NEW METOPOSAURS FROM THE SOUTHWESTERN UNITED STATES AND THEIR PHYLOGENETIC RELATIONSHIPS

by Beth Davidow-Henry, B.S. A THESIS IN MUSEUM SCIENCE

Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of

MASTER OF ARTS Approved

U- Chairperson of the Committee

dL

L,4 Jr ' AccepteAr'r<»ntpdH

yO^^^^t^ll^ the Graduate School

December, 1987 /f(L

r^.

(*^QO. ^ ACKNOWLEDGEMENTS

Special thanks are due to Drs. Donald Baird (Princeton

University) , John Bolt (Field Museiam) , Joseph Gregory (University

of California, Berkeley), John Mecham (Texas Tech University), and

Michael Morales (Museum of Northern Arizona) for their many helpful

discussions and suggestions. I am especially indebted to Dr. Kent

Rylander (Texas Tech University) who patiently guided me through

the course of this thesis. And to Dr. Michael Willig of Texas Tech

University, a special thank-you for taking time at the last minute

to run the computer programs for me. Many thanks go to Dr. Sankar

Chatterjee, Chairperson of my committee and major professor, for

his support, interest, and assistance with this project.

I thank my husband, Greg, not only for his assistance with

the photography, but also for being there when it was important.

And, for their steady support and never-ending faith in me, I chank

my fa'mily, especially Mom and Dad.

11 TABLE OF CONTENTS

ACKNOWLEDGEMENTS ii

LIST OF FIGURES iv

LIST OF TABLES v

LIST OF PLATES vi

1. INTRODUCTION 1

2. MATERIALS AND METHODS 9

3. GEOLOGIC SETTING 11

4. DESCRIPTION OF NEW METOPOSAURS 16

Metoposaurs without otic notches 16

Metoposaurs with otic notches 30

5. RESULTS 34

Cartesian transformations 37

Biometric analyses 42

6. DISCUSSION 63

Growth studies and statistical analyses 63

Characters for taxonomic evaluation 63

7. CONCLUSIONS • • 70

REFERENCES 73

111 LIST OF FIGURES

1. Skeletal reconstruction of a metoposaur (after Romer, 1966) 3

2. Illustrations of the three genera of metopoaauroids showing the otic notch and tabular processes of: (A) Dictyocephalus; (B) Anaschisma; and (C) Metoposaurus 6

3. Dockum Formation in West Texas and type section of the Cooper Creek Member at the Post Quarry in Garza County, Texas (after Chatterjee, 1986) 13

4. Key to skull measurements and abbreviations 36

5. Cartesian transformation series of metopoaauroids: (A) TTUP 9216; (B) TMM 31099-12B; (C) TTUP 9083 (D) TMM 31100-124; (E) TMM 31100-42; (F) TTUP 9083 40

6. Biometric analyses: Top figure-logarithmic graph; (Figures 6A-6P) Bottom figure-ANOVA results 48

7. Two groups of metoposauroids 66

8. Cladogram showing the relationships of the genera of metoposaurs with the capitosaurs chosen for outgroup comparison 69

IV LIST OF TABLES

1. Table of skull measurements 38

2. Table of measurements as entered into the StatWorks computer program including natural logarithmic values for each variable 44 LIST OF PLATES

1. Dorsal view of TTUP 9216 18-

2. Ventral view of TTUP 9216 22

3. Dorsal view of TTUP 9237 26

4. Dorsal view of UCMP 82/39/37 29

5. AMNH 5661; Dictyocephalus elegans Leidy, 1856 32

6. New specimens in the genus Dictyocephalus (left to right) TTUP 9216; TTUP 9237; UCMP 82/39/37 72

VI CHAPTER 1

INTRODUCTION

Metoposaurs are characteristic Late Triassic labyrinthodont amphibians recorded from North America, Germany, Morroco, and

India. The family Metoposauridae, named from the Europena genus

Metoposaurus, is distinguished by its flat skull and the position of the orbits anterior to the midlength of the skull table. Bones of the skull roof are deeply sculptured on their dorsal surfaces.

Skeletons of the predominantly aquatic metoposaurs indicate an animal often 2 meters in length (see Fig. 1). Metoposaurs have been known from the Late Triassic Dockum sediments of West Texas since Case described a specimen in 1920 upon which he erected the genus Butteneria. Since then, five species have been named from the

Dockum, all belonging to this genus.

There is considerable disagreement among paleontologists concerning metoposaur taxonomy, including those specimens from the

Dockum. Colbert and Imbrie (1956) reviewed the Family Metoposauridae and concluded that the American specimens were sufficiently distinct from the Eurasian specimens to warrant placing the former into the genus Eupelor Cope, 1868, as distinct from the genus Metoposaurus

Lydekker, 1890, in which they placed all the Eurasian specimens.

Thus, Butteneria was reclassified as Eupelor according tu their vork. Figure 1. Skeletal reconstruction of a metoposaur (after Romer, 1966). ,-y} : b-

/"\ ^\-: •••-A

/•• / \ • \ . ^ / A\

;^ < ••..-^:T'- 5^'••:u./.rNi xV, J;\ More recently, Roy-Chowdhury (1965) doubted that the

differences between the Eurasian and American specimens were

great enough to justify placing them in two separate genera. He

proposed placing all species in the genus Metoposaurus, which takes

precedence over all other generic names. According to his taxonomy, which is followed in this study, all of the Dockum forms are

congeneric. Morover, Roy-Chowdhury merged all of the Dockum

Formation specimens into a single species, Metoposaurus fraasi.

Metoposaurus fraasi (see Fig. 2) is characterised by a robust

skull with deeply incised otic notches. Tabular processes, or

horns, are also present. The pineal foramen of M. fraasi is

situated on the rear third of the parietal elements. There is much

interspecific variation in this group and many features have been

altered by post-mortem crushing, two reasons why its members have

been assigned to so many species.

Two other genera of metoposaurs are recognised. The first

of these is represented by a solitary specimen, Dictyocephalus

elegans described by Joseph Leidy in 1856, which survives today as

a fragmentary specimen of a small metoposauroid. ^. elegans is

characterised not only by its small size but also by the absence of well-defined otic notches and tabular horns. An interesting

feature of Dictyocephalus is the location of the pineal foramen

centered, rather than near the rear, on the parietals. Colbert and Imbrie suggested that Dictyocephalus may represent a juvenile stage of a large metoposaur. Contrary to their suggestion. Dr.

