чате” is 90 to 275cm. The number of vertical
entrances varies from two to six; the nest-like rooms are one to two; and
storerooms, three to five. The nest-like rooms are situated at a depth of
90 to 275 cm and have a diameter of 25 to 30 см. The storerooms have

90

the same measurements. Sometimes, the nest-like rooms and the store-
rooms are joined by burrow branches with a circular, deep gallery which,
in turn, communicates with the vertical entrances. The number of exca-
vated mounds of soil from one burrow varies from 6 to 217. The distance
between them is from 20 to 1,175 cm. The diameter of the external exca-
vations is 30 to 67 cm, and the height is 10 to 23 cm.

No detailed description of the burrows of the Bukovin mole rat has
been given in literature. On the basis of available data (Yangolenko, 1959,
1965), it can be assumed that their burrows are similar to those of the
Podolsk mole rat.

The burrows of giant and sandy mole rats also have much in common
in their construction with the burrows of the Podolsk mole rat. However,
in living places related to sandy soils, the food entrances are usually
situated at a greater depth of 40 to 50cm in the lower Dnieper sandy
arena, due to the humidity and the resultant texture of the soil as well as
the temperature threshold which, for the given species, should not exceed
27°C. The giant mole rat also constructs similar feeding entrances
on similar depth (Anisimov, 1938). Furthermore, the depth of the ver-
tical entrances built by the sandy mole rat usually slightly exceeds 100 cm
which, most probably, is due to an excess of humidity at great
depths, related to a considerably high level of subsoil water. In the giant
mole rat, the depth of the burrow could reach three meters, and more. The
position of the excavated mounds of earth, in relation to the main food
entry for sandy mole rats, is similar to that of the Podolsk mole rat as
the length of burrow-branches, through which the transportation of earth
to the exit hole takes place, usually does not exceed 25 cm. This branch of
the burrow is inclined in relation to the food entrance at an angle of about
45° in the majority of cases. The dimensions of the externally excavated
earth by sandy mole rats, for example, corresponds to that of the Podolsk
mole rat; the giant mole rat’s exceeds that of the sandy mole rat (diameter
of excavated mounds, 40 to 275 cm; height, 25 to 75 cm).

Food. The basic food of mole rats consists of roots, tubers, and rhi-
zomes of varied vegetation. While constructing the feeding channels, the
animals chew the underground portion of vegetation, preferring them to
succulent foods. The superficial green parts of vegetation—stems and
leaves—are significant in the food of mole rats. They obtain the leaves
without coming out of the feeding tunnels, reaching through their upper
walls. The animals chew the filaments of the roots and by loosening the
soil near the roots, pull the whole plant into the entrance. The vegetation
for bedding in the nest-like rooms is obtained in the same way.

The food for different species of mole rats has been irregularly studied.
Information on this point is extremely scanty for the Ehrenberg mole rat.
The diet of the Nehring mole rat in Caucasia has been completely studied.

91

The main food for this species in hilly meadows consists of onions, tulips,
star of Bethlehem (Ornithogalum umbellatum) and fritillary (Fritillaria sp.)
(Satunin, 1920). In the storeroom of the Nehring mole rat (experiments
were conducted on the territory at Akhalikalakskii and Stalkinskii regions
in Georgia, USSR), the following vegetations were found; geranium
(Cranesbill), turnip-rooted chervil (Chaerophyllum bulbosum), carrot,
gladiolus, star of Bethlehem, grass peavine (L. sativus), rampion (Campa-
nulla rapunculus), sedge (Carex gracilis), wheat grass, salsify (Tragopogon
sp.) sheep fescue, creeping clover, cummin (Trachyspermum corticum),
and onion. The storing of food for winter goes on in the summer months.
The quantity of store considerably increases toward spring. If in August
the quantity of edible vegetation in the store was 130 g, then toward
November it increases up to 600 g.

The food of the western forms of the European white-toothed mole
rat has not been studied. In the Moldavian and Odessa regions, 25 types
of vegetation were found as the food of this species, of which the majority
were grains (Averin et al., 1962). The stores consisted mainly of root and,
in less quantity, the parts of vegetation above ground. However acorn,
maize, grains, and pulses were also found. Of grasses, the following are
particularly popular: dandelion, forget-me-not (Myosotis sp.), chicory
(Cichorium sp.), clover, lucerne, different types of melilot (Melitotus sp.),
garden burnet (Salod burnet), sedge (Carex gracilis), bindweed (Glorybond),
different types of sow thistle (Sonchus sp.), wormwood, vetch (Vicia sp.)
wild garlic, and feather grass (Stipa sp.). On cultivated sands and field-
protecting forest plantations, the white-toothed mole rat’s activity de-
stroyed orchard crops and forest plantations. Thus, in the store of these
animals, considerable quantities (sometimes more than ten kilograms) of
potatoes, sugarcane, carrots, onions, garlic, and even the roots of oak
seedlings were found. Sometimes, insects can be found in burrows in the
fields.

In the region of Chernovitskii in the Ukraine SSR, the basic compo-
nents of food for white-toothed mole rats are as follows, according to
data presented by Yangolenko (1965): dropwort (Filipendule hexapetala),
groundnut, peavine (L. cicera), comfrey, cow parsnip (Heracleum sp.),
field snow thistle (S. arvensis), gray thistle, clover, lucerne, chicory, dan-
delion, and salsify. In the autumn-winter period, they feed on crops like
sugar cane, carrot and melons in addition to wild vegetation. It has also
been observed that vegetation like the families of thistle and pulses pre-
dominate in the food of mole rats of Soviet Bukovina in spring, and in the
autumn, bulbous vegetation (gladiolus, onion, garlic) predominates. The
daily food requirement of this animal usually exceeds that of its body
weight. The weight of the stomach with contents is 18 g, on an average.
Information on the duration of storage of food and its quantity in general

92

is scanty. The total weight of stores may reach up to 14 kg (Yangolenko,
1965).

Very scanty information is available on the diet of the giant and sandy
mole rats. It can only be assumed that in the food of the sandy mole rat
the vegetation generally available in abundance in the habitat of this
species would predominate. The list of this vegetation has been given
above (page 82); salsify (Tragopogon sp.) is liked best,* the roots of which
are abundantly found in the store of this animal (Reshetnik, 1941).

The most complete information on feeding habits is given for common
mole rats. Thus, Dukel’skaya (1932) obtained, as a result of digging up
burrows of this species in the Saratov region, abundant tubers of dropwort,
gladiolus, onions, roots, leaves and stems of gladiolus and sedge (Carex
gracilis), leaves and stems of alpine clover, buttercup (crowfoot, Ranunclus
sp.) and wild forget-me-nots, and leaves of Autumn milk gowan (Leontogon
sp.). Of the foregoing, the dropwort predominates. Full grown acorns
sometimes in great quantities have been found in burrows closely situated
to forests. Thus, from one burrow dug up in May, out of 916 g of total
stores of the common mole rat, 613 g were acorns of oak. E. G. Reshetnik
(1941) puts forward the following list of edible vegetation, found during
the digging of burrows of the common mole rat of the left bank steppes
and the forest steppes of the Ukraine SSR: lilac sage (Salvia verticilata),
salsify (Tragopogon sp.), goats beard, common chicory, gladiolus, ground-
nut peavine, dropwort, knapweed (Centaurea), carrot eryngo (Eryngium
sp.), turnip-rooted chervil (Chaerophyllum bulbosum), annual everlasting
(Xeranthemum annum), sneakweed (Scorzonera sp.), yarrow (Archilles sp.),
locorice (Glycyrrihiza sp.), wheat grass, Jerusalem sage (Phlomis sp.), birth-
wort (Corydalis sp.), tulip, saffron (Crocus sativus), sedge (Carex gracites),
and clover. In the afforested zones and in the zones of field-protecting
forest belts and orchard forest plantations, the roots of trees from the
pine family and also germinating acorns were likewise found. Thus,
according to Silant’ev (cited by Ognev, 1947) in the stores of the common
mole rat, living in the territory of the Veliko-Anadolskii forestations of
the Donets region, the roots of seedlings and to a lesser extent, acorns
were found. In the ark plantations around the city of Kharkov, roots of
young mulberry trees (Morus sp.), seedlings of the oaks and white acacia
were found during the digging up of burrows (Reshetnik, 1941). Of
orchard crops, the most frequently found are potatoes, carrots, and sugar-
cane. Maize, onion, beans, and cucumbers were found rather rarely. The
total weight of the stored vegetable mass varied from 8 to 14kg. The
distribution of these stores in storerooms was irregular. The general quan-

*Giant mole rats in captivity readily eat clover, lucerne, various cereals, radish,
onion, and potato (Anisimov, 1938). According to S. I. Ognev (1947), lucerne is pre-
ferred by them and this is confirmed by his field observations.

93

tity of food increased with the depth at which the storeroom was situated.
The storing of food took place mainly in the summer months and in early
autumn. In addition to vegetable remains, some insects were also found
when the stomach contents were studied. Finally, though rarely, some
bones and wool of mouse-like rodents and the wool of their own bodies
were likewise found (Barbash-Nikiforov, 1928; Reshetnik, 1941).

The food of the Podolsk mole rat has been least studied. All that is
known is that in the right bank steppes of the Ukraine SSR (Nikolaev
and potentially the Dnieper-Petrov regions) in the burrows roots of
lucerne in abundance, and to a lesser extent the roots of wild chicory,
bindweed (glorybind) and mallow (Malva sp.) were found close to the
protecting belts, roots of trees of the pine family, oak, honey locust
(Gleditschia sp.), white and yellow acacia, and elm (E/mus sp.) were found.
According to V. I. Abelentsev (1951), the mole rat loves to eat roots of
young creepers and stems of trees and shrubs in winter. In the field-protec-
ting belts where burrows have been located, dried seedlings were usually
found along with roots chewed up by the animals.

The species composition of the vegetation eaten by the Bukovin mole
rat is quite similar to that of the white-toothed mole rat living in the region
of Chernovitskii, Ukraine SSR. These first of all are the different species
of the family Leguminosae, Compositae, Umbelliferae, Labiatae, and
Rosaceae. Some seasonal changes in composition of food are observed
in this species as in the white-toothed mole rat of the Soviet Bukovina.
The quantity of stored food varies considerably. According to E. I. Yango-
lenko (1965), 0.5 to 6 kg of different vegetation was found in the stores of
the Bukovin mole rat on haying fields; on the best fields, from 1 to 12 kg
of tubers, and on stands of perennial grass, up to 4 kg of wild vegetation.
The daily food consumption of the animal exceeded its own weight, and
the weight of acorns in it was, on an average, 25 g.

Reproduction. Information on the reproduction of mole rats is very
scanty and questionable. The mole rats of Ehrenberg and Nehring have
been least studied in this aspect. It is only known at present that under
conditions of the Soviet Caucasus, the mole rat Nehring perhaps repro-
duces once in a year and moreover, the litter consists of not more than
two offspring (Pkhakadze, 1940). No data on the time of mating, sex ratio,
ovulation and spermato-genesis, sexual maturity, nutrition, and colon-
ization of the young is available.

Rather complete information on reproduction is available on the
white-toothed mole rat. Moreover, the Bukovin populations have been
studied better than the Moldavian and Black Sea region ones in the
Ukraine. There is no data on the reproduction of the Balkanski subtype.
According to E. I. Yangolenko (1965), the weight of the testis and, corres-
pondingly, the diameter of the seminiferous tubules, is largest in February

94

and March in white-toothed mole rats. At the same time, the weight,
length, and the width of the ovaries increased, but the maximum length
and breadth of the uterine horns were observed in March and April. All
this indicates one ovulation in a year. The females mature when they are
two years old. One female has, on an average, 3.15 embryos. There are
only immature follicles in the first year of life in the ovarian stroma.
Copulation takes place in the burrows, from the tenth day of January,
perhaps, to March. The young are born till first half of April. The migra-
tion and colonization of young animals begins in May. The lactation
period does not exceed three weeks. Animals of 85 g of weight and a length
of 10cm can feed independently on grassy vegetation. The sex ratio is
about 1 : 1.

The Bukovin white-toothed mole rat populations and populations of
the Moldavian and Black Sea regions of the Ukraine of the same species
differ; literature gives information about two litters in one year—in the
spring (March to April) and in the autumn (November). This was first
observed by Nordmann (1840) and has been confirmed subsequently by
many authors. Moreover Yu. У. Averin et al. (1962) has reconfirmed the
presence of a spring generation of this species lately. It is quite possible
that some of the spring births correspond to the warmest season and a
prolonged vegetation cover. The number of offspring in a litter is two to
four, usually three. In some instances, this number has reached to six to
eight (Reshetnik, 1941). The lactation period, colonization, and maturity
of the young are similar, perhaps, to the same traits seen in the Bukovin
white-toothed mole rat. The young leaves the maternal burrow when they
are two months old and dig their own burrows.

There is no information on the reproduction of the giant, sandy, and
Podolsk mole rats. There is information only on the colonization by the
young of the sandy mole rat in March (Reshetnik, 1941).

Information on the reproduction of the common mole rat is extremely
scanty. According to Dukel’skaya (1932), of eleven females of this species
obtained in April from the Petrovski region of Stavropol district not one
was found to be pregnant. In only four of them were the teats and milk
glands developed. This, perhaps, denotes the end of lactation. Of fifteen
females caught by Е. G. Reshetnik (1941) in the ВагушКоу region of the
Kharkov district in the first half of April, seven were lactating. Four of
them were caught along with their young ones. All this apparently points
to the appearance of the young in March and to the end of lactation by
the end of May. In May and in the beginning of the year, they colonize
intensively (Dukel’skaya, 1932; Reshetnik, 1941). Very similar periods of
reproduction for the common mole rat living in a valley portion of the
Western Cis-Caucasus have been observed by K. G. Rossikov (1887).
However, in the foothills, Rossikov caught a pregnant female in the

95

beginning of June. According to Ognev (1947) this fact possibly confirms
the delay in periods of reproduction in the foothills of the Western Cis-
Caucasus. The majority of researchers are inclined to say that the common
mole rat reproduces once a year and has two to six offspring in a litter.

The characteristics of reproduction have been studied in great detail
in Bukovin mole rats. They are in many respects similar to those of the
white-toothed Soviet Bukovin mole rat. However, unlike the latter, the
mating time in the Bukovin mole rat is prolonged into the second week of
January and, as a result, the whole cycle of development of the offspring
occurs later correspondingly. Furthermore, compared to the white-toothed
mole rat of Soviet Bukovin this species is less fertile. One female has, on
an average, 2.75 embryos. The number of offspring in a brood varies from
two to five (Yangolenko, 1965).

Mode of life. Mole rats are characterized by year-round activity. They
do not hibernate during the winter. However, because the ground freezes
during winter, they move into the deeper parts of the burrow. A marked
decrease in digging activity is observed during the winter months. Thus
E. G. Reshetnik (1941) saw in January only rare fresh mounds of earth
thrown out during the period of freezing temperatures and thawing
(experiments were conducted on the territory of Lozovskii, Bliznyukovskii
and Barvinskii regions of the Kharkov district of Ukraine SSR). Besides,
some individuals of the same species were obtained on the surface in
February. Under greatly frozen temperatures, the digging activity is, per-
haps, completely stopped. A winter migration is usual for some species
of mole rats. Thus, in the autumn-winter period, the Podolsk mole rat
concentrates itself in the forest belts where the earth freezes to a lesser
depth than in open fields. The migration of animals to open spaces takes
place in the spring (Abelentsev, 1951).

Excavating activity sharply increases in the spring months, reaching
its maximum in the second half of March, April, and the first half of May.
For example, the number of excavations by common mole rats varies from
two to three to fifteen to eighteen per day in this period. A decline in dig-
ging is observed during the summer months which, on one hand, is due
to an increase in food as a result of increased roots in vegetation, and,
on the other hand, to the warming up of the ground (Reshetnik, 1941).

Because of its underground way of life, the daily activity of the mole
rat has not been studied sufficiently. Data available in literature are almost
exclusively obtained as a result of observations on hourly throw-outs of
earth per day, and do not give a complete picture of the digging activity,
or all the intelligent actions of the animals in the burrow and food entrance;
this is not always accompanied by an outpushing of earth on to the surface.
The existing controversy about this question can be explained to some
extent. Thus, for example, according to data by Vasarhelyi (cited by

96

Hamar, Suteu and Sutova, 1964), mole rats are active only during the
day; according to S. I. Ognev (1947) they are active in the evening hours,
night, and morning hours; and finally, according to N. M. Dukel’skaya
(1932) and E. G. Reshetnik (1941) they are active around the clock. The
most significant data on the daily activity of mole rats were obtained by
Hamar et al. (1964), for the white-toothed mole rat by labeling them
with ®°Co. It has been proven that the white-toothed mole rat of Rumania
is characterized by a round-the-clock multiphased and arhythmic daily
activity. The number of phases of activity during twenty-four hours varied
from two to ten depending upon the season. In the autumn months the
activity of the animals is perhaps less than in the spring-summer period.
Thus the number of phases of activity for the marked experimental animals
extended from two to five in September, whereas for marked animals in the
spring-summer months, it reached seven to ten. The duration of each
phase of activity may vary from fifteen minutes to 3.5 hours. The maximum
duration of activity varied from 23.8 to 47.9 % of the time of the day. The
interval of time between phases was not the same. The number of move-
ments in the burrow may reach 554 during the day, and the total distance
traveled, say, about 1.5 km. The food entrances are not used regularly
during this. There are regions liked by them in the burrows, and their
number varies from one to four. The rate of construction of feeding alleys
under conditions of firm soil is about one meter per 24 hours. Mole rats
maintain their feeding entrances and burrows in a typically standard
pattern, and when the slightest destruction occurs, they immediately
repair it.

Each mole rat has his individual territory which, unless a great necessity
compels it to abandon it, he attempts to hold. Usually one animal lives in a
burrow. Females feeding the young are the only exception. A transgression
of the burrow by any animal other than the owner is a rare phenomenon
because the mole rat jealously guards its burrow and food entrances from
unwanted intruders, and depending upon the circumstances, even chases
them out. The time of mating, when males find the burrows of females and
enter, is an exception. The young live with the mother only during the
period of lactation, and at its end they leave the maternal burrow and
move to some free territory where they dig their own burrows. The time
of migration of the young has been given above. In addition to seasonal
migrations and migrations of the young, the mole rat may sometimes leave
its burrow. This happens when the burrows are affected by intensive field
operations and particularly when deep ploughing destroys the feeding
entrances of the animal.

Foes, parasites and epidemiological significance. Due to their under-
ground way of life, the enemies of mole rats among vertebrates are not
many. Sometimes the animals fall prey to wild birds when they go out of

97

their burrows. The young ones migrating from the maternal burrows
usually die like this. The owl, hen carrier (Cirus cyaneus), desert eagle,
and black kite (Milvus migrans) are some of their avian enemies. The dead-
liest predators are the desert and black polecats (Putorius eversmannii).
Mole rats are sometimes sought by other carnivorous animals like foxes,
weasels (Mustelidae) and cats. According to Abelentsev (1951) the above-
mentioned species and species of marten (Mustela) particularly hunt in the
autumn and winter months for mole rats, entering their underground
abode. Thus, as observed by the above-mentioned author, of the 157 burrows
of Podolsk mole rat investigated in the autumn period, on the right bank
steppes of the Ukraine SSR (Nikolaev and part of the Dneperpetrovsk
region), 68 had been opened by polecats. Of the 276 winter burrows of
mole rats investigated, 102 had footprints of these carnivores around the
mounds.

Of the ecto-parasites on mole rats, fleas of the genus Ctenophthalmus
—C. caucasica Tasch. and C. spalacis Jord. and Roth.—are found abun-
dantly on white-toothed mole rats, C. spalacis and C. gigantospalacis
Той on common mole rats, С. gigantospalacis and С. uralospalacis Tiflov
and Usov on giant mole rats, and finally C. Jeanneli Jord. on Bukovin
mole rats. In addition to these, in the nests and on the bodies of white-
toothed mole rats of the territory of Moldavia are found fleas Cerato-
phyllum consimilis Wag. and Oropsylla ilovaiskii Wag., lice of the genus
Hoplopleura and ticks Euryparasitus emarginatus Koch, Northolespis
decoloratus Koch, Eulaelaps stabularis Koch, Haemogamasus nidi Misch.,
H. hirsutosimilis Will., Hirstionyssus macedonicus Hirst, Ixodes ricinus
Latr., Г. JaguriOl. and Dermacentor marginatus Sulz. In Moldavian SSR
the per cent ectoparasitism may be as high as 94.3% (Andreiko, 1963).

Information on the species composition of endo-parasites is very
scanty. It is only known that in some individuals of the common mole
rat, considerable numbers of nematodes in general and, to a lesser degree,
Trichiurodia are found (Reshetnik, 1941). The endo-parasitic species of the
Bukovin mole rat have been studied in somewhat greater detail. Yango-
lenko (1965) has observed Hidatigera taeniceformis Batsch, Taenia polya-
cantha Jeuck., Trichocephalus spalacis Petr. and Potech. Ganguleterakis
spalacis Kozl. and Jang. and Heligmosomum spalacis Kirsch. The Bukovin
mole rat is 100°% infected by helminths. Finally, Heligmosomum molda-
vensis Andr. and Heterakis spalacis Marcus have been observed in white-
toothed mole rats. Mature forms of tapeworms are perhaps absent
in mole rats. However, they are either hosts or intermediate hosts for
nematodes. |

The epidemiological significance of mole rats has not been sufficiently
studied. It has been suggested that they could be the carriers of the infec-
tious rabbit fever.

u

98

Significance of mole rats for man. Мое rats happen to be serious
destroyers of field and orchard crops, stands of perennial grasses, gardens,
grape orchards, and forest plantations. The loss caused by them to agri-
culture differs under different conditions. On virgin lands and wastelands,
the destructive activity of mole rat is very insignificant and amounts to
only the spoiling of pastures. However, the total area of such spoilt
pastures is very small according to Beme (1931) (does not exceed 0.5 to
0.7% of the entire pasture area). Under conditions of intensive cultivation
and forestation the destruction caused by mole rats is quite considerable.

Especially significant damage is caused by mole rats on the seedlings
of vegetable crops. Thus, in the Spitak and Aginsk regions of Armenian
SSR, if the mole rat Nehring is present at the rate of eight to nine indivi-
duals per hectare, the harvest of vegetables is reduced by 140 kg ona given
area (Pogosyan, 1946). Usually, 15 to 18 kg of potatoes were found in their
stores. As reported by Yu. У. Averin et al. (1962) in Moldavian SSR the
white-toothed mole rat destroys potato fields intensively. Two to three
individuals per hectare are capable of destroying 12 to 14 potato plants
daily. The destruction caused by the mole rat can reach 13 to 15% of the
whole plantation at places. Similar damage is caused by the white-toothed
mole rat to the crops of fodder beet (Beta vulgaris), and sugar beet. For
example, in some of the estates of the Sorokskii region of Moldavian SSR,
the yearly damage caused to beet plantations may reach up to 600 kg per
hectare (when there are eight individuals per hectare). The white-toothed
and Bukovin mole rats cause an average reduction in beet harvest of 19
to 21% and of potato, about 15%, in a number of places around the
Chernovitskii district in the Ukraine SSR (Yangolenko, 1965).

Considerable damage is done to the plantings of perennial grasses and
hay harvests. Besides the direct damage done to the plantations, mole rats
damage the contour of the forest land so badly that not only do they
create serious obstacles in the moving of harvesting machines, but also
even hand harvesting is made difficult because each mound thrown out
has to be individually removed. The damage done to various grasses by
the direct and indirect activity of these rodents around the Chernovitskii
district could reach up to 10% (Yangolenko, 1965). A plantation of
lucerne on 67 hectares around the right bank steppes of the Ukraine SSR
suffered a two per cent damage due to the death of plants caused by the
destruction of their root system by the Podolsk mole rat (Abelentsev,
1951). A shrub count on measured tracts around this area showed that
as a result of the activity of mole rats, the destruction amounted to four
to ten per cent in four years. In addition, the whole lucerne was covered
by numerous mounds of excavated earth which proved to be a serious
handicap in harvesting the crop because workers had to remove them by
hand, and only then start the harvesting machines.

99

Compared to vegetable crops and perennial grass stands, field crops
_ suffer less from the destructive activity of mole rats. Maize is most affected.
Thus, according to E. I. Yangolenko (1965) the losses in maize sustained
in some estates of the Chernovitskii region amount up to 10%.

Considerable damage is caused to forestation by mole rats. This damage
is considerably increased on field protecting belts and forest plantations in
parks in the territory of the southern European part of the USSR. Hence,
according to Silant’ev (cited by Ognev, 1947) roots of oak seedlings have
been predominantly found in the stores of the common mole rat living in
the territory of Veliko-Anandolskii forestation of the Donets region. V. I.
Abelentsev (1951) observed that on some estates in the Kherson region, in
forest belts planted on not very deeply ploughed soil, the Podolsk mole
rat can destroy up to 30 to 43 seedlings of different species of wood. The
destruction of the roots of the field-protecting forest belts of 15 to 30 years
standing has been observed; mole rats gave preference to basic species—
elm, oak, and acacia.

Mole rats cause damage to fruit meadows. A. F. Anisimov (1938)
also observed damage caused by the giant mole rat to the roots of
grapes.

It should also be noted that mole rats influence soil fertility by their
activity, by bringing up the lower layers of black soil to the surface. The
damaging activity of mole rats is evident also in irrigation works. Water
from irrigation canals usually penetrates the burrows of the rodent, thus
pushing it out from the irrigation mesh.

The damage mentioned above increases the need for working out
measures to fight these rodents. However, because of the peculiarities of
their way of life the use of different control measures is accompanied by
considerable difficulty. Gas as a method of destroying mole rats has not
yet been very successful. The most promising method appears to be that
of poisoned baits which cannot scare the cautious animals away. Accord-
ing to Yangolenko (1965), this method gave very good results in the Cher-
novitskii region. Zinc phosphate and sodium arsenate were used as poisons
and beets, carrots, tubers of potatoes, and some wild vegetation served
as baits. The effectiveness of these methods increased in early spring and
autumn. However, in the right bank steppes of Ukraine SSR, the baits
poisoned by zinc phosphate were not eaten by the Podolsk mole rat
(Abelentsev, 1951). The most effective method to this day remains the
mechanical catching of animals by digging up the burrows and using arc
trap No. 1 and mole traps.

Some agroclimatic methods—the foremost being that of deep plough-
ing—play a great role in checking the number of mole rats.

100

A SHORT OUTLINE OF THE GEOGRAPHICAL
DISTRIBUTION OF MOLE RATS

The family of mole rats (Spalacidae) is at present exclusively distri-
buted in the Palearctic regions, to be more exact in the region of the
Mediterranean Sea with some species extending out of this boundary
because of their living primarily in the European portion of the USSR.
The area (range of distribution) of the family includes a number of regions
in North Africa, all of Central Asia, Asia Minor, Caucasia, all of south-
eastern Europe from the Balkan and Pre-Balkan regions in the west, to the
Volga in the east and similarly from north Pre-Caspian to the Ural River,
and possibly other parts of the Caspian. The northern boundary of the
distribution of the groups reaches the northern Volga region, central
regions of the European parts of the USSR, the northern parts of the
Ukraine, southwest Poland and Hungary (Figure 31). The zone of distri-
bution lies mainly in desert parts, semi-arid areas, steppes, parts of forest
steppes, and a part of the forest zones. However, in the areas around the
forest steppes and forest zones, mole rats have a tendency to come out
into open areas.

The distribution of mole rats in the past almost completely coincides
with the zones of their present distribution, extending out of these boun-
daries only in the Far East and Northwest. This is particularly so of the
most recently extinct representatives of the species of ancient mole rats
whose remains are abundantly found in the sediments of the superficial
Pliocene of Prikarpate in Poland and Czechoslovakia.

The territory of distribution of Spalacidae at present and in the past is
the ancient Mediterranean Sea, the region which was an area of intensive
hill formation—the so-called Alpine Orogenetic phase—in the time of
neogenesis which caused a permanent change in the contours of the ancient
sea basins like the Sarmatian, Miocean, and Pontiac seas preceding the
Mediterranean Sea into the present Black, Azov, and Caspian seas. The
permanent change in the contour of these basins is related, perhaps, to
those distinct factors which mainly pre-decided the distribution (including
colonization) of various groups of mole rats in the past, and the basic
regulation of its present-day distribution (in the areas of the family). Thus,
the clarification of basic regulations for the origin of the fauna of mole
rats in various regions of the Mediterranean Sea and the areas around it,
and changes in these due to times and genetical relationships, should be
based firstly on a clear understanding about the distribution of different
groups of mole rats in the past geological periods in the history of the
earth, together with an idea of all the intricate peculiarities of the paleo-
geographical state within these territories, all of which happen to be arenas
of evolution for the group as a whole. A study of the fossil and present-day

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101

of subfamilies of Spalacidae.

Figure 31. Distribution

I—Spalacinae; 2—Prospalacinae.

102

fauna of mole rats in this aspect allows one to discover certain features in
the distribution of the subfamilies, genera, subgenera, and individual
species of these rodents, and we are taking the liberty of explaining these
in detail below.

The subfamily of the ancient mole rats (Prospalacinae) succeeding the
most primitive representatives of the family, ancestoral (in relation to the
contemporary mole rat Spalacinae), and completely extinct by the end of
the Pliocene epoch, is known at present by only the very latest forms. Their
remains are restricted mainly to the middle and lower strata of the Late
Pliocene northwest of the Black Sea region, and combined territories of
Rumania as well as Hungary, Czechoslovakia, and south of Poland. It
can be presumed that this group of mole rats was widely represented in
the Late Oligocene, Miocene, and Early Pliocene of Europe, perhaps also
North Africa. With regard to the already known representatives of ancient
mole rats, these existed in the Middle and Late Pliocene of Europe with
more highly specialized true mole rats of the Middle Pliocenic European
species of the Nominal subgenera of the genus Microspalax. Around the ©
northeastern Black Sea region of the USSR and combined territories of
Rumania, the zones of distribution of ancient and contemporary mole rats
are identical. This is proven by the finds of remains of both types in the
Central Pliocenic Kuchurgan deposits (found in the valley of the Kuchur-
gan River, Odessa region) and contemporary strata in territories of Ruma-
nia (the place of the find was Malushteni, right bank of the Pruta River
on its lower current). However, the frequency of finds of both remains
under similar conditions is extremely rare when compared to the same
for present-day mole rats.

Among the Late Pliocene fauna of North Rumania, Hungary, Czecho-
slovakia, and southern Poland, Spalacidae is represented only by a group
of ancient mole rats. The absence of true mole rats here perhaps led to the
frequent occurrence and subsequent discovery of abundant remains of
Prospalacinae as compared to the contemporary sediments of the north-
western Black and Azov Sea areas. The preservation of most of the later
representatives of ancient mole rats in the given area can be explained
most likely, first of all, by paleogeographic factors. Foremost among such
factors are perhaps the distinct influence of the Pannonski Basin and
intensive organic processes in the raised region of Karpatiya and Tatranskii
existing almost throughout neogenesis. As a result, in the Late Miocene
period and throughout the Pliocene epoch, i.e., during the time of intensive
sedimentation and settling of the true mole rats in the northwest Black Sea
and Azoy Sea regions, the old mole rats living in the region of Tatranskii
and Karpatiya could have been isolated because of real insurmountable
obstacles. All this facilitated the preservation of a number of Miocenic
relics in the Pliocene fauna of the given region to a great degree. In addition

103

to ancient mole rats, perhaps И is better to add ancient wrinkle-toothed
hamsters (Cricetus cricetus) from the genus Trilophomys Deperet, Bara-
nomys Kormos and others, and the primitives (Ungaromys Kormos and
Germanomys Heller) which are totally extinct here but have preserved their
numbers significantly up to the present in the northwest Black sea region.

In fact, the area of distribution of the subfamily of the true mole rats
almost completely corresponds to the region of distribution of the family
as a whole. Only some finds of the remains of Prospalacinae in southern
Poland and Czechoslovakia have been found outside its boundaries.

The most ancient and primitive representatives of this group of true
mole rats are the fossil and present-day species placed under the Nominal
subgenera of the genus Microspalax (Figure 32). The only living species,
M. ehrenbergi, is prevalent in the North African and Central Asian Medi-
terranean Sea area (northern regions of Libya, United Arab Republic,
Israel, Jordan, Lebanon, Syria, Iraq, and possibly the southern regions of
Turkey). However, at the end of the Miocene epoch and during almost all
of the Pliocene, this subgenus was widely spread in Europe where lived
other species like M. compositodontus (end of Late Miocene in northwest
Black Sea region, USSR), M. macoveii (first half of the Middle Pliocene
in the northwest Black Sea region of USSR and Rumania), and M. odes-
sanus (second half of the Middle and Late Pliocene in the northwest Black
and Azov sea region of USSR). It should be remembered that the subgenus
Microspalax is represented in the Middle Pliocene of Europe by species
which were already highly specialized in a greater number of traits than
even the present-day M. ehrenbergi. This fact allows one to assume a
considerably wider distribution of this subgenus during the latter part of
the neogene, and to decide that the time of separation into areas with close
proximity was the Early Pliocene.

If we consider the present-day M. ehrenbergi as relics of the Neogenic
age, and if it is proved beyond doubt that their ancestors lived within the
boundaries of their present distribution zone (based on the level of special-
ization of the species and the paleogeographical condition of the given
territory at the end of the neogene era), at least from the end of the Early
and the beginning of the Middle Pliocene, then taking into consideration
the European fossil finds, the areas of distribution of the subgenus from
the end of the Miocene epoch and during the whole of the Pliocene, in
addition to North Africa, Middle East and possibly Asia Minor, extended
to all the territory of southeast Europe situated south and east of the
Pontiac basin going westward up to Northeast Rumania. Naturally, the
contour of the area (zone of distribution) changed during different geo-
logical times in close proximity to the permanent changes in the configura-
tion of the ancient sea basins in the areas of the present Mediterranean,
Black, and Azov seas. Knowledge about the eastern boundary of the

105

distribution zone of the subgenus varies and is limited due to insufficient
studies of the Neogenic fauna of rodents in the eastern territories. The
Azov region near the Ukraine is the latest known farthest eastern point,
recently determined from the finds of remains of the Pliocene European
Microspalax.

The question of the final separation of the Afro-Asian and European
Microspalax is of considerable interest. As shown by research, the per-
manent molar teeth of the living Afro-Asian mole rats of Ehrenberg fall
in a middle category in respect to the degree of specialization, between
the molars of Miocene and certain Middle Pliocene European representa-
tives of the subgenus. Thus, it can be concluded that M. ehrenbergi repre-
sents, perhaps, a special Afro-Asian branch of the subgenus which sepa-
rated from the main stem of Microspalax. Keeping in mind that in the
Middle Pliocene of Europe there existed a species which had a number of
better developed traits than the present-day M. ehrenbergi, perhaps it
could be assumed that the final separation of the Afro-Asian and European
branches of Microspalax took place somewhere in the beginning of the
Pliocene period. Most probably the transgression of the Pontiac basin
played a specifically distinct role here. Until this, perhaps the area of the
subgenus was one as a whole; moreover, the joining of the Afro-Asian and
European zones at the end of the Miocene epoch could have taken place
only in the region of ancient Aegean land. Further, after the Pontiac
period, the dry land communication between Central Asia and Asia Minor,
and Europe in the region of the Balkan was perhaps restored; however,
the further contact of Afro-Asian and European branches of Microspalax
obstructed the appearance and colonization on the territory of Asia Minor
and the Balkan of representatives of another still highly specialized sub-
genus of the genus Microspalax (Mesospalax) which is genetically related
to the Afro-Asian branch of Microspalax.

The youngest branch of the genus Microspalax subgenus Mesospalax,
which is represented by two species, M. nehringi and M. leucodon, is perhaps
of Asia Minor-Balkan origin. The first is, at present, spread on the whole
territory of Asia Minor and partly. in Caucasia; the second, mainly around
the Balkan and Pre-Balkan regions of Eastern Europe, penetrating only
a little into Hungary, the northeastern Black Sea region, and the Karpate
(Soviet Bukovina). The fossil remains, mainly of the obgoicene age, have
been found entirely, without exception, in the region where modern species
have spread. Thus based upon the zone of distribution and morphological
peculiarities of the living representatives of the given subgenus, two bran-
ches fall within its composition—the one from Asia Minor represented
by M. nehringi, and the European represented by M. leucodon. Of the
aforementioned species, M. nehringi appears to be more primitive. In
addition, a number of characteristics in its organization point toward a

106

genetic relationship with Afro-Asian representatives of the subgenus
Microspalax.

A sharp increase in the degree of specialization is observed in M.
leucodon, steadily increasing in the subspecies toward the West. The
degree of digging adaptability in the structure of the masticatory apparatus
in mole rats of this species reaches its maximum in the farthest western
nominal subspecies, М. /. leucodon, and is expressed to a lesser degree in
M.1. monticola of the Balkan. The time of complete separation of the Asia
Minor and European branches of Mesospalax in the region of the dry
lands of the Bosphorus has not been finally decided, primarily because
of an almost complete lack of paleontological documentation. However,
considering the quite significant differences between the species indicated,
the distinctions of the zone of distribution for the subgenus in the Late
Pliocene can be assumed with a certain probability. There is absolutely
no contact between the Asia Minor and European branches of the sub-
genus Mesospalax through the Caucasus and all the Black Sea region.
This is contradicted by the already mentioned fact of the rise in the level ~
of specialization in the European subspecies of 5. Jeucodon' in eastern
direction, and the paleontological data most undisputedly says that in the
Late Pliocene deposits of the cis-Black Sea and cis-Azov parts of the
Ukraine, the ancient mole rats of the subgenus Microspalax (M. odessanus
and forms close to it) were immediately replaced by the highly specialized
representatives of the genus Spalax. All the known reference material on
the remains of М. Jeucodon in the Pliocene and Lower Anthropogene
deposits of the above-mentioned region, are based exclusively on unreliable
identifications, and the remains provisionally classified as belonging to
this species were found, on closer examination, to belong to either Pliocene
representatives of the subgenus Microspalax or to Late Pliocene—Early
Anthropogene Spalax.

If in the Balkans the mole rats of the European branch of the subgenus
Mesospalax are apparently autochtonic since the end of the Pliocene
period, then they are comparatively late arrivals in their present habitat
on the territory of the cis-Black Sea region of the USSR and possibly
adjoining regions of Rumania. The period of penetration of this group
in the territory mentioned is, most probably, approximately the end of the
Pleistocene and Early Holocene era. The latter has been fairly reliably
documented by paleontological finds in the limits of the present distri-
bution of the species on the territory of the cis-Black Sea region of the
USSR. In particular, it has already been mentioned that on the territory
of the entire northern cis-Black Sea and cis-Azov regions in the deposits
of the transitional zone between Neocene and Anthropogene, the mole

1 This should be М. /eucodon—Editor.

107

rats of the subgenus Microspalax are immediately replaced by the early
Spalax. This also relates to the region of the present distribution of M.
leucodon in the limits of the Odessa region and Moldavia. In the deposits
of the lower and middle sections of Anthropogene within the limits of the
habitat of М. leucodon in the cis-Black Sea region, one comes across
remains of representatives of the genus Spalax exclusively which are as if
identical in their species affinity to the present-day S. polonicus. Reliable
finds of remains of Mesospalax in this region relate only to the uppermost
Anthropogene strata, most possibly to the end of the Pleistocene, if, of
course, the remains of М. Jeucodon from Ilinka, Odessa region (Pidopli-
chko, 1956) are not of more recent origin. Otherwise, the distribution of
this species on the territory mentioned above should be dated to the
Holocene. Such a late penetration of М. [еисодоп in the northwest cis-
Black Sea region is explained, most likely, by the presence in the past of
the constant insurmountable barrier in the form of an aquatorium of
different types linked with the Danube and its basins. Apparently, this
species appeared to be more adaptable to the conditions of the xerophyte
steppes than the earlier mole rat inhabitants of the species S. polonicus
in this region, which undoubtedly facilitated the almost complete extinc-
tion of the latter from the region of the present distribution of М. leucodon
in the northwest cis-Black Sea region of the Soviet Union. At present the
valley of the Dunai and Tissa forms a natural boundary for the distribution
of two present-day subspecies—Nominal and Balkan.

The Late Pliocene and Anthropogene autochtones of the southern
and partly central belts of eastern Europe are mole rats of the genus
Spalax. The areas of their present and past distribution encompass regions
of the cis-Black Sea and Caspian lands from the Soviet Bukovina and
adjacent areas of Rumania in the west, to the Volga, the north Caspian
east of the Ural River, and partly the trans-Caspian in the east. The
northern boundary of the habitat of this genus passes through the ex-
treme southeast of Poland, northern regions of the Ukraine SSR, except
the extremely northern parts, adjacent areas of the Chernozem belt of
the Russian Federation to the Central Volga, roughly up to the latitude
of the Samara Luk, and moving into the recent past, into the southern
districts of the Gorkii region (Figure 33). In the Late Pliocene, the habitat
of the genus also included the Crimea. The genus is genetically! linked
with European Pliocene representatives of the subgenus Microspalax,
among which we should possibly search the basic forms of the given group.

The genus includes two groups differing sharply in morphological
features as well as in regions of their present distribution: group giganteus,
represented by the present S. giganteus and the phylogenetically close S.

1 Should be phylogenetically—Editor.

108

arenarius, and close to the latter, early Anthropogene species and the
group Microphthalmus, with three present-day (S. graecus, S. polonicus
and 5. microphthalmus), one fossil (5. minor) species. Among the foregoing
subdivisions, the most primitive group constitutes the mole rats of the
giganteus group. It consists of two clearly differentiated branches, viz.,
the western branch represented by S. arenarius and forms closely related
to it from the lower Anthropogene deposits adjoining the present habitat
of desert mole rats in the cis-Azov region of the Ukraine SSR, and the
eastern branch including present-day S. giganteus.

о, @e2 © O04 65 дб +7

Figure 33. Distribution of species of the genus Spalax.

1—S. polonicus; 2—the same, Holocene; 3—5. giganteus; 4—5. microphthalmus;
5—S. arenarius; 6—S. graecus; 7—5. minor.

The distribution of the species of the western branch is restricted now
to a small area of the lower Dnieper sand belt (left bank of the lower
Dnieper, south of Kakhovka). Fossil remains of possibly closer species
are known from the lower Anthropogene deposits of the village Tikho-
novka (near Militopol’) Zaporozh’e region, east of the present habitat of
the species. The latter evidently points to a wider distribution in the past
of mole rats of the given branch of the group giganteus. It should be noted
that although representatives of the western branch have retained in their
physiognomy various primitive features pointing to their phylogenetic
link with S. giganteus, nevertheless in the course of subsequent evolution
they have reached a considerably higher level of specialization than repre-

109

sentatives of the eastern branch, thereby approaching, in this respect, the
most highly organized species of this genus from the group microphthalmus.
This, apparently, must serve as proof of a comparatively early separation
of these branches, the roots of which pass to the end of the Pliocene era.

Of all the known mole rats of the genus Spalax, the most primitive
physiognomy has been retained by representatives of the eastern branch
of the giganteus group, i.e., the present-day giant mole rats. This species,
in its level of specialization, is much inferior even to the comparatively
primitive earliest representatives of the microphthalmus group like the
late Pliocene S. minor. This, naturally, contradicts the suggestion of a
comparatively early branching of the above-named groups of the genus
Spalax (apparently beginning with the late Pliocene) and the relict nature
of the present S. giganteus in the limits of their present-day distribution.
It is known that the habitat of giant mole rats includes two areas isolated
from each other, viz., eastern cis-Caucasus and the northern Caspian, and
partly, the trans-Caspian east of the Ural River. In the lower Volga region
and on the entire interfluve territory of the lower Volga and Ural Rivers,
this species, like other representatives of the genus, is generally not found.
Observations of V. S. Bazhanov (1930) and A. S. Stroganova (1954) on
the presence of mole rats in the region of the Smolenka village, Puga-
chevskii region, based on the verbal information of collectors from local
organizations for the procurement of wool, need additional proofs or
confirmation. Thus, the distribution of the species is confined to the
zone of stable changes in the course of the Late Pliocene and almost
the entire Anthropogene of the ancient marine basins, preceding the
present Caspian. It may be suggested that the isolating action of these
basins in the course of various sections of the Late Pliocene and
Early and Middle Anthropogene is the chief factor which, in the ultimate
analysis, predetermined the present distribution of the species. Probably,
the leading role in the separation of the western and eastern branches may
have been played by the Manych Strait (Pidoplichko, 1951), the effect of
which, as shown by the data of geologists, was apparently retained till the
Pleistocene. It may also be assumed that the division of the habitat of the
giant mole rat into two areas, observed in the present period, is, to a great
extent, stipulated by the Pleistocene Khazar and subsequent Khvalin
transgressions of the Caspian Sea. Before this, if we take into account the
data of L. A. Vardanyants (1948), both the areas were undoubtedly
linked, since in the early Quaternary period, in view of the contraction of
the Caspian basin, the entire area in the limits of the present habitat of the
giant mole rat from Dagestan to Emba was dry land.

Thus, if the eastern branch of the giganteus group, in view of the specific
nature of the paleogeographical conditions of the past, remained insigni-
ficantly changed from at least the end of the Pliocene, then the western

110

branch of this group in the course of Anthropogene evolved in the same
direction as representatives of the microphthalmus group. This greatly
facilitated the successful competition between them. Apparently, sandy
mole rats were even more adaptive to the specific conditions of the sandy
area of the lower Dnieper which greatly predetermined the conservation
of this species in the limits of this area.

As mentioned above, the microphthalmus group includes, at the present
stage of our knowledge, one fossil and three present-day species. Remains
of the Late Pliocene S. minor are found throughout the deposits of the
second half of the Upper Pliocene and partly the Lower Anthropogene
along the length and breadth of the cis-Black and cis-Azov Sea parts of the
USSR, including the Crimea, from the western state boundary in the east
right up to the Taman Peninsula. Special attention should be paid to the
fact that finds of remains of S. minor have been reported from the Crimea
which documentally prove the existence of mole rats on the peninsula in
the Late Pliocene. The latter is more interesting because in the Pleistocene
and Holocene fauna (including present-day forms) of the Crimea, mole
rats are apparently absent. The only (unfortunately unverified) mention
of the discovery of Spalax remains of the Pleistocene age here in present
times (Merezhkovskii, 1880), has not been confirmed by the research
of Byalinitskii-Birulya (1930) and Gromov (1961) conducted on the
massive paleontological material of the late Pleistocene and Holocene
eras of the Crimea. Thus, the disappearance or, at least, a considerable
reduction, in the population of mole rats in the Crimea in the course of
the Middle and Late Anthropogene, ‘should evidently be considered a
secondary phenomenon. The reason for this probably lies in the substantial
changes of paleogeographic conditions prevalent in the Crimea at the
end of the Early, and the beginning of the Middle, Anthropogene. The
causes stipulating these changes and their nature have not been explained
thoroughly even to this date. It can only be suggested that they were asso-
ciated with the intensification of tectonic disturbances in the Crimean hills,
which ultimately led to the loss of land connecting the Crimea with adjoin-
ing areas of the cis-Black Sea and the cis-Azov Sea dry land. This, in
turn, was accompanied by the emergence of new natural conditions, most
unfavorable for the existence of these rodents. Soon afterwards (possibly
at the end of the Pleistocene and Holocene) when natural conditions within
the Crimean steppes appeared conducive again, the influence of the
island’s past isolation phase continued, apparently causing the retention
of insurmountable barriers such as sea washes and edaphic factors linked
to strong salinization and the formation of solonchaks in the isthmus of
the earlier sea bottom.

In such a wiae habitat, the remains of mole rats of the group S. minor
are nevertheless practically undifferentiated, which apparently testifies to

111

their affinity to a single species. Therefore, it may be assumed that the
appearance of the present-day species grouped under microphthalmus
group was prevalent only in the Anthropogene era. Evidently, these thiee
present branches of the groups—S. graecus, S. polonicus and S. micro-
phthalmus—were already formed at the end of the Early, and the beginning
of the Middle, Anthropogene, since in the deposits of the upper strata of
the Middle Anthropogene, one finds remains of fully differentiated forms
which, from a species aspect, are possibly identical to present-day ones.

Today, the region of distribution of S. graecus encompasses a small
area of the Soviet Bukovina and the adjacent regions of Rumania; that of
S. polonicus, the extreme southeast Poland, the entire right bank portion
of the Ukraine, except the northernmost parts of its territory occupied by
5. graecus and 5. leucodon' and finally, 5. microphthalmus occupies the
entire area of the interfluve of the Dnieper and Volga (except the lower
Volga) reaching in the north up to Kiev, southern parts of the Chernigov
region, eastern parts of the Kursk and Orlov regions, southern districts
of the Tula and Tambov regions, Mordov ASSR and the UI’yanov region
(fossil Holocene remains have also been found in the southern parts of
the Gorkii region), and in the south along the Kakhovka-Azov coast to
the Krasnodar and Stavropol areas. The area of the species encompasses
mostly the steppe zone and forest steppes penetrating in strips into the
forest zone. Major factors greatly predetermining the present habitation
of mole rats of the microphthalmus group and its evolution as an inde-
pendent species are, apparently, insurmountable barriers in the form of
fresh-water aquatoria in the limits of Pradnester and the middle Dnieper,
existing here in the course of almost the entire Early and Middle Anthro-
pogene. The presence of a fresh-water lake or group of lakes in the Pleisto-
cene on the territory of the entire present middle Dnieper has been quite
correctly established by geological studies (Pidoplichko, 1956). At this
time, the role of insurmountable barriers in the distribution of the above
enumerated species is played by the present valleys of Dnestr for S.
graecus and 5. polonicus, and that of Dnieper for the latter and 5. micro-
phthalmus. Of present-day representatives of the microphthalmus group,
apparently the most ancient branch, is S. graecus which, to a great extent,
has retained in its physiognomy the primitive features bringing it closer
to the Late Pliocene-Early Anthropogene S. minor.

Thus, based on the above historical geographic account of the distri-
bution of mole rats in the world, we cannot accept the migrational concept
put forth by Mehely (1909) and accepted further without any revision by
S. I. Ognev (1940, 1947). It concludes exclusively North African and
possibly Asian origin for the entire group with subsequent habitation by

+ should be М. leucodon—Editor.

112

its individual representatives on the territory of Europe and Asia, occupied
by the family at present. Also paleontological data do not correspond to
the hypothesis of the penetration of mole rats into Europe through the
Caucasus range. There are contradictions (only for representatives of the
family Spalacidae) in the Iranian course of penetration (Menzbir, 1934).

AN OUTLINE OF THE PHYLOGENY AND GEOLOGICAL
HISTORY OF MOLE RATS. IMPORTANCE OF THE
REMAINS OF SPALACIDAE FOR A STRATIGRAPHIC
DESCRIPTION OF NEOCENE AND ANTHROPOGENE
CONTINENTAL DEPOSITS OF EUROPE

The phylogenetic links of the family Spalacidae have not been firmly
established in view of the high level of specialization of its representatives.
The only dependable criterion for establishing the similarity could be
studied in the field of teeth development since the establishment of other
such structures in the skull and skeleton inherent in mole rats in the
course of evolution proceeded only for the specialized group. Conse-
quently, in most primitive representatives of the family, closer to the
ancestral forms, these features must be in the initial stage of development.
This, naturally, to a great degree complicates the elucidation of these
features with the help of usual morphometric methods. With regard to the
origin of mole rats, the opinion of Stehlin and Schaub (1951) and Schaub
(1958) may be considered the most acceptable viewpoint to this date.
It holds that Spalacidae, like the closely related family Rhizomyidae,
originate from the general root which separated somewhere in the Eocene
from the primitive Cricetidae, for which the pterydomidal plan of structure
of permanent molars was typical. The Miocene Anomalomyinae should
apparently be considered as forms of hamster-like rodents, if not as being
first in relation to mole rats and Rhizomyidae, then at least as being closely
related to the latter. The structure of the permanent molars in this group
of hamster-like rodents is characterized by extreme similarities with primi-
tive representatives of Spalacidae (sub-family Prospalacinae) and with
the most ancient specimens of present-day mole rats. In fact, the differ-
ences in them almost exclusively lead to the complicated structure of M?
and M, to M, in Anomalomyinae (Figure 34). Moreover, as shown by
Petter (1961), significant similarities with original mole rats are found in
the permanent molars of the relict group of Madagascar hamsters of the
subfamily Nesomyinae, which are close to Anomalomyinae. Besides simi-
larity in the structure of permanent molars, Anomalomyinae are character-
ized by a longitudinal ridge of:enamel on the lower incisors. Such for-
mations have been retained on similar teeth in Prospalacinae and the most
primitive representatives of the subfamily of present-day mole rats.

113

Between the two viewpoints on the origin of Spalacidae, the hypothesis
of Winge (1887) is worthy of consideration. It brings mole rats closer to
the jerboa (Dipodidae). At first glance
this closeness would seem to be proof
enough. Particularly, besides the fact
that representatives of both families
have permanent molars with a ptery-
domidal plan, the primitive mole rats
of the subfamily Prospalacinae are
characterized also by the presence of
a closed sub-occipital canal in the skull
which is inherent in a number of con-
temporary Palearctic Myoidea jerboas.
However, if we consider that hamsters
separated from the general stem of
Dipodidae and the branch of mole
rats, and Rhizomyidae in turn take
their start from the most ancient Crice-
tidae, then we can rightly assume that
the latter must still retain the sub-

ae i rows of permanent molars of Ano-
occipital canal lost by representatives rater СЕНА ПЕЙТЕ
of this family in the subsequent period. (by Grasse, 1955).
Consequently, this hypothesis could
also serve as an addendum to the earlier referred viewpoints of Stehlin
and Schaub throwing light on the peculiarities of structure of the original
group for Spalacidae.

