UNIVERSITY OF

ILLINOIS LIBRARY

AT URBANA-CHAMPAIGN

BIOLOGY

APR 0 9 1992

FTEL

Zoology

W SERIES, NO. 57 //,

f

%

Mice of the Akodon boliviensis Size Class
(Sigmodontinae, Cricetidae), with the
Description of Two New Species from Brazil

Philip Hershkovitz

LLHALL

July 31, 1990
Publication 1412

PUBLISHED BY FIELD MUSEUM OF NATURAL HISTORY

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Croat, T. B. 1978. Flora of Barro Colorado Island. Stanford University Press, Stanford, Calif., 943 pp.

Grubb, P. J., J. R. Lloyd, and T. D. Pennington. 1963. A comparison of montane and lowland rain forest in Ecuador.

I. The forest structure, physiognomy, and floristics. Journal of Ecology, 51: 567-601.
Langdon, E. J. M. 1979. Yage among the Siona: Cultural patterns in visions, pp. 63-80. In Browman, D. L.,and R. A.

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Murra, J. 1946. The historic tribes of Ecuador, pp. 785-821. In Steward, J. H., ed., Handbook of South American

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FIELDIANA

Zoology

NEW SERIES, NO. 57

Mice of the Akodon boliviensis Size Class
(Sigmodontinae, Cricetidae), with the
Description of Two New Species from Brazil

Philip Hershkovitz

Department of Zoology

Field Museum of Natural History

Chicago. Illinois 60605-2496

Accepted June 6, 1989
Published July 31, 1990
Publication 1412

PUBLISHED BY HELD MUSEUM OF NATURAL HISTORY

© 1990 Field Museum of Natural History
Library of Congress Catalog Card Number: 90-82650

ISSN 0015-0754
PRINTED IN THE UNITED STATES OF AMERICA

Table of Contents

Abstract 1

ntroduction 1

Material 1

Nomenclature 3

Discussion 3

akodon boliviensis slze class 3

Characters 9

Akodon mollis Size Class 11

akodon lindbergh!, new species (matosa

Akodon) 16

Characters 17

Akodon lindberghi and the Nomen

Nudum Plectomys paludicola 21

Population Dynamics 22

Survival Status 23

Akodon sanctipaulensis. New Species (SAo

Paulo Marsh Akodon) 23

Characters 25

\cknowledgments 29

Literature Cited 34

List of Illustrations

1. Map of southeastern Sao Paulo showing
collecting localities of Akodon sancti-
paulensis. Inset: Map of Brazil showing
States and collecting locality of Akodon
lindberghi in Distrito Federal 2

2. Saturation of agouti cover-hair through
eumelanin and pheomelanin pathways . . 10

3. Skulls, dorsal and ventral aspects of
Akodon boliviensis, Akodon cursor, Ako-
don andinus dolichonyx, and Bolomys
lasiurus 12

4. Skulls and mandibles, left side of Ako-
don boliviensis, Akodon cursor, Akodon
andinus dolichonyx, and Bolomys lasi-
urus 13

5. Right upper and lower left molars of
Akodon boliviensis, Akodon cursor,
Abrothrix longipilis. and Bolomys lasi-
urus 14

6. Akodon lindberghi: Cheiridia, dorsal
and ventral surface of right hand and

foot 15

7. Skulls of Akodon: Dorsal and ventral
aspects of Akodon sanctipaulensis, Ako-
don lindberghi, and Akodon azarae .... 16

8. Skulls and mandibles of Akodon sancti-
paulensis, Akodon lindberghi, and Ako-
don azarae 17

9. Molars, right upper and lower left of
Akodon sanctipaulensis, Akodon lind-
berghi, and Akodon azarae 18

10. Akodon lindberghi: Glans penis 19

1 1 . Glans penis in Akodon boliviensis (ven-
tral aspect) and Bolomys lasiurus (ven-
tral and lateral aspects) 20

1 2. Abrothrix longipilis: Glans penis 21

13. Matosa habitat of Akodon lindberghi in
Parque Nacional de Brasilia, DF 22

14. Akodon sanctipaulensis: Cheiridia, dor-
sal and ventral surface of right hand and
foot 24

15. Skull, dorsal and palatal aspects show-
ing cranial measurements used in text . . 27

16. Akodont type skull, dorsal aspect 28

17. Akodont type skull, palatal aspect 30

18. Akodont type skull, left side 31

19. Akodont type left mandible 32

20. Upper and lower molar crown pattern

of akodont type rodents 32

2 1 . Molar crowns of sigmodontine rodents;
evolutionary stages from primitive
crested to derived plane in side and

crown views 33

22. Sigmodontine incisor curvature with
reference to the basal-incisive and verti-
cal-incisive planes 34

List of Tables

1. Measurements and diploid chromosome
numbers of taxa of Akodon boliviensis
group and some related akodonts 4

2. Ratios of some cranial and external mea-
surements of taxa of Akodon boliviensis
group and some related akodonts 7

3. External and cranial measurements of
Akodon lindberghi 8

4. External and cranial measurements of
Akodon sanctipaulensis 26

in

Mice of the Akodon boliviensis Size Class
(Sigmodontinae, Cricetidae), with the
Description of Two New Species
from Brazil

Abstract

Two species of Brazilian sigmodontine mice de-
scribed as new are Akodon lindberghi, known from
less than a hectare plot of cerrado near Brasilia,
DF, and Akodon sanctipaulensis, from the marsh-
es at the eastern base of the Serra do Mar in south-
eastern Sao Paulo. Survival status of the first is
discussed. Both species are included in the Akodon
boliviensis size class, an assemblage of the 13
smallest species nearest the typical form of the
genus. The larger species of Akodon, all in the A.
mollis size class, are listed with taxonomic notes.
The phyletic relationship between species within
and between the size classes has not been deter-
mined. The provisional arrangement is for con-
venience of characterization of the two new species
within a difficult, undefined genus. Other taxa of
the akodont group used for reference are also dis-
cussed. Plectomys paludicola, a nomen nudum
mentioned in the literature, is the same as Akodon
lindberghi.

mals of the region during the last decade failed to
reveal the presence of this savannah species out-
side the narrowly restricted plot of an otherwise
extensive suitable habitat (fig. 1 ).

A third species of Akodon, from open, marshy
fields on the eastern base of the Serra do Mar in
southeastern Sao Paulo State, collected in 196 1 by
A. M. Olalla, also appears to be distinctive, and
is described as new.

This is the first of a planned series of taxonomic
and biogeographic papers on the small mammals
of the Atlantic forest region of southeastern Brazil
and the cerrado of central Brazil. Cooperative
fieldwork with the Museu Nacional and the Uni-
versidadede Brasilia was carried out in 1986, 1987,
and 1988. It is expected that continued collabo-
ration between the Brazilian scientific institutions
and the Field Museum of Natural History will
result in a thorough inventory of the small mam-
mals of the highlands and fragmented remains of
the coastal forest of Brazil.

Introduction

Material

A collection of small mammals made during
July and August 1986, in the cerrado region of
Brasilia, Distrito Federal (fig. 1), includes two
species of the sigmodontine genus Akodon. One,
the wide-ranging Akodon cursor Lund, is repre-
sented by four specimens. The second, heretofore
undescribed, is represented by seven specimens
captured in a small segment of wet valley-side
open grassland, or cerrado campo limpo. Intensive
trapping and ecological studies of the small mam-

Specimens examined of the tribe Akodontini in
the collections of the Field Museum of Natural
History (fmnh) represent nearly all species of all
tribal genera except Blarinomys and Juscetinomys.
They, together with others of the tribe, were stud-
ied in the Museu Nacional, Rio de Janeiro, and
the British Museum (Natural History), London.

The last eight figures in the text (figs. 15-22)
illustrate all cranial, dental and morphometric ter-
minologies used here. Reference will be made to

HERSHKOVITZ: NEW SPECIES OF AKODON

Fig. 1 . Map of southeastern Sao Paulo showing collecting localities (2, 3, 4, 5) of Akodon sanctipaulensis. Inset,
map of Brazil showing States and collecting locality (1) of Akodon lindberghi in Distrito Federal (black square). Data
for the Sao Paulo localities are from A. M. Ola 1 la's field notes, a copy of which was loaned to me by M. Traylor
through the courtesy of P. Vanzolini.

FIELDIANA: ZOOLOGY

these illustrations in subsequent papers on Bra-
zilian akodonts.

Nomenclature

There is no distinctive vernacular equivalent for
the generic name Akodon. The technical name it-
self, however, is apt for vulgarization. The epithet
akodon is suggested. It slips easily ofTthe tongue,
particularly of Spanish and Portuguese speaking
people of countries where the genus occurs. The
name vole, sometimes applied to akodonts. is bet-
ter left with the arvicolincs where it belongs.

The abbreviation for molar is m whether upper
or lower. Upper case M as the first letter of a
sentence means the same as lower case m. The
identity of the upper or lower molars is indicated
by a superscript or subscript (examples, m\ m,).

Discussion

Akodon, one of the most diversified and wide
ranging genera of South American mammals, has
never been formally revised taxonomically. Its
systematic limits are unclear, the identities and
assignments of some included species are con-
fused. Cabrera (1961) admits 90 species and sub-
species distributed among the subgenera Akodon
(55). Abrothrix (12), Chroeomys (9), Deltamys(l),
Hypsimys ( 1 ), Thaptomys (2), Thalpomys ( 1 ), Bo-
lomys (5), and Microxus(4). The subgenus A kodon
as understood by Cabrera is a composite of typical
forms clustered around the type species A. boli-
viensis Meyen, a few species (and subspecies) of
Abrothrix, and a few species of Bolomys.

A recent review of Akodon by Reig (1987), in-
tended primarily as a background for descriptions
of several fossil forms, provides, on the whole, a
better understanding of the genus. Contrary to Ca-

brera, Reig treated Bolomys and Microxus as dis-
tinct genera. His restricted genus Akodon includes
the subgenera Akodon (23 living species including
Thalpomys reinhardti or lasiotis, and 3 species of
Abrothrix), Abrothrix (7 species), and monotypic
Chroeomys, Deltamys, and Hypsimys.

