GE FO] National Museums National Museum

k PA of Canada of Natural Sciences
ACTE
Ottawa 1970
Publications

in Palaeontology, No. 6

A Fossil Ray,

Possibly Myledaphus
(Elasmobranchii: Batoidea)
from the Late Cretaceous
Oldman Formation

of Western Canada

by Wann Langston, jr.

Publications
de paléontologie, n° 6

Musées nationaux Musée national
du Canada des sciences naturelles

Digitized by the Internet Archive
in 2011 with funding from
California Academy of Sciences Library

http://www.archive.org/details/publicationsinpaé1 nati

A Fossil Ray,

Possibly My/edaphus
(Elasmobranchii: Batoidea)
from the Late Cretaceous
Oldman Formation

of Western Canada

National Museum of Natural Sciences
Publications in Palaeontology, No. 6

Published by the
National Museums of Canada

Staff editor
Jean Sattar

Musée national des sciences naturelles
Publications de paléontologie, n°6

Publié par les
Musées nationaux du Canada

Graphiste
Georges Beaupré

A Fossil Ray,

Possibly My/edaphus
(Elasmobranchii: Batoidea)
from the Late Cretaceous
Oldman Formation

of Western Canada

Wann Langston, Jr.

© Crown Copyrights reserved

Available by mail

from the

National Museums of Canada
Publications Division

Ottawa 4

Price: $0.50
Catalogue No. NM95-8/6
Price subject to change without notice

The National Museums of Canada
Ottawa, Canada
1970

P0987654321
Y79876543210

Litho in Canada

Résumé

Cette étude décrit le squelette partiel d'un poisson batoide des dépôts
d'eau douce de la formation Oldman. Les lacunes du squelette reliées a
sa ressemblance apparente à celui des guitares et des raies compliquent
sa classification. Même la dimension et la forme originales de l'animal
demeurent très imprécises. Toutefois, à la lumière d'indices accidentels,
plutôt négatifs, on est porté à croire que le spécimen serait un
Myledaphus.

Summary

A partial skeleton of a batoid fish obtained from freshwater deposits of
the Oldman Formation is described in this paper. The incompleteness
of the skeleton, combined with its superficial resemblances to banjo
fish, skates, and rays, hampers attempts to define its generic affinities.
Even the original size and shape of the fish cannot be precisely
determined. It appears, however, from a combination of circumstantial
and ‘‘negative’’ evidence, that the specimen may belong to My/edaphus.

Vi

Biographical Note

Dr. Wann Langston, a leading researcher into the evolution of fossil
reptiles, is particularly known for his work on dinosaurs. While he was
Curator of Fossil Vertebrates with the National Museums of Canada
from 1955 to 1962, Dr. Langston collected dinosaur remains from
southern Alberta and Saskatchewan, and he has worked under contract
for the Museums studying horned dinosaurs. He has published major
works on crocodile evolution and primitive reptiles and has contributed
numerous articles to scientific journals. Now Vertebrate Paleontologist
with the Texas Memorial Museum and Director of the Vertebrate
Paleontology Laboratory, the University of Texas, Austin, Dr. Langston
is collecting in Big Bend National Park near the Mexican border.

vil

à
EE hn.

Se d

Introduction

It is well known that owing to their lack of a bony skeleton,
elasmobranch fishes are represented in the fossil state mainly by teeth,
denticles, and various dermal spines. Only occasionally and under
exceptional circumstances are the primarily cartilaginous portions of
the skeleton preserved as, for example, at Mt. Lebanon, in the
lithographic stone of Bavaria and at Cérin, Monte Bolca. With the
notable exception of the pleuracanths such occurrences are practically
unknown in freshwater deposits. The only non-dental elasmobranch
skeletal material hitherto reported from such deposits in western
Canada is the posterior part of a vertebral column from the late
Cretaceous Edmonton Formation, called Pa/aeospinax ejuncidus by
Lambe (1918). The discovery of a partial skeleton of a batoid fish in
the Oldman Formation of southeastern Alberta is therefore not without
interest.

The specimen was found by Charles M. Sternberg in 1937, 6:
miles southeast of the town of Manyberries. The locality is about 11
miles northwest of the site where in the same year Dr. Sternberg
obtained the exceptional skeleton of Paratarpon apogerontus recently
described by Bardack (1970). Interestingly, these are the only fish
skeletons of any degree of completeness ever reported from the Oldman
beds. Although at first glance the present specimen appears unusually
well-preserved, detailed examination and comparison leave so much
uncertainty about the affinities of the fish that one can only speculate
about its probable generic assignment.

