Skull and atlas-axis complex of the Upper Jurassic sauropod Camarasaurus Cope (Reptilia: Saurischia)

120 Pages·1995·61 MB·English

by  James H Madsen

BULLETIN
1
OF CARNEGIE MUSEUM OF NATURAL HISTORY
SKULL AND ATLAS-AXIS COMPLEX OF THE
UPPER JURASSIC SAUROPOD
CAMARASAURUS COPE
(REPTILIA: SAURISCHIA)
JAMES H. MADSEN, JR., JOHN S. McINTOSH, AND DAVID S BERMAN
NUMBER
3 PITTSBURGH,
1995
BULLETIN
CARNEGIE MUSEUM OF NATURAL HISTORY
of
SKULL AND ATLAS-AXIS COMPLEX OF THE
UPPER JURASSIC SAUROPOD
CAMARASAURUS COPE (REPTILIA: SAURISCHIA)
JAMES MADSEN,
H. JR.
Dinolab, Inc., Salt Lake City, Utah 84109-0415
JOHN McIntosh
s.
Research Associate, Section of Vertebrate Paleontology;
Wesleyan University, Middletown, Connecticut 06457
DAVID BERMAN
S
Curator, Section of Vertebrate Paleontology
NUMBER
31 PITTSBURGH, 1995
BULLETIN OF CARNEGIE MUSEUM OF NATURAL HISTORY
Number 31, pages 1-115, 54 figures
Issued 10 October 1995
James E. King, Director
Editorial Staff: K. Christopher Beard, Editor,
Bradley C. Livezey, Editor, David R. Watters, Editor
Mary Ann Schmidt, ELS, Assistant Editor
CM
Cover illustration; Skull of Camarasaurus lentus 11338 with left mandibular ramus removed.
BULLETINS OF CARNEGIE MUSEUM OF NATURAL HISTORY
are published at irregular
intervals by Carnegie Museum of Natural History, 4400 Forbes Avenue, Pittsburgh, Pennsylvania
15213-4080, by the authority of the Board of Trustees of Carnegie Institute.
©
1995 by Carnegie Institute, all rights reserved.
ISSN 0145-9058
THE CARNEGIE
MUSEUM OF
NATURAL HISTORY
CONTENTS
Abstract
1
Introduction 2
Historical Review and Materials 2
Description 6
External Skull Fenestration 6
Skull Roof Bones 6
Premaxilla 6
Maxilla 8
Nasal 9
Prefrontal 10
Frontal 10
Parietal 11
Lacrimal 11
Jugal 12
Postorbital 13
Quadratojugal 13
Quadrate 14
Squamosal 15
Braincase 15
Supraoccipital 16
Exoccipital-opisthotic 16
Prootic 17
Laterosphenoid-orbitosphenoid 18
Basioccipital 19
Basisphenoid-parasphenoid 19
Scleral Ossicles 20
Stapes 20
^
Comparisons 21
Palate 21
Openings 22
Pterygoid 22
Ectopterygoid 23
Palatine 24
Vomer 24
Mandible 25
Dentary 26
Surangular 27
Angular 28
Prearticular 29
Articular 29
Splenial 30
Coronoid 31
Intercoronoid 31
Dentition 32
Hyoid 32
Atlas-axis Complex 32
Proatlas 32
iii
Atlas 32
Axis 33
Taxonomic History 33
Systematics 35
Acknowledgments 37
Literature Cited 37
Appendices 39
1. Reported Camarasaurus Skull Materials 39
2. Abbreviations for Figures 42
Figures and Captions 43
IV
ABSTRACT
The skull, lowerjaw, and atlas-axis complex ofthe Upper materials from the two principal quarries, all cranial materials
Jurassic sauropod Camarasaurus Cope are described in detail known to belong to Camarasaurus are listed, and the frag-
on the basis of articulated specimens and isolated elements mentary materials belonging to holotypic specimens are also
collected primarily from the Cleveland-Lloyd and Dinosaur figured. The skull and lower jaw of Camarasaurus are com-
National Monument quarries in Utah. Two elements hereto- pared with those of the prosauropod Plateosaurus and other
fore unreported in the sauropod skull and mandible, the stapes sauropods. Unlike many vertebrate groups the sauropods
and coronoid, are described. Each disarticulated element has exhibit greater morphological variation in the postcranial
been figured in multiple views, and in many instances the skeleton than in the skull, and therefore any attempt to revise
same element of several specimens is shown in order to the genus Camarasaurus must await the full study of
illustrate the range of individual variation. In addition to the articulated postcranial skeletorts.
