Elasmobranch and Osteichthyan Fauna of the Rattlesnake Mountain Sandstone, Aguja Formation (Upper Cretaceous; Campanian), West Texas.

by

Joseph A. Schubert, B.A., B.S.

A Thesis

In

Geoscience

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

Master of Sciences

Approved

Thomas M. Lehman Chair of Committee

James E. Barrick

Sankar Chatterjee

Dominick Casadonte Interim Dean of the Graduate School

May, 2013

Copyright 2013, Joseph A. Schubert

Texas Tech University, Joseph A. Schubert, May 2013

ACKNOWLEDGEMENTS

Thank you to Dr. Tom Lehman for his knowledge and help throughout the project, Steve and Jen Wick of the Ten Bits Ranch without whose fossil microsite, none of this would be possible, Dr. Mark Grimson and the Texas Tech Imaging Center for use of the Hitachi SEM, and Alton and Linda Schubert for their unwavering support.

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TABLE OF CONTENTS Acknowledgements ii

Abstract vi

List of Figures viii

1. Introduction 1

Geologic Setting and Regional Stratigraphy 2

Stratigraphy of the Ten Bits Microsite 4

Methods 5

Tooth Morphology and Nomenclature 6

Rostral Teeth 8

Placoid Scales and Dermal Denticles 9

2. Systematic Paleontology 15

Hybodontidae 15

Lonchidiidae 16

Ginglymostomatidae 18

Orectolobidae 23

Squatinidae 24

Cretoxythinidae 26

Anacoracidae 27

Mitsukurinidae 31

Rhinobatidae 33

Hypsobatidae 35

Sclerorhynchidae 36

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Ptychotrigonidae 42

Rhombodontidae 47

Myliobatidae 49

Trigonodontidae 55

Albulidae 55

Phyllodontidae 56

Semionotidae 58

Osteichthyes 58

Testudines 63

Mosasauridae 64

Crocodylia 65

Reptilia 65

Coprolites 66

3. Discussion 77

The Ten Bits Fauna 77

Ten Bits and Terlingua Microsites Compared 79

Paleobiogeography of the Western Interior Seaway 80

Comparison with the Judith River Fauna 82

Comparison with the Pictured Cliffs Fauna 83

Comparison with Blufftown Fauna 84

Comparison with the Black Creek Fauna 85

Characteristics of the Gulf Coast and Atlantic Fauna 86

4. Conclusions 93

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References 97

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ABSTRACT A thin granular conglomerate within the Rattlesnake Mountain sandstone member of the Upper Cretaceous Aguja Formation on Ten Bits Ranch in Brewster County, Texas preserves a diverse assemblage of small teeth, denticles, vertebrae, and other bones of chondrichthyan and osteichthyan fishes. This thin layer of teeth and bones probably represents a winnowed lag deposit, concentrated by wave action in a coastal marine environment. The deposit, referred to herein as the "Ten Bits Microsite" is highly fossiliferous; screen-washing methods yielded about 5000 specimens. Chondrichthyan fishes are represented by 23 species,while identifiable osteichthyan fishes represent four species. Two of the three most abundantly occurring chondrichthyan species

(Scapanorhynchus texanus and Ischyrhiza mira) are also the most common species in other middle to Late Campanian marine vertebrate faunas along the Gulf of Mexico, and

Atlantic Coastal Plain. Ptychotrygon agujaenisis is abundant at Ten Bits, but unknown in correlative marine faunas elsewhere. The abundance and diversity of ptychotrigonid rays may be a unique feature of the Ten Bits fauna.

The most common osteichthyan fishes found in the Ten Bits fauna (Paralbula casei and Albula sp.) are also reported elsewhere in Gulf and Atlantic Coastal Plain faunas, but they are rare there and subordinate to bony fishes not recovered at Ten Bits.

Paralbula casei is a common bony fish found in marine vertebrate faunas of the Western

Interior. The most common chondrichthyan fishes found in Western Interior faunas are either unknown or rare in the Ten Bits fauna, and the common Western Interior ray

vi Texas Tech University, Joseph A. Schubert, May 2013

Myledaphus bipartitis does not occur at Ten Bits or any other Gulf or Atlantic Coast fauna. These differences probably reflect latitudinal variation, oceanic water circulation pattern, or variation in other environmental conditions between the Western Interior

Seaway and the Gulf or Atlantic Coast that restricted the distributions of some marine fish species. The similarities between the Ten Bits fauna and those of the Atlantic and

Gulf Coast indicate that western Texas was more closely allied biogeographically with that province than with the Western Interior of North America.

One species tentatively identified in the Ten Bits fauna on the basis of a single tooth, Igdabatus indicus, is otherwise known only from Africa and Asia. If this identification is correct, it would represent the only known occurrence of the species in

North America. This could reflect the chance preservation of a single individual outside of its normal range. Western Texas may have been near the northern limits of the range for tropical marine vertebrate species.

vii Texas Tech University, Joseph A. Schubert, May 2013

LIST OF FIGURES

1. General geologic map of the Big Bend region of Texas. 11

2. Stratigraphic Relation of the Aguja and Pen Formations. 12

3. Stratigraphic section of the Aguja Formation. 13

4. Diagram of sawfish, tooth and denticle terminology. 14

5. Selachiian teeth. 68

6. Selachiian and Batoid teeth. 70

7. Batoid teeth . 72

8. Osteichthyan teeth. 74

9. Indeterminate rostral spines and Reptilia. 76

10. Late Cretaceous paleogeographic map of North America. 88

11. Paleogeographic map of North America during Campanian. 89

12. Paleogeographic reconstruction of the Western Interior during

Campanian time. 90

13. Ten Bits Ranch Chondrichthyans Assemblage. 91

14. Ten Bits Ranch Osteichthyans Assemblage. 92

viii Texas Tech University, Joseph A. Schubert, May 2013

CHAPTER 1

INTRODUCTION

Remains of fossil sharks and bony fishes are relatively common in Upper

Cretaceous marine strata throughout western North America. Although similar remains have been reported from the Upper Cretaceous Aguja Formation in the Big Bend region of West Texas, only a few specimens from the upper part of the formation have been illustrated (e.g., Rowe et al., 1992), and no thorough account of the Aguja shark and bony fish material has been presented. The Aguja fauna is of particular interest because it provides a sample from the southernmost Late Cretaceous biome in the Western Interior

Seaway of North America (Lehman, 1997). Contemporaneous shark and fish assemblages are known from sites farther north on the Great Plains, and also farther east on the Atlantic and Gulf Coastal Plains. The Aguja fauna offers an opportunity to compare the marine vertebrate faunas in these separate biogeographic provinces. The primary goal of the present report is to provide systematic descriptions and illustrations of a diverse shark and bony fish assemblage recently recovered from the middle part of the Aguja Formation (Rattlesnake Mountain sandstone member).

The shark and fish assemblage described in this report was collected at a site on the Ten Bits Ranch, about 15 km north of Study Butte in Brewster County, Texas (Fig.

1). The site is referred to here as the "Ten Bits Microsite" and was discovered by the owner of ranch, Mr. Steve Wick, who made the initial collection from the site and granted permission to undertake the present study. Subsequent study revealed that this

1 Texas Tech University, Joseph A. Schubert, May 2013 site is almost certainly the same one mentioned by McNulty and Slaughter (1972) that yielded the type specimens of the batoid chondrichthyan Ptychotrygon agujaensis.

Specimens collected for the present study are catalogued at the Vertebrate Paleontology

Laboratory of the Texas Memorial Museum in Austin, Texas and assigned to site TMM -

46018. Exact locality information is available at the Vertebrate Paleontology Laboratory.

Geologic Setting and Regional Stratigraphy

During Late Cretaceous (Campanian) time the Big Bend region of West Texas lay along the western edge of a shallow epicontinental sea, known as the Western Interior

Seaway, that extended from the Gulf of Mexico northward through Montana and Canada.

Throughout the Campanian Stage, transgressive and regressive cycles resulted in deposition of intertonguing marine and coastal sediments all along the western side of the

Seaway (e.g., Kauffman, 1984).

The Aguja Formation is an eastward-thinning series of paralic and marine sandstones that is interbedded with shale and lignite, and reflects deposition in varied shallow marine and coastal plain environments (Lehman, 1985). The fossil vertebrate fauna of the Aguja Formation is well known and includes a wide variety of terrestrial and marine animals (Rowe et al., 1992). However, the marine fauna has not been as extensively studied as the dinosaurs, crocodylians, and turtles.

Lehman (1985) separated the Aguja Formation into several informal members that reflect two major progradational intervals separated by a transgressive marine interval (Fig. 2). The basal sandstone member intertongues with marine shale of the

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underlying Pen Formation, and consists of fine-grained fossiliferous sandstone that

records the initial progradational event in the Big Bend region (Bohannon, 1987). The

lower shale member is composed of interbedded carbonaceous shale and lignite deposited

landward of the prograding shoreline (Record, 1988). The Rattlesnake Mountain

sandstone member is a thin transgressive sandstone interval that represents a shallow

marine shelf environment (Macon, 1994). It is found only in the western part of the Big

Bend region and contains extensive oyster bioherms (Flemingostrea pratti,

Flemingostrea subspatulata, Crassostrea Cusseta, and Crassotrea trigonalis; Macon,

1994). The Ten Bits Microsite is within the Rattlesnake Mountain sandstone. This unit is overlain by an eastwardly thickening interval of marine shale, the McKinney Springs tongue of the Pen Formation (Mosley, 1992).

The Terlingua Creek sandstone member is an extensive coastal and deltainc sandstone interval that resulted from the last progradational event recorded in the Big

Bend area (Lehman, 1985). The upper shale member is the uppermost unit in the Aguja

Formation deposited landward of the shoreline during progradation. This unit consists of mudstone and interbedded lenticular sandstone accumulated in fluvial coastal plain and inland floodplain environments. Its upper contact is gradational with the overlying

Javelina Formation. Most of the known vertebrate fauna of the Aguja Formation has been collected from the upper shale member.

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Stratigraphy of the Ten Bits Microsite

A nearly complete section of the Aguja Formation is exposed in the vicinity of the

Ten Bits Microsite, east of Steep Draw and west of North County Road on Ten Bits

Ranch. The section here is set off by faults, and covered by Quaternary alluvium in places, obscuring parts of the section. The basal sandstone contact with the underlying

Pen Formation is exposed north of the site. South of the Ten Bits Microsite, the upper shale member of the Aguja is overlain by the Devil's Graveyard Formation (Lehman and

Wick, 2010). The strata here dip steeply (about 30 to 80°) to the south. The stratigraphic section measured for the present study was taken adjacent to North County Road with a

Jacob staff and Brunton compass (Fig. 3).

Unit 1 of the section is the basal sandstone member. It is 8 m thick and consists of yellowish-gray, fine-grained, thinly bedded sandstone. Units 2 through 6 are correlated with the lower shale member, here about 44 m in thickness. This interval consists primarily of dark gray mudstone and shale with yellow patches of limonite. Unit

3 is an interval partially covered by colluvium. Unit 4 is a thin lens of fine-grained sandstone, and is overlain by a thin bed of lignite (unit 5). The lower shale member has a gradational upper contact with unit 7, the Rattlesnake Mountain sandstone. This unit is yellowish-gray to white, fine-grained, highly fossiliferous sandstone about 5 m thick. The sandstone is very friable but contains a thin resistant calcite-cemented lens. The Ten Bits

Microsite occurs along the base of this resistant lens where abundant teeth and abraded bone fragments are found in a thin "lag" deposit. This fossiliferous sandstone grades upward into an alternating series of massive to thickly bedded sandstone layers about 12

4 Texas Tech University, Joseph A. Schubert, May 2013 m in thickness (unit 8). These sandstone beds are yellowish-gray to white and fine- grained. Unit 8 is correlated with the Terlingua Creek sandstone member.

If the correlation of units shown here is correct, the Rattlesnake Mountain sandstone appears to grade directly upward into the Terlingua Creek sandstone member in this area, and the McKinney Springs tongue of the Pen Formation has pinched out here. The upper part of unit 8 appears to be in fault contact with the Devil's Graveyard

Formation in the vicinity of the Ten Bits Microsite. However, several hundred meters south and west of this area, the upper shale member is about 30 m in thickness, and exposed in depositional contact with unit 8 (Lehman and Wick, 2010).

Methods

Specimens were initially collected in the field at the Ten Bits Microsite by

"surface picking". This method typically yields only a sample of larger, more readily visible, specimens. Once a representative sample of larger specimens was obtained, unconsolidated sediment matrix was shoveled into burlap sacks for processing in the lab at Texas Tech. Approximately 45 kg of matrix was collected at the site. Five to six kilograms of this matrix was wet-screened through sieves of progressively finer mesh.

The residual coarse concentrate was then examined under an Olympus SZX series binocular microscope at 8X magnification and hand picked for teeth and other skeletal elements. These specimens were used to obtain a representative sample of the smaller taxa preserved at the site.

An additional sample of sediment matrix was processed by Steve Wick at the Ten

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Bits Ranch. This sample was dry-screened and hand picked under a binocular microscope, and is the basis for the biodiversity study of the paper. Specimens that required cleaning were placed in a padded beaker to prevent breakage of the teeth and immersed in water in a sonic cleaner. The cleaning only required ten to fifteen second cycles to achieve the desired results in most cases. If the specimens proved difficult to clean due to encrusting matrix they were immersed in a one percent buffered formic acid solution and agitated with tip of a fine paintbrush. This weak acid proved to be sufficient for cleaning the specimens without damaging the enamel surface. The acid-treated specimens were then placed in the sonic bath for a few seconds to rinse. Using these methods, a total of 4744 specimens were collected.

Examples for each of the teeth and other skeletal elements represented were photographed using a Nikon digital SLR and the Olympus microscope. This setup required a camera mount and specimens photographed directly through the ocular and scope tube. This worked well for larger specimens. Smaller specimens were photographed using a Hitachi S-570 scanning electron microscope at 10 kv to 12 kv and at 30X magnification. This setup provided optimum image detail.

Tooth Morphology and Nomenclature

A variety of conventional terminology is used here to describe the orientation and morphology of elasmobranch teeth (Fig. 4). The labial face of a tooth is the “outer” side facing the mouth opening. The lingual face of a tooth is the “inner” side facing the tongue or throat. The occlusal face is that part that would contact teeth in the opposite

6 Texas Tech University, Joseph A. Schubert, May 2013 jaw during occlusion. The basal face is the bottom of the tooth, or the part that is attached to the jaw. If an axis is drawn down the midline of the animal then the mesial face is the side closest to this axis. The distal face is the one farthest away from the midline. Where the mesial or distal face is viewed this is sometimes said to be a profile view of the tooth

(Fig. 4). Anterior teeth are those situated toward the front of the jaw. Lateral teeth are those located on the sides of the jaw and posterior teeth are those located in the back of the jaw near the jaw hinge.

