Vertebrate Paleontology and Magnetostratigraphy of the Upper Aguja Formation (Late Campanian), Talley Mountain Area, Big Bend National Park, Texas

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1998 Vertebrate Paleontology and Magnetostratigraphy of the Upper Aguja Formation (Late Campanian), Talley Mountain Area, Big Bend National Park, Texas. Julia Tippins Sankey Louisiana State University and Agricultural & Mechanical College

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Recommended Citation Sankey, Julia Tippins, "Vertebrate Paleontology and Magnetostratigraphy of the Upper Aguja Formation (Late Campanian), Talley Mountain Area, Big Bend National Park, Texas." (1998). LSU Historical Dissertations and Theses. 6762. https://digitalcommons.lsu.edu/gradschool_disstheses/6762

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. VERTEBRATE PALEONTOLOGY AND MAGNETOSTRATIGRAPHY OF THE UPPER AGUJA FORMATION (LATE CAMPANIAN), TALLEY MOUNTAIN AREA, BIG BEND NATIONAL PARK, TEXAS

A Dissertation

Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy

The Department of Geology and Geophysics

by Julia T. Sankey B.S., Albertson College of Idaho, 1987 M.S., Northern Arizona University, 1991 A ugust 1998

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UMI 300 North Zeeb Road Ann Arbor, MI 48103

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. DEDICATION This work is dedicated to my mother, Jean M. Sankey, who has provided constant enthusiasm for and assistance with my research.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGMENTS Many people helped me with this research project. I thank Dr. Judith Schiebout for her constant support and advice during my four years at Louisiana State University (L.S.U.). She suggested this research project, guided its development, and helped gather grant support. Dr. Wulf Gose at the University of Texas at Austin, allowed me to work in his paleomagnetics

lab and spent many days helping with the work. I also appreciate the help and advice from my dissertation committee members: Dr s. Arnold Bouma (minor advisor), Joe Hazel, Juan Lorenzo, John Wrenn, and Gary Wise (outside committee member). Thanks to my friends at L.S.U., especially Pam Borne. The L.S.U. Museum of Natural Science and the Department of Geology and Geophysics provided financial and technical support. The Dinosaur Society provided a generous grant for this research. The National Park Service allowed collection within Big Bend National Park (permit #BIBE-N-50.001). Big Bend personnel were very helpful, especially Phil Koepp, Vidal Davilla, and Mike Fleming. Dr. Suyin Ting and Mrs. Ruth Hubert did the initial lab work for this research. Museum volunteers helped with the lab and curation work, especially Tina Aherns, Charlsa Moore, Jason Ramcharan, Margaret Schneider, and Sarah Wachter. Jean M. Sankey enthusiastically assisted with nine weeks of field work over the course of

three trips to Big Bend. Jason Ramcharan was an enormous help with the lab, library, and computer work. Marilee Eggart (L.S.U.) made the illustrations, and Kerry Lyle (L.S.U.) photographed the conglomerates and larger fossils and produced the photographic plates. I appreciate valuable discussions with Drs. Thomas Lehman, Timothy Rowe, Wann Langston, Jeff Eaton, Richard Cifelli, Christopher Brochu, and with Anne Weil and Randall

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Nydham. Dr. Lehman (Texas Tech University) graciously spent an entire day with me discussing the Aguja Formation and its fossils. He also gave me a copy of an unpublished facies map of the Talley Mt. area. Anne Weil (U.C. Berkeley) generously drove out to Big Bend and showed me the Terlingua Held area and taught me the basic stratigraphy of the Aguja Formation. Dr. A.M. Ziegler allowed me to use an unpublished paleogeographic map that he, Hulver, and Rowley had constructed at the University of Chicago (Fig. 1.3). Melissa and Mary Winans gave me a home in Austin during my frequent visits to the University of Texas. I appreciate the access I was given to the fossil collections at American Museum of Natural History, National

Museum of Natural History, University of Texas at Austin, University of Oklahoma (Norman), Weber State University (Ogden), and University of California at Berkeley.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS Dedication...... iii

Acknowledgments ...... iv List of Tables...... viii

List of Figures...... ix Abstract ...... xi Introduction...... 1 Abbreviations Cited In Text ...... 2

The Late Campanian Talley Mountain Local Fauna and Magnetostratigraphy, Upper Aguja Formation, Big Bend National Park, Texas...... 3 Introduction...... 3 Stratigraphy...... 32 Paleomagnetics...... 39 The Talley Mountain Local Fauna...... 52 Discussion...... 83 Conclusions...... 92 Chondrichthyans and Actinopterygians of the Talley Mt. Local Fauna, Upper Aguja Formation (Late Campanian), Big Bend National Park, Texas...... 94 Introduction...... 94 Systematic Paleontology...... 95 Discussion...... 106 Conclusions...... 108

Herpetofauna of the Talley Mt. Local Fauna, Upper Aguja Formation (Late Campanian), Big Bend National Park, Texas...... 109 Introduction...... 109 Systematic Paleontology...... 110 Discussion...... 129 Conclusions...... 131

Mammals of the Talley Mt. Local Fauna, Upper Aguja Formation (Late Campanian), Big Bend National Park, Texas...... 132 Introduction...... 132 Systematic Paleontology...... 133 Discussion...... 137 Conclusions...... 137

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Conclusions...... 139

Sum m ary...... 147

References Cited ...... 149

Appendix I. Paleomagnetic Results...... 159

A ppendix n. Conglomerates Sampled...... 245

Appendix HI. Measurements of Sauromitholestes teeth...... 246

Appendix IV. Measurements of Richardoestesia teeth...... 248

Vita...... 249

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF TABLES

Table LI. Estimates of the duration (My) for the Talley Mt. polarity sequence...... 51

Table L2. Age (Ma) estimates for the Talley Mt. conglomeratic units...... 52

Table L3. Vertebrates from the Talley Mt. local fauna...... 62

Table L4. Vertebrates of the Terlingua (Rowe et al., 1992; Weil, 1992; Cifelli, 1995; Miller, 1997) and Talley Mt. local faunas...... 64

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF FIGURES

Figure 1.1. Late Cretaceous (late Campanian) paleogeographic map of N orth America...... 4

Figure 1 2 . Late Cretaceous (late Campanian) paleogeographic map of the western interior of North America...... 8

Figure 1.3. Late Cretaceous (Maastrichtian) paleogeographic map of North and South America...... 10

Figure 1.4. Map of Big Bend National Park, west Texas...... 17

Figure 1.5. Aguja Formation stratigraphy and positions of the Terlingua and Talley Mt. local faunas...... 19

Figure 1.6. Photograph of the Talley M t field area, view to the southeast...... 24

Figure 1.7. Photograph of the Talley Mt. field area, view to the north., 26

Figure 1.8. Photographs of conglomeratic unit (VL-489/140; arrow)...... 28

Figure 1.9. Topographic map of the Talley Mt. field area...... 30

Figure 1.10. Facies map of rock outcrops in the Talley Mt. field area...... 33

Figure 1.11. Stratigraphic section (JS-1) through the lower part of the upper shale member of the Aguja Formation in the Talley Mt. field area ...... 36

Figure 1.12. Two example of the behavior of normal polarity samples (39.1 and 41.3) during progressive thermal demagnetization....40

Figure 1.13. Three example of the behavior of reversed polarity samples (1.1, 2.1, and 5.1) during progressive thermal demagnetization...... 42

Figure 1.14. 52-meter Talley Mt. magnetic polarity sequence from the lower part of the upper shale member of the Aguja Form ation...... 45

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.15. Correlation of the Talley Mt. magnetic polarity sequence from the lower part of the upper shale member of the Aguja Formation to the geomagnetic polarity time scale (Gradstein et al., 1995)...... 48

Figure 1.16. Photographs of fossiliferous conglomeratic rocks...... 53

Figure 1.17. Photographs of fossiliferous conglomeratic rocks...... 55

Figure 1.18. Conglomeratic rock soaking in acetic acid solution...... 58

Figure 1.19. Chondrichthyan teeth from the Talley Mt. local fauna...... 67

Figure 1.20. Actinopterygians from the Talley Mt. local fauna...... 70

Figure 1.21. Amphibian and lizard fossils from the Talley Mt. local fauna...72

Figure 1.22. Turtle carapace fragment from the Talley Mt. local fauna...... 74

Figure 1.23. Crocodylian fossils from the Talley Mt. local fauna...... 77

Figure 1.24. Dinosaur teeth from the Talley Mt. local fauna...... 79

Figure 1.25. Dinosaur teeth from the Talley Mt. local fauna...... 81

Figure 1.26. Mammal teeth from the Talley Mt. local fauna...... 84

Figure 1.27. Modern coastal and swamp environments in southeastern Texas...... 89

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT Considerable north-south latitudinal diversification existed among vertebrate faunas along the Western Interior Seaway during the late Campanian; this has caused difficulty correlating isolated faunas, especially southern ones, which contained endemic taxa and often lack non-

paleontologic age control. The Talley Mt. local fauna is a late Campanian vertebrate fauna from the upper Aguja Formation, Big Bend National Park, Texas. It is one of the southernmost late Campanian vertebrate faunas, and is one of the few associated with magnetostratigraphy. The fauna is from five channel deposits, spanning 20 meters of section, from the lower portion of the upper shale member of the Aguja Formation. Deposition occurred within a coastal floodplain during the final marine regression from the area. Fossils were recovered by bulk sampling (-1630 kg) and add-disaggregating pedogenic nodule-rich, carbonate-cemented, conglomeratic rocks. The fauna contains 35 terrestrial and aquatic taxa, induding 8 chondrichthyans, 2 actinopterygians, 3 amphibians, 1 trionychid turtle, 4 squamates (induding Chamops and Peneteius sp. nov., new records for the Aguja), 5

crocodylomorphs, 6 dinosaurs, and 6 mammals (Cimolomvs sp., Meniscoessus sp., cf. Cimexomvs. Paradmexomvs sp., Alphadon cf. A. hallevi. and A. cf. A. sahnii). Aquatic taxa decrease in abundance upsection, reflecting

the marine regression from the area and the beginning of drier, more seasonable dimates. The fauna is taxonomically similar to the nearby Terlingua local fauna, but with significant taphonomic and sampling differences. The 52 meter paleomagnetic polarity sequence contains two reversed polarity zones, and is corrdated to the base of Chronozone 32 based on the Judithian taxa in the fauna and on the ages of underlying and

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. overlying Aguja deposits. On the basis of this correlation and on average sedimentation rates of 29 meters/million years, the Talley Mt. local fauna

approxim ately 73.6 to 74.3 Ma.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. INTRODUCTION The purpose of this work is to identify and describe the small vertebrate fossils from the late Campanian (Late Cretaceous) upper Aguja Formation deposits in the Talley Mt. area of Big Bend National Park, Texas, to correlate the paleomagnetic polarity sequence from these sedimentary deposits to the geomagnetic polarity time scale in order to better constrain the age of the fauna, and to determine if faunal changes occurred during the time

sam pled. This dissertation is organized into four papers. The first paper synthesizes late Campanian biogeography of the Western Interior and discusses the difficulties involved in correlating vertebrate faunas of this age. The stratigraphy and paleontology of the Aguja Formation is summarized, the new paleomagnetic and paleontologic information is reported, and the magnetostratigraphic correlation is discussed. The focus of this first paper is on the geochronologic and paleogeographic implications of the work. The following three papers are detailed descriptions and discussions of all the

identifiable vertebrates recovered. These three papers are organized by taxonomic groups: the first paper covers the chondrichthyans and actinopterygians; the second, the amphibians and reptiles; the third, the mammals. The final section synthesizes the conclusions of all four papers, particularly focusing on the taphonomic and sampling differences between the Talley Mt. and Terlingua local faunas, the faunal changes observed within the Talley Mt. fauna, the magnetostratigraphic interpretations, and the implications of this work for late Campanian biogeography. Because an attempt was made to reduce the amount of repetition among the papers, the

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. first paper should be read first in order to better understand the following papers. ABBREVIATIONS CITED IN TEXT Abbreviations for institutions dted are: AMNH, American Museum of Natural History, New York City, New York; LSUMG, Louisiana State University Museum of Geoscience (a division of the LSU Museum of Natural Science), Baton Rouge, Louisiana; NMNH, National Museum of Natural History, Washington D.C.; OMNH, Oklahoma Museum of Natural History, Norman, Oklahoma; TMM, Texas Memorial Museum, Vertebrate

Paleontology and Radiocarbon Laboratory, University of Texas, Austin, Texas;

UCMP, Museum of Paleontology, University of California, Berkeley, California; WSC, Weber State College, Ogden, Utah. Other frequently used abbreviations are: LMA, North American Land Mammal Age; Ma, mega-annum; My, million years; WPA, Work Progress Administration; VL, vertebrate locality number; and V, vertebrate fossil specimen number. An LSU complete catalog number for a vertebrate fossil includes both of these numbers, separated by a colon; for example, 488:5566. Often only the second number is used. Abbreviations for mammal teeth are: m, molar; pm, premolar; r, right; 1, left; 1-4, tooth position; capitalized, upper

tooth; and lower case, lower tooth.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. THE LATE CAMPANIAN TALLEY MOUNTAIN LOCAL FAUNA AND MAGNETOSTRATIGRAPHY, UPPER AGUJA FORMATION, BIG BEND NATIONAL PARK, TEXAS INTRODUCTION Explanation of Problem During the Late Cretaceous, an extensive and fairly continuous lowland bordered the western shore of the Western Interior Seaway (Fig. 1.1). However, beginning in the late Campanian and early Maastrichtian, several combined events began to produce a very different environmental and physiographic setting within the interior of western North America. These events were: the initiation of western tectonism (Laramide), the resultant rain shadow zone produced by the western highlands, and the final regression of the Western Interior Sea in southern North America.

Vertebrate faunas during this time, represented by the Landan North American Land Mammal "Age" (LMA), adapted to distinct environmental and climatic provinces (Lehman, 1991). Older vertebrate faunas (represented

by the Judithian LMA) were considered to be fairly homogeneous, at least

from southern Alberta to central Wyoming. Recently, considerable latitudinal diversification, south to north, has been recognized (Lillegraven

and Ostresh, 1990). Correlations among terrestrial vertebrate faunas during the late Campanian-early Maastrichtian are especially difficult for the following reasons: 1) distinct faunal provinces were beginning to form during this

time, espedally along a north-south latitudinal gradient; 2) faunas were often deposited within separate basins; 3) LMAs were defined by occurrence of taxa from northern faunas from Wyoming, Montana, and Alberta; and 4) often the faunas lack good independent age control from radioisotopic age dating,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.1. Late Cretaceous Gate Campanian) paleogeographic map of North America showing the Western Interior Sea separating the western (Asian- American Peninsula) and eastern (Euroamerica) land portions of North America during this time. Numbers refer to the locations of four major late Campanian vertebrate faunas: 1) Judith River and Two Medicine Formations, Alberta and Montana; 2) Fruitland and Kirtland Formations, New Mexico; 3) Aguja Formation, Texas; and 4) Marshalltown Formation, New Jersey. Figure modified from (Lehman, 1997). Position of Gulf of Mexico volcanoes from (Salvador, 1991:425). Star is Big Bend, Texas.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. —40°N

Western \ Interior Sea Cordilleran Fold and Thrust Belt

Magmatic —20°N Arc

100°W 80°W

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. magnetostratigraphy, and marine fossil correlations (Eaton, 1987; Lehman, 1987, 1991; Lillegraven and McKenna, 1986; Lillegraven and Ostresh, 1990; Rowe et al., 1992; Sloan, 1987). Terrestrial vertebrate faunas from the north

have been extensively studied (Lance Formation, Clemens, 1973; Estes, 1964; Judith River Formation, Sahni, 1972; "Mesaverde" Formation, Lillegraven and McKenna, 1986; and Albertan faunas, Fox, 1976, and 1981). However, assignment of southern faunas to LMAs (defined on northern faunas) has been difficult. Examples are those from the Kaiparowits Formation, Utah (Cifelli, 1990a, 1990b), the Fruitland/Kirtland Formations, New Mexico

(Clemens, 1973; Flynn, 1986; Rigby and Wolberg, 1987), the "El Gallo"