In the present account, the subgenus Akodon is
comprised of about 2 1 species ranging in size from
Akodon lutescens with average skull length about
22 mm to A. varius (sensu lato) with average skull
length about 29 mm (table 1). The gradient can
be conveniently divided into two size classes. The
first, or typical Akodon boliviensis size class, is an
assemblage of 1 3 species with greatest skull length
of each species averaging less than 26 mm. The
second, or A. mollis size class, contains 20 named
forms representing about 8 species, with greatest
skull length of each species averaging more than
26 mm. The classes overlap narrowly in cranial
size, but differences other than size (mainly of the
individual species), maintain separations between
them. Phyletic relationship between the species of
both groups has not been determined except cy-
togenetically to a limited extent. Only the Akodon
boliviensis class, which includes the two new
species, is described. Members of the A. mollis
class are simply listed with taxonomic comments.

Akodon boliviensis Size Class

Included Species (tables 1 , 2)— Akodon alterus
Thomas, 1919; A. azarae Fischer, 1829; Akodon
boliviensis Meyen, 1 833 (type species); A. caenosus
Thomas, 1918;/!. iniscatus Thomas, 1919; A lu-
tescens J. A. Allen, 1901; /i. m/ovsThomas, 1926;
A. pacific us Thomas, 1902; A. puer Thomas, 1902;
A. subfuscus Osgood, 1944; ^4. tucumanensis J. A.
Allen, 1901; A. lindberghi (new species), and A.
sanctipaulensis (new species).

(Explanation of map, fig. 1)

1. Parque Nacional de Brasilia. Brasilia, DF; 15°35'-15°45'S, 47°55'-48°05'W; 700-1,300 m; area 28,000 ha; rolling
plateau of quartzite and limestone; mean annual temperature 20.6° C; annual rainfall 1,675 mm; cerrado, campo
cerrado cerraddo, and Amazonian type gallery forests around springs and along valley streams. P. Hershkovitz
and Scott Lindbergh, August 1986.

2. Iporanga, Sao Paulo; ca. 24°07'S, 47°38'W; 40 m; on Rio Acungui (= Assunagui), 10 km above confluence with
Ribeirao das Corujas; agriculture; second growth, patches primary forest. A. M. Olalla, October 1961.

3. Morretinho, Sao Paulo; ca. 24°0 1 'S, 47°44'W; 40 m; said to be about 30 km NNW of Juquia (ca. 24°19'S, 47°48'W).
A. M. Olalla, September 1961.

4. Primeiro Mono, Sao Paulo; 24°22'S, 47°49'W; ca. 1 6 km NW Juquia (24°1 9'S, 47°38'W) on highway to Sete Barras
(24°23'S, 47°55'W); camp on left bank Ribeirao Fundo, where the stream crosses highway to Sete Barras and
empties into the Rio Juquia; swamps, second growth. A. M. Olalla, July, September, October 1961.

5. Quadro Penteado. Sao Paulo; ca. 24°20'S, 48°09'W; 50 m; 31 km W Sete Barras; camp near junction Rio Eta and
Ribeirao Brazinho, in Rio Ribeira do Iguape basin; mostly primary forest. A. M. Olalla, October, November
1961.

HERSHKOVITZ: NEW SPECIES OF AKODON

Table 1. Measurements (in millimeters) and diploid chromosome numbers (2n) of taxa of Akodon boliviensis
group and some related akodonts. Shown are means, extremes in parentheses, followed by number of specimens;
sexes and localities of each taxon are combined. Numbered superscripts refer to notes on following page.

Taxon

Head and body

Tail

Hind foot with claw

Ear from notch

lindberghi'

92 (86-94) 6

63 (56-66) 6

18.7(18-19)6

13.3(13-14)6

sanctipaulensis2

93(86-100)4

72(63-81)4

23.8 (23.3-25) 4

15(13-17)4

boliviensis*

99(90-115) 11

62 (55-66) 1 1

21 (20-22) 11

—

alterus4

91,89, 100

63,61,78

19, 19,20

13, 13, 13

tucumanensisi

92(80-115) 10

70 (50-75) 9

21 (18-25) 10

—

subfuscush

97(83-107) 11

71 (62-82) 11

21 (19-23) 12

—

azarae1

100(92-114)24

68 (57-83) 24

20.2(19-22)21

—

puer

84 (75-94) 5

71 (70-75)5

18(15-20)5

15(15-15)4

caenosus*

98(85-103)9

60 (56-64) 9

19(18.5-19.5)9

—

iniscatus9

95(86-102)5

63 (58-66) 5

19.7(18-20)5

12(11.5-13.5)5

lute see ns'°

78(76-81)5

60 (57-64) 5

19.4(19-20)5

—

amoenus' '

93(84-100)5

63(61-67)5

21.2(21-22)5

—

nigrita'2

96(82-116) 15

45(30-50) 15

19(16-20) 17

11 (10-12) 12

dolichonyx'*

87(77-94) 14

55(47-66) 14

20.3(19-22) 14

—

brevieeps'4

104.3

42.21 (30-52) 19

18.29(16-21)21

9.7(8-10)21

xanthorhinus'^

92 (88-94) 5

56 (52-58) 5

20.8(20.5-21)5

—

longipilis'b

126(118-141)6

91 (79-105)6

29(28-31)6

-

Weight

Taxon

(g)

Greatest skull length

Condylobasal length

Zygomatic breadth

lindberghi'

18(16-19)4

24.1 (23.5-24.4)5

22.5(21.7-22.9)5

12.1 (11.8-12.4)5

sanctipaulensis2

—

24.6, -, ca. 27, -

23.7, -, -, -

12.1, -, 13.5, -

boliviensis*

—

24.6 (23.8-25.6) 9

23.2 (22.2-24.4) 9

12.6(11.8-13.2)8

alterus4

—

24.0, 22.8, 26.0

—

12.2, 12.0, 12.4

tucumanensis5

—

25.2 (24.0-26.4) 9

23.6 (22.2-24.8) 8

12.3(11.5-13.4)9

subfuscusb

—

24.8(24.1-26.0) 11

22.9(21.9-24.0) 11

12.3(11.8-12.9) 12

azarae1

—

24.4(22.8-26.1)21

21.6(20.8-24.6)22

12.3(11.3-13.3)23

puer

—

24.4, -,22.9,23.7

22.8,20.9,21.2, -

11.7(11.4-12.3)4

caenosuss

—

23.6 (23.0-23.9) 9

21.7(20.8-22.3)9

11.7(11.5-12.1)9

iniscatus9

—

25.8,25.5,23.5

23.0 (20.6-23.9) 5

12.9, 13.1, -

lutescens"'

—

22.3 (22.0-22.7) 4

20.5(20.1-20.9)5

11.1 (10.7-11.3)5

amoenus' '

—

24.1 (23.6-24.6)5

23.6 (23.2-23.9) 4

13.7(13.1-15.4)5

nigrita12

25(20-31)6

24.1 (23.1-25.3) 12

23.5(21.7-25.0) 11

13.1 (12.1-13.9) 11

dolichonyx'*

—

23.4 (22.4-24.4) 8

21.7(20.7-22.4)8

11.9(11.5-12.6)8

brevieeps14

—

25.86(24.8-27.4) 14

23.12(21.7-24.0) 14

13.7(12.9-14.6)7

xanthorhinus'5

—

25.0(24.1-25.3)5

22.7(21.6-23.4)5

12.5(12.0-12.8)5

longipilis'b

—

32.0 (30.8-33.4) 6

29.2 (27.9-30.8) 6

15.4(14.6-16.2)6

Least inter-

Taxon

orbital width

Braincase width

Frontal bone length

Nasal bone length

lindberghi'

4.8 (4.6^.9) 5

11.12(11.1-11.2)5

8.7(8.4-9.1)5

8.2 (7.9-8.4) 5

sanctipaulensis2

4.5(3.5-5.3)4

12.0, -, 11.9

8.5(8.1-9.2)4

10.1 (9.5-10.4)4

boliviensis*

4.2(4.1^.4) 10

11.2(10.8-11.5)8

9.2(8.6-10.0) 10

8.5 (7.9-9.8) 9

alterus4

4.2,4.4,4.3

-, 11.0, 11.6

8.7, 9.2, 9.9

8.5,8.3,9.2

tucumanensis5

4.4(4.1-4.7) 10

11.3(10.7-11.7)9

9.1 (8.7-9.8) 10

8.0(8.4-9.7) 10

subfuscus6

4.5(4.2-4.7) 12

11.4(11.1-11.7) 12

8.3(6.7-9.5) 12

9.2(8.0-10.6) 11

azarae7

4.1 (3.8-4.5)23

11.2(10.7-11.7)24

8.8(8.2-9.4)21

8.8(8.1-9.8)21

puer

4.3 (4.2^1.6) 4

10.8(10.5-11.2)4

7.9 (7.7-8.5) 9

8.9,-8.1,8.4

caenosus*

4.3(4.1-4.4)9

10.9(10.4-11.2)9

8.1 (7.7-8.5)9

8.5(7.7-8.5)9

iniscatus9

4.1 (4.0-4.2)5

11.4(11.2-11.9)5

9.0 (8.5-9.6) 4

9.0 (8.6-9.5) 4

lutescens'0

4.1 (4.0-4.2)5

10.7(10.4-10.9)5

7.9 (7.2-8.4) 5

7.8(7.3-8.1)4

amoenus' '

4.3(4.1-4.6)5

11.0(10.8-11.3)5

9.1 (8.7-9.3)5

7.7(7.2-8.3)5

nigrita'2

5.0(4.7-5.4) 17

11.5(10.8-12.1) 12

7.4(6.5-8.1)8

9.2(8.1-10.0) 14

dolichonyx'*

4.0(3.8-4.1)8

11.3(10.9-11.8)8

7.2 (5.8-7.9) 9

8.7 (7.6-9.3) 9

brevieeps'4

6.79 (6.5-7.2) 20

—

—

11.3(10.9-12.0)4

^anthorhinus'5

3.9 (3.8-4.0) 5

11.5(10.9-12.0)5

7.5(7.1-8.0)5

9.5 (8.8-9.9)'5

longipilis'b

5.0 (4.8-5.2) 6

13.9(13.4-14.1)6

9.4 (8.5-9.8) 6

12.5(11.6-13.1)6

FIELDIANA: ZOOLOGY

Table 1. Continued.