Donald Baird (pers. comm.) believes that Dictyocephalus is a valid genus based upon the aforementioned characters. Figure 2. Illustrations of the three genera of metoposauroids showing the otic notches and tabular processes of: (A) Dictyocephalus; (B) Anaschisma; and (C) Metoposaurus. CJ Dr. Joseph Gregory revised the taxonomy of the metoposaurs on the basis of the presence or absence of the otic notch and

tabular horns. He concluded that for those specimens lacking

tabular horns and bearing a shallow otic notch the genus Anaschisma

Branson, 1905, was vaild. Anaschisma is founded upon two specimens which come from the Popo Agie Member of the Chugwater Formation of

Wyoming. These specimens have shallow otic notches and lack tabular horns. Dr. Baird (pers. comm.) suggests that Dictyocephalus may represent a juvenile individual of Anaschisma based upon these shared

characters as seen in figure 2. If that proves to be the case,

then Anaschisma would be the junior synonym of Dictyocephalus.

However, the systematic position of Anaschisma is questionable because of the incompleteness of the material. Two specimens, one

45 cm the other 41 cm in length,were recovered from near each other

from the Carnian-aged sediments of the Popo Agie. One other

specimen, currently undescribed, is known from the Redonda Formation

of northeastern New Mexico. That specimen is approximately 20 cm

in length.

In 1984, a skull of a small metoposauroid was discovered from

the Dockum Formation near Post, Texas. This skull, TTUP 9216, is

of particular interest in that it is the smallest individual known with a length of 6.8 cm. The skull features are also unusual when

compared with the other metoposauroids from the area.

The study of TTUP 9216, the specimen which forms the basis for

this thesis, is supplemented by two other new metoposauroid specimens:

UCMP 82/39/37 from Petrified Forest National Park, and TTUP 9237 from

Crosby County, Texas. 8

The purpose of this study is twofold: (a) to describe the morphology of the newly discovered skulls; and (b) to compare them

to skulls from other specimens in the three existing genera as a means of evaluating their taxonomic position within the Family

Metoposauridae. CHAPTER 2

MATERIALS A1>ID METHODS

The newly discovered skull, designated as TTUP 9216, was recovered from the Post Quarry, Garza County, Texas. Discovered by Michael W. Nickell during excavation, the small skull was encased in a matrix of red clay. To remove the skull from the matrix was a slow process requiring much care due to its delicate nature.

Acetone was used to soften the matrix in order to avoid moisture damage to the bones. Fine dental probes were used to pick away the damp matrix which was then gently brushed off. A calcareous crust covering the anterior portion of the skull near the external nares was removed with a weak solution of hydrochloric acid.

Specimen repositories are identified by the abbreviations preceding the specimen number: TMM, Texas Memorial Museum;

TTUP, The Museum, Texas Tech University; UCMP, University of

California Museum of Paleontology, Berkeley; YPM, Yale Peabody

Museum; AMNH, American Museum of Natural History.

Nine specimens were used in this study:

1. TTM 31100-42: well-preserved complete skull, portion of

premaxilla anterior of external nares missing; Howard

County, Texas; skull length = 455mm. 10

2. TMM 31100-124: well-preserved skull; Howard County,

Texas; skull length = 400mm.

3. TMM 31099-12B: excellent skull of juvenile metoposaur

complete with both stapes and lower mandibles; Howard

County, Texas; skull length = 160mm.

4. TTUP 9042: well-preserved skull; Howard County, Texas;

skull length = 380mm.

5. TTUP 9083: large complete skull, right side partially

distorted by crushing; Crosby County, Texas; skull

length = 630mm.

6. AMNH 5661: type specimen of Dictyocephalus elegans,

partially intact posterior region; Cumnock Formation,

North Carolina; skull length estimated at 78mm.

7. TTUP 9216: small skull and lower jaw; Garza County,

Texas; skull length = 73mm.

8. UCMP 82/39/37: small skull in good condition, Chinle

Formation, Petrified Forest National Park.

9. TTUP 9237: small skull, posterior border only; Crosby

County, Texas; skull length estimated at 110-120ram. CHAPTER 3

GEOLOGIC SETTING

The Late Triassic of West Texas was characterised by

alternating pluvial and arid conditions. A tropical to subtropical

climate with ample rainfall but a distinct dry season is indicated by the lithology. Paleomagnetic studies of the adjacent Chinle

Formation indicate a latitude of 16-18 degrees north of the equator, which seems to substantiate a tropical climate interpretation

(Tucker, 1982).

The Dockum Formation of West Texas is characterised by

continental red bed sequences composed of 70-700m of terriginous

elastics that accumulated in a mosaic of fluvial, lacustrine, and

flood-plain environments (McGowan, et al., 1979). None of the various beds can be traced extensively, a fact which is consistant with the fluvial interpretation of the Dockum. New research by

Dr. Tom Lehman and his students of Texas Tech University into the

sedimentology of the Dockum Formation shows little or no evidence

of lacustrine or deltaic deposits, contrary to McGowan's studies,

and indicates that nearly all of the Dockimi sediments are of a

fluvial origin (Lehman, pers. comm.)

Recently, Chatterjee (1986) has proposed a major revision of

the Dockum demoting it from Group to Formation status. He retains

11 Figure 3. Dockum Formation in West Texas and type section of the Cooper Creek Member at the Post Quarry in Garza County, Texas. 13

(b)

QUATERNARY conglomerate nl reworked Crciaceotis cobbles

TRIASSIC sandsione with worm burrows \ lime conglomerate

COOPER massive red mudstone

V fossiliferous layer in mudstone

massive mudstone piiorly defined fossiliferous layer in niiidstone

TRKJILU) cross-bedded, micaceous, finegrained s.nuisioiie

lime conglomeraie three units reducing them to member status. The lower

Tecovas Member consists mainly of siltstones and shales. The middle Trujillo Member is composed of sandstones and conglomerates.

The uppermost member, as seen in figure 3, has been designated as the Cooper Creek Member and may possibly of Middle to Late Nori.m in age (Chatterjee, 1986). It is from the Cooper Creek Member where the metoposaur skull central to this study was excavated.

Recently, the "upper fauna" assemblage has been discovered in the Dockum mudstones near Post, Garza County, Texas. From this quarry, new tetrapod fauna, including taxa so far unknown from the

North American Triassic, have been recovered. The fauna include parasuchids (=phytosaurs), coelurosaurs, pterosaurs, protorosaurs, squamates, poposaurs, fabrosaurs, and an ictidosaur. These forms indicate that the Dockum may not be restricted to the Carnian as believed, but may extend well into the Norian (Chatterjee, 1986).

It is generally believed that the Dockum fauna of West Texas is rather primitive, corresponding with the "lower fauna" of the

Chinle Formation. Past workers have correlated the Dockum with the Carnian of the standard European marine sequence. The "upper fauna" of the Chinle is thought to be absent from the Dockum, yet the ictidosaur, Pacygenelus, and the fabrosaur, Technosaurus,are closely related to South African forms of Late Triassic or Early

Jurassic age. Postosuchus, the new poposaur from the quarry, is clearly related to Teratosaurus, from the Upper Norian of Germany

(Chatterjee, 1986). 15

Aetosaurs have also been employed as correlative tools:

Long and Ballew (1985) stated that Desmatosuchus (described from the Post Quarry by Bryan Small) indicates a Carnian age for the

Dockum. According to those authors, the presence of Typothorax in the Upper Petrified Forest Member of the Chinle Formation defines a Norian age for that portion of the Triassic. Recently, Typothorax scutes and postcranial elements, as yet undescribed, were recovered from the Post Quarry, offering support to the idea that at least this section of the Dockum is perhaps of a Norian age.