The family of bamboo rats, Rhizomyidae, is close to mole rats. Both
families apparently originate from common ancestors. A proof of this
could be the considerable similarity in the structure of the lower jaw of the
Oligocene Rhizomyidae, Rhizospalacidae (genus Rhizospalax Miller and
Gidley), and primitive mole rats of the subfamily Prospalacinae. As
shown above (page 66), in Prospalacinae the lower jaw in a sense has
retained the Rhizomyidal plan of structure (Figure 40). There is no single
opinion on the systematic position and phylogenetic links of the Oligocene
Rhizospalacidae in current literature. It is known that the genus Rhizo-
spalax was described by Miller and Gidley (1919) from the late Oligocene
of France. These authors have absolutely correctly noted the general simi-
larity of the lower jaw of Rhizospalax with the same in Rhizomyidae, parti-
cularly in Tachyoryctes, simultaneously viewing similarities with mole rats
in respect to peculiarities of structure of the permanent molars. The latter
conclusion is highly risky since the remains of the skull and the lower jaw
at the disposal of these investigators belonged to old animals whose
teeth were in that stage of rubbing when rubbed surfaces in all Myoidea

8

Figure 34. A—upper and B—lower

114

acquire outlines similar in structure to the permanent molars of the Rhizo-
myidal plan. Attempts to explain identical features and differences between
Rhizospalax and bamboo rats on the one hand, and mole rats on the
other, in the structure of the retained portion of the hard palate, at present
also calls for doubt since in the structure of this section, as shown by an
examination of a series of skulls in Spalacidae and Rhizomyidae, no clear
differences have been exhibited. However, we may agree in principle with
the interpretation of the systematic position and phylogenetic links of
Rhizospalax given by the above authors. If in his earlier work, Miller
(1918) erroneously brought Rhizospalax close to the Spalacinae (subfamily
according to Tullberg’s system followed by the above authors), then later
he refrained from similar interpretations by suggesting that these Oligocene
rodents could be identified as an independent subfamily related to Rhizo-
myidae (Miller and Gidley, 1919). Somewhat later, Stehlin (1923) fully
subscribed to this opinion. He significantly revised the description of the
genus based on newer material. Like earlier authors, while correctly noting
the Rhizomyidal structure of the lower jaw in genera of Rhizospalax,
Stehlin gave, however, an absolutely unreliable viewpoint, on the structure
of the permanent molars in this group of Oligocene rodents, by relating
the structural characteristics of these teeth (without justification) of
Oligocene Rhizospalacidae to the similar ones in mole rats. As opposed
to Miller and Gidley who had only highly rubbed out permanent
molars of Rhizospalax Stehlin had a small series of teeth more or less
reflecting all the major stages of rubbing. This material has been pretty
well described by him (1923). The data permits us to conclude that the
Oligocene Rhizospalax, like Rhizomyidae, were characterized by well-
expressed folded structures in the initial stages of rubbing of the permanent
molars; at the same time, in mole rats, including highly specialized forms,
the tubercular structure is more expressed on evenly rubbed teeth. Thus,
molars in Rhizospalax are at a higher stage of specialization than in all
the later fossil and present-day spalacidae, although more primitive than
in fossil and living Rhizomyidae. Therefore, we do not see any contradic-
tion in bringing Oligocene Rhizospalacidae close to bamboo rats, and feel
that the schemes suggested by Simpson (1945) and Schaub (1955) are fully
justified. These schemes view the rodents in question as belonging to the
family of bamboo rats. True, it is quite likely that in future, with the avail-
ability of-new material, these rodents may have to be separated into a
special subfamily of ancient Rhizomyids—Rhizospalacinae—as suggested
by Miller and Gidley.

As noted above, considerable similarities with Rhizomyidae, especially
with ancient Oligocene Rhizospalacidae, are found in the structure of
the lower jaw of primitive mole rats from the subfamily Prospalacinae.
Therefore, it may be suggested that the ancestral form of Spalacidae should

115

apparently be searched among the given group of Oligocene rodents. The
latter does not at all mean that we consider this form as the only one known
at present, as representatives of Rhizospalacidae, genus Rhizospalax, since
its permanent molars are at a considerably higher level of specialization
than even in the most specialized mole rats. At the same time, it is quite
likely that types, as yet unknown, representative of this group of rodents,
which retained the primitive plan of structure of the permanent molars,
can give rise to the subfamily of ancient mole rats which, in turn, became
ancestors to the highly specialized present-day mole rats. Thus, the phylo-
genetic links of Spalacidae with some other families of rodents belonging
to the group Myoidea are seen by us in the form of a scheme presented in
Figure 35. According to this scheme, the separation of the group Spala-
cidae from the genera stem occurs in the Middle Oligocene, since by the

Dipodidae Cricetidae pbzleciae Bhizomy idee

Anthropogene | | Z |
ee

Miocene

Neogene

ou

|=
Е

Figure 35. А scheme of phylogenetic relationships of Spalacidae.

Paleogene

I—Rhizospalacinae; 2—Rhizomyinae; 3—Rhizospalax.

end of this era there already existed representatives of Rhizospalacidae
with a degree of specialization of molars higher than that conditional
level which had to be present in the suggested ancestors of mole rats.

As for the phylogenetic relationships of various groups of mole rats
within a family, the scheme suggested by Mehely (1909), somewhat sup-
plemented and corrected by S. I. Ognev (1940), and to a lesser extent the
scheme of E. G. Reshetnik (1941), are the most popular ones in literature.

116

The real drawback in both systems is that they do not take the geologic
factor into account at all. Moreover, the phylogenetic structure is based
almost exclusively on a study of morphological peculiarities and the distri-
bution of the present representatives of the family, without due considera-
tion for paleontological material (Mehely, 1909; Ognev, 1940, 1947). In
such cases when paleontological material was used to explain the affinity
of various groups within the family (Reshetnik 1941), it was done without
due interpretation and revision of the systematic position of fossil forms,
in view of which the suggested scheme contains various serious factual
inaccuracies.

The Mehely-Ognev scheme reflects in general the level of knowledge
during their time. It includes major trends in the evolution of the family,
although the interpretation of position in the system and affinity links of
some taxa is highly disputable. However, if we discard the migrational
hypothesis of the above authors, which in the light of the present level of
knowledge of the paleogeography of the Mediterranean and Pontiac
Caspian in the Neogene and Anthropogene is highly unacceptable, then
the above scheme clearly defines two major lines of development in
present-day mole rats corresponding to the genera Microspalax (subgenus
Mesospalax) and Spalax (Figure 36). It has been very correctly pointed
out that both branches take their start from the most primitive representa-
tives of present mole rats, combining the Nominal subgenus of the genus
Microspalax. However, an examination of the present-day M. ehrenbergi
as a direct ancestor of Mesospalax and Spalax is justifiable doubtfully at

hungaricus

Я lonicus
transsy|vanicus roo

syrmiensis Е
microphthalmus

/ serbicus antiquus

monticola :
dclorogeae istricus giganteus
turcicus
5 ro 5
hercegovinesis armeniacus 9'4eCU
ВЕ nehringi
cilicicus 3 Macrospalax
anatoli- hypotheticus

cus

Mesospalax
hypotheticus

fritschi

kirgisorum
: ~—~_Microspalax

_— ehrenbergi

aegyptiacus
Prospalax

priscus

Figure 36. A scheme of phylogenetic relationships within
the family Spalacidae (by Mehely, 1909).

ВИЙ

this time. In our opinion, the most conspicuous drawback to the scheme
is an attempt to derive present-day subspecies from other similar present-
day forms. In addition, the number of the latter is unjustifiably high (see
page 6). The substantial effect of the phylogenetic scheme of Mehely-
Ognev is also an attempt to view the highly specialized P. priscus as direct
ancestors of all living mole rats, though the phylogenetic link of the sub-
family of ancient mole rats to which P. priscus and present-day mole rats
belong, has been correctly noted in general.

The following inaccuracies are brought forward in the phylogenetic
scheme suggested by Reshetnik (1941) (Figure 37).

1. The genus Rhizospalax should not be considered as a general
ancestor of Rhizomyids and mole rats (pages 113-14).

2. The phylogenetic series Miospalax! Stromer—Prospalax priscus—

Macrospalax Масгозра!ах
uralensis giganteus
Macrospalax

microphthal-|
mus

a

Macrospalax Macrospalax
arenarius zemni
+
Macrospalax
diluvil

ee ‘ i lax
at a M ABs Microspalax} |Microspa
i i acrospalax
x x с
м p р ypotheticus ehrenberg! leucodon
i Prospalax °
Rhizomys Tachyorycte т
+
Rhizomyinaeé Miospalax
Mis
Rhizospalax
poirrieri _

Figure 37. A scheme of phylogenetic relationships within
the family Spalacidae (by Reshetnik, 1941).

Macrospalax
istricus

acrospala
graecus

1 Nomen praeoccupatum in relation to the generic group of zukors Myospalax
Laxmann, 1769.

118

Macrospalax ( = Spalax sen. str.) is artificial. Investigations show that
Miospalax monacensis Stromer from the Late Miocene of Bavaria, in its
general plan of structure of the upper permanent molars, is closest to the
fossil hamsters of the subfamily Anomalomyinae and, most probably,
must be considered as a part of the latter. The differences between the
most specialized representatives of the subfamily of present mole rats
forming genus Spalax and ancient mole rats are so great that it is difficult
to visualize the direct ancestral link of the former with the latter, bypassing
the intermediate group such as representatives of the Nominal subgenus
of the genus Microspalax and especially its Miopliocene representatives
with regard to the structure of the skull, the permanent molars, and the
bones of limbs which exhibit similarity with Spalax.

3. The inclusion of P. rumanus in the genus Pliospalax (one of the
synonyms for Microspalax) is based on the nomenclatural confusion asso-
ciated with an incorrect translation of the paper written by Kormos (1932)
which described the genus Pliospalax (details on page 203). In fact this
species should be considered under the genus Prospalax.

4. The phylogenetic links within the genus Spalax do not correspond
to reality since the level of specialization of individual species has been
ascertained arbitrarily. In addition, the reasons are not absolutely clear
as to why it was necessary for this author to conclude the phylogenetic
series of forms of the genus Spalax with giant mole rats standing, as
will be shown later on, at a lower level of specialization, based on the
whole group of features, than S. microphthalmus, which is considered as
a direct ancestor of S. giganteus. It is also not clear why the Bukovin
mole rat (S. graecus) has been identified in an independent evolutionary
line.

Thus, the above phylogenetic relationships appear mostly obsolete
today. More so because, in recent years, significant new paleontological
material has accumulated which can throw some light on the different
stages of evolution within the family. Admittedly, this material is far from
complete. Furthermore, we are deprived of exhaustive paleontological
documentation characterizing the stage of separation of branches of
ancient and present-day mole rats. Besides, any paleontological indications
whatsoever of the time of emergence of the ancestors of the group of
specialized forms of the genus Microspalax (subgenus Mesospalax) are
totally absent. However, a comparative analysis of morphological features
and the distribution of fossil and living mole rats permits us to identify
series of branches combining forms with close adaptive characteristics
and to identify various groups as independent subfamilies, genera, and
subgenera. In our opinion, the scheme suggested below (Figure 38)
reflects more reliably the trends in the evolution of the family and the
phylogenetic links of subfamilies, genera, subgenera, and in some cases,

119

even species and, consequently, may serve аз the foundation for the
classification of Spalacidae described in this book.

The fossil subfamily of ancient mole rats—Prospalacinae—is the most
primitive and apparently the oldest group among Spalacidae. As has been
repeatedly pointed out in the preceding sections of this book, the repre-
sentatives of Prospalacinae with regard to the structure of the lower jaw
have, to a great extent, retained the features of Rhizomyidae to the fossil

Spalacinae Prospalacinae
Spalax Microspalax Prospalax
14 13 12 10 9 7 6

poe МАТ Ty \
№ ох
‘WH \ м

o
=
@
a
|=]
=
[=]
—
=
—
=
<
SS aS

Neogene

Paleogene
(Oligocene)

Figure 38. A scheme of phylogenetic relationships within the family Spalacidae.

1—Prospalax rumanus Sim.; 2—P. priscus (Nehr.); 3—Microspalax composito-

dontus sp. nov.; 4—M. macoveii (Sim.); 5—М. odessanus sp. nov. ; 6—M. ehrenbergi

(Nehr.); 7—М. nehringi (Sat.); 8—M. leucodon (Nord.); 9—Spalax giganteus

Nehr. /0—S. arenarius Resh.; 11—S. minor W. Тор.; 12—S. graecus Nehr.;
13—S. polonicus Meh.; 14—5. microphthalmus Gild.

Oligocene Rhizospalacinae. Among the features characteristic of Rhizo-
myidae, mention must be made first of the position of the angular process
of the lower jaw in relation to the articular and alveolar ones, the com-
paratively lesser height of the latter, and also the clearly expressed ridge
of the lower masseter plate in ancient mole rats. In addition, the facial
portion of the skull of ancient mole rats, in general, acquired an outline,
inherent in representatives of the family Spalacidae. Substantial features
make it possible to readily differentiate the ancient mole rats from Rhizo-
myids: the presence in the former of a low, wide rostral section of the

120

skull, the width of which considerably exceeds its least height; ап elon-
gation and contraction of the nasal bones; a large, comparatively narrow
suboccipital cavity, the greatest diameter of which is roughly equal to the
length of the two anterior permanent molars; a low placed, in relation to
the teeth-rows, zygomatic arch base; incisor cavities shifted backward; a
shortened masseter plate of the skull located almost in a horizontal plane,
the anterior borders of which, furthermore, do not reach the sutures
between the premandibular and mandibular bones, and their lengths being
less than the same in М! to M?; a highly deviated backward articular
process of the lower jaw, the longitudinal axis of which agrees roughly with
the same of the horizontal branch, and the more expressed tubercular
plan of structure of the upper and lower permanent molars. Thus,
there is no doubt that the subfamily of ancient mole rats is a connecting
link between the highly specialized present-day mole rats and the ancestral
group of ancient Rhizomyids—the Oligocene Rhizospalacinae.

Unfortunately, the fossil Prospalacinae is presently known only from
the remains of comparatively later representatives, P. priscus (end of the
Middle and first half of Late Pliocene) and P. rumanus (Middle Pliocene)
with features of high specialization in the structure of the permanent
molars. In particular, the molars of the aforementioned forms are even
simpler than in the most ancient of the present mole rats of the Mioplio-
cene group, i.e., compositodontus mole rats from the Nominal subgenus
of the genus Microspalax. Therefore, it is quite natural that the above
noted species cannot be considered as most primitive among Spalacinae.
This is contradicted also by the fact of finding remains of present-day
mole rats in deposits older than those in which the remains of P. rumanus
and P. priscus have been found. Thus, remains of the primitive M. com-
positodontus were excavated from the strata of the Upper Miocene (Meotes)
of the northwest cis-Black Sea region of the Ukraine SSR. Consequently,
the roots of the subfamily Spalacinae, combining the most highly special-
ized forms of mole rats, apparently pass still deeper in the depths of the
upper portion of the Middle Miocene, and the initial forms for the present-
day mole rat group from the subfamily Prospalacinae should most prob-
ably be searched among the Middle Miocene species which are more
primitive than the ones known at present (P. rumanus and P. priscus).
Their remains have not yet been found due primarily to a far too incom-
plete study of Miocene rodents in general.

Among Spalacinae, the mole rats of the genus Microspalax form the
most primitive group. The most ancient representatives of living mole rats,
i.e., species of the subgenus Microspalax, also belong to this genus. The
latter is represented mostly by fossil forms, remains of which are found
in deposits starting from the Upper Miocene to the Upper Pliocene inclu-
sively, and also the only present-day representative of Asia Minor and

121

North Africa, М. ehrenbergi, whose relict nature at present is undisputed.
In one of the preceding sections (page 64) we have discussed the major
adaptive changes of the skull and the skeleton in the evolution of mole
rats. It was shown that the leading trend in the evolution of the family
was the specialization to search of food underground and the multifarious
adaptations to burrowing and feeding. If we examine representatives of
the subgenus Microspalax from this aspect, then to the number of features
pointing to a primitive organization of the latter, we must add first of all
the following features: very weakly developed sagittal and lambdoid crest
of the skull, relatively wide parietal bones (a feature correlating with the
degree of development of the sagittal ridge), a very sunken occipital bone,
shortened upper and lower diastemata, considerable isolation of the
angular process of the lower jaw, the comparatively small height of its
alveolar process, the contraction of lower and upper incisors, and the
most complicated permanent molars, the roots of which, furthermore,
are the least reduced among all of the present-day mole rats. To the number
of primitive features we should also add the presence of three longitudinal
ridges on the lower incisors in representatives of the given subgenus. This
peculiarity of structure has so far not been subjected to functional analysis
and apparently relates to features inherited by representatives of the
subgenus Microspalax from their direct ancestors, the extinct Prospala-
cinae. Thus, mole rats of the subgenus Microspalax, based on the series
of indices enumerated above, are precisely that link which connects the
extinct primitive Prospalacinae with the more highly specialized repre-
sentatives of Spalacinae of the subgenus Mesospalax on one hand, and
the most highly organized among present mole rats, the genus Spalax on
the other.

The phylogenetic links of the different species of the subgenus Micro-
spalax, considering their level of specialization, can be viewed in the
following manner. The most primitive group in the subgenus most prob-
ably constitutes the late Miocene European compositodontus mole rats,
namely the cis-Black Sea M. compositodontus. The name is derived from
the complexity of their permanent molars, primarily because the upper
and lower front ones still retain a free mesocone on М! and a mesoconid
M,. In addition, molars of the enumerated species as compared to the
Middle and Late Pliocene Microspalax are characterized by great isolation,
next to the paracone on the upper and the entoconid on the lower front
permanent molars, a less reduced МЗ, and also by less reduced roots. The
Late Miocene compositodontus mole rat, in all probability, is the earliest
group in relation to all the remaining European fossil Microspalax. It is
most likely that in the evolutionary process of the subgenus, there was
even a direct phylogenetic series of М. compositodontus—M. тасоуей—а
form close to M. odessanus, since in this species a constant increase in

122

adaptation to burrowing and feeding is demonstrated in the structure of
the masticatory apparatus. Moreover, in the degree of specialization of
incisors M. compositodontus considerably excels the living M. ehrenbergi
which naturally complicates conclusions about their direct ancestral link.

A further stage in the evolution of the group is represented by the
Mid-Pliocene species M. macoveii and M. odessanus. The structure of
their permanent molars illustrates most clearly the tendency during evo-
lution as indicated earlier toward simplification in the structure of their
grinding surfaces. Thus, both species, as distinct from the late Middle
Miocene compositodontus mole rats, have already totally lost the meso-
cone on M1}, having retained a mesoconid on the front lower permanent
molar in the initial and partly in the middle stages of wearing off (M.
macoveii) or only in the very vestigial stage (М. odessanus). Thus М.
тасоуей is still characterized by a comparatively larger mesoconid on M,,
and in M. odessanus, the same is usually found only in a vestigial state or
is even totally absent. Further, if the entoconid on M, in Late Miocene
compositodontus mole rats is not fused with the posterior collar until after
maturity, then in M. macoveii these loops are fused already in the initial
stages of tooth wearing in adults, and in M. odessanus the free entoconid
is generally observed only in very young specimens. In addition to the
foregoing primitive peculiarities in the structure of permanent molars, М.
macoveii also has various other features of a comparatively primitive
organization. Mention must first be made of the presence of a relatively
short diastema on the lower jaw of this species, a shortened symphytic
tubercle, a well-expressed jaw angle, and a highly deviated, downward
and sharply demarcated angular process. Moreover, as far as the special-
ization of incisors is concerned M. macoveii surpasses all the presently
known species of the subgenus Microspalax. This makes it impossible to
consider it as a direct ancestor of the later M. odessanus, not to speak of
the present-day M. ehrenbergi.

M. odessanus should be considered as the most highly specialized repre-
sentative of the subgenus Microspalax. Its remains have been excavated
from deposits of the uppermost middle and lower depths of the Upper
Pliocene. In addition to the characteristics already mentioned in the struc-
ture of permanent molars, a considerable widening of the skull in the
region of the incisors and the entire rostrum as a whole, the absence of a
longitudinal slit-like cavity on the nasal bones, the straight line of the
forehead—nasal and forehead, jaw sutures, and a relatively high and thick
horizontal branch of the lower jaw—are characteristics of this species.
The upper and lower incisors, although not as widened as in M. macoveii,
nevertheless demonstrate a very high level of specialization. Moreover, the
species has retained the whole range of primitive characteristics in the
structure of the skull and the lower jaw. Furthermore, except for features

123

determining its subgenus affinity, the lower jaw of М. odessanus has still
retained many structural characteristics bringing it close to M. macoveii,
although they are expressed to a lesser degree in the latter (sharp demar-
cation of symphytic tubercle, well-expressed jaw angle, considerable sepa-
ration of the angular process). It must be emphasized that despite the
retention of a series of primitive features in the structure of the skull and
the lower jaw, the odessanus mole rats, in their degree of development of
burrowing adaptations, stand at a higher level than even some primitive
members of the subgenus Mesospalax, particularly М. nehringi, not 10.
speak of the recent M. ehrenbergi. This is equally true in respect of the
above discussed facts relating to M. macoveii, and they totally exclude
the possibility of viewing the group of Middle Pliocene European Micro-
spalax as ancestral in relation to Mesospalax. Moreover, this group is
apparently ancestral in relation to the most highly specialized representa-
tive of the subfamily of present-day mole rats of the genus Spalax. A proof
of this could be the considerable similarity between the listed groups in
individual details of structure for skulls and bones of limbs (shortened
non-branched portion of the sagittal ridge, indistinct posterior palatine
pits in the hard plate, and others) expressed more strongly than, for
example, between Spalax and Mesospalax. Moreover, very primitive repre-
sentatives of the genus Spalax, for instance from the group of giant mole
rats, have retained in their organization other features of similarity with
Microspalax. Thus, in S. giganteus the upper and lower diastemata are
very short, the incisors are narrower than in the most highly specialized
Mesospalax. Furthermore, the lower jaw in this species, as also in repre-
sentatives of the subgenus Microspalax, has retained an alveolar process
which in its height is only just equal to the articular one.

Among the species of the subgenus Microspalax, living representatives
and the North African M. ehrenbergi have a special place. Together with
features of higher evolutionary status (relatively longer sagittal ridge of
the skull, smooth symphytic tubercle and jaw angle of lower jaw, sepa-
ration of its angular process less expressed as compared to the Middle
Pliocene Microspalax.), this species has retained many primitive features
found in a lower level of specialization than in the Middle Pliocene and,
in some cases, even in Late Miocene representatives of the given subgenus.
In addition, the Ehrenberg mole rats are the only representatives of the
subgenus that have retained longitudinal ridges not only on the lower but
also on the upper incisors. Moreover, the species is characterized by the
narrowest incisors among representatives of present-day mole rats. In the
degree of complexity of permanent molars, M. ehrenbergi occupies an
intermediate place between the Late Miocene compositodontus mole rats
and the Middle Pliocene M. macoveii on the one hand and M. odessanus
on the other. Thus, despite the fact that the front upper and lower per-

124

manent molars have already lost the mesocone and mesoconid respectively,
the entoconid on M, remains unfused with the posterior collar in later
stages of wearing than in the Pliocene Odessa mole rats. Considering what
has been said above and also such an important factor as the present
distribution of the species, it may be concluded that M. ehrenbergi is,
apparently, a special Afro-Asian branch of the subgenus separating equally
from the general stem of Microspalax. Considering that in the Middle
Pliocene of Europe there were already species which stood at a higher
level of specialization than the present M. ehrenbergi with regard to a
series of features, we have to obviously assume that the separation of the
Afro-Asian and European branches of Microspalax took place somewhere
in the beginning of the Pliocene. Quite likely, a specific disjunctive role
was played in this case by the transgression of the Pontiac basin.

At present, there are many inaccuracies in the knowledge of the origin
of mole rats of the subgenus Mesospalax. This is first of all linked to the
inadequacies of paleontological documentation due to a poor study of
the territory of Asia Minor and the Balkans in this respect. This group
most probably has an Asia Minor—Balkan origin. Results of comparative
anatomical studies on the skull and the lower jaw in present-day species
—М. nehringi and М. leucodon—point immediately to the phylogenetic
link of this group with the Afro-Asian branch of Microspalax. Further-
more, the most primitive representative of the subgenus Mesospalax, the
Asia Minor М. nehringi, has mostly retained even now features similar
to Microspalax (the presence of slit-like cavities on the nasal bones, a
relatively narrower rostral section of the skull, contracted upper and lower
incisors). The proof of a closer relationship between the above listed
groups lies apparently in the fact that the specialization of the skull in
Mesospalax, and equally in the Afro-Asian Microspalax, as distinct from
the European fossil Microspalax and Spalax, proceeded in the direction
of an increase in overall length of the unbranched part of the sagittal
ridge. In the more highly specialized European Mesospalax (M. leucodon)
similarity of features with the initial type has been lost to a great extent.
Here, the differences reach a maximum in the easternmost Nominal sub-
species М. [. leucodon, while the Balkan form, М. [. monticola, mostly
retains features similar to M. nehringi, being, as it were, the connecting
link between the latter and M. /. leucodon. This apparently also points to
the close relationship between the Asia Minor M. nehringi and the Euro-
pean M. leucodon. The period of separation of the Asia Minor and the
European branches of Mesospalax has not been established finally. It
may be assumed that the disjunction of the above species in the region of
the Aegean land took place for the second time somewhere on the border
between the Pliocene and Anthropogene.

It was noted above that the most probable ancestral group in relation

125

to the genus Spalax, combining the most highly specialized representatives
of the subfamily of present-day mole rats, is the Middle Pliocene European
Microspalax. These mole rats have mostly an East European distribution
and origin, only partly entering the North Caspian east of the Ural River
and the trans-Caspian. Precisely, the area of evolution of the genus was
parts of the Caspian land. Reliable remains of representatives of the genus
Spalax are known at present, beginning from the second half of the Late
Pliocene in the limits of the cis-Black Sea and cis-Azov Ukraine and
Taman. However, these remains belong to species standing at a higher
level of specialization than, for example, the present S. giganteus. Conse-
quently, roots of the group probably pass still deeper toward the beginning
of the Late, and the end of the Middle Pliocene.

Of the number of species of Spalax known presently, the most primitive
facial outline is retained by the living giant mole rat. In the structure of
its masticatory apparatus, it shows many features similar to the European
Pliocene Microspalax. This species is characterized in particular by the
presence of relatively shorter upper and lower diastemata, shortened
incisors, and a lower alveolar process in the lower jaw. All this makes it
possible to assume the comparatively earlier separation of the eastern
branch of the genus, the group of giant mole rats, from the western branch
to which we relate 5. Microphthalmus and forms close to it. Most probably
the roots of this group pass to the beginning of the Late Pliocene, and
the retention of such primitive representatives as S. giganteus up to the
present time is apparently explained by the isolating influence of the
Manych Strait which existed since the Late Pliocene and possibly up to
the Pleistocene inclusively.

In the other representatives of the group of giant mole rats, the present-
day S. arenarius, the primitive features in the structure of the masticatory
apparatus which brought mole rats of this group closer to the ancestral
forms have been almost completely lost. The individual features of organ-
ization retained were only in the structure of the rostral section of the skull
and partly the permanent molars. It may be suggested that the ancestral
forms of this branch of giant mole rats, being isolated by the Manych
Strait from the Caspian branch ancestral to S. giganteus, developed under
conditions of the northeast Black Sea region in the same direction as mole
rats of the microphthalmus group. Documentarily, the roots of the group
of the above-mentioned mole rats are traced from the present time to the
beginning of the Anthropogene inclusively. For example, in the lower
Anthropogene deposits of the village Tikhonovka, Zaporozh’e region,
remains of the species have been found which are very much closer to the
now living S. arenarius.

Among the most highly specialized mole rats of the microphthalmus
group, the most ancient and apparently primitive form, S. minor, is from

126

the Late Pliocene of the north Black and Атоу Sea. The present-day 5.
graecus has retained a number of features similar to it. This species has
most probably retained to a considerable extent the facial outline of the
form ancestral to more highly specialized forms of Middle and Late
Anthropogene, including the present ones, S. microphthalmus and S.
polonicus. As for the latter, their differentiation, considering the very small
range of differences, took place somewhere on the border of the Early
and Middle Anthropogene. In any case, in the Late Pleistocene the com-
plete differentiation of the above-listed forms of present times has been
confirmed documentarily by paleontological data.

In conclusion, the author feels it expedient to present a brief outline
of the geological history of mole rats against the background of the
development of faunal complexes of mammals, mostly smaller ones, the
remains of which are most suitable for the purpose of bio-stratigraphy
and paleogeography on the territory of Eastern Europe. Similar data, it
appears to us, is not only of theoretical interest but also has a particular
practical importance since it forms a suitable basis for a stratigraphic
delineation of the remains of mole rats found in continental deposits of
Neogene and Anthropogene, and their corresponding correlation within
the limits of geographically remote areas.

It was noted above that the most primitive and apparently the most
ancient group of mole rats combined in the subfamily Prospalacinae is
presently known only from the comparatively late highly specialized repre-
sentatives, P. rumanus and P. priscus. The remains of the former have been
found in Middle Pliocene deposits of the Kuchurgan valley (Ukraine
SSR, Odessa region) and territorially adjacent deposits of Rumania of the
same age (the well-known Malushteni Kovurlui region, right bank of the
Prut River and its lower reaches). In both places remains of mammals
jointly constituting the so-called Kuchurgan Middle Pliocene faunal com-
plex whose analogue in western Europe is the Middle Pliocene Russilion
fauna of France, were likewise found. The following are the characteristics
of the Middle Pliocene fauna of smaller mammals of the northwest Black
Sea region:

1. Qualitative predominance of remains of rabbit-like animals over
rodents.

2. Archaic rabbit-like fauna on the whole (rabbits being represented
by genera Alilepus Dice and Pliopentalagus Gureev and Konkova; and
pica of the genera Prolagus Pomel, Proochotona Chomenko, and the most
ancient representatives of the genus Ochotona Link—O. antiqua Pidopl.).

3. Presence of beavers of the genus Steneofiber Geoffroy and Promi-
momys-Dolomys complex of a species of Rhizomyid field rats. The latter
are represented in the Kuchurgan fauna by species Promimomys moldavicus
(Kormos) and Dolomys aff. milleri. Nehr.

127

4. Absence of Rhizomyid cementodontus field rats of the genus
Mimomys F. Major.

In deposits of this type, remains of P. rumanus have been found along
with Middle Pliocene mole rats of the genus Microspalax—M. macoveii.
Considering the above-noted distribution of the finds of P. rumanus, we
may assume the specificity of the given species for deposits of the Kuchur-
gan stage.

P. priscus was apparently distributed over a wider time interval than
P. rumanus within the area adjacent to the USSR, i.e., the countries of
western Europe. Presently, its remains are known from various locations
in Rumania (Beralt Kepeni, Transylvania), Hungary (Beremend, areas
4, 5, 7; Charnota, areas 1 to 3; Nadkhoroshan, area 1; and Villan, areas
3, 5, 11—all in south Hungary, Villan Hills, and also Kishlanga), Poland
(Venzhe, area 1; Rembelitsy Krulevskie), and Czechoslovakia (Ivanovsky,
near Trenchina, Slovakia). The geological age of most of the above-noted
locations has been determined as Astian and Willifrank which most prob-
ably correspond to different time sections of the Middle and Late Pliocene
in our interpretation. The Kuchurgan fauna of Chernotana, Hungary is
closest. Thus, according to the data of Kretzoi (1956), in its composition
P. priscus also follows Promimomys and Dolomys groups—P. moldavicus,
D. milleri, D. hungaricus Kormos. Moreover, the fauna is widely repre-
sented by folded-toothed hamster-like rodents belonging to the genus
Baranomys Kormos. All this allows us to place, with a high degree of
probability, the Chernotana deposits parallel to deposits of the Kuchurgan
Shield (Topachevskii, 1965). The later, 1.е., Willifrank, stage of develop-
ment is represented by the fauna of Beremend (areas 5, 7), Nadkhoroshan
(area 1), Villan (areas 3 and, probably 5 and 11) where the remains of P.
priscus are found along with cementodontus Rhizomyid field rats of the
genera Mimomys and Kislangia Kretzoi—M. pliocaenicus, Е. Major, М.
fejervaryi Kormos, M. pusillus Mehely, M. newtoni F. Major, K. rex
(Kormos) and Rhizomyid noncementodontus ones, Villanyia Kretzoi—V.
exilis Kretzoi, V. petenyii (Mehely), V. hungaricus (Kormos). In certain
locations they are also associated with remains of the more ancient D.
milleri. Probably, this group of locations in Hungary corresponds in the
limits of the Soviet Union to the deposits containing fauna of the Khaprov
faunal complex (lower horizon of Kryzhanovka, Odessa region; middle
layer of alluvial deposits exposed along the left bank of the Khadzhibei
estuary near Avgustovka village, Odessa region; and depressions on
Yalpukh Lake, Odessa region). A still later phase in evolution of the Late
Pliocene fauna of rodents reflects the complexes from the locations Bere-
mend 4, Villan 5, and Kishlanga, where the remains of P. priscus ate asso-
ciated with non-Rhizomyid field rats laguridna (L. arankae Kretzoi) and
the cementodontus-allophajomys group (Allophajomys Kormos). This

128

association, in geological age in the limits of the USSR, is apparently close
to strata containing rodent fauna of Odessa, Nogai, and complexes closer
to them.

The Astian phase of development of the Pliocene faunal complexes of
West Europe is probably reflected by the fauna of Venzhe, area 1 in
Poland. Remains of P. priscus have been found here according to Sulimski
(1964) and Kowalski (1960b) along with similar ones of folded-toothed
hamsters of the genera Trilophomys Deperet and Baranomys, primitive
mole voles of the genera, Ungaromys Kormos and Germanomys Heller,
non-Rhizomyid field rats of older types—genus Dolomys, Villanyia, Cseria.
Kretzoi brings this group closer to faunal complexes of the north-west
Black Sea region of the Ukraine SSR, particularly with the Kuchurgan
one by the presence of Petauristin in its composition. As for such locations
as Rembelitsy, and Krulevskie in Poland, their age most probably corres-
ponds to Willifrank (Kowalski, 1960a, 1960b; Fejfar, 1957).

Thus, based on what has been said above, it is quite evident that within
the limits of countries adjacent to the USSR and Poland (Precarpathia),
Czechoslovakia, Hungary and Rumania (Transylvania), the remains of -
representatives of the subfamily of ancient mole rats are found in deposits
which, in the northwest Black Sea region of Rumania and the adjacent
territory of the Ukraine SSR and Moldavia as well as the Azov Sea region,
already contain similar remains of present-day mole rats from the genera
Microspalax and even- Spalax. Consequently, it may be suggested that
representatives of both subfamilies in the course of the entire Middle and
almost the entire Late Pliocene coexisted in time within the limits of
different regions of Europe. In view of this, the remains of mole rats could
be used only to a restricted degree for correlation of the corresponding
strata of Poland, Czechoslovakia, Hungary and the northwest regions of
Rumania with similar aged strata of continental remains of the northwest
Black Sea and Azov Sea regions.

The most ancient recoveries of remains of present-day mole rats
(Spalacinae) in Europe are well known presently from the limits of the
northwest Black Sea region of the USSR, starting apparently from the
Meotes. In particular, remains of the comparatively primitive М. composi-
todontus have been found in gravels exposed near Andreevka village,
Berezansk district, Nikolaevsk region of the Ukraine SSR. These gravels
lie apparently within Pontiac limestone. The remains of M. composito-
dontus in the range of this locality coexist with fauna including Steneofiber
hamster-like rodents, dormice (Myoxidae), and large Muridae. Similar
fauna is presently known from the lower strata of alluvial beds exposed
along the left bank of the Khadzhibei estuary near the Avgustovka village,
Odessa region (Topachevskii, 1965). Here osteoferous gravels lie in gray-
dove colored clays at a hypsometric level of eight to ten meters above

129

sea level, directly under the place of fossilization of Hipparion fauna,
the age of which, as determined by Korotkevish, relates to the latest
Meotes.

The remains of М. macoveii in the limits of the north-western Black
Sea region are confined to the strata of the Astian stage which in the
opinion of N. A. Konstantinova (1965) includes the Kuchurgan deposits
and probably the strata from Moldavia which are similar in age and
contain fauna similar to that of the Russilion, France. Here in the Kuchur-
gan deposits, they are associated with isolated remains of ancient mole
rats. We have already discussed the characteristics of the Kuchurgan
Middle Pliocene faunal complex. As for fauna of smaller mammals of the
Moldavian Russilion, it is quite similar to that of the Kuchurgan. The
difference lies in not finding here the field voles of the genus Promimomys
and the addition of smaller forms from the genus Dolomys—D. kowalskii
Schevtschenko, although close to the Hungarian D. hungaricus, apparently
differs from it in the primitive outline of the frontal section of the worn
out surface of M, (unpaired anterior palate and the paraconid complex),
and noncementodontus Rhizomyid field voles of an ancient type from the
polymorphic composite group Villanyia-Cseria. If we compare this com-
plex with the fauna of field voles of the Hungarian Charnotana, then we
do not find any principal differences between them.

The remains of M. odessanus, confined to the territory of the north-
western Black Sea region to the strata apparently completing the Astian
phase of deposition (the Odessian karst hollows), are found in abundance
in the sediments of the Willifrank stage (Kotlovina village on Yalpuk
Island; lower horizon of Kulyalnits deposits of the village Kryzhanovka
near Odessa; middle horizon of the old alluvial bed exposed along the
left bank of the Khadzhibei estuary near the Avgustovka village, Odessa
region) and rarely in the Upper Pliocene, post-Willifrank deposits (village
Kaira, Gornostaev district, Khersonsk region of the Ukraine SSR; lower
layer of the Nogai bed). In the first case, they are associated with the
lagomorph-Cricetidae complex of smaller mammals which contain field
vole forms from the group D. hungaricus. In the Willifrank-Khaprov
faunal complex, the remains of M. odessanus have been found along with
rich Microtidae fauna which already include Rhizomyids cementodontus
field voles from the genera Mimomys (M. pliocaenicus and M. reidi),
and Kislanagia, as well as comparatively later Dolomys from the group
hungaricus-episcopalis and ucrainicus with the retention of primitive non-
cementodontus Rhizomyid field voles of the polymorphic group Villanyia-
Cseria, close to the Hungarian V. petenyii (Mehely), (M. tenaitica Schevts-
chenko, M. lagurodontoides Schevtschenko, M. praehungaricus Schevts-
chenko), and Cseria gracilis Kretzoi, as well as the ancient D. milleri.
Finally, in the post-Willifrank they are associated with the Kair and the

9

130

Nogai complexes of field voles which include non-Rhizomyid field voles
of Microtid (Allophajomys) and lagurid (genus Lagurus, subgenus Laguro-
don Kretzoi) groups.

In the deposits of the post-Willifrank phase of the Late Pliocene, mole
rats of the genus Microspalax immediately replaced the specialized early
representatives of the genus Spalax (S. minor) and forms close to them.
The remains of mole rats of this group have recently been found in the
limits of the Black Sea region of the Soviet Union in the strata containing
smaller mammalian fauna belonging to the so-called Odessian (the upper
horizon of the Kuyalnits deposits of Kryzhanovka; alluvial beds exposed
along the right bank of the Kuyalnits estuary on the territory of the
health resort bearing the same name in Odessa) and the Nogai faunal
complexes (Azov coast near Nogaisk, Zaporozh’e region; Tarkhankut
near the settlement Chernomorskoe in Crimea; lower portions of the
upper layer of the Khadzhibei deposits; and Tsimbal in Tamani). In the
first case, they are associated with Lagurodontus-Allophajomys complexes
of field voles which retained the Willifrank relicts represented mostly by
M. pliocaenicus and, to a lesser extent, the Rhizomyid non-cementodontus
field voles of the genus Villanyia. In the second case, they are associated
roughly with the same Lagurodontus-Allophajomys complexes but with
the association of later Mimomys (M. intermedius Newton). It should also
be noted that S. minor in the limits of the cis-Black Sea and Azov Sea
regions of the Soviet Union apparently lived till the beginning of the
Anthropogene. This is testified to by findings of remains, although not in
large number, in the lower Anthropogene strata exposed near the village
Tikhonovka, Novo-Vasil’evskii district, Zaporozh’e region, along with
finds of early Arvicola Lacepede, Microtus Schrank (including the sub-
genus Pitymys Mc. Murtrie), and highly specialized Lagurids of the sub-
genus Lagurus Gloger and Eolagurus Argyropulo. The remains of this
fauna are also associated with mole rats close to the present-day S. are-
narius. It should be emphasized, however, that the early Anthropogene
mole rats are one of the least studied groups.

Finally, in the deposits of even later sediments of the Anthropogene
starting from the Pleistocene, we come across the remains of species close
to present representatives of the genus.

The stratigraphic affinity of the remains of mole rats found on the
territory of USSR and in Western Europe is represented in the scheme
in Figure 39.

CLASSIFICATION

In the present work we have done the classification of the family
Spalacidae somewhat differently from the one used in the works of most

According to According to
1.0. Plidoplichko (1955) | \.1. Gromov et al. (1965)

Upper
(Holocene)
wen 1
wen
ower

ne

(Thiverian)

ЕорНосепе

Gums ва wil М.оЧеззапиз

» Prumanus
M.macoveii

fe
En

Pliocene

oe
oe

M.compositodontus

Pliocene

Upper
(Meotis)

Figure 39. A scheme of distribution of Spalacidae in time and space.

of our predecessors. This system has been considerably revised on the
basis of new data on classification by Mehely (1909). The basis for such
a revision was the morphologic and systematic study in depth not only
of present-day but also fossil representatives of the family with due con-
sideration to their geographic distribution, geological periods, and phylo-
genetic links. As a result, it was possible to identify a new subfamily,
acquire new knowledge on generic and subgeneric grouping, and also
identify new taxa of the species range based on fossil material.

Below, we reproduce the classification of Spalacidae in which the
relation of individual groups of these animals to their present-day counter-
parts most correctly reflects their phylogenetic relationship.

Family Spalacidae Gray, 1821; Late Miocene-recent; Europe, Asia, North
Africa.
+Subfamily Prospalacinae subfam. nov.; Late and Middle Pliocene of
Europe.
+ Genus Prospalax Mehely, 1908; Late and Middle Pliocene of Central
and East Europe.

+P. priscus (Nehring, 1897); Middle and Late Pliocene; Polish

Carpathian, Czechoslovakia, South Hungary, Rumania (Tran-
sylvania).

132

ТР. rumanus Simionescu, 1930; Middle Pliocene (Astian); Ruma-
nia (lower reaches of Prut river), northwest Black Sea region of
the Soviet Union.

Subfamily Spalacinae Gray, 1821 ( = Spalacinae Thomas, 1897); Late
Miocene-recent; Europe, Asia, North Africa.
Genus Microspalax Nehring, 1897; Early Miocene-recent; Europe,
Asia and North Africa.
Subgenus Microspalax Nehring 1897; Late Miocene, Late Pliocene
of Europe; Pleistocene-recent of northeast Africa, Middle East
and partly Asia Minor.

M. ehrenbergi (Nehring, 1897); Pleistocene-recent; northern

regions of Libya and UAR, Israel, Jordan, Livan, Syria, Iraq,

possibly northern regions of Turkey.

ТМ. compositodontus sp. nov.; end of Late Miocene; northwest
Black Sea region of the Soviet Union.

ТМ. macoveii (Simiionescu, 1930); Middle Pliocene; northwest
Black Sea region of the Soviet Union and the adjoining regions
of Rumania (right bank of the Prut River in its lower reaches);

ТМ. odessanus sp. поу.; end of Middle Pliocene and Late Plio-
cene; northwest Black Sea region and the north Azov Sea region
of the Soviet Union.

Subgenus Mesospalax Mehely, 1909; recent; Transcaucasus; Asia
Minor, the Balkans, Carpathian regions of Hungary, Soviet Buko-
vina, northwest Black Sea region (Rumania, Bulgaria, Moldavian
SSR, Odessa region of the Ukraine SSR).

M. nehringi (Satunin, 1898); recent; Turkey, North Iraq, Trans-

caucasian region of the USSR. :

M. leucodon (Nordmann, 1840); recent; Yugoslavia, north

Greece, European Turkey, Bulgaria, Hungary, Rumania, Molda-

vian SSR, and the adjacent areas of the Odessa region of Ukraine

SSR, Soviet Bukovina.

Genus Spalax Giildenstaedt, 1770; Late Pliocene-recent; Eastern
Europe including cis-Caucasus and north Caspian, entering into
Transcaspian region.

S. giganteus Nehring, 1897; recent; semi-deserts of Caspian

regions of the northeast cis-Caucasus, north Caspian and Trans-

caspian regions.

S. arenarius Reshetnik, 1938; recent; left bank of lower Dnieper,

South of Kakhovka.

5. microphthalmus Gildenstaedt, 1770; Pleistocene-recent; terri-

tory between Dnieper and Volga except lower Dnieper, west

cis-Caucasus.

S. polonicus Mehely, 1909; Pleistocene-recent; right bank of

133

Ukraine, except its northernmost areas and the Soviet Bukovina.

S. graecus Nehring, 1898; recent; Soviet Bukovina and adjacent

regions of Rumania.

15. minor W. Topachevskii, 1959; Late Pliocene-Early Anthro-
pogene; northwest Black Sea and Azov Sea regions of the
Soviet Union.

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PART II
TAXONOMY

с да : м a | : ot i q | р
О и Tes: Е
f НИ {3 7 ey ‚+ р ее
2 % |
р :
i fi
у У.

KEY FOR IDENTIFICATION OF SUBFAMILIES
OF THE FAMILY SPALACIDAE

1 (2). The suborbital canal is always closed. On the frontal bones there
is a small supraorbital foramen near the external border of the orbit.

The alveolar process of the lower jaw is considerably shorter than

the articular. The angular process is situated at the base of the arti-

cular and has a common border with it. Sella externa is absent
о ple nee ER ee ao aR a a 1. Prospalacinae subfam. nov.

(Mid Pliocene and beginning of the Late Pliocene).

2 (1). The suborbital canal and the supraorbital foramen are always
absent. The alveolar process of the lower jaw exceeds in height

the articular one, or is approximately equal to the latter. The
angular process is placed outside and is on the external wall of the
alveolar process and does not have a common border with the
articulated member. Sella externa is always present...........
а .. 2. Spalacinae Gray.

(Late Miocene to present day).

1. Subfamily PROSPALACINAE W. Topachevskii subfam. nov.
ANCIENT MOLE RATS

Type genus. Prospalax Mehely, 1908; southern Poland, Czechoslo-
vakia, Hungary, Rumania, northwestern Black Sea regions of the Ukraine
SSR; Mid-Pliocene and beginning of Late Pliocene.

Diagnosis. The suborbital canal (bony canal for the branch of the
trigeminal nerve) is always closed (Figure 40, No. 2). The small for.
supraorbitalis is situated on the temporal bones near the external edges
of the orbit (Figure 40, No. 1). The alveolar process of the lower jaw is
considerably shorter than the articular one. The angular process is situated
on the base of the articular one and has a common border with it. Sella
externa is absent (Figure 40).

Additional description. Measurements are mostly small and close to
the measurements of the then-living M. ehrenbergi; the length of the upper
line of the permanent molars is, as a rule, less than 7.5 mm, and that of
the lower, 8.0 mm. The upper and lower distances are short. The masseter

154

area of the lower jaw is sharply defined. The lower incisors are relatively
narrow and are characterized by the presence of usually three (sometimes
two) prolonged ridges on the front side. The upper and lower permanent
molars are longer and narrower than in the representatives of the sub-
family Spalacinae Gray.

77/1

=
С
ee

Figure 40. Prospalax priscus (Nehr.).

A—axial skull, lateral view; B—the same, from above; C—the same, from
below; D, J—lower jaw, inner view; E—the same, from above; F, G—the
same, outer view; H—the same, posterior view; A to F—by Sulimski, 1964;
С to I—by Mehely, 1908. /—supraorbital foramen; 2—suborbital canal.

Comparison. They can be clearly differentiated from the representatives
of the subfamily Spalacinae by:

1. The usual presence of a closed infraorbital canal. It is always absent
in Spalacinae.

2. The usual presence of for. supraorbitalis on the temporal bones.
This is absent in Spalacinae.

3. The shorter alveolar process of the lower jaw is considerably less in
height than the articular one. In Spalacinae, the alveolar process is almost

155

equal in height to its articular one and, in the majority of cases, it notably
exceeds the latter.

4. The angular process is situated at the base of its articulated member,
having a common border with it (the posterior section of the lower jaw).
In Spalacinae the angular process is placed externally on the external wall
of the alveolar border and does not have a common border with the
articular process.

5. The absence of sella externa. This is always present in Spalacinae.

Formation of the subfamily. This is represented by the single genus,
Prospalax Mehely, 1908, from the Middle and Late Pliocene of Europe.

Distribution and geological age. Southern Poland (Prikarpate), Czecho-
slovakia, Hungary, Rumania, northwestern Black Sea region of the Ukraine
SSR (Odessa region); Mid-Pliocene and beginning of Late Pliocene.

1. Genus PROSPALAX Mehely, 1908—ANCIENT MOLE RATS

Mehely, 1908: 305-316, Table II, Figure 1-3; Table IV, Figure 1-3.

Genotype. Prospalax priscusNehring, 1897; south Hungary (Villan Moun-
tains), the Beremend near Villani, Committee of Baran; Late Pliocene.

Diagnosis. Same as for the subfamily.

Description and comparison. In addition to the traits described earlier
for the subfamily, the following special characteristics are typical for the
genus in respect of the structure of the permanent molars.

1. The protocone on M!? in the early and middle stages of wear is
always fused with the anterior collar and, along with the latter, is separated
from the rest of the parts of the crown in the shape of a kidney (Figure 41).
The paracone is largely fused with the hypocone, and the latter, in turn,
is fused with the metacone to form a V-shaped figure on wearing. The
fusion of the protocone with the hypocone in the later and final stages of
wearing does not occur independently as in representatives of present-day
mole rats (genera Microspalax and Spalax), but through the anterior
collar and paracone, as a result of which the worn out grinding surface
assumes either an S- or Z-like appearance. Subsequently, the tooth has
two open intruding folds in the outer line only at the unfused protocone
and hypocone and assumes an S- or Z-shaped appearance changing the
W-like appearance which is characteristic of all Spalacinae without excep-
tion though at only the very early stages of erosion.

2. A similar phenomenon is also observed on the two lower and last
permanent molars (M,_;), the hypoconid of which is fused with the
posterior collar in successive stages of erosion and is separated, along
with the latter, from the rest of the parts of the crown in the form of a
kidney, and the fusion, each with the protoconid of metaconid and
entoconid, forms a V-shaped figure due to wearing. The fusion of the

156

protoconid and hypoconid again does not take place independently as in
Microspalax and Spalax, but through the posterior collar thus giving the
S- or Z-shaped appearance of the mastication surfaces. All the permanent
molars in the later and final stages of erosion are, without exception,
generally similar to the permanent molars of Microspalax and Spalax, if
certain clear differences are not to be considered in the general proportions
of the crowns.

Figure 41. Prospalax priscus (Nehr.).

A—upper row of permanent molars (by Sulimski, 1964); B—incisor of lower
jaw (by Mehely, 1908); C—lower row of permanent molars; D to F—isolated
M, (by Sulimski, 1964); G—lower row of permanent molars
(by Mehely, 1908).

3. The structural folds are more predominantly present on all the
permanent molars without exception than in Microspalax and Spalax. In
addition, the molars of the representatives of the genus Prospalax are, in
general, rather simpler than in true mole rats.

Note. Considering the simplicity of the permanent molars of Prospalax,
and its weakly developed tuberculoid type of structure for the permanent
molars in the early stages of wear as compared to Microspalax and Spalax,
a deviation from the opinion of Mehely (1908) appears imminent, 1.е.,
not considering this given genus as a direct ancestor of true mole rats and
proposing for it a place in the adjacent branch in the family group which
was, in its time, indicated by Stehlin and Schaub (1951); Schaub, (1958). The
presence of remains of true mole rats along with the similar Prospalacinae
appears to be contradictory, and in some cases even the finds of the former
in rather older sediments than the most ancient sediments containing the

157

remains of Prospalax have been found. Thus, Гог example, the remains of
true mole rats are known to have occurred from the Upper Miocene-
meotes of the northwestern Black Sea region of the Ukraine SSR (please
see further, page 188). All the aforesaid proves that in the Mid-Late-
Pliocene of Europe, we come across only highly specialized last repre-
sentatives of the once most populous subfamily of ancient mole rats which
lived in ‘their time in regions where the more adaptive present-day mole
rat could not penetrate because of specific paleogeographical reasons. It
can also be assumed that Prospalacinae were more widely spread out in
the Miocene of Europe and possibly of north Africa, and Asia Minor,
and their origin may be traced in the Oligocene period. In addition, con-
sidering the intermediate position of the subfamily between the Oligocene
Rhizospalacinae and true mole rats, it is highly probable that one could
discover the direct ancestors of Spalacinae in this very subfamily among
ancient, yet unknown genera, less specialized than the only presently
known genus Prospalax. However, all this has to be decided in the future
as the study of the history of the group in the time prior to Mid-Pliocene
faces considerable difficulties related primarily to the non-availability of
paleontological material.

Composition of the genus. Two species—P. priscus (Nehring, 1897) from
the Middle and Late Pliocene of southern Poland, Czechoslovakia,
Hungary, and north Rumania, and P. rumanus (Simionescu, 1930) from
Mid-Pliocene of the Black Sea region of Rumania. Perhaps the remains
of Prospalax from the Mid-Pliocene of the northwestern Black Sea
region of Ukraine should be added to the last mentioned species (Kuchur-
gan sediments, stratigraphically identical and mixed territories with corres-
ponding sediments of Rumania in which the remains of P. rumanus have
been found).

Distribution and geological age. Southern Poland (Prikarpate), Czecho-
slovakia, Hungary, Rumania, northwestern Black Sea region of Ukraine
SSR (Odessa region); Mid-Pliocene and beginning of Late Pliocene.

KEY FOR IDENTIFICATION OF SPECIES
OF THE GENUS PROSPALAX

1 (2). Length of the angular process of the lower jaw is less than the total
О М teats seeks etek. cert 1. P. priscus (Nehring).
(Middle and Late Pliocene).

2 (1). Length of the angular process of the lower jaw exceeds the total
lenethwot ММ. 2. P. rumanus (Simionescu).
(Mid-Pliocene).

158

1. Prospalax priscus (Nehring, 1897)—Original Mole Rats
Nehring, 1897: 174-176, Abb. 4, Figure 3.

Holotype. Geological regulation in Budapest, No. 0 = 4722; the lower
jaw (mandibula sin), the preserved articular process, the angular and con-
siderable part of the alveolar process, and of the teeth—the incisor and
the anterior permanent molar; south Hungary (the place of the find is
Beremend, near Villani, Committee of Baran); Late Pliocene.

Diagnosis. The angular process of the lower jaw is short; its length is
less than the total length of the two anterior permanent molars (M,—M.).

Description. The measurements are medium, a little larger than the
then-living M. ehrenbergi; the length of the upper rows of the permanent
molars is 6.0-7.5 mm, and that of the lower ones is 6-8-9 mm. The
skull is narrowed in the molar region; the relation of the incisorial width
to the length of the row of permanent molars is 71.3. The rostral part is
wedge-shaped; its edges gradually close in anteriorly; the width of the
rostrum at the level of the anterior edges of the for. sub-orbitalis
exceeds the similar width in the middle. The nasal bones are shorter than
the supermaxillary bones and are bifurcated from behind (Figure 40). The
temporo-premaxillary sutures are directed outward and forward, forming
an angle, the apex of which is directed back with the temporo-nasal suture.
Along the borders of the temporal bones there are small for. sub-orbitalis.
The sagittal ridge on the temporal bones is absent. The upper diastema
is comparatively short. The magnitude of the diastema-tooth index is
151.0. The suborbital canal is always closed and in some instances it is
divided in two. The alveolar protuberances, as can be judged by the figure
given in the work of Sulimski (1964), are well expressed and are in imme-
diate proximity from the anterior edges of the alveolus М! when removed,
and are of considerably less length than the anterior permanent molar.
The masseter area is short; its length is perhaps less than the distance from
the anterior edge of the latter to the suture between the premaxillary and
maxillary bones. The hard palate is narrow at the level of the anterior
permanent molars, and its width is about equal to М". The middle ridge
of the palate is well developed and wide. The pillar-like process is large
and blunt. The fossae behind the palate are long and narrow.