Taxon

Incisive foramina

Palatal bridge

Mesopterygoid
fossa

Zygomatic plate
ant.-post.

lindberghi'

6.2(5.9-6.7)5

2.9(2.7-3.1)5

1.3(1.0-1.4)5

1.8(1.7-1.9)5

sanctipaulensis2

5.9(5.7-6.1)4

3.5(3.2^4.1)4

1.6, 1.4.2.0, -

2.0(1.9-2.0)4

boliviensis*

5.6(5.2-5.9) 10

3.3(3.0-3.8) 10

0.9(0.6-1.0) 10

2.2(2.0-2.6) 10

alterus*

5.7, 5.5,6.4

3.0. 3.3. 3.6

-. 1.2.0.9

2.2,2.2.2.3

tucumanensis''

6.1 (5.4-6.8)9

3.2 (3.0-3.4) 7

1.0(0.9-1.1)7

2.2(1.8-2.5) 10

subfuscus"

5.9(5.5-6.5) 11

3.3(2.9-3.8) 12

1.3(1.0-1.8) 10

2.0(1.7-2.4) 12

azarae1

6.1 (5.6-6.8)23

3.2(2.1-3.6)23

1.3(0.9-1.6)21

2.2(1.9-2.4)24

puer

5.7(5.4-6.2)4

2.9(2.8-3.1)4

1.0(8.1-1.1)4

2.2(2.0-2.5)4

caenosus*

5.7(5.1-6.1)9

3.1 (2.7-3.4)9

0.99(0.8-1.2)9

2.0(1.9-2.2)9

iniscatus"

5.8(5.5-6.2)5

-. -.3.6

0.98(0.9-1.0)5

2.6(2.3-2.8)5

htiescens10

5.4(5.1-5.7)5

3.1 (3.0-3.2)5

1.0(0.8-1.2)5

1.9(1.6-2.1)5

amoenus' '

5.6 (5.3-6.0) 5

3.7(3.1^.2)5

1. 1 (1.0-1.2)5

2.5(2.3-2.7)5

nigrita ' :

5.4(4.9-5.9) 17

3.8(3.5-4.1) 16

1.3(1.1-1.4) 12

2.3(2.0-2.7) 17

dolichonvx'*

5.2(4.7-5.7) 10

3.5(3.2-3.6) 10

1.2(1.0-1.3) 10

2.16(2.0-2.3)9

breviceps'4

5.03(4.3-5.4) 18

—

—

—

xanthorhinus'"'

6.0(5.3-6.3)5

3.6 (3.4-3.7) 5

1.0(0.9-1.2)5

1.9(1.8-2.0)5

longipilis"'

7.4(6.9-7.9)6

4.5(4.2^4.7)6

1.9(1.7-2.0)6

2.6(2.4-2.9)6

Rostrum greatest

Molar row

Greatest bullar

Taxon

breadth

(alveolar)

width

Diploid chromosome number

lindberghi'

4.4(4.3-4.5)5

4.0(3.9-4.1)5

3.9(3.7-4.0)5

42 (Svartman, pcrs. comm.)

sanctipaulensis2

4.3, -,4.3, 4.3

4.15(4.1-4.3)4

4.4, -, -, -

—

boliviensis*

4.6(4.4-4.8) 10

4.0(3.9-4.1) 10

4.3(4.1-4.6) 10

40(Bianchi el ai, 1971)

alterus4

4.2,4.4,4.6

4.3. 4.0, 4.4

4.2,3.9,4.1

—

: tucumanensis*

4.5(4.3^.8) 10

4.1 (3.9-4.6) 10

4.0 (3.8-4.2) 9

40(Bianchi et ai, 1971)

subfuscus6

4.4 (4.2^4.7) 1 1

3.9(3.5-4.5) 12

4.0(3.9^4.3) 12

—

| azarae

4.3(3.9^4.7)21

4.1 (3.8^4.3)24

4.1 (3.9-4.6)24

38/37 (Bianchi and Contreras,
1967)

puer

caenosus*

iniscatus9

htiescens'"

amoenus' '

nigrita ' :

dolichonyx13

breviceps'4

xanthorhinus1''

iongipilis"'

4.0(3.7-4.1)4

4.2(4.0-4.3)9

4.62(4.6-4.7)4

4.1 (3.9-4.2)5

4.5(4.2^.8)5

4.6(4.4-5.0) 17

4.2(3.5-4.5)9

4.4(4.2-4.5)5
5.4(5.1-5.7)6

3.6(3.5-3.7)4
3.5(3.4-3.7)9
3.9 (3.3-4.3) 5
3.6(3.4-3.7)5
4.1 (3.9-4.3)5
3.7(3.5-3.9) 17
3.4(2.8-3.7)9

4.41 (4.42^.6)20

3.5(3.4-3.8)5

4.8(4.5-5.1)6

4.0(3.9-4.1)4

3.9(3.5-4.3)9

4.0(3.7^4.2)5

4.02(4.0-4.1)5

4.4 (4.3^4.6) 5

4.1 (3.9-4.2)8

4.4(3.8^4.7)8

4.3 (4.2-4.6) 5
5.0 (4.8-5.2) 6

34 (Vitullo et ai, 1980)
34(Barquez et ai, 1980)
33/34 (Barros et ai, 1990)

34 (Armada et ai, 1983)
52(Yonenaga, 1975)
52 (of A kodon andinus.
Armada et ai, 1983)

52 (Bianchi et ai, 1971)
52(Gallardo, 1982)

1 See Table 3 for individual measurements.

: See Table 4 for individual measurements.

3 Akodon spegazzinii Thomas, 1897, with diploid chromosome number 40 (Bianchi et ai, 1971), is treated as a
subspecies by Cabrera (1961, p. 44 1 ).

"See 5.

''Akodon tucumanensis J. A. Allen, 1901, is treated as a subspecies of Akodon bolivianus, with Akodon alterus
Thomas, 1919, a synonym, by Cabrera (1961, p. 441).

h Originally described by Osgood (1944, p. 195), as a subspecies of Akodon boliviensis.

7 Ration agreste Brants, 1827, is a senior synonym of Mus azarae Fischer, 1829 (figs. 7-9 this paper); junior
synonyms or subspecies include Mus (Habrolhrix) arenicola Waterhouse, 1837, Akodon azarae bibianae Massoia.
1971 (2n = 38, Vitullo et ai, 1986), and possibly Habrolhrix arenicola fossitis Ameghino, 1889. Akodon arenicola
humeri Thomas, 1917 and Akodon sylvanus Thomas, 1921, both treated as subspecies of Akodon azarae, by Cabrera
(1961, pp. 440—441) may be conspecific with each other but apparently not with the smaller A. azarae. They are
referred here to the Akodon mollis group.

* Originally described by Thomas, 1 9 1 8 (p. 1 89) as a subspecies of Akodon puer Thomas, 1 902, but Thomas ( 1 920,
p. 191) later regarded it as distinct.

" Includes collinus Thomas, 1919, as a subspecies; Akodon nucus Thomas, 1926, listed as a subspecies of puer by
Cabrera (1961, p. 443) appears to be unrelated. Akodon iniscatus is notable for its extremely wide zygomatic plate
with greater than usual projection beyond the anteorbital foramen.

HERSHKOVITZ: NEW SPECIES OF AKODON

Table 1. Continued.

10 According to Sanborn (1949, p. 315) Akodon lutescens J. A. Allen, 1901, is a subspecies of Akodon andinus with
Akodon andinus polius Osgood a synonym. However, A. lutescens, with polius a synonym, belongs to the Akodon
boliviensis class whereas A. andinus does not (see 13 below).

" Bolomys amoenus Thomas, 1900, type species. Bolomys Thomas, 1916, is listed as a subgenus of Akodon by
Cabrera (1961, p. 453), and as a genus by Reig (1987, p. 356), who includes the following named forms in the genus:

amoenus Thomas, 1 900

arviculoides Wagner, 1 842 (as a synonym of lasiurus)

bene/actus Thomas, 1 9 1 9 (as a synonym of obscurus)

brachyurus Wagner, 1845 (as a synonym of lasiurus)

elioi Contreras, 1982 (as a subspecies of temchuki)

fuscinus Thomas, 1897 (as a possible subspecies of lasiurus)

lactens Thomas, 1918

lasiotis Lund, 1838 (as a synonym of lasiurus)

lasiurus Lund, 1838

lenguarum Thomas, 1898

leucolimnaeus Cabrera, 1 926 (as a possible subspecies of lactens)

liciae Contreras, 1982 (as a subspecies of temchuki)

negrito Thomas, 1 926 (as a synonym of lactens)

obscurus Waterhouse, 1837

orbus Thomas, 1 9 1 9 (as a synonym of lactens)

pixuna Moojen, 1943 (as a possible subspecies of lasiurus)

tapirapoanus J. A. Allen, 1916 (as a probable synonym of lenguarum)

temchuki Massoia, 1982

The diploid chromosome number 34 has been recorded (cf. Reig, 1987, p. 356) for specimens referred to amoenus,
elioi, lactens, lasiurus, lenguarum, liciae, obscurus, and temchuki. According to Maia and Langguth (1981), the basic
diploid number for samples of arviculoides from Pernambuco is 16 (FN 26/25). This species, therefore, cannot be
conspecific with lasiurus (figs. 3-5). It has been combined with Bolomys as well as Akodon but may belong with
neither genus (cf. Ximenez and Langguth, 1970, for type skull of arviculoides). The taxonomic status of remaining
named forms with karyotypes unknown or morphological affinities unclear, is subject to confirmation.