The teeth of sharks and rays are composed of tiny crystallites of the mineral fluorapatite, which because of its durability results in high preservability compared to softer cartilaginous body parts. The teeth have a central pulp cavity that is surrounded by dentine. There are three types of dentine found in the tooth: pallial dentine, orthodentine and osteodentine (a complete description of dentine was given by Orvig, 1951). An osteodont has teeth with an osteodentine core and no pulp cavity. An orthodont has teeth that are composed of orthodentine with a large pulp cavity (Welton and Farish 1993).

Osteodont and orthodont dentine has a surrounding layer of pallial dentine. The pallial dentine is covered with an enameloid layer to produce a complete tooth crown. The root of the tooth is comprised of osteodentine and is enclosed in the jaw.

While there is great variation in tooth size and shape from prehensile teeth to crushing teeth, all of them share two basic features: the root and the crown. The root anchors the tooth in the mouth of the animal. Roots vary in shape and size and typically exhibit important diagnostic characters (summarized here from Welton and Farish, 1993).

Roots that are flat and tabular are anaulacorhizous. These roots can appear porous and

7 Texas Tech University, Joseph A. Schubert, May 2013 lack nutrient grooves. Holaulacorhizous roots have a well-defined nutrient groove that separates these distal and mesial root lobes. Hemiaulacorizhous roots are those that are broadly triangular in shape if viewed from the basal surface. Polyaulacorizhous roots have many nutrient grooves that are oriented labiolingually resulting in a comb-like appearance with numerous foramina (Welton and Farish, 1993).

The crown of the tooth is the exposed portion of the tooth, and it exhibits the greatest variation in shape, size, and texture. The form of the tooth crown is the principle means of identifying shark species. The crowns of crushing teeth are typically low and flat, and are often closely packed in a pavement arrangement. Prehensile teeth are adapted to grab and hold prey. Prehensile teeth include mesiodistally-compressed blade- like teeth that are adapted to rend flesh from prey and spike-like teeth suited for piercing active prey.

Rostral Teeth

The “sawfishes” (e.g., Sclerorhynchidae and Pristidae) are distinguished on the basis of their elongate, toothed rostrum. The rostrum is composed of prismatic and hyaline cartilage with laterally aligned teeth that form the “saw” and gives these fish their name (Wueringer et al., 2009). The rostral teeth or “spines” are attached to the rostrum via connective tissue and replaced in “conveyor belt” fashion (Wueringer et al. 2009;

Schaeffer, 1963; Case and Springer 1968; Cappetta, 1987). The teeth vary in length from

1 mm to 90 mm or more and can be osteodont or orthodont (Welton and Farish, 1993).

The rostrum and teeth are used to obtain food either be slashing at prey to stun them or by

8 Texas Tech University, Joseph A. Schubert, May 2013 grubbing through bottom sediments. The “saw” may also be used as a means of defense

(Welton and Farish, 1993; Wueringer et. al., 2009). Sclerorhynchidae are represented by as many as 23 genera (Wueringer et. al., 2009) of which several are found in Texas

Cretaceous strata.

The terminology for rostral teeth differs from that of oral teeth is some respects.

The anterior face is the face closest to the tip of the rostrum. The posterior face is the face closest to the tip of the tail. The dorsal face is the side seen when looking down at the top of the animal while the ventral face is the side seen when looking at the belly of the animal (Fig. 4).

Placoid Scales and Dermal Denticles

Placoid scales and dermal denticles are found only in sharks and rays, and are homologous to teeth. They are composed of a large central pulp cavity made of dentine and covered by an enameloid layer (Fig. 4). The scales are attached to the body by connective tissue, with blood vessels and nerves running through a central canal on the scale. Placoid scales are found all over the body in sharks, including inside the mouth, pharynx, and brachial arches (Welton and Farish, 1993). They are non-growing and are subject to periodic replacement by larger scales as the animal grows (Welton and Farish,

1993). Rays tend to have placoid scales scattered more sparsely over the dorsal side of the head, body, and fins (Welton and Farish, 1993). They vary in size and shape depending on where they are found on the animal (Welton and Farish, 1993). Dermal denticles are placoid scales that are enlarged and have a thorn-like appearance (Welton

9 Texas Tech University, Joseph A. Schubert, May 2013 and Farish, 1993). Dermal denticles are prominent on the dorsal midline of rays. The points of the denticles face caudally or posteriorly.

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Figure 1. General geologic map of the Big Bend region of Texas, showing exposures of the Aguja Formation, and location of the Ten Bits Microsite (modified from Lehman, 1985).

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Figure 2. Stratigraphic relationships of the Aguja Formation and Pen Formation in the Big Bend region of Texas (modifed from Lehman, 2008).

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Figure 3. Stratigraphic section of the Aguja Formation exposed along North County Road at Ten Bits Ranch, showing the stratigraphic position of the Ten Bits Microsite.

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Figure 4. Diagram of sawfish (above) showing terminology used for anatomical orientation of rostral spines; dental terminology used for shark and ray teeth (middle of page); and terms used to describe dermal denticles (below; modified from Miyake et al., 1999). 14 Texas Tech University, Joseph A. Schubert, May 2013

CHAPTER 2

SYSTEMATIC PALEONTOLOGY

Family HYBODONTIDAE Owen, 1846

Genus HYBODUS Agassiz, 1837

HYBODUS SP.

Material. Two specimens, one complete (Fig. 5.1) and one partial tooth. The teeth are in good condition, but slightly abraded and polished by postmortem transport.

Description. The largest tooth measures 6 mm in height and 10 mm in width; the second is slightly smaller and fragmentary. The roots are anaulacorhizous. Both teeth exhibit a single central conical cusp and a minute lateral cusplet. The teeth show plications on the labial side, which extend from the base of the enameloid surface to approximately a quarter way up the cusp. The lingual side of the tooth has plications near the cusplet. The plications are not as well developed as those on the labial side and do not extend as far up the cusp. The lingual and labial sides are marked by dark, sinuous, longitudinal bands. In occlusal view, a carina is visible. No foramina are present.

Discussion. Two species of Hybodontidae have been reported in Cretaceous strata of Texas, Hybodus butleri and Hybodus sp. The specimens are very small and difficult to collect without bulk sampling and sorting under a microscope (Welton and

Farrish, 1993).

The characteristics that distinguish H. butleri from other hybodontids include a lack of lateral cusplets, longitudinal ridges that extend halfway up the cusp and a short

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median cusp (Welton and Farrish, 1993). Hybodus sp. has characteristics that include a tall median cusp with a pair of widely spaced lateral cusplets. Labial and lingual sides of the tooth have widely spaced strong longitudinal plications extending from the base of the enameloid to half the height of the apex (Welton and Farrish, 1993). A ridge extends mesodistally between cusp and cusplet (Welton and Farrish, 1993).

Hybodus montanensis has not been reported from Texas, but is characterized by plications on the labial side of the tooth that extend from the base of enameloid border to roughly a quarter way up the cusp. A faint carina is evident when viewed labial-lingually

(Case, 1978). Lateral cusplets are present. The root is anaulacorhizous with distinct foramina on both the labial and lingual sides (Case, 1978). The size of teeth reported ranges from 0.5 cm to 2.5 cm. This species is known from the Judith River Formation in

Montana (Case, 1978). There are no distinct foramina present on the Ten Bits specimens to indicate that the teeth could represent Hybodus montanensis.

Of the two species found in Texas, the characteristics of H butleri do not match those found on the specimen from the Ten Bits Microsite. H. butleri is also found in older

Aptian- Albian strata. The description of Hybodus sp. more closely matches the observed features on the specimens from Ten Bits Microsite.

Family LONCHIDIIDAE Herman, 1977

Genus LONCHIDION Estes, 1964

LONCHIDION SELACHOS Estes, 1964

Material. Nine specimens, four complete, and five fragmentary teeth. All

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specimens lack roots.

Description. The specimens are gracile in appearance (Fig. 5.5). Complete

specimens vary in size from 1.5 mm to 3 mm in mesodistal width. They have a low

crown height and are wider mesodistally than they are labiolingually. The crowns are

peaked and smooth with no ornamentation. Cusplets are not easily identifiable, probably

due to the amount of postmortem wear. The meso and distal ends exhibit a slight upward

curve. A transverse ridge is present on several of the teeth that are less worn. The

specimens display a strong labial protuberance. Both labial and lingual faces are smooth.

There is a slight concavity on the lingual face, visible when viewed from the occlusal

surface. The crown is constricted toward the base.

Discussion. During the past 25 years, Lonchidion Esstes 1964 and Lissodus

Brough 1935 were revised and placed in synonymy by Duffin (1985), but then

reconsidered by Antunes et al. (1990) and considered to represent more than two taxa.

Rees and Underwood (2002) further divided Lissodus into five genera: Lissodus,

Vectiselachos, Hylaeobatis, Parvodus and Lonchidion. For a review of the status of

Lissodus see Rees and Underwood (2002).

Lonchidion selachos is defined by its gracile appearance in comparison to

Vectiselachos, Lissodus and Hylaeobatis (Rees and Underwood, 2002). In comparison

with the gracile teeth of Parvodus, Lonchidion has minute cusplets as the identifying

trait, while the lateral cusplets in Parvodus are larger and well defined (Rees and

Underwood, 2002). Additionally Parvodus lacks the well-defined crown shoulders of

Lonchidion (Rees and Underwood, 2002).

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Welton and Farish (1993) listed two species found in the Cretaceous of Texas:

Lissodus anitae and Lissodus selachos (now considered Lonchidion anitae and

Lonchidion selachos using the taxonomy of Rees and Underwood 2002).

Lonchidion anitae is distinguished in having a cuspate transverse ridge, and its

much smaller size in comparison to all other species. It is only known from Albian strata

in Texas (Welton and Farish, 1993). Lonchidion selachos is distinguished by its larger

size, greater width and lower crown height, and is known from the Campanian of Texas

(Welton and Farish, 1993). Specimens found on the Ten Bits Microsite clearly pertain to

Lonchidion selachos.

Family GINGLYMOSTOMATIDAE Gill, 1862

Genus CANTIOSCYLLIUM Woodward, 1889

CANTIOSCYLLIUM aff. MEYERI Case and Cappetta, 1997

Material. Six fragmentary specimens lacking complete roots, 1 anterior tooth and

5 lateral teeth.

Description. The specimens vary from 1 mm to 3 mm in mesiodistal width (Fig.

5.7). The anterior tooth displays a single abraded central cusp with no cusplets. The lateral teeth have crowns with a strong central cusp flanked by a pair of rounded lateral cusplets. The labial apron is large, rounded, and has some sinuous longitudinal folds that extend partially up the crown.

Discussion. Four species share similarities with the specimens from the Ten Bits

Microsite. These include Chiloscyllium greeni, Plicatoscyllium minutum, Cantioscyllium

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decipiens, and Cantioscyllium meyeri.

The teeth of Chiloscyllium greeni are small with a central median cusp and a pair of lateral cusplets (Williamson et al, 1993 and Welton and Farish, 1993). The teeth display a broad, rounded labial apron or flange that extends partly over the root. The root has a central basal foramen and a pair of margino-lingual foramina (Williamson et al.,

1993; Welton and Farish, 1993). The small size, lack of ornamentation, and pair of lateral cusplets are distinguishing characteristics for Chiloscyllium greeni (Welton and Farish,

1993).

Plicatoscyllium minutum was formerly assigned to Ginglymostoma lehneri;

(Welton and Farish, 1993; see Cappetta and Case, 1997, Noubhani and Cappetta, 1997 for synonymy). The teeth in this species differ from those of other orectolobids in having numerous short cusplets flanking a short central cusp and a broadly triangular high crown. The teeth also have strong and irregular enameloid ridges on the labial crown face

(Welton and Farish, 1993).

Cantioscyllium decipiens, previously reported from Cenomanian through

Coniacian strata in Texas, has a robust crown with numerous strong longitudinal ridges on the labial face (Welton and Farish, (1993).

Cantioscyllium meyeri was erected by Case and Cappetta (1997) for teeth found in Maastrichtian strata of Texas. C. meyeri has small teeth, less than 2.5 mm in height; anterior teeth displaying a sharp conical cusp devoid of basal cusplets, and a large round basal apron that does not quite reach the basal face of the root. The crowns have sinuous but not very pronounced folds along the labial face (Case and Cappetta, 1997). A pair of

19 Texas Tech University, Joseph A. Schubert, May 2013

small, blunt, lateral cusplets is differentiated from the cusp (Case and Cappetta, 1997).

Lateral teeth have a very broad low crown without cusplets differentiated from the central cusp (Case and Cappetta, 1997).

The teeth of Chiloscyllium greeni have a smooth crown, those of Plicatoscyllium minutum have numerous short cusplets flanking the central cusp, and those of

Cantioscyllium decipiens have more prominent and numerous labial ridges compared to those from the Tens Bits Microsite. It is unlikely that the Ten Bits specimens pertain to any of these species. The specimens found at the Ten Bits Microsite are most similar to those illustrated by Case and Cappetta (1997) and assigned to Cantioscyllium meyeri, however, additional specimens and further study may be needed to verify the identity of the Ten Bits specimens.

Family GINGLYMOSTOMATIDAE Gill, 1862

Genus CHILOSCYLLIUM Muller and Henle, 1837

CHILOSCYLLIUM aff. GREENI Cappetta, 1973

Material. Approximately 46 complete and fragmentary teeth. The majority of the specimens lack roots.

Description. The teeth are small; the most complete specimen has a height of 2 mm from base of root to apex of crown, and a mesiodistal crown width of 1.75 mm (Fig.

5.9). Several of the larger specimens have a mesiodistal crown width of 3 mm but lack the root for height determination. The crown has a large, rounded, central, conical cusp flanked by a pair of smaller mesial and distal cusplets. The cusplets are rounded,

20 Texas Tech University, Joseph A. Schubert, May 2013

probably due to wear, and in most cases the cusplets diverge from the centerline of the tooth. The base of the crown has a labial flange or apron that varies in shape from bilobate to nearly circular. The labial flange has a shallow concavity medially. Some teeth display what may be pressure scarring on the medial concavity from adjacent teeth of the file. The labial flange overhangs the root. The specimens lack distinct labial ornamentation. In profile, the cusp slopes downward labially and upward lingually. The root, lingual protuberance, and large central cusp form a ninety-degree angle. The lingual face is smooth and has a lingual protuberance that extends to the root. The root is hemiaulacorhizous, heart-shaped in basal view, with a central foramen. There are two additional foramina on the root shoulders on either side of the lingual protuberance.

There is also a partially enclosed central foramen on the lingual root face; this portion of the root appears somewhat like a nutrient groove that connects with the central basal foramen.

Disscussion. Texas Cretaceous strata have produced numerous orectoblobiforms including, but not limited to Cantioscyllium decipiens, Cantioscyllium meyeri,

Plicatoscyllium minutum and Chiloscyllium greeni. All of these teeth share the same hemiaulacorhizous root and orthodont histology.

Cantioscyllium decipiens is known from Cenomanian to Coniacian strata in

Texas. These teeth display a short and strong central cusp that is flanked by one to three pair of cusplets and a broad labial apron or flange (Welton and Farish, 1993). The distinguishing characteristics for C. decipiens include numerous distinct labial striations and a robust crown (Welton and Farish, 1993).