Formation, Baja California, Mexico (Lillegraven, 1972, 1976), and the Aguja Formation, west Texas (Rowe et al., 1992). The last area provides a good example of this difficulty. The Terlingua local fauna, from the upper Aguja Formation, could only be tentatively assigned to the Judithian LMA because it contains endemic mammalian taxa and has only a few taxa in common with typically Judithian assemblages. However, it most closely resembles faunas considered to be Judithian from the Kaiparowits Plateau, southern

U tah (Cifelli, 1995; Miller, 1997; Rowe et al., 1992; Weil, 1992). In order to better constrain the age of the Terlingua local fauna and the newly discovered Talley Mt. fauna (Sankey, 1995,1996,1997; Sankey and Schiebout, 1997) from the upper Aguja Formation, we employed magnetostratigraphy. Our research has contributed the following: 1) a new late Campanian vertebrate fauna and 2) the first independent age control for the upper Aguja Formation, its vertebrate fossils, and for the final marine

regression in this area.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Additionally, we discovered that carbonate-cemented channel lag deposits containing pedogenic nodules and vertebrate fossils, abundant in the upper Aguja Formation, are rich microvertebrate sites. The vertebrate fossils

from these deposits had previously been ignored because of the lack of feasible techniques for their recovery. We successfully recovered many identifiable vertebrate fossils by bulk-sampling the rocks, using dilute acetic add to disaggregate them, and screening the resultant residue. This new method has opened up the possibility that these resistant, common and widespread, but paleontologically unstudied rocks can serve as quickly recognizable, stratigraphically dosely spaced sources of both marine and

terrestrial vertebrates, bringing the biostratigraphic potential of terrestrial microvertebrates doser to that of marine microinvertebrates such as foraminifera and ostracodes. Tectonic Setting of Western North America in the Late Cretaceous During the Late Cretaceous, subduction of oceanic lithosphere under western North America formed a magmatic arc, producing a peninsula of volcanic highlands connecting western North America and northeast Asia (Coney et al., 1980). This peninsula was then deformed by collisions between

microcontinents and Canada (Monger et al., 1982). The eastern side of the

western North American peninsula (the passive margin) had a gentle

topographic gradient, and sediments accumulated in an extensive foreland basin from northern Canada to central Mexico (Figs. 1.1,1.2,1.3). Beginning in the early Maastrichtian (~71 Ma), Laramide deformation produced volcanic centers, basement uplifts, and intermontane basins within the western interior of North America. By the late Maastrichtian, the physiography and environments in the western interior had dramatically

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 12.. Late Cretaceous Gate Campanian) paleogeographic map of the western interior of North America showing paleoshoreline positions, paleolatitudes, and mean annual temperature isotherms. Numbers refer to the locations of major late Campanian vertebrate faunas. Circles represent "Corvthosaurus” faunas; squares, the "Kritosaurus" faunas. Circles: 1) Dinosaur Provincial Park, Alberta; 2) Judith River Formation, Montana; 3) Wheatland Co., Montana; 4) Two Medicine Formation, Montana; 5) Mesaverde Formation, Bighorn Basin, Wyoming; and 6) Wind River Basin, Wyoming. Squares: 1) Williams Fork Formation; 2) Kaiparowits Formation, Utah; 3) Fruitland and Kirtland Formations, New Mexico; 4) San Carlos Formation, Texas; 5) Aguja Formation, Texas; 6) Cerro del Pueblo Formation, Mexico. Figure modified from (Lehman, 1997). Star is Big Bend, Texas.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. I 1 alluvial plain AQliJ ILAPO LLENITBS lagB coastal plain ■nm •3 y boundary of faunal & floral IS®/ zones

------i

Llinta Uplift ZONE OF FAUNAL MIXING & ENDEMISM T VV

Utah f-— 2.g,...20“C % I Embayment"

MIXED FLORA

NORMAPOLLES. i § § $ S f c o f Ta

0 200 400 600 km ______1 I______I__ I 110°W

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.3. Late Cretaceous (Maastrichtian) paleogeographic map of North and South America with patterns representing different elevations. A land connection existed between North America, Europe, and Asia at this time, allowing faunal exchange, but South and North America lacked such a connection. The Western Interior Seaway had retreated to such an extent that a land connection between the western and eastern portions of North America was almost possible (arrow). Figure is modified from an unpublished map by Ziegler, Hulver, and Rowley and is used here with permission from Ziegler (written comm., 1998). Star is Big Bend, Texas.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ^ Mts. >1QQ0m V7A Uplands 200 to 1000m r~ l Lowlands 0 to 200 m I I Inner and outer shelf -200 to -50m I I Slope -2000 to -200m H Deep ocean < -2000m

2 0 ^ :

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. changed from the previous gentle topographic gradient. For example, previously eastward flowing drainages now began to drain to the west, toward the Cordilleran fold and thrust belt front. Lehman (1987) outlined several sedimentary depositional provinces which formed in distinct paleoenvironmental and paleophysiographic provinces during this time: piedmont, alluvial plain, and coastal lowland lithosomes. He also outlined three dinosaur-dominated vertebrate faunas which occurred in distinct environments of this time: the Leptoceratops. Triceratops. and Alamosaurus Faunas. Western Interior Seaway The Western Interior Seaway covered much of the interior of North America during the Late Cretaceous, connecting the Arctic Ocean with the Gulf of Mexico, and thus, bisecting North America into eastern and western areas. It was a total of 5,000 km long, had depths of up to 200 m, and had a 25,000:1 aspect ratio. There were three outlets for the seaway: the Arctic Ocean, Gulf Coast, and Hudson Strait outlets (Ziegler and Rowley, in press). During the late Campanian to early Maastrichtian, sea-level lowering and

infilling of the seaway by sediments (especially from the western uplands, overthrust belt, and Laramide Mountains; Dickenson et al., 1988) contributed to the closure of the outlets and the final retreat of the seaway. Of the seaway's three outlets, the Arctic outlet closed first, in the middle Maastrichtian. The Gulf Coast outlet closed next, by the late Maastrichtian (McGowen and Lopez, 1983). Although the entire Western Interior Seaway drained by the Paleocene, a long and narrow sea, the Cannonball Sea, reinundated part of the northern Great Plains in the middle late Paleocene (Keefer, 1965; Marinovich et al., 1985), but eventually drained through the

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Hudson Strait outlet (Ziegler and Rowley, in press). A transcontinental arch formed in Canada and in part of the U.S. in the late Campanian-early Maastrichtian, producing the first good land connection between the western and eastern parts of North America. At this time, the seaway persisted in northern and southern embayments: the northern one near the Mackenzie Delta-Banks Island area of Arctic Canada (Miall, 1984) and the southern one in the Gulf Coast of the U.S. Patterns of dinosaur distributions through time

could test how effective epeiric seas were as barriers (Ziegler and Rowley, in press). For example, some of the late Campanian vertebrate faunas from the southeastern U.S. (Alabama, Georgia, North Carolina, etc.) appear more similar to the faunas from Big Bend, on the other side of the seaway, than to the faunas from New Jersey, on the same side of the seaway. This similarity has been explained by proposing that partial land connections might have existed across the southern part of the seaway, allowing some vertebrates to disperse (Lambe, 1997). Some dispersal across the seaway may have been possible across volcanic islands that existed during this time (Salvador, 1991). Land exposure was particularly possible during marine regressions when the shoreline m oved east-west across a ~500 km w ide area (Lehman, 1987). General regression of the seaway occurred for approximately 18 My, between earliest Campanian and Maastrichtian.

Kauffman (1977) tied the major transgressive and regressive cycles within the seaway to global eustatic fluctuations. Only those relevant to the Late Cretaceous of west Texas are discussed here. Transgression 8 occurred in middle Campanian (Kauffman, 1977) and is represented by the McKinney Springs Tongue of the Pen Formation (which intertongues with the Aguja Formation; Lehman, 1985). Regression 8 occurred in the late Campanian

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (Kauffman, 1977) and is recorded in the upper Aguja Formation. The final Late Cretaceous transgressions (T9 and T10; Kauffman, 1977) are only known

from northern deposits and are not recorded in deposits from west Texas, New Mexico, or Colorado. The regressive phases are only represented as one event in the southern deposits (Lehman, 1985). In Big Bend, this final regressive phase is recorded in the deposits of the upper shale member of the Aguja Formation. The presence of the Western Interior Seaway strongly effected the climate of the area. Without its presence within the interior of North America during the Late Cretaceous, the climate would have been significantly more continental, and during its final regression, climates became more seasonal. This climatic shift was also influenced by the initiation of a rainshadow effect within the interior, caused by western tectonism (overthrust belt) and uplift of the Laramide Mountains. This research helps constrain the timing of the final marine regression from west Texas and the initiation of continental seasonality in this area. Geologic and paleontologic evidence has indicated that western Texas began to experience distinct climate seasonality in the early Maastrichtian (Lehman, 1987,1991; Schiebout, 1979). However, we suggest that this had probably begun even earlier, in the late Campanian. This idea has also been recently

proposed by Lehman (1997). Geologic Setting During the Late Cretaceous, a shift between two tectonic settings

occurred in the Big Bend area of west Texas. The first setting, from Cenomanian through Campanian, was a deep rift basin in which the Boquillas, Pen, and lower Aguja Formations were deposited in the

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. "Chihuahua Trough" and on the CoahuiUa Carbonate Platform to the east (DeFord, 1969; Lehman, 1985; Padilla y Sanchez, 1982). The second, from late Campanian through Maastrichtian, was the initiation of Laramide tectonism,

during which deposition of the upper Aguja and lower Javelina Formations occurred (DeFord, 1969; Lehman, 1985; Padilla y Sanchez, 1982). Western volcanic highlands were the main source rock for the Aguja and lower

Javelina Formations (McBride et al., 1974 in Lehman, 1985). During the Maastrichtian, the Chihuahua Tectonic Belt, a southern

extension of the Rocky Mountain Cordilleran Fold and Thrust Belt, formed to the west of Big Bend, and uplift of the Del Norte-Santiago-Sierra del Carm en range began to the east (Cobb and Poth, 1980; M uehlberger, 1980; Woodward and Duchene, 1981). Between these two uplifted areas was a northwest-trending, intermountain basin, the "Tomillo Basin" (named by Wilson, 1969), the southernmost Laramide-age intermontane basin in the

North American cordillera (Lehman, 1985, 1991; Runkel, 1990; and Stevens and Stevens, 1990). The basin existed from -80-40 Ma, and experienced two major pulses of tectonism and sedimentation during this time: 1) from

middle to late Maastrichtian and 2) from late Paleocene to early Eocene.

These two phases of sedimentation and tectonism match the two-phase tectonic model of Laramide deformation of Chapin and Cather (1981,1983) developed from basins in the central and southern Rocky Mountains

(Lehman, 1991). Late Cretaceous and Early Tertiary deposits in the "Tomillo Basin" were buried, folded, and greatly eroded prior to the late Eocene volcanic eruptions in the area (Maxwell et al., 1967). Today, most of Big Bend

National Park (Fig. 1.4) lies within a Basin and Range graben of Late Tertiary-

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. age, bounded to the east and west by upfaulted Cretaceous limestones (Lehman, 1985). This younger structural basin is called the "Sunken Block" (Uden, 1907).

Late Cretaceous sedimentary deposits in the Big Bend area include marine, prodeltaic-deltaic, and fluvial-floodplain sediments and are

represented by the Boquillas, Penn, Aguja, and the lower Javelina Formations, respectively (Hopkins 1965; Lehman 1982,1985,1991; Maxwell et al. 1967; Schiebout et al., 1987). A section of terrestrial deposits crossing the Cretaceous-Tertiary (K-T) boundary occurs within the upper Javelina

Formation (Lehman 1985,1991; Standhardt 1986, 1995; Schiebout et al., 1987). Aguja Formation

The Late Cretaceous Aguja Formation represents marine, paralic, and fluvial sediments which were deposited during the final regression of the Western Interior Seaway from west Texas. The Aguja Formation (Fig. 1.5) is widespread in the Big Bend area, thins to the east, and contains 135 to 285

meters of paralic and marine sandstones interbedded with shale and lignite (Lehman, 1985; Rowe et al., 1992). Sediments w ere deposited in the following environments: open and restricted shallow sublittoral areas, coastal marshes

and swamps, estuaries, deltas, and fluvial floodplains. It contains late Campanian to early Maastrichtian invertebrate and vertebrate fossils (Cifelli, 1995; Lehm an, 1982,1985; Miller, 1997; Rowe et al., 1992; Standhardt, 1986;

Weil, 1992). The ages for the lower Aguja Formation are based primarily

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.4. Map of Big Bend National Park, west Texas showing area of Aguja Formation outcrops in the Park (stippled). The locations for the late Campanian aged Talley Mt. and Ter lingua local faunas are shown by arrows. Both faunas are from the lower part of the upper shale member of the Aguja Form ation.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TERLINGUA^rD FIELD AREA

TALLEY MT. FIELD AREA Outcrop of Aguja Formation within Big Bend National Park 15 km

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.5. Aguja Formation stratigraphy and positions of the Terlingua and Talley Mt. local faunas within the lower part of the upper shale member of the Aguja Formation (modified from Rowe et al., 1992). The stratigraphic position of the Talley Mt. localities above the Terlingua Creek Sandstone is based on Lehman (1985; Plate HI and written comm., 1998). Formal members of the Aguja Formation are capitalized; informal members are not.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. sw NE

_uppershalembr Talley Mt. local fauna f - non-manne=.-=.— —

O I ! rl» 9fe?!< |§ndstonembr.p £ I^p£^-£,Terlingua local fauna ^

McKinney Springs tongue of Pen Fm.l^?[Pf ^ )iS

Rattlesnake Mt. sandstone mbr m 100

lower shale sandstone

FORMATION marine^ m

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. on marine invertebrate fossils which have been correlated to the Gulf Coast Cretaceous biostratigraphic zonation of ammonites, oysters, inoceramid bivalves, and foraminifera (Lehman, 1985). For the more terrestrial, upper

Aguja Formation, the correlations are based on ostreid bivalves and vertebrates (especially, dinosaurs and mammals) (Cifelli, 1995; Lehman, 1982,

1985; Rowe et al., 1992; Standhardt, 1986; Weil, 1992). The Aguja Formation lacks non-paleontologic age control because

rocks suitable for radiometric dating are rare. Magnetostratigraphy has been done on the Early Tertiary deposits (Rapp et al., 1983), but the magnetostratigraphy of the Late Cretaceous deposits (lower Javelina Formation) done by MacFadden (Standhardt, 1986) has never been published in any detail. Upper shale member—The upper shale member of the Aguja Formation represents the last of the pre-Laramide tectonic sedimentation in the area. It occurs throughout Big Bend, but there are few complete sections. It is 170-80 m thick, from west to east, and contains fluvial strata deposited during the final retreat of the seaway from the area. It is 67% mudstone, 33% sandstone, and contains many fluvial channel lag conglomerates containing

mostly intra-basinal pedogenic carbonate nodules, bones, and wood. Sediment source areas were probably the western Mexico magmatic arc, -500 km to west. It had a relatively low rate of sedimentation (~13m/My; Lehm an, 1991).