1
2 BULLETIN CARNEGIE MUSEUM OF NATURAL HISTORY NO. 31
INTRODUCTION
Since the first discoveries of sauropod dinosaur great part on the descriptions of Antarctosaurus
skeletons in the 1870s, researchers have been (Huene, 1929), Apatosaurus (Berman and McIn-
frustrated by the almost total absence of skulls. tosh, 1978), Barosaurus (Janensch, 1935-1936,
This has been a factor hampering the systematic 1961), Brachiosaurus (Janensch, 1935-1936),
study of sauropod dinosaurs. With regard to Upper Dicraeosaurus (Janensch, 1936-1936), Diplodocus
Jurassic sauropods, this situation has been greatly (McIntosh and Berman, 1975; Berman and McIn-
reversed by discoveries at two famous Morrison tosh, 1978), Euhelopus (Wiman, 1929; Mateer and
Formation quarries in Utah, Cleveland-Lloyd and McIntosh, 1985), Nemegtosaurus (Nowinski,
Dinosaur National Monument (formerly the Carne- 1971), Plateosaurus (Huene, 1926, 1932; Galton,
gie quarry of Carnegie Museum of Natural His- 1984), Pleurocoelus (Lull, 1911; Kingham, 1962),
tory). Yet, to date, only four Upper Jurassic sauro- and Quaesitosaurus (Kurzanov and Bannikov,
pod genera are represented by complete skulls 1983). To avoid unnecessary repetition, these
found associated unquestionably with postcranial papers will not be continually referred to through-
skeletons: Apatosaurus, Brachiosaurus, Camara- out the text. The only cranial material referable to
saurus, and Diplodocus. Of these genera the Barosaurus belongs to specimens from the Ten-
greatest amount of cranial material known today is daguru beds of Tanzania and were originally
assignable to Camarasaurus, and, although several described as Gigantosaurus africanus Fraas, 1908.
excellent papers have been published dealing with Although the evidence for the subsequent referral
various aspects of the skull of this genus, no of the African species to the North American
comprehensive description is available. The genus Barosaurus by Janensch (1922) is not indis-
Cleveland-Lloyd and Dinosaur National Monument putable, its consideration as a diplodocid is un-
quarries have yielded sufficient materials for the doubted (McIntosh, \990b).
present detailed description of the skull of
Camarasaurus Cope, the first for any American The following abbreviations are used to identify
sauropod and the only example for a sauropod repositories of specimens: AMNH, American
other than that of the African Brachiosaurus Museum of Natural History; BYU, Brigham
(Janensch, 1935-1936) and the Chinese Young University; CM, Carnegie Museum of
Shunosaurus (Zhang, 1988). The Camarasaurus Natural History; DNM, Dinosaur National
skull materials from the two quarries complement Monument; USNM, National Museum of Natural
one another well. Those from Dinosaur National History; UUVP, Cleveland-Lloyd Dinosaur Quarry
Monument are articulated, complete, and well collections (housed in part at the Utah Museum of
preserved, whereas the Cleveland-Lloyd quarry has Natural History, Salt Lake City, Utah; Earth
yielded only disarticulated elements. This has Sciences Museum, Brigham Young University,
permitted the study of almost every skull element Provo, Utah; and College of Eastern Utah, Prehis-
in multiple views and the description of their toric Museum, Price, Utah); YPM, Yale Peabody
precise relationships with adjoining bones. Museum. The abbreviations r, 1, and p, enclosed in
Throughout the text comparisons are made be- parentheses and following a specimen catalogue
tween Camarasaurus and various sauropods and number, indicate right, left, and paired skeletal
the prosauropod Plateosaurus. These are based in -elements, respectively.