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Teeth of Cantioscyllium meyeri illustrated by Cappetta and Case (1997) are very small, with a height of less than 2.5 mm, and anterior teeth that display a sharp, conical cusp devoid of lateral cusplets, and a large rounded apron that does not extend to the basal face of the root (Case and Cappetta, 1997). The labial apron of the crown exhibits

“flexuous and not very salient folds” (Case and Cappetta, 1997).

Plicatoscyllium minutum, formerly referred to Ginglymostoma lehneri (Welton and Farish, 1993), exhibit a broadly triangular crown and a short central cusp flanked by three to four pairs of lateral cusplets. The labial apron is broad and has “numerous irregular longitudinal enameloid plications” (Welton and Farish, 1993).

The teeth of Chiloscyllium greeni exhibit a smooth crown with a broadly triangular central cusp (Welton and Farish, 1993). There is a single pair of mesial and distal cusplets, and a wide labial crown flange that overhangs the crown foot almost to the base of the root (Welton and Farish, 1993). Chiloscyllium greeni exhibits a strong labial protuberance, a root that is strongly bilobate, a central basal foramen and a basal attachment surface that is concave and oriented at ninety degrees to the crown (Welton and Farish, 1993). The distinguishing features of C. greeni are its small size, smooth crown, and single pair of cusplets (Welton and Farish, 1993).

The specimens from Ten Bits Microsite are most similar to those of C. greeni.

The most prominent characteristics include the smooth crown and single pair of cusplets surrounding a central cusp. Chiloscyllium greeni has a range from Cenomanian to

Coniacian (Welton and Farish, 1993). If the specimens from the Ten Bits Microsite do indeed pertain to C. greeni, then this would represent a range extension into the

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Campanian. It would also be the first reported occurrence of this species in the Big Bend region.

Family ORECTOLOBIDAE Jordan and Fowler, 1903

Genus CRETORECTOLOBUS Case, 1978

CRETORECTOLOBUS OLSONI Case, 1978

Material. Twenty complete and fragmentary teeth.

Description. The teeth range from 1 mm to 2 mm in mesodistal width and have a single high conical cusp that is inclined lingually (Fig. 5.12). The cusp is flanked by low mesial and distal shoulders. The crown is smooth and unadorned. A prominent and narrow labial flange extends to the base of the root. On complete teeth, the root extends lingually and displays a prominent lingual protuberance. There are two distinct lingual foramina on either side of the lingual crown foot. The root is holaulacorizhous and displays a distinct nutrient groove with a central foramen visible in basal aspect.

Discussion. Cretorectolobus olsoni was first described by Case (1978) based on specimens found in the Campanian Judith River Formation of Montana. The partially open medial groove present on the root base distinguishes C. olsoni from superficially similar teeth of Squatinidae (Case, 1978). Case (1987) illustrated additional specimens from the Campanian Teapot Sandstone Member (Mesaverde Formation) that have a high elevated cusp with rounded enameled shoulders. The lateral teeth show a distinctive labial apron that overhangs the root and in lingual aspect fenestrations are visible on either side of a root boss (Case, 1987).

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Welton and Farish (1993) also noted the well-defined nutrient groove on the basal surface as the distinguishing characteristic for Cretorectolobus. The specimens they illustrated have a crown with a single narrow cusp and long, low mesial and distal shoulders, a labial flange that extends to the base of the root foot, and a crown foot that extends over a prominent lingual root protuberance (Welton and Farish, 1993). The basal attachment surface of the root is subdivided by the nutrient groove; the root is holaulacorizhous (Welton and Farish, 1993).

Siverson (1995) provided an emended diagnosis for Cretorectolubus and in the process questioned its position within Orectolobidae. Like Case (1978, 1987) and Welton and Farrish (1993), Siverson also noted the frequent development of an holaulacorizhous root, and the presence of cusplets on anterior teeth as a characteristic separating Squatina from Cretorectolobus.

Material available from the Ten Bits Microsite is insufficient to evaluate the position of Cretorectolobus within Orectolobidae, but the specimens have a distinct nutrient groove and holaulacorizhous root not found in teeth of Squatina hassei that are also found at the site. These features provide a basis for assignment to Cretorectolobus olsoni.

Family SQUATINIDAE Bonaparte, 1838

Genus SQUATINA Dumeril, 1906

SQUATINA HASSEI Leriche, 1929

Material. A single complete specimen (Fig. 5.17).

24 Texas Tech University, Joseph A. Schubert, May 2013

Description. The specimen is approximately 3.5 mm in mesodistal width and 2 mm in height measured from the base of the root to apex of the crown. The specimen has a single central cusp that broadens toward the base. No cusplets are present. The base of the crown is wide with two low mesial and distal shoulders. The crown is smooth both labially and lingually. The tooth exhibits a well-developed labial flange. In basal view, the root is roughly triangular and concave. The root projects lingually and intersects the crown at nearly a right angle. There is a single central foramen on the lingual medial root face. The root exhibits what appear to be faint and short corrugations. The corrugations could represent filled nutritive foramina. The root is hemiaulacorhizous.

Discussion. The single specimen from Ten Bits Microsite exhibits similarities with two species. One is Cretorectolobus sp., which has a single central cusp with low mesial and distal shoulders, a prominent labial flange, smooth crown faces and a triangular root. A second possibility is Squatina hassei, which also has a single central cusp with low mesial and distal shoulders, smooth crown faces and a triangular root in basal view.

Siverson (1995) pointed out that the characteristics distinguishing

Cretorectolobus sp. and Squatina hassei is the hemiaulacorhizous root and absence of shoulder cusplets found on S. hassei. The tooth from the Ten Bits Microsite has a hemiaulacorhizous root. In addition, the specimens illustrated by Welton and Farish

(1993) and Becker et al (2006) as Squatina hassei share the same features as the Ten Bits specimen.

25 Texas Tech University, Joseph A. Schubert, May 2013

Family CRETOXYRHINIDAE Glickman, 1958

Genus CRETALAMNA Glickman, 1958

CRETALAMNA APPENDICULATA Agassiz, 1843

Material. Three fragmentary teeth.

Description. The teeth vary from 5 mm to 14 mm in mesiodistal width (Fig.

5.19). The crown has a high central cusp that is smooth and unadorned. The lingual face of the crown is convex and the labial side is flat or slightly convex. The central cusp has two smaller divergent cusps on its flanks; the smaller cusps are broadly triangular. The largest of the three specimens displays a well-developed dental band. The dental band is faint on the smaller specimens. The thin lines in the enamel do not appear to be true striations, but instead possibly fractures that resulted from poor preservation. The roots are holaulacorhizous, incomplete on all specimens, but lack a nutrient groove. The foramina are obscured.

Discussion. Teeth of Cretalamna appendiculata are widespread in Cretaceous strata of Texas and are distributed stratigraphically from Albian through Maastrichtian

(Welton and Farish, 1993). The distinguishing characteristics of Cretalamna in comparison to other Cretaceous laminoid sharks include a smooth crown with broad triangular cusplets, angular root lobes, and absence of a nutrient groove (Welton and

Farish, 1993). Shimada (2007) describes C. appendiculata as having bilaterally symmetrical to highly asymmetrical teeth with a flat central triangular cusp flanked by a pair of smaller divergent triangular cusplets. The roots are bilobate, with a relatively low lingual protuberance that may display a single nutritive foramen (Shimada, 2007).

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Lateral teeth of Scapanorhynchus texanus can be confused with lateral teeth from

C. appendiculata, and S. texanus is also known from the Ten Bits Microsite. S. texanus

lateral teeth also have a crown that is flattened and compressed, however, the root lobes

are rounded, rather than squared off and angular as in C. appendiculata (Welton and

Farish, 1993).

Serratolamna serrata is another lamniform shark found in Texas Cretaceous

strata. It is found rarely in the upper Taylor Group, but occurs commonly in the Navarro

Group (Welton and Farish, 1993). However S. serrata has a pronounced asymmetrical

tooth with multiple divergent cusplets, smooth crown faces, and a root that displays a

short nutrient groove (Welton and Farish, 1993).

The teeth from Ten Bits Microsite have the broad triangular principal cusp

flanked by a pair of broad divergent triangular cusplets characteristic of Cretolamna

appendiculata. The specimens also lack the nutrient groove that is found in

Scapanorhynchus and Serratolamna. Additional specimens with more complete roots are

needed to confidently identify the Ten Bits specimens as C. appendiculata.

Family ANACORACIDAE Casier, 1947

Genus SQUALICORAX Whitley, 1939

SQUALICORAX KAUPI, Agassiz, 1843

Material. 26 complete and fragmentary anterior and lateral teeth.

Description. The five complete specimens vary in height from 6 mm to 14 mm measured from the apex to the base of the root; the width of the teeth vary from 7 mm to

27 Texas Tech University, Joseph A. Schubert, May 2013

16 mm (Fig. 5.21). The labial sides of the teeth have a slight to moderate convexity. The teeth on the lingual side show multiple foramina on some of the specimens. The teeth are labiolingually compressed, and have a long crescent-shaped mesial cutting edge with serrations extending to the apex of the crown. The serrations continue down the distal side of the crown to an indentation where a small distal blade is formed. The crown is high and has an acute angled apex. The root is anaulocorhizous.

One specimen displays what appears to be a pathological deformity (Fig. 5.23).

The tooth is approximately 12 mm in mesiodistal width and 10 mm from apex of the crown to the base of the root. The crown is split in two by a 1 mm gap that extends from the apex to the crown foot. The distal portion makes up three quarters of the total width of the tooth. Both portions are fully enameled. The crown displays serrations with the distal portion showing the serrations from the crown foot half way up the edge then stopping at a small offset. From this offset the serrations continue around and down into the gap. The mesial portion displays serrations from the gap in the crown to the crown foot. The lingual face displays enameled protrusions from mid tooth. The labial face has a single fold of enamel. The root has a normal morphology.

Discussion. Four named species of Squalicorax are found in Texas Cretaceous strata: S. curvatus, S. falcatus, S. kaupi, and S. pristodontus Squalicorax curvatus is distinguished from other species by having a low, massive crown, a low root with a convex labial crown face, an acute crown apex and angular mesial cutting ridge (Welton and Farrish, 1993). S. curvatus is known only from Cenomanian strata. Squalicorax falcatus is distinguished by having a lower root than S. kaupi and a more weakly convex

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mesial cutting edge than either S. kaupi or S. pristodontus (Welton and Farish, 1993).

Squalicorax pristodontus is distinguished by having a much higher root than the other

species, and in lacking a distinct distal cutting blade. In addition, some examples of S.

pristodontus show crown curvature when viewed labiolingually with a highly convex

lingual face and a highly concave labial side (Welton and Farrish, 1993). Squalicorax

kaupi is distinguished by having a high, convex mesial cutting edge with coarse

serrations and a low well-defined distal cutting blade (Welton and Farish, 1993).

Specimens found at the Ten Bits Microsite strongly resemble those of

Squalicorax kaupi. Complete examples show the distinctive distal cutting blade and

indentation that is lacking in S. pristodontus; they also exhibit a high convex mesial

cutting edge. No specimen exhibits the strong convexity and concavity when viewed

edgewise that is a trait of S. pristodontus. None of the specimens exhibit the low massive

crown found with S. curvatus or S. falcatus or a weakly convex mesial cutting edge.

Family ANACORACIDAE Casier, 1947

Genus SQUALICORAX Whitley, 1939

SQUALICORAX PRISTODONTUS ?, Agassiz, 1843

Material. Two specimens. One specimen is complete and well preserved; the other is abraded.

Description. The teeth are approximately 14 mm in height, measured from the base of the root to the apex of the crown, and vary in width from 13 to 16 mm. The complete specimen displays a crescent-shaped, serrated mesial cutting edge that extends

29 Texas Tech University, Joseph A. Schubert, May 2013

to the apex and down the distal side of the tooth (Fig. 6.1). The distal edge and distal blade are not differentiated with a distinct intersection or notch but grade smoothly into one another. The labial face is convex while the lingual face is straight. The root is high with a prominent dental band on the labial side. The lingual side displays numerous foramina. The root is anaulacorizhous with well-developed lobes. The abraded specimen has a crescent-shaped crown, but the cutting edges are non-serrated and the distal blade is lacking due to wear.

Discussion. Welton and Farish (1993; p. 119) described S. pristodontus as having a “much higher root and lacking a distinct distal cutting blade” compared with teeth of S. kaupi.. Similarly, Case and Cappetta (1997) note the higher root and lack of a differentiated distal heel, but in addition point out that S. pristodontus is twice as large as

S. kaupi.

The two teeth from the Ten Bits Microsite are problematic. The specimens clearly are not S. falcatus or S. curvatus. They share some of the features of S. pristodontus. The complete specimen has a high root and lacks a distinct distal notch or blade. They compare favorably with specimens of S. pristodontus illustrated by Shimada and

Cicimurri (2006; figure 1B FHSM VP -15010). However, they may well be comparable to one shown by Welton and Farish (1993; their page 118 figure 1a) as S. kaupi. The abraded specimen displays the strong labial convexity and lingual concavity associated with S. pristodontus, and also compares favorably with one shown by Welton and Farish

(1993; their figure 1b, page 119).

30 Texas Tech University, Joseph A. Schubert, May 2013

Family MITSUKURINIDAE Jordan 1898

Genus SCAPANORHYNCHUS Woodward, 1889

SCAPANORHYNCHUS TEXANUS (Roemer, 1852)

Material. Approximately 165 complete and fragmentary anterior and lateral teeth, and 2 posterior teeth. The overall preservational quality of the teeth ranges widely, from abraded and highly polished specimens to those with a pristine surface.

Description. The anterior teeth range in length from 3 mm to 20 mm (from apex to base of root), and in width from 2 mm to 6 mm (Fig. 6.4). A typical anterior tooth has a long narrow sigmoidal cusp. The labial face of the cusp is relatively flat; the lingual face is highly convex. On the lingual face, parallel longitudinal ridges extend from the base of the crown to near the apex. The labial face is smooth. The anterior teeth lack cusplets.

The lateral teeth range in length from 5 mm to 21 mm (from apex of central cusp to base of root); width ranges from 3 mm to 13 mm. A typical lateral tooth has a mesiodistally broader crown, resulting in a flatter appearance. The majority of teeth display one pair of cusplets, a few have two pair. The longitudinal ridges so pronounced on anterior teeth are not present on lateral teeth. Typically, the teeth are smooth on both labial and lingual faces with only occasional fractures present on the enameled surface.

The posterior teeth have the same characteristics as lateral teeth; however these have a distally angled cusp.

The roots of the teeth are holaulacorizhous and shows well developed narrow lobes. A lingual protuberance is present but the associated nutrient groove is missing on

31 Texas Tech University, Joseph A. Schubert, May 2013

many examples. Teeth that display the nutrient groove are in a better state of preservation and were subject to less abrasion. The foramen is difficult to distinguish on many examples.