The lower part of the upper shale member contains drab, gray carbonaceous mudstones, thin beds of lignite, and large siderite ironstone concretions. It formed in distributary channels, levees, crevasse splays, and

poorly drained interdistributary marshes and bays. The upper part contains

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. variegated mudstones (gray, purple, and maroon), paleo-caliche nodules, and interbedded fine to medium, submature to mature, tan and brown, hogback- forming sandstones with conglomeratic lags of paleo-caliche nodules representing fluvial environments of the deltaic coastal plain and inland floodplain (Lehman, 1985). The age of the upper shale member is late Campanian to early Maastrichtian, based on its invertebrate and vertebrate faunal assemblages. The lower part contains the Kritosaurus (Dinosauria) assemblage and is late Campanian (Lehman, 1985). The age is constrained by the nearshore marine invertebrates from the underlying Terlingua Creek Sandstone Member (middle Campanian), which represents the last marine regressive event in the area. It is also constrained by vertebrates (especially mammals) that it contains, such as those from the Terlingua local fauna (Fig. 1.5) which is considered to be Judithian (Cifelli, 1995; Rowe et al., 1992; Weil, 1992). The uppermost part of this member is less fossiliferous, but based on its vertebrate fauna, is considered to be early Maastrichtian (Lehman, 1985; Standhardt,

1986). The Terlingua and the Talley Mt. local faunas are the only faunas described from the lower portion of the upper shale member (Figs. 1.5; Cifelli, 1995; Miller, 1997; Rowe et al., 1992; Sankey, 1995,19%, 1997; Sankey and

Schiebout, 1997; Weil, 1992). The Terlingua local fauna is from a locality near Dogie Mountain, just outside of Big Bend National Park, and approximately

40 km northwest of Talley Mt. It was produced by screening approximately

two tons (A. Weil, oral comm., 19%) of a very fossiliferous thin sandy lens. This lens is within a unit of carbonaceous shales and lignites, and is near the boundary of the coastal swamp and coastal floodplain facies, within the lower

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. part of the upper shale member of the Aguja. The depositional environment was probably estuarine, based on the fades assodations, sedimentological evidence, and the fauna (Weil, 1992). Thirty seven lower vertebrate and ten mammal spedes (induding new genera and spedes) have been discovered

(Cifelli, 1995; Miller, 1997; Rowe et al., 1992; Weil, 1992). Talley Mt field area Field work was conducted in a one km square area near Talley M t, in the southern part of Big Bend National Park (Figs. 1.6,1.7). Exposed in this area are good outcrops of the upper shale member of the Aguja Formation in shallowly northward-dipping hogbacks of sandstone with interbedded

mudstones. The marsh deposits in this area have occasional accumulations of the giant crocodile, Deinosuchus riograndensis (Colbert and Bird, 1954) and dinosaurs, Chasmosaurus mariscalensis. hadrosaurs, and camosaurs (Lehman, 1982, 1985). Additionally, fossiliferous carbonate-cemented conglomerates in channel lag deposits of large channels are very common (Fig. 1.8). Five particularly rich units were sampled for fossils (Fig. 1.9). Outcrops of the upper shale member in this area were measured and described in 12 stratigraphic sections by Lehman (1982) to place previous

collections of fossil dinosaurs and crocodiles into a depositional and stratigraphic framework; later these outcrops were tied to others of the Aguja (Lehman, 1985). Several facies within the upper shale member have been distinguished based on lithologies and fossils (Lehman, 1982,1985). This area is included in the geologic map of Big Bend National Park (Maxwell et al. 1967). A large-scale geologic map of the field area was made in order to detect any geologic structures like faults and igneous intrusions that may have disturbed the original stratigraphy of these units and to show the

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.6. Photograph of the Talley Mt. field area; view to the southeast Talley M t, an Early Tertiary intrusion, is in the distance (arrow). In the foreground are interbedded sandstones and mudstones of the upper shale member of the Aguja Formation (arrow). More resistant sandstone beds form the tops of ledges or 'hogbacks'; in this area beds are dipping shallowly to the north. In the distance, a jeep (arrow), is parked directly above WPA Q uarry #1.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 25

Reproduced with permission of the copyright owner. Further reproduction prohibited withoutpermission. Figure 1.7. Photograph of the Talley Mt. field area, view to the north toward Chisos Mts. Black Gap road (arrow), WPA Quarries 1 and 2, and several of the sampled conglomeratic units are in the foreground.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 27

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.8. Photographs of conglomeratic unit (VL-489/140; arrow), stratigraphic position is shown in Fig. 1.11.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.9. Topographic map of the Talley M t field area showing positions of measured sections (Lehman, 1982 and Sankey, this paper), sampled conglomeratic units, WPA Quarries, and AMNH 3073 crocodile locality.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 760’

Outcrop area of collected conglomerates 2720' ro fS&j Fossil quarries AMNH croc, locality — Dry Creek 0.1 m iles 2720' 100 m 0.1 km Contour interval = 40' 52m

JS-1 contd

L#2 AMNH A _M73

L#3 L#4

L#6 490 2630'

WPA-2

VI- ,491

488

WPA-V

L#7 L#5 L#3

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. facies distributions (Fig. 1.10). This map was compared to an unpublished map of the area made by Lehman (written comm., 1998). The upper Aguja units in the area are within the eastern part of the M arise al Mountain anticline. The area is bordered by two northwest-southeast aligned normal faults, but no faults were detected within the one km square field area. The area is near the northwest base of Talley Mt., an igneous intrusion produced by mid-Eocene volcanism. The southern portion of the area was domed up from this activity. The remainder of the Aguja beds in the field area have been uplifted and slightly tilted (~3 degrees) to the northeast as a result of this

volcanic activity. STRATIGRAPHY

Measured Sections A 52-m stratigraphic section through the upper shale member of the Aguja Formation was measured and described in order to place the

fossiliferous conglomerates and paleomagnetic samples in a stratigraphic fram ework (Fig. 1.11). The facies m ap (Fig. 1.10) also show s the distributions of these units and their stratigraphic relationships. Of the five fossiliferous

conglomerates, three were directly crossed in this section and the other two

were tied to it. Stratigraphy The following discussion is based on Lehman (1982, 1985) and on field observations by Sankey in 1996. The lowest facies is the interdistributary bay and marsh facies and contains interbedded laminated mud-siltstones and fine sandstones with marine invertebrates. This facies only outcrops in the southern part of the field area, the area that has been most domed up by volcanic intrusions. However, there are two places where the contact with

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.10. Fades map of rock outcrops in the Talley Mt. field area (same area shown in Fig. 1.9), from the lower part of the upper shale member of the Aguja Formation. Figure shows the position of measured section (JS-1), location of sampled conglomeratic units and fossil quarries, and the distribution of major channel sand bodies. Offset of JS-1 involves neither loss of section nor overlap. Beds were traced to link the two suitable regions for production of this section. Legend on following page.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. V v V >•> 2 '

V / V ,v / /

/WPA-V'

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LEGEND

Alluvium: Quaternary? . ;o '‘j o-?-o

Alluvium: Early Tertiary?

UNIT 2: Distributary channel, marsh, and floodbasin facies (Lehman, 1982): dominated by large channel bodies of fine to medium sandstones with conglomeratic lags, interbeds of carbonaceous mud-siltsone, and occasional large logs and large bones. Lacks siderite concretions.

Ledge-forming fine-medium sandstones of distributary channels. Many with basal lags of fossiliferous conglomeratic beds (not drawn).

Large fossil log. Not drawn to scale.

^ 3 Type Deinosuchus riograndensis, AMNH 3073 locality. Not drawn to scale.

TMM dinosaur and crocodile isolated bone localities. Bones not drawn to scale.

(2 S ) VL-492 90 cm thick carbonate-cemented, fossiliferous conglomeratic bed at 25 m (JS-1).

(J g ) VL-490 15 cm thick carbonate-cemented, fossiliferous conglomeratic bed at 14.5 m (JS-1).

(2 ? ) VL-491 45 cm thick carbonate-cemented, fossiliferous conglomeratic bed at -13 m (JS-1).

^ VL-489 45 cm thick carbonate-cemented, fossiliferous conglomeratic bed at 25 m level (JS-1). &140 Unsampled carbonate-cemented, fossiliferous conglomeratic beds. Many were not drawn on m ap.

UNIT 1: Interdistributary marsh facies with crevasse splays (Lehman, 1982): ' / ' Carbonaceous siltsones, fine-medium sandstones (burrowed in places), with concretionary horizons, large siderite concretions (1 m diameter), and accumulations of large bones (WPA Quarries #1 & 2).

Large siderite concretions.

80 cm thick concretionary horizon of iron-cemented fine sand with fragments of bone, at 4.5 m (^488) (JS -1).

30 cm thick concretionary horizon of iron-cemented fine sand with large fragments of bone and w ood . At 3.4 m (JS -1 ).

Interdistributary bay and marsh facies (Lehman, 1982): Interbedded laminated mud-siltstones and fine sandstones with numerous invertebrate fossils.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.11. Stratigraphic section (JS-1) through the lower part of the upper shale member of the Aguja Formation in the Talley Mt. field area (see Figures 1.9 and 1.10 for location of section). Figure shows (from left to right), the lithologic unit number (corresponding to facies map, Figure 1.10), the meter level, the position of paleomagnetic samples, the rock grain size, and the position of the sampled fossiliferous conglomeratic units.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Meter Level Grain Size Lithology and Conglomerate Positions Unit & Paleo- magnetics >* i/i V ^ ) a.o § Samples — “ vrt co « ★ Conglomeratic bed collected for fossils (•) o t/i ^ o O. i 1111 i i i i i

■52 ■

- - 5 0 - - 4 8 7 2e -J-46 44 •

4 - 4 2 • Concretionary horizon at 41.5 m. Iron-stained, silt-v.f.ss. • 40 •

4 - 3 8 2d - - 4 - 3 6 • Conglomeratic bed at 35.5 m. 45 cm thick. With clasts of clay. 4 - 3 4 •

- - 3 2

4 3 0 Conglomeratic bed at 29.8 m. 70 cm thick. Several 6 cm thick lenses of carbonate-cemented conglomerate of v. coarse gravel to 2c 28 pebble, with clasts of clay and vertebrate fossils. - - 2 6 * VL-492 Stratigraphic position of conglomeratic bed VL-492 at 25 m. - - 2 4 Collected sample -61 m to NNW of section line.

--22 2b --20 J - - 1 8

- - 1 6 Conglomeratic bed at 14.5 m. 15 cm thick. Concretionary horizon of iron-stained, v.f.ss., with clasts of clay and vertebrate fossils. 2a 414 »*VL-490 Collected sample -30 m to SSE of section line. *VL-491 Stratigraphic position of VL-491 at 13 m. Collected sample -305 -12 m to NNW of section line. 45 cm thick. Carbonate-cemented, with clasts of clay and vertebrate fossils. 4-10 Conglomeratic bed (VL-489 & 140) at 8.0 m. 90 cm thick. 8 I* Carbonate-cemented, with clasts of clay and vertebrate fossils. VL-489 6 Conglomeratic bed (VL-488) at 4.5 m. 80 cm thick. *VL-488 4 Concretionary horizon of iron-stained, fine sandstone with vertebrate bones. 4 - 2 1 Concretionary f.ss. horizon 30 cm thick. Base of section at floor of Quarry WPA-1 at 0 m. With siderite concretions 1 m in diameter.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. the overlying fades is conformable (below VL-491 and below YVPA-1; Fig.

1.10). Overlying this fades is the interdistributary marsh and crevasse splay fades (Unit 1, Fig. 1.10). It is characterized by 1) alternating gray dayshale, carbonaceous silty daystone (with thin ironstone concretionary horizons) and thin beds of lignites and coal, and 2) thin interbeds of lenticular

sandstones which form small hogbacks. This fades contains the Deinosuchus (Crocodyiia) assemblage in the carbonaceous daystones and the Kritosaurus (Dinosauria) assemblage in the carbonaceous daystones assodated with crevasse sandsheets. Above this is the coastal floodplain fades which contains thick deposits of tan and purple daystones and interbedded, lenticular, channelized sandstones (distributary channels). These channels, which can be 4 meters thick and several 100s of meters wide, have erosional bases with conglomeratic lags. This fades lacks abundant plant material, well-developed

lignites, and ironstone concretionary horizons. It contains the Kritosaurus and Unio assemblages (characterized by the freshwater invertebrates, Unio and Vivaparus) and was deposited in streams and overbank areas on the coastal plain, inland from the shore.

The inland floodplain fades is the highest fades in this area. Because it was deposited during the initiation of Laramide tectonism, it formed under

a different tectonic and dimatic setting than the underlying fades. It is recognized by its banded, gray to maroon mudstones with abundant calcareous concretions (paleosol nodules) and fewer channelized sandstones.

This fades contains two faunal assemblages: the Vivaparus and Alamosaurus assemblages and was deposited in a semi-arid, inland

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. floodplain basin (the "Tomillo Basin") in meandering streams and overbank

areas with good soil horizons and abundant caliche. This facies is of particular interest because it contains well-developed paleosols and paleocaliche, which indicate cyclic, seasonal, semi-arid/humid environm ents (Buol et al., 1980 in Lehm an, 1985). Reworked caliche and paleosol nodules are common in the lower facies, especially in the fossiliferous conglomeratic channel lags of the underlying distributary

channels. Their presence indicates that cyclic seasonal climates began earlier (late Campanian) than previously thought (Maastrichtian).

PALEOMAGNETICS Paleomagnetic Sampling and Analyses Oriented samples for paleomagnetic analyses were collected from the fine-grained sedimentary rocks along the 52-meter measured section (Fig. 1.11). One to three samples (87 samples total) were collected at one meter intervals. Samples were progressively stepwise thermally demagnetized (9

steps, 150 to 600° C), and measured in a cryogenic magnetometer at the Paleomagnetic Laboratory at University of Texas, Austin. Paleomagnetic results were inspected in As-Zijderveldt diagrams and in intensity vs. demagnetization plots (Figs. 1.12,1.13, App. I). The primary

component of magnetization was usually best observed after the 300° C thermal demagnetization step. Magnetite was identified as the major carrier

of the remanence because the samples lost almost all of their intensity after exceeding the magnetite Curie point of 580°C (Figs. 1.12 and 1.13). Principle Components Analyses (PCA) was used to identify the characteristic direction of magnetization. This was typically the high-temperature component; when two components existed, the high-temperature component was chosen.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.12. Two examples of the behavior of normal polarity samples (39.1 and 41.3) during progressive thermal demagnetization. Top, As-Zijderveldt diagrams; bottom, intensity vs. demagnetization plots. In As-Zijderveldt diagrams, the y-axis is north/south and up/down and the x-axis is west/east and horizontal. NRM, natural remnant magnetization; 150-600, thermal demagnetization step; squares, inclination; and pluses, declination. Length of axis is intensity; this scale will vary. For more detailed explanations of these diagrams, see Butler (1991). Plots for all other samples are in Appendix 1.

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0 WIS1A40R120NTAL 0 100 200 mprtr (c) perature em T Noartvjp 300 600 ,550 400 500 41 150-450 NRM 600 S s I o s s 0 100 200 e eaue (c) perature Tem HOR TH/UP 300 ■550^ 400 • 600 NRM=2.2x 10'6Am2/kg 350 •450 0 500 400 ua41.3 1 4 guja A 300 150

NRM

600 EAST/HORIZONTAL Figure 1.13. Three examples of the behavior of reversed polarity samples (1.1, 2.1, and 5.1). during progressive thermal demagnetization. Top, As- Zijderveldt diagrams; bottom, intensity vs. demagnetization plots. See Fig. 1.12 for explanations.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A g u ja 1.1 NRM=3.8x10- Am'/kQ

150 NMR

200 300 400 Temperature (c) . . . . c A g u ja 2.1 Ss .S

. o 1 NRIVU7.3 x 10 ' Am'/kg o t 5 5 0 ' f 450 r 400 j

350 t 300V 0 200 V 0 100 200 300 400 500 600 ,150 Temperature (c) ►NRM SOUTWOOWK

A g u ja 5.1 NRM=4.3x10"Am’/kg

1 200-300 3501 5i 400-600 150 5 0 100 200 30G 400 500 600 NRM Temperature (c)

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figures 1.12 and 1.13 are As-Zijderveldt diagram s of good exam ples of normal and reversed polarity samples, respectively. Site averages (based on the high-temperature component characteristic direction) were calculated using Fisher statistics. These data were plotted against stratigraphic level and

the polarity interpretations m ade (Fig. 1.14). Both the declination and inclination site averages were considered in the polarity interpretations. However, more importance was given to the declination values than to the inclination values. This is because at low latitudes (such as Big Bend) the lines of force from the earth's magnetic field are nearly horizontal, resulting in shallow inclinations of the magnetic direction (Lerbekmo, 1997:521). When site averages of declination were between approximately 90 and 270 and site averages of inclination were predominately negative, the section was interpreted as within a reversed polarity zone. When declinations were between -90 and 90 and the inclinations were predominately positive, the section was interpreted as normal. For sites within zones d and e, the site averages of declination and inclination were equivocal. In these cases, the As-Zijderveldt diagrams of the individual samples were inspected to aid with

the polarity interpretations. Each polarity zone has been labeled, a-f (Fig. 1.14). The lowest polarity zone, a, occurs from 0-11 meters and is clearly reversed; b, from 11-14 meters, is dearly normal; c, from 14-16 meters is dearly reversed; d, from 16-28 meters, is probably reversed; e, from 28-38 meters, is probably normal; and f, from 38-52 meters, is dearly normal.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.14. 52-meter Talley Mt. magnetic polarity sequence from the lower part of the upper shale member of the Aguja Formation. Site averages of declination and inclination (based on the high-temperature component characteristic direction) were calculated using Fisher statistics. These data are plotted (dots) against elevation and the polarities were interpreted (center column). Polarity zones are labeled, a-f, and are shown in black, normal polarity; white, reversed polarity; R?, probable reversed polarity; and N?, probable normal polarity. Lithologic section with position of conglomeratic samples is also show.