12 Thaptomys nigrita Lichtenstein, 1829. Thaptomys Thomas, 1916, is listed as a subgenus of Akodon by Cabrera
(1961, p. 452). According to Reig (1987, p. 358), "separation of Thaptomys from Akodon s.s. is unwarranted" because,
he avers, nothing distinguishes the taxon "beyond the limits of variation with Akodon s.s." The peculiarity of a single
pair of prostate glands in Thaptomys nigrita, demonstrated by Voss and Linzey (1981), was not esteemed by Reig,
albeit its presence in Microxus bogotensis was deemed significant (Reig, 1987, p. 360). This derived character, found
only in Thaptomys nigrita and Microxus bogotensis (a species questionably identified with Microxus) in a sampling
of 59 species representing 35 genera of South American cricetids, cannot be judged arbitrarily. In addition, characters
of Thaptomys such as the short tail, heavy skull, ridged parietals, short, thick rostrum with long nasal bones, wide
interorbital region, squared braincase, relatively small molars, long powerful proodont incisors, and the diploid
chromosome number 52, are singly or in combination non-Akodon.

13 Hesperomys dolichonyx Philippi, 1896, treated as a subspecies of Akodon andinus by Osgood (1943, p. 179) is
not an Akodon (sensu strict o).

14 Blarinomys breviceps, type and only species; measurements from Abravaya and Matson (1975, p. 4), include
total length 66 142.4 (129-157) 11, 29 152.1 (143-161) 8, sexes combined, 146.5 (129-161) 19; mean tail, sexes
combined, 42.2; mean HB (= mean TL minus mean tail) 104.3; tail : HB, sexes combined, 40.4.

15 Abrothrix xanthorhinus; regarded as a subspecies of olivaceus by Yariez et al. (1979).

16 Abrothrix longipilis Waterhouse, 1837, type species (fig. 5, molars). Abrothrix Waterhouse, 1837, is listed as a
subgenus of Akodon by Cabrera (1961, p. 454). Reig also treats Abrothrix as a subenus of Akodon with recognized
species hershkovitzi, illuteus, lanosus, longipilis, mansoensis, sanborni, and xanthorhinus.

Abrothrix Waterhouse, if restricted to A. longipilis, A. sanborni, and possibly A. illuteus, has the semblance of a
valid genus separable from all other genera. The baculum of the first two species is simple, exceptional for sigmo-
dontines including all akodonts, but obviously derived from the complex type. It is poles apart from the simple
peromyscine type derived independently from a complex type (but see Carleton, 1980). Akodon longipilis and A.
sanborni also share similar karyotypes (2n = 52, FN = 58). That of A. illuteus is the same (Liascovich et al., 1989),
but morphology of its baculum is unknown. The karyotype of Akodon xanthorhinus is characterized by 2n = 52,
FN = 56. Those of A. lanosus, A. hershkovitzi, and A. mansoensis are unknown.

FIELDIANA: ZOOLOGY

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FIELDIANA: ZOOLOGY

Characters (figs. 2-6)

Morphometric (tables 1, 2)— External measure-
ments by various collectors recorded here are not
strictly comparable and some may be misleading;
cranial measurements are by the author. Com-
bined head and body length between 73 and 1 1 7(?);
tail between 49(?) and 85, tail relative to head and
body length between 52% and 94%; hind foot to
longest toe with claw between 15(?) and 26; ear,
usually hidden in fur, between 12 and 15; weight
probably between 1 5 and 22 grams; greatest skull
length, 22-27; condylobasal length, 20.1-24.8;
interorbital constriction, 3.8—4.9; alveolar length
of upper molar row, 3.3—4.6

External— Upper parts of body from tip of ros-
trum to tail base dominantly dark brown (excep-
tionally dominantly buffy or ochraceous), the hairs
blackish (eumelanin) with a single narrow subter-
minal ochraceous or buffy (pheomelanin) band,
length middorsally 5-10 mm; contrastingly col-
ored pheomelanin eye ring and dominantly or en-
tirely pheomelanin snout sometimes present;
cheeks like crown or contrastingly ochraceous;
whitish postauricular patch absent, mystacial vi-
brissae short, when laid back extending to between
eye and middle of ear base. Sides of body like back
or with pheomelanin subterminal band of hairs
broader and usually more saturate, to ochraceous
orange, lateral stripe present or absent. Underparts
from chin to tail base weakly to sharply defined
from sides of body, the hairs dominantly ochra-
ceous or bufTy superficially, the slaty basal portion
showing prominently at the surface; chin like throat
or chest, rarely contrastingly whitish. Tail more or
less uniformly colored to sharply bicolor, thinly
pilose, the scales fully exposed or partially con-
cealed. Hind feet with upper surface thinly to
thickly covered with stiff ochraceous to buffy or
whitish hairs, the scaly brown skin fully exposed
to nearly entirely concealed; digital bristles vary-
ing from short or thin, the claws fully exposed, to
long, thick, nearly completely concealing claws;
fifth digit, less claw (s.u.), extending to base of first,
second, or rarely third phalanx of fourth digit; first
digit with or without claw never extending beyond
base of second digit; claws of middle digits from
2 to 4 mm long, extending 1 .5-3 mm beyond pha-
langeal tips. Extension of webbing between toes
and fingers from slightly proximad to slightly dis-
tad of base of second phalanges; two middle toes
and two middle fingers sometimes syndactylous;
thumb with nail not extending to base of second
digit.

Remarks on Tegumentary Coloration (fig. 2) —

The primitive agouti cover-hair pattern for the
Akodon boliviensis group and all other akodonts
is characterized by a single pheomelanin band be-
tween eumelanin tip and eumelanin basal portion
of the hair. The typical ancestral mammalian agouti
pattern with two pheomelanin bands on the ter-
minal portion of the hair was modified by reduc-
tion and elimination of one pheomelanin band in
the dorsal pelage, and reduction to nearly complete
or complete elimination of the terminal eumelanin
band in the ventral pelage. This may be accom-
panied in some species by expansion of the eu-
melanin base of the hairs. The evolutionary trend
in others may be toward partial or complete dom-
inance on both upper and lower parts of the body
by either of the two melanins. Markings, or con-
trasted chromogenetic fields such as eye rings, snout
tip, chin, postauricular patches, pectoral streak,
and spotting, vary from saturate (reddish or
orange) to bleached (buffy or whitish) monochro-
matic pheomelanin. Markings in dominantly
pheomelanin akodonts may be either eumelanin
(brownish) or a contrasted tone of pheomelanin.

Primitive sensory hairs, not the same as the
strictly mammalian cover hairs, were inherited
from the reptilian ancestry. They appear as vi-
brissae, guard hairs, interscutellate tail hairs, and
digital bristles. Such hairs are typically mono-
chromatic eumelanin, often bleached to grayish or
white. Variation and evolution of mammalian teg-
umentary colors, termed metachromism, are dis-
cussed in detail by Hershkovitz in several publi-
cations, the first in 1968, the most recent in 1988.

Cranial (figs. 3, 4) — Smooth, without sagittal,
lambdoidal, occipital, interorbital, or temporal
crests, ridges, or beading; dorsal contour from na-
sal tips to parietal bones broadly arced to nearly
plane; nasal bones tapered distally, length about
1 0% shorter to 1 7% longer than frontal bone at
midline suture, tips rounded to pointed, not flared
or trumpet-shaped, and separated from and ex-
tending distad of premaxillary bone; sides of in-
terorbital region nearly parallel to concave with
divergence posteriorward; rostrum in front of op-
posing zygomatic plates from slightly wider to
slightly narrower than width of interorbital region
at constriction; braincase moderately inflated,
rarely globose, the supraoccipital bone rounded
above, rounded to nearly plane behind, occipital
condyles not projected behind vertical plane of
supraoccipital bone; zygomatic arches convergent
anteriorly, the bones delicate, the jugal often
threadlike; zygomatic plate narrow, more or less

HERSHKOVITZ: NEW SPECIES OF AKODON

5 4

SA1 ] N PROCESS

EUMELANIN PATHWAY

blackish-brown 2 3

PHEOMELANIN PATHWAY
2 reddish-yellow

saturate saturate
monochromic dichromic
pheomelani n

modi f ied
agouti

modified
agouti

saturate

monochromic

eumel ani n

AGOUTI

(with
eumel ani n

base)
Fig. 2. Saturation of agouti cover-hair through eumelanin (blackish-brown) pathway and pheomelanin (reddish-
yellow) pathway. In model shown, only terminal portion of hair is banded and subject to saturation. The basal portion
is saturate melanin. Two or three pheomelanin bands separated by eumelanin bands is regarded as the primitive
mammalian pattern. The modified agouti (2) hair of the eumelanin pathway is primitive for dorsum and sides of
akodonts, the same or the modified agouti (2) of the pheomelanin pathway is primitive for the underparts, certain
markings, rarely for dorsum and sides. Saturation may proceed stepwise in either pathway, as shown here, or may
leap from agouti to stage 3, 4, or 5. The basal portion of the hair is chromogenetically independent from the terminal
portion. It is also subject to saturation and bleaching. The rates of change are usually uneven, but insofar as known
the direction of change is irreversible. (Adapted from Hershkovitz, 1968.)

upright or reclined, little to hardly projected an-
teriorly beyond antorbital foramen; incisive (an-
terior) palatal foramina long, extending back to
anterior plane of m1 or beyond to midplane of
tooth, the foramina expanded anteriorly, contract-
ed posteriorly but always wider than mesoptery-
goid fossa at palatal border; palate extending to
posterior plane of m3 or slightly beyond; molar
rows parallel-sided to slightly convergent behind,
palatal width between molar rows greater than
length of first molar; sphenopalatine vacuities usu-
ally widely expanded but sometimes narrowed to

short slits or almost completely absent; tympanic
bullae not conspicuously inflated.

Dental (fig. 5)— Upper incisors orthodont to
opisthodont, never proodont, enamel pigmented
yellow to orange, length in straight line from sym-
physis subequal to length of m1-2 but less than that
ofm1-3.

Upper molars moderately hypsodont, unworn
crowns crested or bilevel. First molar with an-
teromedian flexus usually deeply penetrant, some-
times not defined, the procingulum biconulate with
anterolabial and anterolingual conules usually well

10

FIELDIANA: ZOOLOGY

defined, sometimes not defined: talon and trigon
minus procingulum subequal in width and length;
paralophule (pseudomesoloph) present, often fused
with metalophule if present. Second molar shorter
than first minus procingulum, otherwise similar.
Third molar as large as, to slightly smaller than,
talon of second molar, hypoflexus and postero-
flexus shallow but often persistent in worn tooth,
the latter as an island.