Discussion. Cretolamna appendiculata is similar to Scapanorhynchus texanus and the two typically occur together in Texas Cretaceous strata. However, C. appendiculata is distinguished by having a smooth crown, single pair of broad triangular cusplets, angular root lobes, and lacking a nutrient groove on the lingual root protuberance (Welton and Farrish, 1993). Specimens from the Ten Bits Microsite lack the broad triangular cusplets that distinguish C. appendiculata from other lamnoids including

Scapanorhynchus.

Two species of Scapanorhynchus have been reported in Cretaceous strata of

Texas, S. raphiodon and S. texanus. Specimens identified as S. raphiodon are distinguished from those of S. texanus by their overall smaller size, weaker lingual striations, narrower crown and larger lateral cusplets (Welton and Farrish, 1993).

S. texanus has strongly defined parallel lingual striations, larger size, and smaller cusplets on lateral teeth (Welton and Farrish, 1993). In addition S. texanus may be indentified by a narrow band of vertical striations at the base of the enameled portion of the labial side of the cusp. Teeth that lack this band are assigned to S. raphiodon while teeth that have it are identified as S. texanus (Meyer, 1974). Confident identification of S. raphiodon is, however, problematic and S. raphiodon is considered by some authors as a junior synonym of S. texanus (see Hamm and Shimada, 2002; Meyer, 1974; Siverson 1992;

Welton and Farrish, 1993). Supposed morphological differences may simply reflect

32 Texas Tech University, Joseph A. Schubert, May 2013

temporal variation within S. texanus.

The specimens from the Ten Bits Microsite strongly resemble those described by

Welton and Farrish (1993) as S. texanus. However, the abraded and polished state of

many teeth precludes the preservation of the diagnostic cusp striations. Teeth that are in a

more pristine condition tend to display the striations, and this supports their identification

as S. texanus.

Family RHINOBATIDAE Muller and Henke, 1838

Genus RHINOBATOS Link, 1790

RHINOBATOS CASIERI, Herman 1977

Material. 14 complete and fragmentary specimens.

Description. The specimens range in mesodistal width from .5 mm to 1 mm (Fig.

6.10). The largest specimen has a length of 1.5 mm from root to apex. The teeth exhibit smooth, worn, unadorned crowns. The crowns are relatively high. A few specimens exhibit a weak transverse ridge on the lingual edge of the crown. Other specimens are abraded and do not exhibit this feature. A medial lingual uvula is flanked by two smaller mesial and distal uvulae. The mesial and distal uvulae are approximately half the length of the central lingual uvula. The specimens are labiolingually compressed. Complete teeth display a well-defined nutrient groove in the center of the root. The root is inclined upward toward the labial face. The root flares at the base and is constricted toward the root-crown interface. The root is extended lingually.

Discussion. Several species of rhinobatids are found in Upper Cretaceous strata of

33 Texas Tech University, Joseph A. Schubert, May 2013

Texas. Rhinobatos uvulatus is found in the Maastrichtian Navarro Group, (Kemp

Formation), and is distinguished in having teeth that are small and longer than they are wide (Case and Cappetta, 1997). R. uvulatus has a long central lingual uvula flanked by two smaller uvulae. The crown is not very high and has a marked transverse keel, with a flattened area just behind the keel (Case and Cappetta, 1997).

Rhinobatos craddocki is also known from the Maastrichtian Navarro Group, and is distinguished in having very small teeth that are less than 1.5 mm in total length (Case and Cappetta, 1997). Case and Cappetta (1997) indicate that the teeth are wider than they are long, and have a marked transverse keel that divides the crown. A central lingual uvula is short, rounded and well separated from the lingual margin. The lingual margin displays some irregular, blunt folds. The root is narrower than the crown. Lateral uvulae are not present.

Rhinobatos incertus has a crown that is cuspate, wide, not very high, with more robust protuberances and a root that is not lingually extended (Welton and Farish, 1993).

The cusp varies from pronounced to absent and is located toward the center of the crown.

More cuspate crowns tend to appear on presumed males more than on presumed females of the species suggesting that R. incertus exhibits strong sexual dimorphic heterodonty

(Welton and Farish, 1993).

Rhinobatos casieri is known from the Campanian of Texas. Welton and Farish

(1993) have described specimens of R. casieri as having a high, labiolingually narrow, mesodistally expanded crown with a lingual face that is convex, smooth and with a gentle convex transverse ridge. A moderately long medial protuberance is flanked by smaller

34 Texas Tech University, Joseph A. Schubert, May 2013

mesial and distal protuberances (Welton and Farish, 1993). The root is lingually displaced and slightly wider than the crown with root lobes that are convex basally, short and somewhat narrow (Welton and Farish, 1993). Like R. incertus there maybe strong sexual heterodonty between males and females with inferred males having teeth that are high crowned and almost cuspate while female teeth are blunt (Welton and Farish, 1993).

Specimens found at the Ten Bits Microsite resemble R. casieri illustrated by

Welton and Farish (1993). The specimens lack the long medial uvula of R. uvulatus shown by Case and Cappetta (1997). The specimens from the Ten Bits Microsite also have well defined lateral or mesial and distal uvulae that are apparently lacking on R. craddocki. In addition, the Ten Bits specimens display a root structure that is lingually extended compared to that of R. incertus. The specimens are not cuspate.

Family HYPSOBATIDAE Cappetta, 1992

Genus PROTOPLATYRHINA Case, 1978

PROTOPLATYRHINA RENAE Case, 1978

Material. 63 complete and fragmentary teeth.

Description. The teeth range from 1 mm to 5 mm in mesiodistal width (Fig.

6.14). The crowns are smooth, unadorned, thick, and somewhat rounded with a weak ovoid outline in occlusal aspect. There is a weak lingual flange on a few specimens, while others lack this trait. Most of the teeth lack roots. Specimens that retain their roots have a well-defined bilobate root with a nutrient groove. The root does not extend beyond the width of the crown on complete specimens. A central nutrient pore is present on some

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specimens.

Discussion. Protoplatyrhina renae was first described by Case (1978) from the

Campanian Judith River Formation in Montana. P. renae has been reported from Texas

Cretaceous strata by Welton and Farish (1993), and by Case and Cappetta (1997) from the Maastrichtian Kemp Formation (Navarro Group).

Protoplatyrhina renae is distinguished from all other Texas Cretaceous rays by its bulbous crown that lacks distinct faces, its weak lingual protuberance, and root that is not expanded beyond the crown foot (Welton and Farish, 1993). Becker et al. (2004) noted additional distinguishing characteristics for Protoplatyrhina renae including a thick oval crown, an occlusal surface that is smooth and rounded, and the presence of a lingual flange.

Pseudohypolophus mcnultyi is another Texas Cretaceous ray that may be confused with P. renae. However, P. mcnultyi has a hexagonal crown (Becker et. al.

2004; Welton and Farish, 1993). Becker et al. (2004) also pointed out that

Pseudohypolophus mcnultyi has a crown that extends over its bilobate root. The specimens from Ten Bits Microsite display all of the diagnostic characteristics for

Protoplatyrhina ranae, and similar specimens found in the contemporaneous Judith River

Formation of Montana support its identification in Texas Campanian strata.

Family SCLERORHYNCHIDAE Cappetta, 1974

Genus ISCHYRHIZA Leidy, 1856

ISCHYRHIZA cf. AVONICOLA Estes, 1964

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Material. Five complete and fragmentary rostral teeth.

Description. The specimens are approximately 1 mm at the widest point on the root (Fig. 6.18). The root is wide at the base and narrows to a short peduncle. The crowns are short with an anterior convex carina that extends apically forming a dorsoventrally compressed blade. The crown base of one specimen displays a short, raised enameloid protuberance that extend apically around the crown. The other specimens are worn and this feature is hard to distinguish.

Discussion. These specimens share characteristics associated with the rostral teeth of I. avonicola as described by Welton and Farish (1993), Cappetta and Case (1975) and

Becker et al (2006). Thus far, no oral teeth have been found for I. avonicola at the Ten

Bits Microsite, which would help in identification of this species.

Family SCLERORHYNCHIDAE Cappetta, 1974

Genus ISCHYRHIZA Leidy, 1856

ISCHYRHIZA MIRA Leidy, 1856

Material. Seven fragmentary rostral teeth and approximately 216 whole and fragmentary oral teeth. Most of the oral teeth are complete and only mildly abraded. The rostral teeth are fragmentary and lack complete crowns.

Description (rostral teeth). One rostral tooth specimen has a complete root that displays a deep channel separating the root into two lobes (Fig. 6.25). The edges of the lobes have several furrows that extend toward the apex of the crown. The furrows do not exceed a quarter of the root length. The root is expanded basally. The enamel on the

37 Texas Tech University, Joseph A. Schubert, May 2013

crown is smooth and thick. Longitudinal ridges at the base of the crown extend toward the apex. The largest specimen is 17 mm in length (lacking the tip of the crown) and 7 mm in width.

Description (oral teeth). Typical oral tooth specimens from the collection measure 4 mm in labiolingual length, 4 mm in mesodistal width, and 4 mm in height measured from the base of the root to the apex of the crown (Fig. 6.22). The root is strongly bilobate with a deep nutrient groove and nutritive foramina on the lingual side.

The root lobes are triangular in basal view. A labial protuberance extends beyond the edge of the root perimeter. There is a lingual protuberance that is slightly deflected below the crown foot into the root region. The crown has a rising conical projection that is inclined anterior to posterior. Low symmetrical, crown shoulders are evident in occlusal view. The crown is smooth and unadorned.

Discussion. Five genera of sclerorhynchid rays have been reported from Texas

Cretaceous strata. These include Ischyrhiza Leidy 1856, Onchopristis Stromer 1917,

Sclerorhyncus Woodward 1889, Schizorhiza Weiler 1930 and Onchosaurus Gervais 1852

(Welton and Farish, 1993). Four species have ranges that extend into the Campanian.

Welton and Farish (1993) described the oral teeth of I. avonicola as very small,

(less than 2 mm) with an inflated crown that lacks a distinct cusp and a lingual face that is slightly inclined labially. The crown displays numerous transverse ridges that break up into rugosities near the crown foot (Welton and Farish, 1993). The lack of a distinct crown cusp and the rugosity of the crown are diagnostic of this species. The rostral teeth have a wide root and a short crown with enameloid plications near the crown base.

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Beavan and Russell (1999) described Ischyrhiza mira oral teeth as having a short and rounded main cusp; gently sloping broad shoulders; a labial flange that extends below the crown foot; roots that are bilobed and triangular, separated by a nutrient groove with a single central foramen between the lobes, and with a single foramen on the lingual side of each lobe.

The rostral teeth have dorsoventrally flattened crowns that curve slightly posteriorly and ventrally; enamel that is smooth with longitudinal ridges; a tall root that expands toward the base, with a single deep anterior and posterior groove (Beavan and

Russell, 1999).

The oral teeth of Sclerorhynchus sp. are very small, (approximately 1 mm). The crowns are typically triangular with a weak cusp. The lingual protuberance is sturdy, while the labial protuberance is weak. The oral teeth also have a unique ridge pattern that extends toward the apex on the labial face. The ridges appear to radiate from the apex of the cusp. The rostral teeth of this sawfish are described as dorsally compressed and smooth, with an anterior cutting edge that is slightly convex and a distal cutting edge that displays a single basal barb-like projection (Becker et al., 2006).

The sawfish Onchosaurus pharao has enormous rostral teeth. Lehman (1989) described these as having a peduncle that is strongly rectangular in basal cross section with a anteroposterior width (24-36 mm) that is greater than the dorsoventral width (15-

20 mm); with a pronounced groove that runs the entire length of the peduncle and shaft; dorsal and ventral surfaces that are deeply striated, and an indented attachment surface that contains a small centrally located pit.

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The specimens from the Ten Bits Microsite clearly pertain to Ischyrhiza mira.

Family SCLERORHYNCHIDAE Cappetta, 1974

INCERTAE SEDIS

Specimens representing four different types of sclerorhynchid rostral teeth cannot be assigned to either Ischyrhiza avonicola or to I. mira. It has not been possible thus far to identify these rostral teeth with other sawfishes. They are described here informally as morphotypes 1 through 4.

MORPHOTYPE 1

Material. One fragmentary specimen.

Description (type 1 rostral teeth). The root from this specimen is incomplete with only the upper portion intact where it merges into the crown base (Fig. 9.1). The crown is short, robust, and conical. The crown is unadorned and inclined slightly posteriorly.

MORPHOTYPE 2

Material. One fragmentary specimen.

Description (type 2 rostral teeth). The fragmentary peduncle is wide and narrows to a short shaft. The crown is compressed anterodorsally. There is a single carina that extends from the crown foot to the apex; otherwise the crown is unadorned. The crown is inclined sharply posteriorly (Fig. 9.3).

40 Texas Tech University, Joseph A. Schubert, May 2013

MORPHOTYPE 3

Material. Three fragmentary rostral teeth.

Description (type 3 rostral teeth). The roots on the specimens are incomplete

(Fig. 9.6). One tooth has half of a root and extrapolating from that, the base of the peduncle is wide and narrow to a short neck. The crowns are long, blade like and dorsoventrally compressed. The crowns are slightly inclined posteriorly. There is an anterior carina that extends from the foot of the crown toward the apex. The carina is deflected from the anterior face midline. The teeth have enameloid folds that extend halfway up the crown and mimic the deflection of the anterior carina.

MORPHOTYPE 4

Material. 16 complete and fragmentary specimens.

Description (type 4 rostral teeth). The base of the peduncle is wide and varies from 1 mm to 2 mm in width and compressed anterodorsally (Fig. 9.9). The crowns are conical with a slight posterior inclination. Several teeth display a small carina at the crown foot that is not as prominent as in other rostral teeth described. Other type 5 specimens lack this lack this feature, but that may be due to postmortem wear.

Discussion (type 4 rostral teeth). These specimens comprise a separate morphotype due to the conical crown. The other rostral teeth exhibit some compression of the crown. These specimens are also more robust. It is possible that these specimens

41 Texas Tech University, Joseph A. Schubert, May 2013

represent an adult form of the type 4 rostral tooth.

Family PTYCHOTRIGONIDAE Kriwet et al, 2009

Genus PTYCHOTRYGON Jaekle, 1894

PTYCHOTRYGON AGUJAENSIS McNulty and Slaughter, 1972

Material. Over 400 complete and fragmentary specimens.

Description. The specimens vary from 1mm to 2 mm in mesodistal width (Fig.

7.1). The crown is low and noncuspate. The occlusal surface is marked by numerous, closely spaced transverse ridges. The specimens display a medial lingual depression within a flat lingual flange. Many specimens exhibit foramina on either side of the medial lingual flange. A small labial protuberance extends perpendicular to the root, but does not extend below the root line. The root is bilobate with a distinct nutrient groove.

Discussion. There are two species of Ptychotrygon reported from Cretaceous strata in Texas. Ptychotrygon triangularis is known from Cenomanian through

Maastrichtian strata, and is identified by having fewer, more prominent, and sharper transverse ridges on the crown than P. agujaensis. In addition, the crown of P. triangularis is more elongate and higher than that of P. agujaensis (Welton and Farish,

1993). P. agujaensis has a large number of closely spaced rounded transverse ridges.