Parasuchids are also useful correlative tools. Parasuchus and

Angistorhinus are restricted to the lower Dockum Formation. These genera are present in the Popo Agie Member of the Chugwater Formation of Wyoming and among the Maleri Formation of India, both of which are Carnian in age (Chatterjee, 1986). The genus Nicrosaurus which occurs in the Post Quarry, is restricted to the Stubensandstein

(Norian) of Germany, further adding support ro the Late Triassic age associated with the Post Quarry.

Metoposaurs are entirely restricted to the Late Triassic

(Carnian to Early Norian) continental deposits of North America,

Germany, Morroco, and India. Their uniform morphology on both sides of the Atlantic supports the concept of Pangaea during the Late

Triassic. But unlike the parasuchids, the metoposaurs are not useful for biostratigraphic subdivision. CHAPTER 4

DESCRIPTION OF NEW METOPOSAURS

Metoposaurs without otic notches

TTUP 9216: The most striking characters of specimen TTUP

9216 are its small size and delicate osteology, two features unusual amongst the Metoposauridae. Although this specimen is in relatively good condition, some portions of the skull are either missing or damaged. The skull is separated, horizontally between the orbits, into two sections.

The posterior section of the skull has sustained damage along the right lateral margin (see Plate 1). The squamosal has been broken from its tabular connection and the entire margin of the squamosal is absent. A small section of the jugal is evident upon close inspection, but the remainder of that element is missing.

The quadratojugal is also gone.

Anterior of the tabular, the supratempotal is intact, but the rear portion of the latter element has separated a fraction from its suture with the tabular. In front of the supratemporal the medial side of the postorbital is intact. The lateral margin of the postorbital is absent.

The postparietals are in excellent condition. The ornamentation is clearly visible on these bones, and the otic sinus.

16 :=> H H

5 CO to o Q

0) 18 19

albeit extremely shallow, is well-defined lateral to the

postparietal on the left side of the skull. Of great interest are

the parietals. The pineal foramen is located along the midline where the two parietal elements meet. On all other metoposaurs

examined, the pineal foramen was located on the rear third along

the parietal junction. On TTUP 9216, the pineal foramen is

centered on those elements. An interpretation of this feature

follows in the results section.

The postfrontal, with a small segment missing, is intact up to

the orbital rim. Of all the elements in the circumorbital series,

this bone is best preserved. The postorbital is only partially

intact for the lateral section of it is missing. The frontals are

difficult to distinguish; this is the area where most of the damage has occurred. However, the posterior section of the frontals where they merge with the parietals can be determined. Beyond that,

the frontals are obscured by damage.

There has been less damage along the left margin of the skull

(refer to Plate 1). The squamosal is intact, and the quadratojugal, with just its margin missing, rounds off the squamosal. The jugal

is partially present but crushing has obscured most of its features.

The jugal and maxilla, forming the outer margin of the skull, have been pushed upwards and medially, distorting the shape of the skull margin. Crushing has obliterated the left orbit, as well as specific features of the circumorbital series along the orbital rim. 20

The sculpturing of the dorsal elements holds true to that found on other metoposaurs. Pits are circular and uniform on elements where little growth has occurred. In the zone of growth anterior of the pineal foramen, these pits exhibit characteristic elongation. The lateral line system is indistinct in most places.

The ventral side of TTUP 9216 (see Plate 2) is severely altered by post-mortem crushing. The bones anterior of the broad palatine base are all absent. The right palatine is obscured by the interclavicle which has fused to it. The left quadrate is relatively intact and is connected to the squamosal and quadratojugal.

A small section, about 1.0cm in length, is all that remains of the parasphenoid. The maxilla, bearing approximately 10 tiny teeth, extends 2.0cm to where it has been broken. Medially, there is a row of 8 or 9 teeth; these may be on the ectopterygoid which is connected to the crushed dorsal palatine ramus. Ttro foramina pierce the area near the exoccipital/ parasphenoid contact.

The anterior segment of the broken skull contains the external nares. Calcareous deposits on this portion were removed with a weak solution of HCl which destroyed some ornamental and sutural detail. The nares and premaxillae are fairly intact, although a portion of the left premaxilla is missing. Post-mortem crushing has displaced part of the left side pulling it downward at an angle off the midline. The frontal region is beyond interpretation en 3 e to t-l

60 c •H 3 iH O c a^ PL. =3 H H

o

0)

to M

C >

(U to 22

j-> I - 23 due to the extent of distortion. Part of the right frontal is intact as is a section of the right maxilla. The left maxilla is partially intact with its contact with the prefrontal, but other features are obscured.

Ventrally, on the nasal segment of the skull, the right maxillary tooth row is partially intact. A few teeth are borne on the left maxillary. This 0.9cm long section bears about teeth. One vomarine tusk is apparent. The premaxilla is broken left of midline, and to the right, contains a couple of teeth.

One fang is well-preserved in the front. The internal nares are located close to midline; one remains unaltered by the crushing.

Portions of both lower jaws are preserved, with the right ramus being the better of the two (refer to Plate 2) . According to Jupp and Warren (1986), the Metoposauridae can be distinguished from other temnospondyls by the absence of coronoid dentition, and in the position of the posterior coronoid which forms part of the dorsal margin of the posterior Meckelian foramen. Only the anterior section of that Meckelian foramen is preserved in this specimen, and the sutures are difficult to discern. However, the foramen appears large, as is common in the Metoposauridae, and there are no teeth on the posterior coronoid element. These features indicate that the skull is a metoposaur and not a member of another family of the Temnospondyli. 24

Teeth are few but evident on the lower jaw. Two teeth towards the rear of the jaw clearly exhibit the labyrinthine infolding which characterises this subclass. All but two teeth on the dentary are broken off; these two teeth are very minute, but perhaps may easily have handled a diet of small fish or insects.

One clavicle is preserved and partially intact. The characteristic shape and ornamentation of the Metoposauridae are apparent. The interclavicle was damaged during preparation as it was fused to the ventral surface of the skull roof.

TTUP 9237: This specimen from Crosby County, Texas, is

represented by the posterior border of the skull as seen in plate

3. The 9.0cm wide border has both otic notches intact; these are only shallow embayments similar to those on TTUP 9216. Tabular

processes are entirely absent.

