Ontogeny and sexual dimorphism in Champsosaurs (Diapsida, Choristodera)
by Yoshihiro Katsura
A thesis submitted in partial fulfillment of the requirements for the degree Of Doctor of Philosophy in
Biological Sciences
Montana State University
© Copyright by Yoshihiro Katsura (1997)
Abstract:
Two species of Champsosaurus (Diapsida, Choristodera), possessing distinctive humeral and femoral
morphologies, occurred sympatrically in the Early Paleocene of Montana. The humeral ecto-and
entotuberosities of C. ambulator are situated more distally than those of C. laramieinsis. The femoral
internal trochanter is separated from the proximal articular surface in C. ambulator, but not in C.
laramiensis. The phylogenetic significance of these limb morphologies is questioned because similar
dimorphic variations occur in champsosaurs from other geological ages and locations.
Female champsosaurs may have been better adapted to a terrestrial life than males due to nesting
behavior, resulting in variable limb morphologies between sexes. The observed morphologic variations
are hypothesized to reflect sexual dimorphism. Pronounced muscular attachments and articular ends of
C. ambulator-shape humeri, demonstrating an adaptation for walking, is suggested to belong to
females. Similar morphological variations of humeri in extinct aquatic reptiles are also considered to
represent sexual dimorphism, supporting the hypothesis in champsosaurs. Extinct and extant terrestrial
reptiles with C. ambulator-like femora suggest that C. ambulator-shape femora demonstrate an
adaptation to a terrestrial environment, indicating that they belong to females. An extinct aquatic reptile
with C. laramiensis-like femora suggests that C. laramiensis-shape femora demonstrate an adaptation to
an aquatic environment, indicating that they belong to males. No significant variations of humeral and
femoral morphologies and cortical hyperplasia occurred in femora in juveniles suggests an aquatic
niche for them.
No microstructural variations were found between C. laramiensis-shape and C. ambulator-shape
femora, thereby between hypothesized sexes, in spite of their morphological differences. Thick
periosteal cortices observed in juvenile femoral diaphyses were replaced by dense spongy bone,
forming amedullar limb bones in late ontogenetic stages in both hypothesized sexes. ONTOGENY AND SEXUAL DIMORPHISM IN CHAMPSOSAURS
(DIAPSIDA, CHORISTODERA)
by
Y oshihiro K atsura
A thesis subm itted in partial fulfillm ent
of the requirem ents for the degree
Of
D octor of Philosophy
in
Biological Sciences
MONTANA STATE UNIVERSITY
B ozem an, M ontana
April, 1997
11
^
6
^
APPROVAL
of a thesis subm itted by
Y oshihiro K atsura
This thesis has been read by each m em ber of the thesis
com m ittee and has been found to be satisfactory regarding content,
English usage, form at, citations, bibliographic style, and consistency,
and is ready for subm ission to the College of Graduate Studies.
j-Chairperson, Graduate Committee
C o-C hairpersoi^G raduate Committee
D ate
Approved for the D epartm ent of Biology
V/ltY tz
D ate /
Head, Biology D epartm ent
Approved for the College of Graduate Studies
--------
D ate
G raduate Dean
Ill
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IV
ACKNOWLEDGMENTS
This thesis w ould not have been finished w ithout the support
of m any people.
I am m ost grateful to D rs. John R. Horner, Harold D.
Picton, M atthew T. Lavin and Bruce R. Erickson and Ms. Susan K.
G ibson who supervised this thesis project and provided m uch useful
advice as m em bers of my thesis com m ittee.
I appreciate Dr. James G.
Schm itt as the substitute of my thesis com m ittee and Dr. D aniel L.
Shaffer as the graduate representative.
I would like to thank all the
staff and volunteers of the M useum of the Rockies and students
studying under Dr. John R. H orner for their help, especially Ms.
Frankie Jackson for illustrations, Mr. Bruce Selyem for photographs,
and Ms. C eleste H orner for com puter assistance.
I thank the A m erican M useum of N atural H istory, Brigham
Young U niversity, Canadian M useum of N ature, M useum of
Paleontology at U niversity of California at Berkeley, M useum of the
Rockies, Peabody M useum at Yale U niversity, Royal O ntario Museum,
R oyal Saskatchew an M useum , Royal T yrrell M useum, Science
M useum o f M innesota, and Sm ithsonian Institution, for allow ing me
to study their collections.
Ms. Barbara Lee, Dr. John R. Horner, the
M useum of the Rockies provided financial aid for my study.
Finally I thank my fam ily, especially my m other, for giving me
the chance to study in the U nited States.
support helped m e to com plete my thesis.
Their financial and spiritual
V
TABLE OF CONTENTS
Page
ACKNOWLEDGMENTS.............................................................................................. iv
LIST OF FIGURES...............................................
ABSTRACT..................................................
INTRODUCTION....................
vi-viii
ix
I
ABBREVIATIONS........................................................................................................ 13
MATERIALS AND M ETHODS..................................................................................14
RESULTS........................................................................................................................23
M orphological Variations of Champsosaurs ......................................... 23
M icrostructures of Cham psosaur H um eri and Fem ora ................. 36
DISCUSSION.................................................
43
Ecological Cause for Sexual Dim orphism in Champsosaurs ....... 43
M icro structural V ariations of C ham psosaur
Humeri and F em o ra...........................................................................................56
Suggestions......................................................................................................... 60
REFERENCES CITED .................................................................................................. 63
APPEND IX.................................................................................................................... 71
M easurements of Champsosaur Hum eri ................................................. 71
M easurements of Champsosaur Fem ora ................................................. BI
M easurem ents of Champsosaur Lim b Bones ....................................... 91
vi
LIST OF FIGURES
F ig u re
Page
1.
Reconstruction of the skeleton of ChampsosaUrus ............................ 2
2.
Cladogram of D iapsida suggested by Evans and
Hecht (1993).........................................................................................................4
3.
C ladogram of Choristodera suggested by Evans and
Hecht (1993).........................................................................................................6
4.
C orrelation and stratigraphic relations of U pper Cretaceous
and Paleocene rocks in eastern M ontana and w estern
N orth D akota w ith cham psosaur species (Sloan, 1969;
Erickson, 1972, 1981; Gill and Cobban, 1973; Jacob,
1976; Moore, 1976)............................................................................................. 9
5.
Diagrams of m easurem ents............................................................................. 15
6.
H istogram s of two m orphological shapes of hum eri and
fem ora form the Judith River Form ation of D inosaur
Provincial Park, Alberta, C a n a d a ......... ....................................................... 20
7.
H istogram s of two m orphological shapes of hum eri and
fem ora form the Hell Creek and Tullock form ations of
northeastern M o n tan a.......................................................................................21
8.
H istogram s of two m orphological shapes of hum eri and
fem ora form the Tongue River and Sentinel Butte
formations of western North D a k o ta ....................
9.
22
Hum erus and fem ur of juvenile champsosatirs ................................... 24
v ii
LIST OF FIGURES (Continued)
F ig u re
Page
10.
P osterior view of hum eri of the type specim ens of
Champsosaurus laramiensis and
Champsosaurus ambulator .......................................................................... 25
11.
V entral view of hum eri of the type specim ens of
Champsosaurus laramiensis and
Champsosaurus ambulator ............................................................................. 27
12.
D im orphic variations of hum eral proxim al heads in
champsosaurs (posterior view) ..................................................................... 28
13.
V entral view of fem ora of the type specimens of
Champsosaurus laramiensis and Cham psosaurus
am bulator with the diagram s of the proxim al
h ead s.................................................................................................................... 30
14.
D im orphic variations of fem oral proxim al heads in
champsosaurs (ventral v ie w ) ......................................................................... 31
15.
M orphological variations of pelvic bones in
champsosaurs (dorsal v ie w )...........................................................................34
16.
M orphological variations of sacral vertebrae in
champsosaurs (ventral v ie w )........................................
17.
35
T ransverse sections of C. Zflramzenszs-shape hum eri
in interm ediate-sized (U C M P142200) and large
(UCMP142206) cham psosaurs...................................................................... 37
V lll
LIST OF FIGURES (Continued)
F ig u re
Page
18.
T ransverse sections of C. ambulator-shape hum eri
in interm ediate-sized (M O R-FU -82) and large
(SMM P64.10.1) cham psosaurs.................................................................... 38
19.
Juvenile cham psosaur fem ur (U C M P142195) w ith
longitudinal and transverse sections ........................................................ 39
20.
C. laramisensis-shape fem ur (M O R740) with
longitudinal and transverse sections ........................................................ 40
21.
C. ambulator-shape fem ur (M O R697-G -13) with
longitudinal and transverse sections ........................................................ 41
22.
Fem ur of Varanus (Squam ata, V aranidae)
(R om er, 1956) with com parison of
C. ambulator-shape fe m u r.............................................................................. 45
23.
Fem ur of Corosaurus alcovensis (Sauropterygia,
N o th o sauriform es) (Storrs, 1991) w ith com parison
of C. laramiensis-shape fe m u r...................................................................... 47
24.
Sexual dim orphic variations of hum eri in
p ach y p leu ro sau rid s (D iapsida, S auropterygia)
(Rieppel, 1989 and Sander, 1 9 8 9 )............................................................ 49
IX
ABSTRACT
Two species of Champsosaurus (D iapsida, C horistodera),
possessing distinctive hum eral and fem oral m orphologies, occurred
sym patrically in the E arly Paleocene of M ontana. The hum eral ectoand entotuberosities of C. ambulator are situated m ore distally than
those o f C. laramieinsis. The fem oral internal trochanter is separated
from the proxim al articular surface in C. ambulator, but not in C .
laram iensis. The phylogenetic significance of these lim b
m orphologies is questioned because sim ilar dim orphic variations
occur in cham psosaurs from other geological ages and locations.
Fem ale cham psosaurs m ay have been better adapted to a
terrestrial life than m ales due to nesting behavior, resulting in
variable lim b m orphologies betw een sexes. The observed
m orphologic variations are hypothesized to reflect sexual
dim orphism .
P ronounced m uscular attachm ents and articular ends
of C. ambulator-shape hum eri, dem onstrating an adaptation for
walking, is suggested to belong to fem ales. Sim ilar m orphological
variations o f hum eri in extinct aquatic reptiles are also considered to
rep resen t sexual dim orphism , supporting the hypothesis in
cham psosaurs. E xtinct and extant terrestrial reptiles w ith C .
am bulator-like fem ora suggest that C. ambulator-shape fem ora
dem onstrate an adaptation to a terrestrial environm ent, indicating
that they belong to fem ales. An extinct aquatic reptile with C .
laram iensis-like fem ora suggests that C. laramiensis-shape fem ora
dem onstrate an adaptation to an aquatic environm ent, indicating
that they belong to males. No significant variations of hum eral and
fem oral m orphologies and cortical hyperplasia occurred in fem ora in
juveniles suggests an aquatic niche for them.
N o m icrostructural variations w ere found betw een C .
laram iensis-shape and C. ambulator-shape fem ora, thereby betw een
hypothesized sexes, in spite of their m orphological differences. Thick
p erio steal cortices observed in juvenile fem oral diaphyses were
replaced by dense spongy bone, form ing am edullar lim b bones in
late ontogenetic stages in both hypothesized sexes.
I
INTRODUCTION
Cham psosaurus (D iapsida, C horistodera) was a sem i-aquatic,
fresh-w ater reptile found in rocks of the Late C retaceous through
E arly Eocene of N orth Am erica and the Paleocene of Europe.
The
dorsoventrally flattened body of C ham psosaurus is
hydrodynam ically suited to an aquatic life, w hich is com parable to
m odern crocodiles (Figure I).
An elongated snout w ith m any sharp
teeth is observed com m only in fish-eating anim als, such as gharial
(Gavialis gangeticus), the fresh-w ater, long-snouted crocodile of
India.
Therefore, a piscivorous diet is suggested for cham psosaurs.
G igantism occurred in cham psosaurs (L angston, 1958), and therefore,
the size o f body varied w ithin species.
A dult cham psosaurs in the
E arly Paleocene are estim ated to have been two to three m eters in
le n g th .
In 1876, Cope described an unknow n fossil vertebrate
specim en from the Judith R iver Form ation of north-central M ontana,
assigning it to the order C horistodera, fam ily C ham psosaurdiae,
Champsosaurus annectens.
The presence of two sets of temporal
fenestrae clearly indicates that the order C horistodera belongs to
D iapsida, a subclass w ithin the class Reptilia.
However, its
relationship am ong D iapsida rem ains debatable.
R om er (1956, 1966)
placed C horistodera in the order E osuchia (Reptilia; L epidosauria).
E rickson (1972) included it w ithin the infraclass L epidosaurom orpha.
2
Figure I.
Reconstruction of the skeleton of C ham psosaurus.
It is based on Brown (1905) and Erickson (1985).
3
Using cladistic analysis, Benton (1985) placed the fam ily
C ham psosauridae incertae sedis w ithin the infraseries D iapsida.
E rickson (1987) recategorized the order in the A rchosaurom orpha.
C arroll (1988) stated that choristoderes w ere derived from
eosuchians, but his non-cladistic classification placed the order
incertae sedis w ithin the subclass D iapsida.
Evans (1988) included
C h o risto d era w ithin the superorder A rchosaurom orpha using
cladistic analysis.