The crown is lower and more rounded than any other species of Ptychotrygon (Welton and Farish, 1993).

Ptychotrygon agujaensis was first described from the Aguja Formation

(Campanian) of Brewster County Texas and, according to Welton and Farish (1993,) this

42 Texas Tech University, Joseph A. Schubert, May 2013

species is known only from the type locality. Based on morphological traits alone, the specimens from the Ten Bits Microsite are referable to Ptychotrygon agujaensis, and in view of the fact that the Ten Bits locality is the type locality for the species, their identity seems certain.

PTYCHOTRYGON TRIANGULARIS Reuss, 1844

Material. Over 163 complete and fragmentary specimens.

Description. The specimens vary in maximum mesodistal width from 1 mm to

2.5 mm (Fig. 7.5). These teeth have a high crown and display a roughly triangular occlusal surface separated by 3 distinct transverse ridges. The transverse ridges become more undulating and incomplete towards the labial tip. Many of the specimens have an apical occlusal surface that is abraded to a smooth finish with the transverse ridges only appearing on either side. One transverse ridge appears on the labial face, another transverse ridge separates the labial face from the lingual face, and the third transverse ridge appears on the lingual face. The labial apron is well developed. A lingual uvula is present and extends down to the top of the nutrient groove. There is also a marked depression on the lingual uvula. The nutrient groove is well developed. Two foramina are present on the lingual root face on either side of the uvula. The root is holaulacorizhous.

Discussion. In recent years, the family Ptychotrygonidae has undergone several systematic revisions. Case and Cappetta (1997), Hartstein et al. (1999), Case and

Cappetta (1999), Kriwet (2004) and Kriwet et al. (2009) provide details regarding recent revisions and synonymies.

43 Texas Tech University, Joseph A. Schubert, May 2013

Ptychotrygon triangularis is distinguished from Ptychotrygon agujaensis by the distinct separation, the prominence, and sharpness of the major transverse ridges on the crown (Welton and Farish, 1993). In addition, P. triangularis lacks the numerous corrugated ridges found on P. agujaensis. Ptychotrygon triangularis also displays a higher and more prominent crown than Ptychotrygon agujaensis (Welton and Farish,

1993). Texatrygon hooveri, which is also found at the Ten Bits Microsite, differs from

Ptychotrygon triangularis in the absence of ornamentation on its crown. The morphology of the present specimens is sufficiently distinct from P. agujaensis to indicate that

Ptychotrygon triangularis is also present at the Ten Bits Microsite.

Genus PTYCHOTRYGON Jaekle, 1894

PTYCHOTRYGON AFF. CUSPIDATA Cappetta and Case, 1975

Material. Seven whole and fragmentary specimens.

Description. The specimens vary from 1 mm to 3 mm in mesiodistal width, and display a highly cuspate crown with a single transverse ridge separating the labial and lingual faces (Fig. 7.9). The lingual face is smooth and exhibits a short uvula with a circular depression. From the transverse ridge to the lingual edge there is a small lingual shelf that is slightly concave. The labial face exhibits numerous short vermiculated enameloid ridges that extend from the labial edge half way up the crown face. A slight labial protuberance overhangs the crown foot. The root is holaulacorizhous and displays a strong nutrient groove. No foramina are present on the roots in any of the specimens.

Discussion. These specimens lack the multiple transverse ridges present in many

44 Texas Tech University, Joseph A. Schubert, May 2013

Texas Cretaceous species of Ptychotrygon. They are similar to Texatrygon hooveri in this respect. However, the specimens are excluded from T. hooveri due to the numerous vermiculations on the labial face. The specimens from the Ten Bits Microsite share some features of P. cuspidata, as described by Cappetta and Case (1975) most significantly, the vermiculate enameloid ridges. P. cuspidata also lacks numerous transverse ridges.

However, the Tens Bits specimens have a single pronounced transverse ridge, and lack the strong labial protuberance found in P. cuspidata. They cannot be referred with confidence to this species.

Genus TEXATRYGON Case and Cappetta, 1999

TEXATRYGON HOOVERI McNulty and Slaughter, 1972

Material. Four complete and fragmentary specimens.

Description. The specimens measure 1 to 2 mm in mesiodistal width (Fig. 7.13).

The crowns display a distinct transverse cutting ridge separating the labial and lingual faces. They are generally smooth with one specimen displaying small bumps on the edge of the labial flange. The crowns are triangular, cuspate, and narrow labiolingually. A lingual uvula extends below the crown foot to the top of the nutrient groove. Foramina are obscured but appear to be located on either side of the lingual uvula. Located within the uvula is a slight rounded indentation. The roots are holaulacorizhous.

Discussion. Species of both Texatrygon and Ptychotrygon have been reported from Texas Cretaceous strata. McNulty and Slaughter (1972) described Ptychotrygon hooveri, as having a pyramidal crown that is smooth with faint apical angles. Welton and

45 Texas Tech University, Joseph A. Schubert, May 2013

Farish (1993) illustrated a specimen with a narrow high crown, and sparse ornamentation with localized discontinuous enameloid bumps to the midline labial face. Both Welton and Farish (1993) and McNulty and Slaughter (1972) pointed out that key features of this species are the smooth crown and the lack of corrugations found in other species.

Based on the smoothness of the crowns and the presence on the one specimen of possible enameloid bumps, the teeth from the Ten Bits Microsite closely resemble those of T. hooveri. If correct, this identification would indicate a range extension of T. hooveri from Coniacian into the Campanian.

PTYCHOTRYGON SP.

Material. Seven fragmentary teeth, each with crown and partial root.

Description. The largest specimen is 2 mm in mesodistal width; the smallest is 1 mm in width. Six of the specimens have a strong, single transverse ridge forming a low crown cusp; in the seventh specimen, the ridge is not as pronounced, probably due to wear. The labial apron exhibits a rugose texture not present in other teeth of

Ptychotrygon found at Ten Bits. Five of the specimens display bilateral symmetry. One specimen is asymmetric, with a more expanded, rounded, distal side. The opposing side displays a more typical pointed junction between the lingual and distal faces. This asymmetric specimen may represent a pathological deformity.

Discussion. These specimens appear to represent an unknown species of

Ptychotrygon, sharing the overall triangular crown shape and root morphology. Teeth of

P. agujaensis are very abundant at the Ten Bits Microsite, and are readily differentiated

46 Texas Tech University, Joseph A. Schubert, May 2013

from these specimens in having multiple parallel transverse ridges and a low central cusp.

P. triangularis, is the second most common species found at the site, and is distinguished by its higher cusp and transverse ridges. The rugose labial apron in these specimens distinguishes them from other known species of Ptychotrygon as well.

Family RHOMBODONTIDAE Cappetta, 1987

Genus RHOMBODUS Dames, 1881

RHOMBODUS LEVIS Cappetta and Case, 1975

Material. Fifteen complete and fragmentary specimens.

Description. The specimens vary in size from 2 mm to 5 mm in width (Fig. 7.17).

In occlusal view the specimens have a rhombic to subhexagonal shape. The occlusal surface varies from tooth to tooth with a few teeth displaying an abraded occlusal surface and diminished crown height probably due to feeding wear. Abraded specimens display a stippled to smooth occlusal surface. Crowns are higher on the abraded specimens. The crown faces intersect the occlusal surface at roughly ninety degrees. Labial and lingual faces display a shallow concavity on several of the specimens. These faces are smooth except for a few cracks in the enamel that are likely attributable to postmortem wear and not a reflection of original morphology. The root is bilobate and narrower than the crown.

Specimens that have a complete root structure also display a deep nutrient groove. The roots are triangular in basal view. Foramina are present on the root apron of several specimens.

Discussion. Seven Rhombodus species have been described worldwide. These

47 Texas Tech University, Joseph A. Schubert, May 2013

include R. binkhorsti, R. meridionalis, R. microdon, R. andriesi, R. levis, R. carentonensis, and Rhombodus ibericus. Five of the species are found only in

Maastrichtian strata while two, R. levis and R. carentonensis, are found in the mid to upper Campanian. R. binkhorsti, R. meridionalis, R. microdon, R. andriesi, and R. carentonensis differ from R. levis in having weak to strong vertical folds and wrinkles along the labiolingual faces (Vullo, 2005; Kriwett, Soler-Gijon, and Lopez-Martinez,

2007). R. ibericus differs from R. levis in having polygonal pits with interconnecting ridges on the marginolingual and marginolabial faces. R. ibericus is also smaller in overall size than R. levis (Kriwett, Soler-Gijon, and Lopez-Martinez, 2007).

The diagnostic features of R. levis include its rhomboidal to subhexagonal crown in occlusal view, and enamel that is relatively thick and smooth (Case and Schwimmer,

1988). The lingual bulge found in R. levis is reduced or lacking in the present specimens

(Vullo, 2005; Kriwett, Soler-Gijon, and Lopez-Martinez, 2007). The thick enamel, small size, foramina on the tooth apron and overall rhombic shape help distinguish R. levis from other ray teeth of Campanian age (Case and Schwimmer, 1988).

The Ten Bits Microsite specimens have the characteristics found in Rhombodus levis, notably the smooth labiolingual faces, foramina and rhombic shape. If these specimens are indeed R. levis, it would represent their first reported occurrence in the Big

Bend region.

48 Texas Tech University, Joseph A. Schubert, May 2013

Family MYLIOBATIDAE Bonaparte, 1838

Genus BRACHYRHYZODUS Romer, 1942

BRACHYRHYZODUS WICHITAENSIS Romer, 1942

Material. Eight complete specimens.

Description. The specimens are approximately 4 mm in labiolingual length and 8 mm in mesodistal width, and have an irregular hexagonal shape in occlusal view (Fig.

7.21). The surface of the crown is slightly textured with low relief and displays random score lines. In basal view, the crown extends beyond the perimeter of the root. Of the eight specimens, three display dual nutrient grooves while the other five display only a single, wide groove. The root is approximately half the height of the crown. In lingual view, there are several plications that are widely spaced and visible near the crown foot.

On one specimen several foramina are present.

Discussion. There are two myliobatids previously reported from Texas

Cretaceous strata. One of these is Brachyrhizodus wichitaensis. This particular species has been reported from Campanian strata in the Big Bend area of Texas (Welton and

Farish, 1993). It has teeth with a thicker crown and fewer basal nutrient grooves than other myliobatid rays (Welton and Farish, 1993). Another myliobatid is represented by an unnamed species. This unnamed species is distinguished by having a narrow crown and numerous nutrient grooves on the basal surface; its crown is thin and unornamented

(Welton and Farish, 1993).

The rhinobatoid Pseudohypolophus has teeth that resemble those of

Brachyrhizodus. However Pseudohypolophus is strictly bilobate while those in

49 Texas Tech University, Joseph A. Schubert, May 2013

Brachyrhizodus can be multi-lobed (Case and Schwimmer, 1988). Teeth of

Pseudohypolophus are abundant in Cenomanian strata (Welton and Farish, 1993), but also are known from the Campanian (Case and Schimmer, 1988).

The teeth found at the Ten Bits Microsite strongly resemble those of

Brachyrhizodus. The specimens display a thick crown, a single or dual nutrient groove in the root that results in a bilobate to multilobate basal attachment surface such as found in

B. wichitaensis.

Genus IGDABATIS Cappetta, 1972

IGDABATIS INDICUS ?

Material. A single incomplete tooth that is missing part of the mesial side. The specimen is mildly abraded.

Description. The half specimen measures approximately 15 mm mesodistally and

7 mm labiolingually (Fig. 7.24). The crown is thick, with low relief, and slightly convex viewed from the lingual or labial side. The crown thickens from the end toward the middle of the tooth. The occlusal surface of the crown displays a stippled and pitted pattern. The root is polyaulacorhizous with five, possibly six nutrient grooves. One groove is obscured with matrix. There are six lobes, and numerous foramina lingually near the crown foot. Foramina are also present on the labial face near the crown foot. The crown extends beyond the perimeter of the root in basal view.

Discussion. Igdabatis indicus has not previously been reported from North

America. Cappetta (1972) described the type specimen Igdabatis sigmodon based on a

50 Texas Tech University, Joseph A. Schubert, May 2013

tooth found in Niger, West Africa (Kriwet et al., 2007). This species was described as

having teeth with “uvulae like” structures in the lingual bulge above every root groove

(Soler-Gijon and Lopez Martinez, 1998). In addition, I. sigmodon exhibits a sigmoidal

curvature in its median teeth (Soler-Gijon and Lopez Martinez, 1998).

Prasad and Cappetta (1993) described another Igdabatis species from the

Maastrichtian Marepalli and Asifabad intertrappean beds of India (Kriwet et al., 2007),

Igdabatis indicus. Specimens later recovered in Spain were also assigned to Igdabatis

indicus based on having a crown that varies in thickness from medial to lateral sides in

lingual view, a pitted ornamented occlusal surface, lateral and lingual faces that have

folds, and a multi-lobed polyaulacorhizous root (Soler-Gijon and Lopez Martinez, 1998).

These specimens do not display the characteristic sigmoidal contour of I. sigmodon nor

do they display the uvula like structure found above the root grooves (Soler-Gijon and

Lopez Martinez, 1998).

The single tooth recovered from the Ten Bits Microsite shares more

characteristics with Igdabatis indicus than with unidentified Myliobatidae teeth

previously reported in the Cretaceous of Texas (Welton and Farish, 1993) or with I.

sigmodon. This tooth has the characteristic pitted occlusal surface, thinning of the crown

towards the lateral parts of the tooth and the multi-lobed polyaulacorhizous root. The fact that only one fragmentary specimen has been found thus far makes it difficult to confidently identify this as Igdabatis indicus. If the identification is correct, this would represent its first reported occurrence in North America.

51 Texas Tech University, Joseph A. Schubert, May 2013

Order MYLIOBATIFORMES Capagno, 1973

INCERTAE SEDIS

Material. Three complete specimens.

Description. These teeth measure approximately 2 mm in mesiodistal width and 1 mm labiolingually (Fig. 8.1). The crowns are low and smooth. There are striations on the occlusal surface that are probably due to dental wear. The crowns display enameloid bumps on the rounded lingual edge of the occlusal surface. The labial occlusal edge ends rise to form a sharp transverse ridge. The lingual face is concave with numerous foramina. The labial face is convex; this results in a bean-shaped occlusal surface. The root is holaulacorizhous and strongly lobate. The labial root face terminates in line with the crown while the lingual root face extends past the crown. The root displays a well- defined nutrient groove.

Discussion. The identity of these specimens is uncertain. No similar specimens have been described elsewhere.

Class CHONDRICHTHYES Huxley 1880

PLACOID SCALES

Materials. There are 23 complete and fragmentary placoid scales.