М: (length 1.6-2.4-2.7 mm; width 1.3-1.7-2.1 mm) is long and
narrow, the ratio of the width to length is, on an average, 71.0; n = 93
(Sulimski 1964). In true mole rats, the magnitude of this index in all the
given cases is considerably greater than 80.0 or approaches to this value.
The protocone is fused with the anterior collar in the early and middle
stages of wearing, and is separated along with the latter from the rest of
the parts of the crown in the shape of a kidney. The paracone is usually
connected with the hypocone and the latter with the metacone; taken

159

together they form a V-shaped figure during erosion. At a given stage the
relationship of teeth is characterized by the presence of two outer and one
inner intruding fold; moreover, the anterior outer and inner folds form a
continuous fissure. During erosion, the anterior collar fuses with the
paracone as a result of which the masticatory surface assumes an S- or
Z-form. In this stage of wearing, the tooth has an intruding fold in both
the outer and inner lines; the inner line, because of the type of fusion
during erosion described above, deeply penetrates into the masticatory
surface and its inner portion is not separated into the anterior mark. The
length of the inner intruding fold in the just described stage of erosion
usually exceeds two-thirds the total length of the width of the crown,
whereas in true mole rats this measurement is about half the width of the
latter. The mesocone and posterior collar are always absent. There are
three molars—a large inner and two weakly developed outer.

M? (length 1.5-2.1-2.5 mm; width 1.3-1.8-2.2 mm) like the pre-
vious molar is, perhaps, relatively narrower than in true mole rats (the
ratio of crown width to its length is 85.7; n = 79; whereas in Spalacinae
the lowest values of the given index lay in the range of 90.0 and in the
majority of given instances, the width of the tooth exceeds its length). The
form of the wearing surface is S-shaped, quite similar to that of true mole
rats because the anterior collar is fused with the paracone and the latter,
in turn, with the hypocone. However the closure of the internal portion
of the intruding fold of the inner line in the anterior mark, which is
characteristic of the families of the genus Microspalax and Spalax in the
middle and late stages of erosion in corresponding teeth, perhaps does not
occur. The root structure is similar to that of the previous molar.

M? (length 1.2-1.6-2.0 mm; width 1.1-1.4-1.6 mm) like the pre-
vious permanent molars is, on an average, narrower than in true mole rats
(the ratio of the width to length is 87.5; и = 41) in which the width of the
crown of the tooth in the majority of cases exceeds its length (with the
exception of Mio-Pliocenic M. compositodontus and Mid-Pliocenic M.
тасоуей which also have comparatively narrow upper permanent molars).
М? is similar to the previous molar in the general outline of the grinding
surface. The number of roots in the majority of instances does not exceed
three—a large inner and two weakly developed outer. In individual cases,
there are remains of a small fourth external crust.

The lower jaw has a shortened diastema (the value of the diastema
tooth ratio is 66.0; 67.7) and a shortened angular process (length less than
the total length of the anterior permanent molars). The ridge dividing the
crown-alveoli, judged by the figures given in the work of Mehely (1908), is
low and blunt. The lower ridge of the masseter surface is large and forms
an acute angle (Figure 40) along with the prolongation of the anterior edge
of the incoming branch. The horizontal branch is comparatively not high;

160

its height at the level of the posterior edge of the alveoli of М, is less than
the length of the lower line of permanent molars. The mandibular foramen
is somewhat shifted toward the edge of the coronary articulating groove
and is situated far from the latter, a little exceeding half the length of the
condylus.

The lower incisor is comparatively narrow (ratio of the width to
antero-posterior cross section is 78.4; 80.8) with two to three longitudinal
ridges on the dorsal surface (Figure 41). Regarding general proportions
and details, the structure is very similar to the incisors of European Mio-
Pliocenic fossils differing only in the lesser absolute width.

М, (length 1.6-2.4-2.8 mm; width 1.3-1.7-2.0 mm) is long and
short (relation of width of crown to length is, on an average, 71.0; n =
122). The hypoconid and the posterior collar have been separated at very
early stages of erosion in the form of a kidney. Furthermore, the meta-
conid shows a tendency to separate from the protoconid in the same stage
of wearing on the crown of the tooth, or is completely separated from it.
It has to be noted, however, that in semi-mature individuals, a complete
fusion of the metaconid with the protoconid takes place, and also a for-
mation of a bridge between the fused hypoconid and the posterior collar
from one side, and between the rest of the parts of the crown on the other.
The entoconid is always well developed in the early and middle stages of
erosion and the mesoconid is always absent. It is clear from the foregoing
description that in P. priscus, immature individuals and those in the early
stage of maturation, M, is characterized by the presence of one intruding
fold in the outer line and two in the inner lines. Due to further erosion,
the intruding folds are closed in the marks in the following order: the
posterior inner (with formation of posterior mark), the anterior inner,
and finally the outer one. During this, the posterior mark usually com-
pletely vanishes with old age, the entoconid completely fuses with the
posterior collar, and the grinding surface clearly takes up a well-defined
S- o1 Z-form and further, an E-form (at the complete closure of the anterior
inner fold) and finally, an oval shape at the complete closure of the only
outer). It has to be stressed however that in P. priscus as, perhaps, in all
representatives of the genus, the formation of marks (stars) on permanent
molars takes place in somewhat later stages of erosion than in true mole
rats and, further, the complete closure of the outer intruding fold fades
away only in very old age. The tooth is characterized by having two roots.

М, (length 1.5-2.2-2.6 mm; width 1.2-2.0-2.2 mm) like the pre-
vious molar is, on an average, narrower than in true mole rats (relation
of width of crown to length is 90.9; n = 144). The hypoconid along with
the posterior collar is separated from the rest of the parts of the crown at
the initial and middle stages of erosion in the form of a kidney. The fusion
of metaconid, protoconid, and entoconid forms a V-like shape on erosion.

161

The tooth has one intruding fold at the indicated stage of wear in the outer
line, and two in the inner line; moreover, the posterior one is closer.
During further erosion, there is a reduction of the posterior inner intruding
fold because the entoconid fuses with the posterior collar and that is how
the anterior mark is formed—by the closure of the corresponding fold of
the inner line. As for the outer deep intruding fold, it perhaps remains
open almost up to very old age. The tooth, like the previous molar, is
characterized by the presence of two roots.

М. (length 1.3-2.0-2.2 mm; width 1.2-1.7-1.8 mm; relation of
width to length is, оп an average, 85.0; и = 65) is like M, in general,
differing from the latter only by small absolute dimensions.

Comparison. It differs from the Mid-Pliocenic P. rumanus by:

1. A shortened angular process of the lower jaw, the length of which
is less than the total length of М, to Mg. In P. rumanus it is longer than
the latter.

2. Average large absolute dimensions (length of lower rows of perma-
nent molars is 6.0-8.0-9.0 mm against 6.0; 6.2 in P. rumanus).

3. A wider lower incisor on an average (relation of width to the antero-
posterior cross section is 78.4; 80.8 against 68.6 in P. rumanus).

Measurements. Length of upper rows of permanent molars, 6.0-
7.5 mm; width of upper incisor, 1.7-1.9-2.2 mm; lower diastema,
4.4mm; length of row of permanent molars, 6.0-8.0-9.0 mm; height
of horizontal branch at level of posterior edge of alveolus of M,, 6.3 mm
externally; width of lower incisor, 1.6-1.8—2.1 mm; antero-posterior
cross section of lower incisor, 2.55 mm.

Note. The presence of a shortened angular process of the lower jaw
and comparatively wider lower incisors in P. priscus indicates, perhaps, a
higher degree of specialization in the species for digging activity as com-
pared to the Mid-Pliocenic P. rumanus.

Distribution and geological age. Poland (Prikarpate) (place of find
Venzhe near Dzyaloshina; Rembelitsi Krulavskie, Klobutskova uezda),
Czechoslovakia (Ivanovtsi near Trenchin), south Hungary (group of
places of finds in Villanski Mountains; Beremend, sites No. 4, 5, and 7;
Charnota, sites No. 1 to 3; Nad’khorshan’,:site No. 1 and Villan, sites
No. 3, 5 and 11—all in the Committee of Baran’; in addition to around
Hungary, the remains of this species have been found in the Late Pliocenic
fauna of Kushlang); Rumania (Transylvania; place of find, Beralt-Kepeni)
(Kretzoi, 1956; Kowalski, 1960b; Sulimski, 1964); Late and partly, per-
haps, Middle Pliocene. Remains of this species are not found around the
USSR. Information on this point available in literature is mainly based
on some uncertain findings; the remains belonging to P. priscus were
ultimately found to be those of M. macoveii after closer examination
(Simionescu). Details are given below (pages 199-200).

11

162

2. Prospalax rumanus (Simionescu, 1930)—Rumanian Mole rats
Simionescu, 1930: 20, 21; Figures 29 and 30; Tab. II, 2.

Holotype. University in Yassakh (Rumania), number of the find has
not been fixed; the lower mandible (mandibula sin.) without the rising
branch, the angular process has been preserved and also the two per-
manent molars (M,—-M,) (Simionescu, 1930). Rumania with Malushtein;
Mid-Pliocene.

Additional data. Lower mandible from the Kuchurganskii sediments
without the rising branch and the angular process, preserved incisor and
complete line of alveoli of permanent molars; S. Novopetrovka of Frun-
zanskii region near Odessa; Mid-Pliocene. It is preserved in the collec-
tions of the Zoological Institute AN Ukraine SSR. The jaw was found
during the paleontological expedition of the Zoological Institute AN
Ukraine SSR in 1964, and is actually the only authentic find of remains
belonging to representatives of the genus Prospalax in the USSR.

Diagnosis. The angular process of the lower jaw is elongated; its length
exceeds the total length of the two anterior permanent molars (M,—M.,).

Description. The measurement are, on the average, smaller than those
of the previous species. The alveolar length of the lower row of permanent
molars is 6.0, 6.2 mm. The lower dias-
tema, as in P. priscus, is shortened; the
value of the diastema-tooth index is
66.7 (holotype) and 74.3. The angular
process is long; its length considerably
exceeds the total length of M,—M,. The
structure of the masseter area is the
same as that of P. priscus. The lower
incisor is, on the average, perhaps com-
paratively narrower than the one found
in previous species; the relation of the
width to the antero-posterior cross
section is 68.6. There are three longi-
tudinal ridges on the anterior surface.
Unfortunately, the lower permanent
molars in all the specimens known at
present of this species are considerably
worn out (Figure 42), i.e., they are in
Figure 42. Prospalax rumanus Sim. such a stage of erosion that it is iy

(by Simionescu, 1930). difficult to determine the species differ-
: 5 ences. From the general appearance, the
A—lower jaw, external view, holo- С т
type: B—lower rows of permanent grinding surfaces are very similar to the
molars. permanent molars of P. priscus.

163

Comparison. Completely given on page 161.

Measurements. Length of lower row of permanent molars 6.0, 6.2 mm;
length of lower diastema 4.0, 4.6 mm; height of horizontal branch at the
level of the posterior edge of alveolus of M, from outside, 5.0, 5.8 mm;
thickness of the horizontal branch at the level of М,, 3.0, 3.3 mm; width
of lower incisor, 1.5 mm; antero-posterior cross section of lower incisor,
2.2 mm.

Note. This species in comparison with P. priscus has nearly all the
above-mentioned peculiarities in the construction of the angular process
of the lower jaw and incisors which, perhaps, points to its lesser special-
ization toward a burrowing type of life.

Distribution and geological age. Mid-Pliocene of northwest Black Sea
region (Odessa), Kuchurganskii sediments and its analogues around
mixed regions of Rumania (Malushteni Levoberezh’e (left bank) of the
Pruta River along its lower current).

2. Subfamily SPALACINAE Gray, 1821
TRUE MOLE RATS

Type genus. Spalax Giildenstaedt, 1770; the steppes and forest steppes
of Eastern Europe from the northwestern regions of Rumania, Soviet
Bukovina and eastern regions of the Pre-Caspian to east of the Ural
River and Trans-Caspian; Late Pliocene to present day.

Diagnosis. The suborbital canal and the supraorbital foramen are
always absent. The alveolar process of the lower jaw in the majority of
cases considerably exceeds the articular process in height or is approx-
imately equal to it. The angular process is constricted from outside, and
being on the external wall of the alveolar process, does not have a common
edge with the articular one. Sella externa is always present.

Additional description. The measurements are mainly average and
large. The upper and lower diastemata are elongated. The masseter area
of the lower jaw is without a sharply defined ridge. The lower incisor is,
on the average, relatively wider; in the majority of cases it is without a
longitudinal ridge on the anterior surface (present only in representatives
of the most primitive subgenus Microspalax Nehring—the then-living M.
ehrenbergi and its Mio-pliocene fossil representatives). The upper and
lower permanent molars are shorter and wider than in the species from
the subfamily Prospalacinae.

Comparison. The comparison of the subfamily has been given fully
on page 154.

Composition of the subfamily. This subfamily is represented by two
recent genera—Microspalax Nehring, 1897; and Spalax Giildenstaedt,
1770.

164

Distribution and geological age. North Africa (northern region of
Libya and United Arab Republic), Asia Minor (Israel, Jordan, Lebanon,
Syria, Iraq, Turkey, Soviet Zakavkaz, and its southwestern regions), south-
eastern Europe, from Balkan and Pre-Balkan regions in the west, up to
the Volga on the east Pregkavkaze, the northern Pre-Caspian region up
to east of the Ural River and in Zakaspii; Late Miocene to present day.

KEY FOR IDENTIFICATION OF THE GENERA
OF THE SUBFAMILY SPALACINAE

A—Based on the skull

1 (2). The for. supracondyloideum is always present though it is above
one of the occipital condyles, usually above both. The tuberculum
pharyngeum laterale are broad; being broad, they occupy almost
all the place between the auditory bulbe at the place of contact of
the basal wedge and the base of the occipital bone (Figure 43).
The base of the skull has a sharply defined fissure because the
basis-phenoid and the base of the occipital bone are situated at
ап арен 1. Microspalax Nehring.

(Late Miocene to present day).

av
АИ

hee,
А

Figure 43. Base of the skull. х2.75.

A—Spalax; B—Microspalax. 1—lateral occipital tubercles.*

*Probably a mistake in the original. By all accounts this refers to the lateral pharyngeal
tubercle—Editor.

2 (1).

1 (2).

Day

165

For. supracondyloideum is always absent. The tuberculum pharyn-
geum laterale are compact, stretched in the shape of narrow ridges
along the edges of the basic wedge-shaped bone and the base of
the occipital bone; the base of the skull is concave and V-shaped.
The basisphenoid and the base of the occipital bone lie on one level
because of which the fissure in the base of the skull is not defined.
И OAR REE SS Ie BS 2. Spalax Giildenstaedt.

(Late Pliocene to present day).

B—Based on the lower jaw

The ridge of the coronary-alveolar groove is hardly defined; it is
blunt or is absolutely unidentifiable. The depression (between
ridges of the coronary-alveolar and coronary-articular process) is
not deep, usually opening anteriorly and externally. The angular
process is well separated and is inclined from the external wall of
the alveolar process. The area on its external surface is represented
by only a prolongation of its free edge and actually restricts the
place of attachment of the posterior portion of the musculus mas-
seter lateralis (Figure 61). The sella externa is placed below the sella
mtemmar(PISUneva4 i wi era cere eteeile © = 1. Microspalax Nehring.

Figure 44. Lower jaw, posterior view. х 72/5)

A—Microspalax; B—Spalax. se—sella externa;
si—sella interna.

The ridge of the coronary-alveolar groove is strongly developed
and is sharp. The fossa between the ridges is deep and is always
closed. The angular process completely adheres to the alveolar
process and is slightly inclined from the external wall of the latter.
The area on its external surface is exhibited all along its free edge
including the zones of attachment of the posterior as well as anterior

166

1 (2).

portions of the musculus masseter lateralis. The sella externa is
placed approximately at the same level as the sella interna........
SEU Dal koe rea ales Па Г. 2. Spalax Giildenstaedt.

C—Based on the vertebrae

The antero-posterior length of the dorsal arch of the first cervical
vertebra—the atlas—is less than the height of the canal for the
medula oblongata measured at the anterior side. The length of the
neural spine of the second cervical vertebra—axis—measured from
the anterior end, less than twice exceeds its least width (Figures 45
and 46). The 4th to 5th sacral vertebrae are always in contact (either

И, Lt
| Die:

И
4

I, \. wll al

Figure 45. Atlas. x 3.6.

A, B—Spalax; С, D—Microspalax; A, C—anterior view;
B, D—from dorsal arch.

KS
Yay: RS

ИИ,

Figure 46. Axis, anterior view. x 3.7.

A—Spalax; B—Microspalax.

Bel):

1n(2).

2 (1).

167

fuse or touch each other) with the spina ischiadica of the pelvic
bone as a result of which the large sacral groove along with the
sacrum forms a closed opening (Figure 49).................-...
И Bae ei eC И 1. Microspalax Nehring.
The antero-posterior length of the dorsal arch of the first cervical
vertebra—the atlas—is approximately equal to the height of the
canal for the medula oblongata. The length of the neural spine of
the second cervical vertebra—the axis—twice or more exceeds the
least width of this process. The sacrum never comes into contact
with the spina ischiadica of the pelvic bone and, as a result, the
large ischial groove is open from behind.............--+..++++-

D—Based on the scapula

The medial surface of the bone is flattened anteriorly (in the neck
region). Its caudal edge is not wide because the caudal ridge (crista
caudalis) is weakly developed; the maximum length of the caudal
edge is more than three and a half times less than the maximum
width of the scapula. The width of the acromion process is more
than twice less its length (Figure 47)...... 1. Microspalax Nehring.
The medial surface of the bone is highly concave anteriorly. Its
caudal edge is broadened because of the great development of the
caudal ridge. The maximum height of the caudal ridge is only three
times less than the maximum width of the scapula. The width of

У 3
"7.

ПИР
jj YY dle

———

з B
Figure 47. Scapula. x 1.7.
A, C, E—Spalax; B, D, F—Microspalax; A, B—from the side of the articulating

fossa; C, D—from the side of the caudal tubercle; E, F—from lateral sides.

168

1 (2).

2 (1),

the acromion process is less than twice or more its length.........
i ATEN, Seat Te art eae 2. Spalax Giildenstaedt.

E—Based on the humerus and bones of the forearm

The width of the diaphysis of the humerus is greater than the
deltoid process by approximately one and a half times the antero-
posterior cross section measured at the same level (Figure 48). The
maximum width of the proximal epiphysis of the olecranon of the
elbow bone is less than the length of this process. The maximum
width of the crescent-shaped groove at the level of the ulna joint

Figure 48. Humerus,
anterior view. х 1.7.

A—Spalax ;
B—Microspalax.

is approximately equal to its width at the level of the lower border
of the coracoideus process. The least width of the ulna at the base
of the proximal epiphysis is twice less than the width of the latter.
The maximum width of the distal epiphysis of this bone is less
than the width of the proximal epiphysis or is approximately equal
р eer 1. Microspalax Nehring.
The width of the diaphysis of the humerus is greater than the
deltoid process. It is always more than 2.5 times the antero-posterior
cross section. The maximum width of the proximal epiphysis of the
olecranon process of the radius* is less than 2.5 times the length
of the olecranon. The maximum width of the crescent-shaped
groove at the level of the ulna joint always exceeds the same at the
level of the lower border of the coracoideus process. The least
width of the ulna is about twice less than the width of the proximal
epiphysis. The maximum width of the distal epiphysis of this bone
always exceeds the similar width of the proximal epiphysis.......
а Mee cate mgmt tc SOs rene omireaier 2. Spalax Giildenstaedt.

*Should read ulna—Editor.

169

F—Based on the pelvic bones

1 (2). The length of the ilium (measured up to the anterior edge of the ar-
ticulating cavity) considerably exceeds the length of the ischium (by
more than half the length of acetabulum). Measurements of spina
ischiadica and tuber ischiadicus approximately coincide. The ischial
axis always contacts the wings of the sacrum as a result of which
the great ischial groove, along with the sacrum, forms a closed
opening, (Bisurer49) nai ie oe ee. 1. Microspalax Nehring.

2 (1). The length of the ilium is about equal to the length of the
ischium (even if it exceeds the latter, it does not do so more than
half the length of the acetabulum). Measurements of the ischial
axis are half or even less than those for the tuber ischium.
Because of this, the ischium never contacts the wings of the sacrum

ААммии" *

и
TF

ИЯ
SS

Figure 49. Pelvic bones and sacrum. Х 1.6.

A, B—Spalax; C, D—Microspalax; A, C—from above; B, D—lateral view.

170

and the large ischial groove is not closed posteriorly.............
ее. 2. Spalax Giildenstaedt.

G—Based on the femur, knee joint, and bones
of the tarsus

1 (2). The width of the diaphysis of the femur at its narrowest part less
than one and a half times exceeds its antero-posterior cross section
at the same level. The width of the bone at the level above the arti-
culating process is less than the intercondylary space or is approx-
imately equal to it (measured between the external edges of the
condyles). The length of the knee joint exceeds the width more than
twice. The crista tibiae is massive and sharp all along. The medial
ridge is absent or is faintly defined. The width of the proximal
epiphysis of the fibula is two-thirds (or even less) of the width
of the proximal epiphysis of the аа. 4.8.72... ae eee
т 1. Microspalax Nehring.

2 (1). The width of the diaphysis of the femur exceeds at its narrowest
part one and a half times and more the antero-posterior cross section
at the same level. The width of the bone at the level of processes
above articulation always exceeds the intercondylary width. The
length of the knee joint exceeds its width not more than two times.
The crista tibiae in all the given cases is absent or is rarely faintly
defined. The medial ridge is well developed and is sharp. The width
of the proximal diaphysis of the fibula is two and a half times less
than the width of the proximal epiphysis of the tibia.............
о 2. Spalax Giildenstaedt.

1. Genus MICROSPALAX Nehring, 1897—SMALL MOLE RAT

Nehring, 1897: 168 (nomen nudum); Mehely, 1909: 22-25. Nannospalax Palmer, 1903,
Sci. vol. XVII: 873 (nomen praeocupatum). Ujhlyiana Strand, 1922: 142. Pliospalax
Kormos, 1932: 194-198, Abb. 1.

Genotype. Spalax* ehrenbergi Nehring, 1897; present day; eastern
Mediterranean.

Diagnosis. The for. supracondyloideum is always present though it is
above one of the occipital condyles, or usually above both. The tuber-
culum pharyngeum laterale are wide; they occupy almost all the space
by width between the auditory bullae at the place of contact of the basal
wedge and the base of the occipital bones (Figure 43). The base of the
skull is concave because the basisphenoid and the base of the occipital
bone are arranged at an angle. The auditory foramens are large. The

*Should be Microspalax ehrenbergi—Editor.

171

length of the auditory bulla exceeds less than four times the largest dia-
meter of the auditory foramen, usually 3.5 times (3.1-3.5-3.9). The lower
portion of the lacrimal fossa in the majority of cases is pushed below the
upper edge of the malar process of the mandibular bone, or is situated on
the same level as the latter. The skull is placed low; its height at the level
of the anterior edge of МЗ 1$ half or even less than the length from the
nasal bone up to the apex of the occipital process. The parietal bones
form either a perpendicular trapezium or are at least triangular. The
sagittal ridge is long; its height is only about one and a half times less
than the length of the nasal bones (1.3-1.5-1.8) and concave (subgenus
Mesospalax). In case the sagittal ridge is short (length of nasalia exceeds
its length thrice or more), then there appear three longitudinal ridges of
enamel (subgenus Microspalax) on the lower incisor. The ridge of the
coronary-alveolar groove of the lower jaw (situated on the upper edge of
the alveolar process all along its anterior half) is hardly defined, blunt,
or is not marked absolutely (Figure 50). The fossa between the ridges
(coronary-alveolar and the coronary-articular) is shallow and is usually
open anteriorly and externally. The angular process is well separated and
inclined from the external wall of the alveolar and in the majority of
cases is a sharpened process at the end and considerably projects back in
relation to the proc. alveolaris; its apex in mature and aged individuals
is, as a rule, situated behind the posterior wall of the alveolar process or
is situated at the level of the latter. The area on the external surface of the
angular process is represented only along an inconsiderable length of its
edge (near the apex actually) contouring only the place of attachment of
the posterior portion of the musculus masseter lateralis. The sella externa
is situated considerably below the sella interna. The alveolar process is
placed low; its height at the inner edge in mature and aged animals is
almost always less than the length of the lower row of permanent molars
or is approximately equal to it. The dorsal arch of the first cervical ver-
tebra (atlas) is narrower and has remnants of a neural spine in the shape
of a bifurcated knob; its antero-posterior length is usually less than the
height (anterior) of the canal for the medula oblongata. The neural spine
of the second cervical vertebra (axis) is wide and low; its length, measured
along the anterior border, exceeds its least width by less than twice. The
neural spines of the thoracic vertebrae are short and wide. The sacrum
is not ossified in the posterior portion; its width exceeds anteriorly less
than thrice the same in the region of the fifth sacral vertebra. The neural
spines and transverse processes are fused and form dorsal and transverse
ridges (wings). The fifth sacral vertebra in males and females always
contacts the spina ischiadica of the pelvic bone (comes in contact in
females and fuses in males), as a result of which the large ischial groove
is closed from behind (Figure 49). The medial surface of the scapula is

172

flattened anteriorly. Its caudal edge is not widened because of a weakly
developed crista caudalis; the maximum height of the caudal edge is more
than three and a half times less than the maximum width of the scapula
(3.6-3.9-4.6). The acromion ridge in mature and aged individuals is step-
shaped, because the acromion tubercle (tuber spinae) is clearly defined
(Figure 47). The acromion process is narrow; its width is more than twice
less than its length. The cranial edge of the scapula has a sharp projection
because its anterior and posterior cuts are equally well developed. The
diaphysis of the shoulder bone is slightly flattened in the antero-posterior
direction; its width is more than the proc. deltoideus (the free part of the
crista tuberculi majoris) and approximately two and a half times exceeds
the antero-posterior cross section measured at the same level (1.3—1.4—1.6).
The deltoid process itself is, on an average, relatively longer and lower
than in representatives of the genus Spalax; its lateral edge is, as a rule,
situated at about the same level with similar lateral condyles, less bent,
and the extent of the base always exceeds the distal width of the bone
(measured from the lateral edge of the distal block up to the most pro-
truding medial point of the medial condyle). The medial condyle is short
and not wide; its length (slanting measurement) and the antero-posterior
cross section (measured from the anterior edge of the medial portion of
the block) only slightly exceeds half of the posterior width of the distal
block. The elbow process of the elbow bone is constricted from above.
The maximum width of its proximal epiphysis is greater than the length
of the olecranon more than 2.5 times (2.6-2.7-2.9). The maximum width
of the crescent-like groove at the level of the ulna joint is approximately
equal to the width at the level of the edge of the proc. coronoideus because
the proc. coronoideus ulnae is weakly developed. Furthermore, the ole-
cranon is, on an average, shorter than in Spalax. The lateral fossa—the
place of attachment of the long abductor of the pollux (M. abductor
pollicus longus) and the M. extensor pollicus longus—is deep and clearly
defined ; its upper edge goes behind the lower edge of the proc. coronoideus
at a distance approximately equal to the height of the crescent-like groove.
The radius is, on an average, more slender than in representatives of the
genus Spalax; its least width (at the base of the proximal epiphysis) is
less than half the width of the latter (2.2-2.4-2.6). The distal epiphysis
is weakly widened; its greatest width is less than the width of the proximal
epiphysis or is approximately equal to it. The ilium is elongated in length
(measured up to the anterior edge of the articulating process) and signi-
ficantly exceeds the length of the ishium. The for. obturatum is large
(Figure 49); its length exceeds the length of the articulating fossa or is
approximately equal to the latter. Measurements of the spina ischiadica
and of the tuber ischiadicus approximately coincide. As has been said
before, the spina ischiadica always coalesces (in males) or touches

Wie.

(in females) with the wings of the sacrum. The femur has a diaphysis
which is narrow and slightly flattened antero-posteriorly; the width of
the bone at its narrowest less than one and a half times exceeds the antero-
posterior cross section at the same level (1.0-1.2-1.4). The tubercles above
the articulation are weakly developed; the width of the bone at the tuber-
cles in the majority of cases is less than the width between condyles, or is
approximately equal to it. The knee joint is long and narrow; its length
more than twice exceeds the width. The crista tibiae is massive and sharp
all along. The medial ridge is absent or is faintly defined. The anterior
bend of the bone is more sharply defined than in representatives of the
genus Spalax. The proximal epiphysis of the fibula is widened; its width
is one and a half times less than the width of the proximal epiphysis of
the tibia (1.2-1.3-1.5). The symphysis of the tibia and fibula is short,
about two and a half times less than the full length of the tibia (2.3-2.5-
2.8). The free portion of the fibula is bent back externally more sharply
than in all the species of the genus Spalax.

Comparison. The differences between the genera Microspalax and
Spalax stand out clearly if their diagnostic characteristics are compared.
In addition to the characteristics noted in these pages, representatives of
the genus Microspalax differ, on an average, from species of the genus
Spalax by small absolute measurements, by shortened upper and lower
diastemata, by compact (narrowed) upper and lower incisors, and also
by more complicated wearing surfaces on permanent molars, espe-
cially the front ones, in the majority of cases cited. At the same time, the
amount of reduction in roots of permanent molars is exhibited to a lesser
degree than in species of the genus Spalax.

Composition of the genus. Two subgenera—Microspalax Nehring,
1897, and Mesospalax Mehely, 1909, with three present-day and three
fossilized Mio-Pliocenic species: M. ehrenbergi Nehr., 1897; M. composi-
todontus sp. nov.; M. macoveii (Simionescu, 1930); M. odessanus sp. nov.;
M. nehringi (Satunin, 1898); M. leucodon (Nordmann, 1840).

Until recently, the small mole rats from the subgenera Microspalax
and Mesospalax were taken to be under the genus Spalax. However, the
differences in the structure of the skull, lower jaw, and bones of the post-
cranial skeleton of these animals are so clear cut and great that their
separation into independent genus, in our opinion, is well deserved.

Distribution and geological age. Eastern Mediterranean (northern
Libya, Syria), Asia Minor (Turkey, Iraq), Soviet Trans-Caucasus, Balkan
and Pre-Balkan regions (Yugoslavia, Hungary, Greece, Bulgaria, and
European Turkey), northwest Black Sea region (Rumania, Moldavian
SSR, Odessa region of the Ukraine, SSR), Prikarpate of Hungary,
Rumania, and Chernovits region of Ukraine SSR (Soviet Bukovina);
modern. Late Miocene—the Middle and Late Pliocene of the north-

174

western Black Sea region (Rumania, Moldavian SSR, Odessa, Nikolaev,
and Kherson regions of the Ukraine), Azov region of Ukraine SSR.

KEY FOR IDENTIFICATION OF SUBGENERA
OF MICROSPALAX

1 (2). The lower incisor has three longitudinal ridges on the anterior
surface. The lambdoid and sagittal ridges are weakly developed
even in the mature and aged. The sagittal ridge is represented only
on the parietal bones and is faintly defined on the temporal bone.
The width of both parietals approximately exceeds thrice the length
of the upper row of permanent molars. The width of each of the
parietal bones in mature and old individuals is approximately equal
to its length, or even appreciably exceeds that of the latter. The
alveolar process of the lower jaw is about equal to the articular one
ia Пе 1. Microspalax Nehring.

(Late Miocene to present day).

2 (1). The anterior surface of the lower incisor is smooth without longi-
tudinal ridges. The lambdoid and sagittal ridges in mature and old
individuals are well developed; the sagittal ridge is present equally
on the parietal and temporal bones. The width of both parietals
exceeds significantly less than twice the length of the upper line of
permanent molars; the width of each of the parietal bones in mature
and old individuals is quite less than its length. The alveolar process
of the lower jaw significantly exceeds the articular one in height.
о. 2. Mesospalax Mehely.

(Holocene, including the recent period).

1. Subgenus MICROSPALAX Nehring, 1897

Nehring, 1897: 168. Nannospalax Palmer, 1903, Sci., vol. XVII: 873. Pliospalax Kormos,
1932: 194-198.

Genotype. Spalax* ehrenbergi Nehring, 1897; present day; eastern
Mediterranean (northern regions of Libya and United Arab Republic,
Israel, Jordan, Lebanon, Syria, southern regions of Turkey).

Diagnosis. The subgenus contains the smallest representatives of the
subfamily Spalacinae. The lower incisors have three longitudinal ridges
on the anterior surface. The lambdoid and sagittal processes of the skull
are weakly developed even in adult and old individuals; the sagittal ridge
is represented only on the parietal bones and is hardly defined on the
temporal. The parietal bones are quite wide; the width of the parietale

*Should be Microspalax ehrenbergi—Editor.

175

approximately exceeds twice the length of the upper row of permanent
molars. In addition, the width of each of the parietal bones in adult and
old individuals is about equal to its length or even appreciably exceeds
the latter. The alveolar process of the lower jaw is low, and is about equal
to the articular one in height.

Comparison. Microspalax Nehring, 1897 differs from representatives
of the subgenus Mesospalax by:

1. Permanent presence of three longitudinal ridges on the anterior
surface of the lower incisors. These are always absent in Mesospalax.

2. Weakly developed lambdoid and sagittal ridges. In Mesospalax the
corresponding ridges are developed significantly stronger; moreover, the
sagittal one in mature and old individuals is present on the parietal as
well as on the temporal bones.

3. Widened parietal bones. In Mesospalax the width of the parietale
in mature and old individuals less than twice exceeds the length of the
upper row of permanent molars, and the width of each parietal bone is
considerably less than its length.

4. A low alveolar process which is about the same height as the arti-
cular one. In Mesospalax, the alveolar process is considerably higher up
than the articular one. The relation of height in the alveolar process to
the condylary length of the lower jaw is equal to 9.0-15.3—21.0 in Micro-
spalax, as against 12.3-20.0-26.5 in Mesospalax.

Differences between Microspalax and Mesospalax are also found in
the average values of the proportions of the following sections of the
skull and lower jaw:

1. The occipital bone is relatively lower (the relation of its height to
the condylobasal length is 30.0-33.3-37.0 against 31.0-43.4-51.0 in Meso-
spalax).

2. The upper diastema is shorter (the value of the diastema-tooth
relation is 141.4-179.4-221.5 as against 160.0-206.1-280.3).

3. The nasal bones are relatively narrower (the relation of their width
to the length of the permanent molar rows 15 62.6-72.6-79.7 as against
67.1-83.0-100.0).

4. The molar width is less (its relation to the condylobasal length is
70.0-72.0-75.0 as against 72.0—77.2-83.0).

5. The МЗ is comparatively longer and narrower (relation of length
of МЗ to the same in the preceding molar, and width of the third per-
manent molar to its length is equal to 70.8-87.3-105.0 and 72.2-102.8-
123.5 against respectively 56.0-78.0-100.0 and 88.2-108.9-125.0).

6. The lower diastema is relatively shorter (the value of the diastema-
tooth index is 61.5-75.0-93.4 as against 70.0-89.6-125.4).

Composition of the subgenus. One present-day and three fossil Mio-
Pliocenic species—M. ehrenbergi (Nehr., 1897), М. compositodontus sp.

176

поу., М. тасоуей (Simionescu, 1930), and М. odessanus sp. nov.

Distribution and geological age. Eastern Mediterranean (northern
regions of United Arab Republic, Libya, Israel, Jordan, Lebanon, Syria,
Iraq, and possibly the southern regions of Turkey); present-day; Late
Miocene; Middle and partly Late Pliocene, northwestern Black Sea region
(Rumania, Moldavian SSR, around the Black Sea, and regions around
the Azov in the Ukraine).

1 (2).

Di):

3 (4).

4 (3).

5 (6).

KEY FOR IDENTIFICATION OF SPECIES OF THE
SUBGENUS MICROSPALAX

The upper incisors have two longitudinal ridges on the anterior
surface. The nasal bones have a sharply defined longitudinal slit-like
depression in the region of the sutures between them. The sym-
physis tubercle of the lower jaw is flattened, the mandibular angle
is weakly defined, and the angular process is slightly bent downward.
BE eI se an - 1. M. ehrenbergi (Nehring).
: (Holocene, including recent).
The anterior surface of the upper incisors is smooth and devoid
of longitudinal ridges. The nasal bones have no longitudinal slit-
like depression (being smooth or a little concave). The symphysis
tubercle of the lower jaw is sharply defined, the mandibular angle
is well developed, the angular process is sharply bent downward.
The mesocone оп М! is well developed in almost all stages of tooth
erosion (vanishes only in very old age). The entoconid on М, is not
fused with the posterior collar, the posterior mark is absent until
very old age; separate from the metaconid and entoconid, the
well-developed mesoconid is always present and, along with the
latter, forms a characteristic inner fork, the neck width of which
exceeds one-third the general length of the wearing surface of the
tooth or is about equal to the last one (Figure 6). МЗ has three roots.
sar Satna ae eects 2. M. compositodontus W. Topachevskii, sp. nov.
(Late Miocene).
The mesocone оп M! is always absent. The entoconid on М! is
fused with the posterior collar in old age, as a result of which the
posterior intruding fold of the inner line forms a posterior mark;
the mesoconid is not fully developed (the free mesoconid is found
in some species in young age; however, in this case the width of
the neck of the internal fork does not exceed one-fourth the total
length of the wearing surfaces of the tooth). МЗ has two roots.
The width of the hard palate between М! is less than the width of
the alveoli of the anterior permanent molar or is about equal to it;

Wi

the central ridge of the palate is faint, in the shape of a slender
cylinder, or is totally absent. M, has an independent mesoconid
(in the young) or an anterior mark (in semi-mature and mature);
the width of the neck of the inner fork is about one-fourth the total
length of the grinding surface of the tooth; the posterior mark
appears only in the mature. The symphysis tubercle of the lower
jaw is short; its length is approximately equal to the two similar
anterior permanent molars........ 3. М. шасоуей (Simionescu).
(First half of Mid-Pliocene).

6 (5). The width of the hard palate between M, exceeds the width of the
alveolus of the anterior permanent molar; the central ridge of the
palate is larger and wider. The mesoconid on M, is not fully dev-
eloped, the anterior mark is absent; the width of the neck of the
internal fork (if it is present at all) is considerably less than one-
fourth the total length of the grinding surface of the tooth; the
posterior mark is present in all stages of wearing (with the excep-
tion of very young individuals) (Figure 60). The symphysis tubercle
of the lower jaw is elongated; its length is about equal to the length
оазис votepermanent molars ее.
= SRR a ER ERM er Re AED 4. М. odessanus W. Topachevskii, sp. nov.
(Second half of Middle and Late Pliocene).

1. Microspalax ehrenbergi (Nehring, 1897)—Ehrenberg Mole Rat

Spalax ehrenbergi Nehring, 1897: 178-180. S. typhlus Fritsch, 1893, Abhandl. Natur-
forsch. Gesellsch. Halle: 79, 80 (nomen praeocupatum). S. kirgisorum Nehring, 1897:
176-178, Abb. 5. 5. aegyptiacus Nehring, 1897: 180, 181. S. intermedius Nehring, 1897:
181-183. 5. Fritschi Nehring, 1902: 78-87, Figure 1, 5. berytensis Miller, 1903: 162.

Holotype. Institute of special Zoology and Zoological Museum of the
University of Humboldt in Berlin, No. 5119 (Nehring, 1897: 178, Abb. 6);
described from the spirit-preserved specimen from the vicinity of Tel-Aviv
(israel).

Material investigated. Thirty skulls and skins obtained around Egypt,
Syria, Lebanon, Jordan, and southern regions of Turkey. They are pre-
served in the collections of the Zoological Museum of the University of
Humboldt in Berlin, the Paris National Museum, and the Zoological
Institute of the Academy of Sciences of the USSR.

Diagnosis. This is the smallest of the known representatives of the
subfamily Spalacinae (length of body, 130 to 160mm; condylobasal
length of skull, 31.0-38.1-43.9 mm; length of upper row of permanent
molars, 6.5-7.4-8.3 mm; length of lower row of permanent molars,
6.4-7.3-7.9 mm). The upper incisors have two longitudinal ridges
on the anterior surface. The nasal bones have a sharply defined longitudinal
slit-like depression in the region of the sutures between them. The temporo-

12

178

nasal and temporo-maxillary sutures form a clear angle with а backwardly-
directed apex.

The hard palate between M! is narrow; its width is approximately
equal to the width of the alveoli of the anterior permanent molars. The
central ridge of the palate is well developed and slightly widened. The
mesocone on МГ? and mesoconid on М, is always absent. The coales-
cence of the entoconid with the metaconid does not take place until old _
age, as a result of which the anterior mark is absent in young, semi-mature,
and mature individuals. The entoconid of this tooth is not fused with the
posterior collar until old age; the posterior mark is absent, almost through-
out life.

Description. The skull is wide in the infraorbital and narrowed in the
incisorial and rostral parts (the relation of the infraorbital, incisorial and
rostral width to the length of the upper row of permanent molars is equal
to 78.9-96.4-110.6, 69.2-76.4-86.1, and 97.3-108.6-126.0) with a те-
latively short diastema (value of diastema-tooth index is 141.4-179.4—
213.5). The nasal bones are narrow with a sharply defined slit-like longi-
tudinal depression (the relation of their width to the length of the lines
of permanent molars is 62.6-72.6-79.7). The temporo-nasal and temporo-
maxillary sutures form an angle with a backward-directed apex. The nasal
opening is high and narrow (relation of its width to the length of lines
of permanent molars is 49.3—60.2—66.7; of height to width, 61.0-73.3-81.6).
The palate at the level of M! is narrow (its width is approximately equal
to that of the alveoli of the anterior permanent molars). The central ridge
of the palate is well defined and is slightly broad. The foramens behind
the palate are clearly marked throughout the life span. The cut behind
the palate is wide; its width is approximately equal to the length of the
third permanent molar. The molar arches are constricted; the relation of
the molar width to the condylobasal length is 70.0—72.0-75.0. The parietal
bones are wide; the width of the parietale measured up to the lambdoid
ridge approximately exceeds twice the length of the permanent molars;
the width of each of the parietal bones in mature and old individuals is
approximately equal to its length or even considerably exceeds the latter
(Figure 50). The lambdoid and sagittal ridges in mature and old indivi-
duals are weakly developed; moreover, the latter is clearly defined only
on the parietal bones and are faintly marked on the temporals. The occi-
pital bone is low (the relation of its height to the condylobasal length is
30.0-33.3-37.0). The dental row is relatively long (relation of length to
condylobasal length of skull is 17.0-18.7-22.0).

The upper incisors are narrow (relation of width to antero-posterior
cross section is 76.0-83.2-94.0) with two longitudinal ridges on the anterior
surface.

М: (length, 2.3-2.6-2.9 mm; width, 1.8-2.3-2.7 mm; relation of width

179

SSS IN

\

SX

ма

SSS

Figure 50. Microspalax ehrenbergi (Nehr.). Х 1.6.

A—axial skull, from above; B—the same, from below; C—the

same, from the side; D—lower jaw, from outer side; E—the

same, inner view; F—rostral section of skull, anterior view
(schematic); G—lower jaw, posterior view (schematic).

to length, 78.3-88.3-108.3) has no trace of the mesocone. The paracone
is not fused until old age with the anterior collar (Figure 51). The degree
of fusion of the metacone with the posterior collar varies; they are either
fused or partially separated (Figure 51); there are two or three intruding
folds on the outer line (when the metacone is not fused) and on the inner
line, one only. The process of closure in the intruding folds into marks

180

ends earlier in the outer line because of tooth erosion, than in the inner
lines. The arrangement of formation of marks is as follows: the posterior
(vanishing in the old), the anterior external, the central external, and
finally, the internal. In very old individuals, the marks could be absolutely
absent. The protocone and hypocone are approximately equal in magni-
tude. There are three large roots with marks of bifurcation on the internal
and two external, out of which the posterior is less developed than the
anterior (Figure 52).

Figure 51. Microspalax ehrenbergi (Nehr.), upper line of
permanent molars. x8.

A to D—young; Е to -—semi-mature; J to P—adult; О to T—old.

М? (length, 1.8-2.2-2.4 mm; width, 1.8-2.3-2.6 mm; ratio of width
to length, 95.5-107.3-135.3) is, on an average perhaps, more broadened
than in the European Pliocenic Microspalax. The mesocone is completely
reduced. The metacone, as a rule, is fused with the posterior collar. The
tooth has a deep intruding fold on each side, because of which the wearing
surface in the majority of cases is S-shaped. Sometimes, the inner intruding
fold forms an anterior mark. The order of closure for intruding folds and
the formation of marks is as follows: the inner portion of the intruding
fold, the external, and finally, the rest of the portion of the inner one. |
There are three roots—the massive inner and two weakly developed
external ones. In the fissure (depression) between the protocone and
hypocone there is sometimes an additional tubercle (Figure 50).

M? (length, 1.6-1.9-2.3 mm; width, 1.6-2.0-2.2 mm) is wide (ratio of
width to length is 81.8-105.7-123.5). The form of the wearing surfaces is

181

exceedingly variable. The variations are as follows: (а) hypocone and
metacone are isolated from the rest of the parts of the crown of the tooth
(Figure 51); (b) the posterior lobe of the crown (hypocone and metacone)
is fused with the anterior one, as a result of which the wearing surface
assumes an S-shaped form; and (c) usual variations related to the for-
mation of the marks by closure of the intruding folds. On the whole, the
tooth has an intruding fold on each side. However, the complete closure

Figure 52. Structure of roots of upper and lower permanent molars
of Microspalax ehrenbergi (Nehr.) (Mehely, 1909).

182

of the inner fold, differing from the preceding permanent molar, perhaps
takes place earlier than that of the outer fold. The roots are usually three
—the massive posterior and two anterior ones of normal size (Figure 52).
Rarely the roots of the anterior molars exhibit a tendency toward fusion.

The lower jaw has a relatively elongated diastema (for representatives
of the subgenus Microspalax) and a low horizontal branch; the ratio of
the length of the diastema and the height of the horizontal branch at the
level of the center of the alveolus of the anterior permanent molar to the
length of the line of M,—Ms is respectively 61.5—77.0-93.4 and 78.5-88.1-
101.3. In addition the horizontal branch is typically relatively less thick
at the level of M,. Thus, the value of the ratio of the corresponding
measurement to the length of the lines of the permanent molars is equal
to 37.5-45.7-57.8. The symphysis tubercle is flattened and elongated; its
length is approximately equal to the length of the full row of permanent
molars. The ridge in the space between the symphysis tubercle and the
angular process is always present. The mandibular angle is weakly defined
(Figure 50). The lower edge of the masseter area terminates directly near
the alveolar edge. The angular process is more weakly defined than in
the European Pliocenic Microspalax and is less inclined below with a
relatively long base (ratio of length of the latter to length of the lines of
permanent molars is 94.2-112.4—133.3). The alveolar process is low, and
is approximately equal in length to the articular one. The mental (at the
chin) foramen is somewhat shifted toward the alveolar edge. The coronary
tubercle is saddle-shaped, tapering posteriorly in relation to the horizontal
branch. The row of the permanent molars is relatively elongated (relation
of length to condyle length of the lower jaw, 25.0-28.6-33.0).

The lower incisor is narrow (relation of width to antero-posterior
cross section, 64.0-74.5-86.2), with three elongated ridges on the anterior
surface.

The mesoconid on M, is absent. The entoconid is not fused until old
age with the metaconid and the posterior collar respectively, because of
which the anterior and posterior marks are absent on the teeth of the
young, semi-mature, and mature animals. On the whole, the wearing
surface is characterized by the presence of one outer and two inner intrud-
ing folds (Figure 53). The order of closure of the intruding folds into
marks because of tooth erosion is as follows: the posterior inner fold,
the inside portion of the anterior inner fold, and the outer one. The
measurements of the protoconid exceed the measurements of the hypo-
conid less than two times. There are two roots: the posterior one is rather
more massive than the anterior; is flattened in an antero-posterior direc-
tion; and has evidences of bifurcation. Tooth measurements are as follows:
length, 2.2-2.5-2.9mm; width, 1.9-2.2-2.5 mm; relation of width to
length, 77.0-86.2-95.6.

183

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Figure 53. Microspalax ehrenbergi (Nehr.), lower row
of permanent molars. x8.

A to E—young; Ею J—semi-mature; J to P—adult; О to S—old.

М, (length, 1.8—2.1-2.7 mm; width, 1.9-2.2—2.5 mm) is, on the average
perhaps, relatively wider than in the Pliocenic European Microspalax
(relation of width to length, 80.0-104.3-125.0). The form of the wearing
surfaces varies very much. In all the given cases, the tooth either has a
posterior mark and an intruding fold—each in the outer and inner lines—
or it is not fused with the posterior collar of the entoconid and the two
intruding folds in the inner and one in the outer lines. The different varia-
tions are as follows: (a) the posterior collar and the hypoconid are isolated
from the rest of the parts of the crown; (b) the entoconid is fused with
the posterior collar and the posterior mark with the external intruding
folds, because of which the wearing surface has an S-shaped form, i.e.,
it is characterized by the presence of a deep intruding fold in both the
outer and inner lines. The order of the closure of the intruding folds into
marks is as follows: the posterior inner, the anterior inner, and the outer.
The tooth has two antero-posteriorly flattened roots with clear signs of
bifurcation. The posterior root is rather more massive than the anterior
one.

M; (length, 1.6-2.1-2.8 mm; width, 1.7-2.0-2.2 mm) is also relatively
wider than in the European Pliocenic Microspalax (relation of width to
length, 70.0-96.4-116.7). The form of the wearing surfaces for the majority
of the given cases was S-shaped. The presence of an additional posterior
intruding fold was rare (present only when the entoconid was not fused

184

with the posterior collar). The closure of the intruding folds into marks
took place more quickly in the inner line than in the outer. The tooth
has two roots; moreover, the anterior one has a bifurcated end (Figure 52).

Comparison. It differs from all the fossil European species of the sub-
genus Microspalax by:

1. The presence of two longitudinal ridges on the anterior surface of
the upper incisors. They are always absent in European species.

2. On an average, narrower upper and lower incisors (ratio of width
to antero-posterior cross section is equal to 76.0-83.2-94.0 for the upper,
and 64.0-74.5-86.2 for the lower incisors, against respectively 82.6-90.0-
95.0 and 75.7, 80.6, 84.6, 87.5 in М. compositodontus; 95.4, 100.0, 100.0
and 70.3-86.2-93.5 in М. тасоуей; and finally 83.3-89.7-95.8 and 71.4—
81.2-90.0 in М. odessanus.

3. On an average, a wider М; the magnitude of the ratio of width of
the last permanent molar to its length is equal to 81.8-105.7-123.5 for
the upper, and 70.0-96.4—116.7 for the lower tooth as against respectively
77.8 and 72.7 in M. compositodontus; 88.9 and 87.5, 90.5, 95.6 in M.
macoyeii; and finally 95.0-100.0-115.0 and 82.7-89.8-95.6 in М. odessanus.

In addition to the traits described above, M. ehrenbergi differs from
the Late Miocene—Early Pliocene М. compositodontus by the absence of a
mesocone on МГ? and of a mesoconid on M,; of additional intruding
folds on the inner line and tubercle at the base of the paracone on М?;
and also by a weakly developed hypocone on M?~ and protocone on
M,—the measurements of which exceed respectively less than twice the
protocone and hypoconid (in M. compositodontus the difference in the
aforementioned tubercles is more clearly expressed).

The presence of three roots on М! and МЗ in М. ehrenbergi could be
taken as an additional peculiarity of the lower jaw to the ones already
mentioned which helps in differentiating M. ehrenbergi from the Mid-
Pliocene European species of the given subgenus, М. macoveii and М.
odessanus (in their Mid-Pliocenic European forms, there are two, as a
rule); the flattened symphoidal tubercle and faintly defined mandibular
angle; on an average, a relatively higher and thicker horizontal branch
(relation of its height at the level of М, and thickness at the level of M,
to the length of the row of permanent molars is equal to 78.5-88.1-101.3
and 37.5-45.7-57.8 against respectively 81.8-97.6-108.0 and 46.0-54.0-
62.7 in М. macoveii; and 80.0-96.0-107.6 and 42.0-51.4-55.0 in М.
odessanus); and also the process which is saddle-shaped and considerably
steeply inclined backward in relation to the alveolar edge of the horizontal
branch (in fossil European forms, this process is slanting, steeply placed
in relation to the horizontal branch and its apex is almost not bent back-
ward). Finally, average smaller measurements than the above-mentioned
species’ also differentiate it from others.

185

It is better to add to the above that this species differs from М. тасоуей
by a long lower diastema (the magnitude of the diastema-tooth ratio is
61.5—77.0-93.4 against 62.5-70.8—75.0); a long symphoidal tubercle of the
lower jaw (its length is approximately equal to the length of a full line
of permanent molars and in M. macoveii the magnitude of this measure-
ment approximately corresponds to the length of M,—M.,); the supra-
maxillary foramen is shifted to the alveolar edge (in M. macoveii it is
situated equidistant from the alveolar and the lower edges of the hori-
zontal branch); an elongated lower edge of the masseter area (in the mole
rat of Ehrenberg it terminates in the immediate vicinity from the alveolar
edge, and in M. macoveii approximately at the level of the supramaxillary
foramen); absence of a free mesoconid or the anterior mark on M,; and
also of an additional intruding fold in the inner line on М, of young,
semi-mature, and mature animals. It differs from M. odessanus by the
presence of a clearly defined longitudinal depression on the nasal bones,
in the shape of temporo-nasal and temporo-maxillary sutures (in M.
ehrenbergi, it forms an angle with its apex pointing backward; in M.
odessanus, it is in the shape of a straight line); a narrow hard palate
between М? (its width is approximately similar to the width of alveolus
of the anterior permanent molar; in M. odessanus, it is wider than the
latter); a constricted skull in the incisorial and rostral sections; a wide
groove behind the palate (width of this groove in M. ehrenbergi is approx-
imately equal to the length of the last permanent molar; in M. odessanus,
it is less than the latter); and an absence of a posterior mark on the M,
of young, semi-mature and mature individuals.