Lower molars moderately hypsodont, the first
molar with staggered cusps, procingulum slightly
larger than half bulk of trigonid, anteromedian-
flexid penetrant, exceptionally absent, anterolabial
and anterolingual conulids well defined, excep-
tionally not defined (mainly in A. mollis class),
protolophid and posterolophid present, some-
times not well defined. Second molar with trigonid
and talonid subequal in length and breadth; cusps
of opposite sides staggered or opposed; protolo-
phid, mesolophid, and posterolophid present, ec-
tolophid weakly defined or absent. Third molar
narrower but longer than talonid of second molar;
trigonid and talonid subequal; cusps usually stag-
gered; posteroflexid suppressed.

Remarks on Dental Morphology and Terminol-
ogy (figs. 20-22) — Unworn akodont molars are
hypsodont (high crowned), the crowns bilevel,
sometimes crested, with well defined cones (-ids),
conulcs (-ids), lophs (-ids), lophules (-ids), and styles
(-ids). The first (anterior) molar is ovoid or oblong,
larger, and more complicated than the others. This
is mainly due to expansion and differentiation of
the anterior portion of the cingulum, termed pro-
cingulum, into a functional and similitudinal re-
placement of the lost fourth premolar. The second
molar, effectively wedged between first and third,
is more nearly square, its procingulum abbrevi-
ated. The reduced third molar erupts last, the erup-
tion sometimes delayed past weaning.

Erosion of the molar crown topography is rapid.
At the time of the individual's maturity, the crown
surface may already have been ground to a dished
eight-shaped pattern with few of the cingular ele-
ments persistent or clearly defined.

The enamel pattern of sigmodontine molar
crowns was described and figured by me in 1 944,
refined with additions in 1962. The diagrammatic
pattern and terminology for coronal elements were
adopted by various students of New World cricetid
dentition, most recently by Reig ( 1 980, 1 987). The
present plan replaces my term "enamel fold" with
Reig's "flexus" each with a distinguishing prefix
derived from the name of the enamel element de-
fined by it.

Terminology for sigmodontine molar elements
is. in all cases, based on the traditional and still
useful Cope-Osborn concept of molar evolution.
The similar terms used for upper and lower molar
elements distinguished by the suffix "-id," how-
ever, do not imply homology between them. This
defect of the Cope-Osborn terminology has been
explained elsewhere (Hershkovitz, 1 970). The sys-
tem based on homologies of nonrodent crown ele-
ments has yet to be effectively extended to the
special molar crown patterns of sigmodontines and
rodents generally.

Projection of the upper incisor with reference to
the basal incisive plane varies from opisthodont
to orthodont and proodont (fig. 22).

Karyotypic— The diploid chromosome number
is known for 8 of the 13 species of the Akodon
holiviensis class (table 1). The number varies from
34 in puer and caenosus, 38/37 in azarae, 40 in
alterus, holiviensis, and tucumanensis, to 42 in
Akodon lindherghi (Svartman, pers. comm.).

Remarks— The distinctive characters of the two
new species described below extend the erstwhile
parameters of the Akodon holiviensis class consid-
erably beyond what they would be without them.
A better known A. sanctipaulensis might indicate
generic separation.

Akodon mollis Size Class

An alphabetical list of the larger species of Ako-
don Meyen, 1833 (sensu stricto) follows. Taxa in
parentheses may be subjective synonyms, subspe-
cies, or nearest related species of the apposed taxa.
The known diploid chromosome numbers, from
24 (cursor) to 44 (dolores, molinae, serrensis), in-
dicate that the class is heterogeneous. Identifica-
tions of the specimens listed by name have not
been verified against the type specimens. Omitted
from the list are species questionably referred to
Akodon by authors, and others properly referred
to the subgenera or genera Ahrothrix Waterhouse,
1837; Chroeomys Thomas, 1916; Chalcomys
Thomas, 1916; Deltamys Thomas, 1917; Hypsi-
mys Thomas, 1918; Microxus Thomas, 1909;
Thalpomys Thomas, 1916; Thaptomys Thomas,
1916. Skull and molars of Akodon cursor arc fig-
ured (figs. 3-5) as representative of the A. mollis
class.

An antcromedianflexus (-id) is probably present
in all bonafide species of the Akodon mollis size
class. In most type specimens of the species, how-
ever, presence or absence of the character cannot

HERSHKOVITZ: NEW SPECIES OF AKODON

11

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FIELDIANA: ZOOLOGY

Fig. 4. Skulls and mandibles, left side of same specimens shown in Figure 3: a, Akodon boliviensis; b, Akodon
cursor c, Akodon andinus dolichonyx; d, Bolomys lasiurus. White bar = 1 cm.

be ascertained because of the excessive coronal
wear of their first molars.

altorum Thomas, 1913 (see mollis)
cursor Winge, 1888 (includes montensis)

dolores Thomas, 1916 (includes molinac Con-

treras, 1968)
fulvescens Hershkovitz, 1940 (see mollis)
fumeus Thomas, 1 902 (see mollis)
glaucinus Thomas, 1919 (see varius)

HERSHKOVITZ: NEW SPECIES OF AKODON

13

Fig. 5. Right upper and lower left molars of same specimens except c and d, shown in Figures 3 and 4: a, Akodon
boliviensis; b, Akodon cursor, c, Abrothrix longipilis (fmnh 23123); d, Bolomys lasiurus (fmnh 28336). White bar =
1 mm.

hunteri Thomas, 1917

leucogula Miranda Ribeiro, 1905 (originally
proposed as "[Hesperomys] (A[kodon]) ser-
rensis var. leucogula)

markhami Pine, 1973

molinae Contreras, 1968 (see dolores)

mollis Thomas, 1894 (includes altorum Thom-
as, 1913, fumeus Thomas, 1902, fulvescens
Hershkovitz, 1940)

montensis Thomas, 1913 (see cursor)
neocenus Thomas, 1919 (see varius)
pervalens Thomas, 1925 (see serrensis)
serrensis Thomas, 1902 (includes pervalens

Thomas, 1925)
simulator Thomas, 1916 (see varius)
surdus Thomas, 1917
tartareus Thomas, 1919 (see varius)
toba Thomas, 1921 (see varius)

Fig. 6. Akodon lindberghi: Cheiridia, dorsal and ventral surface of right hand (upper) and foot (lower). Drawn
from dry skin, partially reconstituted by moistening; volar pads are semidiagrammatic. Black bar = 5 mm.

14

FIELDIANA: ZOOLOGY

Fig. 7. Skulls of Akodon: Dorsal and ventral aspects of a, Akodon sanctipaulensis (fmnh 94516, holotype);
b, Akodon lindberghi (fmnh 128292, holotype); c, Akodon azarae (fmnh 27619). White bar = 1 cm.

varius (specific synonyms or nearly related
species include glaucinus, neocenus, simula-
tor, tartareus, toba)

Akodon lindberghi, new species
(Matosa akodon)

Holotype1— Adult male, skin and skull, Field
Museum of Natural History no. 128292; collected
7 August 1986, by Philip Hershkovitz and Scott
Lindbergh; original number 9589.

Cotypes— Adult males, skin and skulls, fmnh

1 Deposited in the Museu Nacional, Rio de Janerio,
Brazil.

nos. 128293, 128295, 128297, 128298; skin only
128294; juvenal female, skin and skull, fmnh no.
128296; all collected by Philip Hershkovitz and
Scott Lindbergh.

Etymology— Named for Scott Morrow Lind-
bergh, without whose devoted and unstinted as-
sistance this species would not have been discov-
ered.

Type Locality— Matosa, a former fazenda now
part of the Parque Nacional de Brasilia, about 20
km NW of Brasilia, Distrito Federal, Brazil; alti-
tude about 1,100 m.

Distribution (fig. 1)— All known individuals
were captured within a half hectare plot on the
periphery of an extensive wet valley side grassland

16

FIELDIANA: ZOOLOGY

Fig. 8. Skulls and mandibles of same specimens as shown in Figure 7. a, Akodon sanctipaulensis, right side of
skull and right mandible reversed; b, Akodon lindberghi, right mandible reversed; c, Akodon azarae. White bar = 1
cm.

(campo limpo) cerrado in the Parque Nacional de
Brasilia, Brasilia, DF, Brazil. For a description of
cerrado landscape habitats in the Brasilia area see
Alho(1982).

Diagnostic Characters— Moderately sized
small-footed member of the Akodon bolivicnsis
class; tail about 70%, hind foot about 21% of
combined head and body length; interorbital re-
gion extremely broad, mean 20% of greatest skull
length, 43% of braincase width, incisive foramina
extremely long (mean 6.2 mm); strongly reclined
zygomatic plate extremely narrow antero-poste-
riorly, about 39% of interorbital breadth, and barely
projecting beyond interorbital foramen as seen

from above; auditory bullae small; diploid number
of chromosomes, 42.

Measurements— See Tables 1-3.

Comparisons— Long, lax pelage, extremely nar-
row, strongly reclined interorbital plate, and dip-
loid chromosome number 42 distinguish A. lind-
berghi from all other species of the Akodon
boliviensis group.