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Stratigraphic Level (m) elnto Inclination Declination 46 rm Size Gram VL-492 . ® Magnetostratigraphy

Figure 1.15 shows the correlation of the Talley Mt. polarity sequence (from the lower part of the upper shale member of the Aguja Formation) to the base of Chronozone (C) 32 of the geomagnetic polarity time scale of Gradstein et al. (1995). Reversed zone, a, is correlated to C32r.2 and reversed zone c+d is correlated to C32r.l. The normal zone between these two reversed zones is correlated to the short normal zone between C32r.2 and r.l. The highest normal zone is correlated to the normal zone above C32r.l. These correlations constrain the age of the Talley M t polarity section to the late Campanian, approximately between 71.6 and 74.5 Ma. These correlations are constrained by the ages of the Aguja deposits, based on invertebrate and vertebrate biostratigraphy, and are summarized here. Additional discussion on the age of the Aguja is in Rowe et al. (1992). 1) The marine Terlingua Creek sandstone member of the Aguja Formation, which underlies the upper shale member, is middle Campanian in age (Lehman, 1985; Rowe et al., 1992). Of particular im portance is the presence within this unit of Baculites maclearni (Rowe et al., 1992), a zonal index fossil

for the middle Campanian (Obradovich, 1993), with a duration from ~79.6 to

80.2 Ma. 2) The lower portion of the upper shale member of the Aguja Formation is considered to be late Campanian, based on its vertebrate fossils (Rowe et al., 1992). The Terlingua and Talley Mt. local faunas (discussed below), from localities within this unit, contain Judithian mammal taxa (Cifelli, 1995; Rowe et al., 1992; Sankey, this paper; Weil, 1992). The Judithian LMA spans the upper part of C33 and the lower part of C32 (Lillegraven and McKenna,

1986).

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Stratigraphic Level (m) 30 40 20 0 5 10 ri Size Grain VI <88 8 -< I V * *VH90 VI-<92 VL-ie9 VL-O' OAIY CHRONOZONES POLARITY MAGNETOCHRONQ- MAGNETOCHRONQ- 49 STRATIGRAPHY 70 0 - 80 75 TIME (Ma) MAASTRICHTIAN CAMPANIAN (±0.1)- 0 . 5 6 - STAGES 8. (±0.5)- •83.5 7. (±0.5)- ■71.3 tc « . L C UJ CC o UJ

These three points constrain the magnetostratigraphic correlation to within the late Campanian, and within this time, the base of C32 is the only polarity zone known to contain two closely-spaced reversed zones of short duration. The presence of Judithian mammal taxa within the Talley Mt. and Terlingua local faunas, further support this correlation. Lehman (1991:15) estimated that the sedimentation rates for the upper shale member of the Aguja ranged from 10-21 m/My), and averaged -13

m/My. He attained these age estimates using paleomagnetic stratigraphy and biostratigraphic correlation of vertebrate faunas from the latest Cretaceous through Early Tertiary units in Big Bend (from Rapp et al., 1983; Standhardt,

1986; and Schiebout et al., 1987). Although no paleomagnetic correlations

had been done on the Aguja Formation at the time of Lehman's (1991) work, his age estimates for the Aguja's sedimentation rates were based on its vertebrate fossils and on extrapolation of the magnetostratigraphy from the younger units.

Applying Lehman's (1991) estimated rates of sedimentation, the following range of values for the Talley Mt. polarity section were acquired

(Table 1.1). Based on Gradstein et al. (1995), the approxim ate duration of the normal polarity zone between C32r.2 and C32r.l is 0.2 My. When this value (0.2 My) is used to calculate sedimentation rates during polarity zone b (3 m), an estimated rate of 15 m/My) is acquired. This rate is very similar to Lehman's (1991) average rate of sedimentation (13 m/My). Using this rate of sedimentation (13 m/My), the approximate duration of the two reversed polarity zones (a and c+d) is -0.8 and 1.1 My, respectively

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (Table 1.1). However, the duration of C32r.2 and 32r.l is considerably shorter (-0.3 and -0.4 My, respectively; Gradstein et al., 1995). This suggests that sedimentation rates were considerably higher than 13 m/M y in this area. For

polarity zone a, sedimentation rates were at least -37 m/My, and for polarity zones c+d, sedimentation rates were at least -35 m/M y. A revised sedimentation rate (29m/My) was calculated by averaging the rates from

three parts of the section (a, 37; b, 15; and c+d, 35 m/M y; Table 1.1).

Table 1.1. Estimates of the duration (My) for the Talley M t polarity sequence (lower part of the upper shale member of the Aguja Formation) based on four rates of sedimentation (Lehman, 1991:15 and Sankey, this paper).

Sedimentation Duration Duration Duration Duration Duration Duration rates (My) (My) (My) (My) (My) (My) (m/My) for entire for 20 m, for for for for 52 m between polarity polarity polarity polarity section VL-488 zone a zoneb zone c+d zone e+f and 492 (11 m) (3 m) (14 m) (24 m)

10 (Lehman, 1991) 5.2 2.0 1.1 0.3 1.4 2.4 13 (Lehman, 1991) 4.0 1.5 0.8 0.2 1.1 1.8 21 (Lehman, 1991) 2.4 0.9 0.5 0.1 0.7 1.1 29 (this paper) 1.8 0.7 0.4 0.1 0.5 0.8 Table 1.2 shows age estimates for all the sampled conglomeratic units,

based on sedimentation rates from (Lehman, 1991) and Sankey (this paper) and on the datum , VL-491 (-74 Ma). VL-491 was chosen as the datum because

it is stratigraphically closest (within 1 meter) to the boundary between normal

(b) and reversed (c) polarity zones. This base of zone c is correlated to the base of C32r.l, which is -74 M a (Gradstein et al., 1995). Using the slower sedimentation rate (13m/My; Lehman, 1991), the conglomerates range from -74.6 to -73.1 Ma, with -1.5 My duration between

the lowest and highest conglomerates, and with -4 My duration (-71 to 75 Ma) for the entire 52 meter section. Using the faster sedimentation rate (29

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. m/M y; Sankey, this paper), the conglomerates range from 74.3 to 73.6 Ma, with -0.7 My duration between the lowest and highest conglomerates, and with 1.8 My duration (-72.7 to 74.5 Ma) for the entire 52 meter polarity section. Although these two groups of values are similar, I will be using the latter group in this paper.

Table 1.2. Age (Ma) estimates for the Talley M t conglomeratic units based correlation of polarity zone, c, to C32r.l (-74.0 Ma; Gradstein et al., 1995) and rates of sedimentation from Lehman (1991) and Sankey (this paper).

Conglomeratic Meter Polarity Polarity Sub- Approx. Approx. Approx. unit level zone chrono- age (Ma) age (Ma) age (Ma) zone of sub- (based on (based on chronozomsed. rate sed. rate 13 m/My 29 m /M y Lehman, Sankey, 1991) this paper) Top of section 52.0 f N - 71.6-73.6 71.0 72.7 VL-492 25.0 d R? C32r.l 73.6-74.0 73.1 73.6 (0.4 My) VL-490 14.5 c R C32r.l n 73.9 73.9 VL-491 13.0 b N - 74.0-74.2 74.0 74.0 (02 My) VL-489/140 8.0 a R C32r.2 742-74.5 74.4 74.2 (03 My) VL-488 4.5 a R C32r.2 it 74.6 74.3 Bottom of 0.0 a R C32r.2 it 75.0 74.5 section (WPA-1) THE TALLEY MOUNTAIN LOCAL FAUNA Vertebrate Fossil Collection and Processing Fossiliferous carbonate-cemented conglomerates in channel lag deposits of large channels are very common in the upper shale member of the Aguja in this field area. Five particularly rich units were sampled for fossils (Figs. 1.16-1.17). Bulk samples (-1753.4 kg total) of the conglomeratic beds were collected in order to get a representative sample of the vertebrates. They were collected from five closely-spaced horizons (less than 20 m) tied to

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.16. Photographs fossiliferous conglomeratic rocks (VL-488, 489, and 140). Left, uncut; right, cut. Stratigraphic positions are show n in Fig. 1.11.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. = /.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.17. Photographs of fossiliferous conglomeratic rock (VL-491 and 492). Left, uncut; right, cut VL-490 (with large fragment of turtle carapace, LSUMG 490:5531), bottom left; VL-492 (with large fragment of turtle bone, LSUMG 492:6171), bottom right.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 56

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. a 52 m measured section. Amounts of rock collected from each horizon are shown in Appendix EL A small amount of the collected rocks were kept for

voucher samples (123.9 kg), and the remainder (1,630.5 kg) were disaggregated

in dilute acetic add, screened, and picked (Fig. 1.18) for small vertebrate fossils. All fossils have been catalogued within the LSUMNS, and detailed locality descriptions are on file there. Typically, a 25% solution of acetic add was used to break down the rocks. Lower and higher concentrations were tried, but 25% was found to be the most time and cost effective, while still not harming the fossils. Rocks were removed from the add solution every one to four weeks, rinsed in

water, and returned to a new add solution. We also experimented with the length of time rocks were soaked in add and found that changing the solution every one to two weeks was the most effective. The resulting residue from the rocks was screened through two sizes of screens (Tyler Standard Screen, 9-mesh, with 2 mm wide openings; and USA Standard Screen, 30-mesh, with 1 mm wide openings). The 9-mesh matrix was picked for fossils and then returned to soak in the add solution to break down

further. The dried 30-mesh matrix was weighed and fossils were picked out

under a microscope. It took two years to disaggregate all of the rocks and over

361 hours to pick all the 30-mesh matrix. Sedimentology of Fossiliferous Conglomerates Five fossiliferous conglomerates were sampled. Of these, the lowest

(VL-488; Fig. 1.16) is distinct from the others. Although its original stratigraphic thickness cannot be determined because it now occurs as a surface rubble, Lehman (1982) considered it part of a crevasse splay. It is a

concretionary horizon of iron-oxide stained, fine-medium sands, with large

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.18. Conglomeratic rock soaking in acetic add solution, left. Fossiliferous matrix (right) resulting from add treatment of conglomerate (VL-491) and screening residue through a 30-mesh Tyler Sieve.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ^10

* » ,

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. vertebrate fossil fragments and occasional small vertebrate fossils. This conglomeratic unit was the most difficult to break down in acetic acid because

it is more iron-cemented than the others. It was the least fossiliferous of all five. The other four conglomerates (VL-489/140, 491, 490, and 492; Figs. 1.16- 1.17) are lag deposits of large channels, are less than ~ 0.5 meter thick, and less than 15 meters wide. The conglomerates are carbonate-cemented and contain numerous large clasts of clay, pedogenic nodules, many small vertebrate bones and teeth, and occasional large fragments of wood and large vertebrate bones and teeth. Although these rocks are technically sandstone conglomerates, I use the terms, conglomerates and conglomeratic units.

The presence of these conglomeratic deposits (with such large clasts) suggest that these deposits may have formed quickly, possibly as storm

deposits. The abundance of the pedogenic nodules indicates that conditions suitable for development of soil horizons occurred nearby. The channels themselves may represent major down-cutting events in the area, possibly due to a drop in base level. Taphonomic and Sampling Biases Taphonomically, the conglomerates produce a biased sample of

vertebrate fossils due to their having been transported in a fluvial system.

The samples are biased towards small, durable vertebrate fossils, within the size range of small shark and mammal teeth (usually less than 4 mm in

length) and against anything much larger. Although pieces of larger bone and teeth are present in the conglomerates, they are usually too broken for identification. Additionally, bias may have been introduced with the use of acid-

processing and screening. Although rocks were inspected for larger bones

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. and teeth (and some were found in this manner, for example a tooth of Deinosuchus riograndensis LSUMG 488:5484; Fig. 1.23 A) during acid processing and screening, some of these fossils may have been missed and

destroyed because they broke up during soaking. Another bias introduced into this collection was in sampling methodology. Very different quantities of conglomeratic rock were collected and processed from each horizon (Appendix II): VL-488 (281 kg); VL-140/489 (-553 kg); VL-491 (304 kg); VL-490 (18 kg); and VL-492 (474 kg). This sam ple

size difference should be kept in mind when interpreting the presence or absence of taxa. Vertebrate Paleontology Thirty six taxa (mostly small vertebrate teeth and bones) have been recovered from the five conglomeratic horizons, including two new lizard

records for the Aguja Formation (Table 1.3). Table 1.4 lists the taxa from both the Talley Mt. and Ter lingua local faunas. Identifications of the Talley Mt.

fauna were made by comparisons to descriptions and illustrations in the literature and to museum collections. Detailed descriptions of these taxa are in the following three papers.

The following summarizes the taxa recovered, focusing on how the assemblage compares to the Terlingua fauna, and their paleoecological

significance, and distributional trends within the sampled 20-m section. Chondrichthyes—Eight chondrichthyan taxa have been recovered. They are Hvbodus sp., Lissodus (Lonchidion) selachos. Scapanorhvnchus texanus. Squatirhina americana. Ischvrhiza avonicola. Onchopristis dunklei. Ptychotrvgon sp., and Dasyatidae-indeterminate (Fig. 1.19).

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 13. Vertebrates from the Talley M t local fauna, based on conglomerate samples only. First occurrences in the Aguja Formation marked by (*).______Taxa VL- VL- VL- VL- VL- 488 489 & 491 490 492 140 Chondrichthyes Hybodus sp. X - --- Lissodus (=Lonchidion) selachos X X XX X Scapanorhvnchus texanus - X --- Squatirhina americana - X XX -

Ischyrhiza avonicola - X X --

Onchopristis dunklei - X XX -

Ptychotrygon sp. - X X - X

Dasayatidae X X XX - Fish Lepisosteus occidentalis X X XXX Phyllodontidae-indet. X X --- A m phibia

Albanerpeton sp. - X X --

Scapherpeton sp. - X --- Anura-indet. - XX - X Chelonia

T rionychidae-indet. - X X X X Squamata

Glyptosaurinae-indet. — X — — — *Chamops — X ——— Teneteius sp. nov. — — — — X

Teiidae-indet. — X ———

Squamata-indet. X X — — — Crocodylia

Goniopholidae-indet. X X --- Deinosuchus riograndensis X X - - - cf. Brachvchampsa X XX - X (Table 1.3 continued)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Crocodylian-indet. (A) X X X - X Crocodylian-indet. (B) X X X X X DINOSAURLA Omithischia Omithopoda-Hadrosauridae — XX X — Ceratopsia-Ceratopsidae X — — — X Omithischia-indet — X — — X Saurischia Tyrannosauridae-indet. — X — — — Troodon — X — — —

Sauromitholestes XXX — X

Richardoestesia — X — — X Theropoda-indet. XXX — — M am m alia Multi tuberculata Cimolomvs sp. — X — — — Meniscoessus sp. —— X — — *cf. Cimexomvs — X — — —

Paracimexomvs sp. — XX — —

Multituberculata-indet. X X — — — Marsupialia

Alphadon cf. A. sahnii — X — — —

A lphadon cf. A. hallevi — — — — X

Marsupialia-indet. — X — — X

Mammalia-indet. X X X — X

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table 1.4. Vertebrates of the Terlingua (Rowe et al., 1992; Weil, 1992; Cifelli,

Taxa Terlingua Talley Mt. local fauna local fauna Chondrichthyan

HybodMS sp. X X

Lissodus (=Lonchidion) selachos X X

Scapanorhynchus texanus -- X

Scapanorhvnchus sp. X —

Squatirhina americana X X

Ischyrhiza avonicola X X

Onchopristis dunklei X X

Ptyghptrygpn sp. X X

D asyatidae X X Fish

Lepisosteus occidentalis — X

Lepisosteidae-indet. X X

Amiidae-indet. X —

Phyllodontidae-indet. X X Am phibia

Albanerpeton sp. X X

Scapherpeton sp. — X

Scapherpetontidae-indet. X —

Anura-indet. X X Chelonia

"Aspideretes" X --

"Baena" X —

T rionychidae-indet. X X Squamata

Odaxosaurus piger X —

Glyptosaurinae-indet. X X

Xenosauridae-indet. X --

cf. Paleosaniwa canadensis X —

cf. Parasaniwa X —

Anguimorpha-indet. X — (Table 1.4 continued)

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Serpentes-indet. X --

Chamops — X

Peneteius sp. nov. — X

Teiidae-sp. nov. B X X

cf. Teiidae-sp. nov. Y X —

Teiidae-indet. X X

Squamata-indet. X X Crocodylia

Goniopholidae-indet. X X

Deinosuchus riograndensis X X

cf. Brachvchampsa — X

Crocodylian-indet. X X

Pterosauria X — DINOSAURIA Ornithischia

Ankylosauria X --

Hadrosauridae X X

Ceratopsidae X X

T yrannosauridae X X

cf. Troodon X X

cf. Sauromitholestes X X

cf. Dromaeosaurus X --

cf. Ricardoestesia X X M ammalia Multi tuberculata

Cimolomvs clarki X —

Cimolomvs sp. -- X

Meniscoessus sp. — X

Meniscoessus sp. nov. X --

Cimolodon cf. electus X —

Qmolodon sp. nov. X --

cf. Cimexomys -- X

Paracimexomvs sp. X X (Table 1.4 continued)

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Multi tuberculata-indet. XX

T ribosphenida- X -- Order and Family uncertain PaleomoloDS lanestoni Marsupialia

Alphadon cf. A. sahnii X X

Alphadon cf. A. hallevi X X

Alphadon perexiguus X --

Turgidodon cf. T. lille^raveni X —

Pediomvs cf. P. krejcii X —

Marsupialia-indet. X X Eutheria- Order and Family uncertain

Gallolestes aeuiaensis X —

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.19. Chondrichthyan teeth from the Talley Mt. local fauna: A. Hvbodus sp. (LSUMG 489:5627); B. Lissodus selachos (LSUMG 491:5965, top; 489:5692, bottom); C. Scapanorhvnchus texanus (LSUMG 489:5666, bottom; 489:5626, top); D. Onchopristis dunklei (LSUMG 489:5667); E. Ischvrhiza avonicola (LSUMG 491:5977); F. Squatirhina americana (LSUMG 489:5689); G. Ptychotrvgon sp. (LSUMG 489:5670); H. Chondrichthyan dermal denticle (LSUMG 140:6163); I. Dasyatidae (LSUMG 489:5648).