The postparietals are clearly defined as are both of the

tabulars. The right squamosal is more intact than the left and

is very narrow. The posterior border of the squamosals extend

wing-like slightly beyind the posterior margin of the skull. The

right supratemporal is nearly intact, but only a small portion of

the left one survives.

The posterior half of the parietals are intact, with the

anterior section missing. The pineal foramen is not on this rear

section; therefore, it must have been situated anterior of the

rear third of the parietal elements, as on TTUP 9216. CO tJN Pi S3 H H y-i O

0) •H >

to tn o o

CO

0) to

PM 26

= fe'^ 27

Ornamentation is typically metoposauroid on this specimen, which based upon its width, was probably lOcm in length.

Ventrally, little detail is preserved with the exception of the right quadrate. The occipital bones have been discrticulated from the skull, but remain intact as a unit. Both excoccipital condyles are well-preserved and developed.

UCMP 82/39/37: This specimen was recovered from the Upper

Petrified Forest Member of the Chinle Formation of Petrified

Forest National Park in northeastern Arizona at the Lacey Point site. It is a small metoposauroid, approximately 8cm in length, with shallow otic notches and lacking tabular horns (see Plate 4).

Iron deposits covered the entire surface of the specimen.

Removal of that iron with 10% HCl resulted in the marring of ornamentation and sutural detail. Post-mortem crushing has further destroyed many important features.

The right side of the skull is fairly well intact. The squamosal has been laterally compressed, distorting its width

considerably. The right orbit is well-preserved and the posterior portion of the external nares are also intact. The tip of the snout

is missing.

The left side of the skull had been pushed up beneath the right

side. Very little detail can be observed due to the extent of the

iron deposits. The area of the pineal foramen has been obliterated.

The left side is intact up to the orbital rim, a portion of which survives. CO tTv

CO

tu •H >

to CO o

0)

to r-t PM 29 30

Ventrally, a large portion of the left jaw ramus is preserved. The rear portion of the right ramus is intact but displaced medially. One clavicle is fused to the left side of the posterior region of the skull.

More sophisticated prearation techniques are required to remove the iron without destroying the bones. Until that time, further interpretation of the details is impossible.

AMNH 5661: Dictyocephalus elegans is not a specimen which is new to paleontology. Yet, its inclusion here is deemed justified in that D;. elegans represents the first known specimen of a metoposauroid without otic notches or tabular horns.

This specimen is in a fragmentary state today, but the details of the otic sinuses and tabular horns are well-preserved. Plate 5 illustrates this specimen and clearly shows the condition of those two features. Examination of the specimen indicated that tabular horns were never present, for the posterior margin of the tabulars are cleanly rounded off.

The ornamentation, arrangement of bones, and general characteristics of this specimen are exceptionally similar to the skulls described above.

Metoposaurs with otic notches

Metoposaurs with otic notches have been recently described in detail by several workers (Case, 1931: Romer, 1947), most recently by Roy-Chowdhury (1965) with his description of tX)

-a •H tu •J tn c to eel

OH 0) tj o >i u u •oH vO

(1) 4-1 ::! .—( 32

•^'" ••"'^^?^^?S'^!y-'^^^^^^p^^^^^^^

^.v^5*;s? 33

Metoposaurus maleriensis. These forms with otic notches and tabular horns have all been assigned to the genus Metoposaurus.

The members of Metoposaurus represent a group uniform in its morphology. They are fairly common in continental deposits of the Late Triassic and are of varying sizes. Six of the nine specimens incorporated into this study are members of that genus and range in size from 15 to 65cm in skull length. CHAPTER 5

RESULTS

In 1917, D'Arcy Wectworth Thompson applied the concept of geometric transformation to the description of morphological change. These changes in morphology were represented by the' distortion of a grid placed over an illustration of an organism.

Thompson used adult forms of similar organisms to show how one form could be derived from another, but an ontogenetic series can also be used to show how a single form alters with growth. The

Cartesian transformation offers a visual interpretation of the distribution of the growth of a body (Huxley, 1968) . It is for that reason which the Cartesian transformations were selected for this study.

To use the Cartesian transformation, a form is placed over an X-Y grid and then deformed along those recognised lines. A new figure is thus obtained, one which represents the original under a strain. These figures, when compared to each other, relate the sense and trend of transformation.

Six of the nine specimens were chosen for the transformation series, each as a representative of its size (i.e. growth stage).

First, as seen in figure 4, 17 characters were measured for each

34 Figure 4. .Key to skull measurements and abbreviations, 36

sw i -^ fei>, f^?M^i

si

si = skull length sw = skull width exw= exoccipital width exl= exoccipital length tbl= tabular process length tbw= tabular process width r = otic notch width s = otic notch depth ppl= pineal foramen to back of skull length pol= postorbital length iol= interorbital length aol= antorbital length in = intemares length nl.= nares length pe = pineal foramen to edge length me = midline (above orbit) to edge length se = snout (above nares) to edge length 37 specimen. Table 1 lists these measurements. Then, each skull was standardised to a unti legth of 10cm. Once on a unit scale, a square grid was placed over TTUP 9216, the smallest specimen in the series (see Fig. 5A). This grid was then drawn, based upon reference points on TTUP 9216, over each successive specimen as seen in figures 5B through 5F. In the course of redrawing the grid, the grid was deformed.

A second method for determining if the specimens actually represent a growth sequence was employed. By using programs designed for the Apple Macintosh computer, CricketGraph and Stat

Works, the use of the character measurements in plotting the allometric equation for growth was made possible.

Cartesian transformations

The Cartesian transformation series reflects certain trends as the specimens increase in relative size. Using TMM 31099-12B and TTUP 9083 as the smallest and largest definitive members, respectively, of Metoposaurus, these trends beome apparent.

The first trend is with regards to the position of the orbits,

The distance between lines 4 and 5X (with the X axis being along the exoccipital base) increases as the orbits migrate laterally axiay from the midline. Since orbital shape is greatly affected by post-mortem crushing, it cannot be stated that the reduction in orbital size between those two specimens is related to growth.

The forward position of the orbits on the skull roof is a highly diagnostic feature of the Metoposauridae. In the smaller 38

Table 1. Table of skull measurements.