` Measurements. Condylobasal length of skull, 31.0-38.1-43.9 mm; basic
length, 28.3-35.7-41.9 mm; length of nasal bones, 13.9-16.4-19.2 mm;
total length of parietal and temporal bones, 13.9-16.3-19.5 mm; length
of parietal bones, 5.7-7.2-9.1 mm; length of upper diastema, 9.9-13.2-
15.9 mm; length of hard palate, 18.6-23.4—27.8 mm; length of upper row
of permanent molars, 6.5-7.4-8.3 mm; width of nasal opening, 3.7—4.2-
4.8 mm; incisorial width, 4.5—5.7—6.8 mm; width of nasal bones anteriorly,
4.4-5.3-5.9 mm; rostral width, 7.1-8.0-9.7 mm; width behind the eyes,
6.2—7.1-8.1 mm; width of both parietals, 11.4-12.8-14.8 mm; width of
parietal bone along lambdoid ridge, 6.0-7.0-8.8 mm; malar width 22.9-
27.2-32.8 mm; width of occipital (largest width), 22.1—25.5-27.9 mm; width
of auditory bullae, 8.7-10.3-11.6 mm; length of auditory bullae, 6.6—7.0-
7.7mm; width of upper incisor, 1.5—1.9-2.4 mm; antero-posterior cross
section of upper incisor, 1.7-2.2-2.7 mm; height of occipital bone, 10.4—
13.2-15.5 mm; height of nasal cavity, 2.4-3.1-3.6 mm; angular length of
lower jaw, 22.0-25.1-29.3 mm; condylary length of lower jaw, 20.1-23.9-
27.7 mm; length of lower diastema, 4.8—5.6-6.9 mm; length of lower row
of permanent molars, 6.4-7.3-7.9 mm; height of horizontal branch at the

186

level of center of alveolus of МЕ, 5.8—6.4—7.4 mm; thickness of horizontal
branch at the level of M,, 2.7-3.3-4.4 mm; height of alveolar process
from inside, 2.0-3.9-5.1 mm; width of lower incisor, 1.4-1.9-2.5 mm;
antero-posterior cross section of lower incisor, 1.8-2.5-3.0 mm.

Note. M. ehrenbergi is the only recent representative of the subgenus
Microspalax. In addition to highly specialized traits, it has preserved a
number of primitive characteristics in the construction of the skull, the
lower jaw, and the permanent molars. Before the traits which determine
the subgeneric disposition of the species, the combination of morpho-
logical structures which indicate a lesser adaptability toward a burrowing
type of life has to be enumerated first (the narrowed upper and lower
incisors, and the relative characteristics of the facial skull and the lower
jaw). As far as the masticatory apparatus is concerned, its primitiveness
is determined by the complexity of the picture of the wearing surfaces
of first, the permanent molars, that of M,, and then the roots which are

‘reduced to a lesser extent. From the degree of development of adaptation
to burrowing, the mole rat of Ehrenberg stands on a rather lower evo-
lutionary step than even the Mid-Pliocenic and Late Pliocenic fossils of
the European Microspalax; from the viewpoint of the degree of special-
ization in teeth, the fossil Mid-Pliocenic M. odessanus exceeds it. All this
makes easy a statement about the comparatively early (perhaps beginning
of the Pliocene) separation of the Asia Minor and European branches of
the subgenus, each of which developed further independently. It can also
be presumed that the indicated species has greatly preserved the characters
of the original type common for Microspalax of Asia Minor and Europe.

In his first description of the species, Nehring (1897) included in the
group of Asia Minor Microspalax three more species—M. kirgisorum
(Nehr.), М. aegyptiacus (Nehr.) and М. intermedius (Nehr.)—besides М.
ehrenbergi by erroneously considering individual and age variables in the
structure of permanent molars as taxonomic traits. In his work, the
description of M. kirgisorum has been done before that of M. ehrenbergi.
However, there was some dispute over the fixation of habitat for the typical
example of M. kirgisorum. Nehring obtained the skull and skeleton from
Shlyuter by ‘“‘unfair means’; Shlyuter indicated that they were found in
the steppes of Kirgiziya, near the Volga (Rinpeski, western Kazakhstan
region; Ognev, 1947), i.e., around the present day area of 5. giganteus
Nehr. By the way, the fact that the skull belonged to Microspalax was
beyond doubt and Mehely indicated this in his time (1909). This is shown
by such traits as comparatively smaller dimensions, the presence of very
narrow upper and lower incisors with longitudinal ridges on the anterior
surface, weakly developed sagittal and lambdoid ridges, a narrow facial
section, nasal bones with a sharply defined longitudinal slit-like depres-
sion, and a number of other peculiarities of construction of the skull and

187

the permanent molars (the lower jaw and the post-cranial skeleton were
not described by Nehring). Taking all this into consideration and remem-
bering that at present only S. giganteus is found in the Volga region,
it can be said confidently that the specimen described by Nehring was
not found in the Volga area. In this way, the place of the find of the
holotype M. kirgisorum remains unknown. All the aforesaid forces us not
to use this nomenclature for the species, and out of the three remaining
synonyms, select the next one in order of description, i.e., M. ehrenbergi.

Mehely (1909) also did not recognize M. kirgisorum, M. aegyptiacus
and M. intermedius as independent species, considering the first two as
variants of M. ehrenbergi and the last one as a synonym for M. e. kirgi-
sorum (this subspecies, in the opinion of Mehely, includes mole rats living
in the region of Israel, Syria, Jordan, and Lebanon). However, as will be
shown below, the separation of variants was done by them exclusively on
a territorial principle, without sufficient basis for morphological differ-
ences. Thus, the differences attested to for the nominal subspecies and
M. e. kirgisorum Nehring, which according to the opinion of Mehely
(1909; 24, 25) are contained in the different number of ridges on the
anterior surface of the lower incisors, the magnitude and degree of the
pointedness of the angular process of the lower jaw and, also, in the
details of construction of the roots of permanent molars and measurements,
have not been confirmed on a series of skulls.

Nehring (1902) described a new species, M. fritschi Nehring on the
basis of a lower jaw found in Holocene sediments of Lebanon. There is
no doubt that this lower jaw belonged to the subgenus Microspalax which
is shown by comparatively smaller measurements and the presence of
three longitudinal ridges on the anterior surface of the incisor. Nehring,
and after him even Mehely (1909) thought that the angular process on
the jaw from Lebanon was on the whole more massive and rather more
acutely inclined outward than in the then-living M. ehrenbergi. However,
this was not confirmed during a comparison with a typical example from
the series of lower jaws of the modern M. ehrenbergi. The traits described
by Miller (1903) in his diagnosis of M. berytensis (Miller) from Libya
(around Beirut) also fall within the range of individual variability. Thus,
all the aforesaid makes us regard even these names as synonyms of М.
ehrenbergi.

Distribution and Geological age. The northern regions of Libya and
the United Arab Republic, Israel, Jordan, Libya, Syria, Iraq, possibly
the southern regions of Turkey. Recent; fossil remains are known only
from the Holocene sediments of Libya.

Subspecies 1. М. e. ehrenbergi Nehring, 1897 (including М. e. kirgi-
sorum Nehring, 1897). Distributed in Israel, Jordan, Libya, Syria and
possibly in southern regions of Turkey.

188

2. М. е. aegyptiacus Nehring, 1897. It differs from the nominal sub-
species by, on an average, a narrower rostral section of the skull, elongated
nasal bones, and a more strongly developed proc. naso-basalis. It is distri-
buted in North Africa (Egypt and possibly from Libya up to Tripoli).

2. Microspalax compositodontus W. Topachevskii, sp. nov.—Com-
plex-toothed Mole Rat

Holotype. Institute of Zoology, AN Ukraine SSR, No. 41-712; isolated
left upper first permanent molar (М1 sin.); around the Black Sea of
Ukraine, Andreevka of Berezan district of Nikolaev region; Late Miocene.

Paratypes. Isolated permanent molars—M? sin. (No. 41-713), МЗ dex.
(No. 41-714), М, sin. (No. 41-715) and М. sin. (No. 41-716). All are
preserved in the collections of the Institute of Zoology, AN Ukraine SSR.

Additional Material. Isolated incisors: upper, seven samples; lower, five
samples. These are preserved at the same place.

Diagnosis. Measurements are small: length of М! is 2.3 mm; of М,
is 2.6 mm. The mesocone of М! is well developed at almost all stages of
tooth development (perhaps it becomes completely complex as compared
to similar permanent molars of other representatives of the genus). M,
entoconid of this tooth is not fused with the posterior collar. The massive
mesoconid is separated from the metaconid and the entoconid is always
present; along with the latter, it forms a characteristic inner fork; the
neck width of which exceeds one-third the length of the wearing surface
of the tooth, or is approximately equal to it. The upper incisors are without
two longitudinal ridges on the anterior surface.

Description. Remains of the skull and lower jaw are not known. The
upper incisors are narrow; the relations of width to antero-posterior cross
section is 82.6-90.0-95.0. The enamel on their anterior surface is smooth,
without longitudinal ridges.

The paracone on М! in young, semi-mature, and mature individuals
is not fused with the anterior collar (perhaps it fuses only in very old age).
In addition, this fold is completely separated from the neck which also
connects the inner anterior (protocone) and posterior (hypocone) folds
(Figure 6). The mesocone is well developed and is completely separated
from the paracone. During tooth erosion perhaps, the mesocone fuses
with the paracone but during this fusion, the former is preserved up to
old age in the shape of a well-developed process on the posterior wall
of the latter. At the same time, perhaps, the fusion of the paracone with
the neck which connects the protocone with the hypocone, also has a
considerable meaning and, as a result, a portion of the anterior intruding
fold forms a mark. The hypocone is almost twice longer than the proto-
cone. The metacone at a given stage of wearing is still separated from the

189

posterior collar though a tendency toward their fusion has been quite
clearly observed. The general measurements of the tooth (length, 2.3 mm;
width, 2.1 mm), the corresponding height of the crown, and the peculiar-
ities of construction of the preserved parts of the base of the roots, prove
that they belong more to very old individuals than to semi-mature, and
least of all to young animals.

М? (Figure 6) belonging to mature animals is complex like the preced-
ing permanent molar. The mesocone, differing from the same on M}, is
fused with the paracone at a given stage of wearing. Moreover, the para-
cone is fused with the collar. The fusion of the paracone at a given stage
of wearing takes place in addition to the fusion of the latter with the
anterior collar. The fusion of the paracone with the neck, connecting the
protocone with hypocone, does not take place. As a result, the anterior
outer intruding fold forms a mark which has a form of a crescent. The
complexity of the wearing surface takes place also because of the remains
of an additional inner intruding fold placed anterior to the protocone and
the external additional tubercle at the base of the paracone. The hypocone,
as in M1, approximately twice exceeds the protocone. The metacone is
fused with the posterior collar. There are three roots—the massive inner
and two weakly developed outer. The measurements of the tooth are as
follows: length 2.2 mm; and width 2.0 mm.

M? (Figure 6) is strongly drawn out (elongated) in a longitudinal direc-
tion (length, 1.8 mm; width, 1.4 mm; relation of width to length, 77.8)
and has an S-shaped form on the wearing surface. Notwithstanding the
fact that the tooth belonged to a considerably mature animal, all the
intruding folds are open. There are three
roots—the massive inner and two rather
weak outer (Figure 54). There is no fusion
of roots. >

The lower incisor is narrow (relation uN
of width to antero-posterior cross section,

75.7; 80.6; 84.6; 87.5) with three longi-

tudinal ridges on the anterior surface.

The central ridge sometimes exhibits a

tendency toward bifurcation. The anterior М3 My
surface of the incisor is very convex.

M, (Figure 6) is complex. The ento- Figure 54. Structure of roots of

conid is not fused with the posterior
collar in almost all stages of wear. The
mesoconid is represented by а well-
developed independent fold fused neither

permanent molars of Micro-

spalax compositodontus sp.

nov., Late Miocene of South
Ukraine.

with the metaconid nor with the entoconid. It forms, along with the
latter, a characteristic inner fork, the neck width of which exceeds one-

190

third the length of the wearing surface of the tooth, ог is approximately
equal to it. The protoconid is approximately twice greater than the
hypoconid. In the anterior portion of the tooth, there is a mark represent-
ing a linked portion of the anterior inner intruding fold. There are two
roots—the massive antero-posteriorly flattened posterior one, and a
weakly developed anterior. The posterior root has a tendency toward
bifurcation. The tooth belonged to a mature animal. Measurements were:
length 2.6 mm; width 2.3 mm.

М; is elongated in а longitudinal direction (length, 2.2 mm; width,
1.6 mm; relation of width to length, 72.7) and has a characteristic S-shaped
form on the wearing surface with two anterior and one posterior mark.
Additionally, all the permanent molars of M. compositodontus have, with-
out exception, a relatively lower crown.

Comparison. The basic characteristic by which M. compositodontus
differs from all other species of the subgenus Microspalax is the presence
of many folds on its permanent molars which make the structure of the
latter more complex. In addition, there are other differences related, first
of all, to the general proportions of the teeth, corresponding measure-
ments of their separate parts, and the structure of their roots. A detailed
comparison of the compositodontus mole rat with contemporary and fossil
representatives of the subgenus Microspalax has been given below.

The compositodontus differs from all the presently known species of
the subgenus Microspalax by:

1. The presence of mesocone on М! and М2. It is absent in other
species.

2. The presence of remains of a middle inner intruding fold on М>,
and a tubercle at the base of the paracone. It is absent in other species.

3. The presence of a massive free mesoconid on M, in maturity which
is not fused with the metaconid, and a wide inner fork, the neck width of
which either exceeds one-third the length of the whole wearing surface of
the tooth or is approximately equal to it. In other species, the mesoconid
is absolutely absent (М. ehrenbergi), is underdeveloped (М. odessanus sp.
nov.), or finally, is present in young animals but fuses with the metaconid
in mature age [М. macoveii (Simionescu)]. In the last two instances the
width of the neck of the inner fork does not exceed one-fourth the total
length of the wearing surface.

4. The more strongly developed hypocone on М! and М? and the
protoconid on M, almost twice exceed the protocone and hypoconid
respectively. In the remaining representatives of the subgenus Microspalax,
differences in the respective measurements of the above-mentioned parts
of these teeth are not that significant.

5. The more elongated and longitudinal direction of M3. Thus the
magnitude of the ratio of width of tooth in M. compositodontus is 77.8 for

191

МЗ and 72.7 Гог М. against, respectively, 81.8—105.7—123.5 and 70.0-96.4—
116.7 in M. ehrenbergi; 88.9 and 87.5, 90.5, 95.6 in M. macoveii; and
finally, 95.0-100.0-115.0 and 82.7-89.8-95.6 in М. odessanus.

Furthermore, the compositodontus mole rat differs from M. ehrenbergi
by, on the average, wider upper and especially lower incisors (the range
of relation of width of incisors to antero-posterior cross section is equal
to 82.6-90.0-95.0 for upper, and 75.7, 80.6, 84.6, 87.5 for lower incisors in
М. compositodontus against, respectively, 76.0-83.2-94.0 and 64.0-74.5-
86.2 in M. ehrenbergi); and from M. macoveii and M. odessanus by a lesser
degree of reduction of roots for M? (in the last two species, the number of
roots of this tooth, as a rule, does not exceed two). It should be remem-
bered that in the compositodontus the entoconid of M, is not fused with
the posterior collar until after very old age, differing from the Mid-
Pliocenic M. macoveii and M. odessanus, whereas in the latter two, the
process of fusion ends either in the mature (M. macoveii) (Figure 56) or
even in the young (M. odessanus) (Figure 60).

Note. From the description given above of M. compositodontus and
its comparison with fossil and living species of the subgenus Microspalax,
it is seen that the given species out of the presently known representatives
of the subfamily Spalacinae had the most primitive permanent molars
according to their structure. This can be deduced from the general com-
plexity of the wearing surface of the molar teeth and a lesser reduction
of their roots—a fact which puts the complex-toothed mole rat in a specific
category to the forms which are original for Spalacinae. According to
the degree of complexity in the molar teeth, М. ehrenbergi is most closely-
related to M. compositodontus, though in this species, the permanent
molars on the whole are more simplified. This similarity is due mainly to
the presence of an entoconid on M, up to very old age in the mole rat
of Ehrenberg which is not fused with the posterior collar.

In addition, according to the degree of development of adaptation to
a burrowing way of life in the structure of the incisors, the composito-
dontus considerably exceeds not only the present-day M. ehrenbergi, but
even certain more primitive representatives of the subgenus Mesospalax
which have a greater specialization for a burrowing existence and also
the M. nehringi from Asia Minor and around Kavkaz. This throws some
light on the different trends of development in adaptation toward feeding
and a burrowing way of life, as well as on the limitations for examining
the compositodontus as a type—original for all the fossil and present-day
species of the subgenus- Microspalax, notwithstanding its considerable
geological antiquity. At the same time, it can be successfully taken as an
ancestral type of the European Pliocenic Microspalax—M. macoveii
and M. odessanus. This is as if proven by the gradual simplification of
the structure of permanent molars, and the growing degrees of reduction

192

of their roots through comparatively minor changes in the structure of
incisors in the evolutionary lines of М. compositodontus—M. тасоуей
and species closely related to it—types closer to M. odessanus.

Habitat. Village Andreevka (near Tiligulo-Berezanki), Berezan region.
Nikolaev region, right bank of Tiligulo-Berezan estuary; ancient alluvial
sands lying under Pontiac limestone.

Distribution and geological age. Around the Black Sea of the Ukraine;
Late Miocene.

3. Microspalax macoveii (Simionescu, 1930)—Mole Rat of Macovei

Prospalax Macoveii Simionescu, 1930: 21, 22, Figure 31-33, Tab. 2, Figures 3, 4. Plio-
spalax simionescui Kormos, 1932: 194-198, Abb. 1.

Holotype. University of Yassakh (Rumania); the number of the exhibit
was not fixed; lower jaw (mandibular sin) with an intact incisor, two
anterior permanent molars (M,-M,), the articular process and the
angular one (Simionescu, 1930: 22, Figure 33, Table 2, Figure 4); Ruma-
nia, Malushten, Kovurlui region; Mid-Pliocene.

Paratypes. Fragments of the lower jaw (mandibular dex.) from Malu-
shten and Bereshti (Simionescu, 1930: 22, Figure 32, Table 2, Figure 3;
Kormos, 1932: 195, Abb. 1); Rumania; Mid-Pliocene; preserved in the
collections of the University in Yassakh; the number of samples had not
been fixed. Lower jaw (mandibular dex.) with completely preserved in-
cisors, row of permanent molars (M,-Ms;), and the angular process;
Ukraine SSR, Novopetrovka of Odessa region; Mid-Pliocene; preserved
in the collections of the Institute of Zoology AN Ukraine SSR, No. 37-970.

Additional Material. Fragment of palatal portion of the skull with
alveoli of M1-2; lower jaws and their fragments, samples 14; isolated
teeth—upper incisors, samples 3; M!, samples 4; МЗ, one sample; lower
incisors, samples 13; Ми, samples 3; М», samples 2; M3, one sample; а
few fragments of limb bones.

Diagnosis. Measurements are minimal (within the boundaries of the
subgenus Microspalax); length of the lower row of permanent molars,
7.4-7.9-8.6 mm. The mesocone on M!-M? is absent. The width of the
hard palate between М! is less than the width of the alveoli of the anterior
permanent molar, or is approximately equal to it; the central ridge is weak,
in the shape of a narrow ridge, or is absolutely absent. The free mesoconid
on M, is present only in young animals. In mature animals it fuses with
the metaconid; the inner side of the anterior fold of the lingual line
encloses into a mark which is stretched in a longitudinal direction. The
neck width of the inner fork is approximately equal to one-fourth the
total length of the wearing surface of M,. The entoconid is free in young
individuals; in maturity it fuses with the collar which encloses the posterior

193

intruding fold of the inner line in the shape of a mark. The anterior surface
of the upper incisors is smooth, without longitudinal ridges.

Description. The structural peculiarities of the hard palate have been
noted in the diagnosis. The upper incisor is, on an average perhaps, wider
than in the preceding species and in M. ehrenbergi. The relation of the
width of the incisor to the antero-posterior cross section is 95.4, 100.0,
100.0. The anterior surface of the incisors is smooth, without longitudinal
ridges.

М: has по sign of a mesocone. The paracone is not fused with the
anterior collar in young, semi-mature and mature animals. The fusion
takes place only toward old age (Figure 56). The metacone fuses with the
posterior collar in the early stages of wearing. The number of intruding
folds in the outer line is two; in the unfused metacone, three; and in the
inner line, one. Because of tooth erosion the process of closure of the
intruding folds into marks ends earlier in the outer lines than in the
inner lines. The order of closure is as follows: the posterior external,
the anterior external, the central external, and finally, the inner one.
In very old individuals, marks on teeth are absolutely absent. The
hypocone usually exceeds the protocone less than twice. There are two
roots—the massive antero-internal and a comparatively weak postero-
external (Figure 57). The antero-internal root with a canalicular posterior
wall exhibits a tendency toward bifurcation. Rarely, the number of roots
of M! may reach to three. In this case, their disposition in the alveolus
would look as follows: the massive inner and two approximately equally
developed external ones. Reduction takes place due to a coalescence of
the anterior outer and inner roots. The measurements of М! are: length,
2.7, 2.7, 2.9 mm; width, 2.2, 2.3, 2.6 mm; relation of width to length, 81.5,
85.2, 89.6. Possibly, this tooth is, on the average, more elongated in a
longitudinal direction than in other representatives of this subgenus.

МЗ (length, 1.8 mm, width, 1.6 mm; ratio of width to length, 88.9) is
less elongated in a longitudinal direction than in previous species. The
inner intruding fold closes into marks in the early stages of tooth erosion,
though it remains fused for a long time with the outer intruding fold.
Because of this, the wearing surface of both has a C-shaped form. At a
given stage of wearing, an additional tubercle is still preserved at the
base of paracone. The roots have not been preserved.

The lower jaw has a short diastema and a relatively big horizontal
branch. The relation of the length of the diastema and the height of the
horizontal branch at the level of center in the alveolus of M,, measured
from outside, to the length of the row of permanent molars is respectively
equal to 62.5-70.8-75.0 and 81.8-97.6-108.0. The symphoidal tubercle is
clearly defined (Figure 55) and short; its length is considerably less than
the length of permanent molars (approximately equal to the length of

13

194

M,-M,). The ridge on the space between the symphoidal tubercle and
the angular process is absent. The ridge on the masseter area terminates
at a considerable distance from the alveolar edge, a little above the
mental foramen. The angular process is clearly defined, sharply bent down,
and has possibly a shortened base (relation of the length of base to length
of row of permanent molars is 88.7, 104.8). The alveolar process is low

Figure 55. Microspalax тасоуей (Sim.). x 1.7.

A—lower jaw, external view; B—the
same, internal view.

and is approximately equal to the articular one. The mental foramen does
not blend with the alveolar edge; it is situated approximately at an equal
distance from the alveolus and the lower edges of the jaw. The coronary
process is slanted and its apex has practically no backward incline. The
body of the mandible is relatively thick (ratio of thickness at the level of
М. to length of row of permanent molars is equal to 46.0-54.0-62.7).

The lower incisor is, perhaps, wider than in all the presently known
representatives of the subgenus Microspalax (the relation of width of
incisor to antero-posterior cross section is 70.3-86.2-93.5), with three
longitudinal ridges on its surface.

The mesoconid on M, is free in young individuals (Figure 56). In
mature animals, it is fused with the metaconid. During this, a portion of
the anterior intruding fold of the inner line closes as a mark elongated
in a longitudinal direction. The width of the inner fork is approximately
equal to one-fourth the total length of the tooth. The entoconid in young
animals is not fused with the posterior collar, but exhibits a tendency
toward fusion in mature animals. It should also be noted that the proto-

195

conid and anterior collar (which are fused in mature animals) are dis-
connected. The protoconid exceeds the hypoconid less than twice. There
are two roots—the posterior one is rather more strongly developed than
the anterior, is flattened in an antero-posterior direction, and has vestiges
of bifurcation. The measurements of M, are as follows: length, 2.4, 2.7,
2.7, 2.7 mm; width 2.0, 2.2, 2.3, 2.4 mm; relation of width to length, 81.5,
83.3, 85.2, 88.9. The order of closure for the intruding folds and the marks
is as follows: the posterior and interior part of the anterior plate of the
inner line, the anterior internal, and finally, the external. The marks are
totally absent in very old age.

Figure 56. Microspalax macoveii (Sim.), upper and
lower permanent molars. Mid-Pliocene of South
Ukraine and Moldavia.

The entoconid on М, in mature animals is fused with the posterior
collar. During this, the posterior intruding fold of the inner line closes as
a mark. The mark vanishes with age. On the whole, the work surface is
characterized by the presence of one outer and one or two (in an unworn
condition) intruding folds. The order of their closure into marks is the
same as in the preceding molar. The protoconid and hypoconid are
approximately of the same size. There are two roots. Of them the posterior
is better developed than the anterior. Both roots have vestiges of bifur-
cation which indicates their complex nature (each was formed in the
process of fusion of two roots—the external and internal); they are flat-
tened in an antero-posterior direction. The end of the anterior root is

196

bifurcated in the shape of a fork; there is a socket for each end of the
fork in the alveolus. The measurements of the tooth are as follows: length,
2.2, 2.2, 2.4, 2.6 mm; width, 2.1, 2.2, 2.4, 2.6 mm; relation of width to
length, 84.0, 100.0, 108.3, 109.1.

М. (length, 2.1, 2.3, 2.4 mm; width, 1.9, 2.1, 2.2 mm) is relatively
longer (relation of length of М. to length of the preceding permanent
molars is 95.8, 109.1) and elongated in a longitudinal direction (relation
of width to length is 87.5, 90.5, 95.6). The shape of the wearing surfaces
are, as a rule, S-shaped though in some cases the inner portion of the
external intruding fold closes into a mark. In young and semi-mature
animals, vestiges of an additional fold of the inner line, placed anterior
to the metaconid, are present (Figure 56). The tooth is characterized by
the presence of two roots which are fused all along and flattened in an
antero-posterior direction, each of which has clear marks of bifurcation.
The terminus of the anterior root has even two free ends for each of which
there is a socket in the alveoli.

Comparison. It differs from М. ehrenbergi by:

1. Average large absolute measurements.

2. A weakly developed central ridge of the hard palate (wider in M.
ehrenbergi).

3. Absence of longitudinal ridges on the anterior surface of the upper
incisors (always present in M. ehrenbergi). In addition, the upper and
lower incisors of M. macoveii are, on an average, wider than in M. ehren-
bergi (relation of width of incisor to its antero-posterior cross section in
М. macoveii is equal to 95.4, 100.0, 100.0 for the upper, and 70.3-86.2=
93.5 for the lower tooth as against respectively 76.0-83.2-94.0 and 64.0-
74.5-86.2 in М. ehrenbergi).

4. Presence of two and not three roots for M1—M? in the majority of
the given cases.

5. The М? is more elongated in a longitudinal direction (relation of
width to length is 88.9 against 81.8-105.7-123.5 in М. ehrenbergi).

6. A relatively short lower diastema (relation of diastema-tooth is
62.5—70.8—75.0 against 61.5—77.0-93.4 in М. ehrenbergi).

7. On an average, a relatively higher and thicker horizontal branch at
the level of M, (relation of its height on the level of the antero-permanent
molar, and thickness at the level of M, to the height of line of permanent
molars is equal to 81.8-97.6-108.0 and 46.0-54.0-62.7 in М. macoveii,
as against respectively 78.5-88.1-101.3 and 37.5-45.7-57.8 in М.
ehrenbergi).

8. A clearly defined, downward bent, short symphoidal tubercle (length
is approximately equal to the length of the two anterior permanent molars),
and a well-expressed mandibular angle; in M. ehrenbergi, the symphoidal
tubercle is flattened and elongated (its length is approximately equal to

197

the length of a full row of permanent molars), and the mandibular angle
is expressed faintly.

9. A mental foramen which is separate from the alveolar edge (placed
approximately equidistant from the alveolar and lower edges of the
horizontal branch). It is placed nearer to the alveolar edge in M. ehrenbergi.

10. The ridge on the masseter surface does not reach up to the alveolar
edge of the horizontal branch (it terminates approximately at the level of
the chin opening in M. macoveii). In M. ehrenbergi, it almost reaches the
alveolar edge.

11. A coronary process steeply placed with respect to the horizontal
branch, the apex of which is practically non-inclined behind. In M. ehren-
bergi, the coronary process is bent, saddle-shaped, and more tapered in
relation to the horizontal branch.

12. A clearly defined angular process which is sharply bent down. It is
flattened, and slightly bent down in M. ehrenbergi.

13. Presence of a mesoconid on M,—free in young animals and fused
with the metaconid in mature animals (it is altogether absent in M.

ord

м!
Figure 57. Structure of roots of permanent molars of

Microspalax тасоуей (Sim.). Mid-Pliocene of South
Ukraine and Moldavia.

ehrenbergi). Furthermore, in M. macoveii, the entoconid exhibits a ten-
dency toward fusion with the posterior collar in mature animals (in M.
ehrenbergi, they are not fused up to old age). |

14. Presence of an additional fold of the inner line and posterior mark
(absent in М. ehrenbergi); on М. of young and semi-mature individuals;
and also by the fused roots of this tooth almost all along the row (in M.
ehrenbergi, the anterior and posterior roots are not fused and the tendency
toward bifurcation in each of them is rarely expressed). In addition, the
M, in M. macoveii is, on an average, more elongated in a longitudinal
_ direction than the similar permanent molars of М. ehrenbergi (the relation
of width of tooth to length is equal to 87.5-90.5-95.6 as against 70.0-96.4—
116.7 in M. ehrenbergi).

198

The most important differences from М. compositodontus may be
summarized as follows:

1. The mesocone on M1!—M? is absent.

2. The vestiges of an anterior inner intruding fold and an additional
tubercle at the base of the paracone are absent on M?.

3. The mesoconid in mature animals is fused with the metaconid and
the width of the neck of the inner fork does not exceed one-fourth the
total length of the wearing surface. In the compositodontus mole rat, the
mesoconid is free up to very old age, and the width of the neck of the
inner fork exceeds one-third the length of the wearing surface, or is approx-
imately equal to it. In addition, the entoconid of the first lower permanent
molar in mature animals has a tendency to fuse with the posterior collar
(in M. compositodontus it is not fused until up to very old age).

4. The hypocone on М! and М? and the protoconid on М, are weakly
developed. These dimensions are exceeded less than twice by the measure-
ments of the corresponding protoconid and hypoconid.

5. М? are less elongated in a longitudinal direction (relation of width
to length is equal to 88.9 for upper, and 87.5, 90.5, 95.6 for lower, as
against respectively 77.8 and 72.7 in M. compositodontus). Furthermore,
the МЗ of М. macoveii has, perhaps, not more than two roots; in М.
compositodontus there are three.

6. The upper and lower incisors are, on the average, wider than in M.
compositodontus (relation of width of incisor to antero-posterior section
is equal to 70.3-86.2-93.5 for the lower, and 95.4, 100.0, 100.0 for the
upper teeth, as against respectively 75.7, 80.6, 84.6, 87.5 and 82.6-90.0-
95.0 in M. compositodontus).

Finally, it differs from the Mid-Pliocene M. odessanus as follows:

1. A narrow inter-dental space in the anterior portion (width of the
hard palate between М1 is less than the width of the alveolus of this tooth,
or is approximately equal to it); and a weakly developed central ridge of
the palate (which may be absolutely absent). In M. odessanus, the width
of the alveolus of the anterior permanent molar, and the central ridge is
massive and broad.

2. The presence of a mesoconid on M, which is free in young indivi-
duals, and fused with the metaconid in mature ones, with the formation
of an anterior mark by a relatively wide inner fork (the neck width of
which is approximately equal to one-fourth the length of the masticatory
surface); and by a late fusion of the entoconid with the posterior collar.
In M. odessanus the mesoconid is reduced, the entoconid and posterior
collar are fused even on the teeth of young individuals, and the width of
the inner fork (if it is present at all) is considerably less than one-fourth
the total length of the masticatory surface. Furthermore, the fusion of
the entoconid with the metaconid takes place in M. macoveii through the

199

mesoconid, as a result of which the anterior mark (representing the inner
portion of the anterior intruding fold of the inner line) forms even on
the teeth of young animals. In M. odessanus the fusion of the correspond-
ing folds takes place directly with each other and that, too, in very old
age; and the anterior intruding fold of the inner line does not form an
anterior mark.

3. The МЗ which is, on the average, more elongated in a longitudinal
direction (relation of width to length, 88.9 as against 95.0-100.0-115.0).

4. A shortened symphoidal tubercle of the lower jaw, the length of
which is approximately equal to the length of the two anterior permanent
molars. In M. odessanus, it is approximately equal to the length of a
complete line of permanent molars. In addition, the ridge in the space
between the symphoidal tubercle and the angular process which is well
developed in M. odessanus, is absent in M. macoveii.

5. A shortened lower ridge of the masseter area which approximately
terminates at the level of the mental foramen. In M. odessanus, this ridge
is placed considerably above the for. mentale.

6. Apparently wider upper and lower incisors (relation of width of
tooth to antero-posterior cross section is equal to 95.4, 100.0, 100.0 for
the upper, and 70.3-86.2-93.5 for the lower, as against respectively 83.3-
89.7-95.8 and 71.4—81.2-90.0 in Odessa mole rats).

7. The presence of vestiges of an additional intruding fold on М; in
young and semi-mature individuals (absent in M. odessanus).

8. On an average, smaller absolute dimensions.

Measurements. Condylar length of lower jaw, 24.3 mm; angular length
of lower jaw, 25.4 mm; length of lower diastema, 5.0-5.7-6.1 mm; length
of lower row of permanent molars, 7.4—7.9-8.6 mm; height of the hori-
zontal branch at the level of M,, 7.0-7.8-9.2 mm; thickness of horizontal
branch on the level of M,, 3.8-4.3-4.7 mm; width of upper incisor, 2.1,
2.2, 2.6 mm; antero-posterior cross section of upper incisor, 2.2, 2.2,
2.6 mm; width of lower incisor, 1.9-2.5-2.9 mm; antero-posterior cross
section of lower incisor, 2.4—2.9-3.5 mm.

Note. From the above description of the Mid-Pliocene M. macoveii
and its comparison with fossil and living representatives of the subgenus
Microspalax, it is quite clear that the given species takes up an inter-
mediate position in regard to the degree of specialization of permanent
molars, between the Late Miocene-Early Pliocene М. compositodontus
and the still later Mid-Pliocene M. odessanus. Its permanent molars have
simpler structures as compared to M. compositodontus, and more complex
on the whole, than in M. odessanus. In addition to the primitive character-
istics in the structure of the permanent molars mentioned above, M.
тасоуей has also a comparatively primitive organizational structural
set up. The presence of a comparatively short diastema and ridge on the

200

masseter area, a shortened symphoidal tubercle, a well-defined maxillary
angle, and a sharply defined angular process which is strongly bent down,
are some of these structures. It follows that in the given case, we ap-
parently come across a species which is very primitive on the whole.
Furthermore, in the degree of specialization in incisors, M. macoveii is
superior to all the presently known species of the subgenus Microspalax.
This inclines us to presume the impossibility of taking it as a direct ancestor
of the more ancient M. odessanus.

There is a known confusion even at present with regard to the taxo-
nomy of this species. It occurs primarily because the majority of authors
who carried out investigations on the remains of mole rats from the
Mid-Pliocene of South Ukraine SSR, Moldavia SSR, and mixed regions
of Rumania (Simionescu, 1930; A. I. Argiropulo, 1940; E. G. Reshetnik,
1939, 1941) did not differentiate the genera Prospalax and Microspalax.
Even in current literature there are references to the presence of Prospalax
in Pliocenic fauna of the catacombs of Odessa, the Kuchurgan sediments,
and the territorial Mid-Pliocenic sands and gravels of Moldavia. Along
with these authentic remains of representatives of this genus, as has been
said above, were first found within the territory of the USSR only in 1964.
The descriptions of finds of Prospalax in the USSR (Argiropulo, 1940;
Reshetnik, 1939, 1941) are based on unauthentic determinations and the
very remains on closer examination, appear to belong to Microspalax—
a species identical, or closely related to M. macoveii. This can be explained
by the fact that the said authors concentrated exclusively on the presence
of three longitudinal ridges on the lower incisors in the Mid-Pliocenic
mole rats of Odessa, Kuchurgan and Moldavia (a trait which is equally
characteristic of Prospalax and of the most primitive species of the genus
Microspalax), and paid less attention to the morphologic peculiarities of
the outgoing branch and the angular process of the lower jaw, the differ-
ences in the structure of which are basic not only between the genera
Prospalax and Microspalax, but even between the subfamilies Prospala-
cinae and Spalacinae. It should also be noted that A. I. Argiropulo (1940)
and E. G. Reshetnik (1939) who had material from the Karst caves of
Odessa and Moldavia, represented mainly by lower jaws identical to M.
macoveii (Moldavia) as a species, and to a closer species—M. odessanus
(Odessa)—very correctly ascribed some of their resemblances to the
presently living Microspalax. However, inadequate review of works by
Mehely (1909) who separated the genus Prospalax, or of Simionescu (1930)
who described the species M. macoveii, and Kormos (1932) who reviewed
the taxonomical position of the finds in Rumania and described the
genus Pliospalax, led Argiropulo to an incorrect conclusion about the
morphologic similarity of the genera Prospalax and Microspalax. As
far as the report of A. I. Argiropulo (1940) on the find of remains of

201

Microspalax in Tiraspole is concerned, it is apparently based оп a mis-
understanding because these remains from the gravel of Tiraspole have
yet to be found. S. I. Ognev (1947) differentiated the genera Prospalax
and Microspalax however, due to an incorrect translation of the work of
Kormos (1932); he confused the problem of the generic position of Ruma-
nian mole rats from Malushten and Bereshti which were described by
Simionescu. The author also (1965) did not differentiate the typical Kuch-
urgan and Moldavian М. тасоуей and М. odessanus from the red-gray
loam (clay) finds of the Karst caves in Odessa and much later sediments.
In order to clarify this problem it would seem proper to look at the generic
position and synonyms of European Mid-Pliocenic Microspalax in detail.

The species М. macoveii, as has been said above, was first described
by Simionescu (1930) from the Mid-Pliocene of Rumania (place of find
—Malushten); moreover, the said author mistakenly took it to be in the
genus Prospalax. Simionescu (1930) described the remains as Prospalax
rumanus which undoubtedly belonged to the genus Prospalax as Kormos
(1932) indicated at that time. As far as M. macoveii is concerned, however,
inclusion of this species in the genus Prospalax is absolutely unfounded.
The following peculiarities of the construction of the lower jaw of M..
тасоуей are against this:

1. The alveolar process is somewhat longer than its articular one, or
is approximately equal to it. In Prospalax it is shorter than the latter.

2. The angular process is shifted outward, placed on the lateral walls
of the alveolar process, and is separated from the latter by a well-defined
sella externa. In Prospalax, this process is not situated on the lateral wall
of the alveolar, but at the base of its articular process, and has a common
edge with it. The sella externa is absent.

The given peculiarities of the structure of the lower jaw of a typical M.
macoveii from Malushten bring it close to representatives of the typical
subgenus of the genus Microspalax, and sufficiently clearly fixes the posi-
tion of the given species in the composition of this genus. This was also
observed by Kormos (1932); however he quite wrongly brought M. maco-
veii closer to the modern highly specialized representatives of the genus
Spalax sensu str. ( = Macrospalax Mehely). The mistaken interpretation
of the taxonomical position of M. macoveii could have been easily and
clearly proven by comparing the peculiarities of structure of the lower
jaw of this species with a modern representative of the genera Microspalax
and Spalax, the results of which have been given below. The similarity of
the lower jaw of S. macoveii to the jaw of a modern Microspalax on the
one hand, and their difference from the same bones of the present Bering
Spalax on the other, can be summarized as follows:

1. The angular process is quite separated and inclined from the external
wall of the alveolar process, tapered at one end, and strongly moved back

202

in relation to the proc. alveolaris; moreover, its apex in mature and old
representatives is situated behind the posterior wall of this process or, at
most, is placed at the level of the latter. In Spalax, this process is almost
completely adhered to the alveolar process, is rounded off at the end, and
is inclined somewhat forward in relation to the latter, as a result of which
its apex is situated in front of the posterior wall of the proc. alveolaris.

2. The sella externa is placed considerably below the base of the arti-
cular process. In Spalax the sella externa and the base of the proc. condy-
loideus are placed almost on the same level.

3. The alveolar process is connected to the coronary by a low blunt
ridge. In Spalax the ridge joining the alveolar and coronary processes is
higher and is sharp all along the edge.

Thus, there is no doubt about the fact that М. macoveii belongs to
the group of species of the genus Microspalax. Furthermore, traits such
as the presence of three longitudinal ridges on the lower incisors, a re-
latively lower alveolar process (approximately equal in height to its arti-
cular one, or slightly higher), a short diastema and the complex wearing
surfaces of the permanent molars—dquite clearly fixes its place in the
- compositions of the subgenus Microspalax.

It has been said above that Kormos (1932) described a new genus of
mole rats—Pliospalax—from the Mid-Pliocenic sediments of Rumania
found near Bereshti, and stratigraphically identical sediments of Malu-
shten, from a single fragment of the lower jaw with a piece of an incisor
and completely preserved permanent molars. Kormos was not confident
about showing the similarity of the mole rat from Bereshti and the M.
macoyeii from Malushten, because of which he proposed to name the
typical species of the new genus Pliospalax simionescui Kormos—with
the reservation that if the mole rat from Bereshti should appear similar
in species to the М. тасоуей of Malushten, then the name given by
Simionescu (1930) should be retained for the typical species. The reason
for the separation of the genus was the presence of an anterior mark on
the M, of the mole rat from Bereshti which the said author mistook for a
vestige of the additional anterior intruding fold of the outer line. The jaw
described by Kormos belonged to a semi-mature animal, proven by the
recently started wearing process of Ms, whereas the remains of a typical
M. macoveii, for that matter even the holotype described by Simionescu,
belonged to old animals on whose teeth the process of closure of the
intruding fold into a mark had almost come to an end. Hence, it is very
logical to presume that Kormos took one of the variables of age as a
taxonomical trait. The likelihood of such an assumption becomes clear
if the nature of age changes in the structure of the wearing surface of M,
on a series of teeth for М. macoveii (Figure 56) and representatives of
the subgenus Microspalax which is closely related to it—i.e., the Mid-

203

Pliocenic М. odessanus (Figure 60) and the recent М. ehrenbergi (Figure
53), is reviewed. It has been said above that the anterior intruding fold of
the inner line of the first lower permanent molar in primitive representa-
tives of the subfamily Spalacinae forms the anterior mark by way of
folding in its inner portion. This process takes place either by the fusion
of the mesoconid (if it is present) with the metaconid (in М. macoveii) or
by direct fusion of the entoconid with the metaconid (in M. odessanus
and M. ehrenbergi, on the teeth of which the mesoconid is not fully dev-
eloped or is completely reduced). The speed of completion of this process
in Mid-Pliocenic and modern Microspalax is, apparently, directly depen-
dent on the degree of development of the mesoconid. By the way, the
formation of the anterior mark on the teeth of М. тасоуей takes place
already in semi-mature animals, whereas in M. odessanus and M. ehren-
bergi this process takes place only in old age. Thus, if it is considered that
the anterior mark is found on the teeth of Mid-Pliocenic M. odessanus
and M. ehrenbergi where it represents the folding of the internal part of
the anterior intruding fold of the inner line, then, it is not understood how
it could be proven that this formation in the mole rat from Bereshti
represents a vestige of an additional anterior buccal fold. As a result,
Pliospalax simionescui is nothing but a young form of M. macoveii. With
the known similarity between M. macoveii and P. simionescui, naturally,
there is no necessity for their separation into independent genera. It also
has to be mentioned that the lower incisor of the mole rat from Bereshti
is, on the whole, identical to the incisor of a typical M. macoveii, i.e., it
has three longitudinal ridges of enamel on the anterior surface. That the
lower jaw from Bereshti belongs to a representative of the genus Prospalax
is impossible because on the M,—M, of the latter, the hypoconid and the
posterior collar are folded in the shape of a bud away from the rest of the
portions of the corona at this stage of wearing (Kowalski, 1960b). In
conclusion, it has also to be noted that in the works of S. I. Ognev (1947)
and Reshetnik (1939, 1941), Prospalax rumanus and M. macoveii have
been presented under a common generic name—Pliospalax—with a refer-
ence to the work of Kormos (1932). This is explained by an absolutely
inaccurate translation of the corresponding places in the paper by Kormos.
The latter never wrote anywhere about the inclusion of Prospalax rumanus
in the genus separated by him, thus accepting its previous generic dis-
position (Kormos, 1932: 194). He merely discussed a possible similarity
of the typical species Pliospalax simionescui and М. macoveit.

It has also been stated above that in his earlier works, the author
(Topachevskii, 1965) did not differentiate between M. macoveii and the
rather late M. odessanus. In the present work, the differences between
these species have been looked into in detail (pages 198-99), and also in
the portion where the Odessa mole rat has been described. Remains of M.

204

macoveii were restricted only and exclusively to the most ancient sediments
of the Mid-Pliocene-Kuchurgan sands and gravel, and in sediments strati-
graphically identical to it around Moldavia SSR, and in the valleys of
the Salchi and Kagul rivers.

Place of find. Around the villages Novo-Petrovka and Veliko-Mikhai-
lova, of Frunzenskii area, of Odessa region; right bank of the Kuchurgan
River; Kuchurgan sediments—sands and gravel of the alluvial period.
Around the village Grebenniki, Razdelnyanskii area, Odessa region; alluvial
sands and gravel similar to Kuchurgan’s. Around the villages Musaid (right
bank of the Salchi River) and Gavonosy (right bank of the Kagul River),
Moldavia SSR; alluvial sands and gravel, possibly similar to Kuchurgan’s.

Distribution and geological age. Northwest of the Black Sea region;
first half of the Mid-Pliocene.

4. Microspalax odessanus W. Topachevskii, sp. nov.—Odessa Mole Rat

Holotype. Institute of Zoology AN Ukraine SSR, No. 8442; skull
without occipital and parietal portions and zygomatic arch; Black Sea
region of Ukraine, Odessa; Mid-Pliocene, second half.

Paratypes. Fragment of facial skull with completely preserved per-
manent molars; Nos. 4582 and 4584; Odessa, second half, of the Mid-
Pliocene. All are preserved in the collections of the Institute of Zoology
AN Ukraine SSR.

Additional material. Lower jaws and their fragments, 14; isolated teeth
—upper incisors—10; M1, 7; M?, 6; МФ, 3; lower incisors—10; M,, 4;
М», 6; Ms, 5; and a few fragments of limb bones. Many series of isolated
teeth from Pliocenic sediments of the village Kotlovina of the Odessa
region. Individual incisors and permanent molars from the lower horizon
of the village Kryzhanovki, Odessa region; village Kairy, Kherson region;
and Nogaisk city, Zaporozhie region.

Diagnosis. The largest of the presently known representatives of the
subgenus Microspalax (length of upper and lower rows of permanent
molars is respectively equal to 7.9, 8.3, 8.4 mm and 7.9-8.4-8.8 mm). The
nasal bones are devoid of a sharply defined longitudinal depression in the
region of the suture between them (flattened or slightly concave). The
temporo-nasal and temporo-maxillary sutures form an almost straight
line. The hard palate between М! is wide (its width exceeds the width of
the alveoli of the first permanent molar); the central ridge of the palate
is well developed and wide. The mesocone on М! and М? is absent. The
mesoconid on M, is not fully developed; the neck width of the internal
fork (if one is present at all) is considerably less than one-fourth the total
length of the wearing surface. The fusion of the entoconid with the meta-
conid does not take place up to old age, and so the anterior mark in

205

young, semi-mature, and old animals is absent. The entoconid of this
tooth is fused in the early stages of wearing with the posterior collar, as a
result of which the posterior mark is present almost throughout life. The
anterior surface of the upper incisors is flattened (smooth) without any
longitudinal ridges.

Description. The skull is wide in the incisorial, behind the eyes, and
the rostral section (relation of width behind the eyes, the incisors, and the
rostrum to length of upper row of permanent molars is respectively equal
to 81.0, 102.5, 96.4, 97.6, 100.0 and 105.0; 143.3). The peculiarities of the
structure of the nasal bones, temporo-nasal and temporo-maxillary sutures,
and partly of the hard palate, have been mentioned in the diagnosis. In
addition, the posterior palatine groove is narrow (its width is less than
the width of the third permanent molar), and the opening behind the
palate is almost completely overgrown even in the young.

The upper incisors are, on the average, apparently less wide than in
the preceding species (relation of width of the incisor to the antero-
posterior cross section is 83.3-89.7-95.8). The anterior surface of the
incisor is smooth and without longitudinal ridges.

In the structure of the worn surface and roots, M!, on the whole, is
similar to the permanent molars of М. macoveii, 1.е., it has a completely
reduced mesocone and paracone, and a hypocone which until a later age
is not fused with the anterior collar and less than twice exceeds the proto-
cone; its metacone is fused with the posterior collar in the early stages of
erosion; it has two roots—a massive anterior inner and a comparatively
weaker posterior outer (rarely, the number of roots could be three) (Figure
58). Furthermore, the tooth is, on the average, relatively wider than in the

Figure 58. Microspalax odessanus sp. nov., upper permanent
molars. x8. Mid-Pliocene of South Ukraine, Odessa.

A—holotype.

206

preceding species. The measurements of М! are as follows: length, 2.3—2.6-
3.0 mm; width, 2.2-2.3-2.6 mm; relation of width to length, 80.0-90.3-
100.0. The order of closure of the intruding folds into marks is the same
as in the previous species. The paracone, in the majority of the given
examples, is fused with the neck connecting the inner anterior (protocone)
and the posterior (hypocone) folds. Rarely is the fold separated.

M?is moderately wide (length, 2.1-2.3—2.4 mm; width, 2.1-2.4-2.6 mm;
relation of width to length, 95.8-102.8-108.7). The hypocone less than
twice exceeds the protocone. The anterior mark (the constricted inner
portion of the intruding fold of the inner line) is formed in the early stages
of tooth erosion. The metacone fuses with the posterior collar forming a
posterior mark (preserved up to old age) in the very early stages of the
wearing process. The tooth has one outer and one inner intruding fold.
In the process of erosion, the outer fold closes into a mark earlier than
the inner one (Figure 58). There are three roots—a massive inner and two
weakly developed outer.

МЗ is relatively wider; its width is approximately equal to its length
(length, 1.9-2.0-2.2 mm; width, 1.8-2.0-2.3 mm; relation of width to
length, 95.0-100.0-115.0). The inner and outer intruding folds in young
animals are open and are fused with each other (Figure 58). The fusion
of the protocone with the hypocone, together with the closure of the inner
intruding fold into a mark, takes place with age. During this, the wearing
surface of the tooth assumes either a C-shaped or an E-shaped form. The
tooth has two roots which are fused approximately up to two-thirds their
length. The anterior root is massive, flattened in an antero-posterior direc-
tion with marks of bifurcation. The posterior root is weak and rounded
in the cross section.

The lower jaw has a relatively high horizontal branch (relation of
height of horizontal branch at the center level of the alveolus of М; to
the length of row of permanent molars is 80.0-96.0—107.6). ‘The diastema
is apparently longer than in the preceding species, but is shorter than in
М. ehrenbergi (magnitude of diastema-tooth index, 62.5-74.4-81.0). The
symphoidal tubercle is clearly defined (Figure 59) and elongated, its length
being approximately equal to the length of a full row of permanent
molars. The ridge in the space between the symphoidal tubercle and the
angular process is well developed. The mandibular angle is well expressed,
apparently a little less than in the previous species; however, it is better
defined than in the modern mole rat of Ehrenberg. The ridge on the
masseter area is elongated, and terminates considerably above the supra-
maxillary foramen in the direct vicinity of the alveolar edge. The angular
process is sharply defined, strongly bent down, and elongated at the base
(the relation of the length of the base of the angular process to the length
of the row of permanent molars is 104.5-114.3—130.3). The alveolar process

A wig rede

207

is low, and almost equal to its articular one in height. The supramaxillary
foramen is somewhat displaced above on the side of the alveolar edge.
The coronary process is placed steeply, its apex is almost non-inclined
backward. The horizontal branch is relatively thick (relation of its thick-
ness at the level of M, to the length of row of permanent molars is 42.0-
51.4-55.0).

Figure 59. Microspalax odessanus sp. nov. x 1.7.
Mid-Pliocene of South Ukraine, Odessa.

A—lower jaw, external view; B—the same,
internal view; C—lower incisor.

The lower incisor is, apparently, less in width, on the average, than in
the preceding species (relation of width to antero-posterior cross section,
71.4-81.2-90.0) with three longitudinal ridges on the anterior surface.

The mesoconid on M, is almost completely reduced; its marks are
sometimes preserved in the shape of a small protuberance on the anterior
wall of the entoconid (Figure 60). In the last case, the neck width of the
inner fork is considerably less than one-fourth the total length of the wear-
ing surface of the tooth. The fusion of the entoconid and the metaconid
takes place only in very old age, as a result of which the anterior intruding
fold of the inner line of young, semi-mature, and mature animals does not
form the anterior mark. The entoconid and the posterior collar are fused
even on the teeth of young individuals, as a result of which the posterior
mark is present almost throughout life. The protoconid and the hypoconid
are of about equal magnitude. There are two roots: the posterior is more
massive than the anterior with marks of bifurcation. Teeth measurements
are as follows: length, 2.4-2.6-2.9 mm; width, 2.1-2.3-2.5 mm; relation
of width to length, 78.5-86.0-95.8. The order of closure of the intruding

208

folds into marks is as follows: the posterior inner, the inside portion of
the anterior inner, the anterior inner, and finally, the outer.

Figure 60. Microspalax odessanus sp. поу., lower permanent
molars. x8. Mid-Pliocene of South Ukraine, Odessa.

On the whole, M, is similar to the preceding species. The measure-
ments are as follows: length, 2.2-2.4-2.9 mm; width, 2.1-2.3-2.6 mm;
relation of width to length, 89.6-98.2—109.1. The entoconid is fused with
the posterior collar in the early stages of wearing; subsequently, the
posterior mark is present throughout life. There are two roots. Both are
flattened in an antero-posterior direction with marks of bifurcation; more-
over, the tendency to bifurcation is more strongly expressed on the anterior
root than on the posterior, (which is also seen in the structure of the
alveolus.

М, (length, 2.2-2.4-2.9 mm; width, 2.0-2.2-2.4 mm) is elongated (re-
lation of length to length of preceding molar, 100.0; 109.1), and drawn

209

out in а length-wise direction (relation of width to length, 82.7-89.8-95.6).
The wearing surface is S-shaped. The closure of the inner intruding fold
into a mark takes place only in old age (Figure 60). Marks of an additional
intruding fold of the inner line, which is placed anterior to the metaconid,
are absent. The anterior and posterior roots are fused almost all along as
a result of which the tooth is, in fact, characterized by the presence of one
complex root. The anterior and posterior parts in turn also show a ten-
dency toward bifurcation. On the anterior portion, traces of bifurcation
are expressed more sharply, as a result of which the corresponding socket
in the alveolus shows a tendency toward the formation of two lunes.