How ever, Evans and H echt (1993) excluded
C h o risto d era from both A rchosaurom orpha and L epidosaurom orpha
and considered it an early off-shoot w ithin D iapsida w ith studies of
the new genus, L azarussuchus, described by H echt (1992) (Figure 2).
C arroll (1988) included five genera in the fam ily
C ham psosauridae, Champsosaurus (Cope, 1876), Simoedosaurus
(G ervais, 1877), Eotomistoma (Young, 1964), Tchoiria (Efim ov, 1975),
and, K hurendukhosaurus (Sigogneau-R ussell and Efim ov, 1984).
C ham psosaurus occurred from the Late Cretaceous to E arly Eocene in
N orth A m erica and Europe.
Sim oedosaurus is found in the Upper
Paleocene o f North Am erica and Europe.
Tchoiria and
Khurendukhosaurus are found in the Low er Cretaceous rocks of
M ongolia.
The U pper Cretaceous of China produced Eotom istom a
w hich Young (1964) originally described as a crocodilid.
Sigogneau-
R ussell (1981) recognized that the type specim en of E otom istom a,
represented by the right half of a snout, belonged to a
cham psosaurid and therefore, described it as a new genus,
Ikechosauru s.
Carroll (1988) persisted in the use of the original
genus nam e, E otom istom a, but Evans (1989, 1990, 1991) and Hecht
4
Node
Node
Node
Node
Node
I: Lower and upper temporal fenestrae present; suborbital
fenestra present; paroccipital process reaches suspensorium.
2: Ventral flanges on parietal;anteroventral process of squamosal
narrow; trunk ribs mostly holocephalous; humeral ends robust.
3: Postparietal small or absent; tabulars absent; paroccipital
process/cheek contact strong and broad; stapes slender and
imperforate; no cleithrum; lateral centrale of manus small or absent;
loss or fusion of fifth distal tarsal; hooked fifth metatarsal.
4; Prefrontal/nasal suture anterolaterally oriented; squamosal largely
confined to dorsal half of skull; no tooth row on pterygoid flange;
quadrate emargination present; well-developed retroarticular process.
5; Premaxilla with enlarged dorsolateral flange; external nares close to
midline; pineal foramen reduced or absent; vertebrae not notochordal;
dorsal transverse processes relatively long; cervical ribs
dichocephalous; loss of entepicondylar foramen; no foramen between
ulnare and intermedium; loss of medial centrale; presence of lateral
calcaneal tuber; concave/convex joint between astragalus and
calcaneum; metatarsal 4 elongated.
Figure 2.
Cladogram of Diapsida suggested by Evans and Hecht
(1 9 9 3 ).
5
(1992) used the new genus name.
Efim ov (1983) described a new
genus, Irenosaurus, recovered from the Low er Cretaceous of
M ongolia.
A lthough choristoderes w ere once represented by these five
m oderate-sized genera living from the Cretaceous to E arly Eocene,
th eir phylogeny w as recently reversed based on cladistic analyses.
C teniogenys, from the M iddle Jurassic of the United States, England
and Portugal, was originally identified as a lizard by G ilm ore (1928).
U sing new m aterial, the cladistic analysis suggested by Evans (1989)
indicates that the genus belongs to the order Choristodera.
Evans
(1990) classified the choristoderes cladisatically w ith 53 characters
based prim arily on the skull m orphologies and recategorized these
choristoderes into two groups, Cham psosauridae (Cham pso sa u rus and
Tchoiria) and Sim oedosauridae (Sim oedosaurus and Ikechosaurus).
H echt (1992) described a new choristodere, L a za ru ssu ch u s
inexpectatus, from the Oligocene of France, placing it within
C horistodera using the phylogeny of Evans (1990) w ith five
additional characters (Figure 3).
The phylogenetic analysis indicates
th at the genus is m ost prim itive among choristoderes although it
occurred geologically later than the other genera.
H uene (1935) described Pachystropheus
U pper T riassic of Germany, as a choristodere.
rhaeticus, from the
Rom er (1966)
tentatively placed this genus in the fam ily C ham psosauridae or
Sphenodontidae (L epidosauria; R hynchocephalia).
C arroll (1988)
assigned it w ith som e uncertainty to the fam ily Sphenodontidae
(L epidosaurom orpha; Sphenodonta), and Storrs and G ow er (1993)
6
Node I: Elongation of preorbital skull; prefrontals meet in midline; pineal
foramen lost; skull dorsoventrally compressed; loss or reduction of
interpterygoid vacuity; reduced nasals; long, slender jaws with extended
symphysis; first caudal incorporated into sacrum; caudal zygapophyses
nearly or fully vertical.
Node 2: Nares confluent; posterior displacement of choana; loss of metakinesis;
palatal tooth batteries; hemispherical occipital condyle; notochordal
canal closed; neurocentral sutures open; sacral and caudal ribs free;
large free atlas pleurocentrum; ungual phalanges broad and low with
reduced flexor tubercles.
Node 3: Nasals fused; premaxilla without trace of dorsal process; small dorsally
directed orbits; large posteriorly extended supratemporal fenestra;
presacral vertebrae short and spool-like.
Node 4: Narrow tapering preorbital skull; dentary symphysis extensive;
postorbital free but excluded from orbit; reduced interpterygoid vacuity
enclosed by pterygoids.
Node 5: Tooth sockets transversely widened; relatively short, powerful
preorbital skull; postorbital and postfrontal fused.
Figure 3.
Cladogram of Choristodera suggested by Evans and Hecht
(1 9 9 3 ).
7
later placed it back w ithin the C horistodera after studying new
Pachystropheus rhaeticus m aterial from the U pper T riassic of
The m odified hum erus of P achystropheus
England.
indicates that
the geologically oldest choristodere was m ore adapted to an aquatic
life than the others (Storrs and Gower, 1993).
The cladogram of
C horistodera excluded P achystropheus because of the incom pleteness
o f the specim ens, especially the lack of the skull.
K huren d u kh o sa u ru s and Iren o sa u ru s rem ain in an unknown
position w ithin C horistodera because of the lack of adequate
m aterials.
A fter exam ination of a new specim en, Brinkm an and Dong
(1993) suggested that Ikech o sa u ru s is m ore closely related to
C ham psosaurus than Sim oedosaurus because of the five derived
cranial characters w hich Ikechosaurus and C ham psosaurus share.
H ow ever, their phylogenetic relationship rem ains debatable.
D uring m ost of the C retaceous, the W estern Interior Seaway
extended north-south from the G ulf of M exico to the A rctic, dividing
the N orth Am erican continent into tw o m ain land m asses (Kauffm an,
1977).
As this seaw ay gradually w ithdrew during the Late
C retaceous and E arly Paleocene, extensive basins opened on the
eastern side of the highlands now represented by the Rocky
M ountains.
A lluvial system s were well developed there.
The
biogeographic distrib u tio n of cham psosaurs ranged from present-day
Alberta, Canada to New M exico.
N o cham psosaurs have been
reported from the east side of the W estern Interior Seaway.
Johnson and H ickey (1990) suggested, based on studies of the
fossil flora, that this area changed to a sub-tropical or warm clim ate
8
in the E arly Paleocene.
W olfe and U pchurch (1986) considered that
the paleoclim ate, in itially represented by sub-hum id, notophyllous,
broad-leaved evergreen forests during the Late C retaceous changed
to successional m esotherm al deciduous forests in the E arly Paleocene.
T hese clim ates provided an ideal habitat for aquatic and riparian
vertebrates.
Cham psosaurs represented one of the m ain com ponents
o f the riparian fauna from the L ate Cretaceous throughout the
Paleocene (Estes et al., 1969; Estes and Berberian, 1970; Russell,
1975; Estes, 1976; Lupton et al., 1980; Erickson, 1982; Hutchison,
1982; B artels, 1983; Fiorillo, 1989; K atsura, 1992).
Figure 4 shows
the correlation and stratigraphic relationships of U pper Cretaceous
and Paleocene rocks in eastern M ontana and w estern N orth Dakota.
A ll know n cham psosaur specim ens have been recovered from
terrestrial rocks except for some isolated elem ents found in the
m arine Bearpaw Shale (Figure 4).
E rickson (1972) stated that these
bones w ere carried to the sea by fluvial systems.
The Two M edicine Form ation (Late Cretaceous) produces
cham psosaur m aterial but not as abundantly as the Judith River
Form ation (Late C retaceous) although deposition of the two
form ations are geologically equivalent.
The Two M edicine Form ation
represents an upland deposition and is characterized by shallow
stream channels w ith shallow floodbasin ponds and lakes.
The
clim ate was sem i-arid and seasonal (Rogers, 1993 a; V arricchio,
1993).
In contrast, the Judith R iver Form ation was characterized by
w ider and deeper stream channels w ith swamps and floodplain
ponds on the coastal plain, and its clim ate was humid (Rogers,
9
Series
Western
North Dakota
Eastern Montana
Champsosaurs
Sentinel Butte Fm.
gigas
tenuis
Tongue River Fm.
Lebo Fm.
Ludlow
Cannonball
Tullock Fm.
ambulator
laramiensis
Hell Creek Fm.
Fox Hill Ss.
albertensis
Bearpaw S h .
Pierre S h .
C. natator
Judith River Fm.
Figure 4.
C orrelation and stratigraphic relations of U pper
Cretaceous and Paleocene rocks in eastern M ontana and
w estern N orth Dakota with cham psosaur species (Sloan,
1969; Erickson, 1972, 1981; Gill and Cobban, 1973;
Jacob, 1976; M oore, 1976).
10
1993 a, b; V arricchio, 1993). T herefore, the difference in abundance
o f cham psosaurs betw een these tw o form ations m ay reflect a
preference o f habit or a preservational bias.
The Hell Creek ,
Form ation (Late C retaceous) produces equivalent num bers of
cham psosaur specim ens as the overlying Fort U nion Group
(P aleo cen e).
B oth represent a flu vial-dom inated environm ent
(Fastovsky and Dott, 1986; Fastovsky, 1987; Rigby and Rigby, 1990;
K atsura, 1992).
Cham psosaurs have been found in a variety of
alluvial system s, including channel stream s, sw am ps, and lakes.
C ham psosaurs are easily identified because of the unique bone
m orphology.
H ow ever, the m orphology of cham psosaurs
dem onstrates little d iversity throughout their ev olutionary history
because they w ere highly adapted to their living environm ent.
Therefore, it is very difficult to differentiate species w ithout
adequate m aterial.
Sigogneau-R ussell and Baird (1978) recognized
the existence of Sim oedosaurus in N orth America, based on elements
from the U pper Paleocene of the Bighorn Basin in W yom ing and
M ontana.
Erickson (1987) described a new species, Sim oedosaurus
dakotensis, from the first and only near-com plete specim en from the
U pper Paleocene of N orth Dakota.
In spite of the distinctive
differences of their skull m orphologies and sizes, it is difficult to
distinguish Sim oedosaurus from C ham psosaurs because of the
sim ilarity of the postcranial skeletons of the two genera.
Therefore,
some Sim oedosaurus were possibly m isidentified as C ham psosaurus
(E rickson, 1972, 1987).
Cope (1876, 1881, 1882), Brown (1905), and Parks (1927,
1933) nam ed thirteen species of C ham psosaurus.
H ow ever, many
w ere based on inadequate specim ens, including the first species,
Champsosaurus annectens, which was represented by an axis
centrum and associated vertebrae.
Brow n (1905) and R ussell (1956)
pointed out this nom enclature problem .
E rickson (1972) categorized
all previously described specim ens into four species, C. natator, C .
albertensis , C. Iaramiensis and C. ambulator, and described a new
species, C. gigas.
tenuis
Erickson (1981) described another new species, C .
(Figure 4).
C. natator was found in the Belly River Form ation (Late
C retaceous) in A lberta, Canada (Parks, 1933).
C ham psosaurs from
the Judith R iver (O ldm an) Form ation (Late Cretaceous) of southern
A lberta and northw estern M ontana are considered to belong to this
species.
C. albertensis occurred in the Edm onton Form ation (Late
Cretaceous) in Alberta (Parks, 1927).
C. Iaramiensis was found in the
H ell Creek, Lance, Frenchm an (Late Cretaceous) and T ullock (Early
P aleocene) form ations in Saskatchew an, W yom ing, and eastern
M ontana (Brown, 1905).
Cham psosaurs found in the San Juan
Form ation (Early Paleocene) in New M exico are also considered C.
Iaram iensis (Erickson, 1972).
C. ambulator is a representative
species o f the T ullock Form ation in northeastern M ontana (Brown,
1905; Erickson, 1972).
C. tenuis was recovered from Bullion Creek
(Tongue R iver) Form ation (Late Paleocene) of North D akota (Erickson,
1981).
C. gigas was found in the Bullion Creek (Tongue River) and
Sentinel B utte form ations (Late Paleocene) in N orth D akota (Erickson,
12
1972).
This species also occurred in the Polecat Bench and Bear
C reek form ations (Late Paleocene) in northw estern W yom ing and
south-central M ontana sym patrically w ith S im o ed o sa u ru s
(Sigogneau-R ussell and Baird, 1978).
Two species, C. Iaramiensis and C. ambulator, o c c u rre d
sym patrically in the T ullock Form ation of northeastern M ontana
(Figure 4).
1905).
They possess distinctive bone m orphologies (Brown,
In this study m orphological variations of postcranial
skeletons of these two species, especially the hum eri and fem ora,
w ere reexam ined to discover the possible causes of variation and
w hat it m ight indicate about paleoecology.