TTUP AMNH UCMP TMM TTUP TMM TTuP sect 8Z/3«?/37 90^Z 'illOO'l-XM SUOO-tJ. 9083 si 73 *78 81 160 380 400 455 630 sw 65 60 70 120 320 340 420 510 exw 9 * A 32 A 75 110 120 exl 5 *6 *7 16 40 52 55 80 tbl 0 0 0 8 A A 35 40 tbw 0 0 0 15 A 35 35 40 r 8 11 8 14.5 *25 40 40 60 s 3.5 4 5 10 *20 *28 33 38 ppl 22 17 A 27 55 58 69 80 pol 37 39 45 80 190 195 220 340 iol *14 *24 *22 32 100 110 120 150 aol 22 * 22 50 105 115 125 150 in *6 A *8 16 34 38 48 90 nl 4 A 4 12 *30 *35 40 60 pe 25 31 32 55 153 160 200 220 me 20 29 22 42 105 110 140 165 se 12 A 12 29 60 75 90 130 Figure 5. Cartesian transformation series of metoposauroids: (A) TTUP 9216; (B) TMM 31099-12B; (C) TTUP 9083 (D) TMM 31100-124; (E) TMM 31100-42; (F) TTUP 9083. 40

5 A 3 2 ' "o 5 4 3 2 1 M" 1 '—1' i 1—— •t= i-- ); . L; / 1S / vJ KJ ( V / ', \ , / 5 I '^ / 0 , / / 0 ~xxr^ 7 / s

_0^ \2_ Vo_ 10 jy 110

5 4 3 2 1 ,—1 1 1 f--- ] - 1 \ t^l ^ /s / v V , / \ 6 \ y .0 in 7 8

9 ^ J>' 10

S 4 3 2 1 0 41

specimens, the orbits are placed further back on the skull,

relative to skull length, than the orbits on the larger skulls, which are closer to the snout. The orbital shift, seen in the

Cartesians transformation series between lines 3 through 6Y, with

the Y axis being along the skull length, is a result of the

expansion of the bones in the postorbital region and the repression

of growth in the preorbital region. Schmaulhausen (1968) notes

that age differences are manifested in orbital position.

Schmaulhausen cites the interpretation of orbital position as

concluded by Bystrov and Eframov in their study of Benthosuclms

sushkini, a capitosaur. Capitosaurs are also large Triassic

amphibians and the sister group to the metoposaurs. In the

young Benthosuchus, the orbits are located in the middle of Che

skull table. In the adult forms of that capitosaur, the orbits

have shifted to the posterior region of the skull (Schmaulhausen,

1968).

Associated with the increase in growth and the elongation of

the elements between the pineal foramen and the orbits, is the

relative compression in those areas anterior and posterior of that growth zone. This trend can be seen in the compression between

lines 1-3Y and lines 7-9Y.

A second feature appears between lines 3-5X near the snout.

Although this factor may be altered by crushing, it appears chat the the snout becomes wider as the animal increases in size. A third, and quite interesting feature is seen in the position of the pineal foramen between TMM 31099-12B and TTUP 9083. In the smaller 42 skull, the foramen lies further anterior (relative to skull length) on the skull table than it does on the larger skull.

This trend is apparent in the shortening of the distance between lines 1-3X on the Cartesian transformation series. The pineal foramen of TTUP 9216 lies even more anteriorly than on TMM 31099-

12B. Although AldNH 5661 was not used in this series, the same pineal foramen position present on that specimen is present on

TTUP 9216.

Again, data from Benthosuchus permits interpretation. In juvenile forms of the capitosaur, the pineal foramen lies on the anterior end of the parietals. In the adult forms, the pineal foramen has shifted to a point midway between the parietal elements.

Schmaulhausen (1968) points out that this shift of the pineal foramen is age dependant like the shift of the orbits.

The shift of the pineal foramen during growth has been suggested as being due to the development of the olfactory organ, the olfactory lobe, and the cerebral hemispheres of the brain. As the midbrain is reduced in relative size and pushed backward, the pineal organ, being in a fixed position on the midbrain, is carried along during this posterior movement. Thus, it is only the shift of the midbrain and the pineal organ associated with it that determines the posterior shift of the pineal foramen

(Schmaulhausen, 1968).

With the exception of TTUP 9216, the tabular processes do not change relative to increase in size. Specimens TMM 310099-

12B through TTUP 9083 all possess well-developed tabular horns, 43 the size of which are altered in a few of the specimens by crushing. Along with that feature, the depth of the otic notch relative to size also remains fairly constant. Even though TTUP

9216 does not appear to have a notch, when drawn to scale, a small one does appear.

Biometric analyses

Relative growth denotes change of proportions as an organism increases in size. Huxley's 1932 conceptual tool in the bivariate study of form was the equation of simple allometry: Y=Bx^.

Dodson (1975) states that the size of any part of an organism

(Y) is expressed as an exponential function of the size of the whole organism over a range of size. The value of the allometric coefficient (a) reveals whether a given part is increasing at a greater rate (positive allometry), a lesser rate (negative allometry), or at the same rate (isometric allometry).

In this study the natural logarithmic form of the allometric equation was used: lnY=lnB + alnx. When the data were converted to natural logs, curvilinear relations became linear and the line-fitting technique of simple regression was used.

Biometric considerations, as stated by Dodson (1975), dictated the choice of x. Here, x is the length of the skull.

One criterion upon which that decision was based is that the skull length represents the measurement with the greatest range in size.

In table 2, all 17 variables measured for this study and their natural logs are listed. Each graph plots two variables, one being the dependant x variable of skull length, the other being the 44

Table 2. Table of measurements as entered into the StatWorks computer program including the natural logarithmic values for each variable.

»vl 1 73 65 q 5 : -' 2 7" 60 6 11 4Ci T ?l 70 7 3 5 3 5M 4 160 i:o 32 16 S 15 14 5 10 r.i 5 "SO 520 40 25 10 0 6 400 340 75 5^' 35 40 :'; 0 7 455 4ro 110 55 J5 35 4i"i 33 0 S 630 510 120 60 40 40 ^0 :; 0

ppl pol w>1 aol

1 22 57 14 22 6 4 25 ;o 2 17 35 14 31 5 45 -,^ ^'^ 3 4 72 4 27 so 71 50 16 12 55 5 55 l?0 100 105 34 TO 153 6 ^3 155 110 115 33 75 tiO 7 69 220 110 125 48 40 100 3 cO 340 150 150 ?0 60 110 165

LN SL LH SW IH EW LN EM IN Tfl L.'l TPW in P

1 12 4 2?0 4 174 2.197 1 ';09 ;07F' 4 357 4 094 1.7?2 1 ;"•? 7 12 4 5:i4 4 143 1 946 1 099 1 609 1 '"'^^ 4 29 5 075 4 7S7 3 466 2 773 2 079 2 703 1 '.'^ 5 60 5 940 1763 3 6.99 '. :.!? 6 75 5 991 5 325 4 JI7 3 551 3 T55 T -::? 7 ?0 6 120 6 010 4 700 4 007 3 555 3 555 ? 639 3 669 4 n-<4 O 130 6.446 6.234 4 787 4.382 Zii'i

LN FFl LH POL LH IOL LH WL

1 153 3 091 3611 2639 J 091 1 792 1 386 ;119 I 336 1 333 3 664 3.173 3 -134 1 6OT 3 807 3 091 3 091 2 079 1 336 T J66 2 303 3 296 4 3*''* 3.466 3 911 2 773 2 435 4:o: 2 996 4 007 5 247 4 605 4 654 3 516 5 401 5 ""O 3.331 4 060 S173 4 700 4 745 3 633 .? -,-'*^ 5 :"' 3 407 4 134 5 3?4 4 797 4 319 3 371 3 639 5;:-? 3.63S 4 332 5.829 5 011 5.011 4 500 4 094 5 7-4

au IE LN SE

2 ??6 2 4B5 :• io. : 0''1 :4?5 : 73o 3 367 4->54 4 n',J4 4 700 4 317 4 ?42 4 f'.'O 5 106 4 ' i.'i 45

independant variable of another skull measurement. The blank spaces in the data set indicate either a value of zero, for which there is no log) or a variable which was missing on that

specimen.