Comparison. It differs from the present, living M. ehrenbergi by:

1. Absence of two longitudinal ridges on the upper incisors (always
present in M. ehrenbergi). Furthermore, the upper incisors of the Odessa
mole rat are wider (relation of width of incisor to antero-posterior cross
section, 83.3-89.7-95.8 as against 76.0-83.2-94.0 in М. ehrenbergi).

2. Absence of a sharply defined longitudinal depression on the nasal
bones.

3. Almost straight temporo-nasal and temporo-maxillary sutures (in
M. ehrenbergi, the temporo-nasal and temporo-maxillary sutures form an
angle with the apex directed backwards).

4. A widened hard palate, the width of which in the region of the
anterior permanent molars considerably exceeds the width of the alveolus
of this tooth. In М. ehrenbergi the width of the hard palate between М1
is approximately equal to the similar alveolus of the anterior permanent
molar.

5. A skull widened in the incisorial and rostral sections (relation of
incisorial and rostral width to length of line of permanent molars is equal
to 81.0-102.5 and 105.0-143.0 as against respectively 69.2—76.4—86.1 and
97.3—108.6-126.0).

6. A narrow post-palatal opening (width is less than the length of the
third permanent molar). In M. ehrenbergi, it is approximately equal to the
length of M3.

7. A horizontal branch which is, on the average, higher and thicker at
the level of M, (relation of its length at the level of M, and thickness at
the level of М» to the length of row of permanent molars is equal in М.
odessanus to 80.0-96.0-107.6 and 42.0-51.4—55.0, as against respectively
78.5—88.1-101.3 and 37.5-45.7-57.8 in М. ehrenbergi).

8. Presence of two roots for М! and МЗ in the majority of the given
cases. There are three roots in М. ehrenbergi.

9. A clearly defined, bent down, symphoidal tubercle and a well-
expressed maxillary angle. In M. ehrenbergi the symphoidal tubercle is
flattened and the maxillary angle is expressed faintly.

10. A coronary process which is steeply placed in relation to the

14

210

horizontal branch, the apex of which is almost not bent backward. In М.
ehrenbergi, the coronary process is concave like a saddle and is more
tapered in relation to the horizontal branch.

11. Wider lower incisors (relation of width to antero-posterior cross
section is equal to 71.4—81.2-90.0 as against 64.0-74.5-86.2 in М. ehren-
bergi).

12. Presence of a posterior mark on M, throughout life (formed as a
result of the fusion of the entoconid with the posterior collar). In M.
ehrenbergi, it appears only in old age.

13. The М. and М; are, on the average, apparently more drawn out
in a length-wise direction (the relation of the width of tooth to its length
is equal to 89.6-98.2—109.1 for М» and 82.7-89.8-95.6 for Mg, as against
° respectively 80.0-104.3-125.0 and 70.0-96.4—116.7 in М. ehrenbergi).

14. Larger absolute measurements.

The differences between M. odessanus and M. compositodontus and M.
macoveii have been examined above.

Measurements. Length of upper diastema, 14.1, 15.0, 17.5 mm; length
of hard palate, 24.8—26.8 mm; length of upper row of permanent molars,
7.9, 8.3, 8.4 mm; incisorial width, 7.0, 8.0 mm; rostral width, 2.6, 2.7,
3.0 mm; width behind the eyes, 7.9, 8.0, 8.2 mm; width of upper incisor,
1.8—2.1-2.4 mm; antero-posterior cross section of the upper incisor, 2.0-
2.4-2.6 mm; condylar length of lower jaw, 29.3, 29.9, 31.6 mm; angular
length of lower jaw, 27.5, 28.3, 30.1 mm; length of lower diastema, 5.6-
6.4-6.9 mm; length of lower row of permanent molars, 7.9-8.4-8.9 mm;
height of branch at the level of M,, 6.7-8.1-9.0 mm; thickness of hori-
zontal branch at the level of Mz, 3.7-4.2—4.9 mm; width of lower incisor,
1.6-2.1-2.7 mm; antero-posterior cross section of lower incisor, 2.0-2.6—
3.3 mm.

Note. M. odessanus is the most highly specialized representative of the
subgenus Microspalax. This is indicated by the presence of a wide skull in
the incisorial and rostral region of this species, nasal bones without a
longitudinal slit-like depression, a straight sutura maxillo-naso-frontalis,
a relatively high and thick horizontal branch of the lower jaw, widened
upper and lower incisors, a grinding surface of the permanent molar
which is very simple in structure and by a high tendency toward reduction
of roots with formation of teeth having long period of growth. With
regard to the advanced development of some of the above-mentioned
traits, primarily concerned with adaptations toward burrowing (widening
of incisors, related changes in the structure of the skull and lower jaw),
M. odessanus surpasses not only the living M. ehrenbergi, but also the
most primitive representatives of the subgenus Mesospalax, the present
M. nehringi, which is highly specialized as a whole. At the same time, this
species still preserves a number of primitive characteristics in the structure

211

of the skull and the lower jaw. In particular, besides the traits which
determine its position in a subgenus about which much has been said in
the preceding sections, M. odessanus is further characterized by a quite
sharply defined symphoidal tubercle, a well-developed maxillary angle,
and a well-separated and strongly bent down angular process of the lower
jaw. The foregoing forces us not to accept the Odessa mole rat as an
original form of the living representatives of the subgenus Mesospalax.
This is, perhaps, further proven by the fact that the representatives
of the subgenus Microspalax immediately give place to species of the
genus Spalax within the boundaries of the present distribution of
M. leucodon in the Late Pliocene (second half) and, moreover, in some
excavations their remains have been found together (lower horizon of
the Nogaisk geological strata). All this also proves the rather later pene-
tration of M. leucodon (which spread up not before the Pleistocene) in
the region of the northwest Black Sea of the USSR (Ukraine, Moldavia),
i.e., the regions which, as is well-known, are the easternmost part of the
area of the subgenus Mesospalax in Europe.

Place of find. Odessa, red-gray gravel, aggregates of Karst caves and
craters in Pontiac limestone (catacombs of Odessa); ancient, alluvial layer
which opened up near the village Kotlovina of the Odessa region (right
bank of Lake Yalpukh); lower horizon of alluvial sediments near the
village Kryzhanovki of the Odessa region; alluvial layers of the village
Kairy of the Kherson region; and Nogaisk of the Zaporozhie region.

Distribution and geological age. Northwest Black Sea of Ukraine SSR;
Mid-Pliocene (latter half); Late Pliocene (rare in the sediment lying above
the Willafrank strata).

2. Subgenus MESOSPALAX Mehely, 1909

Genotype. Spalax typhlus leucodon* Nordmann, 1840; recent, around
the city of Odessa.

Diagnosis. Measurements are average. The anterior surface of the lower
incisor is smooth, without longitudinal ridges. The lambdoid and sagittal
ridges are well developed in mature and old individuals. The sagittal ridge
is equally prominent on the parietal and temporal bones. The parietal
bones are contracted; the width of the two parietale is considerably much
less than twice the length of the upper row of permanent molars. In addi-
tion, the width of each of the parietale, individually in mature and old
representatives, is significantly less than its length. The alveolar process of
the lower jaw is high and considerably exceeds its articular one in height.

Comparison. A detailed comparison of the subgenera of the genus
Microspalax has been given above (page 175).

*Should be Mesospalax typhlus leucodon—Editor.

212

Composition of the subgenus. Two modern species—M.' nehringi
(Satunin, 1898) and М. leucodon (Nordmann, 1840).

Distribution and geological age. Zakavkaz, Asia Minor, Balkan, north-
west Black Sea region (Rumania), Moldavia SSR, Odessa region, Prikar-
pate regions of Hungary, Rumania and Ukraine SSR (Bukovina); Holo-
cene including recent period.

KEY FOR IDENTIFICATION OF SPECIES
OF THE SUBGENUS MESOSPALAX

1 (2). The nasal bones have sharply defined longitudinal slit-like depres-
sions in the region of the sutures between them (Figure 61) pointed
anteriorly. The temporal nasal and temporo-maxillary sutures form
an angle with its apex bent backward. The edges of the rostrum are
almost parallel and do not meet in a forward direction. The for-
amina behind the palate are small. The fossae behind the palate
are not present. The central ridge of the palate forms a lamellar
broadening at the level of the foramina behind the palate.........
а в 1. М. nehringi (Satunin).

(Holocene, including recent).

2 (1). The nasal bones are without a longitudinal slit-like depression
(Figure 65) and are rounded or blunted anteriorly. The temporo-
nasal and the temporo-maxillary sutures form an almost straight
line, or an angle with its apex directed forward. The edges of the
rostrum meet sharply in a forward direction. The foramina behind
the palate are comparatively large. The fossae behind the palate
are sharply defined and drawn out in a longitudinal direction. The
central ridge of the palate, at the level of the foramina behind the
palate, does not form a lamellar broadening....................
о ON MEAP rut Gr aie ats a Wana ence 2. M. leucodon (Nordmann).

(Holocene, including recent).

1. Microspalax nehringi (Satunin, 1898)—Mole Rat of Nehring

Spalax Nehringi Satunin, 1898: 314, 315, Figures 1-3. S. monticola nehringi Mehely,
1909: 70-79, Tab. I, Figure 2, Tab. XXII, Figures 1-14. S. monticola armeniacus Mehely,
1909: 79-84. 5. monticola cilicicus Mehely, 1909: 84—88. S. monticola anatolicus Mehely,
1909: 88-100. 5. monticola turcicus Mehely, 1909: 105-114. 5. labaumei Matschie,
1919: 35-38. S. leucodon nehringi Ognev, 1947: 627-633, Figure 309.

Holotype. Museum of Georgia in Tbilisi, No. 119 1/c-80; Zakavkaz,
Kizikoporan, village of the Tandurek-Chaya River (tributary of the Araks).
Material investigated. More than 50 skulls and skins obtained from

213

around the republic of Kavkaz (Caucasia) and Turkey. The material is
preserved in the collections of the Zoological Institute AN USSR of
Moscow State University and the Zoological Museum of the University
of Humboldt in Berlin.

Diagnosis. The nasal bones have a sharply dened longitudinal slit-like
opening in the region of the suture between them. The temporo-nasal
and temporo-maxillary sutures form an angle with its apex directed back-
ward. The upper and lower incisors are narrowed (relation of width and
antero-posterior cross section, 72.2-87.2-95.8 for the upper, and 70.0-
79.6-85.2 for the lower teeth).

Description. Measurements are average (length of body 170-191-
225 mm; length of foot, 23.0-25.7-30.0 mm; condylobasal length of skull,
34.4-44.0-53.3 mm). The skull is narrow in the incisorial and rostral
sections (relation of incisorial and rostral width and length of row of
permanent molars is respectively equal to 67.1-83.0-98.8 and 98.7-115.7-
135.0). The edges of the rostrum are almost parallel and do not meet in a
forward direction (Figure 61). The constriction behind the eyes is clearly
defined; the width behind the eyes is approximately equal to the length of
the anterior permanent molars. With regard to the degree of development
of this trait, the mole rat of Nehring is closer to the Balkan type of M.
leucodon than the east European representatives of this species. The upper
diastema is relatively short (magnitude of the diastema-tooth index, 160.0—
202.7—247.0). In this respect, the species exhibits characteristics that are,
after all, similar to the Balkan type of М. Jeucodon. In the east European
M. leucodon, the diastema is relatively longer, the nasal bones have a
clearly marked longitudinal slit-like depression, sharpened anteriorly and
long; their length, as a rule, exceeds the total length of the temporal and
parietal bones (a typical subspecies of the Caucasus), or is approximately
equal to the latter (subspecies of Anatoliya). The temporo-nasal and
temporo-maxillary sutures form an angle with its apex directed upward
(Figure 61). The occipital bone is narrow; its width approximately twice
exceeds the height measured from the upper edge of for. magnum up to
the apex of the lambdoid process. The hard palate is narrow; its width
between the anterior permanent molars is considerably less than the length
of МЕ. The openings (foramina) behind the palate are small. Depressions
behind the palate are not present. The central ridge of the palate at the
level of the foramina behind it form a lamellar broadening. The portion
behind the palate is bifurcated into two by a well-developed styloid
process. The alveolar bulges are absent or faintly marked. The ridges in
the space between the anterior edge of the alveolus of М! and the incisorial
openings are well developed. The structural characteristics of the upper
incisors have already been given in the diagnosis.

In complexity, the grinding surface of the upper permanent molars

214

resembles similar structures in the specialized representatives of the sub-
genus Microspalax, namely M. ehrenbergi and M. odessanus. The paracone

EN
NOS
&

&
а
SS

F G

Figure 61. Microspalax nehringi (Sat.). x 1.6.

Legend is the same as in Figure 50.

215

оп М, is not fused until old age with the anterior collar, as a result of
which the tooth in these stages of wearing is characterized by the presence
of two intruding folds in the outer line. However, it differs from representa-
tives of the subgenus Microspalax in that the metacone and the posterior
collar, as a rule, are completely fused in almost all stages of tooth erosion,
as a result of which in the majority of cases, at least one of the marks of
the additional outer intruding fold or posterior mark are absent (markings
of this fold were only observed by us in some very young individuals from
the series of fifty skulls). Figures 62 and 63 allow us to judge the character-
istics of individual and age variability in the construction of the masti-
catory surfaces of the upper permanent molars.

Figure 62. Microspalax nehringi cilicicus Meh. x8.

A to J—upper, and K to T—lower rows of permanent molars; A to D and K
to O—young and semi-mature; E to J and P to T—adult and old individuals.

The peculiarities in the structure of the roots of the upper permanent
molars may be summarized as follows: М! and М? in the majority of cases
are characterized by the presence of three roots—a massive inner and two
weakly developed outer ones (Figure 64); the inner root, as a rule, has
marks of bifurcation; the outer ones sometimes show a tendency to fuse
with the inner. In some individuals, the anterior outer root is completely
fused with the inner, as a result of which the teeth have two roots. How-
ever, on М? the general tendency toward root fusion is more apparent

216

than оп М1. МЗ т the majority of cases has two roots because the postero-
external is, as a rule, fused with the inner one. In individual cases the
fusion of the respective roots does not take place and so three separate
roots appear. The dimensions and proportions of the teeth are as follows:
M1—length, 2.2-2.7-3.2 mm; width, 2.0-2.3-2.7 mm; relation of width
to length, 74.0-85.3-104.0; M*—length, 1.9-2.2-3.0 mm; width, 2.0-2.3-
2.6 mm; relation of width to length, 86.7-103.8-114.3; M?—length, 1.4—
1.7-2.1 mm; width, 1.5-1.9-2.2 mm; relation of width to length, 95.2-
109.4—125.0.

Figure 63. Microspalax nehringi nehringi Sat. х 10.

A to G—upper, and H to K—lower rows of permanent molars; A and
H—semi-mature; В to С and J to K—adult and old individuals.

The lower jaw has a relatively high horizontal branch; the ratio of its
height at the level of the anterior permanent molar to the length of row
of М,-М. is 80.0-96.5-113.9. The lower diastema is, on the average,
relatively longer than in representatives of the subgenus Microspalax, and
lower and shorter than in the most specialized species from the subgenus
Mesospalax—the living М. Jeucodon; the magnitude of the diastema-tooth
ratio is 70.4-87.0-106.3. The symphoidal tubercle is flattened, the maxil-
lary angle is slightly expressed, the supramaxillary foramen is shifted to
the lower edge of the jaw. With regard to the degree of development of

217

these traits, the mole rat of Nehring is, after all, closer to the western
Balkan form, М. leucodon, than the east European nominal subspecies.

Figure 64. Structure of roots and alveoli of the permanent
molars of Microspalax nehringi (Sat.) (Mehely, 1909).

The characteristics of the structure of the lower incisors have been
described above in the diagnosis. The lower permanent molars are, on
the whole, simpler compared to the same in representatives of the subgenus
Microspalax. The entoconid on М, at all stages of wearing is fused with
the posterior collar, as a result of which the tooth has characteristically
only one intruding fold on the inner line. However, the vestige of this fold
in the shape of one, or rarely, two posterior marks could be preserved up
to very old age. The mesoconid is absent in old age in the majority of cases.
In young animals its vestiges are represented in the form of a small tooth.
The tooth is, on the average, narrower than in the European M. leucodon;
the relation of width of the corona to its length is 68.0-86.5-95.8. The
range of individual and age variability in the structure of the wearing
surface of М, М, is very great; this can be judged on seeing Figures 62

218

and 63. The lower permanent molars in the majority of cases have two
roots each. The posterior root оп М; and М: and the anterior on М, and
М. exhibit a tendency toward bifurcation. Sometimes, the ends of the
respective roots are bifurcated in the shape of a fork, each portion of
which has, often, a corresponding socket in the alveolus (Figure 64).
Measurements and proportions of lower permanent molars are as follows:
M,—length, 2.2-2.5-3.1 mm; width, 2.0-2.2—2.4 mm; relation of width
to length, 68.0-86.5-95.8; M.—length, 1.9-2.2-2.5 mm; width, 2.1-2.3-
2.4 mm; relation of width to length, 92.0-103.3-120.0; M,;—length, 1.7—
2.0-2.3 mm; width 1.8-2.0-2.1 mm; relation of width to length, 86.3-
101.7-123.5.

Comparison. It differs from the European М. leucodon as follows:

1. Presence of a clearly defined longitudinal slit-like depression in the
nasal bones (always absent in M. leucodon).

2. Construction of temporo-nasal and temporo-maxillary sutures which,
in M. nehringi, form an angle with an apex directed backward. In M.
leucodon the corresponding sutures are straight (nominal subspecies) or
form an angle with its apex directed forward (Balkan subspecies).

3. Narrow upper and lower incisors (relation of width to antero-
posterior cross section is equal to 72.2-87.2-95.8 for the upper, and 70.0-
79.6-85.2 for the lower teeth, as against respectively 86.4—101.5-119.0
and 80.0-92.1-115.0 in М. leucodon).

4. A skull which is narrow in the incisorial and rostral sections (relation
of incisorial and rostral width to length of row of permanent molars is
respectively equal to 67.1-83.0-98.8 and 98.7—115.7-135.0, as against 80.3-—
100.3-130.0 and 106.8-129.9-162.0 in М. leucodon).

5. A narrow occipital bone, the width of which approximately twice
exceeds its height, measured from the upper edge of the for. magnum up
to the apex of the lambdoid ridge (in М. leucodon, the first measurement
exceeds the second by more than twice).

6. Relatively longer nasal bones which are pointed anteriorly and the
length of which exceeds the total length of the temporal and parietal bones,
or is equal to it. In М. leucodon, the nasal bones are rounded off anteriorly,
are blunted, and their length is less than the total length of the temporal
and parietal bones.

7. A narrowed hard palate, the width of which between the anterior
permanent molars is considerably less than the length of M?. In М.
leucodon, the width of the palate at the same place exceeds the length of
the anterior permanent molar or, at best, is equal to the latter.

8. Smaller measurements of the foramina situated behind the palate
and by the almost undefined depressions behind the palate. In М. Jeucodon,
the foramina behind the palate are comparatively large and the depressions
behind the palate are deeper and elongated in a longitudinal direction.

219

9. The central ridge of the hard palate has a lamellar broadening at the
level of the foramina behind the palate and of the depression behind the
palate. In M. leucodon, the lamellar broadening of the central ridge is
absent.

10. A well-developed styloid process which divides the area behind the
palate into two portions (weakly developed or absent in М. /eucodon).

11. On an average, weakly developed alveolar and more strongly dev-
eloped ridges in the place between the anterior edge of the alveolus of M?
and the incisorial opening. |

Measurements. Condylobasal length of skull, 34.4—44.0-53.3 mm; basic
length of skull, 34.8-40.4-47.5 mm; length of nasal bones, 14.8-19.3-
25.6 mm; total length of parietal and temporal bones, 15.9-18.8—24.8 mm;
length of the parietal bones, 6.7-8.7-10.6 mm; length of upper diastema,
11.2-17.0-25.0 mm; length of hard palate, 20.6-27.7-34.7 mm; length of
upper row of permanent molars, 7.0-8.0-8.9 mm; width of nasal apertures,
4.0-5.0-6.0 mm; incisorial width, 4.9-6.6-8.6 mm; width of nasal bones
anteriorly, 4.7-6.4-8.0 mm; rostral width, 7.3-9.5—11.3 mm; width behind
eyes, 6.4—7.2-8.7 mm; width of two parietale, 7.6-11.0-13.2 mm; width
of bones up to lambdoid process, 5.6-6.2—7.7 mm; molar width, 28.5-
37.5-45.3 mm; maximum width of occiput, 23.4-29.7-35.0 mm; length
of auditory bullae, 9.2—11.7-13.6 mm; width of auditory bullae, 6.7-7.6-
8.4 mm; width of upper incisor, 1.6-2.0-2.7 mm; antero-posterior cross
section of upper incisor, 1.9-2.5-3.2 mm; height of occipital bones,
11.1-18.7-24.2 mm; height of nasal aperture, 2.4-3.6-5.2 mm; condylar
length of lower jaw, 22.7-29.0-36.1 mm; angular length of lower jaw,
20.7-27.0-32.6 mm; length of lower diastema, 5.0-6.6-8.4 mm; length
of lower row of permanent molars, 6.4—7.6-8.3 mm; height of horizontal
branch at the level of center of alveolus of М, 5.9-7.2-8.8 mm; thickness
of horizontal branch at the level of М, 2.9-3.6-4.4 mm; height of alveolar
processes from inside, 2.8-5.6-7.9 mm; width of lower incisor, 1.5—2.1—
2.8 mm; antero-posterior cross section of lower incisor, 2.0-2.7-3.6 mm.

Note. M. nehringi is the most primitive representative of the subgenus
Mesospalax. With regard to the degree of development of adaptations of
the skull and the lower jaw for burrowing (relative width of incisors and
morphologic characteristics of the rostral section of the skull related to
them), it occupies a middle position, between M. ehrenbergi and the
European М. leucodon. It has to be noted further that in the aspects noted
above, this species looks more primitive than even the European Pliocenic
representatives of the subgenus Microspalax—M. compositodontus, M.
тасоуей, and М. odessanus. In addition, it has all the peculiarities which
are characteristic of the subgenus Mesospalax (complete disappearance of
longitudinal ridges, presence of narrowed parietal bones, a higher alveolar

220

process of the lower jaw, and others). All this leads to an assumption
about the morphological closeness of M. nehringi with the forms original
to Mesospalax and also, perhaps, about an early (Pliocene) bifurcation
of the branches of Microspalax and Mesospalax with their further parallel
development.

The species was first described by K. A. Satunin (1898); however, he
took the characteristics of skull structure as differentiating features which
are greatly subject to transgression in the newly described species and in
some forms of the European M. leucodon. The latter fact made Mehely
(1909), and after him, V. I. Radugin (1917), K. A. Satunin himself (1920),
and 5. I. Ognev (1947) examine it as a subspecies of М. leucodon ( = М.
monticola Nehr.). Mehely preserved the name given by Satunin during his
first description of the nominal subspecies—the Caucasian mole rat—
while separating the Armenian and a number of Asia Minor forms as
independent subspecies (please see the section on subspecies, page 221).
However, research on the skulls of Caucasian and Asia Minor mole rats
permits a differentiation in the interdependence of traits which were not
subjected to, or were less subjected to, transgression in the Asia Minor
(including Caucasian) and European group of mole rats of the subgenus
Mesospalax. Such traits were, first of all, the presence of sharply defined
longitudinal slit-like depressions on the nasal bones of the Asia Minor
Mesospalax and a number of specific peculiarities in the structure of the
temporo-nasal and temporo-maxillary sutures of the rostrum as a whole,
of the hard palate, and of the upper and lower incisors—all of which
have been described in the previous sections of this work. Thus, we have
no doubt about the necessity for reorganization in the species of M.
nehringi which joins the Asia Minor and, for that matter, even the Cau-
casian Mesospalax. M. labaumei (Matschie, 1919) which differs from M.
nehringi in regard to individual and age differences has to be examined.

Distribution and geological age. Turkey, North Iraq, Republic of USSR
near Caucasus. Also found around the USSR region in Akhalkalskii,
Aspindzskii, Tsalkinskii, and Bashkichetskii regions of Georgia and
around Leninkana, Artiksk, Achinsk, Akhuryansk, Amasii, Tukasyansk,
and Spitaksk and Talin region of Armenia SSR (boundary area between
USSR and Turkey). Recent; fossil remains not known.

Subspecies. It has been said above that Mehely (1909) did not recognize
M. nehringi as an independent species and considered it as a subspecies
of M. leucodon. Furthermore, he described still four subspecies from the
region of Caucasus and Asia Minor: М. /. armeniacus Meh., 1909 (south-
west Armenia SSR, mixed regions of Turkey from the Arart Mountains
in the east); M. /. cilicicus Meh., 1909 (central Tavr, place Bulgar Maden);
М. 1. anatolicus Meh., 1909 (west Turkey around Izmira); and М. 1.
turcicus Meh., 1909 (southwest Turkey, around Fekhti). Afterwards,

221

Hinton* described more forms from the central regions of Turkey: М. /.
corybantium Hinton and М. I. captorum Hinton. However, these authors
had extremely scanty material (M. /. turcicus was described from six; M. /.
armeniacus and М. 1. antolicus from three; and М. /. cilicius from just one
skull) which puts one in doubt about the actual presence of these species
in reality. This has been proven in the works of S. I. Ognev (1947) who
has shown that М. /. nehringi and М. 1. armeniacus are identical. We had
an opportunity to examine a collection of recent mole rats which were
found in the geographical areas from where the forms cilicicus, anatolicus,
turcicus, corybantium and captorum had been taken. On the basis of a
related literature and a morphometrical examination carried out on the
collection, it was found that Mehely and Hinton described individual and,
partly age variables, as subspecies differences, whereas the number of
subspecies should be reduced to two as given below.

1. М. nehringi nehringi Satunin, 1898 (including М. и. armeniacus Meh.,
1909). It is characterized by comparatively large (within the subgenus)
measurements (condylobasal length of skull, 40.3-46.3-53.3 mm; length
of upper row of permanent molars, 7.5-8.1-8.8 mm; condylar length of
lower jaw, 27.2—30.5-35.9 mm; length of lower row of permanent molars,
7.3-7.8-8.3 mm) Бу arelatively long upper diastema, by askull whichis con-
stricted behind the eyes and widened in the incisorial and rostral sections,
by comparatively wider and elongated nasal bones (their length exceeds
the total length of the temporal and parietal bones in the majority of
cases). It spreads up into the southern regions of Georgia SSR (Akhal-
kalakskii, Aspindskii, Tsalkinskii and Bashkichetskii regions) around
Leninkana, Artiksk, Achinsk, Akhuryansk, Amasii, Tukasyansk and
Spitaksk regions of Armenia SSR. On the east, up to Kurovakan; on the
south, the whole of the Talin region; in the mixed regions of Turkey
(from the Gelskaya basin-crater on the west up to the Arart mountains in
the east). Perhaps, this form spreads up also into north Iraq (Reed, 1958).

2. М. nehringi cilicicus Mehely, 1909 (including М. п. anatolicus Meh.,
1909; M. n. turcicus Meh., 1909; M. n. corybantium Hinton and M. n.
captorum Hinton). This differs from the nominal subspecies by:

a. On the average, rather smaller absolute measurements (condylobasal
length of skull, 34.4-40.6-47.2 mm; length of upper row of permanent
molars, 7.0-7.7-8.2 mm; condylar length of lower jaw, 22.7-26.7-31.6 mm;
length of lower row of permanent molars, 6.4—7.4—8.2 mm).

b. A shortened upper diastema (magnitude of diastema-tooth index,
160.0-190.9-239.7 as against 172.8—200.0-247.0 in the nominal subspecies).

c. A lesser incisorial width (relation of incisorial width to length of
row of permanent molars is 67.1-77.0-97.4, as against 77.5-87.3-98.8).

*Reference omitted from the bibliography—(G. Ed.).

222

4. Nasal bones which are narrow and relatively short. The relation of
width of nasal bones anteriorly to length of row of permanent molars is
67.1-76.3-91.0 as against 72.7-82.4-92.5. In addition, the length of the
nasal bones in М. и. cilicicus is approximately equal to the total length of
the temporal and parietal bones (in М. п. nehringi, the former measurement
as a rule exceeds the latter).

e. A lesser rostral width (relation of rostral width to length of row of
permanent molars is 98.7-111.7-137.2, as against 103.7-118.5-135.0).

f. A larger width behind the eyes (relation of width behind the eyes to
length of row of permanent molars is 83.7-97.2-105.1, as against 71.9-
81.2-90.6).

It is distributed in the region of Asia Minor (Figure 32). The boun-
daries of the distribution of the indicated species have not yet been exactly
determined.

2. Microspalax leucodon (Nordmann, 1840)—Hilly or
White-toothed Mole Rat

Spalax typhlus leucodon Nordmann, 1840: 32-35. 5. typhlus hungaricus Nehring,
1897: 173, Abb. 3. S. hungaricus Nehring, 1898a: 479-481, Figure 1. S. monticola
Nehring, 1898 Sitzungsber. Gesellsch. naturforsch. Freunde Berlin: 6. S. dolbrogeae
Miller, 1903: 161. S. leucodon Nordmann, Reshetnik 1939: 9, 17.

Holotype. Zoological Museum of Odessa University; skull from the
collections of Nordmann; around the city of Odessa.

Material investigated. Above ninety skulls and skins in the custodial
finds of the Zoological Institute AN SSSR, Institute of Zoology AN
Ukraine SSR, Institute of Zoology AN Moldavia SSR, Kiev and Odessa
Universities.

Diagnosis. The nasal bones are without a longitudinal slit-like depres-
sion. The temporo-nasal and temporo-maxillary sutures form almost a
straight line or an angle with its apex directed forward. The upper and
lower incisors are wide (relation of width to antero-posterior cross section,
86.4-101.5-119.0 for the upper, and 80.0—92.1-115.0 for the lower teeth).

Description. Measurements are average (length of body, 150-201-
240 mm; length of foot, 19.0-24.5-27.5 mm; condylobasal length of skull,
35.7-43.8-51.4 mm). The skull is wide in the incisorial and rostral sections
(relation of incisorial and rostral widths to length of row of permanent
molars is respectively equal to 80.3-100.3-130.0 and 106.8-130.0-162.0).
The edges of the rostrum meet anteriorly (Figure 65). The constriction
behind the eyes is clearly defined in the Balkan types (width behind the
eyes is approximately equal to the length of the two anterior permanent
molars), and finally in the east European types (the first measurement is,
as a rule, always greater than the second one). The upper diastema is

223

relatively short in the Balkan subspecies (magnitude of diastema-tooth
index, 162.5-201.7-240.0) and is elongated in the east European nominal

(fA

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SS MMe

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Figure 65A. Microspalax leucodon monticola Nehr. x 1.6.
Legend is the same as in Figure 50.

224

G

Е

Figure 65B. Microspalax leucodon leucodon Nord. Х 1.6.

Legend is the same as in Figure 50.

Ee

—

225

type (164.4—214.0-280.3). The nasal bones are without a longitudinal slit-
like depression, rounded or blunted in front, and short; their length is less
as a rule than the total length of the temporal and parietal bones. The
temporo-nasal and the temporo-maxillary sutures form analmost straight
line (nominal subspecies) or an angle with its apex directed forward
(Balkan subspecies). The occipital bone is wide; its width in the majority
of cases exceeds more than twice its height measured from the upper edge
of the for. magnum up to the apex of the lambdoid process. The hard
palate is wide; its width between the anterior permanent molars exceeds
the length of М! or is approximately equal to the latter. The foramina
behind the palate are sharply defined and elongated in a longitudinal
direction. The central ridge of the palate at the level of the foramina
behind the palate does not form a lamellar thickening. The styloid process
of the palate is weakly developed, or is totally absent. The alveolar bulges
in the majority of cases are well developed. The ridges in the space between
the anterior edges of the alveoli of М! and the incisorial openings are
weakly developed in old age and maturity. The structural characteristics
of the upper incisors have been given in the diagnosis.

The general configuration of the grinding surface of the upper per-
manent molars is like that of M. nehringi as a whole. However, in some
cases the anterior fold of М! is complicated by the presence of an addi-
tional outward layer (Figures 28 and 66). The roots of the upper per-
manent molars are constructed on the same principle as in the previous
species. However, the tendency toward bifurcation of the inner root on
M!—M2? is, perhaps, more clearly expressed (Figure 67). Three roots are
often observed on МЗ. The measurements and proportions of the upper
permanent molars are as follows: M1—length, 2.2-2.6-3.3 mm; width,
1.9—2.3—3.0 mm; relation of width to length, 71.4-88.2-104.0; M*—length,
1.9—2.2—2.8 mm; width, 2.0-2.3-2.9 mm; relation of width to length, 88.0-
105.9-123.5; M°—length, 1.3-1.7-2.1 mm; width, 1.5-1.8-2.3 mm; re-
lation of width to length, 88.2—108.7-125.0.

The horizontal branch of the lower jaw is, on the average perhaps,
relatively higher and the diastema is relatively longer than in the preceding
species (relation of height of horizontal branch at the level of the first
permanent molar, and length of diastema to length of row of permanent
molars are equal respectively to 84.0-101.7-127.1 and 70.0-91.0-125.4).
The nature of the structure, the degree of development in the symphoidal
tubercle, the jaw angle, and also the position of the supramaxillary foramen
in the Balkan type are similar to the same in M. nehringi. In the nominal
subspecies, the symphoidal tubercle is sharply defined, the maxillary angle
is well developed, and the supramaxillary foramen is not shifted to the
lower edge of the jaw.

The structural characteristics of the lower incisors have been noted in

15

226

the diagnosis. The lower permanent molar (Figures 29, 67 and 68) are
similar, on the whole, to the molars of the preceding species with regard
to the structure of the grinding surfaces and the roots. However, on the

Figure 66. Microspalax leucodon leucodon Nord. Х 10.

Upper row of permanent molars: A to E—young and semi-mature;
F to J—adult; K to M—old individuals.

REN
М

С

227

Figure 67. Structure of roots and alveoli of permanent molars Microspalax leucodon Nord. (by Mehely, 1909).

228

average, М; is relatively wider than in М. nehringi (relation of width to
length, 83.3-95.1-122.2). The measurements and proportions of the lower
permanent molars are as follows: M,—length, 1.8—2.3-3.1 mm; width,
1.8—2.2—2.6 mm; relation of width to length, 83.3-95.1-122.2; M,—
length, 1.8—2.2-3.0 mm; width, 2.1-2.4-2.8 mm; relation of width to
length, 87.0-108.1-130.0; M,—length, 1.6-2.0-2.5 mm; width, 1.6-1.9-—
2.4 mm; relation of width to length, 81.0-96.1-129.4.

Comparison. A detailed comparison of M. leucodon and M. nehringi
has been carried out above (pages 218 -219).

Figure 68. Microspalax leucodon leucodon Nord. x 10.

Lower row of permanent molars: A to E—young and semi-mature;
F to I—adult; J, K—old individuals.

Measurements. Condylobasal length of skull, 35.7-43.8—51.4 mm; basic
length of skull, 32.9-40.8-50.8 mm; length of nasal bones, 14.9-18.7—
24.4 mm; total length of parietal and temporal bones, 15.3—19.0-23.0 mm;
length of parietal bones, 5.8-8.2-10.6 mm; length of upper diastema,
12.5-16.1-20.5 mm; length of hard palate, 21.5-26.5-33.2 mm; length of
upper row of permanent molars, 6.5-7.8-9.0 mm; width of nasal openings,

229

4.3—5.5-7.0 mm; incisorial width, 5.9-7.8-9.5 mm; width of nasal bones
anteriorly, 5.2—7.3-8.1 mm; rostral width, 8.1-10.0-12.0 mm; width behind
the eyes, 6.3-7.5-8.9 mm; width of two parietals, 8.5-12.0-15.0 mm;
width of parietal bones up to lambdoid ridge, 5.2-6.6-8.6 mm; malar
width, 27.1-34.6-41.4 mm; maximum width of occiput, 23.0-28.0-
34.7 mm; length of auditory bullae, 10.2-11.6-13.7 mm; width of audi-
tory bullae, 6.7-7.5-8.2 mm; width of upper incisor, 1.9-2.6-3.3 mm;
antero-posterior cross section of upper incisors, 1.8—2.5-3.3 mm; height
of occipital bone, 16.9-19.9-23.2 mm; height of nasal openings, 2.9-3.6-
4.8 mm; condylar length of lower jaw, 23.8—28.7-35.5 mm; angular length
of lower jaw, 22.4-27.7-35.8 mm; length of lower diastema, 5.0-6.8—
8.8mm; length of lower row of permanent molars, 6.7—7.4-8.7 mm;
height of horizontal branch at the level of center of the alveoli of М,, 6.0-
7.5-8.9 mm; thickness of horizontal branch at the level of Mz, 3.1-4.1-
5.1mm; height of alveolar process from inside, 3.2—6.0-8.0 mm; width
of lower incisor, 1.8—2.6-3.3 mm; antero-posterior cross section of lower
incisor, 2.0-2.7-3.8 mm.

Note. M. leucodon is a highly specialized representative of the genus
Microspalax for an underground way of life. Within the genus, it is char-
acterized by the widest upper and lower incisors and the corresponding
sections of the facial section, by the most elongated upper and lower
diastemata, by a wide and low occipital section of the skull, by strongly
developed sagittal and lambdoid ridges, and by a relatively high horizontal
branch of the lower jaw.

The species was first described by Nordmann (1840) from an example
found around Odessa. However, this work was ignored by research
workers without due consideration. As a result, the species was rewritten
several times, based on very scanty material from Yugoslavia and Hungary
(Nehring, 1897, 1898a) and from Bulgaria (Miller, 1903, 1912), and more-
over, the respective descriptions were done without a proper comparison
with the east European forms described by Nordmann. Nehring (1898a,
1898b) and after him, Mehely (1909), considered that around the Balkan
countries and around the adjacent regions of Hungary and Rumania,
there lived two species of the genus Microspalax—M. monticola (Nehr.)
(Yugoslavia, Greece, Bulgaria, and European Turkey) and M. hungaricus
(Nehr.) (Hungary, Rumania). The peculiarities of М. were taken as differ-
entiating traits by the authors. It was considered that M. hungaricus had

only one inner intruding fold on the lower third permanent molar and
not two (the external and internal), differing from M. monticola in this
respect. However, as new data poured in, this trait was not confirmed.

Miller (1912) quite emphatically said M. monticola was synonymous
with M. hungaricus; however, he mistakenly thought a type lived around
Bulgaria which is principally different from M. hungaricus. Because of

230

this, he maintained the name of М. dolbrogeae (Miller) given by himself
in 1903 for the Bulgarian and Rumanian Microspalax. To prepare a basis
for this, Miller (1912) made an unsuccessful attempt to discover the
difference between the types mentioned above with regard to relative
height of skull (in relation to condylobasal length), width of auditory
bullae and suborbital foramen. However, the traits given by Miller (1903,
1912) in the diagnosis of the type and in the table determining it were
found after further review to be nothing other than an ae of
individual and age variability.

Mehely (1909) considered M. dolbrogeae as a subspecies of М: monti-
cola Nehr. The name given by Nordmann was restored only later in the
works of Reshetnik (1939, 1941) and Ognev (1947).

Distribution and geological age. Yugoslavia, north Greece, European
Turkey, Bulgaria, Hungary, Rumania, Moldavian SSR and surrounding
regions of Ukraine, Odessa region in the north approximately up to the
Baltic, on the coast up to the Yuzhnogo Buga River, Soviet Bukovina.
Authentic fossil remains up to the Holocene age are not known though,
possibly, the Pleistocene mole rats from the sediments of south Austria
(Brunner, 1936) and Hungary (Kormos, 1917) have to be added to this
species.

Subspecies. Mehely (1909) and Hinton described nine subspecies of
M. leucodon from very scanty data from different sources of the Balkan
and Pre-Baltic regions. This was not confirmed in the comparative study
on Martino’s collections stored in the Zoological Institute of Academy
of Sciences of the USSR. These collections refer to specimens from Yugo-
slavia, Hungary and Bulgaria, material from Moldavia and nearby
territory of the Ukraine, and related literature. On this basis perhaps,
there are not more than two subspecies which differ in their average
magnitudes of measurements in regard to a number of traits of skull
and lower jaw.

М. I. leucodon Nordmann, 1840 (including М. /. transsylvanicus Meh..,
1909). It is characterized by comparatively smaller absolute measurements
(body length, 158-185-230 mm; length of foot, 17-20-24 mm; condylo-
basal length of the skull, 36.7-42.5-50.4 mm; length of upper row of
permanent molars, 6.5—7.4-8.0 mm; condylar length of lower jaw, 23.8—
27.6-32.9 mm; length of lower row of permanent molars, 6.7—7.1-7.9 mm);
by an elongated upper and lower diastemata; widened upper and lower
incisors; relatively wider skull in the incisorial-rostral sections and in the
section behind the eyes; by a lower, widened nasal opening; by faintly
separated processes of the winged bones; by a sharply defined symphoidal
tubercle; by a well-developed maxillary angle of the lower jaw; and by a
supramaxillary foramen which is not shifted to the lower edge of the jaw.

It is distributed in Hungary on the west up to Tissa in Rumania,

231

Moldavia SSR and surrounding regions of Cherenovitskaya region of the
Ukraine SSR, in the Odessa region of the Ukraine SSR on the north
approximately up to Balta, and on the east up to the Yuzhnogo Buga
River.

М. I. monticola Nehr., 1898 (including types М. [. hellenicus Meh..,
1909; М. 1. dolbrogeae Miller, 1903; М. 1. hercegovinensis Meh., 1909;
М. I. syrmiensis Meh., 1909; М. I. serbicus Meh., 1909; М. 1. hungaricus
Nehr., 1898; М. /. thermaicus Hinton). It differs from the nominal sub-
species by:

1. Onan average, large, absolute measurements (body length, 170-201-
245 mm; length of foot, 21.5—24.5-27.5 mm; condylobasal length of skull,
37.4—45.1-53.7 mm; length of upper row of permanent molars, 7.1-8.1-
9.0mm; condylar length of lower jaw, 25.0-29.9-33.9 mm; length of
lower row of permanent molars, 6.9-7.7-8.7 mm).

2. A shortened upper diastema (magnitude of diastema-tooth ratio,
162.5—201.7-240.0, as against 164.4-214.0-280.3 in the nominal sub-
species).

3. Narrowed upper and lower incisors (relation of width to antero-
posterior cross section, 86.4-97.7—108.7 for the upper, and 80.0-89.5—100.0
for the lower, as against respectively 93.3-105.3-119.0 and 81.8-94.8—
115.0).

4. A lesser width of skull in the incisorial, rostral, and behind the eyes
sections (relation of incisorial, rostral and preorbital width to length of
row of permanent molars, 80.3-95.3-111.7, 106.8—123.7-149.3 and 71.6-
89.8—115.5, as against respectively 82.9-105.5-130.0, 112.3-136.0-162.0
and 85.0-102.8-124.3).

5. A high and narrow nasal aperture (relation of height of nasal aper-
ture to its width, 56.7-72.2-82.6, and to width of row of permanent molars
is 55.4-67.1-81.6, as against respectively, 45.1-59.7—79.0 and 60.0-76.7-
91.7 in the nominal subspecies).

6. Widely separated processes of wing-like bones (distance between
external edges, as a rule, exceeds the length of the two first permanent
molars; in the nominal subspecies, the first measurement in the majority
of given instances is less than in the second or, at best, equals it).

7. Shape of temporo-nasal and temporo-maxillary sutures (nasal bones
are shorter than premaxillary because of which the sutures indicated form
an angle with its apex directed anteriorly; in the nominal subspecies, the
temporo-nasal and temporo-maxillary sutures form an almost straight line
because the length of the nasal bones is approximately equal to the length
of the premaxillary bones).

8. On the average, a short lower diastema (magnitude of diastema tooth
index, 70.0-88.4-125.4 as against 74.0-93.6-117.3).

9. A flattened symphoidal tubercle, a faintly expressed maxillary angle

232

of the lower jaw and, similarly, а supramaxillary foramen which is some-
what shifted (situated at the lower edge of the horizontal branch closer
than to the alveolar; in the nominal subspecies, it is situated closer to
the alveolar edge).

It spreads up into Yugoslavia, north Greece, European Turkey, Bul-
garia (up to Dunai on the north), Hungary (east up to Tissa).

2. Genus SPALAX Giildenstaedt. 1770—TRUE MOLE RAT

Giildenstaedt, 1770: 409-440. Mus (partim!) Schreber, 1792: 718-720. Talpoides
Lacépéde, 1799: 10. Aspalax Desmarest, 1804: 24. Anotis Rafinesque, 1815, Analyse de
la nature, on tableau de l’univers et de corps organises: 58. Ommatostergus Keyserling
u. Blasius, 1840 (nomen nudum). Myospalax Hermann, 1873: 83. Macrospalax Mehely,
1909: 32-37.

Genotype. Spalax microphthalmus Gildenstaedt, 1770; recent; left bank
of Ukraine, mixed regions of black soil, strips of RSFSR, right bank
of Volga region except the lower, and the northwestern Caucasus.

Diagnosis. The for. supracondyloideum is always absent. Vestiges of
this foramen are observed only in two per cent of the individuals from the
most primitive representatives of the genus Spalax—the modern Bukovin
mole rat S. graecus Nehr. The tuberculum pharyngeum laterale are narrow,
drawn out in the shape of narrow ridges along the edges of the main wedge-
shaped bone and the base of the occipital bone, because of which the
base of the skull in the region of the tuberculum pharyngeum laterale is
convexly bent like a furrow (canal) in a longitudinal direction. The basis-
phenoid and the base of the occipital bone are in one plane; the crack in
the base of the skull at the place of this contact (which is characteristic of
Microspalax) is not expressed. The auditory aperture is small; the length
of the auditory bulla exceeds more than four times the largest diameter of
the auditory opening (4.1-5.6-8.0). The lacrimal fossa is placed low. Its
lower edge is situated above the upper edge of the molar process of the
mandible. The skull is high; the height at the level of the anterior edge
of the last permanent molar is twice less than the length from the nasal
up to the apex of the lambdoid ridge. The parietal bones form a pentagon
or five-angled star (Figure 74). The sagittal ridge is short; itis twice or more
shorter than the nasal bones (1.8—2.1-2.7) and is convex. The ridge of the
coronary-alveolar site of the lower jaw is well developed and sharp. The
depression between the ridges is deep and always closed. The angular
process which almost always touches the alveolar process is rounded at
the ends and shifted somewhat forward in relation to the latter; its apex,
as a rule, is situated anterior to the posterior wall of the proc. alveolaris.
The area on the external surface of the angular process is marked all
along its border covering the places of attachment of the anterior and
posterior parts of the musculus masseter lateralis. The sella externa is

233

approximately situated at the same level as the sella interna ог is placed
even above it. The alveolar process is high; its height beginning from
maturity exceeds the length of the lower row of permanent molars. If the
height of the alveolar process should be less than the length of the lower
tooth row or approximately corresponds to it, then the length of the body
is more than 250 mm, and the condylobasal length of the skull exceeds
55 mm. The dorsal arch of the first cervical vertebra is wide; its antero-
posterior length is equal to the height of the neural canal. Remains of
the general spine are absent or are represented in the shape of a small
protuberance. The neural spine of the second cervical vertebra is long
and high; its length exceeds more than twice the least width. The neural
spines of the thoracic vertebrae are long and narrow. The sacrum is greatly
constricted in the posterior portion; its anterior width exceeds approx-
imately twice or more the same in the region of the fifth sacral vertebra.
The neural spines are not fused completely; the sagittal ridge is divided
(Figure 49), though in some cases complete fusion of the respective pro-
cesses is observed in the second, third, and rarely fourth sacral vertebrae.
The horizontal wings are always divided in the region of the fifth sacral
vertebra and sometimes in the region of the fourth. In males and females
the sacrum never touches the ischial axis of the pelvic bone, as a result
of which the large ischial arch is always widely open from behind. The
medial surface of the scapula is strongly bent anteriorly. Its caudal edge
is widened because of the great development of the caudal crest (crista
caudalis); the greatest height of the caudal edge is less than the maximum
width of the scapula by about three times (2.3-2.8-3.1). The acromion
process in mature and old representatives is completely dissimilar because
the acromion tubercle (tuber spinae) is flattened (Figure 47). The acromion
process is wide and club-shaped; its width is shorter by twice or less its
length. The cranial edge of the scapula is smooth or has a blunt tooth-like
process because its posterior portion is not well defined. The diaphysis
of the shoulder bone is considerably flattened in an antero-posterior
direction; its width above the proc. deltoideus exceeds the antero-posterior
cross section at the same level by more than one and a half times (1.6—
1.8—2.0). The deltoid process itself is, on the average, relatively shorter
and higher than in representatives of the genus Microspalax; its lateral
edge, as a rule, considerably protrudes as compared to the edge of the
lateral condyle, is strongly curved, and the general area of its base is less
than the distal width or is approximately equal to the latter. The medial
condyle is long and wide; its length and the antero-posterior cross section
are approximately equal to the posterior width of the distal block. The
tubercle of the radius is widened from above; the maximum width of its
proximal epiphysis is two and a half times less than the length of the
olecranon (2.0-2.2—2.5). The maximum width of the semi-circular notch

234

at the level of the ulna joint always exceeds the same at the level of the
lower edge of the hook-like process because the coronary process of the
radius is well developed. Furthermore, the olecranon is, on the average,
longer than in Microspalax. The lateral depression—the place of attach-
ment of the long abductor of the pollux and the long flexor of the same
—is shallow; it is wide in appearance; its upper edge in the majority of
given cases is placed approximately at the same level as the lower edge of
the hook-like process and even if it elevates, it does so at a distance which
is considerably less than the height of the semilunar groove, The ulna is,
on the average, thicker than in representatives of the genus Microspalax;
its least width (at the base of the proximal epiphysis) is approximately
twice less than the width of the latter (1.8—2.0-2.3). The distal epiphysis is
greatly widened; its maximum width exceeds the similar width of the
proximal epiphysis. The ilium is short; its length in all the given cases
was approximately equal to the length of the ischium (even when it exceeds
the latter, it does so at not more than half the length of the acetabulum).
The abdurator in the majority of cases is almost completely overgrown;
its length is considerably less than the length of the articulating fossa
(Figure 49). However, in S. microphthalmus, the measurements of this open-
ing approximate those in representatives of the genus Microspalax. Mea-
surements of the ischial axis are twice or more less than the measurements
of the tuber ischii. During this, the ischial axis never fuses and does not
come in contact with the wings of the sacrum. The femur has a wide dia-
physis greatly flattened in an antero-posterior direction; the width of the
bone at its narrowest part exceeds more than one and а half times the
antero-posterior cross section measured at the same level (1.4—1.6-1.8).
The tubercles under the joint are well developed; the width of the bone
at the tubercles is wider and the joint always exceeds the intercondylar
width. The patella is short and wide; its length exceeds its width not more
than two times. The tubercle of the femur in the majority of cases is
absent or present as a vestige. The medial ridge is well developed and sharp.
The bend of the bone is present but slight (considerably less than in Micro- ‘
spalax). The proximal epiphysis of the fibula is narrow; its width is less
than the width of the proximal epiphysis of the tibia by more than one
and a half times (1.6-1.9-2.3). The symphysis of the tibia and fibula is,
on the average, longer than in Microspalax; its length is usually less than
two and a half times the full length of the tibia (2.0—2.2-2.4). The free
part of the fibula is slightly more curved from the external side than in
representatives of the genus Microspalax.

Comparison. A comparison of the genus Spalax and Microspalax has
been given above.

Composition of the genus. Five modern and one fossil Late Pliocenic
species—S. giganteus Nehr., 1897; S. arenarius Reshetnik, 1939; S. micro-

235

phthalmus Giild., 1770; 5. polonicus Mehely, 1909; 5. graecus Nehr., 1898;
and S. minor W. Topachevskii, 1959.

Distribution and geological age. Late Pliocene (middle and end of the
period) to present day. Recent representatives are distributed in the
Prikarpate regions of Rumania and Ukraine SSR (Bukovina), in all the
territory of the Ukraine but for its northernmost parts, in the mixed
regions of the black soil belt of the Russian Federation in the middle of
the region around the Volga (right bank), in the Pre-Caucasus, North
Caspian to the east from the Ural River and behind the Caspian. Fossil
remains of the Pliocenic period are known only from around the Black
Sea and Azov regions of the Ukraine. Anthropological remains are found
everywhere within the boundaries of the distribution area of the genus,
and even to the northern borders of its present-day area (Arzamaskii
region, Gorkii district; Gromov and others, 1963).

KEY FOR IDENTIFICATION OF SPECIES
OF THE GENUS SPALAX

1 (4). The rostral section of the skull is greatly widened and scapula-
shaped. Its width at the level of the anterior edges of the suborbital
opening and at the center is approximately the same (Figures 3 and
71) The total width of the nasal bones posteriorly is considerably
less than the width of the premaxillary bones (individually), and
the latter in turn considerably exceeds half of the anterior total
width of the nasale. The temporo-parietal and forehead-to-temple
sutures form a sharp angle (giganteus group).

2 (3). The length of the upper masseter exceeds approximately twice or
more the least distance between the premaxillary and maxillary
bones. The width of the hard palate, at the level of М! in adult and
old individuals, is approximately equal to the length of the anterior
permanent molar. The natural articulating fossa is wide with a
flattened inner ridge. The alveolar process of the lower jaw in adult
and old individuals is approximately equal in height to the articular
one (Figure 3). The length of the body is 250 to 350 mm; condylo-
basal length of skull, 43.9-55.4-69.6 mm. The color is light pale-
gray-yellow (straw); on the ventral side it is slightly more gray than
оне bac key weenie. ааа Sails 1. S. giganteus Nehring.

(Holocene, including recent).

3 (2). The length of the upper masseter area is approximately equal to
the distance between the anterior ridge of the latter and the suture
between the premaxillary and maxillary bones. The width of the
hard palate at the level of М! exceeds one and a half times or more

236

4 (1).

5 (6).

6 (5).