M orphological variations
in cham psosaurs from the other form ations and m icrostructures of
hum eri and fem ora of these two species were also studied.
13
ABBREVIATIONS
AMNH;
A m erican M useum of N atural H istory
MOR;
M useum of the Rockies
NMC;
C anadian M useum of N ature
(form er name; N ational M useum of Canada)
ROM;
Royal O ntario M useum
RTM.P;
Royal T yrrell M useum of Paleontology
SMM;
Science M useum of M innesota
UCMP;
M useum of Paleontology at U niversity of C alifornia at
B e rk e le y
USNM;
U nited States N ational M useum (Sm ithsonian Institution)
YPM-PU;
Peabody M useum at Y ale U niversity (Princeton
U niversity
collections)
14
MATERIALS AND METHODS
H um eri and fem ora in cham psosaurs from geographically
lim ited areas w ere analyzed statistically.
Three geographical areas
representing different geological ages and form ations included: the
Judith R iver Form ation in D inosaur Provincial Park in southern
Alberta, in which C. natator is representative; the H ell Creek and
T ullock form ations in northeastern M ontana, in which C. ambulator
and C. Iaramiensis occurred; and the Tongue R iver and Sentinel Butte
form ations of western N orth Dakota, in which C. gigas was found. C .
albertensis and C. tenuis were not taken in consideration in this
study because no identifiable specim ens have been found except for
the type specim ens.
Specim ens from the same form ations of the
other areas and the other form ations, w hich are geologically
equivalent to the form ations m entioned above, w ere also studied.
H ow ever, these specim ens were not used for the statistical analyses.
L ength and w idth of proxim al heads of hum erus and fem ur
w ere m easured.
M ost m easurem ents w ere m ade w ith a slide caliper
in a tenth of a m illim eter scale.
Some long bones w ere measured
w ith m illim eter-scaled graph paper.
A ll lengths of hum eri and
fem ora w ere m easured betw een perpendiculars to the longitudinal
axes of the bones (Figure 5).
W idth of the hum eral proxim al head
was m easured by a line drawn betw een the m axim um points
perpendicular to the longitudinal axis (Figure 5).
W idth of the
I5
Humerus
(P o sterio r view )
Figure 5.
Fem ur
(V entral view )
D iagram s of m easurem ents. (W , width; L, length)
I6
fem oral proxim al head was m easured by a line draw n betw een the
points of greatest distances (Figure 5).
The line is perpendicular to
the longitudinal axis in the proxim al region rather than the diaphysis
because cham psosaur fem ur is curved and the shafts o f m any of the
m easured fem ora w ere not preserved.
All of the m easurem ents of
hum eri and fem ora are listed in the A ppendix.
L ength/w idth ratios
o f hum eri and fem ora w ere also calculated.
The other lim b bones, such as radius, ulna, tibia, and fibula, of
associated and articulated cham psosaurs w ere also m easured
(A ppendix).
A ll lengths of these lim b bones w ere m easured between
perpendiculars to their longitudinal axes.
The ratios of length of
these elem ents, including hum eri and fem ora, w ere also calculated.
A ll m easured specim ens from the three localities w ere plotted
in separate histogram s (Figure 6, 7, 8).
M icro site localities represent
m ixed v erteb rate assem blages, including m any cham psosaur
elem ents.
This taphonom ic condition prohibits positive identification
of lim b bones representing a single individual, even when
m orphology and size are sim ilar.
Therefore, each lim b bone was
counted as one, and articulated/associated specim ens w ith
preservation of both lim bs counted as two.
fem ora and hum eri rarely occurs.
Preservation of com plete
Therefore, the w idth of the
proxim al head is used in statistical analyses for determ ining growth
rath er than length.
A ll m easured hum eri were categorized into tw o groups, C.
Iaram iensis- and C. a m W afo r-sh a p es, according to the positions of
ecto- and entotuberosities.
The ecto- and entotuberosities of
17
C. ambulator-shape hum eri is located more distally than those of C .
Ztirtimzens1Zj1-Shape ones.
All m easured fem ora w ere also categorized
into two groups, C. laramiensis-shap& and C. ambulator-shape,.
The C .
am bulator-shape group includes fem ora in which internal
trochanters separate from the proxim al heads and the area betw een
them is covered by com plete or patchy periosteal bone.
A patchy
appearance of the periosteal bone is assum ed to be a result of
w eathering.
The fem ora, whose internal trochanters are located
distally but do not separate from the proxim al heads w ith periosteal
bones, w ere also categorized into the C. ambulator-shape group
because the periosteal bones are assum ed to have been peeled off by
w e a th e rin g .
B esides hum eri and fem ora, the m orphologies of other parts of
skeletons were also studied.
The type specimens of C. Iaramiensis
(AM NH982) and C. ambulator (AM NH983) were the focus of the
m orphological com parison because they are m ost com plete.
ch am p so sau r skeletons, esp ecially
a rticu lated /asso ciated
Other
specim ens
w ere also exam ined for this study.
C ham psosaur hum eri and fem ora w ith different m orphologies
and variation of size from the Hell Creek and Tullock form ations of
northeastern M ontana w ere included in the histological study.
The
bones for this study were photographed, and then m olds and casts of
the bones were m ade.
The bones were then em bedded in a polyester
resin under vacuum and cut.
The sliced bones were glued to glass
slides w ith tw o-ton epoxy and then ground.
Super glue and five-
m inute epoxy were occasionally used to reinforce the sliced bones.
18
T ransverse sections of C. ambulator-shscpQ and C. Iaramiensisshape hum eri of interm ediate (sub-adult) and large (adult)
cham psosaurs w ere m ade perpendicular to the shafts.
Because
hum eri w ith com pletely preserved diaphyses are very rare, the
highest peak on the deltopectoral crest, in the m etaphyseal region,
was chosen for the transverse sections.
L ongitudinal and transverse sections w ere m ade from one
sm all (juvenile) fem ur and two large (adult) fem ora w ith different
m orphologies.
The transverse sections w ere m ade m id-w ay betw een
the proxim al and distal ends and perpendicular to the diaphyses.
B ecause the distal half of the juvenile fem ur was not preserved, the
ratio betw een length and w idth of the proxim al head of a com plete
and sim ilar sized fem ur was used to estim ate the appropriate
position for m aking the transverse section.
A fter the m id-diaphyses were cut for m aking transverse
sections, both proxim al and distal parts of the fem ora w ere cut
dorsoventrally to m ake the longitudinal sections.
The longitudinal
section o f the proxim al half of the bone was made on a line drawn
betw een the m iddle of the m id-diaphyses and the m iddle point of
the proxim al end.
That of the distal half was m ade on a line drawn
betw een the m iddle of the m id-diaphyses and the ventral tip of the
distal end.
Because the femur of C ham psosaurus is curved and
tw isted, the longitudinal sections of the proxim al and distal halves
are not perpendicular to the transverse sections.
The thin sections
w ere then exam ined w ith an optical m icroscope and photographed.
19
The type specim en of C. natator, which was originally given the
specim en num ber ROM 856, was later stored in the R oyal Tyrrell
M useum and given a new specim en num ber, RTM .P81.47.1.
H ow ever, som e fragm ents of the skeleton, including the hum erus, are
still stored in the Royal Ontario M useum and have the original
specim en num ber.
In this study, the new specim en num ber,
R T M .P81.47.1, was used.
20
Number of specimens
C. ambulator- shape
C. Iaramiensis- shape
10.0
20.0
30.0
40.0
50.0
Number of specimens
Width of proximal heads of humeri
C. ambulator -s h a p e
C. Iaramiensis- shape
10.0
20.0
30.0
40.0
50.0
W idth of proximal heads of femora
Figure 6.
H istogram s of two m orphological shapes of hum eri and
fem ora from the Judith R iver Form ation of D inosaur
Provincial Park, Alberta, Canada.
21
Number of specimens
C. ambulator- shape
C. Iaramiensis- shape
10.0
20.0
30.0
40.0
50.0
Width of proximal heads of humeri
Number of specimens
C. ambulator- shape
n rr
C. Iaramiensis- shape
10.0
20.0
30.0
40.0
50.0
Width of proximal heads of femora
Figure 7.
H istogram s of two m orphological shapes of hum eri and
fem ora from the Hell Creek and Tullock form ations of
n o rth ea stern M ontana.
22
Number of specimens
C. ambulator- shape
C. Iaramiensis- shape
20.0
30.0
40.0
50.0
W idth of proximal heads of humeri
Number of Specimens
C. ambulator- shape
C. Iaramiensis- shape
20.0
30.0
40.0
50.0
(cm)
W idth of proximal heads of femora
Figure 8.
Histogram s of two m orphological shapes of hum eri and
fem ora from the Tongue River and Sentinel Butte
form ations of western North Dakota.
23
RESULTS
M orphological V ariations of Cham psosaurs
The hum erus of C ham psosaurus is robust and twisted.
The
proxim al and distal articular ends are heavily developed, but the
shaft is fragile and dorsoventrally flattened.
Hum eri show the m ost
diagnostic skeletal features for differentiating species in
cham psosaurs (E rickson,
1972).
N o significant dim orphic variations of hum eral m orphologies
occurred in sm all cham psosaur individuals from all three localities
(Figure 6, 7, 8).
The ecto- and entotuberosities are located
proxim ally on the hum eri, appearing rounded or sub-rounded in
shape (Figure 9).
In the type specimen of C. Iaramiensis (A M N H 9 8 2 )
w hich is considered an adult individual, ecto- and entotuberosities of
the hum erus sit close to the proxim al head, appearing rounded in
shape (Figure 10).
In contrast, those in the type specim en of C.
ambulator (AM NH983) are located distally and give the head a
triangular shape (Figure 10).
The proxim al articular surface of C .
am bulator appears m ore oval than that of C. Iaramiensis because of
the distal location of these tuberosities. Separations of ecto- and
entotuberosities from the proxim al head appear to vary even in C .
am bulator-shape hum eri.
The separations of the tuberosities from
the hum eral proxim al head in the type specim en of C. ambulator
24
H u m e ru s
(R T M .P 8 6 .3 0 .1 5 5 )
Figure 9.
Fem ur
(U C M P 142195)
H um erus and fem ur of ju v en ile cham psosaurs.
(H um erus, posterior view; fem ur, ventral view)
(Scales, 2 cm)
25
Champsosaurus laramiensis
Champsosaurus ambulator
(AM NH982)
(A M N H 983)
Figure 10. Posterior view of humeri of the type specim ens of
Champsosaurus laramiensis and Champsosaurus
am bulator. (Scale, 5 cm)
26
(A M NH983) is m ore pronounced than any other individuals (Figure
10 ).
C. ambulator-shape hum eri are generally m ore robust than C .
Iara m ien sis-shape hum eri, and the m uscular attachm ents are m ore
prom inent (Figure 10, 11).
For exam ple, the deltopectoral crest of
the C. ambulator-shape hum erus (A M N H 983) is m ore pronounced
than that of the C. laramiensis-shape hum erus (A M N H 982) (Figure
11).
The distal articular end of the C. ambulator-shape
hum erus,
especially the ectocondyle, is m ore developed than that of the C .
laram iensis-shape hum erus (Figure 11).
The hum eral m orphologies of the type specim ens of C. natator
(RTM .P81.47.1) and C. gigas (SMM P72.2.1) are similar to those of C.
Iaramiensis (AM NH983).
However, C. ambulator-shape hum eri also
occurred in the localities where these tw o type specim ens were
found, and the described hum eral dim orphs were also found in
cham psosaurs from the Two M edicine Form ation of northw estern
M ontana (Figure 12).
The fem ur of C ham psosaurus is long and slender.
20-35% longer than the hum erus and also twisted.
articulation is not w ell-differentiated.
It is about
The distal
The w ell-developed internal
trochanter is located ventrally on the fem ur.
O ccasionally fem ora
w ith relativ ely enlarged shafts are found.
N o significant dim orphic variations of fem oral m orphologies
occurred in sm all cham psosaur individuals from any of the three
localities (Figure 6, 7, 8).
The internal trochanter of the exam ined
27
Champsosaurus laramiensis
Champsosaurus ambulator
(AM NH982)
(A M N H 983)
Figure 11. V entral view of humeri of the type specim ens of
Champsosaurus laramiensis and Champsosaurus
am bulator. (Scale, 5 cm)
(Dc, deltopectoral crest; Ec, ectocondyle)
28
(M O R 424)
(M O R969)
Tw o M edicine Form ation in northw estern M ontana
(R T M .P 85.67.21)
(R T M .P .92.30.202)
Judith River Form ation in D inosaur Provincial Park,
southeastern A lberta, C anada
(SM M P77.33.24)
(SM M P80.11.4)
Tongue R iver Form ation in western N orth D akota
Figure 12. D im orphic variations of hum eral proxim al heads in
cham psosaurs (posterior view ). (Scales, 2 cm)
29
sm all individuals connect to the articular surface of the proxim al
head, form ing a bridge on the ventral surface (Figure 9).
The fem oral internal trochanter of the type specim en of C .
Iaram iensis (ANHM 982) connects to the articular surface of the
proxim al head like those of juvenile cham psosaurs, although the
internal torchanter is located m ore distally than those of juveniles
(Figure 13).