Acknowledgments

| am indebted to Dr. Dale Russell of the National Museums of Canada
for permission to complete this study, commenced over a decade ago
when | was associated with the Museum of Natural Sciences. Dr. C.M.
Sternberg has been most helpful with comments about the occurrence
of the fossil. Dr. Rainer Zangerl of the Field Museum kindly provided
the radiographs of the specimen, reproduced here as positive prints.
Drawings are by Mrs. Doris Tischler.

A Fossil Ray

Plate 1
Photograph of incomplete batoid skeleton
NMC 12443 partly excavated in the field.
Dark spots adjacent to specimen, first

believed to be remains of the skin, do not

contain any x-ray opaque materials, and are
probably of carbonaceous origin. Scale is in
inches. Photograph by C.M. Sternberg,
NMC negative 83383.

Occurrence and Condition

According to the field records, the
specimen (NMC 12443) was found
about 30 ft below the top of the Pale
Beds [i.e., Oldman Formation], in a
sandstone with clay and lignitic bands
near the base of a sandstone butte, on
the west side of a coulee tributary to
South Manyberries Creek, in SW%, sec.
35, tp. 4, rge. 5 west of the 4th
meridian (see Canada Dep. Mines and
Res. Geol. Map 567A—Dunmore,
Alberta).

The specimen comprises the anterior
part of the axial skeleton including
chondrocranium, the ankylosed synarc-
ual plate, and an articulated series of 28
definable ‘free’ vertebrae. The animal
lay on its vertral surface with the
vertebral column curved distally to the
left (Plate 1). The head is distorted, but
some vertebral centra are uncrushed.
Preservation was such that preparation
in a conventional manner was imposs-
ible, and most of the study had to be
carried out with the aid of radiography.
After removal of the field jacket and
some matrix the upper side of the block
containing the specimen was imbedded
in bee’s wax reinforced with gauze and
then x-rayed (Plate 2). This procedure
revealed that the visceral and appen-
dicular skeletons are missing. No teeth
or dermal denticles are preserved.
Weathering evidently destroyed the pos-
terior part of the skeleton before its
discovery.

A Fossil Ray

Plate 2

Radiograph positive of NMC 12443: left-hand
page, anterior part of skeleton; right-hand
page, posterior part. Scale: length of bar=5cm.

Occurrence and Condition

Plate 2 (cont'd.)

A Fossil Ray

Plate 3

Detail of radiograph positive print of NMC
12443 showing tesserae investing part of the
calcified cartilage in the area of the
vertebral ankylosis. Scale: 1.6 actual size.

Morphology

All preserved parts of the skeleton are
composed of calcified cartilage. The
anterior parts are largely invested by
isometric tesserae’ of up to 2 mm in
diameter, and are clearly seen in the
radiographs. Tesserae in the head region
do not appear to be arranged in any
particular pattern, but those in the
pectoral area show a distinct longitudinal
orientation (Plate 3).

The general outline of the
chondrocranium is interpretable from
the radiograph. Its length of 21 cm is
about 1.6 times its width. A large
orbital vacuity can be seen to occupy
the middle part of the right side of the
specimen. Pre- and post-orbital areas of
the skull appear to have been about
equal in size, the width posteriorly
being only a little more than that in
front. As preserved, the cranium is
truncated anteriorly; there is no evi-
dence that a rostrum was present, but
the possibility cannot be completely
ruled out. Wide olfactory capsules, evi-
dently deflected downward in batoid
fashion, are clearly seen (Figure 1, n).
These are separated medially by a gap of
about 10 mm. Outlines of the antorbital
(dorsal) fontanelle are indistinct, al-
though a certain ‘‘thinness” in the radio-
graph indicates its general position. The
opening was evidently about half as long
as the cranium and more oval than
triangular in outline. A light area postero-
medial to the right orbit occupies the
position of the otic capsule on that side.
A distinct process projecting antero-
laterally from behind each olfactory
capsule (Figure 1, a) was probably for
attachment of the antorbital cartilage,
of which no trace is preserved. A trian-
gular process projecting posterolaterally
from either side of the otic region

'The word used here in the sense of Wood-
ward (1889) should not be confused with the
same term sometimes applied to the tesselated
pattern of dermal bones in ostracoderms.