7 (8).

the length of this tooth. The natural articulating fossa is narrow
with a sharply outlined inner ridge. The alveolar process of the
lower jaw in adults and old individuals considerably exceeds the
articulating one in regard to height (Figure 71). The length of the
body is 190-234-275 mm; condylobasal length of skull, 42.4-51.0-
59.0 mm. Comparatively darker shades of color predominate (dull
gray); the ventral side is usually considerably more gray than the
Бабка Pat eee ares cae 2. S. arenarius Reshetnik.
(Recent).
The rostral section of the skull slowly narrows in a forward direction
and is wedge-shaped. Its width at the level of the anterior edges of
the suborbital foramen always exceeds the width at the middle
(Figures 74, 77 and 81). The total width of the nasal bones poster-
iorly is considerably more than the width of the nasale or is ap-
proximately equal to it. The temporo-parietal and forehead-to-
temple sutures form a blunt or straight angle (Microphthalmus
group).
The anterior width of the nasal bones exceeds less than twice the
width posteriorly. The groove between the nasal bones in the region
of the temporo-nasal suture is well developed; its posterior ends
are sharp and are bifurcated like a fork (Figure 81). The least width
of the external wall of the suborbital foramen exceeds the length
of the anterior permanent molar. The depression on the temporal
bones in the place of the sagittal ridge is deep and sharply defined.
The apex of the coronary process of the lower jaw is very much
Serrated siete SSS Ne Pb ede 5. S. graecus Nehring.
(Holocene, including recent).
The anterior width of the nasal bones exceeds more than twice the
posterior width. The groove between the nasal bones in the region
of the temporo-nasal suture is absent or is slightly demarcated; the
posterior ends of the nasale are blunt in the majority of cases and
do not form a fork-like bifurcation (Figures 74 and 77). The greatest
width of the external wall of the suborbital foramen is less than the
length of the anterior permanent molar or is close to the latter. The
depression on the temporal bone in the place of the displaced
sagittal ridge, is absent or is faintly marked. The apex of the coro-
nary process of the lower jaw is not serrated.
The nasal bones are shorter than the premaxillary. The temporo-
nasal and the temporo-premaxillary sutures form an angle with the
apex directed forward (Figure 77). The length of the nasale is less
than the total length of the temporal and parietal bones. The largest
diameter of the auditory opening exceeds the length of the anterior
permanent molar. The protocone and hypocone оп М! of young

and semi-mature animals are always separated (Figure 78)........
ROP IOS ES Saree Ret INS 4. 5. polonicus Mehely.
(Pleistocene to recent).

8 (9). The nasal bones are of the same length as the premaxillary bones
or even longer than the latter. The temporo-nasal and temporo-
premaxillary sutures are straight (Figure 74). The length of the
nasale is more than the total length of the temporal and parietal
bones, or is equal to the last. The largest diameter of the auditory
opening is approximately equal to the length of the anterior per-
manent molar. The protocone and hypocone оп М! in the majority
of cases are fused at the same stage of wearing (Figure 75).

9 (10). The total width of the parietal bones exceeds the length of the
upper row of permanent molars. The width of the articulating
surface of the condylus of the lower jaw exceeds half its length.
The corono-alveolar groove is very step-like; its ridge in regard
to height is close to the height of the corono-articulating groove.
oS aA, А oe oa Ra a GN Ar 3. S. microphthalmus Giildenstaedt.

(Pleistocene to recent).

10 (9). The total width of the parietal bones is less than the length of
the upper row of permanent molars. The width of the articulating
surface of the condylus of the lower jaw is less than half its length,
or is approximately equal to it. The corono-alveolar groove is
step-like; its ridge usually exceeds in height the height of the
corono-articulating groove......... 6. S. minor W. Topachevskii.

(Late Pliocene, Early Anthropogen).

1. Spalax giganteus Nehring, 1897—Giant Mole Rat
Nehring, 1897: 169-171, Abb. 2. Spalax uralensis Tiflov and Usov, 1938: 141-143.

Holotype. Institute of Special Zoology and Zoological Museum of the
University of Humboldt, Berlin; the number of the example has not been
fixed (Nehring, 1897: Abb. 2); around Makhachkaly, Dagestan.

Material investigated. Forty-five skulls and skins obtained in the vicinity
of Pre-Caucasus and northern Pre-Caspian. They have been stored in the
collections of Moscow State University, Zoological Institute of AN SSSR,
Institute of Zoology AN Kazak SSR, and Kiev State University.

Diagnosis. This is the largest of the presently known representatives
of the subfamily Spalacinae (length of body, 250 to 350 mm; length of
hind foot 31.9 to 36.8 mm; condylobasal length of skull, 43.9-55.4—
69.6 mm; length of the upper row of permanent molars, 9.1—10.5—
11.7 mm., length of lower row of permanent molars, 9.3-10.2-11.0 mm).
The rostral section of the skull is greatly widened and is shovel-shaped.
The width of the nasal bones posteriorly is less than the width of each of

238

the premaxillary bones; the latter, in turn, exceeds half the width of the
nasale anteriorly. The temporo-nasal and the temporo-maxillary sutures
form an angle with its apex directly forward. The antero-external edges of
the molar arches are sharply bent down (Figure 3). The masseter area is
long; its length exceeds approximately more than twice the least distance
between the anterior ridge of the latter and between the inter-mandibular
and mandibular sutures. The alveolar tubercles are separated from the
anterior edge of the alveolus of М! at a distance which is considerably less
than the length of the first permanent molar. The hard palate at the level
of the anterior permanent molars is narrow. Its width in mature and old
individuals is approximately equal to the length of M?. The alveolar
process of the lower jaw is approximately equal to its articular one in height.

Description. The rostral section of the skull is greatly widened because
of the latitudinal bulge of the upper sections of the premaxillary bones.
Its width at the level of the anterior edges of the suborbital foramen, and
at the middle, is approximately similar. The edges of the rostrum greatly
converge together anteriorly. The posterior portions are parallel and,
rarely, slightly separate in the majority of cases. The total width of the
nasal bones from behind is considerably less than the width of each pre-
maxillary, and the latter, in turn, considerably exceeds half the total
anterior width of the nasale. The nasal aperture is narrow and placed low.
The ratio of its width and height to the length of row of permanent molars
is respectively equal to 68.1-78.6-92.3 and 33.6-39.0-44.0 in mature and
old individuals; and 62.2—70.5-75.5 and 33.6-35.0-36.3 in the young and
semi-mature. The nasal bones are relatively narrow anteriorly; the magni-
tude of the relation of their anterior width to the length of row of per-
manent molars is 75.2-86.6-101.8 for mature and old individuals, and
65.3—76.1-87.9 for young and semi-mature animals. The length of the
nasal bones in the majority of cases is less than the total length of the
temporal and parietal bones. Furthermore, the nasale are shorter than the
premaxillary bones because of which the temporo-nasal and temporo-
maxillary sutures form an angle with its apex directed forward. It has also
to be noted that the nasal bones of the giant mole rat are, on the average,
relatively shorter than in all the modern species of the genus Spalax;
the relation of their length to the length of row of permanent molars is
equal to 201.9-226.6—263.4 in mature and old individuals, and 171.4—196.6—
231.6 in young and semi-mature animals. The constriction behind the eyes
is equally and strongly expressed in mature and old males and females;
the relation of the width behind the eyes to the length of row of permanent
molars is 58.5—75.6-95.6. The temporo-parietal section is short; the relation
of total length of the temporal and parietal bones to the length of ММЗ
is 217.1-245.2-267.3 for mature and old individuals, and 208.7-222.4—
235.7 for the young and semi-mature. The parietal bones are relatively

239

longer and wider; the relation of length and width of each to the length
of the row of permanent molars is respectively equal to 87.6-130.0-148.1
and 32.1-50.5—63.2 in mature and old individuals, and 124.2—142.0-204.3
and 65.0-78.0-89.1 in young and semi-mature animals. The depression on
the temporal bone in the place of the displaced sagittal ridge is not ex-
pressed. The temporo-parietal and the temple-to-forehead sutures form a
sharp angle (Figure 3). The upper diastema and the hard palate are re-
latively shorter than in all the presently known recent representatives of
the genus Spalax. Thus, the magnitude of the diastema-tooth index is
194.4—216.0-247.3 in mature and old individuals, and 148.0-165.6-183.8
in young and semi-mature animals; the relation of the length of the hard
palate to the length of row of permanent molars is respectively equal to
320.0-347.3-384.8 and 267.3—282.6-314.1. The masseter 1$ long; its length
approximately exceeds more than twice the least distance between the
anterior ridge of the latter and between the suture of the premaxillary and
maxillary bones. The alveolar tubercles are well developed and placed in
the direct vicinity of the anterior edges of the alveolus of М! at a distance
which is considerably less than the length of the anterior permanent molar.
The hard palate at the level of the anterior permanent molars is narrow;
its width in mature and old individuals is approximately equal to the
length of М1 in the majority of cases.

The zygomatic arches are very massive anteriorly. Their antero-external
edges are sharply bent down forming a malar angle approximately equal
to or exceeding 45°. The zygomatic arches are situated at the same level
posteriorly to the articulating surfaces for the joint of the lower jaw. The
external wall of the suborbital foramen is narrow from above (its least
width is less than the length of the anterior permanent molar), and signi-
ficantly widens below. The suborbital foramen is placed low; its height
is approximately equal to the length of the lower row of the permanent
molars and, in some cases, somewhat exceeds it. The inner edge of the
fossa glenoidea is smooth, and the articulating surface itself is wide. The
base of the occipital bone is narrow, as a result of which the auditory
bullae are closer to each other. Thus, the greatest distance between the
external edges of the tuberculum pharyngeum laterale approximately coin-
cides with the length of M?-M®. The auditory bullae are relatively narrow;
the relation of their width to the length of row of permanent molars is
equal to 80.0-94.5—111.1. The occipital part of the skull is relatively low;
the magnitude of the relation of the height of the occipital bone, measured
from the upper edge of the for. magnum up to the apex of the lambdoid
ridge, to the largest width of the occiput (measured near the base of the
molar arches) is 33.4—41.2—48.9.

The upper incisors are relatively narrow (for representatives of the
genus Spalax); the relation of width to antero-posterior cross section is

240

90.9-106.3-114.0. Their anterior surface is more complex than in all the
presently known fossil and presently living species of the genus.

М: (length, 3.0-3.4-3.8 mm; width, 2.7-3.1-3.5 mm; relation of width
to length, 77.8-91.8-97.2) in the young and semi-mature is similar to the
М: of the previously described genus Microspalax; the paracone is still
not fused with the anterior collar in the given stages of development, as a
result of which the tooth has, characteristically, two intruding folds in
the outer line (Figure 69). In mature animals, the middle external tubercle
fuses with the anterior collar while closing the antero-external intruding
fold, and thus forms a mark. In addition, vestiges of the metacone are
better preserved on the teeth of young and semi-mature animals than in
other species of the genus; the metacone is fused with the posterior collar
and the posterior mark represents itself as a structurally constricted portion
of the postero-external intruding fold. Such types of formations are alto-

Figure 69. Spalax giganteus Nehr. x 10.

Upper row of permanent molars: A to D—young and
semi-mature; E to G—adult individuals.

241

gether absent on the teeth of mature and old individuals. The order of
closure of the intruding folds into marks because of tooth erosion is as
follows: the antero-external, the inner portion of the postero-external,
the postero-external, and finally, the inner. In the majority of cases, the
tooth has two roots—the massive antero-internal which is formed because
of the fusion of the antero-external and the internal roots, and the postero-
external which is comparatively weakly developed. Quite often, all the
roots fuse together because of which the tooth has only one complex root.

М? (length, 2.4—2.8-3.3 mm; width, 2.6-3.1-3.6 mm; relation of width
to length, 100.0-109.7-120.7) is characterized by the presence of an
anterior mark of one outer and one inner intruding fold (Figure 69). The
anterior mark is formed in two ways. Most often it represents a constricted
portion of the outer intruding fold, and rather rarely, inside portions of
the inner intruding layer. The metacone and the posterior collar have a
tendency to separate only in the teeth of young individuals. In semi-mature
and mature animals, they are completely fused. The order of closing of the
intruding folds into marks is as follows: the anterior inner portion of the
outer, the inner portion of the inner, the outer, and finally, the inner. The
number of roots often varies from one to two. The order of fusion of the
roots is the same as in the preceding permanent molar.

МЗ (length, 1.8—2.2—2.7 mm; width, 2.4—2.7-3.3 mm) is relatively wider
than in all the other species of the genus (relation of width to length, 90.9—
120.3-144.4). In addition, this tooth is, on the average perhaps, relatively
shorter than in the close 5. arenarius (relation of length of МЗ to length
of the preceding molar, 72.0-80.2-96.4). The protocone and hypocone in
the majority of cases are not fused on lightly worn teeth. In the middle
stages of erosion, the third permanent molar of the giant mole rat is also
characterized by the presence of an anterior mark. It should be added to
the aforesaid that in the majority of cases, there is also an additional
external protuberance which fuses with the posterior intruding fold of the
outer line with age, and completely vanishes in old age. Most often, the
tooth is characterized by the presence of two roots—the massive posterior
internal (formed as a result of the fusion of the internal and posterior
external roots) and the weak antero-external. The degree of separation
of the latter vary significantly.

The lower jaw has a shortened diastema and a relatively low hori-
zontal branch. The values of the diastema-tooth index, and the relation of
height of horizontal branch to the length of the lower row of permanent
molars are respectively equal to 72.4—89.0-102.9; 103.0-113.5-127.9 in
mature and old individuals, and 73.3-78.7-92.0; 88.7-103.0-113.0 in
young and semi-mature animals. The alveolar process is low; it is equal
to or slightly exceeds the articulated one in height. The height of the
process measured from the internal side, even in mature and old indivi-

16

242

duals, is less than the length of the row of permanent molars. Thus, the
values of the respective indices in the giant mole rat are 70.0-85.1—100.1
in mature and old, and 42.4-61.4-83.0 in young and semi-mature indivi-
duals. The incisura corono-alveolaris terminates near the base of the
coronary process. Its ridge is, on the whole, more weakly developed than
in other species of the genus Spalax. The coronary process is low with a
smooth external surface in the majority of cases, because the lower edge
of the coronary-alveolar groove does not reach the coronary process (a
little encroachment is observed sometimes in very young individuals). The
incisura corono-condyloidea is wrongly cut because of the shortness of its
coronary edge as compared to the condylar edge. It has to be noted that
the ridge of the corono-alveolar groove is considerably less in the degree
of its development than the similar coronary articular groove, because of
which the depression between them is considerably smaller anteriorly than
in all the other fossil and recent representatives of the genus. The for.
mandibulae is placed low and separated from the ridge of the corono-
articular groove at a distance approximately equal to the length of the
articulating surface of the condylus; in any case, it much exceeds two-
thirds the length of the latter. The articulating surface of the condylus is
wide; the relation of width to length is 47.5—53.1-60.3.

The lower incisor is relatively narrower than in all the modern species
of the genus Spalax; the relation of its width to the antero-posterior cross
section is 95.2-98.0-108.1.

М, (length 3.0-3.2-3.7 mm; width, 2.8-3.1-3.5 mm; relation of width
to length, 86.5-96.2-106.4) in young, semi-mature, and partly in mature
individuals is characterized by an almost constant presence of an anterior
mark representing, most probably, a constricted anterior (additional)
external intruding fold which in other modern species of the genus,
except for S. microphthalmus, is completely reduced (Figure 70). The
protoconid and hypoconid are separate in early stages of wear. Further-
more, the tooth is characterized by the constant presence of an addi-
tional tubercle at the base of the external intruding fold between the
protoconid and hypoconid in young, semi-mature, and partly in mature
animals. There is one outer and one inner intruding fold in mature indivi-
duals. There are two roots. Of them, the posterior one is more strongly
developed than the anterior one and has vestigial marks of bifurcation.

М, (length, 2.6-2.8—3.1 mm; width, 3.0-3.3-3.7 mm; relation of width
to length, 103.2-118.2-132.1) is relatively wide. It is characterized by the
presence of one intruding fold in the outer and inner lines. The protoconid
and the hypoconid are fused, though in early stages of wear they some-
times exhibit a tendency toward separation (Figure 70). Traces of an
entoconid are absent (it is completely fused with the posterior collar).
The tooth has two roots; moreover, the posterior is developed consider-

243

ably stronger than the anterior one. Both roots exhibit а tendency toward
fusion; in addition, the anterior one has marks of bifurcation.

Figure 70. Spalax giganteus Nehr. х 10.

Lower row of permanent molars: A to C—young and
semi-mature; D to F—adult individuals.

М; (length, 2.4—2.7-3.1 mm; width, 2.6-3.0-3.6 mm; relation of width
to length, 93.1-112.9-128.0) is, on the average, relatively wider than in all
the presently known modern representatives of the genus. In the majority
of the given cases, it has an intruding fold in the outer line and one in the
inner. Separation of the protoconid and the hypoconid is observed rarely
in the very early stages of wear. There are two roots; the posterior one is
larger than the anterior. Both roots fuse along almost their entire length.
The anterior exhibits a tendency toward bifurcation which is proven by
the structure of the alveolus.

Comparison. This mole rat sharply differs from those of the micro-
phthalmus group in which we include the recent S. graecus, S. polonicus,
and S. microphthalmus and the fossil Late Pliocene S. minor, by a widened
rostral section of the skull which bulges along the edges of the rostrum as
well as by considerably large absolute measurements. The width of the
rostrum at the level of the anterior edges of the suborbital foramen and
in the middle is approximately equal because of the fact that its edges
are approximately parallel all along the posterior half of its length, and
slightly approach each other in the anterior part; the rostral section, on
the whole, has a more or less clearly defined shovel-shaped form. In mole
rats of the microphthalmus group, the rostral section does not bulge along
the edges, and the latter gradually meet in a forward direction because of
which the rostrum, on the whole, has an almost wedge-shaped contour
rather than a shovel-shaped form. The above-mentioned traits would look
as follows: the width of the nasal bones posteriorly in S. giganteus is less

244

than the width of the premaxillary (individually), and the latter consider-
ably exceeds the total width of the nasal anteriorly. In mole rats of the
microphthalmus group, the total width of the nasale posteriorly is greater
than the width of the praemaxilla, and the latter is less than half of the
anterior width of the nasal bones, or is approximately equal to it.

This species differs from its closely related species, the present-day S.
arenarius, as follows:

1. Considerably large absolute measurements.

2. A relatively long masseter area, the length of which exceeds more
than twice the least distance between the anterior ridge of the latter and
the suture of the premaxillary and maxillary bones. In S. arenarius, the
measurements are approximately the same.

3. Alveolar tubercles which are placed in the direct vicinity of the
anterior edges of the alveoli of the first permanent molars, at a distance
considerably less than the length of М. In 5. arenarius the alveolar
tubercles are separated from the anterior edges of the alveoli of М! at a
distance exceeding (in young and semi-mature individuals) the length of
the anterior permanent molar, or approximately equal to it.

4. The hard palate which is narrow at the level of M!, and the length
of which in both aged and mature individuals in the majority of cases is
approximately equal to the length of the anterior permanent molar. In
5. arenarius, its width exceeds the length of М! by more than one and a
half times.

5. A wide fossa glenoidea with a flattened inner ridge. In S. arenarius,
the inner ridge is sharply defined.

6. An occipital bone with a narrow base (the largest distance between
the external edges of the tuberculum pharyngeum laterale is approximately
equal to the length of M?-M®). In 5. arenarius, the base of the occipital
bone is wide (the indicated distance considerably exceeds the length of
the last two permanent molars).

7. A lower alveolar process of the lower jaw (even in mature and old
individuals, it is approximately equal to the articular one in regard to
height). In S. arenarius, this process is considerably higher than its
articular one. The indicated trait is quite clearly illustrated by the
magnitude of the ratio of the inner height of the process to the length of
the lower row of permanent molars. Thus, in S. giganteus, the alveolar
process in the majority of the given cases is shorter than the row of
M,-Ms; or rarely approximately equal to the latter (70.0-85.1-100.0),
whereas in S. arenarius it is always longer than the lower row of perma-
nent molars (102.5-116.6—132.5).

8. An unfused coronary-alveolar groove with a faintly developed ridge
(it is considerably weaker developed than the coronary articular one). In
5. arenarius this groove is very step-like because of a well-developed ridge

245

in the lower portion of the proc. alveolaris which is not less in the degree
of development of the coronary articular one, and because of which the
fossa between them is considerably deeper than in the giant mole rat.

9. A low placed mandibular foramen (shifted from the edge of the
coronary articular groove at a distance approximately equal to the length
of the articulating surface of the condylus). In S. arenarius, it is situated
at a distance considerably less than two-thirds the length of the condylus.

10. A widened articulating surface of the proc. condyloideus, the width
of which in the majority of cases is approximately equal to half the length
(47.5-53.4—60.3) or exceeds the same. In 5. arenarius, the articulating
surface of the condylus is constricted; its width is always less than half
its length (38.8—45.2—48.2).

11. A lesser tendency for separation of the protocone and hypocone
on M}, and a greater tendency for separation of the metacone and the
posterior collar than in similar permanent molars of S. arenarius.

12. An almost permanent presence of an additional inner tubercle on
М3. It is always absent in 5. arenarius.

13. The metaconid of M, which is fused with the protoconid in all
stages of wear. In S. arenarius, the metaconid is represented by an inde-
pendent fold on the similar permanent molar in young and semi-mature
individuals. In addition, the anterior mark and the additional tubercle
at the base of the intruding fold between the protoconid and hypoconid
are strongly developed on the anterior lower permanent molars of young,
semi-mature, and partly in adult giant mole rats. The former is rarely
found on similar molars in 5. arenarius and the latter is always absent in
this species.

Additional differences between the given species may be observed in
the average values of the following traits:

1. The nasal bones in giant mole rats are relatively short (relation of
their length to length of row of permanent molars, 201.0-226.6-263.4 in
adult and old individuals, and 171.4-196.6-231.6 in young and semi-
mature animals, as against respectively 241.0-250.6-257.9 and 210.5-
214.5—216.9 in the sandy mole rat).

2. The total length of the temporal and parietal bones is relatively less
(relation to length of M!-M?, 217.1-245.2—267.3 in adults and old indivi-
duals, and 208.7—222.4-235.7 in young and semi-mature animals, as
against respectively 241.6-261.1-285.0 and 216.7-230.2-244.2 in 5. are-
narius).

3. The parietal bones are relatively longer (87.6-130.0-148.1 and 124.2—
142.0-204.3, as against 105.2-125.2-137.5 and 131.1-124.5-130.1).

4. The upper diastema and hard palate are relatively shorter (value of
the diastema-tooth index and the relation of length of hard palate to
length of row of permanent molars, 194.4-216.0-247.3 and 148.0-165.6-

246

183.8; 320.0-347.3-384.6 and 267.3-282.6-314.1 as against respectively
230.0-249.9-266.7 and 178.3-184.2-195.2; 363.6-393.4—418.4 and 313.0-
321.3-332.1 in the sandy mole rat).

5. The nasal aperture and the nasale are relatively narrower (relation
of width of nasal aperture and both nasale anteriorly to length of row of
permanent molars is respectively 68.1-78.6-92.3 in adult and 62.2-70.5—
75.5 in old individuals, in young and semi-mature animals respectively
75.2-86.6-101.8; 65.3—76.1-87.9 as against 78.1-84.6-90.8; 71.8—75.3—79.5
and 87.5-94.7-100.0; 77.6-82.6-87.2 in S. arenarius).

6. The constriction behind the eyes in mature and adult specimens is
expressed more sharply (relation of width behind eyes to length of row of
permanent molars, 58.5—75.6-95.6 as against 71.6-81.3-89.3).

7. The parietal bones are comparatively wide (relation of width of
each parietal bone to length of M!—M3, 32.1-50.5-63.2 in adult and old
individuals, and 65.0-78.8—89.1 in young and semi-mature animals, as
against 33.0-44.2-51.2 and 62.7-68.1-71.7 in the sandy mole rat).

8. The occipital section is relatively low (relation of height of occipital
bone measured from the upper edge of the for. magnum to the largest
width of the whole occipital section, 33.4—41.2—48.9 as against 47.9-52.8-
59.3).

9. The upper incisors are relatively narrow (relation of width to antero-
posterior cross section, 90.9-106.3-114.0 as against 108.3—119.0-130.0 in
S. arenarius).

10. МЗ is relatively wider (relation of width to length, 90.0-120.3-
144.4 as against 95.6-109.5—120.0).

11. The lower diastema is relatively shorter (magnitude of diastema-
tooth index, 72.4-89.0-102.9 in adult and old individuals, and 73.3—78.7-=
92.0 in young and semi-mature animals, as against respectively 100.0-
117.4-126.6 and 84.3; 101.3 in the sandy mole rat).

12. The horizontal branch of the lower jaw at the level of the posterior
edge of the alveolus of M, is placed relatively low (relation of height to
length of lower row of permanent molars, 103.0-113.5-127.9 in adult and
old animals, and 88.7-103.0-113.0 in young and semi-mature individuals,
as against respectively 118.1-123.0-132.0 and 111.3 in 5. arenarius).

13. The lower incisor is relatively narrower (relation of width to
antero-posterior cross section, 95.2-98.0-108.1 as against 100.0-103.9—
109.0).

14. М. is relatively wider (relation of width to length, 93.1-112.9-128.0
as against 88.0-98.9-—104.3).

Furthermore, the third permanent molar is, apparently, relatively short
(relation of its length to length of М? is 84.0-95.5-111.5 as against 95.8—
104.4-109.1).

Measurements. Condylobasal length of skull, 43.9-55.4-69.6 mm; basic

247

length of skull, 40.0-53.4-65.6 mm; length of nasal bones, 16.8—22.9—
31.4 mm; total length of parietal and temporal bones, 20.0—25.0-30.2 mm;
length of parietal bones, 9.2—14.1-18.8 mm; length of upper diastema,
14.4-20.9-28.0 mm; length of hard palate, 23.6-34.0-43.4 mm; length of
upper row of permanent molars, 9.1-10.5-11.7 mm; width of nasal
aperture, 6.1-8.0-10.8 mm; incisorial length, 8.8-11.5-14.1 mm; width
of nasal bones anteriorly, 6.4-8.7-11.7 mm; rostral width, 11.5-15.0-
19.4 mm; width behind the eyes, 6.4—8.7—10.9 mm; width of two parietale,
6.9-10.8-15.8 mm; width of the parietal bone up to lambdoid to tubercle,
5.9-7.0-8.5 mm; malar width, 34.5-44.8-54.4 mm; maximum width of
occiput, 31.0-38.1-45.4 mm; length of auditory bullae, 12.6-15.2—17.7 mm;
width of auditory bullae, 8.8-9.9-12.0 mm; width of upper incisor, 2.8—
3.9-4.9 mm; anterior posterior cross section of upper incisor, 2.7-3.6-
4.6 mm; height of nasal opening, 3.1-4.0-4.9 mm; condylar length of
lower jaw, 33.6-40.1-46.3 mm; regular length of lower jaw, 33.3—39.8—
47.9 mm; length of lower diastema, 7.4—8.8—10.7 mm; length of lower row
of permanent molars, 9.3—10.2—11.0 mm; height of horizontal branch at
the level of posterior edge of alveoli of М, externally, 9.4-11.3-13.6 mm;
thickness of horizontal branch at the level of Мь, 5.2-6.5-8.2 mm; height
of alveolar process internally, 4.5-8.0-10.0 mm; width of lower incisor,
3.1-4.0-4.7 mm; antero-posterior cross section of lower incisor, 3.1-4.2—
5.1 mm.

Note. As has been said above, the giant mole rat compared to the rest
of the presently known living species of the genus has a shorter upper
and lower diastema, a skull placed relatively low in the occipital region,
narrow upper and lower incisors, a relatively low horizontal branch and
alveolar process of the lower jaw; with an ill-developed ridge on the
coronary-alveolar groove. Furthermore, apart from the above-mentioned
traits, the species has other traits indicating a lesser specialization of the
skull for burrowing activity.

In addition to this, the toothrows of S. giganteus are more complex
as compared to the same ones in other modern representatives of the
genus which together with traits indicating a rather stronger development
of the masticatory musculature (details of the structures of the masseter
area of the skull and partly of the zygomatic arches, etc., have been given
above) proved the great adaptability of the species toward consumption
of vegetative food which is rough in consistency. The latter fact is based,
perhaps, on the life style of the giant mole rat who, as is known, feeds in
more arid climatic zones compared to other recent species of the genus,

The foregoing account apparently shows that the species has preserved,
even up to present times, the old way of life akin to certain fossil species
which will be described below, in a way original for the group as a whole.

The species was described by Nehring (1897) from the Pre-Caucasus.

248

Afterward, У. Е. Tiflov and Ya. A. Usov (1938) tried to report its eastern
forms from Gurev and west Kazakhstan regions as an independent species
—S. uralensis Tiflov and Usov. The reasons for such a separation were
the rather smaller dimensions of the individuals from Kazakhstan, their
rather darker color, and at times, a sharply defined angle between the
temporo-nasal and the temporo-maxillary sutures, which was not con-
firmed by a series of data. All this permits one to completely agree with
the opinion of S. I. Ognev (1947) who considered S. uralensis as synony-
mous with S. giganteus. However, the possibility of the Ural mole rat
being an independent subspecies is theoretically feasible because the
nominal and the Ural form of mole rats live at quite a significant distance
from each other. We could not put our hands on enough data to solve
this problem with finality.

Distribution and geological age. The semi-arid Pre-Caspian regions of
northeastern Pre-Caucasus, mainly between the lower currents of the
Kumu, Tereka, and Sulaka Rivers. On the north, it exists somewhat
beyond the Kumu River, in the southern region of Kalmytskii ASSR to
the south approximately in the line of Mahachakala-Gudermes. Isolated
colonies are also known to occur to the east of the Urals in the eastern
parts of west Kazakhstan, at the extreme northeast Gur’evskii, and also
the Aktyubinskii regions along the Uilu, Temiru, and middle and upper
currents of the Emby River. Recent. Fossil remains have not yet been
found.

Subspecies. The geographical variability has not yet been studied
though 5. g. uralensis Ноу and Usov could be taken as an independent
subspecies.

2. Spalax arenarius Reshetnik, 1939—Sandy Mole Rat

Ognev, 1947: 615-620, Figures 296-301. Spalax polonicus arenarius Reshetnik, 1939:
11-12, Figure За. 5. zemni arenarius Reshetnik, 1941: 31-33; Figures 6a—-d, 7, 8. 5
microphthalmus arenarius. Vinogradov and Gromoy, 1952: 177.

Holotype. Institute of Zoology AN Ukraine SSR; No. 14, around
the Black Sea, Ukraine SSR; around the city Golaya Pristan, Kherson
region.

Material investigated. Forty-two skulls and twenty-five skins obtained
in the region of Aleshkinski sands (lower Dnieper). All stored in the
collections of the Institute of Zoology AN Ukraine SSR.

Diagnosis. Measurements are considerably smaller than in the giant
mole rat (body length, 190-234-275 mm; hind foot, 22-26-30 mm; condy-
lobasal length of skull, 42.4-51.0-59.0 mm; length of upper row of per-
manent molars, 8.3-8.7-9.9 mm; length of lower row of permanent
molars, 7.8-8.1-8.7 mm). The rostral section of the skull is very wide and

249

is shovel-shaped. The relative width of the nasal and premaxillary bones
is similar to that of the preceding species. The temporo-nasal and temporo-
maxillary sutures, as in the giant mole rat, form an angle with its apex
directed forward. The antero-external edges of the zygomatic are sharply
bent down. The masseter area is shortened; its length is approximately
equal to the distance between the anterior ridge of the latter and between
the suture of the intermandibular and maxillary bones. The alveolar
tubercles are placed farther from the anterior edge of the alveolus of М"
at a distance exceeding the length of the first permanent molar, or is
approximately equal to it (in young and semi-mature animals). The hard
palate at the level of the anterior permanent molars is wide; its width in
adults and old individuals exceeds the length of М1 by one and a half
times and more. The alveolar process of the lower jaw considerably
exceeds the articular one in regard to height (in adult and old individuals).

Description. The rostral section of the skull is, on the whole, like that
of S. giganteus. The nasal aperture is wide and high; the relation of its
width to length of permanent molars is respectively equal to 78.1-84.6-
90.8 and 38.6—43.2-50.0 in adult and old individuals, and 71.8—75.3-79.5
and 35.7-38.0-40.0 in young and semi-mature individuals. The nasal bones
are relatively narrower anteriorly; the value of the relation of their anterior
width to the length of permanent molars is equal to 87.5-94.7-100.0 for
adult and old individuals, and 77.6-82.6-87.2 for the young and semi-
mature. The length of the nasal bones, as in the giant mole rat, in the
majority of cases, is less than the total length of the temporal and parietal
bones. The structure of the temporo-nasal and temporo-maxillary sutures,
is, on the whole, as in S. giganteus. However, the nasal bones are, on the
average, longer than in the preceding species; the relation of their length
to the length of M1—M3 is 241.0-250.6-257.9 in adult and old individuals,
and 210.5-214.5-216.9 in young and semi-mature animals. The constric-
tion behind the eyes is, perhaps, expressed more faintly than in the giant
mole rat; the relation of the width behind the eyes to the length of row of
molars is 71.6-81.3-89.8 in adult and old individuals, and 96.5-99.5-—
102.3 in young and semi-mature animals. The temporo-parietal section
is elongated; the relation of the total length of temporal and parietal
bones to the length of M!-M®? is 241.6-261.1-285.0 in adult and old
individuals, and 216.7-230.2—244.2 in young and semi-mature animals.
The parietal bones are short and narrow; the relation of their length and
width (individually) to the length of row of permanent molars is 105.2—
125.2-137.5 and 33.0-44.2-51.2 in adult and old individuals, and 113.1-
124.5-130.1 and 62.7-68.1-71.1 in young and semi-mature animals. The
relation of the structure of the sagittal ridge, the temporo-parietal and
temporo-frontal sutures is similar to the preceding species. The upper
diastema and the hard palate is elongated; the magnitude of the diastema-

250

tooth index is 230.0-249.9-266.7 in adult and old animals, and 178.3—
184.2-195.2 in young and semi-mature animals; the relation of the length
of the hard palate to the length of the row of permanent molars is respec-
tively equal to 363.6-393.4-418.4 and 313.0-321.3-332.1. The structural
characteristics of the masseter area, the alveolar tubercles, and the hard
palate have been given in the diagnosis. It may be added to the aforesaid
that the alveolar tubercles in the sandy mole rat are, as a whole, more
weakly developed than in the giant mole rat. The structure of the anterior
sections of the zygomatic arches in general are as in S. giganteus. Their
antero-external edges are strongly bent down, forming a malar angle equal
to 45° or exceeding it (Figure 71). The external wall of the suborbital
foramen in adult and old animals is slightly broadened; its least width is
equal to the length of the anterior permanent molar or even considerably
exceeds it. The suborbital foramen itself is relatively higher than in the
preceding species; its height exceeds the length of the upper row of per-
manent molars. Only in some cases do these measurements coincide. The
inner ridge of the fossa glenoidea is sharply defined; the articulating
surface itself is narrow and elongated. The base of the occipital bone is
wide, because of which the auditory bullae are widely separated. Thus,
the largest distance between the external edges of the tuberculum pharyn-
geum laterale considerably exceeds the length of M!-M®. The structure
of the auditory bullae is, on the whole, similar to that of the giant mole
rat; the relation of width to length of line of permanent molars is 90.6—
96.1-103.4. The occipital section of the skull is relatively high; the magni-
tude of the relation of the height of the occipital bone, measured from the
upper edge of the for. magnum to the largest width of the occiput, is 45.4—
51.0-59.3.

The upper incisors are wide; the relation of width to the antero-
posterior cross section is 108.3-119.0-130.0. Their anterior surface is
flattened and smooth.

М: (length, 2.4—2.6-2.9 mm; width, 2.4-2.5-2.9 mm; relation of width
to length, 85.7-96.3-108.3) is, on the average perhaps, relatively wider
than in the previous species. The configuration of the enamel fold of the
grinding surface resembles the similar molar of the giant mole rat. How-
ever, the tendency of separation of the protocone and hypocone is sharply
expressed (Figure 72). The metacone is fused with the posterior collar in
all stages of erosion. The order of closure of the intruding folds into marks
is similar to that of the preceding species. In the majority of cases, there
are two roots—the massive postero-internal (formed by the fusion of the
postero-external and the inner roots) and the weak antero-external.

М? (length, 2.1-2.3-2.5 mm; width, 2.3-2.6-2.9 mm; relation of width
to length, 100.0-113.3-126.1) in regard to the nature of the structure of
the grinding surface is, as a whole, as in the giant mole rat. There are two

251

roots—the massive antero-internal (the fused antero-external and the
inner roots) and the faintly developed postero-external.
MS (length, 1.8-1.9-2.4 mm; width, 2.0-2.1-2.4 mm) is, оп the average,

SSS
еее eee 502-0

SO

\

\ а
‘aa
а

м ~ i

G

Figure 71. Spalax arenarius Resh. x 10.

Legend is the same as in Figure 50.

252

Figure 72. Spalax arenarius Resh. x 10.

Upper row of permanent molars: A to D—young and
semi-mature; Е to H—adult; /, J—old individuals.

relatively narrower and longer than in the preceding species; the relation
of width to length, and length to length of the preceding molar is respec-
tively equal to 95.6-109.5—-120.0 and 80.0-87.9-100.0. In young and semi-
mature animals, the protocone and hypocone were fused in the majority
of the given cases, because of which the tooth is characterized by the
presence of only one intruding fold in the outer line. The external addi-
tional tubercle is always absent. The anterior and posterior outer roots
are fused almost along their entire length with the inner root.

All the upper permanent molars are considerably smaller than similar
molars of the giant mole rat.

The lower jaw has an elongated diastema; the value of the diastema-
tooth index is 100.0-117.4—126.6 in adult and old individuals, and 84.3—
101.3 in the young and semi-mature. The horizontal branch is relatively
high; the relation of its height measured at the level of the posterior edge
of the alveolus of M, to the length of the lower row of permanent molars
is 118.1-123.0-132.0 in adult and old individuals, and on the average,

253

111.3 in young and semi-mature animals. The alveolar process is high in
adult and aged individuals and considerably exceeds the articular one
with regard to height. The height of this process, measured from the inner
side, always exceeds the length of the lower row of permanent molars
(the value of the respective index in the sandy mole rat is 102.5-116.6—
132.5). The incisura corono-alveolaris is step-like because of the strong
development of the anterior tubercle of the alveolar process which con-
siderably overlaps the coronary process. The latter, in the majority of
cases, is higher than in the preceding species, though in individual cases,
a type of structure akin on the whole to the condition in the giant mole
rat is observed. The outer surface of the proc. coronoideus is step-like
due to its being overlapped by the tubercle of the corono-alveolar groove.
The nature of the structure of the coronary articular groove varies depend-
ing on the height of the coronary process; it is asymmetrical when the
proc. coronoideus is elongated. The ridges of the corono-alveolar and
coronary-articular groove are developed approximately to a similar degree
anteriorly, as a result of which the depression between them is considerably
deeper than in the preceding species. The mandibular foramen is raised
to the border of the coronary-articulate groove, away from the tubercle
of the latter, at a distance considerably less than two-thirds the length of
the condylus. The articulating surface of the proc. condyloideus is narrow;
the relation of width to length is 38.8—45.2—48.2.

The lower incisor is wide; the relation of width to antero-posterior
cross section is 100.0-103.9-109.0.

М, (length, 2.4—2.7-2.8 mm; width, 2.4—2.5-2.7 mm; relation of width
to length, 88.9-93.1-100.0) in young and semi-mature individuals is char-
acterized by non-fusion with the anterior collar and, as a result, also with
the protoconid and the anterior inner tubercle, the metaconid (Figure 73).
In addition, the tooth has vestiges of an entoconid in the early stages of
wear. The protoconid and hypoconid are fused in all the stages of erosion;
however, a tendency for separation is, after all, observed in very young ani-
mals. The additional tubercle on the outer intruding fold is always absent.
Because the tooth has a free metaconid in the early and middle stages of
wear, the number of intruding folds in the inner line in young and semi-
mature animals is two. Because of the fusion of the metaconid with the
anterior collar, the anterior intruding fold is reduced. The order of closure
of the intruding folds into marks is given in Figure 73. The tooth has two
roots; of them, the posterior one is more strongly developed than the
anterior. The roots sometimes exhibit a tendency for fusion.

М. (length, 2.2—2.3-2.4 mm; width, 2.6-2.7-2.8 mm; relation of width
to length, 113.0-117.2-127.2) as in the previous species is wide. It is, on the
whole, similar to the same tooth in the giant mole rat with regard to the
configuration of the grinding surface and the structural nature of the roots.

254

M, (length, 2.3-2.4-2.6 mm; width, 2.1-2.3—2.6 mm; relation of width
to length, 88.0-98.9-104.3) is relatively narrow. On the whole, it is similar
to the М, of the giant mole rat; however, it differs in that the protoconid
and hypoconid on the teeth of young and semi-mature animals, in the
majority of cases, are separate. The tooth is characterized by having two
roots. In the majority of cases, they are fused along the entire length.

Figure 73. Spalax arenarius Resh. x 10.

Lower row of permanent molars: A to D—young and
semi-mature; E, F—adult; С to J—old individuals.

Comparison. A detailed comparison of S. arenarius and S. giganteus
has been made above. (Please turn to the corresponding section of char-
acteristics for S. giganteus.) The basic differences from mole rats of the
microphthalmus group are the same as for the giant mole rat.

Measurements. Condylobasal length of skull, 42.4—51.0-59.0 mm; basic
length of skull, 39.6-47.4-56.0 mm; length of nasal bones, 17.7-20.8—
23.9 mm; total length of parietal and temporal bones, 18.2—21.8—24.9 mm;

255

length of parietal bones, 9.5-10.8-12.7 mm; length of upper diastema,
15.2-19.8-24.4 mm; length of hard palate, 26.5-32.2-38.6 mm; length of
upper row of permanent molars, 8.3-8.7-9.6 mm; width of nasal aperture,
6.1-7.1-8.0 mm; incisorial width, 7.8-9.5-11.2 mm; width of nasal bones
anteriorly, 6.6-7.9-9.6 mm; rostral width, 10.4-12.6-14.7 mm; width
behind the eyes, 6.8—7.7-8.8 mm; width of two parietale, 4.9-8.0-12.6 mm;
width of parietal bone up to the lambdoid tubercle, 2.9-4.5-6.1 mm;
malar width, 31.3-39.9-45.6 mm; greatest width of occiput, 29.2-33.5-—
40.1 mm; length of auditory bullae, 10.8-12.8-15.0 mm; width of auditory
bullae, 7.7-8.4-9.1 mm; width of upper incisor, 2.6-3.3-4.0 mm; antero-
posterior cross section of upper incisor, 2.2—2.7-3.6 mm; height of nasal
aperture, 3.1-3.5-4.8 mm; condylar length of lower jaw, 31.8-36.2-
39.0 mm; angular length of lower jaw, 32.6-36.4—38.2 mm; length of
lower diastema, 7.0-9.0-10.1 mm; length of lower row of permanent
molars, 7.8-8.1-8.7 mm; height of horizontal branch at the level of the
posterior edge of the alveolus of M, externally, 8.6-9.7-10.4 mm; thickness
of the horizontal branch at the level of М,, 4.7-5.3-5.9 mm; height of
alveolar process internally, 7.4-9.2-10.6 mm; width of lower incisor, 3.0-
3.5-4.0 mm; antero-posterior cross sections of lower incisor, 3.0—3.4—
3.9 mm.

Note. The sandy mole rat is more specialized toward a burrowing type
of life than the previously described species. The presence of an elongated
upper and lower diastema, a skull relatively high in the occipital region,
widened upper and lower incisors, a relatively high horizontal branch
and alveolar process of the lower jaw, are the proofs; moreover, the latter
is characterized by a strongly developed tubercle of the corono-alveolar
groove in its anterior portion.

In addition, this species has still preserved the complex permanent
molars like those of S. giganteus which indicates not only the relative
primitiveness of it as a whole, but also its special adaptation of feeding
on rather hard, rough vegetative foods or, in other words, to living in
conditions of more arid climate than mole rats from the microphthalmus
group. This is partly proven also by the already described structural
characteristics of the upper masseter area (it assumes a medium position
in regard to the degree of development, between the giant mole rat and
the species of the microphthalmus group), and the zygomatic arch
(massive and sharply bent down in the antero-external section).

The status of this species was confirmed by S. I. Ognev (1947). Until
then, the sandy mole rat was primarily taken as a subspecies of S. polo-
nicus (Reshetnik, 1939, 1941). Ognev put S. arenarius close to S. micro-
phthalmus. As has been shown above, the species takes a middle position
between the giant mole rat and the species from the microphthalmus
group. The structure of the rostral section of the skull, the zygomatic

256

arches, and partly the permanent molars, put it close to the former;
whereas the elongated upper and lower diastema, widened upper and
lower incisors, the height of the occipital section of the skull, the wide
hard palate, the base of the occipital bone, anumber of structural peculiar-
ities in the lower jaw, and foremost, its alveolar process, put it close to
the latter. Further, without sufficient basis for all this, the species was
taken to be a subspecies of 5. microphthalmus (Vinogradov and Gromoy,
1952; Gromov et al., 1963).

Distribution and geological age. The lower Dnieper sandy area (Aleshkin-
skie Piski). The western boundary, the bank of the Dnieper and estuaries of
the Dnieper; the eastern boundary, approximately in line with Kakhovka-
Brilevka; the southern boundary, along the lines of Brilevka-Ivanovka.
The area of the species is apparently relict. Recent; fossil remains are not
known.

Subspecies. Because of the small area, it is represented only by a
nominal subspecies, S. a. arenarius Reshetnik.

3. Spalax microphthalmus Giildenstaedt, 1770—-Common Mole Rat

Giildenstaedt, 1770: 409-440, Tab. XV, Figures 1-10. Spalax Pallasii Nordmann, 1839:
200. Spalax typhlus xantodon Nordmann, 1840: 35. Mustyphlus Pallas, 1778: 154—165,
Tab. VIII. Ommatostergus Pallasii Keyserling and Blasius, 1840.

Holotype. Described from a find in the Zadone Steppes (Novokhoper).
Number of samples and place of storage not known.

Material investigated. More than 300 skulls and skins obtained within
the boundaries of Ukraine SSR, mixed region of Russian Federation and
northern Caucasus; stored in the reserves of the collections of the Institute
of Zoology AN Ukraine SSR, Moscow State University, Kiev State
University, and the Zoological Institute AN SSSR.

Diagnosis. Measurements are, on the average, similar to those of the
sandy mole rat (body length, 197-232-290 mm; length of feet, 23.0-26.3-
30.0 mm; condylobasal length of skull, 37.2-49.8-58.4 mm; length of
upper row of permanent molars, 7.3-8.2-9.0 mm; length of lower row
of permanent molars, 6.8—7.6-8.4 mm). The rostral section of the skull
gradually narrows in an anterior direction and is wedge-shaped. The width
of the nasal bones posteriorly is more than the similar width of each of
the premaxillary bones, and the latter, in turn, is less than half of the
anterior total length of nasale, or approximately equal to it. In addition,
the width of the nasal bones anteriorly exceeds approximately twice or
more their posterior width (in all cases, it was measured at the level of
the temporo-premaxillary sutures). The temporo-nasal and the temporo-
premaxillary sutures are straight, usually slightly step-like because of the
bifurcation of the nasale behind the line of the temporo-premaxillary

257

sutures. The groove between the nasal bones in the region of the temporo-
nasal sutures is absent or is lightly defined, because of which the posterior
ends of the nasale are blunt. The length of the nasal bones exceeds the
total length of the parietal and temporal bones. The antero-external edges
of the zygomatic arches are practically not bent down. The masseter area
is short and has a slightly developed anterior tubercle; its length is approx-
imately equal to the distance between the anterior ridge of the latter and
the suture of the intermaxillary and maxillary bones. The external wall
of the suborbital process is narrow; its least width is less than the length
of the anterior permanent molar. The alveolar tubercles in adult and old
individuals are hardly defined, and are placed apart from the anterior edge
of the alveolus of М! at a distance exceeding the length of the tooth. The
auditory opening is small; its greatest diameter in the majority of cases
is less than the length of M1, and is rarely equal to it. The alveolar process
of the lower jaw considerably exceeds its articulate one in regard to height
(in adult and old individuals). The coronary process is high. The corono-
alveolar groove is slightly step-like. The closed foramen of the pelvic
bone is large; its length approximately coincides with the length of the
acetabulum.

Description. The rostral section of the skull is not wide and gradually
narrows down anteriorly. Its width at the level of the anterior edges of
the suborbital foramen always exceeds the same at the center. The total
length of the nasal bones posteriorly is always more than the width of
the premaxillary bone, and the latter, in its turn, is less or equal to half of
the total anterior width of the nasale. In addition, the nasal bones are
strongly narrowed in the posterior section; the total anterior width of the
nasale exceeds twice or more the posterior width. The groove in the region
of the temporo-nasal suture is absent or slightly marked, because of which
the posterior ends of the nasal bones are blunt and do not form the
sizable bifurcation characteristic of S. graecus (Figure 74). It should also
be mentioned that the nasal bones of the common mole rat are, on an
average, relatively longer than those of the giant mole rat and, perhaps,
even those of the sandy mole rat. The relation of their length to the length
of row of permanent molars is 231.0-259.5-306.0 in adult and old indivi-
duals, and 205.0-220.0-231.0 in the young and semi-mature. Furthermore,
the nasale, as in S. arenarius, are apparently relatively wider anteriorly,
on the average, than in the giant mole rat; the relation of their total width
to the length of M?-M® is equal to 84.5-96.4-121.0 in adult and old
individuals, and 77.1-82.1-87.0 in the young and semi-mature. The length
of the nasal bones, as a rule, exceeds the total length of the temporal and
parietal bones; the magnitude of the relation is 95.0-106.5-120.0 for
adult and old individuals, and 94.2-101.9-106.7 for young and semi-
mature animals. The structural characteristics of the temporo-nasal and

17

258

temporo-maxillary sutures have been given in the diagnosis. The nasal
openings are relatively narrow though, on the average, probably wider
than in the giant mole rat. The relation of their width to the length of row
of permanent molars is 70.8-88.0-101.0 for adult and old individuals,
and 70.8-77.2-80.7 for young and semi-mature animals. The constriction
behind the eyes is slightly more expressed than in mole rats from the

Е G

Figure 74. Spalax microphthalmus Giild. Natural size.
Legend is the same as in Figure 50.

259

giganteus group; the relation of width behind the eyes to length of row of
permanent molars is 77.9-94.2-114.0 for adult and old individuals, and
166.0-176.0-195.0 for the young and semi-mature. The temporo-parietal
section is shortened; the ratio of the total length of the temporal and
parietal bones to the length of M'-M® is respectively equal to 218.0-
233.5-302.0 and 209.0-218.0-227.0. The parietal bones are relatively
longer and greatly widened; the relation of length and width for each of
them to the length of row of permanent molars is respectively equal to
107.0-130.0-156.0 and 45.3-68.4-92.9 in adult and old individuals, and
116.0-128.0-134.0 and 71.9-86.2-94.2 in young and semi-mature animals;
the relation of the total width is 80.2-140.0-179.0 in adult and old indivi-
duals, and 166.0-176.0-195.0 in the young and semi-mature. Their sutures
form a pentagon or five-pointed star. The triangular depression on the
temporal bones in the area of displacement of the sagittal ridge is absent
(Figure 74). The temporo-parietal and temporo-frontal sutures form a
blunt angle. The upper diastema and hard palate are elongated. Thus, the
magnitude of the diastema-tooth index is 204.0-241.0-317.0 in adult and
old individuals, and 177.0-192.0-214.0 in the young and semi-mature.
The relation of length of hard palate to length of row of permanent molars
is respectively equal to 334.0-378.0-463.0 and 302.0-322.0-347.0. The
structural characteristics of the masseter area and of the alveolar tubercles
have been discussed fully in the diagnosis. The hard palate, on the whole,
is apparently wider than in the giant mole rat at the level of the anterior
permanent molars, and narrower than in the sandy mole rat. Its width
in adult and old individuals only slightly exceeds the length of M!. The
zygomatic arches are thin anteriorly. Their antero-external edges are
almost not bent down. The malar angle is considerably less than 45°. The
external wall of the suborbital foramen is constricted; its least width is
considerably less than the length of the anterior permanent molar.

The suborbital foramen itself is high; its length considerably exceeds
the length of the upper line of permanent molars. The zygomatic arches
are considerably elevated posteriorly in relation to the fossa glenoidea.
The suture between the malar processes of the maxillae and the frontale
(situated near the outer wall of the suborbital foramen) is strongly tapered.
The inner crest of the fossa glenoidea is marked more sharply than in
the giant mole rat, and less so than in the sandy mole rat. The articulating
surface itself is wide. The base of the occipital bone is wide because of
which the auditory bullae are widely separated. Thus, the greatest distance
between the external edges of the tuberculum pharyngeum laterale con-
siderably exceeds the length of M!—M2. The auditory bullae are, on the
average perhaps, relatively wider than in representatives of the giganteus
group. The relation of their width to length of the permanent molar is
equal to 92.8-101.5-116.0. The structural characteristics of the auditory

260

opening have been discussed in the diagnosis. The occipital section of the
skull is, on the average perhaps, relatively higher than in all the presently
living representatives of the genus; the magnitude of the relation of the
occipital bone measured from the upper edge of the occipital foramen
to the largest width of the occiput, is 52.5-55.0-66.1.

The upper incisors are relatively narrow (for representatives of the
genus); the relation of width to antero-posterior cross section is 104.4—
112.0-120.8. Their anterior surface is flattened.

М: (length, 2.4-2.7-3.2 mm; width, 2.1-2.5-3.0 mm; relation of width
to length, 80.6-91.1-107.1) has a type of structure in the grinding surface
of the teeth akin only in very young animals to the same in giant and sandy
mole rats, and a number of representatives of the microphthalmus group
‘in S. graecus (the paracone is not fused with the anterior collar but is
isolated from the neck which joins the protocone and hypocone; two
intruding folds are in the outer line; Figure 75). In the majority of the
cases, the central external tubercle is fused with the anterior collar, but
separated from the neck joining the anterior and posterior internal tuber-
cles, as a result of which the tooth is characterized by the presence of only
one intruding fold in the outer line in early and middle stages of wear
(in young, semi-mature, and partly in adult animals). The antero-internal
part of the outer intruding fold closes into a mark as age advances. The
protocone and hypocone in the majority of cases are fused and rarely
separated. The remnants of the metaconid are rarely preserved at very
early stages of tooth erosion. The grinding surface in adult and old animals
is similar, on the whole, to the one in the giant mole rat and the sandy
mole rat. The intruding folds close into marks due to tooth erosion in the
following order: the inner part of the external, the external, and finally,
the internal one. There are two roots—the massive antero-internal (formed
by the fusion of the antero-external and the internal roots), and a weakly
developed and free postero-external. The antero-internal root has no
markings or bifurcation. Perhaps, the fusion of the postero-external root
with the antero-internal does not take place.

М? (length, 2.1-2.4—2.8 mm; width, 2.1-2.5-2.9 mm; relation of width
to length, 92.3-105.3-124.0) is similar to the same molar in the sandy
mole rat in regard to structure of the wearing surface. However, it is
perhaps relatively narrower, on the average. It is quite different from the
same in mole rats of the giganteus group by a constant presence of three
roots—the massive internal, and the weakly developed anterior and
posterior externals.