In contrast, separation of the internal trochanter from
the proxim al articular head occurs in the type specim en of C .
am bulator (AM NH983), and the periosteal bone covers the surface
betw een the internal trochanter and proxim al articular surface
(Figure 13).
The proxim al head of C. ambulator
(AM NH983) flattens
dorsoventrally m ore than that of C. Iaramieisis (AM NH982).
The
fem oral m orphology of the type specim en of C. gigas (SM M P72.2.1)
is sim ilar to that of C. laramiensis.
The internal trochanters of the
type specimens of C. natator (RTM .P81.47.1), C. albertensis (ROM 806),
and C. tenuis (SM M P79.14.1) also connect with the proxim al
articular surfaces, but their proxim al heads are oval in shape.
A lthough the separation of internal trochanter from the
proxim al head was considered a taxonom ic character unique to C .
am bulator, the sam e fem oral m orphology also occurs in
cham psosaurs from the Judith R iver Form ation of southern Alberta
and northw estern M ontana, the H ell Creek Form ation of eastern
M ontana, and the Tongue River Form ation of w estern N orth Dakota
(Figure 14).
Furtherm ore, a fem ur w ith internal trochanter
connecting to the oval-shaped proxim al head (MOR 697-G -30) and a
cham psosaur possessing C. ambulator-shape fem ora (M O R 697-G -13
30
Champsosaurus laramiensis
Champsosaurus ambulator
(AM NH982)
(A M N H 983)
Figure 13. Ventral view of femora of the type specim ens of
Champsosaurus laramiensis and Champsosaurus
am bulator with the diagram s of the proximal heads.
(Scale, 5 cm)
3I
(R T M .P 8 8 .1 16.3)
(R T M .P 8 0 .1 6 .1 4 2 1 )
Judith River Form ation in Dinosaur Provincial Park,
southeastern A lberta, C anada
(SM M P60.2004)
(SM M P80.11.4)
Tongue River and Sentinel Butte Form ations
in w estern N orth Dakota
Figure 14. D im orphic variations of femoral proxim al heads in
cham psosaurs (ventral view ). (Scales, 2 cm)
32
and -16) were found in the same bone bed in the T ullock Form ation
in northeastern M ontana.
The bone bed was in m udstone which is
considered floodplain in origin, and the skeletons of the animal
possessing C. ambulator-shape fem ora were associated.
This
taphonom ical situation suggests that the skeletons in this bone bed
are likely autochthonous.
Therefore, the. two cham psosaur
individuals possessing fem ora w ith different m orphologies lived in
the sam e area, and the burial of the two cham psosaurs took place
geologically at the same time.
The fem ur/hum erus length ratio varied about betw een 1.20
and 1.36 in all cham psosaur species.
N either notable interspecific
nor ontogenetic variations of the ratio are indicated in m easured
specim ens (A ppendix).
Although Brown (1905) and E rickson (1972)
noted lim bs of C. ambulator are shorter than those of C. laramiensis,
the fem ur/hum erus ratio is not different betw een them .
T he w idth/length ratio of hum erus varied betw een 0.33-0.50
in all cham psosaur species except C. laramiensis (Appendix).
In C .
laram iensis the ratio of an interm ediate-sized individuals is 0.30 and
that of large individuals is about 0.36-0.40.
observed in other species.
This character is not
The w idth/length ratio of fem ur varied
about betw een 0.18 and 0.24 in all species (Appendix).
B esides the hum erus and fem ur, Brown (1905) also described
m orphological variations of postcranial skeletons of the type
specim ens of C. laramiensis (AM NH982) and C. ambulator
(A M N H 983), especially the pectoral and pelvic girdles.
33
N o notable m orphological variations are observed in radius
betw een the type specim ens.
specim en of C. ambulator.
The ulna is not preserved in the type
The horizontal bar of the L-shaped
clavicle of the C. ambulator is stronger than that of the C. laramiensis.
The stem of the T-shaped intercravicles of the C. ambulator is more
robust and w ider than that of the C. laramiensis.
A lthough
m orphology of the scapula of the C. ambulator is not notably
different from that of the C. laramiensis, the infraglenoid process of
the coracoid of the C. ambulator is m ore pronounced than that of the
C. laramiensis.
There are only m inor m orphological variations of
tibia and fibula betw een these type specim ens, but the pelvic girdles
show distinctive m orphological variations (Figure 15).
The pubis of
the C. ambulator is anteroposteriorly w ider than that of the C .
laram iensis although the two individuals are alm ost equal in size.
The posterior part of ischium of the C. ambulator is m ore elongated
than that of the C. laramiensis.
C ham psosaurs possess three sacral vertebrae.
The first and
second centra w ere fused in the C. ambulator but not in the C .
laram iensis although they are alm ost equal in size and considered
adults (Figure 16).
The neural arches and sacral ribs were not fused
to the centra in both the specim ens.
34
Pubes
Champsosaurs laramiensis
Champsosaurs ambulator
(ANM H982)
(A M N H 983)
Isc h ia
Champsosaurs laramiensis
Champsosaurs ambulator
(ANM H982)
(A M N H 983)
Figure 15. M orphological variations of pelvic bones in
cham psosaurs (dorsal view). (Scales, I cm)
35
Champsosaurs laramiensis (AN M H982)
Champsosaurs ambulator (A M N H 983)
Figure 16. M orphological variations of sacral vertebrae in
cham psosaurs (ventral view). (Scales, I cm)
The arrow points the fusion of the first and second
c e n tra .
36
M icrostructures of C ham psosaur Hum eri and Fem ora
A ll the exam ined hum eri dem onstrate the sam e basic
m icrostructures at the deltopectoral crests.
The relatively thin
p erio steal cortices w ere progressively replaced with spongy bones in
the m edullar regions (Figure 17, 18).
The periosteal cortices of C .
am ibK /tftor-shape hum eri in both sizes appear thinner than those
w ith C. laramiensis-s]\2L\>z ones at the deltpectoral crests (Figure 17,
18).
T hick periosteal com pact bones, observable w ith the naked eye,
com m only occurred in fem oral diaphyses of sm all cham psosaurs.
The transverse section of a fem ur from a small individual
(U C M P142195) show ed that a hyperplasic periosteal cortex with
radial vascular canals was well developed (Figure 19).
The
longitudinal section of the proxim al half of the fem ur revealed a
p erio steal cortex gradually thinned tow ard the m etaphysis (Figure
19).
The radial vascular canals in the periosteal cortex appear to be
parallel to the boundary betw een the com pact and spongy bones.
N o significant m icrostructural variations occurred betw een C .
ambulator-shape (M O R697-G-13) and C. laramiensis-shzpe (M O R740)
fem ora in spite of their m orphological variations (Figure 20, 21).
both m orphological shapes of adult fem ora, the periosteal cortices
w ere vascularized and replaced by dense spongy bone in the
endosteal regions, form ing dense, am edullar bones.
In
37
(U C M P 1 4 2 2 0 0 )
:
v
r -rv,
18 # l
'
--V .;
(U C M P 1 4 2 2 0 6 )
Figure 17. Transverse sections of C. IaramiesisshdLyt hum eri in
interm ediate-sized (U C M P142200) and large
(U CM P142206) cham psosaurs. (Bones, posterior view;
transverse sections, proxim al view )
(Scales: bones, 2 cm; transverse sections, 5 mm)
38
(SM M P64.10.1)
Figure 18.
T ransverse sections of C. ambulator-shdspz hum eri in
interm ediate-sized (M O R -FU -82) and large
(SM M P64.10.1) cham psosaurs. (Bones, posterior view;
transverse sections, proxim al view )
(Scales: bones, 2 cm; transverse sections, 5 mm)
Figure 19. Juvenile cham psosaur fem ur (U CM P142195) with
longitudinal and transverse sections. (Bone, ventral
view; longitudinal section, anterior view; transverse
section, proxim al view) (Scales: bone and longitudinal
section, I cm; transverse section, I mm)
40
Figure 20.
C. laramisensis-shaipe fem ur (M O R740) with longitudinal
and transverse sections. (Bones, ventral view;
longitudinal sections, anterior view; transverse section,
proxim al view) (Scales: bone, 4 cm; longitudinal sections,
2 cm; transverse section, I mm)
41
Figure 21.
C. ambulator-shape fem ur (M O R697-G -13) with
longitudinal and transverse sections. (B ones, ventral
view; longitudinal sections, anterior view; transverse
section, proxim al view) (Scales: bone, 4 cm; longitudinal
sections, 2 cm; transverse section, I mm)
The transverse sections of both shapes of fem ora show that the
vascularizations w ere m ore concentrated in the anterior area than
the posterior area (Figure 20, 21).
In the endosteal regions, the
cortices w ere replaced w ith scattered H aversian system s.
The radial
vascular canals observed in the periosteal com pact bone in the
ju v en ile fem ur rarely developed in the exam ined fem ora.
The longitudinal sections of the proxim al and distal halves of
the exam ined fem ora show that the thick periosteal cortices were
gradually replaced w ith dense spongy bone tow ard both proxim al
and distal epiphyses (Figure 20, 21).
In contrast w ith the juvenile
fem ur, the p eriosteal cortices w ere scatteringly vascularized
throughout the shafts.
Calcified cartilage rem ained in the endoesteal
regions throughout the fem ora.
43
DISCUSSION
Ecological Cause for Sexual D im orphism in Cham psosaurs
A lthough the described m orphological variations of hum eri and
fem ora w ere considered taxonom ic variations betw een C. Iaramiensis
and C. ambulator (Brown, 1905), the histogram s of both hum eri and
fem ora from all three localities indicate that sim ilar dim orphic
variations also occurred in large individuals from the L ate Cretaceous
through Paleocene.
Therefore, the phylogenetic significance of the
described hum eral and fem oral m orphologies are questionable.
M aharana and Bustard (1982) and Bedi (1984) recorded the
ecological differences betw een sexes during the reproductive season
in gharials (Gavialis gangeticus).
Fem ale gharials excavate nests and
lay eggs distant from the river to avoid flooding.
A fterw ards, they
stay in the w ater near the nests.
They em erge from the w ater to
protect eggs and open the nests.
M ales protect the infants in the
w ater only during the post-hatching period although they keep
w atching the nests from the w ater prior to hatching.
Therefore,
fem ale gharials spend m ore tim e on land than males.
C onsiderable ecological and m orphological sim ilarities betw een
gharials and cham psosaurs suggest that the sim ilar ecological
division betw een sexes m ay have occurred in cham psosaurs.
Fem ale
44
cham psosaurs m ay have been m ore adapted to a terrestrial
environm ent than m ales due to the nesting behavior, resulting in
variations o f lim b m orphologies betw een sexes.
The observed
m orphological variations in cham psosaur hum eri and fem ora are,
hence, hypothesized to reflect sexual dim orphism .
As described above, Nm uscular attachm ents of C. ambulator-
shape hum eri are generally m ore pronounced than those of C.
Iaramiensis-Shwps hum eri (Figure 10, 11, 12).
The feature indicates
that the locom otive force of the C. ambulator-shape hum erus for
craw ling on land was m ore powerful than that of the C. Iaramiensisshape hum erus.
A rticular ends of the C. ambulator-shape hum eri are
m ore developed than those of the C. laramiensis-shape
(Figure 10, 11, 12).
hum erus
This bone m orphology suggests that the
m echanical support of the C. ambulator-shape hum erus was stronger
than that of the C. laramiensis-shape hum erus.
Therefore, C .
am bulator-shape hum eri m ost likely indicate a terrestrial adaptation
w hile C. laramiensis-shape hum eri suggest an aquatic adaptation.
Lim b bones of lizards are m orphologically sim ilar to those of
cham psosaurs except the existence of epiphyseal plates separating
epiphyses from diaphyses.
The fem oral internal trochanters of
m odern terrestrial lizards, such as Iguana and Varanus (D iapsida,
Squam ata), separate from the proxim al articular surfaces sim ilar to C .
am bulator-shape fem ora (Figure 22).
The same fem oral m orphology
also occurs in Sphenodon panpitecus (D iapsida, Sphenodonta), a
terrestrial reptile in New Zealand.
Gephyrosaurus bridensis
(D iapsida, E osuchia), an unspecialized terrestrial reptile from the
45
Varanus
C. ambulator-shape
Figure 22. Fem ur of Varanus (Squam ata, V aranidae) (Rom er,
1956) with com parison of C. ambulator-shape fem ur.
46
L ow er Jurassic of South W ales, England, also possesses fem ora with
separated internal trochanters (Evans 1981).
T hese extinct and
extant analogs suggest that C. ambulator-shape fem ora represent
fem ales w hich w ere m ore adapted to a terrestrial environm ent due
to the nesting behavior.
(Am blyrhynchus
The fem oral m orphology o f m arine iguana
cristatus) is also sim ilar to the terrestrial lizards
although they dive into sea to feed on m arine benthic algae.
The
lim b m orphology of this anim al m ay not have been adapted to an
aquatic life because it dives into the sea only for feeding but does not
stay in the w ater.
C orosaurus alcovensis (Sauropterygia, N othosauriform es), a
T riassic aquatic reptile, possesses fem ora w hose intern al trochanters
connect to the proxim al heads, sim ilar to C. laramiensis-shape fem ora
(Storrs, 1991) (Figure 23).
This extinct analog suggests that the C .
laram iensis-shape fem oral m orphology is an adaptation to an aquatic
life.