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. This assemblage is very similar to that of the Terlingua (Rowe et al., 1992). Two of the sharks (Hvbodus sp. and Scapanorhvnchus texanus). are considered to be mainly shallow marine taxa (Welton and Farish, 1993) and

only occur in the lowest two conglomerates. The other shark, Lissodus (=Lonchidion) selachos, considered to be a brackish water taxon (Estes, 1964), is present in all the conglomerates, but only one tooth has been found from

the highest conglomerate. Acintop terygians—Lepisos teus occidentalis. gar and an indeterminate phyllodontid were recovered from the conglomerates (Fig. 1.20); this fish assemblage is similar to that of the Terlingua local fauna. L. occidentalis. commonly found in fluvial channel fills and considered to be brackish to

freshwater taxon (Bryant, 1989), is much less common in the highest

conglomerates. Amphibia—Two salamanders (Albanerpeton sp. and Scapherpeton sp.) and one frog (genus indeterminate) have been recovered from the conglomerates (Fig. 1.21) and these groups are also present in the Terlingua fauna (Rowe et al., 1992).

Chelonia—Fragments of trionychid turtle carapaces were found from all of the conglomerates, but are uncommon; further identification could not be made with this material (Fig. 1.22). Trionychids were also recovered from

the Terlingua local fauna (Rowe et al., 1992). Modem trionychids live in aquatic environments. Their scarcity in the Talley Mt. fauna is probably due

to the taphonomic bias against large sized vertebrate fossils in the conglomerates. Squamata—Several lizard taxa were recovered from the conglomerates

(Glyptosaurinae-indet., Chamops. Peneteius sp. nov., and Teiidae-indet.; Fig.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.20. Actinopterygians from the Talley Mt. local fauna: A. Lepisosteus complete tooth (LSUMG 488:5521); B. Lepisosteus tooth caps (LSUMG 140:6127, left; 6128, right); C. Lepisosteidae scale (LSUMG 489:5732); D. Indeterm inate fish vertebrae (LSUMG 140:6144); E. Phyllodontid tooth plates (LSUMG 489:5577).

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1mm

e IE

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.21. Amphibian and lizard fossils from the Talley Mt. local fauna: A. Albanerpeton sp. maxilla, lingual view (LSUMG 491:5958); B. Scapherpeton sp. dentary, lingual view (LSUMG 489:5694); C. Glyptosaurinae indet., maxilla, lingual view (LSUMG 140:6106); D. Teiidae-"Species B" (Miller, 1997), tooth (LSUMG 489:5656); E. Chamops mandible, labial view (LSUMG 140:6104); F. Peneteis sp. nov., tooth, lateral and occlusal views (LSUMG 492:6253).

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1mm

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.22. Turtle carapace fragment from the Talley Mt. local fauna (LSUMG 492:5533).

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1.21), but far fewer taxa than from the Terlingua. Both Chamops and Peneteius sp. nov. have only been recovered from the Talley Mt. fauna and are new records for the Aguja. Lizards are rare and were only recovered from the lowest two conglomerates (with the exception of Peneteius sp. nov. from the highest conglomerate). This is probably due to the different taphonomic histories for the Terlingua and Talley M t faunas. Because lizard jaws and

teeth are so fragile, most were probably destroyed during transport.

Additionally, no glyptosaurine osteoderms (the most common lizard element found from the Terlingua; Rowe et al., 1992) have been found from the conglomerates. This is also probably due to taphonomy: osteoderms are

larger than most of the fossils recovered from the conglomerates. Crocodylia—Several crocodylian taxa were recovered from the conglomerates (an indeterminate goniopholidae, Deinosuchus riograndensis.

Brachvcham psa ?, and two indeterm inate crocodylians; Fig. 1.23). This assemblage is very similar to that of the Terlingua (Rowe et al., 1992). Crocodylians, which live in aquatic areas, have been recovered from all the

conglomerates, but are more common from the lowest ones.

Dinosauria—Both herbivorous and carnivorous dinosaur (small shed teeth and juvenile teeth) have been recovered from the conglomerates (Hadrosauridae-indet., Ceratopsidae-indet., Tyrannosauridae-indet., Troodon.

Saurom itholestes. and Ricardoestesia: Figs. 1.24 and 1.25). This assem blage is very similar to that of Terlingua (Rowe et al., 1992). The hadrosaurs in the Talley Mt. fauna provide an interesting taphonomic story. Only the small teeth of juvenile (or younger) hadrosaurs have been recovered. Yet hadrosaurs are the most common dinosaur from the Terlingua (based on teeth), and from the Aguja in general (based on large

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.23. Crocodylian fossils from the Talley Mt. local fauna (lateral views): A. Deinosuchus riograndensis teeth (LSUMG 489:5672; 488:5484); B. Goniopholid indet. teeth (LSUMG 489:5673, left; 5608, right); C. cf. Brachvchampsa teeth (LSUMG 491:5621, left; 140:6125, middle; 489:5658, right; lateral views and occlusal views); D. Croc, indet-type B teeth (LSUMG 140:5564, left; 489:5697, right); E. Croc, indet. type A teeth (LSUMG 488:5496, occlusal and lateral); F. Croc, indet. scutes (LSUMG 489:5582, left; 140:6136, right).

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. m

an ok f t

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.24. Dinosaur teeth from the Talley Mt. local fauna. A. Hadrosaurid (juvenile) tooth (LSUMG 489: 5538, occlusal view); B. Ceratopsian tooth fragment (LSUMG 488:6230, occlusal view); C. Tyrannosaurid tooth, close-up of denticles (LSUMG 489:5580); D. Troodon tooth, left (lateral view); close-up of denticles, right (LSUMG 140:6117); E. Sauromitholestes tooth, left (lateral view); close-up of denticles, right (LSUMG 488:5483); F. Sauromitholestes tooth, lateral view (LSUMG 140:6139); G. Sauromitholestes tooth left (lateral view); close-up of denticles, right (LSUMG 489:5659).

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.25. Dinosaur teeth from the Talley Mt. local fauna. A. Richardoestesia tooth, left (lateral view); dose-up of dentides, right (LSUMG 489:6238); B. Richardoestesia tooth, left (lateral view); dose-up of denticles, right (LSUMG 489:6239).

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. bones). Their presence in the conglomerates is probably a factor of size sorting: only these small teeth were small enough to survive transport without destruction beyond recognition. Larger teeth could have been

deposited elsewhere. Mammalia—Mammal fossils are rare, but have been found from all of

the conglomerates (except VL-490), and are most common in the second

lowest conglomerate (VL-489/140). Multituberculate (Cimolomvs sp., Meniscoessus sp., cf. Cimexomvs. Paracimexomys sp., and cf. Paracimexomvs) and marsupial (Alphadon cf. A. sahnii and A. cf. A. hallevi) mammal teeth were recovered from the conglomerates (Fig. 1.26). All of the these taxa are known from the Terlingua

local fauna, but the Talley Mt. assemblage is much less diverse and abundant (400 multituberculate teeth were recovered from the Terlingua; Weil, 1992). The Terlingua mammalian assemblage is considered to represent part of the Judithian LMA (Rowe et al., 1992). However, because it contains species only found from the Big Bend area and does not contain many taxa found in similar faunas to the north, it is considered to be very endemic (Rowe et al.,

1992; Weil, 1992; Cifelli, 1995). DISCUSSION

T he Talley ML Local Fauna The taxonomic composition of the Talley Mt. local fauna is very similar to that of the Terlingua, and both have mammalian taxa that are present in Judithian faunas to the north. There are no taxa present in the Talley Mt. local fauna which indicate a different age from the Terlingua. The main difference between the two faunas is a result of the different depositional environments sampled and their differing taphonomic

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1,26. Mammal teeth from the Talley Mt. local fauna (occlusal views). Multi tuber culates (A-E): A. Cimolomvs sp. M l (LSUMG 489:5681); B. Meniscoessus sp. Ml (LSUMG 491:5779); C. Cimexomvs sp. Lml (LSUMG 140:6121); D. Paradmexomvs sp. M2 (LSUMG 491:5778); E. Paracimexomvs sp. PM3 (LSUMG 489:5684); Marsupials: F. Alphadon cf. A. hallevi LM3 (LSUMG 492:6252); G. Alphadon cf. A. sahnii M2 anterior fragment (LSUMG 489:5679).

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. histories. An additional important difference is the amount of rock processed from each area. Two tons (1,814 kg) were collected from one unusually rich site from the Ter lingua area (A. Weil, oral comm., 1996), which is similar to the amount sampled for all the Talley Mt. conglomerates

combined (1,630 kg processed). The Terlingua site produced hundreds of vertebrate fossils of various sizes. Because of this abundance of fossils representing many size categories,

a greater diversity of taxa (52) are present in the Terlingua. Also important,

the Terlingua preserves remarkably fragile fossils, such as pterosaur bones. Terlingua's higher taxonomic diversity is a direct result of more fossils collected, so that even very rare taxa are represented in the sample. In contrast, the Talley Mt. local fauna was sampled from five stratigraphic levels of conglomeratic rock. Fluvial sorting and transport produced a collection of vertebrate fossils only within a small size range and

with a high level of durability. As a result, the conglomerates produced fewer total fossils and a lower diversity of taxa. Few rare taxa were probably

sampled in the conglomerates. Despite the taphonomic 'disadvantage' of sampling conglomerates,

one clear advantage stands out: they provide the ability to sample from similar depositional environments at multiple stratigraphic levels. Assuming the magnetostratigraphic correlations and estimated rates of sedimentation are correct, then -0.7 My elapsed between deposition of the lowest and highest conglomerates. If there was environmental change during this period of time, then faunal change through the section should reflect this.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The most obvious change occurred in the aquatic taxa (chondrichthyans, actinopterygians, and salamanders): they dramatically decrease upsection and are extremely rare or absent in the highest

conglomerate. The environmental change recorded is: a more aquatic environment with a stronger marine influence lower in the section, and a

less aquatic environment with a weaker marine influence higher in the section. This change was probably due to the marine regression from the area and to overall drier conditions present, even low on the coastal plain. A change within the more terrestrial vertebrates is more difficult to discern, especially given the taphonomic and sampling problems involved. However, within the taxa that preferred aquatic environments (such as the

crocodylians), a similar decrease upsection occurs. Despite the small sample of mammals, two observations can be made. First, although considerably fewer multituberculate fossils were found compared to marsupials, a higher diversity of multituberculates than marsupials is represented, possibly reflecting a greater taxonomic diversity among the multituberculates during this time. Second, only marsupials

were found from the highest conglomerates, possibly reflecting a habitat preference to the less aquatic environments higher in the section. This interpretation is supported by the fact that more multituberculates them marsupials were recovered from the Terlingua, considered to be within an

estuarine setting. The vertebrate distribution patterns within the section suggest the following paleoenvironmental interpretations. The lower conglomerates

(VL-488, 489/140, 491, 490) contain more aquatic taxa (including shallow marine taxa) than the highest conglomerate (VL-492). This ~0.7 My interval

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. records the effect of the marine regression from the area, from a marine influence low in the section to very little influence higher in the section. This supports Lehman's (1982) interpretations that this area was within a

coastal lowland environment similar to those on the coast of Texas and Louisiana (Fig. 1.27), and that facies changed upsection to more terrestrial

settings with drier conditions. In particular, Lehman (1982) suggested that the stratigraphically lowest deposits in the area (below the WPA quarries) were interdistributary bay and marsh facies, with a stronger marine influence than all the others facies above it. He considered deposits above this (which include the WPA dinosaur quarries and the lowest four conglomerates) to be interdistributary marshes, with crevasse splays near the base. The higher portion of the section (which includes the AMNH crocodile quarry and the highest conglomerate) he considered to be distributary channel, marsh, and floodplain facies (Lehman, 1982). The paleoenvironmental significance of the fossils described here fit Lehman's (1982) paleoenvironmental interpretation of these deposits.

However, the abundance of the pedogenic conglomerates, even in the lower

portion of the section, suggest a modification first proposed by Davies and

Lehman (1989) to explain the dinosaur bonebeds in the area. This suggestion was that the area experienced periodic droughts during which the marshes dried up or were significantly reduced. A drier environment (at least for certain parts of the year) would also explain the presence of large pedogenic nodules in the conglomerates. Clearly, good soil horizons were able to develop nearby. The presence of the conglomerates themselves may also be a paleoenvironmental hint: during droughts, heavy rainstorms could cause

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 1.27. Modem coastal and swamp environments in southeastern Texas (near Galveston) are probably analogous to portions of the upper Aguja Formation. Top photographs, a coastal environment with salt to brackish water. Bottom photograph, swamp environment with brackish to fresh water. Photographs by Sankey (1998).