Fig. 1. Diagrammatic representation of an-
terior part of the skeleton. a, process for
attachment of antorbital cartilage; c, primary
double cone; f, area of anterior fontanelle
(distorted); h, hyomandibular process; Is, ?
lateral stay; n, olfactory capsule; o, orbit; p,
“odontoid’’ process of ankylosis; s, ? syn-
arcual spine (displaced).

(Figure 1, h) no doubt gave attachment
to the hyomandibular cartilage. There is
no evidence of a postorbital process. The
cranio-cervical joint is more than half as
wide as the chondrocranium. It com-
prises two thick articular facets separ-
ated by a deep U-shaped notch, which
receives a corresponding tongue-like
process of the ankylosis.

The vertebral column consists an-
teriorly of a massive synarcual anky-
losis, a series of fused vertebrae, which
characteristically supports the pharyn-
gobranchial cartilages and some pectoral

A Fossil Ray

structures in skates and rays. This is
followed by 28 movable postankylosis
vertebrae. The part of the column pre-
served may therefore represent no more
than half the body length.

The ankylosis, clearly defined in the
radiograph (Plate 2), is a little longer
than the skull. It broadens anteriorly at
its articulation with the braincase,
where it attains a maximum width of 74
mm. The massive cranial condyle bears a
strong median ‘‘odontoid’”’ process (Fig-
ure 1, p). Seven vertebral centra, the
first represented by only the posterior
half of the double cone, appear at the
posterior end of the ankylosis. Although
these centra do not differ greatly in
length from those in the free column
their diameters decrease rapidly craniad,
so that the width of the first centrum is
only about one-quarter that of the
eighth, or first postankylosis, vertebra.
There is no indication of laterally ex-
panded vertebral arcualia behind the
main area of consolidation. Lateral pro-
cesses of any kind are ill-defined, and |
am unable to distinguish any areas of
attachment for the branchial cartilages.
A narrowly triangular, longitudinal ridge
seen a little to the right of the midline
in the radiograph (Figure 1, s) is perhaps
the displaced synarcual spine (see
Garman 1913, pl. 55). No sign of an
articulation for the scapular arch can be
seen. What may be remains of a “‘lateral
stay’ appears as a wide triangular area on
the right side of the ankylosis.

All post-ankylosis vertebrae have sim-
ple spool-shaped centra with thickened
articular edges (Plate 2). Double cones
are not discernible in the radiographs of
this series. Viewed in the horizontal
plane, the centra appear fairly uniform
in shape and dimensions: those just
behind the ankylosis have a maximum
transverse diameter of about 16 mm, a
least diameter of 15 mm, and a length
of about 12 mm, whereas at the end of

the preserved column, these measure-
ments are 17.5, approx. 14, and 11 mm
respectively. Irregular shadows along the
sides of the centra represent the dis-
torted and fragmentary remnants of the
tesserate covering of the arcualia.

A systematic tool used by some in
elasmobranch studies is the pattern of
calcification in the vertebral centra (for
a recent review of the limitations of this
“system,” see Applegate 1967). To ex-
pose this pattern a centrum is sectioned
transversely at its narrowest diameter;
according to Ridewood (1921) such
sections are most reliable in closely
related taxa if they are obtained from
caudal vertebrae. However, no caudal
elements being available in the present
specimen, a well-preserved and easily
removed mid-trunk vertebra (the second
behind the ankylosis) was selected for
sectioning.

This vertebra has a tiny (diameter:
0.9 mm) chordal canal. The subcircular
centrum is of relatively massive and
uncomplicated form (Figure 2). It is
constructed of tightly appressed, con-
centric lamellae (= lines or zones of
growth (Ridewood 1921)). Regularly
alternating hard and soft calcified zones
are of fairly regular thickness (approx.
0.28 mm). Some 24 of them occur
along the transverse radius of the cen-
trum. Although they parallel the irregu-
lar outlines of the centrum peripherally,
these annulae become more regularly
circular toward the chordal canal. The
cellular composition characteristic of
the outer zone of the chordal sheath
(see Applegate 1967) is clearly discern-
ible in the annulae at a magnification of
X10. A dark band about 0.3 mm wide
occurs a short distance from the chordal
canal. This is composed of denser ma-
terial than the ‘‘zones of growth’’ and
evidently represents the middle zone of
the sheath cartilage, that is, the ‘‘double
cone” of authors. Within this, and sur-

Fig. 2. Diagrammatic cross-section of the
second post-ankylosis vertebra, at midlength.
Actual size. Small irregularly disposed objects
are calcified tesserae.

rounding the chordal canal, is a lighter
and less compact inner zone represen-
ting the calcified elastica interna.