B ased on the described m orphologies of hum eri and fem ora
and extinct and extant analogs, it is hypothesized that cham psosaurs
with C. laramiensis-shwpe hum eri and fem ora, indicating aquatic
adaptations, are m ales and those w ith C. ambulator-shape hum eri
and fem ora, show ing terrestrial adaptations, are fem ales of each
species.
The m orphological sim ilarities of hum eri and fem ora
betw een ju v en iles and hypothesized adult m ales suggest m inor
ontogenetic changes of these m orphologies in m ales and an aquatic
niche for juveniles like adult m ales.
Interm ediate-sized individuals
47
Corosaurus alcovensis
C. laramiensis-shape
Figure 23. Femur of Corosaurus alcovensis (Sauropterygia,
N othosauriform es) (Storrs, 1991) with com parison of
C. laramiensis-sM 2L\)z fem ur.
48
w hich possess the interm ediate m orphologies of hum eri and fem ora
are, hence, likely im m ature fem ales.
Sander (1989) suggested that the same type of sexual
dim orphism occurred in Serpiansaurus mirigiolensis (N othosauria,
Pachypleurosauridae), a T riassic aquatic reptile (Figure 24).
The
assum ed terrestrial nesting behavior of fem ales o f the species
resu lted in b etter developed m uscular attachm ents and articular
ends on the hum eri com pared to m ales.
Rieppel (1989) also
described this type of sexual dim orphism in hum eri of
Neusticosaurus pusillus (N othosauria, P achypleurosauridae) (Figure
24).
These analogs support the hypothesis of sexual dim orphism in
ch am p so sau r
hum eri.
The separations of the ecto- and entotuberosities from the
hum eral articular surface by periosteal bones occurred in a large
individual (RTM .P94.44.6) found in the D inosaur Provincial Park,
Canada, although the hum erus dem onstrates C. laram iensis-like
m orphology.
Some other C. Iaramiensis-Shdjpz hum eri possess
periosteal bones w hich separate at least one tuberosity from the
proxim al articular surfaces.
These indicate that these separations
could occur ontogenetically in m ales but the degrees of the
separations w ere d ifferent betw een sexes.
A n interm ediate-sized cham psosaur (U C M P142209) from the
H ell Creek Form ation of northeastern M ontana possesses C.
am bulator-shnpz fem ora and C. Zartiimzensij1-Shape hum erus although
the hum eral ectotuberosity separates from the proxim al articular
surface by periosteal bone.
This suggests that the specim en is a
49
Serpiansaurus mirigiolensis
F e m a le
M ale
Neusticosaurus pusillus
Figure 24. Sexual dim orphic variations of humeri in
p ach y p leu ro sau rid s (D iapsida, S auropterygia)
(R ieppel, 1989 and Sander, 1989).
(Scales, I cm)
50
fem ale and im plies the m orphological change of the hum erus was
ontogenetically slow er than that of the fem ur in fem ales.
Because
this individual is considered sexually im m ature according to the size,
it is suggested that separation o f the fem oral internal trochanter
from the proxim al head took place before sexual m aturation.
The proxim al head shows a tendency to flatten dorsoventrally
during grow th in both shapes of fem ora.
Some large individuals
m aintained oval-shaped fem oral proxim al heads sim ilar to those in
juveniles.
The proxim al head of the right fem ur of C. gigas (SM M
P60.2004) is m ore flattened than that of the left fem ur; the internal
trochanters of both fem ora connect to their proxim al heads.
T herefore, flattening of the fem oral proxim al heads could occur
in d e p e n d e n tly .
C. laramiensis-sfowps fem ora appear to have occurred
occasionally w ith C. arafrw /tftor-shape hum eri and vice versa, even in
articulated cham psosaurs.
O ccurrence of a C. IaramiensisshwpQ
hum erus with a C. ambulatorshdipo, fem ur is considered to have
resulted from the different ontogenetic tim ing of m orphological
changes betw een hum erus and fem ur and possible retention of
juvenile m orphology of hum eri in fem ales.
Occurrence of a C.
ambulatorshapc hum erus with a C. laramiensisshzpe fem ur is
considered to have resulted from the m isidentification of the
m orphology of fem ur, caused by w eathering.
Sander (1989) suggested two criteria for determ ining sexual
dim orphism in a fossil taxon: num erous sam ples representing the
dim orphism from one stratigraphic horizon, and roughly equal
num bers o f dim orphs.
The described hum eral and fem oral dim orphs
in cham psosaurs occurred sym patrically in several form ations of
different geological ages.
As m entioned above, the described fem oral
dim orphs occurred in the same bone bed in the T ullock Form ation.
The num bers of C .
Therefore, the first criterion could be satisfied.
ambulator-shap& hum eri and fem ora are less than those of C .
laramiensis-shzLpe hum eri and fem ora in cham psosaurs from the
three localities (Figure 6, 7, 8).
Even though small individuals are
elim inated from this com parison because of the undifferntiated
m orphologies of these bones, the num bers of dim orphs are still not
e q u a l.
Four reasons are proposed to explain this discrepancy.
first is an unequal sex ratio.
that o f fem ales.
The
The num ber of m ales was greater than
The second is the taphonom ical bias betw een sexes.
B ecause m ales are hypothesized to be m ore aquatic than fem ales, the
chance of preservation in males could be higher.
The third is
m iscategorization of hum eri and fem ora in fem ales due to the
ontogenetic changes of these bone m orphologies. Interm ediate-sized
hum eri and fem ora in fem ales m ay be m iscategorized because of
their interm ediate m orphologies.
Possible retention of juvenile
m orphologies of hum eri in fem ales could produce m iscategorizations.
The last is m isidentification of the original m orphologies caused by
weathering.
E specially in C. ambulator-shape fem ora, periosteal
bones w hich separate the internal trochanters from the proxim al
heads w ere often peeled off by w eathering.
Therefore, they are
often m isidentified as C. laramiensis-shape fem ora.
52
The robust m orphologies of the pectoral and pelvic bones in C .
am bulator (AM NH983) indicate pow erful locom otion for craw ling on
land.
Therefore, C. ambulator, a fem ale, was m ore am bulatory than
C. laramiensis, a m ale, which is consistent with the interpretation
from the m orphological studies of hum eri and fem ora.
The larger
pubis and ischium of a hypothesized fem ale cham psosaur could have
related to the reproductive organs.
Sacral fusion did not occur in a cham psosaur with C.
laramiensis-sYiwpz lim b bones (M OR740) which is larger than the
type specim ens of C. ambulator (AM NH983) and C. laramiensis
(AM NH982).
In the MOR specimen, the sacral neural arches were
m issing and sacral ribs w ere detached.
This indicates that fusion of
sacral centra is not dependent on the size, suggesting that it does not
rep resen t an ontogenetic change.
Fusion of sacral vertebrae, w hich could provide m echanical
strength to support pelvic bones for w alking on land, is generally
observed in terrestrial vertebrates, for exam ple, dinosaurs.
Therefore, the fusion of the first and second sacral centra in C.
am bulator (AM NH983), a hypothesized fem ale, is considered to
reflect an adaptation to a terrestrial environm ent due to the nesting
behavior.
This is coincident with the interpretation from the
hum eral and fem oral m orphologies.
H ow ever, som e evidences exist which possibly opposes this
suggestion.
In the type specimens of Champsosaurus
natator
(R TM .P81.47.1), the second and third sacral centra were fused
although it possesses C. IaramiensisshwpQ hum eri and fem ora,
53
suggesting that this individual is m ale.
However, because the third
centrum was com pressed and the neural arch is also fused to the
second centrum , the fusion could be pathological.
In the specimen,
the second sacral ribs were glued upside down to the centrum by
plaster.
Furtherm ore, the first centrum does not m atch the anterior
surface o f the second centrum because it is sm aller than the second
even though the first centrum is the largest in three sacral centra in
all other cham psosaur specim ens.
This suggests that the sacral
vertebrae w ere m ounted inaccurately and the fused sacral vertebrae
m ay not represent the second and third vertebrae.
A cham psosaur (R O M 12 4 1) from the Paskapoo Form ation (Late
C retaceous) of A lberta, Canada, also possesses fused sacral centra
although it has C. laramiensis-shape hum erus and fem ur.
However,
because the bones w ere w eathered, the original m orphologies of the
hum erus and fem ur are not clear.
Furtherm ore, these bones may
represent surface collection and therefore, a m ixed assem blage.
The
second and third sacral centra were fused in a cham psosaur
(M O R697) w hich possesses C. ambulator-shape fem ora.
Fusion of sacral centra in cham psosaurs may be an individual
variation or pathological if it is not a sexual variation.
Further
studies for this m orphology are necessary.
Sym patric speciation is an alternative hypothesis for the
described dim orphic variations of hum eri and fem ora in
cham psosaurs.
extant anim als.
Sym patry of closely related species is observed in
M cCune (1996) described rapid speciation in
sem ionotid fishes from the Tawaco Form ation (Early Jurassic) of New
54
Jersey.
Therefore, C. Iaramiensis and C. ambulator may indeed
represent different species; C. Iaramiensis may be m ore derived
because it is considered more aquatic than C. ambulator.
The
dim orphic variations of hum eri and fem ora in cham psosaurs from
other form ations m ay also represent speciation.
The hypothesis of sym patric speciation, therefore, suggests
coexistence of cham psosaur species w ith terrestrial and aquatic
adaptations.
Furtherm ore, the two lineages persisted from the Late
Cretaceous to Late Paleocene, about for 22 m illion years.
However,
such lineages of speciation persisting for such a long tim e seems
unlikely.
Skulason and Sm ith (1995) suggested that resource
polym orphism s occurring in various vertebrates are im portant for
speciation.
The overall bone m orphologies of all cham psosaur species
indicate that they w ere essentially sem i-aquatic and piscivorous.
For
this reason, coexistence of terrestrial and aquatic form s can not be
explained by sym patric speciation resulting from niche
d iv ersification for resource partitioning and reducing interspecific
c o m p e titio n s .
The fem oral dim orphic variations which occur in
C ham psosaurus are also observed in Sim oedosaurus from Europe
(Sigogneau-R ussell, 1981).
Separation and connection of internal
trochanters from or to the fem oral proxim al heads occur in
sim oedosaurs, indicating the presence of both aquatic and terrestrial
m orphs in this genus.
It seems unlikely that the same m orphological
variations w hich occur in both genera represent speciation.
T herefore, it is hypothesized that the m orphological variations of
55
hum eri and fem ora observed in cham psosaurs reflect sexual
dim orphism rath e r than taxonom ic characteristics.
A ccording to the suggested hypotheses of sexual dim orphism ,
three cham psosaur species in N orth A m erica could be established: I)
C. natator in the Late Cretaceous, 2) C. Iaramiensis in the Late
C retaceous-E arly PaleOcene, and 3) C. gigas in the Late Paleocene.
Further studies are necessary for C. albertensis and C. tenuis b e c a u s e
the type specim ens represent the only identified m aterial.
56
M icrostructural V ariations o f C ham psosaur H um eri and Fem ora
B one m icrostructues provide clues about the ecology of an
anim al as m uch as bone m orphology.
Increase in body density is
necessary for aquatic anim als to overcom e buoyancy.
As a result,
m any aquatic anim als exhibit pachyostosis, an increase in thickness,
m assiveness, and density of bones as an adaptation to an aquatic life
(R icqles, 1976; B uffrenil and M azin, 1989).
Buffrenil and Mazin
(1989) described four dom inant types of pachyostosis; I) retention of
epiphyseal calcified cartilage, 2) hyperostosis of periosteal cortex, 3)
m oderation of inner resorption and rem odeling of bones, and 4)
intense rem odeling of bones by resorption and re-deposition of
bones in m arrow cavities.
W all (1983) stated that periosteal cortex thickening occurs in
H ippopotam us
(M am m alia, A rtiodactyla), resulting from the second
and/or third types of pachyostosis.
B uffrenil and M azin (1989)
described coincidental occurrence of the first three types of
pachyostosis in P achypleurosaurus and the sole occurrence of the
fourth type in Claudiosaurus germaini (Reptilia, Claudiosauridae).
W iffen et al. (1995) categorized increase of bone density into
tw o types: pachyostosis and pachyosteoclerosis.
W hen a bone
becom es dense due to hyperplasia of periosteal cortex only, it is
called pachyostosis.
The term , pahchysclerosis, is applied when the
57
com pactness of the inner structure of a bone is associated with
c o rtica l h y perplasia.
B uffrenil et al. (1990) described the ontogenetic changes of
diaphyseal m icrostructures of lim b bones in cham psosaurs.
The
diaphysis o f a juvenile cham psosaur is com posed of relatively thick
p erio steal cortex w hich is constructed of pseudo-lam ellar bone
tissues w ith less endosteal spongy bone.
Growth arrest lines and
radial vascular canals are observed in the periosteal com pact bone.
In later ontogenetic stages, probably follow ing sexual m aturity, the
cortical com pact bone was replaced with dense spongy bone, form ing
am edullar bone structures.
H yperplasia of periosteal cortex is not
observed, but unresorbed calcified cartilage was retained in adult
cham psosaurs.
C onsidering these bone m icrostructures, B uffrenil et
al. (1990) proposed that juvenile cham psosaurs w ere som ew hat
terrestrial and becam e m ore aquatic ontogenetically w ith
replacem ent of periosteal cortex w ith dense spongy bone.