МЗ (length, 1.6-2.1-2.4 mm; width, 1.9-2.2-2.6 mm; relation of width
to length, 90.5-107.0-120.0) is like the previous molar, on the whole, and
similar to the same one in the sandy mole rat. However, in the common
mole rat, the completely separated anterior and posterior tubercles are

261

often observed and, similarly, a considerable tendency toward complexity
in the grinding surface is observed on the teeth of young animals because
of the formation of additional tubercles and layers. Besides, a lesser degree

Figure 75. Spalax microphthalmus Gild. x 10.

Upper row of permanent molars: A to F—young and semi-mature;
G to L—adult; M to O—old individuals.

262

of reduction of the antero-external root is characteristic of the МЗ of 5.
microphthalmus. The latter is almost always not fused with the postero-
internal root (the fused postero-external and the single internal root), and
is represented in the alveolus by an independent socket.

The lower jaw has an elongated diastema; the value of the diastema-
tooth index is 98.9-117.0-138.7 in adult and old animals, and 92.0-106.0-
125.0 in the young and semi-mature. The horizontal branch is relatively
high; the relation of its height to the length of the lower row of permanent
molars is 109.0-129.2-146.4 in adult and old animals, and 92.0-106.0—
125.0 in the young and semi-mature. The alveolar process, as in the sandy
mole rat, is high and exceeds the articulating one in both adult and old
animals in this regard. The height of the process from the inner side begin-
ning from mature conditions, as a rule, considerably exceeds the length
of the lower row of permanent molars (value of the corresponding index
in common mole rats, 95.0-114.4-138.6). The incisura corono-alveolaris,
as in previous species, is slightly step-like; its anterior edge goes into the
coronary process. The coronary process is high. The external surface of
it is step-like which, as has been shown above, is related to the encroach-
ment of the ridge of the corono-alveolar groove. Because of the approx-
imate coincidence of the height of the coronary and the length of the
upper edge of the articulating process, the corono-articular groove is
correctly divided (Figure 74). The common mole rat and the sandy mole
rat do not differ from each other in regard to the structure of the corono-
alveolar and the corono-articulating ridges, the anterior fossa between
them, and also in regard to the position of the mandibular foramen in
relation to the edge of the incisura corono-condyloidea. The articulating
surface of the proc. condyloideus is wide; the relation of width to length
is 50.0-57.0-66.7.

The lower incisor is, on the average, probably relatively wider than
that of all the presently known representatives of the genus. The relation
of the width of the antero-posterior cross section is 100.0-109.5—120.7.

М, (length, 2.2-2.5-3.0 mm; width, 2.1-2.4—2.7 mm; relation of width
to length, 79.3-94.5-108.3) differs from M, of the sandy mole rat by the
process of an additional anterior intruding fold in the outer line, or its
vestige in the shape of an anterior mark, and also, on the average, a less
reduced entoconid in young and semi-mature animals (Figure 76). In
addition, the metaconid is fused with the anterior collar in the given stages
of wear, and through it with the protoconid also. In some cases, the neck
of the antero-internal tubercle at the place of fusion with the anterior
collar shows the marks of division. The protoconid and hypoconid are
fused in all stages of wearing. Because the tooth in young and semi-mature
animals has an additional outer (almost always) and inner intruding
(rarely) fold, the number of the latter in the outer and inner lines at given

263

stages of wear may vary from one to two. In adult and old animals, the
tooth always has an inner and outer intruding fold. The order of closure
of the intruding folds into marks is as follows: the antero-internal and

Figure 76. Spalax microphthalmus Gild. x 10.

Lower row of permanent molars: A to F—young and semi-mature;
G to J—adult; K to M—old individuals.

264

external additional in the given order, the main internal, and finally the
main external. The tooth has two roots; the posterior is better developed
than the anterior one.

М, (length, 1.9-2.2—2.7 mm; width, 2.1-2.5-2.9 mm; relation of width
to length, 95.4—110.7-128.5) is, on the average, probably relatively wider
than in the preceding species: In regard to the general configuration of
the grinding surfaces, it is generally similar to the М, (permanent molar)
of sandy and giant mole rats. There are two roots; the posterior is more
developed than the anterior. Sometimes the roots exhibit a tendency
toward fusion.

М. (length, 1.9-2.2-2.5 mm; width, 1.7—2.2-2.7 mm; relation of width
to length, 81.8—101.4—121.0), like the preceding molar, is principally
similar to the permanent molar of the sandy mole rat in regard to its
relative width of the corona, and the nature of the structure of the grinding
surface and roots.

Comparison. The traits common for all the representatives of the micro-
phthalmus group which allow one to differentiate them from the species
of the giganteus group, were discussed above (page 243). As far as the
common mole rat is concerned as a species, the following differences
need to be considered in addition to those observed earlier.

1. The temporo-frontal and temporo-parietal sutures form a blunt
angle; in mole rats of the giganteus group, the temporal bones are placed
on the border of the parietals and the frontale at an acute angle (the trait
is clearly exhibited in adult and old animals).

2. The temporo-nasal and temporo-premaxillary sutures form a line
that is almost straight in common mole rats; in giant and sandy mole rats,
they form an angle with its apex directed forward.

3. The almost unbent downward anterior outer borders of the zygo-
matic arches and a malar angle that is much less than 45°; in representa-
tives of giganteus group, the anterior outer borders of the zygomatic
arches are considerably shifted downward and the malar angle is almost
equal to or slightly more than 45°.

4. In mature and adult animals, the temporal bones ident in the front,
forming a figure resembling a regular pentagonal star (Figure 74) to some
extent; in giant mole rats, and to a lesser degree in sandy mole rats, these
bones are constricted, because of which the pentagon is elongated in a
longitudinal direction with a highly elongated anterior ray.

5. An elongated nasale whose length exceeds the combined length of
the temporal and parietal bones, as a rule; in mole rats of giganteus group,
an inverse relationship is observed in the majority of cases.

6. In the majority of cases, a fused paracone and anterior collar in
the early and middle stages of wear of the first permanent molar of the
upper jaw; in giant and sandy mole rats, the middle outer tubercle is not

265

fused with the anterior collar though it communicates with the suture
connecting the protocone and hypocone.

In the remaining features, S. microphthalmus is identical with the sandy
mole rat although some differences are observed in the average values of
indices for the skull structure, the lower jaw, and the permanent molars.
These differences are readily observed on comparing the descriptions of
both the species given earlier; therefore, it appears to us that there is no
urgency to discuss them in detail. The most substantial differences, in
addition to those mentioned, could be the following:

1. Inthe common mole rat the external wall of the infraorbital foramen
is narrow; its width in the narrowest part is considerably less than the
length of the anterior permanent molar. In the sandy mole rat, the bony
bridge above the for. infraorbitale is slightly widened; the least width is
approximately equal to the length of М! or clearly exceeds it.

2. A broadened fossa glenoidea with a weakly developed inner ridge,
and a correspondingly short and wide articulating condyle of the lower jaw
(width of the condylus exceeds half its length or, rarely, is approximately
equal to it; the values of the corresponding relations are 50.0-57.5-66.7).
In S. arenarius, the articulating fossa on the skull is narrowed with a highly
developed internal ridge. Correspondingly, the condyle of the lower jaw
is narrow and long. Its width is considerably less than half its length (38.8-
45.2—48.2).

3. The antero-internal tubercle—the metaconid оп M,—of young and
semi-mature animals is fused with the anterior collar (independent in the
sandy mole rat). In addition, the anterior permanent molar of the common
mole rat is characterized in the early and middle stages of wear by the
presence of an additional intruding fold in the outer line, or its vestige
(always absent in the sandy mole rat).

It differs quite clearly from S. polonicus which is a close species by:

1. Elongated nasal bones and a shortened temporo-parietal of the
skull. The length of the former, with rare exception, exceeds the total
length of the temporal and parietal bones. The trait mentioned can be
quite clearly seen while comparing such traits as the relation of the length
of the nasale, and the total length of frontale and parietale to the length
of the row of permanent molars. The former value in the common mole
rat is 231.0-259.5-306.0, and of the latter, 218.0-233.5-302.0 as against
208.1-235.4—260.0 and 240.0-270.9-296.6 in 5. polonicus.*

2. The shape of the temporo-nasal and temporo-premaxillary sutures
(almost a straight line in the common mole rat, with an angle that has an
apex directed forward in the Podolsk mole rat).

3. A fused protocone and hypocone on М! in the early and middle

1 The indices here and afterward are given only for adult and old animals because
the author did not possess a sufficient number of young and semi-mature S. polonicus.

266

stages of wear in the majority or cases (always separated in the Podolsk
mole rat).

4. Complex anterior lower permanent molars in young and semi-mature
animals. M, of the common mole rat is characterized in early and middle
stages of wear by the presence of an additional external intruding fold,
or its vestige in the shape of a small anterior mark which is absent in S.
polonicus.

5. A comparatively small auditory opening, the greatest diameter of
which, in the majority of cases, is less than the anterior permanent molar
and sometimes is approximately equal to the latter. In the Podolsk mole
rat, the said measurements always exceed the length of МЕ.

In addition, the differences between the common mole rat and the
Podolsk mole rat can be seen in the average values of the following traits:

1. The parietal bones and the upper diastema are relatively longer; the
relation of the length of the parietale to the length of the row of permanent
molars, and the diastema-tooth index, is respectively equal to 107.0-130.0-
156.0 and 204.0-241.0-317.0 in the common mole rat, as against 78.4—
114.1-135.8 and 198.8—230.4—263.6 in the Podolsk mole rat.

2. The nasal bones are narrower anteriorly (84.5-96.4—121.0 as against
87.2-102.5—-113.6).

3. The total width of the parietale is relatively greater (80.2-140.0-179.0
as against 84.0-117.0—-142.7).

4. The nasal bones are placed relatively low (33.3-37.4—45.2 as against
36.6-44.8—51.1). it

5. The occipital bone is relatively higher; the relation of its height
measured from the upper edge of the foramen magnum to the greatest
width of the occipital is 52.5-55.0-66.1 as against 43.0-50.1-53.8.

6. The upper incisors are relatively narrower; the relation of width to
antero-posterior cross section is 104.4—112.0-120.8 as against 110.3-119.5-
130.7.

7. The lower diastema is relatively longer; the value of the diastema-
tooth ratio is 98.9-117.0-138.7 as against 100.0-109.3-122.0.

8. The horizontal branch is relatively higher; the relation of its height,
at the level of the posterior edge of M, externally, to the length of the
lower row of permanent molars is 109.0-129.2-146.4 as against 106.1-
122.1-134.7.

9. М» is relatively narrower (relation of width to length is 95.4-111.0-
128.5 as against 113.0-117.2-127.2).

Finally, the common mole rat differs from the presently living Bukovin
mole rat, S. graecus, by:

1. Nasal bones which are narrowed posteriorly and widened anteriorly
(width anteriorly exceeds twice and more the width posteriorly). In S.
graecus, the total anterior width of the nasale exceeds considerably less

267

than twice the posterior width. Furthermore, the posterior groove оп the
nasal bones of the common mole rat is absent or faintly present and the
ends of the nasale are blunt. In common mole rats, the latter is always well
developed, the posterior ends of the nasal bones are sharpened, and the
nasal bones themselves are greatly bifurcated posteriorly.

2. A narrow external wall in the infraorbital foramen, the least width
of which is considerably less than the length of the anterior permanent
molar. In the Bukovin mole rat, the width of the wall of the infraorbital
foramen in its narrowest part considerably exceeds the length of M?.

Furthermore, the infraorbital foramen itself in the common mole rat
is relatively higher. Its height considerably exceeds the length of the upper
row of permanent molars whereas in the Bukovin mole rat, the values of
these measurements approximately correspond to each other.

3. A greatly tapered position of the sutures between the frontale and
the malar process of the maxillary bone in relation to the longitudinal axis
of the external wall of the infraorbital foramen. In S. graecus it is weakly
tapered or even placed in a transverse position.

4. The absence of a three-angled fossa in lieu of the displacement of
the sagittal ridge. It is always present in the Bukovin mole rat.

5. A weakly developed upper alveolar tubercle.

6. Slender, almost not bent down, antero-external edges of the zygo-
matic arches, and a malar angle which is considerably less than 45°. In S.
graecus the zygomatic arches are massive, sharply bent down, and have
a malar angle which approaches or is roughly equal to 45°.

7. Widened parietal bones; the relation of the total width of the two
parietale to the length of row of permanent molars is 80.2—140.0-179.0 as
against 41.1-60.1-85.5 in the Bukovin mole rat.?

8. A less step-like coronary-alveolar groove in the lower jaw. It is step-
like in S. graecus because of the great development of its ridge. This trait
equally differentiates the common mole rat from the fossil Late Pliocene
S. minor.

9. The non-serrated apex of the coronary process. It is quite serrated
in the Bukovin mole rat.

10. A simplified structure of the anterior permanent molar. In S.
graecus, M! is similar to the same molar in 5. giganteus and 5. arenarius
in regard to complexity.

The differences between the above-mentioned species could also be
found in the average values in the number of structural traits of the skull
and the lower jaw. Thus, for example, the common mole rat compared
to the Bukovin mole rat has a relatively short temporo-parietal section
of the skull, elongated and widened parietal bones, a comparatively low

1 As in the case of 5. polonicus, measurements are for adult and old animals only,
because we did not possess a series of skulls for young and semi-mature animals.

268

nasal aperture and high occipital bone, ап elongated lower diastema and
a high horizontal branch of the lower jaw, and widened lower incisors.
The said differences stand out more clearly when the respective indices
are compared, the values of which can be found in the section devoted
to them. In some cases, the trend of these changes coincides with similar
ones in the Podolsk mole rat (a relatively wide rostrum and parietale).

The common mole rat takes up a middle position between the Podolsk
and Bukovin mole rat in regard to a number of traits because, in the latter,
the individual differences have a great importance. In particular, the nasal
bones in S. microphthalmus are, on the average, shorter than in S. graecus;
the relation of their length to the length of row of permanent molars is
231.0-259.5-306.0 as against 249.0-273.0-296.0. ;

Measurements. Condylobasal length of skull, 37.2-50.0-58.4 mm; basal
length of skull, 34.3-46.8-54.2 mm; length of nasal bones, 15.8—20.9—
25.9 mm; total length of parietal and temporal bones, 15.9-19.9-24.0 mm;
length of parietal bones, 8.9-10.7-12.8 mm; length of upper diastema, 13.4—
19.4-24.7 mm; length of hard palate, 23.0-30.7-37.1 mm; length of upper
row of permanent molars, 7.0-8.2-9.0 mm; width of nasal aperture, 5.3—
7.1-8.5 mm; incisorial width, 7.0-8.7-10.3 mm; width of nasal bones
anteriorly, 5.4-7.8-9.6 mm; rostral width, 9.3-11.6-14.7 mm; width be-
hind the eyes, 6.7—7.9-9.9 mm; width of two parietale, 8.7-11.8-15.4 mm;
width of parietal bones up to the lambdoid ridge, 3.9-5.4—6.7 mm; malar
width, 31.1-39.7-45.9 mm; maximum width of occiput, 26.3-33.9-
38.8 mm; length of auditory bullae, 10.7-12.7-14.5 mm; width of auditory
bullae, 7.4-8.2-9.1 mm; width of upper incisor, 2.2—2.9-3.4 mm; antero-
posterior cross section of upper incisor, 2.0-2.6-3.3 mm; height of nasal
aperture, 2.4-3.0-4.0 mm; condylar length of lower jaw, 24.2-33.0-
40.1 mm; angular length of lower jaw, 23.3-32.2-39.8 mm; length of
lower diastema, 6.7-8.8—10.4 mm; length of lower row of permanent
molars, 7.3—7.6-8.4 mm; height of horizontal branch at the level of the
posterior edge of the alveolus of М, externally, 7.3-9.6-11.2 mm; thick-
ness of the horizontal branch at the level of Мь, 3.5-4.7-6.5 mm; height
of alveolar process internally, 3.7-8.2—11.2 mm; width of lower incisor,
2.1-3.1-3.8 mm; antero-posterior cross section of the lower incisor, 1.8—
2.9-3.7 mm.

Note. The common mole rat is approximately on the same level of
specialization toward a burrowing type of life as S. arenarius. Traits like
an elongated upper and lower diastema, widened upper and lower incisor,
a skull which is relatively high in the occipital portion, a comparatively
high horizontal branch, and an alveolar process of the lower jaw, are
proofs of this: moreover, the latter, as in the sandy mole rat, is character-
ized by a sufficiently well-developed ridge of the corono-alveolar groove.
In addition, the species has a simplified structure of permanent molars,

269

the roots of which are less reduced than in the sandy mole rat. The latter,
along with rather weak development in the sites of attachments of the
masticatory muscles (masseter area of the skull, the antero-external
portions of zygomatic arches, and others) proves, perhaps, the trend of
development toward adaptation to eating more succulent and soft vegeta-
tive food.

It has also to be noted that the common mole rat considerably pre-
served characteristic resemblances to the fossil Pliocene S. minor from
around the Azov Sea. This permits one to consider with a high degree of
probability that this species is a direct descendant of the latter.

Distribution and geological age. Ц spreads up from the Dnieper west
to the Volga and Pre-Caucasus in the east (in the Dnieper region, it is
absent in the Aleshki Sands portion). The northern borders of the spread
pass through approximately the Kiev region along the southern part of
the Chernigovskaya region; in the eastern portion through the Kursk
and Orlov regions, in the southern portion through Tula, the Tambovsk
region and Moldov ASSR, along the southern portion of the Ulyanov
region. The southern border is approximately in line with Kakhovka,
the Azov shore up to the Krasnodar and Stavrapol regions, but for their
southern parts. Holocene, recent. Holocene remains from the excavation,
related to the mole hill forest, are found everywhere within the area of the
species. Finds of closely related forms are also known from Pleistocene
sediments (mole hill forest).

Subspecies. Geographical variability has not been studied at all. The
northern Caucasian form could very well be an independent subspecies.

4. Spalax polonicus Mehely, 1909—Podolsk Mole Rat

Mehely, 1909: 34, 35, 194—202. typhlus Kessler, 1850: 74-77 (nomen praeocupatum).
diluvii Nordmann, 1858; 164. podolica Troussart, 1898: 570 (nomen nudum). zemni
Reshetnik, 1941: 28-31, Figures 4, 5, 8a, 12. Microphthalmus podolicus Bobrinskii et al.,
1944: 362. Microphthalmus polonicus Vinogradov and Gromov, 1952: 177. Podolian
_ Marmot Pennant, 1771: 274 (nomen nudum). Glis zemni Erxleben, 1777, Systema Regni
Animalium, I: 370-371 (nomen nudum). Mus typhlus Dwigubski, 1804: 78-80 (nomen
praeocupatum).

Holotype. Teachers Museum of L’vov, No. 261/430, Ukraine SSR,
around Krements city (village Vishnevets), Ternopolsk region.

Material investigated. Twenty-five skulls and skins found in and around
Nikolaev, Odessa and Dnepropetrovsk regions (recent), right bank portion
of Kiev and Zhitomir regions (subfossil). All stored in the collections of
the Institute of Zoology AN Ukraine SSR.

Diagnosis. Measurements are, on the average, close to that of S. micro-
phthalmus (body length, 200-280 mm; length of foot, 25-30 mm; condylo-
basal length of skull, 39,3-49,2-56.5 mm; length of upper row of perma-

270

nent molars, 7.3-8.2-8.8 mm; length of lower row of permanent molars,
7.2-7.6-8.2 mm). The skull, as a whole, is similar to that of the common
mole rat. It differs in regard to the shortened nasal bones, the length of
which is considerably less than the total length of the temporal and parietal
bones, the line of the temporo-nasal and temporo-premaxillary sutures
forming an angle with its apex directed forward, a relatively large auditory
aperture, the maximum diameter of which exceeds the length of the
anterior permanent molars. The closed foramen of the pelvic bone is
almost completely overgrown; its length is considerably less than the
length of the acetabulum.

Description. The rostral section of the skull is not broad and gradually
narrows in an anterior direction as a wedge-shaped structure, as in the
common mole rat. Its width at the level of the anterior edges of the infra-
orbital foramen always exceeds the same in the center. The total length
of the nasal bones posteriorly is always more than the length of the
premaxillary bone, and the width of the latter, in turn, is less or approx-
imately equal to half of the anterior width of the nasale. Furthermore,
the nasal bones are primarily in the posterior section; the width of the
nasale exceeds anteriorly twice or more times the width posteriorly. As
in S. microphthalmus, the groove in the region of the temporo-nasal sutures
is absent or is slightly marked because of which the posterior ends of
the nasal bones are blunt and do not form a fork-like bifurcation (Figure
77). However, the nasal bones are considerably shorter than in the common
mole rat. As has already been mentioned in the diagnosis, their length is
considerably less than the total length of the temporal and parietal bones
(the value of the corresponding index is 79.2-86.4-95.0 in adult and old
animals, 76.3 and 92.8 in the young and semi-mature), and the ratio of
the length of nasale to the length of row of permanent molars is 208.1-
235.4-260.0. Additionally, the nasale are probably wider, anteriorly, on
the average, than in S. microphthalmus; the relation of their anterior total
width to the length of row of permanent molars is 87.2-102.5-113.6 in
adult and old animals, and 87.7 and 92.5 in the young and semi-mature.
The structural characteristics of the temporo-nasal and temporo-pre-
maxillary sutures have been mentioned in the diagnosis. The nasal aperture
is comparatively wide; the relation of its width to the length of row of
permanent molars is 80.2-93.4-105.0 in adult and old individuals, and
82.2 and 91.3 in the young and semi-mature. The constriction behind the
eyes is, on the average, possibly more strongly expressed than in the
common mole rat; the relation of the width behind the eyes to the length
of M!—M3 is 77.3-88.5-101.2. The temporo-parietal section is elongated ;
the relation of the total length of the temporal and parietal bones to the
length of row of permanent molars is 240.0-270.9-296:6 in adult and old
animals, and 242.5 and 283.5 in the young and semi-mature. The parietal

271

bones are short and narrow; the relation of the length of each and their
total width to the row of permanent molars is respectively equal to 78.4—

Я N
ДА
y

SSS

>
рен
А
4

Figure 77. Spalax polonicus Meh. Natural size.

Legend is the same as in Fig. 50.

272

114.1-135.8 and 84.0-117.0-142.7. As in the preceding species, it forms a
pentagon suggesting a five-angled star. The triangular depression on the
temporal bone, in lieu of the displacement of the sagittal ridge, is not
expressed. The temporo-parietal and the temporo-frontal sutures form a
blunt angle; rarely, this angle is almost straight. The upper diastema and
hard palate are, on the average, probably shorter than in the common
mole rat; the values of the diastema-tooth and palate-dental indices are
respectively equal to 198.8—230.4—263.6 and 331.4-369.3-408.0. The struc-
ture of the masseter. area, the alveolar tubercles, the hard palate, the
zygomatic arches, the infraorbital foramen and its external wall, the
sutures between the maxillary and temporal bones, the fossa glenoidea,
the base of the occipital bone, and the auditory bullae is, on the whole,
similar to the same in S. microphthalmus. However, the auditory aperture
in the Podolsk mole rat is considerably larger than in the common mole
rat; its maximum diameter always exceeds the length of the anterior
permanent molar. The occipital section of the skull is probably, on the
average, relatively lower than in S. microphthalmus; the relation of the
height of the occipital bone, measured from the upper edge of the for.
magnum, to the maximum width of the occiput is 43.0-50.1-53.8.

The upper incisors are widened; the relation of the width to the antero-
posterior cross section is 110.3-119.5-130.7. The anterior surface is
flattened.

М: (length, 2.5-2.6-2.9 mm; width, 2.2-2.4-2.7 mm; relation of width
to length, 82.1-90.9-103.8) in regard to the configuration of the grinding
surface is similar to the same permanent molar of the common mole rat.
Thus, the paracone in all stages of wearing is fused with the anterior collar
because of which the tooth is characterized by the presence of only one
intruding fold in the outer line (Figure 78). In addition to this, it differs
from S. microphthalmus in that the protocone and hypocone in the early
stages of wearing (in young and semi-mature, and even in some old indivi-
duals) are separated, as aresult of which the outer and inner intruding folds
fuse at the ends of each other. With age, the intruding folds close into
marks approximately in the same order as that of the similar permanent
molars of the common mole rat (the inner part of the external, the external,
and finally, the internal). Furthermore, the fusion of the anterior and
posterior external tubercles takes place. The fusion of the roots is expressed
to a greater extent than in S. microphthalmus. In the majority of cases,
the tooth is characterized by the presence of only a complex root formed
by the fusion of the massive inner, and the weakly developed anterior
and postero-external. During this, the vestiges of the fusion of the antero-
external and the inner roots are altogether absent. However, the marks of
the fused postero-internal root are almost always evident on the very root,
and also in the structure of the alveoli.

273

М? (length, 1.9-2.3-2.5 mm; width, 2.2-2.5-2.7 mm; relation of width
to length, 104.0-108.9-117.4), like the preceding molar, is principally simi-
lar in regard to the nature of the structure of the wearing surface to the
similar permanent molar in the common mole rat. However, it differs
from the latter in that a complete separation of the protocone and hypo-
cone is observed in the young and semi-mature. Furthermore, the closure
of the antero-internal section of the intruding fold of the outer line into
mark in the Podolsk mole rat takes place, perhaps, in rather later stages
of tooth erosion than in the common mole rat; the fold itself is simpler,
on the whole, because of a rather weakly developed pleating of its walls.
The order of the closure of the inner folds into marks because of tooth
erosion is, perhaps, the same as in the preceding molar. It should also

Figure 78. Spalax polonicus Meh. х 10.

Upper row of permanent molars: A to C—young and semi-mature;
рю H—adult; J—old individual.

18

274

be noted that as distinct from the common mole rat, the anterior and
posterior outer root of the tooth completely fuse with the single inner
one, although traces of fusion are fairly clearly expressed on the root itself
as well as on the structure of the alveolus.

M3 (length, 1.8-1.9-2.4 mm; width, 2.0-2.1-2.4 mm; relation of width
to length, 96.8-111.4-122.2), in young and semi-mature animals, has a
more simplified grinding surface as compared to the same molar of the
preceding species. Because of the presence of only one intruding fold and
fused anterior and posterior internal tubercles, the degree of complexity
more closely resembles that of adult S. microphthalmus than in the young
and semi-mature. In addition, the roots of the tooth differ from similar
teeth in the common mole rat, by showing a greater tendency toward
fusion. The antero-external and the complex postero-internal roots are
fused, though marks from the fusion area are clearly seen on the roots and
in the alveolus.

The lower diastema is shortened; the value of the diastema-tooth index
15 100.0-109.3-122.0. The horizontal branch is, on the average, relatively
lower than in the common mole rat; the relation of its height to the length
of the lower row of permanent molars is 106.1-122.1-134.7. As in the
desert mole rat and the common mole rat, the alveolar process is high;
in adult and old animals it considerably exceeds the articulating one in
height. Its height from the inner side, at a mature stage, exceeds, as a rule,
the length of the lower row of permanent molars (100.0-114.1-133.6).
The structure of the coronary-alveolar and the coronary-articular grooves,
and the ridges of the coronary and its articulating process, are, on the
whole, similar to the same in the common mole rat.

The lower incisor is wide; the relation of its width to the antero-
posterior cross section is 97.0-104.3—110.7.

М, (length, 2.2-2.4-2.7 mm; width, 2.4-2.5-2.7 mm; relation of width
to length, 92.3-101.0-118.2) is, on the average perhaps, relatively wider
than in the common mole rat. In regard to the general structure of the
grinding surface, it is very close to the same permanent molar in S. micro-
phthalmus (the metaconid in all stages of wearing fuses with the anterior
collar and weakly developed entoconid, Figure 79). It differs from the
earlier mentioned species by a permanent absence of an additional intrud-
ing fold in the outer line, or any of its markings, because of which the
number of intruding folds does not exceed one on each side of the corona.
If the additional fold is not taken into consideration, then, as has been
shown above in the teeth of common mole rats, the closure of the intruding
folds into marks due to tooth erosion in both species takes place in the
same general order. The tooth has two roots; the posterior is more
strongly developed than the anterior.

М, (length, 1.9-2.2-2.4 mm; width, 2.6-2.7-2.8 mm; relation of width

215

to length, 113.0-121.8—137.6) as in the previous molar, оп the average,
is probably relatively wider than in the common mole rat. In the remaining
aspects, it is not possible to differentiate the said permanent molars in
the Podolsk and common mole rat, though it is possible that in the former
the entoconid, on the average, is more strongly developed than in the
latter.

М. (length, 2.0-2.1-2.4 mm; width, 2.1-2.2-2.5 mm; relation of width
to length, 91.6-105.4-115.0) is also, on the whole, similar to the same
permanent molar of the common mole rat.

Comparison. A detailed comparison of the Podolsk and common mole
rat was done above (see page 265).

Because, as has been shown, the skull and the lower jaw of the Podolsk
mole rat is akin in basic structure to the same in S. microphthalmus, then,
the differences of the said species from S. graecus coincide, on the whole,

Figure 79. Spalax polonicus Meh. x 10.

Lower row of permanent molars: A to C—young and semi-mature;
D to H—adult; J—old individual.

276

in all the ten main points (pages 266-67). To the traits which allow dif-
ferentiating the Podolsk mole rat from the Bukovin mole rat may be
added the shape of the temporo-nasal and temporo-premaxillary sutures
which form an angle anteriorly directed in the former. In S. graecus, the
temporo-premaxillary sutures are straight or directed in relation to the
temporo-nasal suture externally and slightly forward, as a result of which
their line in the expected intersection should form an angle directed
backward.

Furthermore, the difference between the Podolsk and Bukovin mole
rat could be found in the average values of the following traits:

1. The nasal bones are relatively short; the relation of their length to
the length of row of permanent molars is 208.1-235.4—260.0 as against
249.0-273.0-296.0 in the common mole rat.

2. The rostrum is relatively narrow (132.5-145.5-158.0 as against
142.0-160.0-172.0).

3. The constriction behind the eyes is more pronounced (77.3-88.5—
101.2 as against 90.5-98.8—111.0).

4. The parietal bones are relatively wider (relation of their total width
to length of row of permanent molars, 84.0-117.0-142.7 as against 51.1-
60.1-85.5).

5. The lower diastema is relatively long (the value of the diastema-tooth
index is 100.0-109.3-122.0 as against 82.8—100.3—107.8).

6. М, and М, are relatively wide (relation of their width to length,
92.3-101.0-118.2 for Му, and 113.0-121.8-137.6 for Мь, as against respec-
tively 82.8-92.0-100.0 and 100.0-108.6-118.2 in the common mole rat).

It differs from the Late Pliocene Nogaisk S. minor by the shape of the
temporo-nasal and temporo-premaxillary sutures (the angle with an apex
directed forward in Podolsk mole rat, and an almost straight line in S.
minor), by a slightly step-like corono-alveolar groove (quite step-like in
S. minor), and by a widened, relatively short articulating surface of the
proc. condyloideus (its width in the Podolsk mole rat in the majority of
cases is half as long as the cord; in S. minor, it is less than half the length).

Measurements. Condylobasal length of skull, 39.3—49.2—56.5 mm; basic
length of skull, 36.5-46.1-53.6 mm; length of nasal bones, 15.8—19.3—
22.7 mm; total length of parietal and frontal bones, 20.6-22.4—26.1 mm;
length of parietal bones, 6.9-9.3-11.9 mm; length of upper diastema,
14.2-18.7-23.2 mm; length of hard palate, 26.5-30.2-35.9 mm; length
of upper row of permanent molars, 7.3-8.2-8.8 mm; width of nasal aper-
ture, 6.0-7.6-9.0 mm; incisorial width, 7.0-8.6-9.8 mm; width of nasal
bones anteriorly, 6.4-8.3-9.8 mm; rostral width, 9.8-11.9-13.9 mm; width
behind the eyes, 6.8—7.5—9.1 mm; width of two parietale, 7.3-10.2-12.1 mm;
width of parietal bones up to the lambdoid ridge, 3.9-5.7-8.1 mm; malar
width, 30.0-38.6-46.8 mm; maximum width of occiput, 28.3-34.5—

211

40.0 mm; length of auditory bullae, 10.8—12.6-13.9 mm; width of auditory
bullae, 7.5-8.5-9.2 mm; width of upper incisor, 2.4—3.0-3.4 mm; antero-
posterior cross section of upper incisor, 2.1-2.5-2.9 mm; height of nasal
aperture, 3.0-3.6-4.5 mm; condylar length of lower jaw, 31.2-33.1-
37.2 mm; angular length of lower jaw, 30.3-33.4-38.9 mm; length of
lower diastema, 6.9-8.1-9.0 mm; length of lower row of permanent
molars, 7.2—7.6-8.2 mm; height of horizontal branch at the level of the
posterior border of the alveolus of М, externally,’7.9-9.3-10.5 mm; thick-
ness of horizontal branch at the level of M,, 4.4-4.9-5.6 mm; height of
alveolar process internally, 7.6-8.7-10.3 mm; width of lower incisor, 3.0—
3.3-3.8 mm; antero-posterior cross section of lower incisor, 2.8-3.2—
3.8 mm.

Note. The Podolsk mole rat is, on the whole, similar to the common
mole rat in regard to the degree of specialization to a burrowing way of
life. The basic differences—related to the shortening of the nasal bones
of the former, as has been shown above, which is perhaps related to
another trait, namely, the shape of the temporo-nasal and temporo-pre-
maxillary sutures (the common line of them depends upon whether the
premaxillary bones are shorter or longer than the nasal bones)—are for
the time being inexplicable from the viewpoint of stabilizing selectivity
which, in Spalacidae on the whole, is directed toward progressive adapta-
tions to burrowing. A proposal for taking these traits as characteristics
of a less expressed specialization could be put forth because the traits
indicated are, no doubt, related to the degree of elongation or of shorten-
ing of the rostral section of the skull as a whole. The adaptive character
of the first trait can, perhaps, be proven by comparing the structure of
the respective section of the skull in different ecological forms within the
limits of one taxonomical group of rodents burrowing with help of incisors.
For this, the forms have only to be compared within the limits of a family
which has an exclusively underground way of life, and burrowers living
partly underground but obtaining their food on the surface. In this respect,
the family of field voles represents very good material for relating innumer-
able numbers of different zoological forms. A comparison of the relative
length of the rostral section of the skull in the group of Ellobii and other
field voles, as it were, confirms the opinion already expressed. The Ellobii
are characterized by a relatively drawn out narrow rostral section in
comparison to other Microtidae (short, wide). The foregoing makes us
examine the given differences between the Podolsk mole rat and the
common mole rat as an index of the comparatively lesser degree of special-
ization in the former to a burrowing way of life. This is confirmed even
by such structural characteristics of the skull and the lower jaw of the
Podolsk mole rat as a relatively short upper and lower diastema. However,
from the structure of the upper incisors, the said species perhaps stands

278

on a rather higher level of specialization than the common mole rat
(upper incisors in S. polonicus are, on the average, wider than in the latter).

At the same time, the Podolsk mole rat is characterized by more
specialized permanent molars compared to the common mole rat (struc-
ture of the grinding surface is simplified, reduction of roots is more pro-
nounced) which, with а known degree of probability, may be seen as a |
compensatory reaction for a shortened diastema (forward carrying of the
burrowing organ which, in this case, is the incisor), and related to its
general elongation, provides rather easier isolation of the buccal cavity
from falling gravel during digging.

The differentiation of the said species took place, perhaps, somewhere
on the border between the Early and Middle Anthropogene. At any rate,
we have skulls with complete formation of permanent traits from sediments
of the end of the Pleistocene epoch which allow unmistaken differentiation
of the Podolsk and common mole rat.

The name of the species is greatly confused. At present, three names
appear in literature: S. podolicus (Pennant), S. zemni (Erxleben), and S.
polonicus Mehely. The first name, introduced in literature casually by
Troussart (1898), relates to the first part of the Podolian Marmot (Pennant,
1771) as the name of a species; as Troussart did not give even a short
description, this name should be undisputedly cast out as a nomen nudum.
Moreover, in the work of Pennant, the nomenclature of the species given
in the translation is not in accord with the rules of bionomial nomen-
clature.

An attempt to confirm the name S. zemni (Erxleben) (in the first
description, Glis zemni Erxleben, 1777) was done by S. I. Ognev (1940,
1947), and after him even by Reshetnik (1941). However, the description
of Glis zemni subjects “mole rat” to considerable strain. To substantiate
the above, a translation in Russian given in the work of Erxleben (1777,
cited by Ognev, 1947) is given here: ““Measurement based upon squirrel.
Head is large, rostrum is short. The first lower teeth are of half the length
of the upper ones. The eyes are small, covered with hair. The ear holes
are short. The rounded paws have four fingers. The feet have five fingers.
The tail is short.”” From this description, we feel that even this nomen-
clature should not be used, that is a nomen nudum, since we have a right
to doubt whether the description is that of a mole rat at all.

The name S. typhlus (Pallas) under which this species has been intro-
duced in the works of Dwigubski (1804) and Kassler (1850) also cannot
be used because it is synonymous with S. microphthalmus Gild.

The name S. diluvii Nordmann, 1858, may be rightly retained because
it has been described elaborately though quite superficially. Moreover,
E. G. Reshetnik (1941) in his time proved that the subfossil S. diluvii and
S. polonicus were identical, and this is completely in line with our findings.

279

However, 5. diluvii was forgotten for some time and we feel that resurrect-
ing it now is not necessary.

In fact, the species was first described in detail by Mehely (1909) under
the name S. polonicus Mehely. This happens to be the only correct nomen-
clature at present.

In our literature, there is currently an unjustified tendency for taking
the Podolsk mole rat as a subspecies of the common mole rat (Bobrinskii
et al., 1944; Vinogradov and Gromov, 1952; Kuzyakin, 1963; Gromov
et al., 1963). However, as has been shown above, the Podolsk mole rat
has permanent traits which do not transgress and which formed during
a long geological history (throughout the Anthropogen), in addition to
the structure of the skull and permanent molars which allow an unmistak-
able differentiation of this species from S. microphthalmus. Add to the
aforesaid that the Podolsk mole rat also has genitals basically different
from the same of S. microphthalmus (Figure 80), then separating this
form as an independent species is fully justified (Pidoplichko, 1930;
Kuntze and Scynal, 1933; Libich and Nezabytovskii,* 1934; Migulin,
1938; Reshetnik 1939, 1941; Ognev, 1940, 1947).

ПИТ

Figure 80. Os penis from above and from the side.

A—Spalax polonicus, Meh.; B—S. microphthalmus Gild.;
C—S. arenarius Resh. (by Оэпеу, 1947).

Distribution and geological age. The distribution has been studied only
in very general terms. Perhaps it inhabits a large portion of the right bank
of the Ukraine besides the northernmost parts of the Volynsk Zhitomirsk
and Kiev regions. The western boundary passes from the San River in
the Peremyshlya region along the Dnestra approximately up to Kotovsk
in the line Kotovsk-Pervomaisk, and further south along the South Bug
_ River. It was not found in the Odessa and Nikolaev region west from the
South Bug River within the limits of the present distribution of М. leuco-
don, though fossil and subfossil remains were found around the region

*Reference omitted from the bibliography—(G. Ed.).

280

mentioned. The remains described by Nordmann (1858) from around
Odessa are one of these. In addition, skulls of this species were found in
layers of VI-I ages to A.D. and I-V ages A.D. during excavations of the
ancient city Ol’viya (situated near the village Parutino of the Ochakovsk
region, Nikolaev district) around its periphery (Pidoplichko, 1956; Topa-
chevskii, 1956) as well as in fresh sediments on the right bank of the
Kuchurgan River between the inhabited regions of Veliko-Mizailovka
and Novo-Petrovka of the Frunzenskii region, Odessa district. All this
helps in assuming the presence of the Podolsk mole rat in the region even
now, though its number is very low. There is another species, S. graecus,
living west from Dnestra around the Chernovitskii region. The north
boundary of the area goes through, perhaps, in the line of Peremyshl,
Yavorov, Rovno, Novograd-Volynsk, Kiev (somewhat to the north of the
latter). The eastern boundary of the distribution is the Dnieper River.

Recent; remains of close forms are known starting from the Pleistocene.
It has been found everywhere in subfossil conditions within the limits of
the present-day distribution.

Subspecies. It is represented by only the nominal subspecies, S. polo-
nicus polonicus Mehely, 1909.

5. Spalax graecus Nehring, 1898—Bukovin Mole Rat

Nehrin, 1898b; 228-230, Figure 1-2. istricus Mehely, 1909: 34, 186-194, Tab. II,
Figure 4, Tab. Ш, Figure 6, Tab. XXVIII, Figures 9-16.

Holotype. University in Munich (Federal Republic of Germany);
number of item is not fixed (Nehring, 1898b); place from which the
holotype obtained, not known.

Material investigated. Twenty skulls and skins from the collection of
Yangolenko obtained from Chernovits, Storozhnitskii, and Glybokskii
regions, Chernovits district. Stored in collections of the Zoological Institute
of AN USSR and the Institute of Zoology AN Ukraine SSR.

Diagnosis. With regard to measurements, it is close to the common
mole rat and the Podolsk mole rat (condylobasal length of skull, 49.9—
53.0-55.1 mm; length of upper row of permanent molars, 8.1-8.5-9.0 mm;
length of lower row of permanent molars, 7.7-8.4-8.9 mm). The rostral
section of the skull gradually narrows in an anterior direction and is
wedge-shaped. The width of the nasal bones posteriorly is greater than
the width of each of the premaxillary, and the latter in turn is less or
approximately equal to half of the anterior total width of nasale. However,
the width of the nasal bones anteriorly less than twice exceeds their
posterior width. The temporo-premaxillary and temporo-nasal sutures are
straight or form an angle directed backwards and, rarely, an angle directed
forward. The groove between the nasal bones in the region of the temporo-

281

nasal suture is highly developed; the posterior extremities of the nasale
are sharp and bifurcated like a fork. The length of the nasale bones
exceeds the total length of the temporal and parietal bones. The external
wall of the infraorbital foramen is wide; its least width exceeds the length
of the anterior permanent molar. The auditory opening is small; its
maximum diameter is approximately equal to the length of M’. The
alveolar process of the lower jaw in adult and old individuals considerably
exceeds its articulating one in regard to height. The coronary alveolar
groove is step-like.

Description. The structure of the rostral section of the skull, and the
corresponding width of the nasal and premaxillary bones on the whole,
are similar to the same in the earlier described species—the common mole
rat and the Podolsk mole rat. However, this species differs from the other
two in that the nasale are not constricted in the posterior portion; their
width anteriorly, less than twice exceeds the width posteriorly. In addition,
the groove on the nasal bones in the region of the temporo-nasal suture is
well developed; the posterior end of the nasal is sharp and forms a char-
acteristic fork-like bifurcation which is not present in all the other fossil
and present-day representatives of the genus (Figure 81). It has also to

Figure 81. Spalax graecus Nehr. Natural size.

Legend is the same as in Fig. 50.

282

be noted that the nasale in the common mole rat are, оп the average,
relatively longer, and the rostrum is relatively wider at the base, than in
other species from the genus Spalax. Thus, the relation of the length of
the nasal bones and rostral width to the length of row of permanent
molars is respectively equal to 249.0-273.0-296.0 and 142.0-160.0-172.0.
As in the Podolsk mole rat, the nasal bones anteriorly are relatively wide;
the relation of the total anterior width to the length of row of the per-
manent molar is 98.8—103.0-109.0. Respective measurements of the nasal
bones with regard to the parietal and temporal bones have been given in
the diagnosis. The temporo-premaxillary sutures are directed outward in
relation to the temporo-nasal sutures, and slightly forward, as a result of
which their lines in the expected intersection form an angle with its apex
directed posteriorly. Rarely, the shape of the temporo-premaxillary and
the temporo-nasal sutures is similar to the same in the common mole rat
(straight) or in the Podolsk mole rat (angle with apex directed forward).
On the whole, the sutura praemaxillo-nasofrontalis in the Bukovin mole
rat, because of a considerable development in the grooves, one of which
has already been described, has rather sharper contours than in other
species of the genus. Also, in the Podolsk mole rat the nasal apertures
are relatively high and wide; the length of the row of permanent molars is
respectively equal to 36.4-43.6-53.0 and 91.1-94.4-98.0. The constriction
behind the eyes is expressed in about the same degree as in the common
mole rat. The relation of the width behind the eyes to the length of row of
permanent molars is 90.5-98.8-111.0. The temporo-parietal section is
elongated; the relation of the total length of the temporal and parietal
bones to the length of row of permanent molars is 245.0—-274.0-301.0.
The parietal bones are short and narrow. The relation of their length
and the total width of length of М" МЗ is respectively equal to 101.0—
113.0-125.0 and 51.1-60.1-85.5. In view of the elongation of the
parietal bones in a longitudinal direction, the pentagon formed by
them acquires a corresponding form. The triangular depression on the
temporal bones in the place of displacement of the sagittal ridge is well
developed. The non-bifurcated portion of the sagittal ridge is shorter
than in all the presently known fossil and present-day representatives of
the genus; its length is twice or more less than the length of the nasal
bones. The temporo-parietal and temporo-frontal sutures form a sharp
or straight angle. As in the common mole rat, the upper diastema and
hard palate are, on the average perhaps, relatively longer than in the
Podolsk mole rat. The value of the diastema-tooth index and the ratio
of the length of the hard palate to the length of row of permanent molars
are respectively equal to 217.0-238.0-258.0 and 351.0-378.0-404.0. The
alveolar tubercles in the majority of animals are more strongly developed
than in the common mole rat and the Podolsk mole rat, are closer to the

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anterior edge of the alveolus of МЪ, and situated at a distance which is
less than the length of the first permanent molar, or is approximately
equal to it. The masseter surface is shortened; its length is approximately
equal to the distance between the tubercle of the latter and the suture
between the premaxillary and maxillary bones. However, it differs from
the common mole rat and the Podolsk mole rat in that the anterior tubercle
of the masseter area is massive and sharply defined. The zygomatic arches
are widened anteriorly (Figure 81). Their antero-external edges, as in mole
rats from the giganteus group, are strongly bent down. The malar angle
approaches to 45°. The external wall of the infraorbital foramen is wide.
Its least width considerably exceeds the length of the anterior permanent
molar. The infraorbital foramen itself is low, its length is approximately
equal to the length of the row of permanent molars. The zygomatic arches
are considerably lifted posteriorly in relation to the fossa glenoidea. The
sutures between the malar process of the maxillary bone and the frontal
pass almost in a transverse direction to the former. The hard palate is
wide; its width at the level of the anterior permanent molar exceeds one
and a half and more times the length of M1’. Its posterior edge often
carries markings of the styloid process in the shape of a small diodontus.
The inner ridge of the fossa glenoidea is flattened and the articulating
fossa is wide. The base of the occipital bone is wide and the auditory
bullae are widely separated. The greatest distance between the external
edges of the lateral pharyngeal tubercles considerably exceeds the total
length of the two last permanent molars, in some cases approaching to
the full length of the tooth row. The auditory bullae are wide; the relation
of their width to the length of row of permanent molars is 96.6-102.0—
106.0. The auditory aperture is small; its greatest diameter is approximately
equal to the length of the anterior permanent molar. The occipital portion
of the skull, as in the Podolsk mole rat, on the average perhaps, is lower
than in the common mole rat. The relation of the length of the occipital
bone measured from the upper edge of the foramen magnum to the
maximum width of the occiput is 47.1-50.2-53.2.

The upper incisors are wide; the relation of width to antero-posterior
cross section is 110.3—115.8—133.0. Their anterior surface, as in all repre-
sentatives of the microphthalmus group, is flattened.

М: (length, 2.8—2.9-3.0 mm; width, 2.5-2.6-2.8 mm; relation of width
to length, 83.3-89.4-96.4) with regard to the nature of the structure of
the grinding surface is similar to the same molar in representatives of the
giganteus group. In particular, in young, semi-mature and even partly in
old individuals, the paracone is not fused with the anterior collar, as a
result of which the tooth has two intruding folds in the outer line (Figure
82). The order of closure of the intruding folds into marks, because of
tooth erosion, is the same as in the already described common mole rat

284

and the Podolsk mole rat. The roots are less reduced than in all the
present-day representatives of the genus. The number of roots of this
tooth varies from three to two. In the first case, only the internal and
the antero-external roots are fused incompletely, because of which each
of them has a corresponding independent socket in the alveolus. In the
second case, the fusion is complete; however, the markings of the fusion
of the said roots are always expressed more clearly than on the same
permanent molars of the common mole rat. A fusion of the postero-
external and the internal roots never takes place.

Figure 82. Spalax graecus Nehr. x 10.

Upper row of permanent molars: A to C—adult; D—old individual.

М? (length, 2.2-2.5-2.8 mm; width, 2.5-2.6-2.8 mm; relation of width
to length, 96.3-105.6-122.7) by the structure of its grinding surface is
more akin to the similar molar in the sandy mole rat than the common
mole rat or the Podolsk mole rat. In particular, it differs from S. micro-
phthalmus by less defined foldings of the walls of the outer intruding fold
in the young and semi-mature; and from S. polonicus, by the presence of
anterior and posterior internal tubercles which, in the initial stages of
erosion, are fused with each other. The roots are less reduced than in all
the presently living representatives of the genus. As in the common mole
rat, М? in all cases is characterized by the presence of three independent
roots—a massive internal one and weakly developed anterior and posterior
external ones; moreover, each root has an independent socket in the
alveolus.

However, it differs from S. microphthalmus in that some individuals
have a tendency toward bifurcation of the end of the internal root, as a
result of which the number of cavities in the alveolus may reach up to four.

ee ВИНИТ ВРЕДАЧАВИ

ЕСА

285

MS (length, 1.8—2.0-2.3 mm; width, 2.1-2.2-2.3 mm; relation of width
to length, 100.0-109.0-116.7) is, on the whole perhaps, similar to the
same permanent molar of the common mole rat and the Podolsk mole
rat, possibly differing from the latter in its average smaller relative length.
Thus, the relation of the length of МЗ to the length of the preceding molar
in the Bukovin mole rat is 73.1-79.7-86.4 as against 71.4-84.2-100.0 in
the common mole rat, and 78.2-83.4-100.0 in the Podolsk mole rat. In
addition, it differs from the similar permanent molar in S. microphthalmus,
perhaps, by a rather simpler structure of the grinding surface in the early
and middle stages of wear. The roots, in the majority of cases, also have a
structure similar to that of the same permanent molar of the common
mole rat. They are usually two—a massive postero-internal (the fused
internal one and the posterior external) and the free antero-external. In
such cases, the number of cavities in the alveolus is two. In some cases
there is a tendency toward bifurcation of the end of the postero-internal
root, as a result of which the number of cavities in the alveolus may reach
up to three.

The lower jaw has a short diastema. The latter is, on the average
perhaps, shorter than in all the presently living representatives of the
genus, except for the comparatively primitive giant mole rat. Thus, the
value of the diastema-tooth index in the Bukovin mole rat is 82.8—100.3-—
107.8, that is, approximately equal to the length of the lower row of
permanent molars. As in the Podolsk mole rat, the horizontal branch is,
on the average, relatively lower than in the common mole rat; the relation
of its height at the level of the posterior edge of the alveolus of М, is
108.0-119.4—126.7. The alveolar process in adult and old individuals, with
regard to height, considerably exceeds its articulating one. The height of
the process from the internal side in the said age, as a rule, considerably
exceeds the length of the lower row of permanent molars (97.7-113.3-—
124.4). However, it differs from the sandy mole rat, the common mole
rat, and the Podolsk mole rat, because the alveolar process of S. graecus
is often complex; a tubercle is formed on its posterior surface which, in
some cases, attains the degree of development of a ridge (Figure 81). Such
forms are met in 70 percent of adult and old individuals, and significantly
change the contours of the upper portion of the process. Thus, if in the
sandy mole rat, the common mole rat, and the Podolsk mole rat, the
apex of the alveolar process laterally in a cross section has an appearance
more or less of a semi-circle, then in the Bukovin mole rat, because of
the aforesaid, this does not happen. In fact, the upper section of the
alveolar process of S. graecus looks to be somewhat flattened posteriorly
(Figure 81). In this respect, the given species exhibits characteristics
similar to those of the giant mole rat because in the latter, the alveolar
process of the lower jaw also carries markings of similar structures, though

286

it does not reach the degree of development characteristic of the Bukovin
mole rat. The incisura corono-alveolaris is step-like because of the great
development of the anterior ridge of the alveolar process (Figure 81). Its
anterior edge encroaches considerably on the coronary process. The coro-
nary process is high and wide, with a step-like external surface related to
its being encroached upon by the anterior edge of the corono-alveolar
groove. The corono-articulating groove is correctly cut because of the
approximate coincidence of the height of the coronary process and the
length of the upper edge of the articulating one. The ridge of the coronary-
alveolar groove in the majority of cases is more strongly developed than
the ridge of the coronary-articular one; rarely, the degree of their develop-
ment is approximately similar. Because of a more strongly developed
coronary-alveolar ridge, the fossa contoured by its anterior extremity and
the coronary alveolar ridge is, on the whole, deeper than in the sandy
mole rat, common mole rat, and the Podolsk mole rat. Furthermore, it
differs from the species mentioned above in that the mandibular foramen
is placed low and apart from the edge of the coronary-articulated groove,
at a distance approximately equal to the length of the articulating surface
of the condylus; in any case, it considerably exceeds two-thirds the length
of the latter. With regard to the degree of development of this trait, the
Bukovin mole rat comes nearer to the primitive S. giganteus after all. The
articulating surface of the condylus is widened: its width in the majority
of cases is equal to half the length or even considerably exceeds the length
(relation of width to length is 44.0-52.0-59.0).

The lower incisor is, on the average perhaps, narrower than in the
common mole rat; the relation of the width to the antero-posterior cross
section is 100.0-101.2—103.0.

М, (length, 2.7-2.8—2.9 mm; width, 2.4—2.5-2.7 mm; relation of width
to length, 82.8-92.0-100.0) in the structure of its wearing surface bears a
similarity to the teeth of the sandy mole rat and the common mole rat.
The tendency toward separation of the metaconid and the anterior collar
in the initial stages of tooth erosion and the almost completely reduced
entoconid take it close to the first; the presence of an additional intruding
fold in the outer line in the corresponding stages of wearing takes it close
to the second. The tooth has two roots—a massive, wide posterior and a
weakly developed anterior. Sometimes, the posterior root exhibits a
tendency toward bifurcation.

М, (length, 2.2-2.4-2.6 mm; width, 2.4-2.6-2.7 mm; relation of width
to length, 100.0-108.6-118.2), with regard to the structure of the wearing
surface and the general proportions of the corona, is similar to the same
permanent molar of the common mole rat. However, it differs from the
latter by becoming more complex in the very early stages of wearing (in
very young individuals), because of the presence of an additional intruding

287

fold in the outer line. There are two roots; moreover, both of them either
exhibit a tendency toward bifurcation or are even characterized by forked
ends. In the first instance, the anterior and the posterior cavities of the
alveoli have a well-developed fold, and in the second case, each of the
cavities is divided into two.