The broad lateral, and relatively nar-
rower dorsal and ventral lobes of the
cross-section are presumably formed by
the coalescence of expanded horizontal
and vertical calcified rays (toward the
distal end of the preserved column
longitudinal shadows on the radiograph
suggest the presence of better-defined
calcified septa). The only evidence of
uncalcified intermedialia (sensu
Ridewood) are the notches in the sides
of the centrum. Calcified tesserae oc-
cupy these notches, which were sites of
persistently cartilaginous arch com-
ponents.

The fish described above was a large
one, but in the absence of fins and the
tail, conclusions about its proportions
are only speculative. Living stingrays,
for example, vary from fishes with
relatively wide disks and short tails
(butterfly rays) to species with whiplash
tails three times the length of the body.
If this fish was similar to the moderately
long-tailed Dasyatis hastatus, the animal
may have been about 3 metres long. It
was, however, smaller than individuals
of several existing dasyatid species.

Systematics

The thoroughly calcified vertebral cen-
tra and the absence of a postorbital
process are clear evidence that the
Alberta fish belongs to the modern level
of elasmobranch organization (Schaef-
fer 1967). The laterally expanded and
downwardly deflected nasal capsules,
the strong condyloid occipital articu-
lation, and the massive ankylosis are
exclusive batoid qualities. In most other
respects the specimen offers a puzzling
array of features commonly found
among banjo fish (Rhinobatoidea),
skates (Rajoidea), and rays
(Myliobatoidea).

Absence of a rostrum would favour
assignment to the rays, but it would not
rule out inclusion with the skates—the
existing Malacorhina lacks a rostral car-
tilage. The orientation of the nasal
capsules seems more ray-like than
skate-like, but the general shape and
proportions of the rather narrow skull
are reminiscent of some skates (especial-
ly Malacorhina) and guitar fish, minus
the rostrum. The resemblance to rhino-
batoids is accentuated by the absence of
a postorbital process. This process,
either relict or secondarily developed, is
generally present in existing rays al-
though it has no jaw-supporting func-
tion. It is usually fragile and often only
narrowly attached, so it is possible that
the process may have been destroyed in
the fossil.

In so far as it is interpretable the
ankylosis, with what is believed to be
a wide lateral stay, resembles that of
Rhinobatus percellens (Garman PI. 55,
fig. 4). Neither is it so long and slender
as in the rays Aetobatus and Rhino-
ptera, nor does it widen anteriorly as in
Potamotryoon, or Dasyatus. \t is, how-
ever, longer and narrower than in Raja.
Absence of an obvious scapular articu-
lation at the side of the ankylosis
suggests that the scapulae were joined to
its upper spine in simple skate fashion

A Fossil Ray

rather than by the complicated lateral
articulation found in rays. But if this
was the natural state of affairs, it may
represent a primitive condition.

Hasse (1879-1885) based a compre-
hensive system of elasmobranch classifi-
cation upon the arrangement of second-
ary calcification seen in the longitudinal
septa of the vertebral centra. Opinion
differs with respect to the usefulness of
this feature. Regan (1906) and
Ridewood (1921), for example, have
attacked the “system” as being inapplic-
able at higher taxonomic levels, but
Applegate (1967) finds it valid within

certain limitations. The patterns of
secondary calcification (‘‘stars’’) re-
vealed in transverse sections of the

centra may not be reliable keys to
phylogenetic inferences, and according
to Ridewood (p. 396) they ‘‘do not
appear to have any direct bearing on the
classification of the families” within the
Batoidea. Nevertheless, lacking more
definitive criteria, | shall note some
aspects of vertebral structure that may
be helpful in analyzing the systematic
position of the Oldman fish.