Characters (figs. 6-10)

External— Coat thick, hairs of upper and lower
surface of body long, lax; dorsal surface from tip
of rostrum to tail base dark olivaceous agouti, the

HERSHKOVITZ: NEW SPECIES OF AKODON

17

Fig. 9. Molars, right upper and lower left of same specimens shown in Figures 7 and 8. a, Akodon sanctipaulensis;
b, Akodon lindberghi; c, Akodon azarae. White bar = 1 mm.

individual hairs 8-10 mm long middorsally, with
one narrow subterminal buffy (pheomelanin) band;
mystacial vibrissae short, when laid back extend
from between eyes to middle of ears; sides of body
brighter, the pheomelanin band broader; lateral
line absent; cheeks like sides. Underparts from
chin to tail base not sharply defined from sides,
hairs buffy to ochraceous terminally, slaty basally,
the color broadly exposed at the surface. Tail dark
brown above, little paler beneath, thinly pilose,
the scales fully exposed. Hind feet (fig. 6) thinly
covered with grayish or buffy hairs above, the
brown scaly skin exposed; fifth digit less claw ex-
tending to base of second phalanx of fourth digit;
first digit less claw extending to base of first pha-

lanx of second digit; claws comparatively thick,
moderately curved, length (middle pair) about 4
mm, of shortest (first digit) about 3 mm, all ex-
tending 2 mm beyond tip of distal phalanges; dig-
ital bristles thin, short, not concealing claws; fore-
feet small, thick, claws extending about 1.2-1.4
mm beyond phalangeal tips. Webs between mid-
dle digits of hands and feet extending from slightly
distad to slightly proximad to base of second pha-
langes; plantar tubercles large, the palmar post-
digitals apparently adapted for clutching grass
stems and slender twigs.

Cranial (figs. 7, 8) — Bones thin, translucent;
dorsal contour nearly plane; paired anterior frontal
sinuses notably inflated; braincase rounded but

18

FIELDIANA: ZOOLOGY

Fig. 10. Akodon lindberghi (fmnh 128292): Glans penis, partially reconstituted from dry tissue and cleared in
K.OH to reveal baculum. A, baculum from ventral aspect; B, three quarter ventral view of cartilaginous bacular digits;
C, lateral view of baculum. a, base of proximal bony shaft. See Figure 1 1 for identification of other parts. Black bar
= 1 mm.

not globular; interparietal bone comparatively long
anteroposteriorly; interorbital region extremely
wide relative to greatest skull length; zygomatic
plate extremely narrow, reclined, hardly or not
projecting beyond antorbital foramen as seen from
above; width of rostrum in front of zygomatic plates
less than least interorbital breadth; zygomatic
arches extremely weak, convergent anteriorly; fo-
ramen magnum positioned forward, the occipital
condyles not produced behind vertical plane of
supraoccipital bone; auditory bullae comparative-
ly small; mesopterygoid fossa comparatively wide,
parapterygoid fossa as wide proximally, becoming

wider distally; sphenopalatine vacuities widely
open; combined foramina ovale and spinosum
crossed by pterygoid bridge.

Upper teeth (fig. 9) — Incisors more often ortho-
dont than opisthodont, enamel pigmented yellow
to orange; molar rows parallel-sided to slightly
convergent behind, crowns moderately hypso-
dont, persistently cuspidate. First molar with pro-
cingulum slightly more than half bulk of trigon,
anterior median fold or fiexus deeply penetrant
and persistent in worn tooth, the anterolingual and
anterolabial conules well defined; anteroloph
moderately developed; paralophule present in ab-

HERSHKOVITZ: NEW SPECIES OF AKODON

19

Fig. 1 1 . Glans penis, partially reconstituted from dry tissue and cleared in KOH to reveal baculum. A, Akodon
boliviensis (fmnh 75494), ventral aspect; B, Bolomys lasiurus, ventral aspect; C, Bolomys lasiurus, lateral aspect, a,
proximal baculum or bony shaft; b, lateral bacular process or lateral cartilaginous digit; c, distal baculum or middle
cartilaginous digit; d, outer crater; e, inner crater; f, dorsal papilla. Black bar = 1 mm.

sence of mesoloph; posteroloph short but well de-
fined. Second molar like first but shorter, the pro-
cingulum reduced; talon narrower than trigon.
Third molar less than half bulk of second; talon
less than bulk of either cusp of trigon; hypoflexus
shallow, obliterated with wear, shallow postero-
flexus more persistent.

Lower teeth (fig. 9). Incisors with enamel paler
than that of corresponding upper incisors. First
molar with procingulum slightly more than half
bulk trigonid; anteromedianflexid penetrant, an-
terolingual and anterolabial conulids well defined;
accessory features include protolophid, protosty-
lid, ectolophid, ectostylid usually fused with ec-
tolophid, mesostylid, anterolophid, mesolophid,
metalophid, metastylid and posterolophid often
fused with entoconid; talon wider than trigon and
subequal in bulk to trigon plus procingulum; cusps
staggered. Second molar with protolophid, ecto-
stylid, mesostylid, posterolophid present, ectolo-

phid weakly defined or absent; lacking are antero-
lophid, protostylid, and mesolophid; trigonid and
talonid subequal in length and breadth; cusps
slightly staggered. Third molar with hypoflexid
present often as a midcoronal island; posterolo-
phid almost vestigial, usually undefined in worn
tooth, posteroflexid suppressed; protolophid greatly
reduced; talonid narrower than trigonid but sub-
equal in bulk; cusps staggered.

Karyotype— The diploid number of 42 chro-
mosomes for the species was determined from bone
marrow preparations of specimens fmnh 1282953
and 1282962 by Maria Svartman of the Univer-
sidade de Sao Paulo, Sao Paulo. Her formal de-
scription of the karyotype awaits publication of
the name Akodon lindberghi.

Genitalia (fig. 10)— The dried penis of the ho-
lotype (fmnh 128292), preserved on the dry skin,
was detached and partially reconstituted with water
and by clearing in potassium hydroxide (KOH);

20

FIELDIANA: ZOOLOGY

B

Fig. 12. Abrothrix longipilis: Glans penis, partially reconstituted from dry tissue and cleared in KOH to reveal
baculum. A, dorsal aspect of proximal baculum; B, ventral aspect showing urinary meatus and ventral lappet; C,
lateral aspect; a, enlarged section of penial skin with spines; b, ventral lappet; c, ventral. Black bar = 1 mm for
baculum, .5 mm for spines.

the bone and cartilage were then stained. Nearly
all soft parts of the glans were lost. The baculum
itself (fig. 10) resembles that of Akodon boliviensis
(fig. 1 1A) more nearly than that of Bolomys lasi-
urus (figs. 1 1 B,C) and differs widely from that of
Abrothrix longipilis (fig. 12). Detailed descriptions
of the complete glans penis of Akodon boliviensis,
and some related species including those of A.
azarae, Bolomys lasiurus, and other sigmodon-
tincs, are given by Hooper and Musser (1964).

Specimens Examined— Total 7. Matosa, Parque Na-
cional de Brasilia, Brasilia, DF, 7 (fmnh, holotype and
6 cotypes).

Akodon lindberghi and
the Nomen Nudum
Plectomys paludicola

A report by Borchert and Hansen (1983) on the
effects of flooding and wildfire on sigmodontincs
in the Parque Nacional is of particular relevance
to the probable history of Akodon lindberghi. Their
study areas, .74 hectares each, denominated un-
burncd A, and burned B, were located 1 km apart
in the valley side wet campo behind the old Matosa
farmhouse, now type locality of A. lindberghi. The
147 mice captured during the study included, in

HERSHKOVITZ: NEW SPECIES OF AKODON

21

decreasing order of abundance, Bolomys (their
Zygodontomys) lasiurus, 42%; Oxymycterus sp.
(their O. roberti), 31%; their Plectomys paludicola,
20%; Oryzomys "eliurus," .05%; Akodon cursor
(their Akodon arviculoides cursor), .0 1 %. Their ob-
servations focused on the most abundant species,
Bolomys lasiurus, Oxymycterus sp., and the so-
called Plectomys paludicola.

The last binomial is puzzling. To my knowledge,
neither the generic nor specific name of Plectomys
paludicola has ever been described. The name,
with no mention of holotype, no indication of a
distinguishing character, reference to author, or
where or when published, was used by Borchert
and Hansen (1983). It was also used in two un-
published student theses on the ecology of cerrado
rodents shown me in Brasilia, and in a publication
by Alho et al. (1986, pp. 447, 45 1-452, 454). Not-
withstanding, the mice conceived as Plectomys
paludicola must be real, and their attributes, in-
cluding habitat preference, relative abundance,
food habits, and circadian rhythms (Borchert &
Hansen, 1 983) cannot be dismissed for having been
reported under an unrecognized name. In any
event, all authors agree that mice they called Plec-
tomys paludicola were found only in the Parque
Nacional de Brasilia, specifically the Matosa area.

Trapping by me and Scott Lindbergh (fig. 13)
in cerrado habitats of the Parque Nacional de Bra-
silia during August 1986 yielded the following sig-
modontines (number of specimens in parenthe-
ses): Bolomys lasiurus (12), Oxymycterus sp. (7),
Akodon lindberghi (7), Oryzomys subflavus (5),
Thalpomys sp. (2), and Thalpomys lasiotis(l). The
last binomial takes priority over Akodon rein-
hardti proposed by Langguth ( 1 975, p. 45) for Ha-
brothrix lasiotis Winge, 1887, p. 29, and Thal-
pomys lasiotis Thomas, 1 9 1 6, p. 339, not the Mus
lasiotis of Lund (1840, p. 55).

The above mentioned species, except Akodon
lindberghi, are widely distributed throughout the
central Brazilian cerrado. The seven specimens of
Akodon lindberghi were captured within the Bor-
chert and Hansen (1983) study area A, still iden-
tifiable at the time by their grid marking stakes.
At least two of the mice were trapped in daylight.

Thalpomys lasiotis, Oryzomys subflavus, and the
erstwhile undescribed Akodon lindberghi, are area
species not mentioned by Borchert and Hansen.
Habitat, distribution, demography, and possibly
habits attributed to Plectomys paludicola point
more certainly to identity of that mouse with Ako-
don lindberghi than to either of the others, which
are distinctive and too well known to be confused
with anything else. Furthermore, the number of

Fig. 1 3. Matosa habitat of Akodon lindberghi in Par-
que Nacional de Brasilia, DF; Scott Lindbergh is shown
holding live-trapped Oxymycterus sp. with right hand
and Oryzomys subflavus with left hand, both species tak-
en in the same trapline with Akodon lindberghi.