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 90

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. soil erosion, and soil nodules and fossils could be transported and deposited

to form conglomerates in the base of the stream channels. Correlation to other Judithian-age faunas The Judithian LMA was described and reported from the Judith River Formation, Montana (Lillegraven and McKenna, 1986; Montellano, 1992; Sahni, 1972), the Two Medicine Formation, Montana (Montellano, 1992), and the "Mesaverde" Form ation, W yoming (Lillegraven and M cKenna, 1986). Although there has been difficulty dearly assigning a Judithian LMA to faunas further to the south, the following formations are thought to contain Judithian LMA faunas: Kaiporowits Formation, Utah (Cifelli, 1990a, 1990b; Eaton, 1987); the Fruitland/Kirtland Formations, New Mexico (Clemens, 1973; Flynn, 1986; Rigby and Wolberg, 1987), but for dissenting views of this age, see Lillegraven and Ostresh (1990; Rowe et al., 1992); the "El Gallo Formation", Baja California (Lillegraven, 1972, 1976); and the upper Aguja Formation (Cifelli, 1995; Lehman, 1991; Rowe et al., 1992; W eil, 1992). Two Judithian age mammal-bearing horizons from the Judith River

Formation in northern Montana (Goodwin and Deino, 1989; Montellano,

1992) have been bracketed by radioisotopic dates to -78.0 to 79.5 Ma (Goodwin and Deino, 1989). These deposits also correlate with the middle lithofades of the Two Medicine Formation and with the Taber Coal Zone of southern Alberta (Eberth, 1990; Eberth and Hamblin, 1993). The age of the Judith River (Oldman Formation) deposits in Dinosaur Provindal Park, Alberta, range from -76.5 to 74.5 Ma (Eberth et al., 1992; Thomas et al., 1990). The age of the Two Medidne Formation, Montana, has been refined by 40Ar/39Ar dating of

four bentonites and one tuff, to -78 to 71 Ma (Rogers et al., 1993). Mammal localities of Judithian age occur in the middle lithofades suite of the

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. formation. Other vertebrate assemblages (Homer, 1989) occur in the upper

lithofades (-upper 280 m; Lorenze, 1981) and are approximately contemporaneous with faunas from Dinosaur Provincial Park, Alberta

(Rogers et al., 1993). CONCLUSIONS The Talley Mt. local fauna is the second late Campanian

microvertebrate fauna to be described from the Big Bend area. It contains 35 vertebrate taxa, inducting two new lizard records for the Aguja Formation and several Judithian mammal taxa, and is assigned to the Judithian LMA. Along with the Terlingua local fauna, which it is similar to, it is one of the southern-most Judithian faunas in North America. The paleomagnetic polarity sequence has been correlated to the base of Chronozone 32 (Fig. 1.15). The age of the sampled 20-m section can be

constrained to -73.6 to 74.3 Ma; and 0.7 My occurred between the lowest and

highest conglomerates. This magnetostratigraphy has provided the first non- paleontologic age control for the lower portion of the upper shale member of the Aguja Formation and for the vertebrate fossils from both the Talley Mt.

and Terlingua local faunas. The Talley Mt. local fauna, which was derived from five conglomeratic horizons which span -0.7 My, reflects an environmental

change in the area due to the marine regression. Distinct dry seasons, during which marshes dried up or were reduced and good soil horizons could form, occurred during this time. Flooding events also occurred, during which soils were eroded, transported with bones and teeth, and deposited in stream

channels.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The Talley Mt. and Terlingua local faunas are both from the lower portion of the upper shale member of the Aguja Formation, from deposits formed within a coastal lowland setting, and contain similar vertebrate taxa. Taphonomic and sampling biases produced two very different assemblages. The Terlingua local fauna, collected from an estuarine deposit, has more total fossils, more size categories represented, more fragile specimens, and a higher taxonomic diversity (52). The Talley Mt. fauna, collected from fluvial conglomerates which span 0.7 My of environmental change, contains fewer total fossils, primarily durable fossils less than 4 mm in length, and a lower

taxonomic diversity.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHONDRICHTHYANS AND ACTINOPTERYGIANS OF THE TALLEY MT. LOCAL FAUNA, UPPER AGUJA FORMATION (LATE CAMPANIAN), BIG BEND NATIONAL PARK, TEXAS INTRODUCTION The chondrichthyan and actinopterygian fauna are described from the late Campanian Talley Mt. local fauna of Big Bend National Park, Texas. The fauna was collected from the lower portion of the upper shale member of the Aguja Formation. Fossils were collected by bulk sampling five horizons of carbonate-cemented, pedogenic-nodule conglomeratic beds. Magnetostratigraphic correlations constrain the fauna to base of Chronozone

32. Approximately 0.7 My occurred (~73.6 to 74.3 Ma) between the lowest and highest conglomerate.

Previous environmental interpretations for the Aguja deposits in the area had suggested that the deposits had formed in a coastal setting, ranging

from interdistributary marsh-bay facies at the base of the exposed section to inland floodplain facies at the top (Lehman, 1982, 1985). The five horizons sampled are from within the lower portion of the section. The

chondrichthyans and actinopterygians are used to provide more detailed

paleoenvironmental information for these deposits than was previously available.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SYSTEMATIC PALEONTOLOGY Class CHONDRICHTHYES EUSELACHII

HYBODONTOIDEA Family HYBODONTIDAE HYBODUS sp. (Fig. 1.19 A) Referred specimens—LSUMG 488:5566; 489:5627. Description—V-5566 is a tooth missing its root, lateral cusps, and apical

end. The tall median cusp contains faint longitudinal ridges which extend apically from the crown base. The cusp is 2 mm long, but because it is broken

at the apical end, it would have been longer. A small, lateral cusplet was present, but during preparation was broken and destroyed. V-5627 is a larger, broken tooth, with only a partial (3 mm long) median cusp. The cusp has

strong longitudinal ridges at its base. Comparisons and Discussion—Tooth compares very well to Hybodus sp. from the Terlingua local fauna illustrated in Rowe et al. (1992:477) and to descriptions and illustrations in Welton and Farish (1993:49). Only two teeth of Hybodus sp. have been recovered from the Talley Mt. local fauna; the teeth were found from the stratigraphically lowest

conglomeratic beds in the section (VL-488 and 489). Modem hybodontid

sharks live in marine or brackish water environments, but little is known

about the paleoecology of Hybodus sp. If it had an ecology similar to modem

hybodontid sharks, then its rarity in the Talley Mt. local fauna suggests a weak marine influence in this area. The single Hybodus occurrence low in the section suggests that there was a slightly greater marine influence lower

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. in the section. Rowe et al. (1992:477) report that teeth of Hybodus sp. are relatively abundant in the Terlingua local fauna, further indicating that the Terlingua (considered to be from an estuarine deposit) was under more marine influence than the Talley Mt. local fauna. Family POLYACRODONTIDAE LISSODUS (LONCHIPION) SELACHOS (Fig. 1.19 B)

Referred specimens—LSUMG 488:5490,5498,5528; 140:6118,6166; 489:5649,5692,5698,5735; 491:5945,5954,5965; 490:5625; 492:6245, Description—Teeth are missing roots and most of the tooth crowns are broken. Tooth crowns are small, short, and wide mesially-distally. Crowns have a prominent labial protuberance and a continuous, crenulated, and cusped transverse cutting ridge. A complete crown (491:5945) has the following measurements: 2.5 mm in mesial-distal width, 1 mm in anterio posterior width, and 0.75 mm in basal-apical width.

Comparisons and Discussion—Teeth compare very well to descriptions and illustrations of this species from the Aguja Formation (Rowe et al.,

1992:477; Welton and Farish, 1993:54), from the Late Cretaceous Lance

Formation, Wyoming (Estes, 1964:7), and from the Late Cretaceous Hell Creek

Formation, Montana (Bryant, 1989:10). Teeth from L. selachos are common in the Talley Mt. local fauna, and occur in all the conglomeratic horizons sampled. However, only one tooth has been recovered from the highest

conglomerate (VL-492). Although modern hybodontid sharks live in marine or brackish water environments, little is known about the paleoecology of L. selachos. Estes (1964:159) and Capetta (1987:24 and 36) considered L. selachos to be a

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. fresh-water inhabitant and Standhardt (1986:76) reported it from a freshwater deposit in the uppermost Aguja Formation (LSUMG VL-113). Rowe et al. (1992:477) recovered hundreds of teeth from this taxon from the Terlingua local fauna, which is considered to represent an estuarine environment. It is likely that this species could inhabit both fresh and brackish water environments. It is interesting to note that only one tooth has been recovered from the highest conglomerate (VL-492), despite the very large sample of rocks collected from this horizon, further indicating a weak marine influence higher in the section. Order LAMNIFORMES Family MITSUKURINIDAE SCAPANORHYNCHUS TEXANUS

(Fig. 1.19 C) Referred specim ens—LSUMG 488: 5517; 489:5626,5666. Description—V-5517, 5626, and V-5666 are large broken teeth. Only the median cusps are present, but are missing their apical ends. The cusps are straight and slightly convex. V-5626 is 8 mm long and 6.5 mm wide at the

base, distally-medially; V-5666,15 mm long and 8 mm wide; and V-5517 is 5 mm long and 3 mm wide. Many strong longitudinal ridges extend the length of the crowns and on both sides, but are more prominent on the lingual

surfaces. Comparisons and Discussion—The characteristics of the teeth described above match the descriptions and illustrations in Welton and Farish (1993:95). Rowe et al. (1992:477) report that teeth of Scapanorhvnchus sp. are

present, but rare in the Terlingua local fauna. Two teeth of Scapanorhvnchus texanus from the lower Aguja Formation are mentioned

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. in Standhardt (1986:80) and Lehman (1985:255) reported that S. texanus is the most common shark taxon in the lower Aguja. According to Case and Cappetta (1975:142), it is the most common mitsukurinid species in Late

Cretaceous deposits in the U.S. Modem mitsukurinid sharks, such as Mitsukurina owstoni. are bottom-dwellers in deep waters (200-700 m), but can enter shallow waters at

night (Cappetta, 1987:91). The paleoecology of Scapanorhynchus is not well known, but based on its anatomical similarity to M. owstoni (Cappetta, 1987:93), it is possible that Scapanorhynchus occupied similar habitats. It has only been recovered from the lowest conglomerates (VL-488 and 489). BATOMORPHII

Order RAJIFORMES Family RHINOBATOIDEI incertae sedis

SOUATIRHINA AMERICANA (Fig. 1.19 F) Referred specim ens—LSUMG 140:6122; 489:5689; 491:5947; 490:5911;

492:5558. Description—Teeth are very small (1.2 mm in greatest width and 0.7 in

greatest height); have a tall, sharply pointed cusp; and some have cuspelets

adjacent to this cusp. The labial flange is short and squared off in outline, two characteristics which help distinguish it from the similar Onchopristis d u n k lei. Comparisons and Discussion—Teeth closely match the descriptions and illustrations of S. americana in Estes (1964:12) and are very similar to those illustrated from the Terlingua local fauna (Rowe et al., 1992:477). Although Cappetta (1987:142) questioned Estes' (1964) assignment to Squatirhina. he did

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. agree they are orectolobids. Welton and Farish (1993:135) place possible Squatirhina teeth in the Rhinobatoidei incertae sedis. Until further taxonomic work has been done on this taxon, I am following Estes (1964) and

Rowe et al.'s (1992) assignment to £. americana. Rhinobatoidei family uncertain. S. americana is known from the Late Cretaceous to the early Eocene.

Modern rhinobatoids (guitarfishes) live in tropical and subtropical oceans, and some live in freshwater. They are bottom dwellers and feed on crustaceans and molluscs (Welton and Farish, 1993:130). £. americana have been recovered from four of the five conglomeratic horizons in the Talley Mt. local fauna, but is absent from the lowest (VL-488) conglomerate. Although their paleoecology is not well known, it is probable that this taxon lived in brackish to fresh water. Its absence from the lowest

conglomerate is difficult to explain, but the presence of only a single tooth

from the highest conglomerate is probably due to a decrease in marine influence higher in the section. Family SCLERORHYNCHIDAE

ISCHYRHIZA AVONICOLA

(Fig. 1.19 E) Referred specim ens—LSUMG 140:5628; 489:5629; 491:5977. Description—All specimens are very small rostral teeth. Crowns are

convex and are 0.7 to 0.8 mm long and 0.6 to 0.7 mm wide at their base. Crown surfaces have longitudinal ridges at their base. The roots form most of the tooth and are very wide (up to 1.5 mm, mesially-distally).

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Comparisons and Discussion—The rostral teeth compare well to those

described and illustrated in Estes (1964:13) and in Welton and Farish (1993:140) and to those illustrated in Rowe et al. (1992:477). Modem sawfishes (Pristidae) live in warm to tropical seas and inhabit nearshore areas, in or around the mouths of rivers; they prefer brackish and estuarine conditions. Sawfishes are bottom dwellers and feed on fish and shellfish (Welton and Farish, 1993). Cretaceous sawfishes (Sderorhynchidae), which closely resemble modem sawfishes anatomically, probably occurred in similar environments (Estes, 1964). However, one Central American species lives completely in fresh w ater (Bryant, 1989:12). Only three teeth of I. avonicola have been recovered from the Talley Mt. fauna, making this one of the rarest chondrichthyans in the fauna. These teeth were recovered from the lowest three conglomerates, further indicating a stronger marine influence occurred lower part of the section. I. avonicola was also recovered from the Terlingua local fauna (Rowe et al., 1992). ONCHOPRISTTS DUNKLEI

(Fig. 1.19 D) Referred specim ens—LSUMG 140:6111; 489:5667; 491:5951; 490:5908. Description—Oral teeth are small (1.7 mm in total length, including root, and 1.7 mm wide at base of the root), with a very tall and narrow cusp and two cuspelets. The labial protuberance is long and narrow. Comparisons and Discussion—These teeth are very distinctive and match those described and illustrated in Welton and Farish (1993:143) and those illustrated in Rowe et al. (1992:477). O. dunklei was a Cretaceous sawfish; although little is known about its paleoecology, it may have lived in similar environments as the modem

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. spedes (discussed above). Teeth of O. dunklei have been recovered from three of the five conglomeratic horizons of the Talley Mt. local fauna. Their absence from the highest horizon may be due to decrease in marine influence

higher in the section. O. dunklei was recovered from the Terlingua local fauna (Rowe et al., 1992), a record which extended the range for this spedes up from the Cenomanian Woodbine Formation (McNulty and Slaughter, 1962; Slaughter and Steiner, 1968). Its presence in the Talley Mt. local fauna, further extends its range, higher into the upper Aguja Formation. PTYCHOTRYGON sp.

(Fig. 1.19 G) Referred specimens—LSUMG 140:6123; 489:5670; 491:5631; 492:6261. Description—Teeth are very small (1.2 mm in greatest width and 0.8 mm in greatest height) and extremely short and compact. The crown is high

and triangular and has no cusplets. Crown surfaces are fairly smooth (without ornamentation), with usually only one transverse ridge on each side of the crown. Labial and lingual flanges are broad, round, and equal in

size. Roots are large, well separated into two lobes, and have a large notch between the lobes.

Comparisons and Discussion—Teeth compare very well to illustrations

of Ptychotrvgon sp. from the Terlingua local fauna which Rowe et al. (1992:477) considered to be a possible new spedes. The teeth described here may belong to this new spedes, as they do not resemble any other described species of Ptychotrvgon. They are dearly not P. agujaensis. which was described from the Aguja Formation (McNulty and Slaughter, 1972), because

they do not have flat crown surfaces. They are also not easily referred to P.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. hooveri. P. slaughteri, or P. triangularis, because of their lack of ornamentation and the low number of transverse ridges. However, they could be P. texana (a common Maastrichtian taxon; McNulty and Slaughter,

1972), which also lacks crown ornamentation and has conical cusps. Ptychotrvgon was another group of Cretaceous sawfish, and although little is known about their paleoecology, they may have lived in similar

environments as the modern species (discussed above). Ptychotrvgon has been recovered from three of the five conglomerates, but only one has been found from the highest conglomerate (VL-492),

possibly a sign of less marine influence higher in the section. Order MYLIOB ATIFORMES Family MYLIOBATIDAE DASYATIDAE

(Fig. 1.191) Referred specimens-LSUM G 488:5505; 140:6126; 489:5648; 490:5910; 491:5946,5956,5969; 490:5904. Description—Teeth are very small (0.7 to 1.2 mm high and 1.2 to 2.2

mm wide, longest width of occlusal surface). Occlusal surfaces vary from smooth to pitted and grooved. Top of crowns are flat, with transverse ridges.

Roots are bilobed. Comparisons and Discussion—Teeth closely resemble illustrations and

descriptions of ?Dasyatidae, genus and species undetermined, in Welton and

Farish (1993:157), but could also be included in Dasvatis as described and illustrated in Cappetta (1987:163). However, D asvatis is not well defined, and

probably includes many, unrelated taxa, so this designation has been avoided.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Modem dasyatid stingrays are bottom dwellers and feed on crustaceans, molluscs, and small fish. They live in warm, shallow, coastal waters, especially in the subtropics and tropics (Welton and Farish, 1993). They can enter estuaries and rivers, and some modem species are completely

freshw ater (Budker, 1971). Only 24 dasyatid teeth have been recovered from the Talley Mt. local fauna. Most of the teeth are from VL-491, the third highest conglomeratic

bed. None have been found from VL-492, the highest conglomeratic bed, further supporting the interpretation of a weaker marine influence higher in

the section.