The outstanding feature of the cen-
trum described above is its compactness
as compared with most elasmobranch
vertebrae. Although a basic rayed pat-
tern can be detected, the appearance is
completely different from the many-
branched ‘‘star’’ found in Raja. Rhino-
batus, believed to have the most general-
ized caudal vertebrae among batoids
(sensu Romer 1966, less torpedinoids),
is considered in some detail by
Ridewood. The calcification pattern is
said to vary among certain species from
a distinct eight-rayed star to a compact
pristid-like structure, and some variation
also occurs ontogenetically. The eight-
rayed star in caudal vertebrae of A.
granulatus gives way anteriorly to more
simplified patterns as a result of enlarge-
ment and coalescence of the calcified

10

septa. It is easy to imagine the fossil
fitting into interspecific, ontogenetic or
metameric series such as these, and its
high degree of calcification is no doubt
partly a reflection of its anterior posi-
tion in the column.

Similar variations occur also among
the dasyatid stingrays where instances
of excessive calcification are reported
(Ridewood 1921; Hasse 1885). The
fossil vertebra could theoretically be
derived from the patterns illustrated for
the rays Rhinoptera javanica and even
Urogymnus ( = Rhachinotus) asper-
rimus or Myliobatis neuhofi (see
Ridewood 1921, figs. 36, 37). Indeed
the sectioned centrum appears fairly
similar to a caudal vertebra of “7rygon”’
figured by Hasse (1882, Pl. 19, fig. 3),
and is even more like one ascribed to a
Cretaceous Rhinoptera (Hasse, PI. 21,
fig. 29).

The foregoing analysis reveals such
basic uncertainties and ambiguities that
systematic determination below the or-
dinal level is very uncertain. Though
clearly a batoid, the fish was certainly
not a pristid or a torpedo. The vertebral
structure apparently argues against
assignment to the Rajidae, and the
absence of a rostral cartilage (if natural)
against the Rhinobatoidea, as under-
stood from most of the existing repre-
sentatives.

Collectors have long been aware that
scattered teeth of a ray, Myledaphus
bipartatus Cope, are ubiquitous in the
predominately freshwater Oldman and
Edmonton Formations in western
Canada. Indeed so abundant are they
that virtually every fossiliferous concen-
tration of any variety will be found to
contain these double-rooted, polygonal
crushing teeth. The genus is usually
placed among the Dasyatidae. No other
kinds of ray teeth have ever been
reported from the same deposits. There
is thus some circumstantial support for

supposing that the skeleton just
described belongs to My/edaphus, and it
is disappointing that the lack of teeth in
the specimen precludes a positive state-
ment. In sum, what evidence there is
favours a reference to either the guitar-
fishes or to the ray families Rhino-
pteridae or Dasyatidae. | have opted for
the latter, because of the possibility that
the skeleton may belong to My/edaphus.

Comparisons

Most extinct batoid taxa are based on
teeth and denticles, and the present
specimen cannot, of course, be com-
pared with these. Some, mostly older
taxa, whose skeletons are known, are so
primitive as to show stronger resem-
blances to selachians than to the Alberta
ray. The batoid affinities of the Jurassic
Asterodermus, Belemnobatis, and
Spathobatis are still disputed (see Saint-
Seine 1949; Schaeffer 1967). More ad-
vanced types, mostly representing living
genera, are among the magnificent
assemblage of Eocene elasmobranchs
from Monte Bolca. Unfortunately,
despite their generally impressive state
of preservation, the skulls and vertebrae
are not adequately revealed in the ma-
terial described by Jaekel (1894). Useful
comparisons with the Alberta specimen
are therefore impossible. Similar dif-
ficulties arise in attempting to compare
the Cretaceous material from Mt.
Lebanon, in which batoids are richly
represented (Hay 1903; Woodward
1942).

Among Canadian elasmobranchs, the
poorly preserved caudal skeleton pro-
visionally assigned to Palaeospinax by
Lambe apparently represents a selachian
having ‘‘cyclospondylic’’ vertebrae and
densely clothed by a shagreen of tiny
granular tubercules. The fish was prob-
ably considerably smaller than the
Oldman ray.

As noted, there is no basis for com-
parisons with Myledaphus, to which
genus the specimen may well belong.