; М. (length, 1.9-2.2—2.4 mm; width, 2.2—-2.3-2.5 mm; relation of width
to length, 95.6-103.7-115.8), with regard to the general characteristics of
the wearing surface, proportions of the corona, and the nature of the
root structure, does not differ from the same permanent molar in the
common mole rat (Figure 83).

Figure 83. Spalax graecus Nehr., lower row of permanent
molars. x10.

A to C—adult; D—old individual.

Comparison. A detailed comparison of the Bukovin mole rat was made
above.

Measurements. Condylobasal length of skull, 49.9-53.0-55.1 mm; basal
length of skull, 46.1-49.3-51.5 mm; length of nasal bones, 21.2—23.5-
25.3 mm; total length of parietal and temporal bones, 22.1-23.0-24.4 mm;
length of parietal bones, 8.7-9.7-11.3 mm; length of upper diastema,
19.0-20.4—21.7 mm; length of hard palate, 29.9-32.5-34.8 mm; length of
upper row of permanent molars, 8.1-8.5-9.0 mm; width of nasal aperture,
7.8—8.1-8.3 mm; incisorial width, 8.4-9.3-10.3 mm; width of nasal bones
anteriorly, 8.6-8.9-9.2 mm; rostral width, 12.1-13.7-14.8 mm; width
behind the eyes, 7.3-8.5-9.6 mm; width of two parietale, 3.3-5.2-7.7 mm;
width of parietal bone up to lambdoid ridge, 4.8-5.3-6.1 mm; malar
width, 39.8—42.7-45.5 mm; width of occiput, 36.4-37.7-39.5 mm; length
of auditory bullae, 12.1-12.9-13.9 mm; width of auditory bullae, 8.5-
8.7-9.2 mm; width of upper incisor, 3.0-3.2-3.6 mm; antero-posterior

288

cross section of upper incisor, 2.5-2.8-3.1 mm; height of nasal opening,
3.1-3.7-4.3 mm; condylar length of lower jaw, 33.9-35.2-39.1 mm; angular
length of lower jaw, 32.6-35.5-41.4 mm; length of lower diastema, 7.2—
8.4-9.1 mm; length of lower row of permanent molar, 7.7-8.4—8.9 mm;
height of horizontal branch at the level of the posterior edge of the alveolus
of M, externally, 9.4-10.1-10.9 mm; thickness of horizontal branch at
the level of Mz, 4.8-5.4-6.1 mm; height of alveolar process internally, 8.5—
9.5-10.7 mm; width of lower incisor, 3.1-3.4-3.9 mm; antero-posterior
cross section of lower incisors, 3.0-3.4—3.8 mm.

Note. From the above description of the Bukovin mole rat and its
comparison with fossil and presently living representatives of the genus,
it is very clear that in the given case we are dealing with the least specialized
species from the microphthalmus group from the viewpoint of a trophic
as well as a burrowing capacity. This group preserved, along with highly
specialized traits characteristic for the group as a whole, some primitive
traits taking it closer to the most primitive representative of the giganteus
group—the giant mole rat, and from the number of species of the micro-
phthalmus group—the Pliocene S. minor. Such traits in the structure of
the skull, the lower jaw, and the permanent molars of the Bukovin mole
rat are: structural characteristics of the alveolar tubercles and the zygo-
matic; a highly developed anterior ridge in the masseter area; a shortened
lower diastema; a relatively low horizontal branch of the lower jaw; a
typical structure of the upper end of the alveolar process; a lower position
of the mandibular foramen, possibly relatively narrower lower incisors;
and also complex upper and, to a certain extent, lower anterior permanent
molars, the roots of which are less reduced than in all the presently living
representatives of the genus Spalax. Furthermore, individual specimens
of Bukovin mole rats rarely preserve markings of the for. epicondyloideum
which actually push it toward the boundary between Microspalax and
Spalax. In the rest of the traits, the species is characterized by all traits
inherent in the highly specialized mole rats from the genus Spalax, and
foremost from the species of the highly developed group microphthalmus.
The foregoing helps in taking it to be a species which has, to a considerable
degree, preserved the characteristics original for the group in toto.

The species was first described by Nehring (1898b). In place of its
terra typica. Nehring supposedly indicated only the region around Athens
because the etiquette of the holotype did not offer a possibility to exactly
fix the place of its find. Afterwards Mehely (1909) doubted the possibility
of finding this species in Greece because all the rest of the finds were
discovered exclusively in the Karpate region of the Pricarpate regions of
the Chernovits district of Ukraine SSR (Bukovina), and the adjacent
regions of Rumania. However, in the work of further researchers up to
Miller (1912) the findings of Nehring (1898b) and especially of Mehely

289

(1909) were forgotten, and the presence of the species around Athens was
taken to be an established fact not needing additional proof. As a result,
Greece and Bulgaria are included in the present-day area of the species:
true, sometimes with a footnote that the species is presently extinct there
(Ognev, 1947). By the way, it could be confirmed adequately that during
the determination of the terra typica of the Bukovin mole rat as well as
the M. kirgisorum, a great misunderstanding with regard to etiquetie
prevailed. Hence, we feel the terra typica of the species may be taken as
the region around the city of Chernotisi from where Mehely (1909)
described two skulls belonging to the given species which could be rightly
taken as paratypes of the species. At present, the habitat of this species
within Soviet Bukovina is restricted to the hilly landscape on the right
bank of the Prut River (Yangolenko, 1959). The mole rat of this species
obtained from adjacent territorial regions in Rumania (around Borshi
and Bistritsi, Northeastern Klusha) were separated by Mehely (1909) as
an independent species—S. istricus Mehely. However, a comparison of
the skull of Rumanian mole rats with a series of skulls obtained from the
region of Soviet Bukovina makes it possible to determine the presence of
considerable transgression in respect to all the traits which Mehely took
to be specific for the species (structural characteristics of the temporo-
nasal and temporo-premaxillary sutures, the corresponding length of the
premaxillary and nasal bones, the degree of reduction of roots on the
permanent molars). On this basis, a separation of it as a separate species,
in our opinion, does not have enough basis. In addition, it is possible
that these differences will be taken into further consideration in the
average of the serial data which serves as a basis for the preservation of
this nomenclature as a subspecies. The presence of an independent sub-
species in the vicinity of the indicated regions of Rumania is quite possible
theoretically because the main ridge of the Karpate hills could play the
role of a geographical fence between the Rumanian and Bukovin forms.
However, at present, this question remains unsolved because we do not
have.a series of skulls for the Rumanian S. graecus.

Distribution and geological age. In Soviet Bukovina, spread up on the
right bank of the Prut River, occupying the northwestern portion of the
near hills and hilly zones. It has been found around the village Zavoloki,
Mikhalcha, Kamenka, Chagor, Valya Kuzmina of Chernovitsk region,
and also in a number of centers of the Storozhintsk and Glybovskii
regions; around the adjacent regions of Rumania near Borsh and Bistritsi
(northeast of Kluzha). Recent; subfossil remains of the Holocene period
have been found in and around the present regions of its spread near
Turda.

Subspecies. Geographical variability has not been studied; however,
it is quite possible to have two subspecies.

19

290

1. S.g. graecus Nehring, 1898—Bukovin subspecies; distributed around
Soviet Bukovina along the northeastern slant of Karpate and their foothills.

2. S. g. istricus Mehely, 1909—Rumanian subspecies; differs from the
nominal form, perhaps, by a lesser degree of reduction of roots on the
permanent molar. It is distributed along the southwestern slant of the
Karpate hills within the limits of Rumania. S. g. antiquus Mehely, 1909,
from the Holocene sediments of Rumania (Turda) is absolutely similar to
this form.

6. Spalax minor W. Topachevskii, 1959—Small Mole Rat or
the Nogaiskii Mole Rat

Topachevskii, 1959: 1263-1266, Figures 1, 2, 7, 8. microphthalmus minor Topachevskii,
1957a: 144-145.

Holotype. Institute of Zoology AN Ukraine SSR, No. 27-92; lower
jaw (mandibula sin.) without the coronary and alveolar processes; from
the permanent molars, only the complete line of alveoli has been preserved ;
Late Pliocene Nogaisk.

Paratypes. Skull is without temporal and occipital sections and the
zygomatic arches, No. 27-980; lower jaw with a fully preserved row of
permanent molars, without coronary and upper portion of the alveolar
processes, No. 27-981; lower jaw without teeth, with disturbed coronary
and alveolar processes, No. 27-215. All the remains are from Upper >
Pliocene sediments, hidden near the city Nogaisk, Primorsk region,
Zaporozh’e district, and are stored in the collections of the Institute of
Zoology AN Ukraine SSR.

Material investigated. The lower jaws at different degrees of preserva-
tion and their pieces—4 items; isolated teeth—incisors of the upper jaw
—10, M,—13;M?—7; M3—5; lower incisors—20; M,—12; M,—7; Ms—4.
All these remains come from the Upper Pliocene sediments of Nogaisk. In
addition, the author had individual broken pieces of the lower jaw, and a
small series of teeth from a number of places of finds of the Late Pliocene
in the region of Odessa and Kryma.

Diagnosis. It is the smallest of all the presently known representatives
of the genus. The skull is generally similar to the skull of the Bukovin
mole rat. It differs by narrowed parietal bones, the total length of which
is less than length of the upper line of permanent molars, and also by,
on the average, a shortened upper diastema, a hard palate, row of per-
manent molars, and a reduced width behind the eyes. The lower jaw has
a high diastema section, elongated and narrowed articulating surfaces
for the condylus (width is less than half its length or is approximately
equal), and a step-like corono-alveolar groove. In addition, the upper and
lower incisors, and the anterior permanent molars are, on the average,

291

relatively narrower than in all the presently living representatives of the
genus.

Description. The rostral section of the skull is similar to the same as
in the common mole rat and is wedge-shaped (its width at the level of the
anterior edges of the infraorbital foramen exceeds the width at the center.
The total length of the nasal bones posteriorly exceeds the length of the
premaxillary, and the latter, in turn, is approximately equal to half the
anterior total width of the nasale. The nasal bones are greatly narrowed
in the posterior section; total width of the nasale anteriorly, approx-
imately twice exceeds the width posteriorly. The groove in the region of
the temporo-nasal suture is faintly marked; however, the posterior ends
of the nasal bones are slightly sharpened and exhibit a tendency toward
forming a fork-like bifurcation, typical as was shown above, of the
presently living Bukovin mole rat (Figure 84). The nasal bones are elon-
gated; their length slightly exceeds the total length of the temporal and
parietal bones. The temporo-premaxillary and temporo-nasal sutures are
straight; however, the posterior ends of the nasale are slightly curved

Figure 84. Spalax minor W. Top. x 1.6. Late Pliocene of
South of Ukraine, Nogaisk town, Zaporozh’e district.

Legend is the same as in Figure 50.
19A

292

back in relation to the former. The constriction behind the eyes is expressed
more clearly than in the common mole rat. The relation of the width
behind the eyes to the length of skull from nasion to apex of the lambdoid
is 16.0! as against 16.4-19.4-22.4 in 5. microphthalmus. The parietal bones
are narrow; the relation of their total width to the length of row of per-
manent molars is 86.1 as against 80.2-140.0-179.0 in adult and old S.
microphthalmus. It has also to be taken into account during this that the
dental row in S. minor is shortened and, as a result, the value of the given
trait in it is dependent on it. The parietal bones form a pentagon drawn
out in a longitudinal direction like a five-angled star. The triangular
depression on the temporal bones in the place of displacement of the
sagittal ridge is almost not expressed. The temporo-parietal and the
temporo-frontal sutures form a blunt angle. The upper diastema and the
hard palate are short; the relation of their lengths to the length of the
skull from nasion to apex of the lambdoid ridge is 42.4 and 67.8 as against
respectively 43.1-48.1-52.2, and 68.1-75.6-81.3 in the common mole rat.
The masseter area is shortened; its maximum width is equal to the distance
from the anterior tubercle of the latter up to the suture between the
premaxillary and maxillary bones. The anterior ridge of the masseter area
is weakly developed. The alveolar tubercles are absent. The hard palate
at the level of the anterior permanent molars is narrowed; its width only
slightly exceeds the length of M1. The upper row of permanent molars
is short (16.4 as against 18.4-20.2-22.7 in 5. microphthalmus). The zygo-
matic arches, the posterior portion of the base of the skull, and the frontal
and occipital sections have not been preserved, because of which the
comparison of their structure with similar organs in the Bukovin mole
rat is out of question.

The upper incisors are, on the average, narrower than in the common
mole rat; the relation of the width to the antero-posterior cross section is
100.0-104.2-108.6 as against 104.4-112.0-120.8. Their anterior surface is
flattened.

М! (length, 2.0-2.3-2.5 mm; width, 1.7-1.9-2.1 mm; relation of width
to length, 75.0-84.6-95.0) is smaller in regard to absolute measurements
than the similar permanent molar in all presently living representatives of
the genus. Furthermore, it is, on the average, comparatively narrower. A
great similarity is observed between the permanent molars of mole rats
from the giganteus groups in regard to the structure of the grinding face

1 Here and afterward the indices of the skull differ from the earlier described
species in being measured against the length of the skull from nasion to apex of the
lambdoid ridge, and not to the length of the upper row of permanent molars, because
the latter in the Nogaisk mole rat in comparison with presently living species is short-
ened and, as a result, even the values of the corresponding relations, if they are to be
brought to this number, will be dependent to a considerable extent. In cases where the
index is taken from the length of M?—M2, a corresponding note is given in the text.

293

in young, semi-mature, and partly in old animals, and among representa-
tives of the microphthalmus with the Bukovin mole rat. This similarity
is due mainly to the presence of a paracone that is not fused with the
anterior collar, as a result of which the tooth is characterized by two intrud-
ing folds in the outer line (Figure 85). The types of structures character-

Figure 85. Spalax minor W. Top., upper permanent molars. x 10.

istic of the common mole rat (paracone fused with the anterior collar
but separated from the neck, joining the protocone with the hypocone;
one intruding fold in the outer line, the protocone and the hypocone
fused) and the Podolsk mole rat (protocone and hypocone isolated) are
rarely seen. It has also to be noted that the closure of the intruding fold
into a mark in the Nogaisk mole rat takes place, perhaps, in rather later
stages of tooth erosion than in all the present-day and fossil quaternary
species of the genus. It differs from all the presently living representatives

294

of the genus in that the metacone and posterior collar express, perhaps,
a greater tendency for separation; moreover, in individual cases the pos-
terior external tubercle may even have the form of an independent fold,
as a result of which the tooth will be characterized by the presence of
three intruding folds in the outer line. The grinding surface of the said
teeth from the moment of the closure of the intruding folds into marks
assumes a form very similar to that on the same permanent molars in
recent representatives of the genus, because of which the differentiating
characteristics at a given stage of wearing (in part, of adult and old
animals) will reduce to only smaller absolute measurements and some-
what other proportions in the structure of the corona. The number of
roots in the majority of given cases, as in Bukovin mole rats, does not
exceed two—the massive antero-internal (the fused internal and the
external), and a comparatively weakly developed posterior external. In
some animals, the antero-external and the internal roots are not fused,
as a result of which the tooth is characterized by the presence of three
roots. On the whole the roots on the anterior permanent molars of the
Nogaisk mole rat are more reduced than in the common mole rat which,
to a certain extent, puts it closer to S. graecus. -

М? (length, 1.8-2.0-2.2 mm; width, 1.8-2.0-2.2 mm; relation of width
to Jength, 95.0-100.0-104.8), on the average, is smaller and perhaps
relatively narrower than in the present-day S. microphthalmus. The struc-
ture of the wearing surface is similar to that of the recent common mole
rat. However, the degree of reduction of roots is generally expressed more
strongly. This varies in the Nogaisk mole rat from one to two as against
three in the common mole rat.

МЗ (length, 1.6-1.7-1.9 mm; width, 1.7-1.8-1.9 mm; relation of width
to length, 95.0-106.8-112.5), in regard to the character of the structure of
the wearing surface, and general proportions of the crown, is, on the
whole, similar to the same molar in the common mole rat, differing
only in the average lesser absolute measurements. However, as in the
preceding molar, the degree of reduction of roots is expressed more
strongly than in S. microphthalmus. This tooth in the Nogaisk mole
rat, in the majority of cases, is characterized by the presence of only one
root. In present-day common mole rats, there are usually two roots.

The lower jaw is, on the whole, similar to the lower jaw of the presently
living S. microphthalmus, differing by a rather high diastema-section and
an outgoing branch. Thus, the values of the height of the jaw along the
center of the diastema and the outgoing branch to the condylar length,
respectively, are equal to 16.7, 17.8, 18.1 and 36.5 as against 13.0-14.3-
16.2 and 30.7-33.4-35.5 in 5. microphthalmus. In addition, the horizontal
branch of the lower jaw of the Nogaisk mole rat is perhaps thicker at the
level of М»; the relation of its thickness to the condylar length is 15.7,

295

16.3, 17.4 as against 13.4-14.3-15.8. The coronary alveolar groove is step-
like because of the greater development of the alveolar ridge in the alveolar
process than in the common mole rat. With regard to the development of
this trait, the Nogaisk mole rat is closer to the present-day S. graecus than
to the rest of the representatives of the microphthalmus group. Parti-
cularly clear differences between S. minor and the common mole rat are
observed in the structure of the articulating surface of the condylus. The
latter in the Nogaisk mole rat is, on the average, relatively longer and
narrower than in S. microphthalmus. This trait is well seen during a com-
parison of the values of the relation of width of the articulating surface
to its length, which in S. minor is respectively equal to 47.8, 48.1, 49.1, 52.3
as against 50.0-57.0-66.7 in S. microphthalmus. The said peculiarity of
the structure of the lower jaw, to some extent, draws the Nogaisk mole
rat nearer to the recent S. arenarius.

The lower incisor is, on the average, relatively narrower than in all the
presently known representatives of the genus, except for the giant mole
rat. The relation of the width to the antero-posterior cross section is 90.0—
97.7—-104.1 in the Nogaisk mole rat and 88.9, 92.3, 96.0 and 96.4 in Krym
mole rats. However, it differs from the giant mole rat in that the anterior
surface of the incisor is flattened and not convex. Furthermore, the
incisors of the Nogaisk mole rat differ from the same in S. giganteus by
considerably smaller absolute measurements.

М, (length, 1.9-2.2-2.5 mm; width, 1.5-1.9-2.0 mm; relation of width
to length, 78.3-84.1-90.9), on the average, is smaller and narrower than
the same permanent molar in all the presently known recent representatives
of the genus. In the initial stages of wearing (in very young individuals),
there is quite a similarity in the structure of the wearing surface with the
same permanent molar of the sandy mole rat and the Bukovin mole rat,
because the metaconid and the anterior collar are not fused (Figure 86).
However and further (in young, semi-mature, and partly in old indivi-
duals), the masticatory surface of the tooth assumes a form which is
characteristic of the common mole rat and the Podolsk mole rat. It differs
from the first in that the markings of an additional intruding fold in the
outer line (observed by us only in one instance, Figure 86) are rarely
observed on the anterior permanent molars of the Nogaisk mole rat. As
far as the Podolsk mole rat is concerned, the said teeth in it are, on the
average, considerably wider than in the common mole rat, not to speak
of the Nogaisk mole rat. The protoconid and the hypoconid in the majority
of cases are fused. The entoconid is developed to approximately the same
degree as that in the common mole rat and the Podolsk mole rat. Rarely,
this tubercle fuses with the posterior collar forming a posterior mark
characteristic, as was shown above, of the same permanent molar in
representatives of the genus Microspalax. The structure of the root on

296

the whole, is similar to the same on the anterior lower molars of the
common mole rat.

Mp

Figure 86. Spalax minor У. Top., lower permanent molars. x 10.

М, (length, 2.1-2.2-2.3 mm; width, 1.9-2.1-2.3 mm; relation of width
to length, 82.6-96.8—104.8), with regard to the general characteristics of
the wearing surface and the structure of the roots on the whole, is similar
to the same permanent molar of the common mole rat and the Podolsk
mole rat. It differs from all the presently living species of the genus by
lesser absolute measurements and by a narrowed crown.

М. (length, 1.8-1.9-2.0 mm; width 1.8-1.9-2.1 mm; relation of width
to length, 94.7-102.7-105.1) is similar to the same permanent molars of
the present-day species from the microphthalmus group.

Comparison. Characteristics of similarity and difference between the
Nogaisk and the common mole rat have been looked into above. While
summarizing the foregoing, it has to be underlined that S. minor differs
from all the recent representatives of the microphthalmus group by a long
and narrow articulating surface of the condylus of the lower jaw, and also
by, on the average, relatively narrower upper and lower incisors and

297

permanent molars, primarily, М!-М2. Furthermore, it differs from 5.
polonicus as follows:

1. Elongated nasal bones, the length of which exceeds the total length
of the temporal and parietal bones (in the Podolsk mole rat, the relation-
ship is reversed).

2. Shape of the temporo-nasal and temporo-premaxillary sutures
(almost a straight line in Nogaisk mole rat, with an angle whose apex is
directed forward in the Podolsk mole rat).

3. A protocone and hypocone on M}, fused in the majority of cases
in the early and middle stages of wear, and also the paracone which is
not fused at a given stage of wear with the anterior collar (in Podolsk
mole rat, the first are always isolated and the second ones are fused).

4. A step-like form in the corono-alveolar groove (faintly stepped in
5. polonicus).

Finally, besides the above-mentioned characteristics in the structure
of the articulating process of the lower jaw and the permanent molars, it
differs markedly from the Bukovin mole rat by a weakly developed groove
on the nasal bones in the region of the temporo-nasal sutures and by the
triangular depression on the temporal bones in lieu of the displacement
of the sagittal ridge.

Measurements. Length of nasal bones, 22.9 mm; total length of parietal
and temporal bones, 21.7 mm; length of parietal bones, 10.9 mm; length
of upper diastema, 18.6 mm; length of hard palate, 29.7 mm; length of
upper row of permanent molars, 7.2 mm; width of nasal aperture, 7.9 mm;
incisorial width, 8.3 mm; width of nasal bones anteriorly, 8.3 mm; rostral
width, 12.0 mm; width behind the eyes, 7.0 mm; total length of parietale,
7.7 mm; width of parietal bones up to the lambdoid ridge, 4.0 mm; width
of upper incisor, 2.3—2.6-2.9 mm; antero-posterior cross section of the
upper incisor, 2.2—2.4—2.8 mm; height of nasal aperture, 4.3 mm; condylar
length of lower jaw, 26.9, 29.9, 31.2 mm; length of lower diastema, 7.0,
8.1, 8.3 mm; length of lower row of permanent molars, 6.8—7.0-7.2 mm;
height of horizontal branch at the level of the posterior edge of the alveolus
of M, externally, 7.1, 7.8, 8.8, 8.8 mm; thickness of horizontal branch at
the edge of the М,, 4.2-4.6-5.2 mm; width of lower incisor, 2.3-2.6-
3.0 mm; antero-posterior cross section of lower incisor, 2.3-2.6-2.9 mm.

Note. From the description given above about the mole rat from
Nogaisk, and comparing it with fossil and presently living species of the
genus Spalax, there is no doubt that in the given case we are dealing with
an already completely formed representative of a most highly specialized
group within the limits of the microphthalmus group which has preserved
in its structure a number of primitive traits that place this species closer
to the last specialized representatives of the group—the present-day S.
graecus, and in regard to some traits, even closer to the species from the

298

giganteus group—the giant mole rat and the sandy mole rat. However,
it has to be underlined that the Nogaisk mole rat, in regard to a number
of structural characteristics of the skull, the lower jaw, and the permanent
molars, stands closer to the common mole rat than to the Bukovin mole
rat. This, first of all, concerns the degree of reduction of roots on the
permanent molars which in S. minor is expressed in a greater manner
than in S. graecus. Thus, taking into consideration the highly expressed
trophic adaptability of the Nogaisk mole rat as compared to the Bukovin
mole rat, the comparatively early separation of these took place, perhaps,
somewhere toward the end of the Late Pliocene. In addition to this, with
regard to the degree of development of adaptations to burrowing (relative
width of the incisors) the Late Pliocene Nogaisk 5. minor sharply differs
from all the presently living representatives of the genus except for S.
giganteus which, perhaps, indicates a lower degree of specialization in
the species in this regard. Relative to the development of this trait, the
Nogaisk mole rat takes up a middle position between representatives of
the primitive genus Microspalax and the highly specialized Spalax.

It has also to be underlined that the considerable similarity of the
Nogaisk mole rat with present-day S. microphthalmus and, to a lesser
extent, with S. polonicus, allows one to look to it with a known degree of
probability as a form close to the ancestral with regard to the said species
separation which, as has already been mentioned, took place perhaps only
in the Anthropogene.

The Nogaisk mole rat is the most ancient of the presently known
species of the genus Spalax. In sediments more ancient than the Nogaisk
sediments (Villapransk and below), mole rats have been represented by
remains of representatives of the genera Microspalax and Prospalax. Thus,
the type of structure of the skull, lower jaw incisors, and permanent molars
inherent in all fossil and presently living Spalax completely took shape,
perhaps, in eastern Europe only at the end of the Pliocene epoch. The
remains of closer forms, considering the past and present distribution of
the genus, should be found in the corresponding sediments of western
Europe also (Rumania, Hungary, Czechoslovakia, Poland). In this regard,
Kretzoi’s report (1941) about finding in the Upper Pliocene sediments in
Hungary (place of find, Betfiya near Nagivard, Inner Karpate) the incisors
of a mole rat of the Spalax species, which did not have on the anterior
border the three additional ridges of enamel characteristic of the European
Pliocenic Microspalax and representatives of the genus Prospalax, is signi-
ficant. Unfortunately, the foregoing author does not give the measurements
of width and the antero-posterior cross section of the incisors. Hence, there
is insufficient basis for assuming that this mole rat from Betfiya belonged
to a species closer to S. minor and not to a form from the subgenus Meso-
spalax. It has also to be noted that Kretzoi (1956) gives it the name S.

299

advenus Kretzoi. Remains of this species orginate from the Upper Pliocene
sediments of Hungary, possibly stratigraphically identical or at least close
to the Nogaisk mole rat. Unfortunately, in the absence of at least a short
description, we cannot compare S. minor with S. advenus.

Distribution and geological age. End of Late Pliocene and, perhaps,
early fossils around the Black Sea and the Azov Sea of USSR, including
Krym. Besides Nogaisk, remains of this species have been found in the
Upper Pliocene sediments of mysa Tarkhankut in Krym (near the village
Chernomorskoe) and on Tamani (place of find, Tsimbal). Perhaps some
portion of the remains from the lower fourth of the sediments in the village
Tikhonovka of the Novo-Vasilevsk region, Zaporozh’e district, could be
related to this species. Very scanty remains of the close, if not identical
form are known at the present time from the sediments of the right bank
estuary of Kuyal’nitsk around the city of Odessa (Zhevakhova hills, terri-
tory of Kuyal’nitsk hill station), and from down under the upper layer of
the ancient alluvial soil, hidden in the left bank of the estuary of Khadzhi-
beisk near the village Avgustovka, Odessa region, Odessa district (Topa-
chevskii, 1965). In the first case, they are accompanied by fauna more
ancient than that of Nogaisk which has been separated by A. I. Shevchenko
(1965) in the so-called Odessa Late Pliocene complex. In the second case,
the remains of the mole rat having a shape very close to the Nogaisk’s
were found in adjacent sediments.

Special attention should be given to the discovery of this species in
Krym, giving documentary evidence of the presence of mole rats in the
territory of the peninsula in the Late Pliocene. The latter is more interest-
ing because among the Pleistocene and Holocene (including present-day
forms), fauna of Krym, mole rats, perhaps, are absent. Unfortunately,
the only one unconfirmed report on the habitation of the fossil remains
of Spalax of the Pleistocene period (Merezhkovskii, 1880) was not con-
firmed by the research of A. A. Byalinitskii-Birulya (1930), and I. M.
Gromov (1961), who carried out research on masses of paleontological
material from the Pleistocene and Holocene of Krym. Thus, the dis-
appearance, or at least a considerable reduction, in the number of mole
rats in Krym through the Anthropogene makes us look at it perhaps as a
secondary event, the reason for which is most probably hidden in the
significant changes of a paleogeographical nature which took place in
Krym at the end of the Early Anthropogene and in the beginning of the
Pleistocene. The reasons bringing about these changes and the nature of
the latter are not clear even up to the present time.

300

Spalax Species
Spalax aff. microphthalmus Topachevskii, 1965: 139.

Material investigated. Isolated teeth: M!—1 only; M3—1 only; lower
incisors—7; M,—3. All the remains originate from the lower Anthropogene
sediments excavated near the village Tikhonovka of the Novo-Vasilevsk
region, Zaporozh’e district.

Description and comparison. The author has already reported in earlier
works the fact of the discovery of two types of mole rats among the early
Anthropogene fauna of Tikhonovka (Topachevskii, 1965). A portion of
the remains from this place of discovery (mainly, isolated incisors and
permanent molars) appeared to be absolutely identical to those of S.
minor and, in all probability, should be attributed to this species. In
addition, it was possible to separate these series of teeth sharply differing
from the similar remains of the Nogaisk mole rat, by large general measure-
ments, somewhat different proportions in the structure of the crown of
the permanent molars, and perhaps, by a less expressed degree of reduction
in the roots of the latter. This form was earlier placed close to S. micro-
phthalmus by us. However, during a detailed study of the material, we
had to retract this because it was possible to note a number of significant
differences in the Tikhonovka large mole rat from this species. The traits
taken together indicate, first of all, that in the given case we are dealing
with a less specialized form than the recent species which, perhaps, takes
an intermediate place in the evolutionary line between the Nogaisk mole
rat and the presently living species from the microphthalmus group.
Because these finds are interesting from the point of view of understanding
history of stabilization in the group as a whole, we take the liberty of
putting forward a short description of the remains, though the very scanty
material available with the author does not allow describing the Tikho-
novka mole rat as an independent taxon at the species or subspecies level.

М: (length, 2.5 mm; width, 2.3 mm; relation of width to length,
92.0 mm) is larger and mainly, relatively wider than the same permanent
molar in the earlier described Late Pliocene Nogaisk mole rat, and ap-
proaches in regard to development of the said traits to presently living
representatives of the genus. There were no differences in the structure of
the grinding surface between S. minor and present-day species of Spalax
because both belong to aged individuals (the anterior fold or the inner
portion of the only fold of the external line closed into a mark), and the
configuration of the masticatory surface of the permanent molar in all
mole rats of this genus, as has already been said, at these stages of advanced
age has a very similar shape. The structure of the roots is basically similar
to the common mole rat. The tooth has two roots—a massive antero-
internal and a weakly developed postero-external.

301

M3 (length, 1.9 mm; width, 1.9 mm; relation of width to length, 100.0),
with regard to general features of the grinding surface, proportions of the
crown, and absolute measurements, is similar to the same permanent molar
of the Nogaisk and the common mole rat. However, the presence of two
roots sharply differentiates it from the former.

The lower incisors are larger than in the Nogaisk mole rat, and ap-
proach to the same in S. microphthalmus in regard to absolute measure-
ments (width of incisor, 3.2-3.4-3.8 mm; antero-posterior cross section,
3.1-3.3-3.4-4.0). However, they are, on an average, relatively narrower
than in the common mole rat (relation of width to antero-posterior cross
section, 94.1-98.1-103.2), which brings the Tikhonovka mole rat closer
to S. minor and the giant mole rat.

М, (length, 2.3-2.4-2.5 mm; width, 2.2-2.2-2.2 mm; relation of width
to length, 88.0-91.7-95.6), on the average, is apparently larger and rela-
tively wider than in the Nogaisk mole rat, resembling, because of this,
the same molars in the recent representatives of the genus. With regard to
the general characteristics of the grinding surface, it exhibits many char-
acteristics that are similar to the same permanent molars of the Nogaisk
mole rat because, in the initial stages of wearing, the metaconid and
anterior collar are completely separated (Figure 87). The said teeth could
also belong to S. arenarius though
in the semi-mature animals the
antero-internal tubercle and the
anterior collar fuse together. In the
sandy mole rat, isolation of the
metaconid and the anterior collar
is preserved even in semi-mature
animals.

: 2 Figure 87. Spalax sp. x10. Early

Thus, on the basis of the Tik- Anthropogene, South of Ukraine,

honovka Early Anthropogene mole Village Tikhonovka, Zaporozh’e
rat, we come across a type of region.

structure which has considerably
preserved the style of the Late Pliocene forms and which, at the same
time, is highly specialized like the presently living species from the micro-
phthalmus group. The presence of less reduced roots on the permanent
molars, as compared to S. minor, greatly reduces the obstacles in the way
for seeing this species as an ancestor in relation to the common mole rat
and to the species close to it.

Distribution and geological age. Early Anthropogene, the Azov Sea
region in the Ukraine SSR.

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INDEX OF LATIN NAMES!

advenus, Spalax 299

aegyptiacus, Microspalax 116*, 186

—-—ehrenbergi 187

aegyptiacus, Spalax 177

Alilepus 126

Allophajomys 127, 130

anatolicus, Mesospalax 116*

anatolicus, Microspalax leucodon 220

—-—nehringi 221

— Spalax monticola 212

Anomalomyinae 112, 118

Anomalomys gaudryi 113*

Anotis 232

antiqua, Ochotona 126

antiquus, Macrospalax 116

antiquus, Spalax graecus 290

arancae, Lagurodon 127

arenarius, Macrospalax 117*

—Spalax 5,7*, 14*,31*, 68, 70, 82, 108*,
109, 119*, 125-126, 131*, 133, 235-237,
241, 244-247, 248, 251, 252, 254, 255,
256, 257, 265, 266, 267, 279*, 294-295,
301

—arenarius, Spalax 255

—Spalax arenarius 256

arenarius Spalax microphthalmus 248

——polonicus 248

— —2етш 248

armeniacus, Mesospalax 116%

armeniacus, Microspalax leucodon 221

—-—-nehringi 221

—Spalax monticola 212

arvalis, Microtus 62*

Arvicola 130

Arvicolidae 3

Aspalax 232

auratus, Mesocricetus 48

Baranomys 103, 127, 128
Bathyergidae 3, 4

berytensis, Microspalax 187

—Spalax 177

captorum, Microspalax leucodon 221

cilicicus, Mesospalax 116%

cilicicus, Microspalax leucodon 221

cilicicus,—nehringi 215*, 221, 222

cilicicus, Spalax monticola 212

compositodontus, Microspalax 15*, 67,
71, 103, 104*, 119*, 120, 121, 128, 131*,
132, 159, 174, 176, 184, 188, 189*, 190,
191, 198-199, 210, 219

corybantium, Microspalax leucodon

—-—nehringi 221

Cricetidae 4, 44, 113, 115*

Cseria 128, 129

—egracilis 129

Cylindrodontidae 10, 53

221

diluvii, Macrospalax 117%

diluvii, Spalax 269, 278

Dipodidae 3, 14, 113, 115*

dolbrogeae, Mesospalax 116*

dolbrogeae, Microspalax 230

— —Чеисо4оп 231

—Spalax 222

Dolomys 128, 129

—aff. milleri 126

—hungaricus. 127, 129

—kowalskii 129

—milleri 127, 129

—ucrainicus 129

ehrenbergi aegyptiacus, Microspalax 188

—ehrenbergi, Microspalax 187,

—kirgisorum,—187

—Microspalax 5, 38*, 40*, 67-71, 80,
103, 104*, 105, 116*, 117*, 119*, 121-
123, 1311, 132. 153) 158: 163. 173: 4.
177, 177, 180*, 181*, 183*, 184—187,

1 Bold face numbers denote pages on which a description is given; an asterisk refers
to pages with diagrams; italics indicates synonyms.

304

190-193, 196, 197, 203, 206-210, 214,

219
ehrenbergi, Microspalax ehrenbergi
—Spalax 4, 5, 70, 170, 175, 177
Ellobii 277
Eolagurus 130
Eupetauridae 4
exilis, Villanyia

188

127

feijervaryi, Mimomys 127
fritschi, Microspalax 6, 116*, 187
fritschi, Spalax 5

Fritschi, Spalax 177

Geomyidae 3

Germanomys 103, 128

(giganteus), group 107, 108, 109, 235,
259, 260-264, 283, 288, 292, 298

giganteus, Macrospalax 116*, 117*

—Spalax 5, 11*, 58, 68-70, 108*, 108,
118, 119, 123-125, 131*, 133, 186, 234,
235, 237, 240*, 243*, 244, 247-250, 254,
255, 267, 286, 295, 298

—uralensis, Spalax 248

Glis zemni 269, 278

gracilis, Cseria 129

graecus, Macrospalax 116*, 117*

—Spalax 5, 6, 68, 70, 85, 108*, 111,
118, 119*, 126, 131*, 133, 232, 235, 236,
243, 257, 260, 266, 267, 276, 280, 281*,
284*, 287*, 289, 294, 295, 297

—antiquus, Spalax 290

—graecus, Spalax 290

—istricus, Spalax 290

—Spalax graecus 290

hellenicus, Microspalax leucodon 231

hercegovinensis, Mesospalax 116*

hercegovinensis, Microspalax leucodon
231

hungaricus, Dolomys 127, 129

(hungaricus-episcopalis), group Dolomys
129

hungaricus, Mesospalax 116*

hungaricus, Microspalax 6, 229

—-—leucodon 231

—Spalax 5, 222

— —typhlus 222

hungaricus, Villanyia 127

hypotheticus, Macrospalax 116*, 117*

—Mesospalax 116*

intermedius, Microspalax 186
—Mimomys 130

—Spalax 177

istricus, Macrospalax 116*, 117*
istricus, Spalax 5, 6, 280, 289
istricus, —graecus 290

kirgisorum, Microspalax 116*, 186, 289

kirgisorum, —ehrenbergi 186, 187

—Spalax 177

Kislangia 127

—rex 127

kowalskii, Dolomys 129

labaumei, Microspalax 220

—Spalax 212

Lagomorpha 43

Lagurodon subspecies

—arankae 127

lagurodontoides, Mimomys

Lagurus 130

leucodon anatolicus, Microspalax 220, 221

—armeniacus—220

—captorum—221

leucodon cilicicus, Microspalax 221

—corybantium—221

leucodon dolborgeae 230

—hellenicus—231

—hercegovinensis—231

—hungaricus—231

—leucodon—106, 124, 224*, 226*, 228*,
230

—Microspalax 6, 67, 70, 81, 104*, 105-
107, 117*, 119*; 124, 131% 13211153.
211, 212, 216-220, 222, 227*, 228, 229,
230, 279

—w—leucodon 106, 124

—monticola, Microspalax 78*, 79*, 106,
124, 223*, 231

leucodon nehringi, Spalax 212

leucodon serbicus, Microspalax 231

—Spalax 106, 111, 222

leucodon, —typhlus 211, 222

leucodon syrmiensis, Microspalax 231

—thermaicus—23\

—transsylvanicus—230

leucodon turcicus—221

130

129

macoveii, Microspalax 103, 104*, 119*,
122, 123, 127, 129, 131*, 132, 159, 161,
173, 177, 177-178, 184, 185, 191, 192,
194*, 197-205, 210, 219

—Pliospalax 5, 67-71, 117%

Масоуей, Prospalax 192

macoveii, Spalax 201

Macrospalax 5, 118, 201, 232

Macrospalax antiquus 116*

—arenarius 117%

—diluvii 117%

—giganteus 116*, 117*

—graecus 116*, 117*

—hypotheticus 116*, 117*

—istricus 116*, 117*

—microphthalmus 116*, 117*

—polonicus 116*

—uralensis 117*

—zemni 117*

Marmot Podolian 269, 278

Mesocricetus auratus 48

Mesospalax subspecies 5, 6, 69-71, 105,
106, 116, 118, 121, 123, 124, 132, 171,
175-177, 191, 210, 211, 219, 298

—anatolicus 116*

—armeniacus 116*

—cilicicus 116%

—dolbrogeae 116*

—hercegovinensis

—hungaricus 116*

—hypotheticus 116*

—monticola 116*

—nehringi 116*

—serbicus 116*

—syrmiensis 116*

—transsylvanicus

—turcicus 116*

(microphthalmus), group 9,108-110, 125,
236, 243, 254, 255, 260, 283, 288, 288,
293, 296, 297, 300, 301

microphthalmus arenarius, Spalax 290

microphthalmus, Macrospalax 116*,
v=

microphthalmus minor, Spalax 248

—podolicus, Spalax 269

—polonicus—269

microphthalmus, Spalax 3,5, 47, 58, 68,
DONS S 74.177, 82 108 Ш 118%
119*, 125, 131*, 133, 232, 234, 237, 242,
243, 255, 256, 258*, 261*, 262, 263*,
265, 268, 270-274, 278, 279*, 284, 292,
294, 295, 298-301

microphthalmus, Spalax aff. 300

Microspalax 4-8, 14, 15*, 66-72, 80, 102,
103, 104*, 105-107, 116-118, 119*,
120-125, 126, 127-130, 132, 156, 159,

116*

116*

305

160, 164*, 165*, 166*, 167* 168*, 169*,
170, 174, 200-203, 221, 229, 230, 232,
234, 240, 288, 298

Microspalax, subspecies 106, 120-123,
132, 171, 174, 176, 180-187, 190-194,
199, 202, 204, 210, 211, 215, 216, 219

—aegyptiacus 116*, 187

—berytensis 187

Microspalax compositodontus 15*, 67,
71, 103, 104*, 119*, 120, 121, 128, 131*,
132, 159, 174, 176, 184, 188, 189*, 190,
191, 198-199, 210, 219

—dolborgeae 230

—ehrenbergi 5, 38*, 40*, 67-71, 80, 103,
104* 105. 116%; 117+, 119% 121-123,
131*, 132, 153, 158, 163, 173, 174, 177,
180*, 181*, 183%, 184-187, 190-193,
196, 197, 203, 206-210, 214, 219

——aegyptiacus 188

— —ehrenbergi 187

— —kirgisorum 187

—fritschi 6, 116*, 187

—hungaricus 6

—intermedius 186

—kirgisorum 116*, 186, 289

—labaumei 220

—leucodon 6, 67, 70, 81, 104*, 105-107,
HITE HOS 124131" 1132. 1173, 211,
212, 216-220, 222, 227*, 228, 229, 230,
279

—leucodon anatolicus 220, 221

——armeniacus 221

— —сарюгит 221

——cilicicus 221

— — согубапнит 221

—leucodon dolborgeae 231

— —hellenicus 231

— —hercegovinensis 231

— —Aungaricus 231

—w—leucodon 106,
228*, 230

——monticola 78*, 79*, 106, 124, 223*,
231

——serbicus 231

— —syrmiensis 231

— —thermaicus 231

— —transsylvanicus 230

—leucodon turcicus 221

—macoveii 103, 104*, 119*, 122, 123,
1275 129. 131% 132.159 16,
177-178, 184, 185, 191, 192, 194*, 195*,
197-205, 210, 219

124599224" 226%,

306

—monticola 6, 220, 229, 230

Microspalax nehringi 30*, 40, 47, 48, 50,
51*, 58, 60*, 62*, 67, 70, 80, 104*, 105,
116*, 123, 124, 131*, 132, 174, 191, 210,
212. 212. 214A 2g 218-220. 225

— —anatolicus 221

— —armeniacus 221

——captorum 221

ее Сы 12522] 292

— —corybantium 221

—-—nehringi 216*, 221, 222

— —turcicus 221

—odessanus 67-71, 103, 104*, 106, 119*,
121, 122, 129, 131*, 132, 174, 177, 178,
184—186, 190, 191, 192, 198—203, 204,
205*, 207*, 2087; 210, 211, 214. 219

Microtidae 277

Microtinae 4

Microtus 58, 64, 130

—arvalis 62*

—socialis 48

milleri, Dolomys 127, 130

—Dolomys aff. 126

Mimomys 127, 130

—feijervaryi 127

—intermedius 130

—lagurodontoides

—newtoni 127

—pliocaenicus

—praehungaricus

—pusillus 127

—reidi 129

—tanaitica 129

minor, Spalax 68, 108*, 108-111, 119*,
125 130, 131%. 1835 23542378 243: 2607,
269, 276, 288, 290, 291*, 293*, 295,
296*, 298—301

minor, —microphthalmus 248

Miospalax 117, 117*

—monacensis 118

moldavicus, Promimomys 126

monacensis, Miospalax 118

monticola, anatolicus, Spalax 212

monticola armeniacus, Spalax 212

—cilicicus, Spalax 212

—nehringi, Spalax 212

monticola Mesospalax 102*

—RMicrospalax 6, 220, 229, 230

—Microspalax leucodon 78*, 79*, 106,
124, 223*, 231

monticola, Spalax 5, 222

—turcicus, Spalax 212

129

127 2930
129

Mures subterranei 3

Muridae 3, 128

Mus 232

—typhlus 256, 269

Myoidea 3, 4, 14, 31, 32, 35, 40, 41, 45,
47, 50-52, 56-62, 63, 64, 66, 68, 113,
115

Myospalacinae 4, 20, 50, 52, 58, 60*

Myospalax 117

Nannospalax 170, 175-176

nehringi anatolicus, Microspalax 221

—armeniacus—221

—captorum—221

—cilicieus 215", 221, 20

—corybantium 221

—Mesospalax 116*

—Microspalax 30*, 40, 47, 48, 50, 51*,
58, 60*, 62*, 67, 70, 80, 104*, 105, 116*,
123, 124, 131*, 132. 174. Ч9Т: 210 219
212, 214*, 2]7* 2185220. 295

——nehringi 216*, 221, 222

—nehringi, Microspalax 216*, 221, 222

Nehringi, Spalax 212

nehringi, —leucodon 212

—-—monticola 212

nehringi turcicus, Microspalax 221

Nesokia 40, 50-51, 56

Nesomyinae 112-113

newtoni, Mimomys 127

norvegicus, Rattus 48

Ochotona 126

—antiqua 126

odessanus, Microspalax 67-71, 103,
104*, 106, 119*, 121, 122, 129, 131*,
132, 174, 177, 178, 184-186, 190, 191,
192, 198-203, 204, 205*, 207*, 208%,
210, 211, 214, 219

Ommatostergus 232

—Pallasii 256

Palaeotrogomorpha, group 4
Pallasii, Ommatostergus 256
Pallasii, Spalax 256
petenyii, Villanyia 129
Petromyidae 4
Pitymys 130
pliocaenicus, Mimomys
Pliopentalagus 126
Pliospalax 5, 6, 118, 170, 175, 200-203
—macoveii 5, 67-71, 117*

127, 129, 130

в ай

—гатапи$ 117*, 118

—simionescui 192, 202, 203

poirrieri, Rhizospalax 117*

Podolian Marmot 269, 278

podolica, Spalax 269

podolicus, Spalax 278

podolicus,—microphthalmus 269

polonicus arenarius, Spalax 248

polonicus, Macrospalax 116*

—polonicus, Spalax 280

—Spalax 5, 68, 70, 83, 107, 108*, 111,
119*, 126, 131*, 133, 235, 237, 243, 265,
266, 269, 271*, 273, 275*, 278, 279,
279* , 284, 297

polonicus, Spalax microphthalmus 269

polonicus, —polonicus 280

preaehungaricus, Mimomys 129

priscus, Ргозраах 5, 67, 116*, 117,
ire 119120. 126-128, 131% 2132)
154, 156, 158, 159, 161, 162

priscus, Spalax 155

Prolagus 126

Prometheomys schaposchnicovi 62*

Promimomys 129

Promimomys moldavicus 126

Proochotona 126

Prospalacinae 6, 10, 13, 27, 44, 67-69,
101*, 102, 103, 113-114, 119, 119*, 120,
126, 132, 153, 156, 157, 164, 200

Prospalax 5, 6, 119*, 132, 153, 155, 156,
158, 200, 201, 203, 298

Prospalax, Macoveii 192

Prospalax, priscus 5, 67, 116*, 117, 117%,
119*, 120, 126-128, 131*, 132, 154, 156,
158, 159, 161, 162

—rumanus 5, 67, 118, 119*, 120, 126, |

127. 131. 132157, 161. 162. 162* 201,
203
pusillus, Mimomys 127

Rattus 50-51

—norvegicus 48

reidi, Mimomys 129

rex, Kislangia 127

Rhizodontes 4

Rhizomyidae 4

Rhizomyinae 4, 20-27, 113, 114, 115*,
117*

Rhizomyini 4

Rhizomys 12*, 17*, 18*, 19*, 20*, 22*,
35+. 117%

Rhizospalacinae 114, 115*, 119, 120

307

Rhizospalax 113, 114, 115*

—poirrieri 117%

rumanus, Pliospalax 117*, 118

—Prospalax 5, 67, 118, 119*, 120, 126,
127 131. 132. 157. 161. tele. 162, 201,
203

schaposchnicovi, Prometheomys 62*

Scirtopoda telum 82

serbicus, Mesospalax 116*

serbicus, Microspalax leucodon 231

simionescui, Pliospalax 192, 202, 203

socialis, Microtus 48

Spalacidae’’ ait, v, 3. 5, 7, 13, 14, 21, 23,
24, 27-29. 31-36, 37, 43, 45, 46, 47, 48,
52—64, 68, 80, 100, 101*, 102, 112-115,
SRS MSA ile Milos, 131-82 153)
277

Spalacina 3

Spalacinae 6, 10, 13, 27, 44, 67, 69, 80,
107 113. 119*_ 120. 128. 1328153=157.
159, 163, 164, 175, 191, 200, 203, 237

Spalaxe 38. 12" 14. 16: 16+ 17% 18+.
19* 20%) 35* 66 72. 106-110, 116 118.
По WB), 175), 178. 130. 13. 155}. 15%)
163, 164*, 165*, 166*, 167*, 168*, 169%,
170—174, 177, 201, 202, 211, 232, 234,
235, 239, 242, 282, 288, 297-300

Spalax advenus 299

Spalax aegyptiacus 177

Spalax aff. microphthalmus 300

АЛЕН 5. 1, se. Bike (05. 0, Bes
LOS= a 10911 922512 Geel sit e133)
235-237, 241-247, 248, 251, 252, 254,
255, 256, 257, 265, 266, 267, 279*, 294-
295, 301

—-—arenarius 256

Spalax berytensis 177

Spalax diluvii 269, 278

Spalax dolbrogeae 222

—ehrenbergi 4, 5, 70, 170, 175, 177

—fritschi 5

—Fritschi 177

Spalax giganteus 5, 11*, 58, 68-70, 108*,
118, 119, 123-125, 131*, 133, 186, 234,
235, 237, 240*, 243*, 244, 247-250, 254,
255, 267, 286, 295, 298

—w—uralensis 248

—graecus 5,6, 68, 70, 85, 108*, 111, 118,
119*, 126, 131*, 133, 232, 235, 236, 243,
257, 260, 266, 267, 276, 280, 281*, 284*,
287*, 289, 294, 295, 297

308

— —antiquus 290

—-—sgraecus 290

—w—istricus 290

Spalax hungaricus 5, 222

—intermedius 177

Spalax istricus 5, 6, 280, 289

Spalax kirgisorum 177

—labaumei 212

—leucodon 106, 111, 222

—leucodon nehringi 212

Spalax тасоуей 201

—microphthalmus 3, 5, 47, 58, 68,
70; 73* 7477 32. 1081 Е а
119% 125. 131%. 133, 232 234. 231 242.
243, 255, 256, 258, 261*, 262, 263*, 265,
268, 270-274, 278, 284, 292, 294, 295,
298—301

—microphthalmus arenarius 290

— — итог 248

——podolicus 269

——polonicus 269

—minor 68, 108*, 108-111, 119*, 125,
130, 131*, 133, 235, 237, 243, 267, 269,
276, 288, 290, 291*, 293*, 295, 296*,
298-301

Spalax monticola 5, 222

— —anatolicus 212

— —armeniacus 212

— —cilicicus 212

— — пейния 212

— —turcicus 212

—Nehringi 212

Spalax Pallasii

—podolica 269

—podolicus 278

—polonicus 5, 68, 70, 83, 107, 108*, 111,
119% 126, 131* 133. 235 237, 243, 265,
266, 269, 271*, 273*, 275*, 278, 279*,
284, 297

—polonicus arenarius 248

256

—polonicus polonicus 280
Spalax priscus 155
Spalax sen. str. 118, 201

—sp. 298, 300, 301*

Spalax typhlus 177, 269, 278
— —hAungaricus 222

— —leucodon 211, 222
——xantodon 256

—uralensis 237, 248

Spalax zemni 269, 278

——arenarius 248

Steneofiber 126, 128

subterranei, Mures 3

syrmiensis, Mesospalax 116*

syrmiensis, Microspalax leucodon 231

Tachyoryctes 113, 117*

Talpoides 232

tanaitica, Mimomys

telum, Scirtopoda 82

thermaicus, Microspalax leucodon 231

transsylvanicus, Mesospalax 116*

transsylvanicus, Microspalax leucodon
230

Trhynomyidae 4

Trilophomys 103, 128

turcicus, Mesospalax 116*

turcicus, Microspalax leucodon 221

—-—nehringi 221

—Spalax monticola 212

typhlus hungaricus, Spalax 222

—leucodon, Spalax 211, 222

—Mus 256, 269

—Spalax 269, 278

—xantodon, Spalax 256

—Spalax, 177

129

ucrainicus, Dolomys 129
Ujhlyiana_ 170

Ungaromys 103, 128
uralensis, Macrospalax 117*
uralensis, Spalax 237, 248
uralensis, —giganteus 248

Villanyia 128, 129, 130
(Villanyia—Cseria), group 129
Villanyia exilis 127
—hungaricus 127

—petenyii 129

xantodon, Spalax typhlus 256

zemni arenarius, Spalax 248
—Glis 269, 278

zemni, Macrospalax 117*
zemni, Spalax 269, 278

(Contd. from front Пар)

Neocenic and Anthropogenic continental
deposits in the southern region of the
European part of the USSR and adjacent
territories. Taking into consideration also
the Pontiac origin of the Mediterranean
Sea and the present distribution of Spala-
cidae, it is self-evident that the evolution
and geographical distribution of the family
in the past, and at present, were dictated
by a distinct influence—mainly by the
contours (Sarmatian, Miocean, and Pontiac
Seas) of these basins during their entire
geological history.

The book reviews fossil and present-day
mole rats of the family Spalacidae (Roden-
tia, Mammalia) from all over the world.
The general characteristics of the family, the
basic adaptive characteristics of its ances-
tors and the occurrence of basic adapta-
tions in phylogeny and postembryonic
ontogeny are given. Data are presented on
the distribution of this group in the past
and at present. The phylogeny of the
family has been worked out. A recon-
struction of the taxonomy of mole rats
has been made. A separation of subfamilies
and certain genera has been done for the
first time.

OSs ош В Вю оао