As described above, the periosteal cortices of C. ambulatorshape hum eri in both sizes appear thinner than those w ith C .
laramiensis-sha^Q hum eri (Figure 17, 18).
The location of the
deltopectoral crest in C. ambu.lator-sha.ipe hum erus is m ore distal
than C. laremiensis-shape one (Figure 11).
Therefore, the periosteal
cortices at the points w here the transverse sections w ere m ade in the
C. ambulator-shape hum eri were expected to be thicker than in the C .
Iaram iensis-shape ones.
How ever, the opposite was observed.
T here may be two reasons that w ould explain these results.
The first is that the exam ined hum eri represent different ontogenetic
58
stages.
B ecause the periosteal cortex thinned ontogenetically, the
ontogenetic stages of the exam ined C. a m b u l a t o r hum eri m ay
have b e e n , later than those of the C. ZtiramzenjrZS1-Shape hum eri.
The
second is that the periosteal cortices in the C. ambulator-shape
hum eri are indeed thinner than in the C.
laramiensis-shape hum eri,
resulting from the ecological differences betw een sexes due to the
terrestrial nesting behavior in fem ales.
m ay indicate higher bone density.
T hicker periosteal cortices
Therefore, the thicker periosteal
cortices in C. laramiensis-shape hum eri m ay indicate that C .
laram iensis-shzpe hum eri were better adapted to an aquatic
environm ent than C. ambulator-shape hum eri.
This is consistent
w ith the interpretation from the m orphological studies of hum eri.
A
C. ambulator-shape hum erus (M OR969) from the Two M edicine
Form ation of northw estern M ontana, how ever, has a thick periosteal
cortex at the deltopectoral crest.
Further histological studies are
necessary to resolve this issue.
The exam ined fem ora dem onstrate the same m icrostructures
and ontogenetic changes w hich B uffrenil et al. (1990) described.
How ever, the periosteal cortices in both C. ambulator-shape and C .
laram iensis-shape fem ora are thicker than that in the specim en
described by B uffrenil et al. (1990).
This evidence indicates that
hyperplasia of periosteal cortex continued in the adult stage contrary
to the observations of Buffrenil et al. (1990).
The m icrostructural
differences in the transverse sections betw een this study and that of
B uffrenil et al. (1990) may result from the different positions w here
the thin sections w ere made.
59
As described above, no significant m icrostructural variations
occurred betw een the exam ined C. ambulator-shape and C .
laram iensis-shape fem ora.
This indicates that both hypothesized
sexes adapted to an aquatic life with increase of bone density by
retention o f calcified cartilage and secondary deposition of spongy
bone.
A lthough B uffrenil et al. (1990) suggested juvenile
cham psosaurs w ere som ew hat terrestrial, thick cortices in their lim b
bones indicate high bone density and therefore, an adaptation to an
aquatic environm ent.
This is consistent w ith the interpretation from
the m orphological studies of hum eri and fem ora.
In general, infants
of aquatic reptiles which lay eggs near shore m argins rush to the
w ater im m ediately after hatching or their parents carry them to the
w ater to avoid predators on land.
B ecause the skull m orphology of
the cham psosaur indicates that transportation of hatchlings by
parents is unlikely, infant cham psosaurs are presum ed to have
rushed to the w ater by them selves.
ju v e n ile
cham psosaurs
Therefore, it is unlikely that
w ere terrestrial.
W iffen et al. (1995) suggested that ontogenetic variations of
m icro structures in L ate Cretaceous plesiosaurids relate to the
ontogenetic changes of their ecology.
Pachyosteosclerosis observed
in ju v en ile plesiosaurids suggests that they were poorly m obile and,
therefore, lagoon or shore dw ellers like sirenians w hich also possess
the sam e bone m icrostructures.
On the other hand, osteoporosis-like
bone m icrostructures occurred in adult plesiosaurids, suggesting that
I
60
they had active locom otive behavior in the open seas like m odern
cetaceans in w hich the sam e m icrostructures occur.
As described above, the fem oral periosteal cortex in a juvenile
cham psosaur (U CM P142195) was less vascularized than in an adult.
This suggests that fem ora of juveniles w ere denser than those of
adults, indicating that juvenile cham psosaurs w ere less m obile.
In
contrast w ith juveniles, adult cham psosaurs may have been m ore
m obile so that they could catch fast-sw im m ing fish.
However,
secondary deposition of spongy bone could m ake fem ora dense in
adult cham psosaurs.
A com parison of gross bone density of fem ora
betw een ju v enile and adult cham psosaurs is necessary to address
this problem .
S u g g e stio n s
A lthough the degree of terrestrial adaptation is considered to
have varied betw een genera, all other choristoderes are thought to
have been am phibious like cham psosaurs (Evens and H echt, 1993,
Storrs and Gower, 1993).
Therefore, the sim ilar ecological variations
betw een sexes, hypothesized in cham psosaurs, m ay have also
occurred in them .
As m entioned above, the dim orphic variations
that occurred in cham psosaur fem ora are also observed in
Simoedosaurus (Sigogneau-R ussell, 1981).
Evans (1991) described
that the fem oral internal trochanter of an old individual of
61
Cteniogenys connects to the proxim al head, sim ilar to C. Iaramiensisshape fem ur.
Brinkm an and Dong (1993) described that the fem oral
internal trochanter of Ikechosaurus
sunailinae separates from the
proxim al head in the adult stage like C. ambulator-shape fem ur
although it is confluent with the proxim al head in the juvenile stage.
Storrs et al. (1996) described the ontogenetic separation of the
fem oral internal trochanter in Pachystropheus
rhaeticus.
Therefore,
it is necessary to exam ine fem oral m orphology of all choristoderes
w ith studies of other lim b bones and pectoral and pelvic girdles.
It is also im portant to study fusion of sacral vertebrae and its
relationship w ith lim b bone m orphologies in choristederes.
Evans
(1991) indicated that sacral fusion did not occur in an old individual
of C teniogenys w hose fem oral internal trochanter connects to the
proxim al head like C. Zammzen1S1ZS-Shape specim ens.
Studying lim b bone m orphologies of highly aquatic but
am phibious extinct and extant anim als, such as gharials, nothosaurids
and eosuchians, could also provide im portant inform ation because of
their inferred ecological sim ilarities to cham psosaurs.
M eers (1996)
described the m orphological variations of hum eri related to
ecological differences in crocodilians.
Therefore, sexual variations of
lim b bone m orphologies may occur in a crocodile species if ecological
variations occur betw een the sexes.
How ever, lim b m orphologies of
crocodilians under captured conditions differ from those in the wild
because o f nutrition and lim itation of their activities (M eers, personal
com m unication, 1996).
M any available skeletons of crocodilians
62
w ere from zoos, and therefore, this factor m ust be taken into
co nsideration in future studies.
The histological studies in this project indicate no significant
m icrostructural variations occurred betw een C. Iaramiensis- and C .
ambulator-sha.p& fem ora, and therefore, no m icrostructural
d istinction occurred betw een the hypothesized sexes.
Further
com parative studies of bone histology betw een the hypothesized
sexes as w ell as ontogenetic changes of m icrostructures w ith other
parts o f skeletons are necessary.
H istological studies of other
choristoderes and highly aquatic but am phibious extinct and extant
anim als are also im portant.
W ink and E lsey (1986) and W ink et al. (1987) observed that
fem ora o f egg-laying fem ale alligators {Alligator mississippiensis) are
less robust and m ore porous than both m ales and non egg-laying
fem ales, apparently resulting from egg shell production.
This is a
necessary consideration because sim ilar physiological changes may
have occurred in fem ale cham psosaurs.
63
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Vertebrata
APPENDIX
M easurem ents of C ham psosaur H um eri
W /L
R atio betw een w idth of the proxim al head and
length of hum erus
S ide
R
L
R ight
L e ft
(w )
S lig h tly
S pecim en
•v
w eathered
num ber
Locality num ber of a specim en of the M useum of
Paleontology at U niversity of C alifornia, Berkeley.
72
F o rm a tio n s
JR
BR
A ge
Late Cretaceous
L o c a lity
DPP D inosaur Provincial Park, A lberta, Canada
RDR Red D eer River, southw estern A lberta
Judith River ((O) Oldman) Form ation
B elly R iver Form ation
C. laramiensis-shape hum eri
Locality (Fm.)
Spec. Number
Side
DPP
DPP
DPP
DPP
DPP
DPP
AB
RTM.P95.134.3
RTM.P80.20.246
RTM.P95134.2
RTM.P71.21.1
RTM.P86.36.155
RTM.P81.29.3
SMM P68.20.2
SMM P67.4736
SMM 67.4.49
RTM.P64.5.219
RTM.P87.48.52
RTM.P80.16.51
RTM.P88.116.47
RTM.P92.36.564
RTM.P82.30.51
SMM P67.4
SMNH.P1956.8
NMC38460
RTM.P85.36.201
SMM P67.4.357
AMNH5354
R
R
L
R
L
L
R
R
R
R
L
L
L
L
R
R
L
L
L
R
R
L
L
L
L
R
R
R
R
DPP
DPP
DPP
DPP
DPP
DPP
(JR)
(O)
(JR)
(JR)
(O)
(O)
(O)
(O)
(JR)
(O)
(JR)
(JR)
(O)
SS
RDR
DPP
(JR)
RDR
(O)
(BR)
DPP
DPP
DPP
DPP
DPP
DPP
DPP
(JR)
(O)
(JR)
(JR)
(JR)
(JR)
(JR)
(JR)
RTM.P92.30.202
RTM.P90.107.82
RTM.P86.116.2
RTM.P90.119.31
RTM.P94.44.6
RTM.P85.67.21
RTM.P85.36.201
L
56.0
M
11.4
15.4
18.5
19.1
19.4
19.9
25.6
25.8
26.8
26.8
27.0
28.2
W/L
(w)
(w)
(w)
(w)
(w)
0.343
(w)
101.3 (w)
31.3 (w)
31.9
31.4
3 2 .9 (w )
95.9
124.3
35.2
35.0
36.4
36.7
37.6
37.1
37.7
38.9 (w)
40.1
41.3
44.1
44.5
0.367
0.332
73
C. a m b u la to r-sh a p e
hum eri
Locality (Fm.)
Spec. Number
Side
L
M
W/L
DPP
DPP
DPP
DPP
RTM.P81.19.261
RTM.P20.81
RTM.P95.132.2
RTM.P92.30.202
L
L
L
R
.........
........
.........
..........
29.7 (w)
35.1
36.3
36.4
........
-----........
-- - - -
(0 )
(0 )
(JR)
Form ation
JR
Judith R iver Form ation
A ge
L ate C retaceous
L o c a lity
nw M T
. N o rth w e stern
M ontana
C. Iaramiensis-Xype hum eri
Locality (Fm.)
Spec. Number
Side
L
M
W/L
nwMT
nwMT
nwMT
nwMT
V82142
V82114
V82092
YPM-PU22264
R
R
L
R
---------------..........
21.0
23.3
26.7 (w)
28.8 (w)
........
-----........
-- ---
(JR)
(JR)
(JR)
(JR)
F o rm a tio n
TM
A ge
L ate Cretaceous
L o c a lity
nw M T
Two M edicine Form ation
n o rth w e ste rn
M ontana
C. laramiensis-shstpc hum eri
Locality (Fm.)
Spec. Number
Side
L
M
W/L
nwMT(TM)
nwMT(TM)
YPM-PU22581
MOR424
R
R
-----------
35.8
40.1
-----------
W/L
C. ambulator-shwp& hum eri
Locality (Fm.)
Spec. Number
Side
L
M
nwMT (TM)
MOR969
L
------
37.0
Form ations
(A g es)
L
FE
T
FU
L o c a litie s
MT
neM T
seM T
Lance Form ation
H ell Creek Form ation
Tullock Formation
Fort U nion Group
(L ate C retaceous)
(L ate C retaceous)
(Early Paleocene)
(Early Paleocene ?)
M o n ta n a
n ortheastern M ontana
so u th e aste rn M ontana
C. laramiensis-shape hum eri
Locality (Fm.)
Spec. Number
neMT(?) (PU)
neMT (T)
V76176
V85085
(UCMP131796)
V70209
(UCMP119587)
V79103
(UCPM129419)
V86031
V87035
V83244
V87028
V90104
MOR-FU-082
V70209
(UCMP128576)
V84043
V70209
(UCMP119592)
V87028
V83086
V90001
MOR698
neMT (HC)
neMT (T)
neMT
neMT
neMT
neMT
neMT
neMT
neMT
(HC)
(HC)
(T)
(HC)
(T)
(T)
(HC)
neMT (HC)
(HG?)
neMT
neMT
neMT
neMT
(HC)
(HG)
(HC)
(T)
neMT
neMT
neMT
neMT
neMT
neMT
(T)
(HC)
(HC)
(HC)
(T)
(T)
V74119
V91018
V91018
V87040
V74110
V86094
(UCMP142200)
Side
L
M
W/L
R
R
L
R
---------------.........
16.0 (w)
16.9
17.2
18.4
-----.........
-----........
L
------
20.0 (w)
------
........
........
........
------........
-----------
20.1
21,4 (w)
22.7
22.8
23.9
24.0
24.0 (w)
-----........
---------.........
-----.........
25.1
26.0
-----------
26.2 (w)
26.3
26.3 (?)