HISTORICAL REVIEW AND MATERIALS
The recorded discovery of sauropod skull of 1877-78 at Quarry 1, Como Bluff, Wyoming,
first
material, with the exception of isolated teeth, was collecting for O. C. Marsh (Ostrom and McIntosh,
YPM
made by William Harlow Reed, William Edward 1966). The specimen, 1905, consists of a
Carlin, and Samuel W. Williston during the winter well-preserved posterior half of skull, incomplete
1995 MADSEN ET K\..—CAMARASAURUS SKULL AND ATLAS-AXIS COMPLEX 3
YPM
maxillae, and dentary. It was designated the para- skull, 1911, found isolated and referred by
type ofMorosaurus (=Camarasaurus) grandis and Marsh (1883) to Brontosaurus. This specimen
was described briefly by Marsh (1879). The fol- closely resembles Camarasaurus and was believed
lowing year Marsh (1880) figured the cranium in at one time to belong to that genus, but subsequent
dorsal view, showing details of the endocranial investigation by one of us (JSM) has shown that it
cavity. Evidently the skull had been partially disar- may belong to Brachiosaurus.
ticulated, and in the illustrations (Fig. 2A, B, C) During approximately 1882-83 Cope’s collec-
the medial and lateral surfaces of the quadrate, tors at Garden Park north of Canon City, Colo-
pterygoid, and quadratojugal were reversed. A rado, recovered cranial and jaw materials of two
(AMNH
corrected version of the illustration (Fig. 2F) ap- large Camarasaurus specimens 5761 Fig.
;
pears in Marsh’s (1896) “Dinosaurs of North 2F, 4). This material was unpacked many years
America.” In the mid-1880s Marsh had his prepar- later, following Cope’s death and its transferral to
ators disarticulate all of the skull elements, a task the American Museum of Natural History, and
they performed with remarkable skill considering described and figured by Osborn and Mook (1921)
the infancy of preparation techniques at that time. as Camarasaurus supremus. Marsh also obtained
Each element was then illustrated in multiple material from a lower horizon at Garden Park
views for a planned, but never completed, mono- which included a cranium he described (1889Z?) as
graph on sauropod dinosaurs. Some of the figures “Morosaurus” agilis and which was later rede-
were published more than 80 years later by scribed in detail by Gilmore (1907). It is unlikely
Ostrom and McIntosh (1966), and the remainder that this specimen pertains to Camarasaurus and
are reproduced here for the first time. Eventually therefore will not be considered here. Marsh did
the skull was reassembled for exhibition, giving receive a partial skull of Camarasaurus from
the original drawings an even greater importance. Webster Park, Colorado, several years later, but
Marsh obtained more cranial material from incomplete preparation prevents from being
it
Como
several quarries at Bluff during the years discussed here.
1880-87, much of which consisted of disartic- The first attempt to reconstruct the skull of
ulated elements that were largely incomplete. Morosaurus {=Camarasaurus) was completed in
Noteworthy among these collections were two 1905 by Adam Hermann under the direction of
YPM AMNH
skulls of Camarasaurus from Quarry 3, Osborn (1906). The skull, 467, was col-
YPM
1907 and 1912 (Fig. 15, 29, 30, 33). 1907 lected from the Bone Cabin Quarry northeast of
was apparently nearly complete and well preserved Medicine Bow, Wyoming. Although the greater
when found, but many of the fragile elements part of this specimen is preserved, it is badly
fragmented as a result of careless collecting. The crushed and somewhat scattered. Each element
importance of both skulls lies in the extraordinary was disarticulated before the skull could be reas-
perfection in which the tightly articulated elements sembled and described. The figure published by
ofthe braincase were separated by Marsh’s prepar- Osborn (1906) gives the shape and general propor-
ators. Drawings of several of these, made under tions of the skull of Camarasaurus for the first
Marsh’s direction, were published by Ostrom and time, but it still contains many inaccuracies. It was
McIntosh (1966:pl. 3) and are reproduced here not possible at that time to identify all of the cra-
(Fig. 27, 28, 32). nial elements, but some of those are determined
Also noteworthy, several partial skulls of Cam- here. Disarticulated braincases andjaw elements of
arasaurus were collected about 6.5 km east of several other skulls of Camarasaurus (AMNH
Como Bluff from Quarry 13 (Ostrom and McIn- 607, 611, 618, 657, 673, 677, 6126) were also
tosh, 1966). Among these are some poorly pre- collected from the Bone Cabin quarry.
served jaws belonging to the juvenile, holotypic Very large collections of sauropod material
skeleton of Morosaurus lentus (YPM 1910). Poor made during 1899-1906 by Carnegie Museum
preservation, however, renders this material (Fig. (now known as Carnegie Museum of Natural
3) of little descriptive value. Of much greater History) from quarries on Sheep Creek and the
importance is the anterior portion of a very large Red Fork of the Powder River in Wyoming
.