Akodon lindberghi captured by us holds a roughly
proportional relationship to that of our capture of
Bolomys lasiurus and Oxymycterus sp., compa-
rable to the proportional number of Bolomys, Ox-
ymycterus, and Plectomys paludicola trapped by
Borchert and Hansen (1933) in the same general
area. The fact that the distinctive Matosa akodon
lacked a valid scientific name at the time may have
invited the use of the unpublished manuscript name
Plectomys paludicola, of an anonymous author,
possibly Joao Moojen (1965), the discoverer of
Juscelinomys candango of the same region.

Population Dynamics

All cerrado habitats in Brasilia, DF, including
the one occupied by Akodon lindberghi, have been
thoroughly investigated during the last decade by
students of mammalian ecology and demography
including, among others, Mello and Moojen ( 1 979),
Borchert and Hansen ( 1 983), da Fonseca and Red-
ford (1984), Redford and da Fonseca (1986), Mares

22

FIELDIANA: ZOOLOGY

et al. (1986), Nitikman and Mares (1987), Alho
(198 l),Alho and Pereira (1985), Alhoetal.( 1986),
and Alho and Souza (1982). As noted above, two
of the cited references mention the nomen nudum
Plectomys paludicola; Borchert and Hansen ( 1 983,
p. 237) provide more information than mere name
and locality. Excerpts from their paper are quoted
below.

Plectomys paludicola

had a narrow habitat breadth and an even narrower
microhabitat preference in wet campo. While the cap-
ture distributions of the other two [study] species [Bo-
lomys lasiurus, Oxymycterus "roberti"] on area A ex-
panded and contracted during the study, that of P.
paludicola remained remarkably constant even though
its population level fluctuated considerably. Very few
individuals were captured at Paspalum [spp. grasses]
stations 20 m from the border [of the campos] even
after the flood water receded. Apparently, this species
travelled along the border because of the frequency
with which individuals were captured on opposite
borders of the marsh on consecutive nights, but never
in the central portion. Nor were captures common in
[the introduced grass] Hypahrrenia even though food,
at least grass seed, was far more abundant in this area
than along the Paspalum border.

Preceding the above statements, Borchert and
Hansen (1983, p. 237) note that unlike the more
abundant Oxymycterus ""robertr and "Zygodon-
tomys" lasiurus, which were not limited in move-
ments by flooding, their Plectomys paludicola

avoided standing water, yet its own movements were
only partially influenced by flooding. Several lines of
evidence suggest that this species moves to and from
wet campo seasonally, departing after the beginning
of the rainy season and returning when the marsh
begins to dry. First, individuals disappeared from area
A by April even though the preferred microhabitat
did not flood. Second, specific attempts to snap trap
this species during the rainy season on unburned
mounds surrounded by water and along the wet campo
border were fruitless, while upland burned and un-
burned low-tree and scrub savanna yielded a number
of individuals. Third, at least one marked male from
area A was snap trapped 500-600 m from the grid in
bordering low-tree and scrub savanna, 100 m from
the nearest wet campo. Finally, we noted a sudden
increase in the abundance of this species in wet cam-
pos that were beginning to dry suggesting an influx of
individuals from other habitats.

Response to wet campo, altered by an intensive
wildfire in late 1978 that burned 60% of the Par-
quc, also differed significantly among the species.
According to Borchert and Hansen (1983, p. 238),
Bolomys lasiurus and Plectomys paludicola, both
seasonal inhabitants of wet campo, recolonized

area B not long after the fire. Oxymycterus roberti
was continuously present in the marsh after the
fire. Plectomys paludicola, however, "was the last
species to appear in the burned area."

Survival Status

What is known of Akodon lindberghi, granting
identity with Plectomys paludicola, suggests that
its restricted geographic range may be too small
for survival of the species should the habitat suffer
exceptionally severe and long term alteration by
flood and fire. Addition of competition by the larg-
er, ubiquitous, and resilient Bolomys and Oxy-
mycterus can result in catastrophic effects. Skulls
and molars of Bolomys lasiurus are shown in Fig-
ures 3-5.

Our trapping in 1986, and that of Borchert and
Hansen (1983) in the wet valleyside grassland
{campo limpo) cerrado in the Parque Nacional un-
covered a total of eight sigmodontine species. Gal-
lery forest mice in Brasilia are distinct and of no
consideration here. Trapping during the same pe-
riod in 1986, and again in 1988, in surrounding
unprotected campo limpo drastically modified by
excessive burning, agriculture, and cattle grazing
indicated that ultimately only Bolomys and Calo-
mys survive there. Both genera include plague or
ratada species, which are the principal reservoirs
of pathogenic viruses. In contrast, mice as deli-
cately balanced ecologically as Akodon lindberghi,
and the fossorial oxymycterine Juscelinomys can-
dango Moojen (1965), the primary object of our
trapping, may not survive in altered habitats. The
latter species was discovered in 1960 at the time
its natural cerrado niche was being destroyed for
accommodation of human facilities. The animal
has not been seen since despite intensive search.

The Matosa mouse is neither fossorial nor cryp-
tic. Its existence, almost certainly confined to a
small plot of campo limpo in the Parque Nacional
de Brasilia, is precariously balanced between strong
competitors and an undefined microhabitat that
narrows progressively with each overall environ-
mental modification.

Akodon sanctipaulensis, new species
(Sao Paulo marsh akodon)

Holotype— Adult female, skin and skull, fmnh
no. 945 1 6, collected 1 3 July 1 96 1 , by A. M. Olalla,
original number 1 166.

Type Locality— Primeiro Morro, Sao Paulo,
Brazil.

Distribution (fig. 1)— Known only from the

HERSHKOVITZ: NEW SPECIES OF AKODON

23

north bank of the Rio Juquia and Rio Eta (between
24°00'-24°25'S, 47°35'^8°10'W) on the Atlantic
coastal plain at the base of the Serra do Mar, ex-
treme southeastern Sao Paulo State, Brazil.

Diagnostic Characters— Tail relatively long,
[ about 77% of head and body length; average size
I of hind foot about 24 mm or extreme for the .-1.
Iboliviensis class; braincase globular, interorbital
region short, wide; zygomatic arches extremely
I delicate, convergent; nasals long, ratio of length to
I frontal bone at midline high, as in Abrothrix rather
[than Akodon (s.s.)\ upper incisors extremely short,
length from symphysis less than combined length
[of m' -, enamel pale orange to pale yellow; pro-
cingulum of first upper molar biconulate, of lower
uniconulate or biconulate; m2 with mesolophid
present; m, with posterolingual flexid persistent,
usually as island in worn tooth; complete eruption
of upper and lower third molars delayed to post
weaning juvenal or early subadult stage.

Measurements— See Tables 1, 2, and 4.

Comparisons— Large feet, globular braincase
with short interorbital region, relatively long na-
sals, short incisors, combine to distinguish Akodon
sanctipaulensis from equal-aged individuals of all
other species of Akodon.

Characters (figs. 7-9, 14)

External (fig. 14) — Pelage dense, the hairs 7-9
mm long middorsally; dorsal surface from rostrum
to tail base nearly uniformly blackish, the hairs
blackish (eumelanin) with a single narrow buffy
(pheomelanin) subterminal band broader on an-
terior than on posterior half of trunk; sides of trunk
with pheomelanin band wider, more saturate, lat-
eral line absent; cheeks like crown, mystacial
vibrissae when laid back extend from eye to mid-
ear base. Underparts not defined from sides, dom-
inantly ochraceous orange, the pheomelanin ter-
minal portion and eumelanin basal portion of hairs
not banded, chin not contrastingly whitish. Tail
brown above, slightly paler beneath, hairs short,
the scales fully exposed. Hind feet thinly covered
grayish or buffy, brown of scaly skin fully exposed;
fifth digit less claw extending to base of first pha-
lanx of fourth digit, first digit less claw extending
to base of second digit; claws moderately curved.

of middle digits about 4.5 mm long and extending
about 1 mm beyond phalangeal tips; digital bris-
tles short, thin, not concealing claws. Webbing of
middle digits of hands and feet usually extending
from slightly proximad to slightly distad of second
phalanges; in fmnh 94573, middle digits of right
hand completely syndactylous, of left hand united
to base of distal phalanges, middle digits of right
and left feet entirely syndactylous, webbing of ad-
jacent digits extend to base of second phalanges
(fig. 14).

Cranial (figs. 7, 8)— Bones smooth, delicate,
translucent, dorsal contour with globular brain-
case raised above long, pointed slender rostrum;
paired midfrontal sinuses notably inflated, ante-
rior frontal sinuses less inflated; zygomatic plate
reclined but anterior border projecting, as usual,
beyond antorbital foramen as seen from above;
interorbital region short, wide, the sides strongly
divergent; width of rostrum in front of zygomatic
plates less than least interorbital width; zygomatic
arches extremely weak, convergent; mesoptery-
goid fossa comparatively wide; parapterygoid fos-
sa wider, with greatest expansion behind; ptery-
goid bridge complete; sphenopalatine vacuities
absent to present and widely expanded; auditory
bullae well inflated; interparietal bone little de-
veloped.

Dental (fig. 9) — Upper incisors extremely short,
opisthodont; upper and lower molars essentially
as in the Akodon boliviensis class, except procingu-
lum of m, uniconulate or weakly biconulate as in
holotype, incisor enamel extremely pale.

Karyotype — Unknown.

Remarks— Available skulls are of juvenals,
young adults, and a skin without skull (fmnh
95413) of an old male. Procingulum of first lower
molar is uniconulate in one juvenal and one adult,
biconulate in four specimens. Third molar erup-
tion in the juvenals appears to be retarded com-
pared with dental eruption in comparably aged
juvenals of other akodonts.

The distinctive characters of Akodon sanctipau-
lensis suggest those typical of juvenals or newborn.
These traits, however, are not shared with com-
parably aged young of all other Akodon species
examined. The 10 specimens of sanctipaulensis
were taken by the same collector in the same places
at the same times with 91 specimens of Akodon
cursor, and 2 of a third unidentified species of

Fig. 14. Akodon sanctipaulensis: Cheiridia, dorsal and ventral surface of right hand (upper) and foot (lower).
Drawn from dry skin, partially reconstituted by moistening; digits 3 and 4 of hands and feet are syndactylous, volar
pads are semidiagrammatic. Black bar = 5 mm.