26.4
25.0
26.8
27.1
27.2
27.8
27.9
28.3
........
---------0.359
0.353
----------........
----------........
R
L
L
L
R
R
L '
L
R
-----------
L
L
R
R
L
R
R
L
L
L
R
----------..........
73.5
70.9
----------........
----------........
C.
ZtiiramZen1Szs1-Shape hum eri (C o n tin u e d )
Locality (Fm.)
Spec. Number
Side
L
M
neMT (HG)
V91016
neMT (HG)
V91082
(UCMP142209)
V84224
MOR-TF-149
V92013 .
MOR740
SMM P69.14.1
MOR-FU-O82
V86094
R
L
L
------....
28.4 (w)
25.3 (w)
27.5
L
R
L
L
L
L
R
L
R
L
L
R
L
....
....
....
-----....
---....
....
------....
....
----
28.6
28.7 (?)
29.0
29.0 (w)
29.4
29.4 (w)
29.2
29.5
29.8
29.9
30.3
30.3
30.3
R
R
---83.5 (?)
30.6
30.9
L
R
....
----
30.9
31.0
L
L
L
R
R
---95.9
....
-------
31.3 (w)
31.5
32.0
32.3
32.4
R
R
L
R
L
L
------94.0 (?)
---....
104.0
32.7
32.8
31.9
33.1
33.4
33.7
R
R
R
L
L
---114.7
---....
....
33.9
34.2
33.4
34.3
36.7
neMT
neMT
neMT
neMT
MT
neMT
neMT
(T)
(T)
(?) (T?)
(T)
(T)
(T)
(T)
neMT
neMT
neMT
neMT
neMT
(HG)
(T?)
(T)
(T)
(T)
neMT (T)
neMT (HG)
neMT (T)
neMT (T)
neMT
neMT
neMT
neMT
neMT
(T)
(T)
(T?)
(HG)
(T)
neMT (T)
(HG)
neMT (T)
neMT (T?)
neMT (T)
neMT (T)
neMT (HG)
neMT (T)
neMT (T)
V91018
V79143
V84062
V74114
V84152
(UCMP130438)
V
V85086
(UCMP133904)
V84177
V84198
(UCMP142198)
V81014
V74124
V83043
V90092
V
(UCMP129403)
V84152
SMM P63.13.1
V86094
V83043
V730731
(U CMPl 07775)
V72130
V87082
V84198
V80006
(UCMP124439)
.
W/L
0.328
0.339
0.324
0.298
77
C.
laram iensis-s\ia.\)e. hum eri (C o n tin u e d )
Locality (Fm.)
Spec. Number
Side
L
neMT (FU)
USNM 427782
R
L
L
L
108.0
neMT (T)
neMT
MOR-FU-082
SMM P69.10.1
neMT (T)
V84199
(UCMP142187)
V83043
V77129
(UCMP142206)
AMNH982
neMT (T?)
neMT (T)
neM
(HG?)
neMT
neMT
neMT
neMT
neMT
neMT
neMT
MF
neMT
neMT
neMT
(T)
(T)
(HG)
(T)
(T)
(T)
(HG)
(T)
(HG)
(HG)
(T)
MT
(L)
neMT (T)
MT
(L)
V76170
V75196
V87087
V84177
V77124
V84156
V87029
SMM P63.14.1
MOR093
V85086
V84192
(UCMP130599)
USNM2453
V77129
(UCMP142205)
USNM2453
M
36.9
38.0
37.6
38.0
R
38.4
R
L
38.5
38.7
R
L
R
L
R
R
R
R
L
L
L
R
R
L
L
L
L
119.6
117.8
106.7
128.8
131.5
37.9
39.2
39.6
40.5
40.6
40.7
41.5
41.9
42.2 (w)
42.8
44.3
45.6
47.6
47.9
48.5
49.9
50.1 (w)
W/L
(^352
0.317
0.335
0.401
0.370
0.364
78
C. a m b u la to r-sh a p e
hum eri
Locality (Fm.)
Spec. Number
Side
L
M
W/L
neMT
neMT
neMT
neMT
neMT
V82009
MOR-FU-082
V87028
V85085
V84151
V87107
MOR-HC-180
V90096
(UCMP142190)
V84201
V84201
V91125
SMM P64.10.1
L
L
R
L
R
R
L
R
........
........
-----92.5 (?)
........
----------------
28.7
29.6
30.1
30.3
30.6 (w)
32.2
33.2
33.6
-----........
---------------........
-----------
33.9
34.4
36.6
35.7 (w)
36.7
36.9
37.4
----------.........
.........
----------------
(HC)
(T)
(HC)
(T?)
(HC)
(HC)
neMT (HC)
neMT (T)
neMT
neMT
neMT
neMT
(T)
(T)
(T)
(T)
neMT (HC)
neMT (HC)
neMT (T)
MOR-HC-180
V 84184
(UCMP142202)
V81005
(UCMP129294)
V77129
(UCMP142207)
V84080
(UCMP142203)
V84153
neMT
AMNH983
(HG)
neMT (T)
SMM P68.32.12
V84022
(UCMP142201)
neMT (T)
neMT (T)
neMT (T)
R
L
R
R
L
L
R
-----........
----------........
------..........
L
........
37.5
-----.-
L
------
37.8
------
R
------
38.0 (w)
------
R
L
R
L
L
R
L
-----........
-----112.7
----------........
38.5
36.8 (w)
39.9
39.5
40.7
41.1
40.8
--------------0.350
----------------
79
Form ations
(Ages)
TR
SB
FU
L o c a litie s
Tongue River Formation
(Late Paleocene)
Sentinel B utte (B ullion Creek?) Form ation
(L ate P aleocene)
Fort Union Group
(Late Paleocene?)
ND
nwND
swND
N orth D akota
northw estern N orth
southw estern north
D akota
D akota
C. laramiensis-shsipe hum eri
Locality (Fm.)
Spec. Number
swND (TR?)
ND
ND
(TR)
R
SMM P80.10.6
R
USNM20521
USNM (U.S.G.S. 64) R
L
R
SMM P74.12.1
L
R
SMM P90.4.1
L
R
YPM-PU17078
R
SMM P91.17.2
L
R
SMM P71.2.1
L
R
SMM P92.22.1
L
R
SMM P91.17.18
L
L
SMMP
R
SMM P77.33.24
L
L
SMM P60.2004
swND (TR)
swND (TR)
nwND (SB?)
swND (TR)
ND
(SB)
swND(?)(TR?)
swND (TR)
ND
(TR)
swND (TR?)
swND (PU)
Side
L
122.7 (?)
140.7
139.9
139.0
156.5
151.1
M
30.8
38.8
42.4
41.5
41.9 (w)
43.3
46.6
46.2
48.7
48.6
48.8
48.9
49.0
49.7
48.1 (w)
51.4
52.1
53.1
52.3
53.3
54.5
W/L
0.346
0.350
0.353
0.334
0.353
80
C.
a m b u la to r-sh a p e
hum eri
Locality (Fm.)
Spec. Number
Side
swND
swND
(TR)
(TR)
SMM P91.17.7
SMM P84.22.1
swND
(TR)
SMM P80.11.4
R
R
L
R
L
L
M
------
47.3 (w)
47.1
47.4
55.0
55.5
------
W/L
81
M easurem ents of C ham psosaur Fem ora
W /L
Ratio between w idth of the proxim al head and
length of hum erus
S ide
R
L
R ight
L e ft
(w )
S lig h tly w eathered
S p ecim en
num ber
v --------
Locality num ber of a specimen of the M useum of
Paleontology at U niversity of C alifornia, Berkeley.
82
Form ations
JR
BR
Judith R iver ((O )O ldm an) Form ation
B elly R iver Form ation
A ge
L ate Cretaceous
L o c a lity
DPP D inosaur Provincial Park, A lberta, Canada
RDR Red D eer River
C. laramiensis-shape fem ora
Locality (Fm.)
Spec. Number
DPP
DPP
DPP
L
RTM.P92.36.691
R
RTM.P84.163.75.
R
RTM.P81.16.100
L
RTM.P90.151.5
R
RTM.P80.16.1432
L
RTM.P82.19.220
R
RTM.P80.16.1356
L
SMM P67.4.440
RTM.P90.36.94
L
L
RTM.P80.16.1415
L
RTM.P80.20.95
R
SMM P67.4.260
R
RTM.P79.8.261
RTM.P85.36.207 . L
L
SMM P67.4.938
L
RTM.P87.36.138
L
RTM.P87.36.208
L
RTM.P87.36.135
L
RTM.P80.16.886
L
RTM.P67.20.199
L
RTM.P66.33.il
R
RTM.P82.40.1
L
RTM.P92.36.179
L
RTM.P81.23.122
R
RTM.P87.36.188
L
RTM.P85.63.40
R
RTM.P87.36.180
R
RTM.P78.9.123
RTM.P80.26.14
L
L
RTM.P92.30.202
RTM.P79.8.85.
R
AMNH5354
L
RTM.P88.116.3
DPP
DPP
DPP
DPP
DPP
DPP
DPP
DPP
DPP
DPP
DPP
DPP
DPP
DPP
DPP
DPP
DPP
DPP
DPP
DPP
DPP
DPP
DPP
DPP
DPP
DPP
DPP
seAB
DPP
(JR)
(O)
(JR)
(O)
(O)
(O)
(JR)
(O)
(O)
(JR) .
(JR)
(O)
(JR)
(JR)
(JR)
(JR)
(JR)
(JR)
(JR)
(JR)
(JR)
(JR)
(JR)
(JR)
(O)
(JR)
(JR)
(JR)
(JR)
Side
L
M
W/L
59.1
13.0 (w)
15.2
16.0
16.1
15.9 (w)
16.6
16.9
17.3
18.2 (w)
19.4
19.7 (w)
19.9
19.9 (w)
20.1 (w)
20.8 (w)
21.1 (w)
21.2 (w)
25.2 (w)
25.3 (w)
25.8
26.4 (w)
26.5 (w)
27.1 (w)
27.4
27.5
28.1 (w)
28.5
28.6 (w)
28.7
29.5
30.0
31.3
34.1
0.220
73.5
77.9
95.7 (?)
104.7
100.2
105.9
115.7
111.1
133.7
102.4
140.9
156.2
0.218
0.204
0.188
0.211
0.200
0.218
0.232
0.197
0.265
0.199
0.218
83
C.
la ra m ien sissh sL ip t fem ora (continued)
Locality (Fm.)
Spec. Number
Side
L
M
W/L
DPP
(BR)
(JR)
RTM.P80.16.1174
RTM.P81.47.1
L
R
L
DPP
(JR)
RTM.P80.16.549
145.5
..........
........
.........
34.3
30.3
34.5
37.0
0,236
----........
-----
C. am&M/titor-shape fem ora
Locality (Fm.)
Spec. Number
Side
L
M
W/L
DPP(JR)
RTM.P80.16:1421
L
------
29.2
........
84
Form ation
JR
A ge
L ate Cretaceous
L o c a lity
nw M T
Judith R iver Form ation
N o rth w e stern
M ontana
C. laramiensis-ty^& fem ora
Locality (Fm.)
nwMT
nwMT
nwMT
nwMT
nwMT
nwMT
nwMT
nwMT
nwMT
nwMT
(JR)
(JR)
(JR)
(JR)
(JR)
(JR)
(JR)
(JR)
(JR)
(JR)
Spec. Number
V82105
MOR-JR-OOl
V83025
MOR027(12)
V82174
V81234
V82229
V81236
MOR-JR-OOl
V82176
Side
L
L
R
R
L
L
L
R
R
L
L
M
W/L
12.5
15.9
18.3
18.5
18.9
19.9 (w)
21.2 (w)
23.0
23.1
26.5
C. ambulator-shape fem ora
Locality (Fm.)
Spec. Number
Side
nwMT (JR)
V83162
(UCMP142192)
L
L
M
W/L
30.1
------
85
Form ation
TM
A ge
L ate C retaceous
L o c a lity
nw M T
Two M edicine Form ation
n o rth w e ste rn
M ontana
C. laramiensis-shdi^Q fem ora
Locality (Fm.)
Spec. Number
nwMT (TM)
nwMT (TM)
MOR-TM-018
MOR-TM-013
Side
L
R
L
M
W/L
-------------
29.0
29.8
-----------
86
Form ations
(Ages)
L
HG
T
L o c a litie s
n eM T
seM T
L ance Form ation
Hell Creek Form ation
T ullock Form ation
(Late C retaceous)
(Late C retaceous)
(E arly Paleocene)
northeastern M ontana
so u th e aste rn M ontana
C. laramiensis-shsLp& fem ora
Locality (Fm.)
Spec. Number
Side
seMT (HC)
neMT (T)
neMT (HG?)
MOR-HC-109
V73096
V86031
(UCMP142194)
V90077
V72130
V90084
V85085
(UCMP131796)
V90077
V84203
V87098
V84156
V91133
(UCMP142195)
V91003
V87092
V86093
V86093
V87113
V90083
V87076(?)