Rowe et al. (1992:476) recovered one large, square tooth of an indeterminate dasyatid and several fragmentary teeth of other batoid taxa from the Terlingua local fauna. Class ACTINOPTERYGII

Family LEPISOSTEIDAE LEPISOSTEUS OCCIDENTALIS (Fig. 1.20 A-C)

Referred specimens—LSUMG 488:5494,5516,5518, 5521; 140:6116, 6127, 6128,6129,6135; 489: 5650,5651,5653,5732; 491:5949,5967,5982,5983; 490:5907,

5912; 492:6243,6244. Description—Specimens referred are teeth, teeth caps, and scales. Complete teeth are rare. Teeth are straight, small, slender (0.7 mm wide), and with many, deep, longitudinal ridges. Tooth crowns on these teeth are either arrow-shaped and strongly keeled or conical and very weakly keeled to unkeeled. Tooth caps are much more common than complete teeth. They

vary in size and shape, but are usually straight, conical, smooth surfaced, and

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. strongly keeled. Greatest lengths vary from less than 1 mm to over 4 mm; greatest widths, from less than 1 mm to over 4 mm. Smaller teeth tend to be more triangular-shaped with very sharply pointed ends, and larger teeth are more conical, with blunter, rounder ends. Scales vary in size; the largest

recovered is over 15 mm in greatest length. Most scales are broken, but complete ones are rhomboid in shape. They have smooth surfaces. Comparisons and Discussion—The identification of L. occidentalis

from the Talley Mt. local fauna is based only on isolated teeth and tooth crowns. They match the descriptions of L. occidentalis in Estes (1964) and Bryant (1989), but because of the variation in tooth cap sizes and shapes, more than one taxon may be represented in this collection. There are also many isolated fish post-cranial bones in the collection, but no identifications were

attempted. Although Wiley (1976) split fossil and modem gars into two groups, Lepisosteus occidentalis and Atractosteus spatula. I am following Bryant (1989), who considered that the inter- and intra-specific differences among gars are not well enough understood to make this distinction. Modem gar species range in size from the small gar pike (L. osseus) to

the very large alligator gar (L. spatula) and live in brackish to freshwaters from southeastern Canada to Mexico. L. occidentalis was most similar to L. spatula, which lives today in large streams along the Gulf coast and feeds

mainly on fish (Bryant, 1989; Wiley, 1976). Lepisosteids (especially their tooth caps and scales) are the most common fossil from the Talley Mt. local fauna, and have been found from all five of the conglomeratic horizons. However, there are fewer of them from the highest conglom erate (VL-492) com pared to the lowest ones (VL-488, 489/140). Although little is known about the paleoecology of L. occidentalis.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. its similarity to L. spatula suggests that it also lived in large streams near the ocean. Its presence in the conglomeratic horizons supports the interpretation that the conglomerates formed in large stream channels or in flood-related channels within a lowland coastal environment. Lepisosteids are the most common fish reported from the Aguja Formation (Lehman, 1985; Rowe et al., 1992; Standhardt, 1986). In addition, these authors have reported on the less common amiids from the Aguja, but none have been recognized from the fragmentary material from the Talley Mt. fauna. Class TELEOSTEI Family PHYLLODONITDAE

(Fig. 1.20 E) Referred specim ens—LSUMG 488:5492; 489:5577. Description—Fragments of bone (2 nun long) with small (less than 1 mm), spheroidal, flat teeth embedded in the bone. Comparisons and Discussion—Tooth plates are too small and fragmentary for identification below the family level. Rowe et al. (1992:477) also recovered many small, spheroidal teeth from a phyllodontid fish from the Terlingua local fauna. The paleoecology of this group of fish is not well known. They have

been reported from other Late Cretaceous deposits (Hell Creek Formation, MT, Bryant, 1989; Judithian of Alberta and Maastrichtian of New Jersey, Estes,

1969). The only specimens which have been recovered from the Talley Mt.

local fauna are from the lowest two conglomeratic horizons (VL-488 and 489), possibly reflecting the more marine influence lower in the section.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. DISCUSSION Eight chondrichthyan taxa have been recovered from the

conglomerates. The taxonomic composition of this assemblage is very

similar to that of the Terlingua local fauna (Rowe et al., 1992), a similar aged microvertebrate fauna also from the upper shale member of the Aguja. None of the taxa provide detailed biostratigraphic information, but they do provide important paleoecological information of the deposits in this

area. Although little is known about the paleoecologies of these sharks,

several observations can be made. Modern hybodontid sharks live in marine or brackish water environments, but little is known about the paleoecologies of Hybodus sp. or Lissodus selachos. Only two Hybodus sp. teeth have been recovered from the conglomerates, and both are from the stratigraphically lowest horizons (VL- 488 and 489). Their rarity in the fauna and their presence only in the lowermost conglomerates suggests that the deposits were not closely tied to marine waters, but that the lower portion of the section was under more of a marine influence than the higher portions. Additionally, because Hybodus

sp. was more common in the Terlingua local fauna, deposits sampled in the

Talley Mt. area were clearly under a weaker marine influence than those at

Terlingua. The hybodontid shark, L. selachos. thought to have inhabited brackish to fresh waters (Estes, 1964:159 and Capetta, 1987:24 and 36), is the most common shark recovered from the Talley Mt. local fauna. Although it has been recovered from all five conglomerates, only one tooth has been recovered from the highest conglomerate (VL-492), despite the very large sample of rocks collected from this horizon. Its extreme rarity higher in the

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. section indicates that the marine influence had significantly decreased at this time. L. selachos is the most common shark recovered from the Terlingua local fauna (Rowe et al., 1992), which further supports the idea that the Terlingua was an estuarine deposit, more closely tied to marine water. Only three teeth from the mitsukurinid shark, Scapanorhynchus texanus have been recovered from the Talley Mt. local fauna. The paleoecology of this shark is also not well known, but if it was similar to living species in this group, then it inhabited deep marine waters. Again, it is interesting that this taxon is only known from the lowest conglomerates (VL- 488 and 489), indicating more marine influence lower in the section. The distribution patterns of the three sharks and the other four chondrichthyan taxa support the interpretation that the lower portion of the section (especially, VL-488 and 489/140) in the Talley Mt. field area had more connection with marine waters than the higher portions (especially, VL-492). It must be emphasized that until the paleoecologies of these Cretaceous chondrichthyan taxa are better understood, the above paleoenvironmental

interpretations are tentative. For example, some tropical chondrichthyan taxa enter estuaries and freshwater rivers, and some can live exclusively in

freshwater lakes (Budker, 1971:141). Although the freshwater tolerances of these Cretaceous taxa are not known, it is probable that they could also live in

brackish to fresh waters. The actinopterygians present are also similar to those reported from

the Terlingua (Rowe et al., 1992), and provide useful paleoecological information. The gar, L. occidentalis is commonly found in fluvial channel fills and is considered to be a brackish to freshwater taxon. Gars are common in Late Cretaceous deposits. They probably lived in shallow, weedy waters

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (their modern habitat) within major drainages of the Western Interior Seaway, although they were probably not restricted to fresh water (Bryant, 1989). Gars are much less abundant in the highest conglomerates. CONCLUSIONS The chondrichthyan and actinopterygian assemblage from the Talley Mt. local fauna is very similar to that of the Terlingua local fauna. However, the total number of fossils and the diversity is lower in the Talley Mt. fauna. This is due partly to taphonomic and sampling biases, but is also due to the more terrestrial deposits in the Talley Mt. area. The Terlingua local fauna was collected from an estuarine deposit. The Talley Mt. local fauna was collected from fluvial channels within marshes that were further inland.

The decrease in the number (and diversity) of taxa upsection in the Talley Mt. area documents an environmental change during the 0.7 My sampled to a less aquatic setting with a decrease in marine influence and possibly conditions with seasonal aridity.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. HERPETOFAUNA OF THE TALLEY MT. LOCAL FAUNA, UPPER AGUJA FORMATION (LATE CAMPANIAN), BIG BEND NATIONAL PARK, TEXAS INTRODUCTION The herpetofauna is described from the late Campanian Talley Mt. local fauna of Big Bend National Park, Texas. The fauna was collected from the lower portion of the upper shale member of the Aguja Formation. The fossils were collected by bulk sampling five horizons of carbonate-cemented, pedogenic-nodule conglomerates. Associated magnetostratigraphic correlations constrain the fauna to the base of Chronozone 32. Approximately ~0.7 My occurred (~73.6 to 74.3 Ma) between the lowest and highest conglomerate. Previous environmental interpretations for the Aguja deposits in the area had suggested that they had formed in a coastal setting, ranging from interdistributary marsh-bay facies at the base of the exposed section to inland floodplain facies at the top (Lehman, 1982,1985). The five horizons sampled are from within the lower portion of the section. The herpetofauna assemblage are used to provide more detailed paleoecological information for

these deposits than was previously available.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SYSTEMATIC PALEONTOLOGY Class AMPHIBIA Order CAUDATA Family PROSIRENIDAE

ALBANERPETON sp. (Fig. 1.21 A) Referred specimen—LSUMG 140:5606; 491:5958. Description—Both specimens are very small maxillary fragments (0.7 mm and 1.0 mm long). Teeth are closely spaced, minute (0.1 mm wide and 0.5 mm long), straight, and with flat to slightly rounded crowns. Comparisons and Discussion—The specimens compare well to illustrations and descriptions of Albanerpeton (= Prodesmodon copei in

Estes, 1964:90), Estes (1981), and Standhardt (1986). Albanerpeton was probably an aquatic salamander (Estes, 1964). Many specimens have been recovered from the Terlingua local fauna (Rowe et al., 1992), but only 1 (referred to A. nexuosus) has been recovered from the uppermost Aguja Formation (Standhardt, 1986). Few specimens have been recovered from the conglomerates, possibly because of the very fragile nature of these fossils.

Family SCAPHERPETONTIDAE SCAPHERPETQNsp. (Fig. 1.21 B) Referred specimen—LSUMG 489:5694. Description—This specimen is a 4 mm long fragment of a left dentary. Twenty teeth (or teeth spaces) are present on this fragment and they are

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. tightly spaced. Teeth are small (0.1 mm wide; 0.3 mm long) and short with

fairly straight crowns. Comparisons and Discussion—The specimen compares very well to descriptions and illustrations of Scapherpeton; dentaries would have contained 60-75 teeth (Estes, 1964). Scapherpetontids were recovered from the Terlingua local fauna, but less comm only than A lbanerpeton sp. (Rowe et al., 1992). Standhardt (1986)

recovered one specimen of Scapherpeton tectum from the uppermost Aguja. So few Scapherpeton specimens were recovered from the Talley Mt. local fauna probably due to their fragile nature; they would have been destroyed during transport and deposition in the conglomerates. AMPHIBI A-indet

Referred specim en-LSU M G 140:6182; 489:5682; 491:5979; 492:6266. Description—Fragmentary and very small posteranial bones.

Comparisons and Discussion—These specimens are too fragmentary to be identified beyond amphibian. There are several possible frog postcranial bones in this collection, but further identification is not possible with this

fragmentary material. Class REPTILIA

Order TESTUDINES Family TRIONYCHIDAE-indet (Fig. 1.22)

Referred specim en-LSUM G 489:5535,5677,5686; 491:5537; 490:5531; 492;5533,5534.

1 1 1

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Description—All specimens are carapace or plastron fragments. Pits vary from round to oval in shape and from large (30 mm in diameter) to

small (1 mm in diameter) in size. Comparisons and Discussion—Referral to trionychid is based on the ornamentation of the fragments. Because identifications based only on carapace ornamentation is discouraged, further identification is not possible with the fragmentary material in this collection. However, the ornamentation patterns (for example, LSUMG 492:5533, Fig. 1.22) are most similar to those of the trionchyid, ?"Aspideretes". illustrated in Tomlinson (1997:103). "Aspideretes" is the most common turtle from the upper shale member of the Aguja Formation (Tomlinson, 1997:120; Lehman, 1985), and has also been recovered from the Terlingua local fauna (Rowe et al., 1992). The scarcity of turtle fossils in this collection can be explained by the fact that few large bones of any vertebrate have been recovered from the conglomerates. Usually large bones have been broken into the small, unidentifiable fragments during transport and deposition in the conglomerates. The carapace fragments described here are exceptions to this

observation. Fig. 1.17 (bottom left) shows one of these fragments (LSUMG

490:5531) still attached to the conglomeratic rock.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Order SAURIA ANGUIMORPHA

Family ANGUIDAE

Subfamily GLYPTOSAURINAE-indet (Fig. 1.21 C) Referred specimens—LSUMG 140:6106. Description—Specimen is a 3 nun long maxilla fragment with five teeth. Teeth are 0.4 mm wide and 1.0 mm long. Crowns are pointed with slightly rounded tips. Comparisons and Discussion—Specimen is too worn and fragmentary

to identify beyond the subfamily level. However, it compares well to Odaxosaurus piger from the Terlingua local fauna (Miller, 1997) and to Late

Cretaceous O. piger specimens at UCMP (V-5711; Lance Formation, Niobrara

Co., WY). A second glyptosaurine from the Terlingua local fauna was originally reported as Proxestops sp. (Rowe et al., 1992), but is no longer considered to be from this taxon (M.S. Miller oral comm., 1996 and Miller, 1997). SaNCOMORPHA FamilyTEIIDAE CHAMOPS (Fig. 1.21 E)

Referred specimens—LSUMG 140:6104. Description—Specimen is a 3 mm long mandible fragment with five teeth. The teeth are short (0.5 mm wide; 1.1 mm long), stout, and slightly

tricusped. From the lateral view, the tooth bases expand out slightly in the anterior-posterior direction.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Comparison and Discussion—This specimen closely resembles Chamops sp. specimens described and illustrated in Gao and Fox (1996:25; Fig. 7F-P and to Chamops specimens at UCMP (49809; Lance Fmtn; WY),

especially its teeth, which are robust and barrel-shaped. It is also similar to Meniscognathus (UCMP 49838; Lance Fmtn; WY), especially in its crown height. It is least similar to Leptochamops (UCMP 49826), which have more

slender (not barrel-shaped) and straight teeth. Although many teiids was recovered from the Terlingua local fauna, no Chamops have been identified (Miller, 1997; Rowe et al., 1992). PENETEIUS sp. nov. (Fig. 1.21 F)

Referred Specim ens—LSUMG 492:6253. Description—Specimen is an isolated maxillary tooth, still attached to a

fragment of maxillary bone. It is subpleurodont, bi-cusped, and has heavy cementum at the base. Comparisons and Discussion—This specimen represents a new species of Peneteius and will be included in the species description by Randall

Nydam (in preparation, 1998) who identified it (R. Nydam, written comm.,

1998). It is the seventh and southernmost record of this species in North A m erica.

TEIIDAE-indet cf. "Species B" Miller, 1997 (Fig. 1.21 D) R eferred Specim ens—LSUMG 489:5656.

Description—V-5656 are two isolated teeth; one is still attached to bone. They are large (2 mm long and 1.2 mm wide) and robust teeth. Crowns are

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. round and have strong longitudinal striations on all sides which join at the

apex to form a small point. Comparisons and Discussion—Further identification with this material is not possible. However, these teeth most closely resemble the teiid, "Species B" of Miller (1997:45) from the Terlingua local fauna. SQUAMATA-indet Referred Specimens-LSUM G 488:5780; 140:6107,6110; 489:5601.

Description—These specimens are tiny fragments of squamate jaws. Comparisons and Discussion—Specimens are too fragmentary for further identification. ARCHOSAURIA

Order CROCODYLIA Suborder MESOSUCHIA

Family GONIOPHOLIDAE-indet

(Fig. 1.23 B) Referred specimens-LSUMG 488:5485; 489:5608,5673, 5707,5786. Description—Teeth are tall, straight to slightly recurved, and have two 'keels' on the anterior surfaces. Crown surfaces vary; some crowns are smooth and others have prominent longitudinal ridges. Teeth are all broken, but the m ost complete (V-5673) is 2 cm in greatest length and 1 cm in greatest width.

Comparisons and Discussion—Teeth are referred to a goniopholid based on the presence of the keels on all teeth and on the presence of strong longitudinal striations on most of the teeth; characters used by Lehman (1985:259).

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Goniopholid teeth have only been recovered from the lowest two conglomeratic horizons (VL-488 and 489). Two of these teeth (V-5608 and 5673) were recovered by surface collecting at the level of the conglomerate (VL-489), and although they may be originally from the silt-fine sandstones within centimeters below this conglomerate, such a minute stratigraphic distinction is irrelevant to this work (see a similar discussion under Deinosuchus riograndensis. below).