HERSHKOVITZ: NEW SPECIES OF AKODON

25

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FIELDIANA: ZOOLOGY

greatest length
condylobasal

palatal

bulla r
length — '
less tube

Fig. 15. Skull, dorsal and palatal aspects showing cranial measurements used in text: a, rostrum width; b, least
interorbital breadth; c, zygomatic breadth; d, mid-frontal expansion; e, braincase, greatest width.

HERSHKOVITZ: NEW SPECIES OF AKODON

27

Fig. 16. Akodont type skull, dorsal aspect.

Explanation of Figures 16-18. Practically all topographic features of the sigmodontine skull are shown except cranial
crests and ridges absent in Akodon.

Bones

1 nasal

2 frontal

3 parietal

4 interparietal

5 occipital

6 premaxillary

7 maxillary

8 jugal; zygomatic

9 squamosal; temporal

10 lacrymal

1 1 auditory or tympanic bulla

1 2 mastoid, periotic capsule

1 3 infraorbital foramen or fissure

14 alisphenoid

15 orbitosphenoid

16 basisphenoid

17 presphenoid

18 palatine

(Continued on opposite page)

28

FIELDIANA: ZOOLOGY

Akodon. The A. cursor series includes 1 1 juvenals
and young comparable in age to those of the sanc-
tipaulensis series. The latter species differs in the
same respects from young A. cursor as it docs from
the adults. It is apparent that in Akodon, cranial
growth pattern from juvenal to adult is one of
increase in si/e with little change in proportions
and overall shape. The same likely holds for Ako-
don sanctipaulensis.

Specimens Examined— Total 10 (table 3). all fmnh.
Primeiro Morro 6 (holotype and 5 paratypes); Quadro
Ponteado. 2; Morrctinho. 1; Iporanga. 1.

Acknowledgments

Fieldwork in Brazil during 1986 was made pos-
sible through the sponsorship of the Museu Na-
tional. Rio dc Janeiro, with permission for faunal
investigations in the National Parks and Reserves
granted by the Instituto Brasileira de Desenvol-
vimento Florestal (ibdf) of the Ministerio dc Agri-
cultura; hospitality and logistical help was provid-
ed by Giraldo Israel Rocha. Chief, and Braulio F.
dc Sou/a Dias of the Reserva Ecologica of the
Instituto de Geografia c Estadistica (ibge). The

institutions and their representatives are heartily
thanked. My gratitude is expressed to Professors
Cleber J. R. Alho and Jader Soares Marinho Filho
of the Universidade de Brasilia for loan of traps
and use of university facilities, and to the latter
for assistance in the field as well. My thanks extend
to Professor Helena Luna Ferrcira for use of the
University's genetic laboratory in her charge, to
Professor Eunice Judith Cardoso de Almeida and
graduate student Marta Svartman of the Univer-
sidade de Sao Paulo for the preparation of karyo-
types, to Professor Milton Thiago de Mello for
orientations and hospitality in Brasilia, and to
Universidade dc Brasilia graduate student Miguel
Marini for hospitality and volunteer field assis-
tance.

Permission by Professor Ulises Caramaschi, of
the Museu Nacional. Rio de Janeiro, and by au-
thorities of the British Museum of Natural His-
tory, London, for study of the specimens of sig-
modontines in their respective charges, is gratefully
acknowledged.

Fieldwork during July 1986 was assisted by
Christopher Tribe, graduate assistant of the Museu
Nacional. and during August of the same year by
good friend and volunteer. Scott Lindbergh of
Brasilia. Notes by the late A. M. Olalla on the Sao

(Fig. 16. continued from previous page)

Foramina, Fissures, Sutures, Processes, Fossae, Others

a coronal suture

b sagittal suture

c suprafrontal foramen

d paraptcrygoid fossa of pterygoid; external pterygoid
process (of alisphenoid. 14)

hamular process of pterygoid (internal pterygoid
process of alisphenoid, 14)

squamosal or temporal process of zygomatic arch
(9)

petrotympanic fissure (middle lacerated foramen.
Glasserian fissure)

h foramen ovale and foramen spinosum

i auditory meatus

j temporal vacuity (postglenoid foramen, subsqua-
mosal foramen)

k hamular process of squamosal (9)

I condyle of occipital or occipital condyle (5)

m paraoccipital process

n capsular projection for upper incisor, and naso-
pharyngeal foramen of maxillary (7)

o prcorbital foramen

p zygomatic plate of maxillary (7)

q anteorbital bridge of maxillary (7)

r anterior palatine foramen

s optic foramen

sphenopalatine vacuity (anterior alar fissure, an-
terior lacerated foramen)
malar process of maxillary (7)

v anterior and posterior ethmoidal foramina

w alisphenoid foramen or canal

x basioccipital of occipital (5)

y palatal process of premaxillary (6)

z palatal process of maxillary (7)

aa mesopterygoid fossa (craniopharyngeal canal: pos-
terior nares) between internal pterygoid processes
(see fig. 1 5 for points of measurement)

bb postincisor foramen

cc posterior palatine foramen (foramina) of maxillo-
palatine (7. 8) and/or palatine (18)

dd palatine process of premaxillary (6)

ee posterior palatine foramina or pits

fT alveolar process of maxillary (7)

gg sphenoidal fissure

hh sphenofrontal foramen

ii glenoid fossa of squamosal (9)

jj stapedial foramen

kk interptcrygoid foramen (foramen Civinini)

11 Eustachian canal

mm carotid canal (posterior lacerated foramen)

nn jugular foramen

oo mastoid process of mastoid ( 1 2)

pp stylomastoid foramen

qq hypoglossal foramen or canal

rr buccinator-masticatory foramen (partially con-
cealed by alisphenoid. 15)

ss foramen magnum of occipital (5)

HERSHKOVITZ: NEW SPECIES OF AKODON

29

Paulo collecting localities were kindly supplied by
Paulo P. Vanzolini through Melvin Traylor.

The manuscript benefitted from critical review
by colleague Bruce Patterson. Assistance in data
recording, manuscript typing, and editing was pro-
vided by Associate Barbara Brown and Technical
Assistant Ronald Edwards. Figure 1 is the work

of Staff Artist Clara Simpson, Figures 10-12, of
Elizabeth Liebman, Figures 6, 13-22, of Staff Art-
ist Zorica Dabich. Most of the photographs were
produced, and all were printed, by Staff Photog-
raphers Ron Testa and Diane White. My thanks
to all.

Fieldwork in Brazil was supported by the Bar-
bara E. Brown Fund for Mammal Research.

Fig. 17. Akodont type skull, palatal aspect. For names of parts and foramina see Figure 16 caption.

30

FIELDIANA: ZOOLOGY

u.

HERSHKOVITZ: NEW SPECIES OF AKODON

31

RIGHT UPPER

LEFT LOWER

Fig. 1 9. Akodont type left mandible: A, lateral sur-
face; B, medial surface; a, ramus; b, ascending ramus; c,
symphysis; d, angular process; e, condyloid process; f,
coronoid process; g, alveolar process; h, capsular pro-
jection of incisor root; i, sigmoid or superior notch; j,
inferior or lunate notch; k, superior masseteric ridge; 1,
inferior masseteric ridge; m, mylohyoid line; n, mental
foramen; o, mandibular or dental foramen; p, alveolar
foramen.

Explanation of symbols used for molar crown elements of akodont rodents (fig. 20):

Fig. 20. Upper and lower molar crown pattern of
akodont type rodents.

Upper Right Molars

Main Cusps (large numbers)

1. paracone

2. metacone

3. protocone

4. hypocone

Lophs, Conules, Conulids, Styles1

(medium-sized numbers)

5. anterolabial conule

6. anterolingual conule

7. oarastyle

8. anteroloph

9. anteroconule

10. mesostyle

1 1 . paralophule

12. mesoloph

13. metalophule

14. posteroloph

15. mure

16. enterostyle

Flexi or Enamel Folds'

(small numbers)

17. anteromedianflexus

18. anteroflexus

19. paraflexus

20. mesoflexus

21. metaflexus

22. posteroflexus

23. protoflexus

24. hypoflexus

Lower Left Molars

Main Cusps (large numbers)

1. metaconid

2. entoconid

3. protoconid

4. hypoconid

Lophs, Conules, Conulids, St \ lids
(medium-sized numbers)

5. anterolabial conulid

6. anterolingual conulid

7. protostylid

8. anterolophid2

9. anteroconulid3

10. metastylid

1 1 . metalophulid

12. mesolophid

13. entolophid

14. posterolophid

15. murid

16. mesostylid

(Continued on opposite page)

32

FIELDIANA: ZOOLOGY

crested

terraced

plane

Fig. 21. Molar crowns of sigmodontine rodents; evolutionary stages from primitive crested to derived plane in
side and crown views (from Hershkovitz, 1955).

(Fig. 20, continued from opposite page)

Flexids or Enamel Folds'

(small numbers)

17. anteromedianflexid

18. anteroflexid

19. metaflexid

20. mesoflexid

21. entoflexid

22. posteroflexid

23. protoflexid

24. hypoflexid

Addendum

25. ectostylid

26. anterolophulid4

1 Numbers 5, 6, 7, 8, 9, 17, 18 of upper and lower first molars and number 10 of first lower molar are elements
of the procingulum. Numbers 8, 9 may also be present in second and third upper and lower molars.
: Commonly coalesced with metaconid.
1 Commonly coalesced with anteroloph and metaconid.
4 Anterolabial cingulum of Reig (1987).

HERSHKOVITZ: NEW SPECIES OF AKODON

33

diversity on habitat complexity. Revista Brasileira de
Biologia, 41(1): 223-230.

1982. Quantitative components of three cer-

Fig. 22. Sigmodontine incisor curvature with refer-
ence to the basal-incisive plane (a-b) and vertical-inci-
sive plane (from Hershkovitz, 1962, p. 103).

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269-286.

HERSHKOVITZ: NEW SPECIES OF AKODON

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Field Museum of Natural History
Roosevelt Road at Lake Shore Drive
Chicago, Illinois 60605-2496
Telephone: (312) 922-9410