Although it may be of no signifi-
cance in relation to present questions,
the following note is of some interest in
connection with My/edaphus. |n spite of
the great abundance of this presumed
dasyatid ray’s teeth in the Oldman,
Edmonton, and other late
Cretaceous and early Tertiary deposits, |
am unaware of the discovery anywhere
in these beds of a _ characteristic

similar

11

myliobatoid tail spine (‘‘stinger’’), so
demanding of respect in living stingrays.
Admitting the hazards of negative “‘evi-
dence,’ it nevertheless seems reason-
able, in view of the incredible numbers
of their teeth, to suppose that the
extinct rays were devoid of such spines.
Some living myliobatids and the
dasyatid Urogymnus lack stingers.

12

Taphonomy

The sedimentary character of the rocks
surrounding the specimen suggests an
area of swash, and the first idea that
came to mind regarding the mode of
burial was that the fish had been. stran-
ded on a tidal flat. But such sedi-
mentary structures can also result from
seasonal flooding in rivers and lakes;
nearby exposures at the same horizon
contained the fragmentary plant and
vertebrate (mostly hadrosaurian) re-
mains that are most often associated
with fresh and brackish water de-
positional environments.

It is assumed that as in most rays the
individual possessed dermal denticles;
the absence of these in the fossil,
together with loss of jaws and fins,
indicates that maceration was far ad-
vanced at the time of burial. Shadows
seen on the radiographs of the chondro-
cranium suggest wrinkles, which may
have existed before burial and which
could have been caused by desiccation.
These conditions recall a singular
characteristic of the decomposition of
rays sometimes observed on modern
beaches. Such fish when stranded may
come to rest with their broad ventral
surfaces flat against the substrate. The
mouth and pharyngeal cavity soon fill
with sediment which has the effect of
anchoring the carcass while the fins
disintegrate. The skin on the superior
surface is soon reduced by scavengers
and maceration (under salt water condi-
tions a combination of pickling and
desiccation usually delays complete de-
gradation of the skin and total loss of its
denticles). Currents and animal activities
may then separate the axial skeleton
from the jaws and gill arches, which are
held fast in the sediment occupying the
branchial chamber. By this time very
little connective tissue remains and the
cartilaginous skeleton is largely exposed
to drying and consequent shrinking and
warping, particularly of the chondro-

cranium. Hence, isolated jaws with teeth
and axial skeletons comprising crania
and parts of spinal columns may be
buried separately. This course of events
seems adequate to explain the occur-
rence of the Oldman ray.

Environmental Interpretation

Discovery of a representative of a large-
ly marine group of fishes in sediments
that may be of non-marine origin calls
for some comment. À general des-
cription of the geological conditions in
the Manyberries district of Alberta is
given by Russell and Landes (1940:
62-72). As elsewhere the Oldman de-
posits in this area are presumed to be
mainly of freshwater origin. They con-
tain freshwater invertebrates, dinosaurs,
other reptiles, and mammals. However,
the marine Bearpaw beds occur stra-
tigraphically only a short distance above
the fossil horizon, and proximity to
marine waters at the time of the ray’s
burial is implicit in the inferred late
Cretaceous history of the region (see
Williams and Burk 1964).

The appearance of a fossil elasmo-
branch under such conditions should
occasion no surprise and should not be
taken as a contraindication of a fresh-
water origin for the deposits adduced
from other evidence. Smith (1936) of-
fers a list of 52 Recent species of
elasmobranchs that have been reported
from fresh water. Although later work
(Bigelow and Schroeder 1953) suggests
that some of these records are er-
roneous, there is still ample justification
for Smith’s statements (p. 65) that ‘‘we
are not entitled to exclude the elasmo-
branchs from fresh water on physio-
logical grounds. Given the proper eco-
logical conditions, there is little doubt
that most of the smaller forms, at least,
could survive as well in fresh water as in
the ocean.”

There can be no question about the
occurrence of Myledaphus in
marine sediments in western Canada and
elsewhere. Restriction of this genus to
North America supports the notion that
it was confined in fresh to brackish

non-

13

A Fossil Ray

water.* Interestingly among existing
elasmobranchs the rays seem to have the
widest tolerance for non-saline environ-
ments, and one family, Potamo-
trygonidae, is restricted to fresh water.
Other rays are said to occur commonly
in shoal channels and lagoons along
tropical coasts, in waters of variable
salinity. Similar conditions may be
reasonably inferred from the thinly lam-
inated siltstones and interbedded car-
bonaceous shales that surrounded the
present specimen.