MORPHOTYPE A

Description (type A placoid scale). The specimens are approximately 1 mm to 2 mm along the largest dimension (Fig. 9.24). The external face is roughly circular with a

52 Texas Tech University, Joseph A. Schubert, May 2013

pronounced protuberance in the center of the scale. One side of the protuberance displays concavities along its perimeter while the remaining perimeter is smooth. This gives the protuberance the appearance of a webbed foot. The basal face is unadorned.

MORPHOTYPE B

Description (type B placoid scale). Type B placoid scales are 1 mm to 3 mm along the greatest dimension (Fig. 9.25). The shape varies from specimen to specimen but is roughly circular. There is a protuberance in the center of the external face but unlike the type A scale, this protuberance is round. The basal surface is unadorned.

MORPHOTYPE C

Desciption (type C placoid scale). The Type C placoid scale differs from the Type

A and Type B in overall shape (Fig. 9.26). The scales are 1 mm to 3 mm along the greatest dimension. These specimens have one or more flat sides that form a right angle.

The external face has a protuberance that is smooth and rounded like the Type B scale.

The basal face in unadorned.

MORPHOTYPE D

Description (type D placoid scale). The Type D scales are 1 mm to 6 mm long at the greatest dimension (Fig. 9.27). These scales have a overall disk shape. The largest displays a central dot that is darker in color than the rest of the scale. The other specimens have a central region that is abraded and it is difficult to determine if there is a central dot.

53 Texas Tech University, Joseph A. Schubert, May 2013

The basal surface is unadorned.

Discussion. It is possible that Type B and Type C represent the same type of scale and the overall shape is simply the function of how closely they were arranged in life.

The Type A and Type D are sufficiently different that they warrant separate designation.

DERMAL DENTICLES

Material. The 69 complete and fragmentary denticles.

Description. The denticles vary from less than 1 mm to 3 mm at the widest dimension. Many of the denticles display a wide, somewhat ovoid root in external view.

The perimeter is not perfectly ovoid but has indentations along the edges in many example (Fig. 9.28). The spines are robust and posteriorly inclined. The spine sits anteriorly on the root, leaving what may be described as a posterior root apron. Many display a flattened anterior face while others retain a more conical appearance. The spine foot is smooth to scalloped with small enameloid ridges. The ridges extend apically to about three quarters the length of the crown on some.

Discussion. The dermal denticles found at the Ten Bits Microsite represent a diverse assemblage, and probably represent multiple taxa. The denticles look very much like rostral teeth and it can be hard to differentiate the two since they are morphologically very similar.

54 Texas Tech University, Joseph A. Schubert, May 2013

Family TRIGONODONTOIDAE Weiler, 1929

Genus STEPHANODUS Zittel, 1883

STEPHANODUS ?

Material. 22 whole and fragmentary specimens.

Description. The specimens are flattened pharyngeal teeth. Nine of the specimens display a strongly hooked crown. (Fig. 8.5). The remaining ten specimens display only a slight hook. The teeth display striations on the enamel probably due to poor preservation. There are no roots.

Discussion. Specimens similar to those found at the Ten Bits Microsite have been variously assigned to Pycnodontidae (Applegate, 1970), Sclerodontidae (Case, 1982) or more recently to Trigonodontodae (Zittel, 1932; Case, 1982; Case and Schwimmer,

1988). The specimens found at the Ten Bits Microsite are probably referable to

Stephanodus sp. based on the similarity to those described by Case and Schwimmer

(1988).

Family ALBULIDAE Cope, 1871

Genus ALBULA Bloch and Schneider, 1801

ALBULA sp.

Material. Approximately 385 complete and fragmentary teeth.

Description. These teeth range from 1 mm to 2 mm in the greatest diameter (Fig.

8.6). Many specimens are circular to near circular in occlusal aspect. The pattern in which were the teeth were likely packed on the tooth plate, and the resulting compression

55 Texas Tech University, Joseph A. Schubert, May 2013

probably results in slight variability in shape. The specimens display a stepped annular

ornamentation. This varies from one to three concentric steps on the occlusal surface. The

teeth are flat in basal aspect. Some display a completely smooth basal surface while other

display a weak ornamentation, possibly from resulting abrasion postmortem. The

specimens lack roots.

Discussion. Case and Schwimmer (1988) described specimens from the

Blufftown Formation of Georgia that display triple rows of annular ornamentation, have a

circular occlusal outline, and lack distinctive roots. The Ten Bits specimens clearly

pertain to Albula, and these teeth display the same detailed features found in those

identified by Case and Schwimmer (1988) from the Blufftown.

Family PHYLLODONTIDAE Sauvage, 1875

Genus PARALBULA Blake, 1940

PARALBULA CASEI Estes, 1969

Material. Approximately 130 complete and fragmentary teeth and tooth caps.

Description. These specimens are small, 1 mm to 2 mm in their greatest diameter

(Fig. 8.8). Most of the teeth are circular to nearly circular in occlusal outline. The occlusal surface displays a rugose texture radiating from the center of the tooth outward to the margins. Some of the specimens display a faint to distinct circular sculpturing at the apex. The teeth vary from hemispherical to nearly square in lateral outline. The base is circular, displays a central depression, and not a foramen due to infilling of matrix; it is not clear that all specimens have a basal foramen, however some specimens display a

56 Texas Tech University, Joseph A. Schubert, May 2013

clear central foramen.

Discussion. Paralbula marylandica was described by Blake (1940) based on a specimen found in the Aquia Formation of Maryland. The specimen was described as hemispherical with a basilar foramen, and an occlusal surface that is smooth or sparsely punctate (Estes 1969). Paralbula stromeri is a Late Eocene bonefish found in the Qasrel-

Sagha Formation of Egypt, and described as sharing similarities with P. marylandica

(Estes, 1969).

Paralbula salvani is found in the Paleocene strata of Morocco. The single incomplete specimen figured by Arambourg (1952) is described as sharing similarities with P. casei, including a radiate but less distinct sculpture pattern. More complete specimens are needed to resolve the relationship between P. salvani and P. casei.

Paralbula casei is distinguished from other species of Paralbula by its well developed radiate surface ornamentation, thin enamel layer and bases with well developed pulp cavities (Estes 1969). Case and Schwimmer (1988) illustrated specimens from the Blufftown Formation of Georgia as similarly hemispherical to square in lateral outline. The specimens are circular in occlusal view, slightly concave in basal aspect, with a surface ornamentation of faint rugosities radiating from the center to the margins

(Case and Schwimmer 1988).

The specimens from the Ten Bits Microsite share many of the attributes of P. casei. These include the surface ornamentation on the occlusal surface, hemispherical to square lateral outlines, basal concavity and foramen. The stratigraphic range of Paralbula casei is also compatible with the Campanian age of the Ten Bits Microsite.

57 Texas Tech University, Joseph A. Schubert, May 2013

Family SEMIONOTIDAE Woodward 1890

Genus LEPIDOTES Agassiz 1832

LEPIDOTES SP.

Material. Approximately 106 complete and fragmentary teeth.

Description. The teeth are 1 mm to 2 mm in greatest width and display various shapes in occlusal view (Fig. 9.20). Most are ovoid to circular, but some teeth are polygonal and straight sided with one straight edge or more, possibly due to close packing in life. Many of the specimens display a conical profile in lateral view with the widest dimension at the occlusal surface, narrowing to the base of the root. The occlusal surface is typically flat to slightly rounded and is unadorned, although there is some wear evident on the surface of many specimens. The basal face displays a pulp cavity in most of the specimens.

Discussion. The specimens collected from the Ten Bits Microsite appear to represent a pycnodontiform fish, but teeth with this simple design are difficult to identify with certainty.

OSTEICHTHYES Huxley, 1880

OSTEICHTHYES INDETERMINATE

Teeth belonging to four different species of fishes cannot at present be assigned to known taxa. They are described below as indeterminate species A, B, C, and D. Three of the species (A, B, and C) probably represent osteichthyan fishes, but one (D) may represent an elasmobranch.

58 Texas Tech University, Joseph A. Schubert, May 2013

INDETERMINATE SPECIES A

Material. 11 complete teeth.

Description. The specimens vary from 1.5 to 5 mm mesiodistally and 1 to 2 mm labiolingually (Fig. 8.10). The occlusal surface is smooth with a few fine striations, although these may be due to postmortem wear. In many of the specimens, the crown is somewhat heart-shaped with the basal attachment surface extending beyond the crown perimeter. In profile, the crown is strongly inclined lingually at an angle of approximately

10 to 20 degrees. The labial face is concave and the lingual face is convex.

Discussion. These specimens may pertain to a previously unknown osteichthyan species. The “root” or basal attachment surface does not have the morphology normally found in elasmobranch teeth.

INDETERMINATE SPECIES B

Material. Eight complete and fragmentary teeth.

Description. The specimens are 1 mm to 3.5 mm in mesiodistal width and 1.5 to

3 mm from apex to base of root (Fig. 8.14). The crown is roughly triangular with parallel labial and lingual faces. The lingual face is shorter than the labial face in height and gives the apex of the crown a faceted appearance. The occlusal surface is 1 mm in labiolingual width. Two occlusal faces are separated by a labiolingual ridge. On some of the specimens, the two occlusal faces show a slight concavity. The labial and lingual faces are smooth. The ‘root’ forms an obtuse angle to the crown. On one specimen this angle is approximately 110 degrees and gives the specimen the appearance of a hinge. There are

59 Texas Tech University, Joseph A. Schubert, May 2013

no foramina, nutrient grooves, or lobes associated with the root.

Discussion. The specimens from the Ten Bits Microsite do not exhibit traits

associated with elasmobranch or holocephalian teeth. It is more likely that the specimens

pertain to an unknown osteichthyan.

INDETERMINATE SPECIES C

Material. One complete tooth.

Description. The specimen appears to be a tooth crown and is 4 mm in its widest

dimension (Fig. 8.18). The outline is ovoid in occlusal view. The crown is flat and has

four pronounced grooves in the enamel surface. The grooves extend both transverse and

parallel to the long dimension of the crown, and may be subdued as a result of wear. In

profile view, one side of the crown is taller than the opposite side, 1.5 mm and 1 mm

respectively. The basal surface is smooth with numerous fracture lines, and there does

not appear to be a root.

Discussion. This single specimen may represent a vomerine tooth from an

unknown pyconodont.

INDETERMINATE SPECIES D

Material. One complete and one partial tooth.

Description. The specimens are 1 mm to 2.5 mm in mesiodistal width (Fig. 8.20).

The roots are bilobate with a very prominent central notch on the lingual root face.

However, the root lacks a nutrient groove and a central foramen. The root extends beyond

60 Texas Tech University, Joseph A. Schubert, May 2013

the crown. The crown is short and narrows toward the apex to form a cutting edge. The

crown merges into a well-defined lingual uvula resulting in a ninety degree angle

between root and crown. Viewed labially, the crown displays a v-shaped notch in the

center of the face with a slightly inflated portion of crown to either side.

Discussion. These unusual teeth may represent an unknown species of

elasomobranch. Because there is more than one tooth that shares this morphology it is

unlikely that that they represent an individual pathological deformity. Both occlusal and

labial surfaces of the crowns appear incomplete and fractured. If so, the v-shaped notch

may actually be the exposed pulp cavity. However, it seems unlikely that two teeth would

have fractured in the same way.

OSTEICHTHYES Huxley, 1880

OSTEICHTHYES INDETERMINATE

CENTRA

Material. There are approximately 462 complete and fragmentary teleost centra.

Desciption. The specimens range from 1 mm to over 10 mm in diameter. (Figs.

9.22 and 9.23). The majority of the specimens are compressed anteroposteriorly; the centrum diameter is greater than its thickness. There are five specimens that are instead anterposteriorly elongate, the centrum diameter is less than its thickness. The centra are all highly worn. The parapophyseal articular pits, neural arch articular pits, fossa and radial calcifications are poorly preserved. The anterior and posterior faces of the centra display concentric calcareous rings with a central notochordinal pit. The articulation

61 Texas Tech University, Joseph A. Schubert, May 2013

surfaces of the centra are circular to ovoid in shape.

There are three fragmentary specimens that display a unique morphology compared to the other specimens. One specimen is greater than 10 mm in diameter. This specimen is anteroposteriorly compressed, with well defined paired radial calcareous fibers that extend from the anterior to posterior face. The fibers are separated by fosse that are roughly equal in width to the paired fibers. The second fragmentary centrum is elongate anteroposteriorly. The lateral fosse are separated by a single radial calcareous fiber that separates on the anterior and posterior ends into four fibers and three smaller fossae. The third fragmentary centrum displays neural arch articular pits and foramina.

The ventral side of the centrum has the paraophyseal articular pits with associated foramina in either pit. The fourth centrum is worn but lacks the distinctive morphology of the other three. This specimen displays concentric calcareous rings on the anterior and posterior faces. Articular pits are poorly preserved. The articulation faces of the specimen are rectangular in form, and is the only one to display this shape.

Discussion. The identification of isolated teleost centra is problematic (see

Brinkman and Neuman, 2002). In this case identification is particularly uncertain due to the amount of wear on the centra.

62 Texas Tech University, Joseph A. Schubert, May 2013

TESTUDINES Linnaeus, 1758

TESTUDINES INDETERMINATE

Fragments of four varieties of turtle shell are described below as morphotypes 1,

2, 3, and 4. Due to their poor preservation, none of the fragments can be assigned with confidence to specific taxa.

Material. Four fragmentary and abraded pieces of turtle carapace and plastron.

The shell is unadorned.

MORPHOTYPE 1

Description (type 1 shell). The specimen is 10 mm by 11 mm and is roughly square. The outer surface of the shell displays five ridges with a series of pits aligned in a row between the ridges. The ridge and pit morphology is very ordered in this specimen and is structured similar to a honeycomb (Fig. 9.12). The internal face of the shell is unadorned.

MORPHOTYPE 2

Description (type 2 shell). This specimen is 9 mm by 15 mm. The external face of this specimen is adorned with ridges and elongated troughs (Fig. 9.13). Unlike the morphotype 1 shell fragment, there is no obvious order to the ridges and troughs. The internal surface of the shell is unadorned.

MORPHOTYPE 3

Description (type 3 shell). This specimen is 9 mm by 9 mm and displays a

63 Texas Tech University, Joseph A. Schubert, May 2013

trapezoidal shape. The external surface exhibits two patterns. The top portion displays

four plates that are separated by thin grooves. The bottom portion also displays numerous

individual plates, but unlike the upper these do not appear to be separated by grooves

(Fig. 9.14). Along one side of the specimen are very fine parallel lines that extend across

the surface. The lines appear to extend underneath the individual plates. The internal

surface is unadorned.

MORPHOTYPE 4

Description (type 4 shell). This specimen is 25 mm by 22 mm. Both surfaces of

the shell fragment are smooth and unadorned.

Discussion. Turtle shell morphotypes 1, 2 and 3 represent fragments from the

carapace of different individuals or different parts of the shell. The morphotype 4

specimen represents a fragment from a turtle plastron. The distinct external morphology

exhibited by each specimen suggests that the fragments pertain to more than one species

of turtle.

MOSASAURIDAE Gervais, 1853

MOSASAURIDAE INDETERMINATE

Material. One partial verterbra.