4 BULLETIN CARNEGIE MUSEUM OE NATURAL HISTORY NO. 31
yielded few skull remains and only jaws of Cama- upper layer weathers quickly when exposed, the
rasaurus (CM 113, 312) (McIntosh, 1981). How- specimen was removed and prepared by the Monu-
ever, the well-known Carnegie Museum of Natural ment’s technicians F. (Tobe) Wilkins and F. Mc-
History quarry at what is now Dinosaur National Knight under the direction of the late Park Paleon-
Monument
north of Jensen, Utah, has yielded tologist T. E. White. White (1958) published a
some of the finest skull material of Camarasaurus detailed description of the braincase, commented
Well-preserved upper and lower jaws of a large on aspects of some of the other skull elements not
individual (CM 21751) were found in 1914. Two available to Gilmore (1925), and also provided an
years later a large but imperfect skull was found excellent series of illustrations.
associated with a disarticulated skeleton (CM Two other skulls of Camarasaurus were found
11393) that was first thought to be Apatosaurus. subsequently at Dinosaur National Monument.
Although preparation revealed this specimen to be Both are articulated with a series of cervical
a large Camarasaurus, the skull was recatalogued vertebrae and have been worked out in relief on
CM
12020, and a cast of it was used in the the quarry face as part of the Monument’s per-
mounted skeleton of Apatosaurus louisae (CM manent in situ exhibit. One of the skulls belongs
3018) which was described by Gilmore (1936). with the greater part of a partially disarticulated
This error has since been rectified (Berman and skeleton preserved in the stratigraphically higher
McIntosh, 1978; McIntosh, 1981). and more extensively quarried of the two bone-
In 1918 and 1919 two well-preserved, nearly bearing sandstone layers. Because all but that
complete skulls with mandibles were discovered as portion of the layer immediately supporting the
CM
part of articulated skeletons 11373 (now skeleton was excavated, the specimen appears on
USNM CM
1 3786) and 1 1338 at Dinosaur Nation- a strongly elevated area of the quarry face that is
al Monument. The larger of the two skulls (USNM referred to as the “hump” by the quarry personnel.
13786) was somewhat crushed and distorted. The The skull (DNM 1009) has, therefore, become
other skull (CM 11338), belonging to a very known as the “hump skull.” The anterior end of
young individual, is only slightly distorted (Fig. the neck and skull lay beside the distal end of the
ID) and reveals almost all of the external dermal right femur of this skeleton, necessitating the tem-
roof sutures. The lower jaws were firmly joined to porary removal of part of the femur by F. Wilkins
the skull, although displaced slightly to the right. in order to expose the skull. More recent addi-
In order to expose the palate and the medial sur- tional preparation revealed the skull to be well
faces of both jaws the left was removed. The preserved and therefore very important. Pressure
external features of the skull were first described from the femur at the time of deposition dislocated
by Gilmore (1925), who presented detailed figures some of the elements of the right side of the skull,
in which errors in the earlier reconstruction by and the anterior part of the skull remains covered
Osborn (1906) were corrected. About midway by matrix. The second skull (DNM 975) is artic-
through the period of 1909-22 of the large scale ulated with a series of eight cervical vertebrae and
excavation at the Dinosaur National Monument lies some distance to the east of the hump skull.
quarry by Carnegie Museum, two other skull spec- Because the second skull is positioned on the cliff,
imens (CM 21732, 21702) were collected that con- it is commonly referred to as the “cliff skull.” The
sisted mainly of jaw materials. right side and much of the posterior and dorsal
When operations at the Dinosaur National Mon- aspects have been exposed. Most of the skull is
ument quarry were resumed in 1952 under the articulated, but the right quadrate, quadratojugal,
auspices of the National Park Service, the first and a number of the palatal elements have been
specimen uncovered was a well-preserved, undis- displaced ventrally. Several of these bones have
torted, and largely disarticulated skull and series of been lost, whereas others (right pterygoid and pal-
vertebrae of Camarasaurus. This specimen (DNM atine) have been removed and fully prepared. The
28) was found in a soft layer of rock above the articulated dentary, surangular, and angular, and
two sandstone layers that have yielded the great the disarticulated prearticular and splenial of the
majority of specimens at the quarry. Because this right mandible were displaced from the skull and
.