The problem of incomplete data sets is a common one in the

study of fossils. In order to deal with the missing data, the

computer program employed pairwise deletion. In calculating a

bivariate statistic where a datum field is blank for one specimen,

the field for the other variable is ignored. In that manner, the

particular specimen does not contribute to the calculation of that

coefficient (Dodson, 1975).

As an example, the first figure in the series (figure 6A) shows the logarithmic plot of skull width as a function of skull

length. The analysis of variance (ANOVA) chart indicates that the sw:sl ratio is very significant, as shown in the far right column. The coefficient of determination (R) reveals that a full

99.4% of the variation in skull width can be attributed to the variation in skull length.

The range of variability in the 16 ANOVA tests show that

95.3% to 99.7% of the variability in any given measurement is due to the variation in the length of the skull. These graphs and charts are listed in figure 6A through 6P and can be interpreted following the example given above.

In doing these analyses of variance, the null hypothesis made was that the specimens do indeed represent an ontogenetic series.

Based upon that hypothesis, the results of the logarithmic plots 46 and the ANOVA's show that size differences (i.e. age differences) may account for the most parsimonious explanation for the linear progression, or isometric allometry, shown in each graph. Figures 6A-6P. Biometric analyses: Top Figure—logarithmic graph; Bottom Figure— ANOVA results. 48

6A

5w 0.782 » sl*1.012 R = 1.00

.,;')(.;

> ••-./••, J

Jg"

•31

:?ijrri .vf D?-3

1 :,."..,rl n '•r>.

CT.jl

"vrrYici^flt '-•!' L r'"'rrT.'l'nii'iOri v? -'Z'"z'-'i C'-^tTvi"?'''.* '-F!'"2)

HI ,1 ^,..: 1- . I f ', 49

6B

oxw =0.057 • 3f* 1.211 R - 0.90

..--3

• ,111

-51

;?ijm of D"?!]. ot M>?.in :0ijrC6' ioujrS'S Ff'ij^dorn S'^uif6'3 F-Rjtio ?!--;'o:F

-T . •_-,;,^ 0.105

Vt.il 4.£i9

'Ic6'ff:ci6'nt of Det^rrninaticn !.R"2) 0. ?T3 .^di-jsrvd Cc^"'rc7rrit i.^R''2) 0.'?~0 i".,-iMT'tioic,r.T ijt' rof*'>?i6t'ior! I.Rj 0 . '?^-'i itirntif:-: Error oi Ejtimdt'? 0. ) 87 50

6C

6x1=0.026 ' 31*1.249 R= 1.00

Sum of Dijip. of Mii.iri :v'jr'2& ?qij.ji"'?s Fr*'?don"i Square; F-P.itio probM^

Mcc:^! 1 1 r. 1.45'? 0. C4S O.OuS

"Ot.il

i.-C'efiioit-nt of D'jt'f'r.niirijtiori (.R"l'; 0. 353 .^di'jjtjd C,:^f''!:''>rit (R''2) 0.'?'?4 ^^".•ijftioivnt of '" "•'•f'^Utiori i R i 0 '?'?7 iihrmirc Error or Ei^T'riViTi- j. 'jiS l'jrb'],'i-\! iiso'i E'inxtio 2. 'r25 51

6D

tb5 - 0.010 » Gl'1.306 9. = 0.09

.:;•.) :i.;u si

Sum of C'sq. of H

; lodfl T . .J I • Error 0.047 0.02;

Tot.il 4.622

Cotfncifnt of D6'tt'riT,irijiiori (r'"2) 0 9'rri ^di'j?''T'd ''J•:rf'''v.':'^Ti* (R''2) 2 Co>?ff'ic.i6nt of CoiV'jicit'iori (Ri C' •5C=; ': tindjrd trror of Estimate 0 I-urbin-V-it^cfi S'jtistio 2 52

6E

low = 0.069 •' ;iri .017 R - C.Qfl

sl

"urn of Deq. of Me.sn • S'jUirvj Fr^j^dom F-=:iti,:

0.139 3 0.04':'

"ntii

C'ifno'

;,it>"':,-.-ir,T •-•(• Corriijfion i.P.'' 0 "in^ziri: Error or E/tTnit^ 0 jlt^ jrb\fi~ •/i^.SC'U r'Td'ii'iO _ 53

6F

r =• 0.207 * s|-0.857 R =0.90

:-iijm OT ,<^i} . ot Mi?.5in •••r6":vrn F-Ritio Frob>F

14^'--. 1 1 -_'

•••or 0.034

..06rT"o:iri'-t 0? .--T^rTi'i'rifinon

r;-„itYi,:iK,nT of Corr^'i+'ion iR it-inoirc Error of Ei"f!m.iT.6, 54

6G

s = 0,036 * xsl* 1.093 R = 0.99

.J J -•'•••< si

Sum of Deo. of \-\^hx\ :,ourc:? Bqu-ares Fr'j'jdom Squari-i F-Patio '-'•-ob:-|^ • :0d6'l Error 0.104 0.017 rot-ii

jrffioi'f-rit Oi [T'rrmiri-at'ori i.R^.'

•,c,Ty'r'wriT vt Corr^ls+'on i.P.i '5"0.3ri3 Error of E/tTnit'? .roin-tv-jrvon i*.aU/tio 55

6H

ppl - 0.961 » 31*0.685 R -- 0.93

• t J ,. J J

oum OT D^q. of I'ls-in ;qU.=rH5 Fro'idorn >qu-3r'?:3 •it^o Prob:F

I ' •• '-'=A 1 -r.L . . •_,'4 Error U _ M ;

, OT-il .;. .-^u

-••,•'••••I*i:^ Co?T'''ic"i&ri*. lR"2? 1:6'ffioi'?riT of Cor'-6Ution (R) QC;T i'.'iTvViVii t-rror o'\ Ei'irriaii? 124 - :.,''t;r.~'.,''.ii^;"or! bt.jtiitiv 56

61

pol = 0.5^13 * 51*0.988 R = 1.00

Sum of Di?q. of rte-in Sourc? Squar*;. Fri?edom •-,-,K::.r

Error 0.016 0. on?:

.06'fTioivh. or L-^rj^rrrr'nrKTi'.': \4;,j,ii4 ,':-s-v?-.>t.|-|4 !p"2'l L,:-6'ffioi6'rit of Corr^htion (R) 0.999 St.ind-ard Error of E.-r;,Ti.iit^ 0.051 rL;rDin-,v.at5ori S'-atiitiO 57

6J

iol= 0.219 » r.1*1.024 R = 0.98

SI

Sum of Ol?'}. of Mo =10 -v'jrov Square-;. rri?«dom Squaro-3 F-Rj+io P-obiF

i.-'.i'i r4.C4C 0.000 '•ror 0.1S3 0.031 lOt.ai 6.1U.i

•-•.i"?ifioierit or [.Htjrrriirijiiofi u -cvjjtfd C',6'fr''i'-i6ri*' F'"2) ''o'rrf'vi&nt of Corr-jldt'on iR.J '::i,-i.xaro Error oT Ei-timjie '.•ijro iri-'v/.i r/On S ''if ivt:o 58

6K

aol = 0.381 » 51*0.9-13 R = 1.00

..'.'U ;vJ -l'.''v si

Sum of Dijq. of Miin i-ouro-; :cuari?'3 Freedom Squarijj i^-Patio P>-OD:-F •lod*] «•. Joe 4. CUc Error 0.031 0.00^

'Ot.-al 4.097

CofffioisTit of DHtermin.alion (i u. r r^: .-^diustf'd Co?ffioii?ri't iP "2'.J 0 991 Cowffii-.-jiirit of OorrsU+ion i'^') ij 99>:, •jTariGard ."^rror of Eit^maTi? 0.075 ''•jrbin-'v.it^on Stiti/ti,; 59

6L

•3e-0.101 " 51*1.102 R - 1.00 -0 -!

11

XJ

5l

Sum of Oeg. of M^-sn Squar^i Fr^jedom Squar^-^ F-Patio

^.^.J.l c cere: A C trertr Error 0.042 5 O.OOS

rotal 5. -597 6

Coeffioient of Dt-terrriinatlon (.R''2) 0. 992 .^di^jsted Coi='**''':'irri'!'. ',R'2) 0.991 C'o^ffioi^nt of Correlation ' P) 0.99':, irafidard Error of E^timaTs 0.092 :'jrbm-Vatjon itatix^io 2.797 60

6M

in = 0.05? » "J*1.12 R=0.99

.-•='

L-J'J Sl

Sum of Di?i5. of Mi?ari :.ourc>- I"!Uar« Freedom Square-i- --^'.'Ay.< Prob>F irror 0.117 0.023

J. 'j_,_,

loc^'fio'enr of ''eterminaTiori i R 2..' o. 9,30 ^liuir^d Coeff^oii-nr (F:''2) 0.974 i"'OHff'ii-i>?rit. of Cor*''?^at'ion '•^'!• j . 990 :," afidard Error of EsTimate ij. 15-3 ! .r::n- /a'ii-or; r'ari/t^o ! .-14 61

6N

n!= 0.016 * 31*1.276 R = 1.00

Sum of Deg. of Heari So'jrc? Square-:. Freedom Squarei" "-Pat'O !=''-!-,K-ir

f-^-^fc- 0. CHh, iotai

-•oeTfioient of Determinatiofi (R"2} -^dVJ'tfd Cvrff'ioij'-'t ''p-'-2"'i !'OHtfi,--jc,nT of l>rreht-^ori (p)

jtanoarij Error of EvTTrare LM:,,'J

^•'J..ij;-c,:n, L'ill - • • • 62

60

pe = 0.334 ^ s^^ .025 R = 1.00

JU H

1 GO :.JU

Sum of Deq. of rlean iource S.zuare; Freedom Squire-.- "Ratio F'rob>F • lodel i'"ror 0 rS-: 0.00'^

'otal

Ooeffioiefii of'-etermiriatiori'?'' 0.991 -idiusted Cojfroii'rit ';p''2) 0. 9;'9 Coeffioierit of Correlation i.P'i 0.995 : ?ar;oard E;"ror of Ef-timate 0.095 CHAPTER 6

DISCUSSION

Growth studies and statistical analyses

The Cartesian transformation series provided a visual account

of the changes that might occur during the ontogeny of a metoposauroid. However, to be accurate in reflecting ontogenetic

change, a true ontogenetic sequence must be employed. Since the

specimens used in this study were found in different localities and stratigraphic sections they cannot be said to represent such a series.

The significance of the statistical results indicates that the Metoposauridae is a uniform group. Differences that could be used to define genera were not picked up by the analyses.

Two of the characters which appeared to change as the skull length inreased were the position of the pineal foramen and the position of the orbits. These features, supported by information from Benthosuchus sushkini, are growth related and therefore not of taxonomic significance.

Characters for taxonomic evaluation

With the exclusion of the above mentioned characters as taxonomically significant, two characters remain for valid

63 64 assessment of relationships. These are the presence/ absence of the tabular processes (horns) and the notchless/ notched structure of the otic sinus (see figure 7).

The metoposaurs can be separated on the basis of the otic structure as demonstrated by Gregory (1980). He concluded that two genera should be recognised for which the names Anaschisma, for those forms with the notchless condition, and Metoposaurus, for those forms with the notched condition, are valid.

Most populations of metoposaurs have well-defined otic notches and are thus readily separable from those which show only a shallow otic sinus are the rear of the skull. Systematic recognition of those two groups is comparable to the recognition of several genera of the Capitosauridae based upon different types of modifications of the otic notch in that family (Welles and

Cosgriff, 1965; Gregory, 1980).

The capitosaurs are separated into two basic groups:

Paratosaurus, from the Lower and Middle Triassic, represents the central stock of the Capitosauridae, a form with open otic notches.

Cyclotosaurus, from the Upper Triassic, represents the end product of capitosaur evolution; this form possessed fully enclosed otic notches.

The tabular process of Paratosaurus ends in a prominant point, whilst that of Cyclotosaurus grows to meet the squamosal, fully encapsulating the notch and forming an otic fenestra.

Welles and Cosgriff (1965) described a new species of

capitosaur from the Meteor Crater area of Arizona. Ten specimens Figure 7. Two groups of metoposauroids. 66

1. Shallow otic notch 2. Tabular processes absent

1. Deep otic notch 2. Tabular processes present 67 of Paratosaurus peabodyi were recovered from that quarry, each of varying size with the otic region well-preserved. This ontogenetic series showed that the structure of the otic notch remains constant and does not vary with ontogeny. The degree of closure did not change even though the notch depth increaced.

Following these evolutionary changes seen through time in the capitosauroid otic notch, the same character can be used to evaluate the taxonomy of the metoposauroids. In the capitosaurs, the shallow otic notch is primitive. An enclosed notch is indicative of the derived capitosaur condition. The metoposaurs exhibit a shallow otic notch in the primitive state. A deeply incised notch indicates a derived form.