Description. The vertebrae is procoelous and is split in half down the anteroposterior axis preserving the left lateral half of the vertebrae (Fig. 9.15). The

64 Texas Tech University, Joseph A. Schubert, May 2013

specimen is 25 mm in length anterposteriorly. The specimen displays an attachment point for a caudal rib and partial attachment point for the hemal arch and the neural arch.

Discussion. Russel (1967) discusses various morphologies exhibited by mosasaur vertebrae, but due, the abraded nature of the Ten Bit’s specimen, no conclusions can be made for this specimen.

INDETERMINATE CROCODYLIAN TEETH

Material. Five fragmentary specimens.

Description. Four of the specimens are conical fragments from the upper portion of the crown apex (Fig. 9.18). The four specimens are 2 mm to 3.5 mm in width. One specimen appears to be from the lower portion of the tooth and is lacking the apex. It has a width of 4 mm. All the specimens display varying degrees of roughly parallel striations extending from the base toward the apex of the tooth.

REPTILIA INDETERMINATE

Material. Two fragmentary caudal vertebrae.

Description. The vertebrae are 1 mm to 2 mm wide. The centra are elongate anteroposteriorly and fractured perpendicular to their long axis. The anterior or posterior face on both specimens is convex. The parapophyseal articular pits, neural arch articular pits, and fossae are poorly preserved (Fig. 9.19).

Discussion. These specimens display characteristics that are not associated with either osteichthyan or elasmobranch vertebrae. The convex articulation face of the

65 Texas Tech University, Joseph A. Schubert, May 2013

anterior or posterior face suggests that these likely represent an indeterminate reptile species.

COPROLITES

Material. Approximately 75 whole and broken fragments of coprolites.

Description. The specimens range up to 8 mm in length and 4 mm in width, and are mostly cylindrical in shape with a few exhibiting tapered ends.

Discussion. The specimens represent coprolites from various unknown aquatic organisms. None exhibit the spiral form typical of chondrichthyan coprolites, and so presumably these may pertain instead to bony fishes. There are no obvious fragments of scales, bones, or teeth within the coprolites.

66 Texas Tech University, Joseph A. Schubert, May 2013

Figure 5 - Oral tooth of Hybodus sp. Agassiz 1837, in lingual (1), and labial views (2); oral tooth of Lonchidion selachos Estes 1964, in profile (3), lingual (4), labial (5), and occlusal views (6); oral tooth of Cantioscyllium aff. meyeri Case and Cappetta 1997, in occlusal (7), and labial views (8); oral tooth of Chiloscyllium aff. greeni Cappetta 1973, in labial (9), lingual (10), and profile views (11); oral tooth of Cretorectolobus olsoni Case 1978, in occlusal (12), labial (13), lingual (14), and profile views (15); oral tooth of Squatina hassei Leriche 1929, in labial (16), lingual (17), and occlusal views (18); oral tooth of Cretalamna appendiculata Agassiz 1843, in lingual (19), and labial views (20); oral tooth of Squalicorax kaupi Agassiz 1843, in lingual (21), and labial views (22); pathologically deformed oral tooth of Squalicorax kaupi Agassiz 1843, in lingual (23), labial (24), and profile views (25).

67 Texas Tech University, Joseph A. Schubert, May 2013

68 Texas Tech University, Joseph A. Schubert, May 2013

Figure 6 - Oral tooth of Squalicorax aff. pristodontus Agassiz 1843, in lingual (1), labial (2), and profile views (3); anterior oral tooth of Scapanorhynchus texanus Roemer, 1852, in lingual (4), labial (5), and profile views (6); anterior oral tooth of S texanus, in lingual (7), labial (8), and profile views (9); oral tooth of Rhinobatos casieri Herman 1977, in lingual (10), labial (11), profile (12), and occlusal views (13); oral tooth of Protoplatyrhina renae Case 1978, in lingual (14), labial (15), profile (16), and occlusal views (17); rostral tooth of Ischyrhiza cf. avonicola Estes 1964, in anterior (18), posterior (19), and profile views (20); oral tooth of Ischyrhiza mira Leidy 1856, in lingual (22), labial (23) and profile views (24); rostral tooth of I. mira, in dorsal (25), and anterior views (26).

69 Texas Tech University, Joseph A. Schubert, May 2013

70 Texas Tech University, Joseph A. Schubert, May 2013

Firgure 7 – Oral tooth of Ptychotrygon agujaensis McNulty and Slaughter 1972, in lingual (1), in labial (2), in profile (3), in occlusal (4); oral tooth of Ptychotrygon triangularis Reuss 1844, in lingual (5), in labial (6), in profile (7), in occlusal (8); oral tooth of Ptychotrygon aff cuspidate Cappetta and Case 1975, in lingual (9), in labial (10), in profile (11), in occlusal (12); oral tooth Texatrygon hooveri McNulty and Slaughter 1972, in lingual (13), in labial (14), in profile (15) in occlusal (16); oral tooth Rhombodus levis Case and Cappetta 1975, in lingual (17), in labial (18), in profile (19), in occlusal (20); oral tooth Brachyrhizodus wichitaensis Romer 1942, in lingual (21), in basal (22), in occlusal (23); oral tooth Igdabatis aff indicus Cappetta 1975, in labial (24), in basal (25), in occlusal (26).

71 Texas Tech University, Joseph A. Schubert, May 2013

72 Texas Tech University, Joseph A. Schubert, May 2013

Figure 8 – oral tooth Myliobatiformes Capagno 1973, in lingual (1), in labial (2), in profile (3), in occlusal (4); vomerine tooth Stephanodus ? in profile (5); oral tooth Albula sp. in profile (6), in occlusal (7); oral tooth Paralbula casei Estes 1969, in profile (8), in occlusal (9); oral teeth Osteichthyes Indeterminate Species A, in lingual (10), in labial (11), in profile (12), in occlusal (13); Indeterminate Species B, in lingual (14), in labial (15), in profile (16), in occlusal (17); Indeterminate Species C, in profile (18), in occlusal (19); Indeterminate Species D, in labial (20), in lingual (21).

73 Texas Tech University, Joseph A. Schubert, May 2013

74 Texas Tech University, Joseph A. Schubert, May 2013

Figure 9 – rostral teeth morphotype 1, in anterior (1), in occlusal (2); morphotype 2, in anterior (3), in occlusal (4), in profile (5); morphotype 3, in anterior (6), in occlusal (7), in profile (8); morphotype 4, in anterior (9), in occlusal (10), in profile (11); Testudines Indeterminate shell morphotype 1, (12); morphotype 2, (13); morphotype 3, (14); Mosasaur vertebrae, (15), (16), (17); Crocodylia Indeterminate, (18); Reptilia Indeterminate, (19); Oral tooth Lepidotes sp Agassiz 1832, in profile (20), in occlusal (21); fish vertebrae (22), (23); placoid scales in occlusal, type A, (24), type B, (25); type C, (26); type D, (27); dermal denticle in occlusal (28).

75 Texas Tech University, Joseph A. Schubert, May 2013

76 Texas Tech University, Joseph A. Schubert, May 2013

CHAPTER 3

DISCUSSION

The shark and bony fish fauna collected at the Ten Bits Microsite represents the southernmost marine vertebrate fauna of middle Campanian age thus far known in North

America. The bone-bearing interval at the Ten Bits Microsite is unusually fossiliferous, yielding about 5000 specimens in the small amount of matrix (c. 50 kg) processed by screen-washing for purposes of this research. The fauna preserved here is a diverse one, with about 30 species identified thus far, and others no doubt represented among the indeterminate specimens. The relative abundance of species present in the Ten Bits fauna is discussed below, and the fauna is compared with those of similar age known from farther north in the Western Interior, and from farther east on the Gulf and Atlantic

Coastal Plain.

The Ten Bits Fauna

The fauna collected at the Ten Bits Microsite exhibits a mixture of marine species, with some that are known or believed to have inhabited brackish or freshwater environments. The most common teeth, denticles, and spines belong to species of sharks, rays, and sawfishes typical of coastal marine deposits elsewhere (e.g., Scapanorhynchus,

Ptychotrygon, Ischyrhiza). These elements also tend to be well preserved, suggesting that they have not been transported far from the environments the animals actually inhabited. In contrast, some of the shark species found in the Ten Bits fauna (e.g.,

Hybodus, Lissodus) are known elsewhere from sites that are thought to record brackish to

77 Texas Tech University, Joseph A. Schubert, May 2013 freshwater habitats (Welton and Farish, 1993), but these species are represented at Ten

Bits by only a few specimens, suggesting that they were either rare in the environment there, or preserved outside their usual habitat. Similarly, teeth, bones, and shell fragments of crocodylians and turtles typical of freshwater deposits, are less abundant at the site. These tend to be broken and abraded, suggesting that the elements were transported some distance prior to burial. The relative abundance and varied preservation of species represented at the Ten Bits Microsite indicates that it represents a marginal marine or estuarine environment. This interpretation is consistent with sedimentary facies analysis of the Rattlesnake Mountain sandstone member of the Aguja, and its marine invertebrate fauna (Lehman, 1985; Macon, 1994).

The sample from Ten Bits Microsite yielded roughly comparable numbers of identifiable chondrichthyan specimens (54%) compared to osteichthyan fish specimens

(46%). A total of 2236 identifiable chondrichthyan specimens were recovered, representing 23 species (Fig. 13). The most abundant species represented is

Scapanorhynchus texanus (800 specimens, 36% of chondrichthyan material).

Scapanorhynchus was probably related to the modern deepwater goblin shark,

Mitsukurina owstoni, which is known to inhabit oceanic waters at depths of up to 500 meters (Welton and Farish 1993).

The second most abundant species represented is the sclerorhynchid Ptychotrygon agujaenisis (688 specimens, 30% of chondrichthyan material). The Ten Bits Microsite yielded the type specimens of P. agujaensis (McNulty and Slaughter, 1972), and several additional species pertaining to this genus are reported here. Ptychotrygon was probably

78 Texas Tech University, Joseph A. Schubert, May 2013 related to modern sawfishes and shared the same ecological niche in warm, shallow marine environments, occasionally also inhabiting brackish or fresh water (Welton and

Farish, 1993). The third most common species found at Ten Bits Microsite is also a sclerorhynchid, Ischyrhiza mira (230 palatal teeth, 11 rostral teeth; 11% of chondrichthyan material). Many of the remaining species represent bottom-dwelling rhinobatid, rajid, and myliobatid rays, and are known from fewer specimens, each comprising less than 1% of the chondrichthyan material.

The lamniform sharks Squalicorax and Cretolamna are found in lower numbers

(43 specimens, 2%) and represent species probably related to modern mackerel sharks found worldwide in coastal and open deep water environments, in tropical, warm temperate, and temperate waters (Welton and Farish, 1993).

Osteichthyan fishes are represented in the Ten Bits fauna by fewer species,

(Fig. 14) but are abundant in numbers of specimens (1892 identifiable specimens). The three common species are Paralbula casei (901 specimens, 63% of osteichthyan specimens), Albula sp. (392 specimens, 27%), and Lepidotes (108 specimens, 7%). Both

Paralbula and Albula are thought to be related to modern bonefish and ladyfish, and have dentition adapted for crushing small molluscs.

Ten Bits and Terlingua Microsites Compared

A diverse aquatic micro-vertebrate assemblage was reported by Rowe et al.

(1992) from the upper shale member of the Aguja Formation on Terlingua Ranch, 20 km southeast of the Ten Bits Microsite. The Terlingua Microsite is slightly higher

79 Texas Tech University, Joseph A. Schubert, May 2013 stratigraphically, and preserves a much greater number of fresh water species, as well as terrestrial reptiles and mammals that are entirely absent in the Ten Bits fauna. As a result, differences between the Ten Bits and Terlingua faunas may be due in part to slightly different age, and to sampling different environments. Even so, the two sites share many of the same species. Both Hybodus and Lonchiodon are represented by hundreds of specimens in the Terlingua fauna, but only a few specimens have been found at Ten Bits. In contrast, Scapanorhynchus is represented by hundreds of specimens at

Ten Bits, but only a few broken teeth were recovered at the Terlingua Microsite. Such differences are almost certainly due to accumulation in a more open marine setting at Ten

Bits, as opposed to a brackish or freshwater environment at the Terlingua Microsite. Two schlerorhynchids, Onchopristis dunklei and Squatirhina americana, occur in the

Terlingua fauna that have not been found at Ten Bits, and the unidentified species of

Ptychotrygon found there does not appear to represent any of the five species represented at Ten Bits. The latter differences are less likely due to contrasting paleoenvironment, and could be due to stratigraphic position (e.g., immigration events or evolutionary changes).

Paleobiogeography of the Western Interior Seaway

Within the marine deposits that accumulated in the Western Interior Seaway, several latitudinal paleobiogeographic provinces have been recognized, based primarily on marine molluscs (cephalopods, gastropods and bivalves; (Sohl, 1967; Jeletzky, 1971;

Kauffman, 1973; Scott, 1977). Kauffman (1984) and Coates et al. (1984) also recognized

80 Texas Tech University, Joseph A. Schubert, May 2013 multiple biotic zones in the Western Interior based on modern biogeographic concepts.

The northernmost zone is designated the Northern Interior Subprovince and characterized by a "cool temperate" biota, from the Arctic Ocean southward through the western provinces of Canada (Fig. 10). From there to Wyoming and South Dakota southward to

Colorado and Kansas, a Central Interior Subprovince is recognized, characterized by

"mild temperate" marine biota. Areas where these provinces overlap comprise the North

American Endemic Center of Kauffman (1984). South of this line, a Southern Interior

Subprovince existed in New Mexico and Texas, characterized by a "warm temperate" biota. The Gulf and Atlantic Coast Subprovince was characterized by "warm subtropical" marine biota, including large echinoids, rudistid bivalves, specialized ammonites and planktonic foraminifera typical of the equatorial Tethyan realm (Kauffman, 1984).

Nicholls and Russell (1990) also recognized differences in the marine vertebrate faunas of these regions. The Northern Interior marine vertebrate fauna was characterized by abundant plesiosaurs, dominance of the mosasaur Platecarpus and bird Hesperornis, rarity of sea turtles, and generally low diversity in all groups. In contrast, the Gulf and

Atlantic Coast vertebrate fauna was characterized by abundant sea turtles, dominance of the mosasaur Clidastes and bird Ichthyornis, and high diversity of chondrichthyans and osteichthyans.

The Ten Bits Microsite provides a sample of the marine vertebrate fauna that existed in the boundary region between the Southern Interior and Gulf/Atlantic Coast subprovinces. The high diversity of sharks and bony fishes in the Ten Bits fauna accords with the high diversity typical of other "southern" marine faunas of this age (Nicholls and

81 Texas Tech University, Joseph A. Schubert, May 2013

Russell, 1990). It is useful to compare the species represented, and their relative abundance in the Ten Bits fauna with those of similar age (Middle to Late Campanian) found farther north, and farther east, to see which shark and fish species may also occur in the adjoining provinces (Fig. 11 and 12).