Rays at the present time have a
mostly tropical to subtropical distri-
bution; only a few species range regular-
ly into temperate latitudes. Occurrence
of the ray skeleton in rocks that also
contain crocodilian remains indicates a
climatic range consistent with that of
existing species.

2 The striking external resemblance between
the teeth of My/edaphus and the mainly Old
World Cretaceous- Recent Hypolophus has
been noted by several authors. However,
McNulty (1964) reports significant histolo-
gical differences in the structure of the
crowns by which these fishes can be distin-
guished.

14

References

Applegate, S.P.

(1967). A survey of shark hard parts. In
Sharks, Skates and Rays, ed. by Perry W.
Gilbert and others. Baltimore, Johns Hopkins
Press. 37-67, 7 figs., 4 pls.

Bardack, D.

(1970). A new Teleost from the Oldman
Formation (Cretaceous) of Alberta. Watt.
Mus. Canada Publ. in Palaeontol. No. 3.
Ottawa.

Bigalow, H.B. and W.C. Schroeder.
(1953). Fishes of the western North Atlantic,
Part 2—Sawfishes, Guitarfishes, Skates and
Rays. Mem. Sears Found. 1: 588pp.

Garman, S.

(1913). The Plagiostomia (sharks, skates, and
rays). Mem. Mus. Comp. Zool. Harvard, 36:
528pp.

Hasse, C.

(1879-1885). Das nattirliche System der
Elasmobranchier auf Grundlage des Baues und
der Entwicklung ihrer Wirbelsaule. Jena. 3
vols. 1879: 6 + 76; 1882: 6 + 284; Suppl.
1885: 27p.

Hay, O.P.
(1903). On a collection of Upper Cretaceous
fishes from Mount Lebanon, Syria, with
descriptions of four new genera and nineteen
new species. Bull. Amer. Mus. Nat. Hist. 19:
395-452.

Jaekel, O.

(1894). Die eocänen Selachier vom Monte
Bolca. Ein Beitrag zur Morphoganie der
Wirbelthiere. Berlin, Kgl. Akad. der
Wissenschaft. 176pp.

Lambe, L.M.

(1918). On remains of a selachian from the
Edmonton Cretaceous of Alberta. Ottawa
Nat. 32 (2): 27-28.

McNulty, C.L.

(1964). Hypolophid teeth from the Woodbine
Formation, Tarrant County, Texas. Ec/. Geol.
Helvetiae 57, (2): 537-539.

Regan, C. Tate.

(1906). A classification of the selachian
fishes. Proc. Zool. Soc.—1906, (48): 722-758.

Ridewood, W.G.

(1921). On the calcification of the vertebral
centra in sharks and rays. Phil. Trans. Roy.
Soc. London (B), 210: 311 -407.

Russell, L.S. and R.W. Landes.

(1940). Geology of the southern Alberta
Plains. Geo/. Surv. Canada Mem. 221: 223pp.

Saint-Seine, P.
(1949). Les poissons de calcaires litho-

graphiques de Cérin. Nouv. Arch. Mus. Hist.
Nat. Lyon 2: 357pp.

Schaeffer, Bobb.

(1967). Comments on elasmobranch evolu-
tion. In Sharks, Skates and Rays, ed. by Perry
W. Gilbert and others. Baltimore, Johns
Hopkins Press. 3-35.

Smith, H.W.

(1936). The retention and physiological role
of urea in the Elasmobranchii. Biol. Rev. 11
(1): 49-82.

Williams, G.D. and C.F. Burk.

(1964). Upper Cretaceous. In Geological
History of Western Canada, ed. by R.G.
McCroosan and R.P. Glaister, Alberta Soc.
Petrol. Geol.: 169-189.

Woodward, A.S.

(1942). Some new and little known Upper
Cretaceous fishes from Mount Lebanon. Ann.
Mag. Nat. Hist. 9 (11): 537-568.

15

—

| : A4 i.
SUR VAT Bie Sr rer ere)
| nr? D

“ ov oa
SS ae > D wai ~ " aie
P cadre) oumyis)

PEAT 1 SE A

‘1° {tease
LT eee ee
et. 1 less dus arias ar

yer Too on Ve ire

7 st ae

es gh) > nes. wm
aay ol er D =