V84152
V91018
MOR-FU-O82
V87065
MOR-FU-082
V87033
V90104
V84062
V77129
(UCMP142197)
V90001
V82028
V70209
L
L
R
neMT
neMT
neMT
neMT
(HG)
(T)
(HG)
(T)
neMT
neMT
neMT
neMT
neMT
(HG)
(T)
(HG)
(T)
(T)
neMT (HG)
neMT (HG)
neMT
neMT
neMT
neMT
neMT
neMT
neMT
neMT
neMT
neMT
neMT
neMT
neMT
(HG)
(HG)
(HG)
(HG)
(T)
(HG)
(T)
(HG) (T)
(HG)
(T)
(T)
(T)
neMT (HG)
neMT (T)
neMT (HG)
L
M
W/L
44.3
---------
7.9
10.3 (w)
11.1
0,178
........
L
R
L
R
-------------64.8
12.8 (w)
13.2
13.3
13.8
-----........
-----0.213
R
L
L
-------------
R
------
14.2
14.4 (w)
14.9
15.6
15.7
L
R
R
L
L
R
R
L
L
R
L
L
R
L
R
L
--------------------........
----------------------------------------........
-----104-8
16.9
17.0
17.0
17.2
17.7
18.4
18.4
18.6
19.0
19.1
19.2
19.2
19.4
19.4
19.8
19.8
R
R
R
----------------
20.5
20.5
20.8 (w)
.
-------
(w)
(w)
(w)
(w)
(w)
0.189
87
C.
Ztirtimzezz1S1Zj1-Shape fem ora (C ontinued)
Locality (Fm.)
Spec. Number
Side
neMT (HG)
neMT (T)
V87030
V83080
(UCMP10778?)
V88045
V88049
V84205
(UCMP142199)
V77129
(UCMP129570)
V87082
MOR698
L
R
L
L
L
R
neMT (T)
neMT (HC)
neMT (T)
neMT (T)
neMT (HG)
neMT (T)
.
neMT (T)
neMT (T)
neMT (T)
V86031
V85085
V79103
(UCMP129419)
V73080
V77128
V91002
neMT (HG)
neMT (T)
V90092
MOR-FU-149
neMT
neMT
neMT
neMT
neMT
neMT
neMT
SMM P62.10.1
V86094
V74114
V79102
V90095
V84022
V90095
(UCMP142191)
V90084
V90095
V87028
V88041
V87151
neMT (HG)
neMT (HC)
neMT (T)
(T)
(T)
(T)
(T)
(T)
(T)
(T)
neMT (HG)
neMT (T)
neMT (HG)
neMT (HG)
neMT (T)
neMT (T)
neMT (T)
neMT (T)
neMT (T)
V73080
V73031
(UCMP107775)
V74110
V80117
(UCMP129310)
V84198
L
95.5
105.1
R
R
L
L
L
R
L
L
R
L
R
L
R
L
W/L
21.2
21.4
21.6
21.8
21.9
22.0
0.226
0.209
22.0 (w)
R
R
L
R
L
L
L
R
R
L
R
R
L
L
L
R
L
L
R
R
M
95.5
96.3
t
108.0
104.9
116.2
122.4
20.2
20.8 (w)
20.8
22.1 (w)
22,4 (w)
22.6
22.8 (w)
22.9 (w)
23.1
23.1
23.2
23.2
23.2
23.3
23.7
23.7
23.8
24.1
24.3
24.6
24.6
24.7
24.7
24.7
25.0
19.9
25.4
25.5
24.6
25.7
25,9
26.2
26.4
0.218
0.216
0.216
0.235
(w)
0.213
(w)
(w)
0.201
(w)
88
C.
la ra m ie n s is-sh a p e fem ora (C ontinued)
Locality (Fm.)
Spec. Number
Side
neMT (T)
V77129
(UCMP129540)
V77129
(UCMP129570)
V85002
V84192
L
26.5
L
26.5
L
R
L
L
L
R
R
R
L
R
26.5 (w)
26.6
26.6 (w)
26.8
27.0
27.2
27.2 (w)
27.5
27.6
27.7
neMT (T)
neMT (T)
neMT (T)
neMT
neMT
neMT
neMT
neMT
neMT
neMT
(HC)
(HC)
(T)
(T)
(T)
(T)
(T)
neMT (T)
neMT (HC)
neMT
neMT
neMT
neMT
neMT
neMT
seMT
neMT
(HC)
neMT
neMT
neMT
neMT
neMT
neMT
(HC)
(T)
(T)
(T)
(T)
(T)
(HC)
(HC)
(HC)
(T)
(L)
(T)
seMT (L)
neMT (T)
neMT
neMT
neMT
neMT
neMT
neMT
(T)
(HG)
(T)
(HC)
(T)
(T)
V87151
V90092
AMNH27221
MOR-FU-O82
MOR-TF-149
V91007
V77129
(UCMP129570)
V80006
(UCMP124439)
AMNH982
V90092
SMM P69.10.1
V87056
V87151
SMM P69.16.2
V84201
USNM2453
V76170
(UCMP142188)
SMM P62 21.1
V84201
V74124
SMM P65.9.1
MOR-FU-082
MOR740
USNM 2453
V79103
(UCMP129419)
MOR697-G-30
SMM P69.16.1
V83244
V86031
V86094
MOR-TF-149
L
124.0
M
W/L
0.215
R
127.2
28.1
0.221
R
L
L
L
L
R
R
L
L
L
143.6
144.1
28.5
28.5
28.7
28,8
28.8 (w)
29.0
29.0 (w)
29.1
29.6
29.6
0.198
0.198
L
R
R
R
R
R
L
L
R
L
R
R
L
R
L
127.2
138.1
153.6
170.1
149.6
30.0
30.1
30.2 (w)
30.5
30.5 (w)
28.7 (w)
30.8
31.1
31.2
31.5
31.6
32.8
32.8
33.3
34,3
0.233
0.211
0.183
0.211
89
C. la ra m ie n sis-sh sip e fem ora (C ontinued)
Locality (Fm.)
Spec. Number
Side
L
M
W/L
neMT (T)
V84192
(UCMPl 30599)
V80117
(UCMPl 29324)
V84224
(UCMPl 3 1706)
R
L
L
162.1
-----------
34.3
33.9
34.4
0.212
.........
.........
R
L
-----169.9
34.7
33.2
-----0.195
Spec. Number
Side
L
M
W/L
V84220
V91082
(UCMP142209)
V84152
MOR-FU-O82
V84162
MOR (G1.93013)
SMM P64.10.1
R
R
L
L
L
R
R
R
L
L
R
-----........
-----........
........
---------------136.1
138.4 (?)
........
119.5
21.4
21.5
21.6
21.7
23.1 (w)
25.6
25.8 (w)
26.7 (w)
27.3 (w)
27.3
27.4
--------------------0.196
-----........
0.229
L
L
R
L
R
L
R
-----133.0
-----........
----------------
27.7
27.9
28.0
28.6
28.8
29.0
29.7
........
0.210
---------------........
........
neMT (T)
neMT (T)
C. ambulator-sha.p& fem ora
Locality (Fm.)
neMT (HC)
neMT
neMT
neMT
neMT
neMT
(T)
(T)
(HC)
(HC)
(T)
neMT (T)
neMT (T)
neMT
neMT
neMT
neMT
neMT
(T)
(HC)
(T)
(HC)
(T)
neMT (T)
neMT (T)
neMT (T)
neMT (T)
neMT (T)
neMT (T)
neMT (T?)
V84153
V84198
(UCMP142198)
V91125
V86093
V84198
V90084
V84153
V84199
(UCMPl 42187)
V84199
(UCMPl 30765)
MOR697-G-18
MOR697-G-13
AMNH983
V84177
V83018
(UCMPl 29212)
V77124
-------
L
R
L
R
L
R
R
R
.........
29.8
133.9
134.3
136.4
135.9
31.1
30.7
31.3
31.8
32.0
32.3
40.1 (w)
0.232
0.232
0.229
0.234
90
Form ations
Tongue River (Bullion Creek) Form ation
Sentinel B utte Form ation
A g es
L ate Paleocene
L o c a lity
ND
nwND
swND
North D akota
northw estern N orth
southw estern N orth
D akota
D akota
C. Iaramie ns is-shape fem ora
Locality (Fm.)
Spec. Number
swND (?)
SMM P80.10.6
swND (SB)
ND (TR)
swND (SB) .
swND (TR)
swND?(TR?)
nwND (TR)
swND (TR)
swND(?) (TR?)
swND (TR)
swND (FU)
Side
R
L
SMM P74.12.1
R
L
USNM (U.S.G.S. 64) R
L
SMM P71.2.1
R
L
SMM P90.4.1
R
L
SMM P92.22.1
R
L
SMM P82.8.1
R
L
SMM P77.33.24
R
L
SMM P91.17.2
R
L
SMM P91.17.18
L
SMM P60-2004
R
L
L
167.7
174.6
176.3
175.3
197 (?)
193
194
206
M
24.0
23.8
32.1
32.2
33.9
31.8
35.3
35.9
35.9
35.6
40.6
38.3
39.6
41.0
40.9
W/L
(w)
(w)
(w)
(w)
(w)
(w )
------....
0.192
------0.202
0.204
-----------0.226
---....
42.8 (?)
43.0
42.0
44.7
45.9
45.7
0.223
0.216
---0.223
----
W/L
C. ambulator-shape fem ora
Locality (Fm.)
swND (TR)
Spec. Number
Side
L
M
SMM P80.11.4
R
------
46.5
91
M easurem ents of C ham psosaur Lim b Bones
F /H
F /T
F em ur/H um erus length ratio
F em ur/T ibia length ratio
r
&
S ide
R ight
L e ft
9 2
C h a m p s o sa u r u s
n a ta to r (C. la r a m ie n s is -s h a p e )
NMC.8919
Side
R
Hum erus
Radius
Ulna
131
79
83.5
Femur
Tibia
Fibula
F/H
F/T
AMNH5354
L
R
----.......
-----
-----.........
------
-----.........
.........
141.0
99.0
92.5
98.0
65.4
------
-----.........
-----1.42
-----1.50
Champsosaurus albertensis (C. Ztimmzens1ZlS -Shape)
ROM806
R
Hum erus
Radius
Ulna
Femur
Tibia
Fibula
F/H
F/T
ROM3371
131.8
70.1
73.9
158.5 (?)
103.2
\104.8
1.20 (? )
1.54 (?)
L
---------------160.0
103.7
-----1 . 21 )
1.54
(
93
C. Ia ra m ie sn sis (C. /a ra w z e n m -sh a p e )
UCMP131796
R
SMM P65.3.1
L
Hum erus
Radius
Ulna
MOR698
R
L
77
47.2
47
73.5
45.2
46.1
70.9
Femur
Tibia
Fibula
64.8
.........
93.5
69.5
64.5
95.5
67.8
96.3
64.1 (?)
F/H
F/T
-------
-------
1.21
1.35
1.30
1.36
1.36
AMNH982
MOR740
SMMP 64.10.1
R
L
R
119.6 117.8
72.9 .......
----- 76.8
Hum erus
U lna
Radius
------
----- -
74.8
74.4
Fem ur
Tibia
Fibula
136.1 138.4 (?)
92.6 (?) ----........ 90.0
F/H
F/T
1.47 (? )---UCMP130599
R
L
L
143.6 144.1
------ 106.9
98.1
1.20
------
1.22
1.35
U C M P 1 3 1706
R
L
-------
-------
--------
169.9
126.3
-----
1.35
128.8 131.5
Humeru s
Ulna
Radius
84.9
Femur
Tibia
Fibula
162.1
114.4 113.5
106.2 (?)
F/H
F/T
1.26
1.42
(1.23)
(1.43)
R
—————
L
—————
73.6
—
—
153.6
110.9 112.0
—
—
—— ———
—— ———
1.39
I'
I
;
94
Champsosaurus ambulator (C. ambulator-shape)
R
L
R
L
Hum erus
Radius
Ulna
-----.........
------
-----.........
------
-----69.9
------
112.7
70.3
------
Femur
Tibia
Fibula
133.9
134.3
99.9
68.8 (?)
136.4
100.7
92.9
135.9
101.6
93.2
F/H
F/T
------
-----1.34
-----1.35
1.21
1.34
Champsosaurus tenuis (C. ZtimmzenlSzs1-Shape)
SMM P79.14.1
,
R
L
Hum erus
Radius
Ulna
-----—
------
-----69.4
70.5
Femur
Tibia
Fibula
162.5
113.3
110,6
162.9
113.8
------
F/H
F/T
........
1.43
........
1.43
95
C h a m p so sa u ru s g ig a s (C. la ra m ie n s is-sh a p e )
SMM P71.2.1
SMM P91.17.2
SMM P77.33.24
R
R
L
R
—————
—————
—
—
—
—
L
Hum erus
Radius
Ulna
139.9 139.0 (?)
----- 79.3
----- 81.8
Femur
Tibia
Fibula
174.6 176.3
....... 122.0
115.1 115.8
F/H
F/T
(1.25) 1.27
1.52 1.52
Hum erus
Radius
Ulna
Femur
Tibia
Fibula
F/H
F/T
----
—
194
193
135.2 133.9
—
—
—————
—————
1.43
1.45
SMM P90.4.2
SMM P60.2004
R
R
L
L
1 5 3 .0 -----93.9
94.1
----- 202
206
139.8 139.2
134.9
(1.32) ........
1.47
(1.48)
L
156.5 151.1 (?)
- - - - -
— — — — — —
89.2
89.2
197 (?)
135.8
134.2
1.30 (?)
(1.45) (?)
MONTANA STATE UNIVERSITY LIBRARIES
y I Zb2 1U314422 4