Comparison with the Judith River Fauna

Case (1978) described the elasmobranch fauna of the Campanian Judith River

Formation in northern Montana. The deposits of the Judith River Formation are within the Northern Interior Subprovince of Kauffman (1984), and reflect coastal estuarine habitats similar to those in the Aguja Formation. The two faunas share many of the same species. Case's (1978) study does not provide a total number of specimens collected, nor is the relative abundance of each species given. According to Case (1978), however, the five most abundant species represented are Protoplatyrhina renae, Plicatilamna arcuata,

Cretorectolobus olsoni, Hypotodus grandis and Myledaphus bipartitis. Three of these species are not present in the Ten Bits fauna (P. arcuata, H. grandis, and M. bipartitis).

The other two, Protoplatyrhina renae and Cretorectolobus olsoni, are found only in small numbers at the Ten Bits Microsite. It is particularly significant also that Myledaphus bipartitis has not been found at the Ten Bits Microsite. The teeth of this ray are very large, distinctive, and do not require screen-washing techniques to recover. Not a single example has been found at the Ten Bits Microsite, or elsewhere in the Aguja Formation

(e.g., Lehman, 1997; Rowe et al., 1992).

82 Texas Tech University, Joseph A. Schubert, May 2013

The sawfish Ischyrhiza mira is uncommon in the Judith River, while it is very common in the Ten Bits fauna. Squalicorax kaupi and Ischyrhiza avonicola are not abundant at either site. Scapanorhynchus texanus is the most common chrondrichthyan at the Ten Bits Microsite, but is not reported to occur in the Judith River fauna.

Comparison with the Pictured Cliffs Fauna

Armstrong-Ziegler (1978, 1980) described chondrichthyan and osteichthyan fishes from marginal marine deposits in the Upper Campanian Fruitland Formation in northern New Mexico. Williamson and Lucas (1992) found additional fish species in marine deposits of the underlying and intertonguing Pictured Cliffs Sandstone.

Collectively these provide a sample of Late Campanian coastal fishes from the Southern

Interior Subprovince, but relative abundance data are not provided. The Pictured Cliffs fauna is similar in diversity to the Ten Bits fauna, and shares at least seven of the same species but lacks many of the rays found at Ten Bits. As with the Judith River fauna, the most common Ten Bits shark, Scapanorhychus texanus, is lacking in the Pictured Cliffs fauna, but Myledaphus bipartitis is a common species of ray that is absent in the Ten Bits fauna. Several Pictured Cliffs species (Odontaspis, Squatirhina) are not found at Ten

Bits, but are reported from the overlying upper shale member of the Aguja, and so could indicate that the Pictured Cliffs fauna is slightly younger than Ten Bits. The most common Ten Bits osteichthyan fish, Paralbula, is also found in the Pictured Cliffs fauna.

83 Texas Tech University, Joseph A. Schubert, May 2013

Comparison with the Blufftown Fauna

Case and Schwimmer (1988) described a shark and bony fish assemblage from the Blufftown Formation (Campanian) of western Georgia. They indicate that the

Blufftown fauna represents an estuarine or comparable river mouth environment similar to that recorded at the Ten Bits Microsite. Both locations are within the Gulf and

Atlantic Coast Subprovince, but the Blufftown site lies at the junction between Gulf and

Atlantic Coast, while the Ten Bits site lies at the westernmost extreme of the Gulf Coast near its border with the Southern Interior subprovince. It might therefore be expected that the two faunas could differ in some ways.

Although Case and Schwimmer (1988) did not report the total numbers of specimens in their sample, or the relative abundances of individual species, a general comparison can be made with the Ten Bits fauna based on the numbers of specimens listed for each species under the material examined. Of the 23 species identified by Case and Schwimmer (1988), the three most abundant are Scapanorhychus texanus (more than

1000 specimens), Squalicorax kaupi (more than 100 specimens), and Ischyrhiza mira

(about 20 specimens). Two of these three are also the most abundant chondrichthyans in the Ten Bits fauna. The remaining 20 species are each represented by about ten specimens or less. Ten of the species found in the Blufftown fauna are also represented in the Ten Bits fauna; these include Hybodus sp., S. kaupi, S. texanus, C. appendiculata,

I. mira, B. witchitaensis, R. levis, Albula sp., P. casei and Stephanodus sp. Although

Ptychotrygon occurs rarely in the Blufftown fauna, it is represented by a species (P.

84 Texas Tech University, Joseph A. Schubert, May 2013 vermiculata) not found at Ten Bits, where P. agujaensis is among the three most common chondrichthyans.

Comparison with the Black Creek Fauna

A diverse shark and bony fish fauna was described by Robb (1989) from the

Black Creek Formation near Phoebus Landing in North Carolina. This site lies along the central part of the Atlantic Coastal Plain Subprovince; the fauna found there is similar in age (Late Campanian), and from an estuarine depositional setting comparable to the Ten

Bits Microsite. Robb (1989) provides a comprehensive list with numbers of specimens recovered, and their relative abundances, allowing for a detailed comparison of the Black

Creek and Ten Bits faunas.

Collectively, the chondrichthyan fishes in the Black Creek fauna are much more abundant (96% of specimens, 12 species) relative to the bony fishes (4% of specimens, 9 species), in contrast to the Ten Bits fauna where the two groups are represented in roughly equal numbers. Scapanorhynchus texanus is by far the most common species in the Black Creek fauna, alone accounting for 79% of the chondrichthyan material, followed by Squalicorax kaupi (6%), and Ischyrhiza mira (3%). Together, these three species comprise 88% of the chondrichthyan specimens recovered; the remaining 9 species are each represented by only a few specimens. The abundance of S. texanus and

I. mira in the Black Creek fauna is similar to that at Ten Bits; however, no species of

Ptychotrygon is identified there. Several of the Black Creek sharks (e.g. Odontaspis,

85 Texas Tech University, Joseph A. Schubert, May 2013

Synodontaspis) are not found in the Ten Bits fauna, but otherwise the chondrichthyan species are comparable.

Among the osteichthyan species, Albula sp. and Paralbula casei, the two most common species at Ten Bits, occur rarely in the Black Creek fauna, each accounting for only a few percent of the identifiable bony fish elements. Instead, the most abundant osteichthyans in the Black Creek fauna (Enchodus, Xiphactinus, Anomoeodus) do not occur in the Ten Bits fauna.

Characteristics of the Gulf and Atlantic Coast Fauna

Some differences between the faunas compared above may reflect differences in the environments sampled at each of the sites, and so the presence or absence of species represented in low numbers at some sites may be insignificant. Similarly, the relative abundance of species may reflect the degree to which remains of those characteristic of open marine waters were mixed with those that inhabited primarily fresh or brackish water in coastal or estuarine settings.

Even so, the comparisons above clearly indicate that the shark and bony fish fauna at the Ten Bits Microsite is similar to those of the Gulf and Atlantic Coast subprovince in Georgia and North Carolina, and less like those in the Western Interior subprovinces. The Ten Bits, Blufftown, and Black Creek faunas share many of the same species, and in all three cases, the shark Scapanorhynchus texanus, is by far the most abundant chondrichthyan. This species appears to be absent from the Western Interior

86 Texas Tech University, Joseph A. Schubert, May 2013 faunas. In all three areas, the ray Myledaphus bipartitis, has not been found, and this is among the most common species in the Western Interior faunas.

The Ten Bits fauna appears to be unique in the abundance and diversity of ptychotrygonid rays, with at least five species, including Ptychotrygon agujaensis, which has not been reported in any other fauna. The possible presence of Igdabatus indicus here, a species that is otherwise known from Africa and Asia, is also unique, but could represent the chance occurrence of a single individual outside its normal range. On the other hand, the giant sawfish Onchosaurus pharao, has been reported from the Lower

Campanian San Carlos Formation in western Texas (Lehman, 1989), and this is also a species known elsewhere only from southern Europe, North Africa, and South America.

So, the rare occurrence of these species may indicate that they were more widely distributed in equatorial marine environments, and western Texas was near the northern limits of their range.

87 Texas Tech University, Joseph A. Schubert, May 2013

Figure 10. Late Cretaceous paleogeographic map of North America showing marine biogeographic provinces in the Western Interior, Gulf and Atlantic Coast (modified from Kauffman, 1984).

88 Texas Tech University, Joseph A. Schubert, May 2013

Figure 10. Paleogeographic map of North America during Campanian time, showing major physiographic and tectonic features, hypothesized oceanic current systems, an Pictured Cliffs, AG = Aguja, Ten Bits Microsite, BL = Blufftown, and BC = Black Creek; modified from Lehman, 1997).

Figure 11. Paleogeographic map of North America during Campanian time, showing major physiographic and tectonic features, hypothesized oceanic current systems, and locations of the marine micro-vertebrate sites discussed in the text (JR = Judith River, PC = Pictured Cliffs, AG = Aguja, Ten Bits Microsite, BL = Blufftown, and BC = Black Creek; modified from Lehman, 1997

89 Texas Tech University, Joseph A. Schubert, May 2013

Figure 12. Detailed paleogeographic reconstruction of the Western Interior region during Campanian time, showing hypothesized oceanic current systems, and locations of several marine micro-vertebrate sites discussed in the text (JR = Judith River, PC = Pictured Cliffs, AG = Aguja, Ten Bits Microsite; modified from Lehman, 2008).

90 Texas Tech University, Joseph A. Schubert, May 2013

Figure 13. – Ten Bits Ranch chondrichthyan assemblage by percent.

91 Texas Tech University, Joseph A. Schubert, May 2013

!"#$%&'($)('"&*+'+,"($

)!+' )++'

)++'

,+' (&#&)(*&(+$'

(+' ;32<397' !"#$%"%&$' %+' "#$,*$**%&,'

!+' )#$%(+!*$)$'

+' -./0.-' 1-2-./0.-' .31456738'8731-96508' :67-.' Figure 14. – Ten Bits Ranch Osteichthyan assemblage by percent

92 Texas Tech University, Joseph A. Schubert, May 20313

CHAPTER 4

CONCLUSIONS

A thin granular conglomerate within the Rattlesnake Mountain sandstone member of the Aguja Formation on Ten Bits Ranch preserves a diverse assemblage of small teeth, denticles, vertebrae, and other bones of chondrichthyan and osteichthyan fishes. This thin layer of teeth and bones probably represents a winnowed lag deposit, concentrated by wave action in a coastal marine environment. The deposit, referred to herein as the

"Ten Bits Microsite" is unusually fossiliferous, and yielded about 5000 specimens in a small amount of matrix (c. 50 kg) processed by screen-washing techniques for purposes of this research. The fauna preserved here is a diverse one, about 30 identifiable species of sharks, sawfishes, rays, and bony fishes recognized thus far, and others represented by indeterminate specimens. Most of the species represented, and those occurring most abundantly and best preserved, are known elsewhere from marine sedimentary facies.

Bones and teeth of crocodylians and turtles, as well as fresh or brackish water fish species, are typically broken, abraded, or represented by only a few specimens. These observations suggest that the Ten Bits Microsite provides a sample of predominantly shallow marine fish fauna. This fauna represents the southernmost marine micro- vertebrate fauna of middle Campanian age thus far known in North America.

The Ten Bits fauna is from a lower stratigraphic level than the Terlingua local fauna described by Rowe et al. (1992) from the upper shale member of the Aguja

Formation. The Terlingua local fauna is also from a different depositional setting and preserves a greater number of fresh water species, as well as terrestrial reptiles and

93 Texas Tech University, Joseph A. Schubert, May 20313

mammals that are absent in the Ten Bits fauna. Differences between the two faunas are due in part to their slightly different age, and to sampling different environments. The hybodontoid selachians, Hybodus and Lonchiodon, are very abundant in the Terlingua fauna, but only a few specimens have been found at Ten Bits. In contrast, the most abundant selachian in the Ten Bits fauna, Scapanorhynchus, is rare at the Terlingua

Microsite. An unidentified species of Ptychotrygon found in the Terlingua local fauna does not appear to represent any of the five species of ptychotrygonid rays represented at

Ten Bits.

The sample from Ten Bits Microsite yielded roughly comparable numbers of identifiable chondrichthyan fish specimens compared to osteichthyan fish specimens.

The chondrichthyan specimens, however, represent 23 species while the identifiable osteichthyan specimens represent 4 species. Two of the three most abundantly occurring chondricthyan species (Scapanorhynchus texanus and Ischyrhiza mira) are also the most common species in other middle to Late Campanian marine vertebrate faunas along the

Gulf and Atlantic Coastal Plain, as preserved for example in the Blufftown Formation of

Georgia and the Black Creek Formation in North Carolina. In contrast, another species abundantly represented in the Ten Bits fauna, Ptychotrygon agujaenisis, is unknown in correlative marine faunas elsewhere. Although Ptychotrygon occurs rarely in the

Blufftown fauna, it is represented there by a different species (P. vermiculata), and no species of the genus is reported from the Black Creek fauna. The Ten Bits Microsite yielded the type specimens of P. agujaensis (McNulty and Slaughter, 1972), and several additional species pertaining to the genus are reported here for the first time. The

94 Texas Tech University, Joseph A. Schubert, May 20313

abundance and diversity of ptychotrigonid rays may be a unique feature of the Ten Bits fauna.

The most common bony fishes found in the Ten Bits fauna (Paralbula casei and

Albula sp.) are also reported elsewhere in Gulf and Atlantic Coastal Plain faunas, but they are rare there and subordinate to fishes not recovered at the Ten Bits Microsite (e.g.,

Enchodus, Xiphactinus, Anomoeodus). Instead, Paralbula casei is also an abundant bony fish found in marine vertebrate faunas of the Western Interior, for example in the

Pictured Cliffs Sandstone of New Mexico. The most common chondrichthyan fishes found in Western Interior faunas, as preserved for example in the Judith River Formation of Montana, are either unknown (Plicatilamna arcuata, Hypotodus grandis) or rare

(Cretorectolobus olsoni, Protoplatyrhina renae) in the Ten Bits fauna, and the common

Western Interior ray Myledaphus bipartitis does not occur at Ten Bits or any other Gulf or Atlantic Coast fauna. These differences probably reflect latitudinal variation, oceanic water circulation pattern, or variation in other environmental conditions between the

Western Interior Seaway and the Gulf or Atlantic Coast that restricted the distributions of some marine fish species. The similarities between the Ten Bits fauna and those of the

Atlantic and Gulf Coast indicate that western Texas was more closely allied biogeographically with that province than with the Western Interior of North America.

One species tentatively identified in the Ten Bits fauna on the basis of a single tooth, Igdabatus indicus, is otherwise known only from Africa and Asia. If this identification is correct, it would represent the only known occurrence of the species in

North America. This could reflect the chance preservation of a single individual outside

95 Texas Tech University, Joseph A. Schubert, May 20313

of its normal range. Other Tethyan marine vertebrates have been reported from

Campanian strata in western Texas (Onchosaurus pharao; Lehman, 1989). Western

Texas may have been near the northern limits of the range for tropical marine vertebrate species.

96 Texas Tech University, Joseph A. Schubert, May 2013

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