These characters are summarized in the cladogram in figure

8 which shows the relationships of the genera of metoposaurs using the capitosaurs as the outgroup for comparison. Apomorphies are listed for each node of the cladogram. Figure 8. Cladogram showing the relationships of the genera of metoposaurs with the capitosaurs chosen for outgroup comparison. 69

(2) Dictyocephalus (3) Metoposaurus

(1) Metoposauridae

Capitosauridae

Apomorphies for each node are as follows:

(1) orbits anterior of midlength of skull; skull table relatively flat.

(2) tabular processes absent; otic notch shallow.

(3) tabular processes present; otic notch incised.

Degree of separation is not implied. CHAPTER 7

CONCLUSIONS

Only two genera of metoposaurs coexisted in the Late

Triassic, Dictyocephalus and Metoposaurus. Dictyocephalus has been found throughout the Late Triassic deposits, as has

Metoposaurus, with no stratigraphic significance assigned to either of their occurrence.

In conclusion, the discoveries and subsequent analyses of

TTUP 9216, TTUP 9237, and UCMP 82/39/37, support the position that these specimens should be placed together in the same genus, namely Dictyocephalus (see Plate 6).

Therefore, Dictyocephalus Leidy, 1856 becomes the senior synonym of Anaschisma Branson, 1905.

70 r^ CO

Ol en CNJ 00 § o •• K3 M D iH • M ra r^ j= n p. CM 0) CTi a o PH :3 4>J< H O H •H « CO v.O^ a —4 C csl (u as 00 PL, m 3 J= H 4J £H c •H ^-v 4J CO .sz C 60 QJ -H S >-i •H o o (U u a. CO u y-i 3

vO

OJ XJ nj iH P^ 72 REFERENCES

Baird, D. 1986. Some Upper Triassic reptiles, footprints, and an amphibian from New Jersey. in_ The Mososaur 3:126-153.

Branson, E.B. 1905. Structure and relationships of American Labyrinthodontia. Journal of Geology 13(7):568-610.

and Mehl, M.G. 1929. Triassic amphibians from the Rocky Mountain region. University of Michigan Studies 4C2):1-255.

Case, E.G. 1931. Description of a new species of Butteneria with a discussion of the braincase. Museum of Paleontology, University of Michigan Contributions 3:187-206.

. 1932. A collection of Stegcephalians from Scurry County, Texas. University of Michigan Contributions, Museum of Paleontology 4(l):l-56.

Chatterjee, S. 1986. The Late Triassic Dockum vertebrates: their stratigraphic and paleobiologic significance; pp. 139-150 ±ri Padian, K. (ed.). The Beginning of the Age of Dinosaurs. Cambridge University Press.

Colbert, E.G. and Imbrie, J. 1956. Triassic metoposaurid amphibians, amphibians. Bulletin of the American Museum of Natural History 110(6):403-452.

Dodson, P. 1975. Functional end ecological significance of relati relative growth in Alligator. Journal of Zoology, London 175:135-355. Elder, R.L. 1978. Paleontology and paleoecology of the Dockum Group, Upper Triassic, Howard County, Texas, unpublished M.S. Thesis, Department of Geology, University of Texas at Austin.

Green, E. 1954. The Triassic deposits of Northwestern Texas. unpublished Ph.D. dissertation. Department of Geology, Texas Tech University.

73 Gregory, J.T. 1980. The otic notch of metoposaurid labyrinthodonts; pp. 125-136. j^ Jacobs, L. (ed.). Aspects of Vertebrate History.

Huxley, Sir Julian S. 1972. Problems of Relative Growth (second edition). Dover Publications, Inc., New York.

Jupp, R. and Warren, A.A. 1986. The mandible of the Triassic temnospondyl amphibians. Alcheringa 10:99-124.

Murray, P.A. 1982. Biostratigraphy and paleoecology of the Dockum Group (Triassic) of Texas. Ph.D. dissertation. Southern Methodist University.

Olson, E.G. 1985. A larval specimen of trematopsid (Amphibia: Temnospondyli). Journal of Paleontology 59(5):2273-2280.

and Miller, R. 1951. Relative growth in paleontological studies. Journal of Paleontology 25(2):212-223.

Romer, A.S. 1947. Veview of the Labyrinthodontia. Bulletin of the Museum of Comparative Zoology, Harvard University 99:1-367.

. 1966. Vertebrate Paleontology (Third edition). University of Chicago Press. Chicago, Illinois.

. 1968. Notes and comments on vertebrate paleontology. University of Chicago Press. Chicago, Illinois.

Roy-Chowdhury, T. 1965. A new metoposaurid amphibian from the Upper Triassic Maleri Formation of Central India. Geological Studies Unit, Indian Statistical Institute, Calcutta. 4.

Schmaulhausen, I.I. 1968. The origin of the terrestrial vertebrates. Academic Press. New York and London.

Small, B.J. 1986. The Triassic thecodontain reptile Desmatosuchus: osteology and relationships, unpublished M.A. Thesis, Department of Museum Science, Texas Tech University.

Tucker, M.E. and Benton, M.J. 1982. Triassic environments, climates, and reptile evolution. Paleogeography, Paleoclimatology, Paleoecology. 40:361-379.

Watson, D.M.S. 1919. The structure, evolution, and origin of the Amphibia-the orders Rhachitorai and Stereospondyli. Philosophical Transactions of the Royal Society of London (B) 209:1-73. 75

Watson, D.M.S. 1962. The evolution of the labyrinthodonts. Philosophical Transactions of the Royal Society of London (B) 245:219-265.

Welles, S.P. and Cosgriff, J.W. 1965. A revision of the labyrinthodont family Capitosauridae and a description of Paratosaurus peabodyi n. sp. from the Wupatki Member of the Moenkopi Formation of Northern Arizona. University of California Publications in Geological Sciences 54:1-148.

Wilson, J.A. 1941. An interpretation of the skull of Butteneria with special reference to the cartilages and soft parts. Contributions from the Museum of Paleontology, University of Michigan 6:71-111.

. 1948. A small amphibian from the Triassic of Howard County, Texas. Journal of Paleontology 22(3):259-361, PERMISSION TO COPY

In presenting this thesis in partial fulfillment of the

requirements for a master's degree at Texas Tech University, I agree

that the Library and my major department shall make it freely avail­

able for research purposes. Permission to copy this thesis for

scholarly purposes may be granted by the Director of the Library or my major professor. It is understood that any copying or publication of this thesis for financial gain shall not be allowed without my further written permission and that any user loay be liable for copy­ right infringement.

Disagree (Permission not granted) Agree (Permission granted)

Student's signature Student's signature //

/O ihfn^hfu /Qr/ Date Date