1995 MADSEN ET kL.—CAMARASAURUS SKULL AND ATLAS-AXIS COMPLEX 5
were removed from the quarry for preparation and Although the bulk of the postcranial sauropod
have provided details about the relationships of the materials from the Cleveland-Lloyd quarry can be
lower jaw elements. The left mandible is articu- assigned to Camarasaurus, at least two other
lated with the skull, and its prepared medial sur- sauropod taxa have been recognized. The presence
face clearly reveals the sutural pattern. The excel- of Barosaurus is clearly indicated by a series of
lent preservation of the skull, together with its caudal vertebrae, a pair of ischia, and other
well-defined sutures, has provided invaluable in- elements, but this genus is a diplodocid (McIntosh
formation in this study. and Berman, 1975). Haplocanthosaurus also ap-
The latest and one of the most important dis- pears to be represented by three caudals, an
coveries of skull materials referable to Camara- ischium, and other elements. The skull of this
saurus was made at the Cleveland-Lloyd Dinosaur genus is not known, but, like other cetiosaurids, it
Quarry east of Cleveland, Emery County, Utah, by would be expected to possess broad, spatulate
a University of Utah field party under the direction teeth of the general type found in Camarasaurus.
of J. H. Madsen (Madsen and Stokes, 1972). This On the other hand, considering the pronounced
locality, most famous for its spectacular remains of differences between the postcrania of these two
Allosaurus (Madsen, 1976), has yielded disarticu- genera, their skulls would be expected to exhibit
lated and largely scattered skeletons of at least five much greater differences than those found among
different sauropods, only three of which can be the camarasaur skulls of the Cleveland-Lloyd
definitely assigned to Camarasaurus. Not only are quarry. Yet, it is known that, unlike the condition
the skeletons disarticulated but, with the exception found in most other vertebrate groups, the skulls
of the braincases, so are the skulls. Of the five of sauropod genera tend to be less diagnostic than
braincases, four (UUVP 3568, 4286, 10070, the vertebrae, as for example in Diplodocus and
10795) were found in the same general part of the Apatosaurus (Berman and McIntosh, 1978). Thus,
quarry and were all variously associated with other it is possible that one of the two aberrant
elements of the skull. The fifth braincase (UUVP Cleveland-Lloyd skulls may indeed pertain to
5684), which is assigned to Camarasaurus, was Haplocanthosaurus. It is important to emphasize
displaced from the other four, but is incomplete here that, of the four braincases with associated
and badly eroded. Other elements of the skull may skull elements, two cannot be distinguished from
UUVP
have been associated with 5684 but, as that of Camarasaurus As an example, they are
their positions in the quarry provide no help in indistinguishable from the seven skulls of Cam-
determining associations, they could also represent arasaurus from Dinosaur National Monument,
more than one individual. Some of the other disar- which incidentally do not exhibit the same range
ticulated cranial elements have been assigned of variation as the Cleveland-Lloyd skulls. Further,
separate catalogue numbers. This was done even the two aberrant Cleveland-Lloyd skull-bone
though three of the four braincases from the same assemblages differ more strongly from one another
part of the quarry were sufficiently separated from than either does from those assigned to Camara-
each other to allow their fairly certain association saurus. Thus, if the differences between the four
with many of the other disarticulated bones. It is skulls are not due to sexual or individual variation,
unfortunate that definite associations could not be the only alternative explanation would be that
made, since the resulting skull-bone assemblages three camarasaurid genera, including Camarasau-
exhibit subtle differences from each other, making rus, are represented in the Cleveland-Lloyd quarry.
it possible to recognize two aberrant skulls that Of the six well-established Morrison sauropod
may pertain to camarasaurid taxa other than Cam- genera, the only one that could possibly be repre-
arasaurus. These two skulls have a definite Cama- sented by one of the two aberrant, Camarasaurus-
rasaurus-Vik& structure that is similar to, for ex- like skull-bone assemblages is Brachiosaurus.
ample, those of Camarasaurus, Brachiosaurus, or However, the structure of the lacrimal in one of
Euhelopus and are, therefore, easily distinguishable the aberrant skulls (UUVP 10795) and the
from the skulls of such diplodocids as Diplodocus, braincase in the other (UUVP 3568 and associated
Apatosaurus, or Dicraeosaurus. elements) would seem to preclude this assignment.