The goniopholid in the Aguja Formation is probably Goniopholis cf. G. kirtlandicus (Rowe et al., 1992). A partial skeleton has been found from both the lower and upper shale members and isolated teeth have been found

from the upper shale member of the Aguja (Lehman, 1985:259). Suborder EUSUCHIA Family CROCODYUDAE DEINOSUCHUS (=PHOBOSUCHUS) RIOGRANDENSIS

(Fig. 1.23 A) Referred Specim ens-LSUM G 488:5484; 489:5644,5672,5674,5675. Description—Specimens are large, robust teeth (or fragments of teeth).

Teeth vary from short, straight, blunt-tipped, with anastomizing striations (as in V-5484) to long, slightly recurved teeth with longitudinal striations. None of the teeth have keels. Teeth vary in size from 3.0 to 6.5 cm in greatest length and 1.5 to 2.5 cm in greatest width.

Comparisons and Discussion—Teeth are referred to D. riograndensis based on their very large size. Variations in tooth size and shape are probably due to different tooth position in the jaw and to size of the individual. Tooth size varied considerably within the skull of D. riograndensis. and some teeth

were as large as 10 cm in diameter in the specimens in the TMM collection.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. All of these teeth were found from the lowest two conglomerates (VL- 488 and 489). All were found by surface collection from the same area that the conglomerates were found, except for V-5644, which was recovered during screen washing. It is uncertain whether these teeth eroded out from

the conglomerates or from the fine sands and silts just centimeters below the conglomeratic horizons. This observation is important, however, in recognizing that recovery of such large teeth is rare from the conglomerates.

Usually teeth of this size were destroyed during transport and only unidentifiable fragments of large teeth remain. V-5644, the largest vertebrate tooth recovered during screen washing the conglomerates, is an exception to this observation. D. riograndensis. the largest crocodile from the Aguja Formation (Lehman, 1982, 1985), is fairly common in the middle shale and the base of

the upper shale members (Lehman, 1985:259). It has also been recovered from the Terlingua local fauna (Rowe et al., 1992). The type specimen of D. riograndensis was described from a very fragmentary and incomplete skull and partial posteranial skeleton (Colbert

and Bird, 1954) collected in the Talley Mt. field area (Figs. 1.9 and 1.10). A more complete (and larger) skull has recently been collected from the upper Aguja Formation by TMM personnel and is under preparation there. cf. BRACHYCHAMPSA (Fig. 1.23 C) Referred specim ens-LSUM G 488:5503; 140:6125; 489:5658; 491:5621; 492:5557.

Description—Teeth are small, short, and bulbous. Their sizes range from 1 to 4 mm in greatest anterior-posterior length; 1 to 2 mm in greatest

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. crown height; and 1 to 3 mm in greatest mesial-lateral width. Very heavy longitudinally wrinkled enamel occurs on all crown sides. Tops of crowns are fairly flat to pointed, with a prominent anterior-posterior oriented ridge. In some specimens this ridge is worn down to a depression. Comparisons and Discussion—Teeth match the descriptions and illustrations of Brachycham psa in Bryant (1989:55) and Standhardt (1986:133). Both Langston (pers. comm, in Rowe et al., 1992) and Brochu (oral comm., 1998) doubt that identifications of either Brachychampsa or Leidvosuchus can be done on isolated teeth. However, because the teeth described here are so distinctive and match those identified by Bryant (1989) and Standhardt (1986), I have assigned them to Brachychampsa. CROCODYLIA-indet

(Fig. 1.23 D-F) Referred specim ens—Scutes: LSUMG 140:6133,6136,6179;489:5607,

5582,5668,5573; 491:5549; 490:5611. Teeth (A): LSUMG 488:5496; 140:6114; 489:5663; 491:5970; 492:6176. Teeth (B): LSUMG 488:5519; 140:5564; 489:5697; 491:6022; 490:5571; 492:6249.

Description—There are two types of small (less than 1 cm long) fragments of crocodylian scutes present. In the first type, the bone is very thin (0.2 mm thick) and the numerous pits present are round to oval in shape (Fig. 1.22 F, right). In the second type of scute, the bone is much thicker (1 mm thick) and the pits are round and considerably deeper (Fig. 122 F, left). There are two types of very small crocodylian teeth. The first type (A) are short, conical, with two bilateral keels, and very smooth crown surfaces (Fig. 1.23 E). These teeth are usually less than 2 mm wide and 1.5 mm long. The second type (B) are short, robust, slightly recurved to straight, very

118

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. strongly striated teeth, and most have bilateral keels (Fig. 1.23 D). They are usually less than 4 mm long and less than 2 mm wide. Comparisons and Discussion—All scutes tire referred to crocodylian- indet.; further identification is not possible with the material recovered.

Whether more than one taxon is represented by these 2 types of scutes is not know n. Several taxa may be represented by the small teeth described above (especially within type B), but further identification is not possible based on these isolated teeth for several reasons. First, teeth vary greatly not only within the jaw of one individual, but within its lifetime, and among taxa.

Second, a thorough taxonomic study of crocodylians based on teeth has not

been done, so identification of these teeth beyond this level would be m eaningless (Brochu, oral comm., 1998). Lehm an (1985:260) reports that there are tw o indeterm inate crocodilian taxa in the Aguja. These taxa are based on small, slender teeth, with no keels or costae, and with fine longitudinal striations on all crown surfaces.

Class DINOSAURIA Subclass ORNITHISCHIA

Order ORNITHOPODA Family HADROSAURIDAE-indet (Fig. 1.24 A) Referred Specimens-LSUMG 140:5562,5578; 489:5538,5700; 491:5544; 490:5570.

Description—The tooth crowns and tooth crown fragments are very small. Two complete tooth crowns, without the roots (V-5700 and V-5538)

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. are 2 and 4 mm in diameter, respectively and have a star-shaped occlusal

outline. Comparisons and Discussion—Hadrosaur skulls and mandibles contained rows of many, densely packed, interlocking teeth which formed tooth batteries (Weishampel, 1984; Homer, 1990:179; Weishampel and Homer, 1990:535 and 547). Although hadrosaur identifications are mainly based on skull characteristics (Weishampel and Homer, 1990:535), Homer (1990) did include dental characteristics to differentiate the two hadrosaur groups, the hadrosaurinae and the lambeosaurinae. In the former's dentary teeth, the angle between the crown and root is less than 130 degrees and the

teeth are diamond shaped (Meszoely, 1970:180-2). Because no teeth with roots were recovered, an identification to the subfamily level is not possible.

However, the most common hadrosaur found in the Aguja is Kritosaurus cf. navajovius (= ?G rvposaurus in H om er and W eisham pel, 1990:122) and it is likely that these teeth are from the same taxon. The two complete tooth crowns (V-5700 and V-5538), although considerably smaller, have the same occlusal outline as the hadrosaur, Hadrosaurus sp. (TMM 42315-1) from the Judith River Formation, Dinosaur Provincial Park, Alberta and as the Prosaurolophus sp. figured in Homer

(1990; fig. 13.3 A). Although the other specimens are fragments, they are referred to hadrosauridae based on their shape and on the absence of the rugose external surface present in ceratopsids. Based on their very small sizes, all of these teeth and fragments are probably from juveniles or possibly even from hatchlings. Many unidentified hadrosaurid teeth and teeth fragments were found from the Terlingua local fauna, including some from very young individuals

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (Rowe et al., 1992), and are probably the most common dinosaur fossil in this fauna (personal observation, 1998). Hadrosaur teeth and teeth fragments were also recovered from the uppermost Aguja in the Dawson Creek area

(VL-113), and the small teeth (probably from juveniles) are the most

common dinosaur fossil from this locality (Standhardt, 1986:149). Kritosaurus sp., K. cf. navajovius. and an unidentified lambeosaurine have been found elsewhere in the Aguja (Lawson, 1972; Davies, 1983; Davies

and Lehm an, 1989). K ritosaurus sp. bones were found in the W PA 1-3 quarries and in other localities in the Talley Mt. field area (Lehman, 1982; Davies, 1983; Davies and Lehman, 1989). Within the WPA quarries, the hadrosaur bones were associated with ceratopsian, crocodylian, ankylosaur, and a small number of camosaur, small theropod, fish, and turtle fossils. WPA #3 had the largest percentage of hadrosaur bones (66%; Davies and Lehman, 1989). The Kritosaurus faunal assemblage, dominated by bones of this dinosaur, accumulated in coastal marshes and swamps and is found in carbonaceous daystones assodated with crevasse sand sheets of the Aguja (Lehman, 1985:157). Because hadrosaurs are the most common dinosaur fossils in the Aguja (Lehman, 1985:262), it is surprising that so few hadrosaur fossils were

found from the conglomerates; the only ones found were juvenile teeth.

These very small teeth are approximately the same size as the other dinosaur teeth from the conglomerates. Obviously this is a taphonomic bias toward fossils of a particular size. Most hadrosaur teeth would have been a larger- sized dast than is typically found in the conglomerates. There are many

unidentifiable bone and tooth fragments in the conglomerates; some of these

may be from hadrosaurs.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Order CERATOPSIA Family CERATOPSID AE-indeL (Fig. 1.24 B) Referred Specim ens-LSUM G 488:6230; 492:5581. Descrip tion—Specimens are tooth crown fragments of large teeth, probably from adults. The external surface of one ridge has many small and round denticles.

Comparisons and Description—The shape of the tooth fragments and the presence of the denticulate ridge closely resemble ceratopsian teeth. They compare well to a ceratopsid tooth fragment from the uppermost Aguja (113:1373; Standhardt, 1986:156). Ceratopsian bones and teeth were also found from the Terlingua local fauna, but in lesser abundance than the hadrosaur m aterial (Rowe et al., 1992:482). Ceratopsians also had dental batteries, or densely packed interlocking

teeth, but their teeth had two roots (Dodson, 1997:473). Ceratopsian (Chasmosaurus mariscalensis: Lehman, 1989) bones are rare in the upper shale member of the Aguja, but bone beds do occur, for example WPA-1 in

the Talley Mt. field area (Lehman, 1982,1985; Davies and Lehman, 1985; Lehman, 1989) and a nearly complete skull from Rattlesnake Mountain (Forster et al., 1993). Although the specimens recovered from the

conglomerates are only small tooth fragments, they were recovered near

WPA-1 (V-6230 from 4.5 m above the level of the quarry) and probably represent this taxon. The WPA-1 quarry produced the largest number of ceratopsian bones of any of the WPA quarries (representing a minimum of ten individuals and 72% of the bones; Lehman, 1982; Davies and Lehman, 1989:36-37). This

122

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. particular accumulation of ceratopsian and hadrosaurian bones is thought to represent a mass mortality event: possibly a herd was concentrated around a drying watering hole during a severe drought in the area (Davies and Lehm an, 1989:37 and 42). Except for unusual bonebeds like WPA-1, the general scarcity of ceratopsians in the Aguja may explain why only one partial tooth has been recovered from the conglomerates. In addition, there is a taphonomic bias against recovering larger teeth from the conglomerates. ORNITHISCHIA-indet.

Referred Specimens-LSUMG 489:5572,5536,6231; 492:5556.

Description—The specimens are fragments of non-camivorous dinosaur teeth, but are too broken or worn to be identified further. They are large tooth fragments with smooth external surfaces from small, possibly juvenile teeth. Comparisons and Discussion—These teeth are most likely from

hadrosaurids, which are discussed above. Order SAURISCHIA

Suborder THEROPODA

C ARNOS AURIA

Family TYRANNOSAURIDAE-indeL (Fig. 1.24 C) Referred Specimens-LSUMG 489:5580. Description—V-5580 is a small (2 mm long) carinae fragment. Denticles are short (0.5 mm proximally-distally) and wide (0.3 m m at base, anteriorally-posteriorally). Their tops are round in outline; not pointed.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. There are spaces (0.1 mm wide) between denticles and very distinctive blood grooves. There are 2.5 denticles/mm. Comparison and Discussion—Juvenile tyrannosaurid teeth and fragments are often found along with small theropod teeth in Late Cretaceous microvertebrate sites (Abler, 1997). Tyrannosaurid teeth are more stout and robust than other theropod teeth, and although they are also laterally compressed, they are round in cross-sectional outline (Abler, 1997:741). Denticles occur on both the anterior and posterior carinae; they are large, chisel-shaped, wider (labially-lingually) than long (proximodistally),

and occur 3 /m m (Currie et al., 1990). V-5580 fits the above descriptions for tyrannosaurid teeth and compares well with illustrations in Currie (1990:121) and Abler (1997:742).

There are many other small carinae fragments in the collection, but all contain considerably smaller denticles and are probably from small

theropods. Based on this collection from the conglomerates, tyrannosaurids were a rare component of the fauna. Fewer tyrannosaurids than smaller theropods have been found in the

Aguja; most are isolated teeth from channel lags (Lehman, 1985:261). Although theropod teeth were recovered from the WPA quarries, they were not identified to genus (Lehman, 1982; Davies and Lehman, 1989). Rowe

(1992:482) reported that there was at least one large tyrannosaurid in the Terlingua local fauna and Standhardt (1986:144-147) reported three camosaurian morphotypes from the uppermost Aguja, one of which is possibly Albertosaurus. This scarcity in the Talley Mt. local fauna and in others from the Aguja supports the idea that tyrannosaurids were

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. uncommon in this area and that they possibly preferred drier, more upland

habitats. Suborder THEROPODA MANIRAPTORA

Family TROODONTIDAE Subfamily TROODONTINAE TRQQPQN-indet (Fig. 1.24 D) Referred Specimens-LSUMG 140:6117. Description—V-6117 is a compete crown of a tooth; the root is missing. It is 3.7 mm tall (proximal-distal), 2.9 mm wide (labial-lingual), with a fore-aft basal tooth length (FABL, fore-aft basal length; Currie et al., 1990) of 3.8 mm. The tooth is pyramidal and stout and is constricted at the base of the crown. The denticles are worn off from both carinae, but a hint of their large bases remain and indicate that there were denticles on both carinae. Comparisons and Discussion—V-6117 compares well to T. formosus teeth illustrated in Currie (1990:112), especially in its size and shape, constriction below the crown, and indication that there were few, but very large denticles present. However, the tooth may not be the same species of Troodon. Although Troodon teeth had considerable variation depending on their position in the jaw, two important characteristics, which this specimen

has, are the constriction below the crown and the very large denticles (Currie, 1987:80). There are several small (1-2 mm long) carinae fragments containing

large denticles in the collection that might also be from Troodon. However, because both troodontids and tyrannosaurids have similarly shaped and sized

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. denticles, it is difficult to distinguish between the two (Currie et al., 1990:113),

and they have been left unidentified. Troodon. represented by only one tooth (V-6117) is the rarest theropod from the Talley Mt. local fauna. Even if the several unidentified carinae fragments are also from Troodon. it would still be the least common theropod in the fauna. Troodon is also the rarest dinosaur from the entire

Aguja; V-6117 is only the third specimen reported to date. A possible Troodon tooth was reported from the Terlingua local fauna (Rowe et al., 1992:482-3) and Standhardt described a juvenile tooth referred to cf. Pectinodon (= Troodon) from the upperm ost Aguja (Standhardt, 1986:144).

Troodontids occurred in North America and Asia in the Cretaceous. They were small theropods with large brains, many teeth, long legs, and a retractable claw; they were presumably very fast moving predators. They lived in a variety of habitats, but may have preferred drier, cooler inland areas such as Alberta instead of wetter, coastal areas like Big Bend (Varricchio et al., 1997:749-753). This possible habitat preference may explain their rarity in the Aguja.

VELOCIRAPTORINAE

SAURORNITHOLESTES-m det (Fig. 1.24 E-G; App. HI) Referred Specimens-LSUM G 488:5483; 140:6139,6183,6184,6185,6186;

489:5659,6234; 491:5950; 492:5158. Description—All specimens are tooth crowns. They are small, flattened lingually, and are sharply recurved. FABLs vary from 2.6 to 9 mm. Denticles on the posterior carinae are considerably larger than those on the anterior carinae; although not all anterior carinae have denticles. Denticles are

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. rectangular-shaped (longer than wide), their edges are fairly straight, but are slightly pointed distally. Posterior denticle heights vary from 0.1 to 0.3 mm.

Posterior denticle counts vary from 4-7/mm (App. HI). Comparisons and Discussion— The small, flattened, recurved teeth compare well to other Sauromitholestes illustrated and described in the

literature (Fiorillo and Currie, 1994; Rowe et al., 1992). O ne tooth (V-5483;

Fig. 1.24 E) is especially large, but is referred to this taxon based on the other tooth and denticle characteristics outlined above. Numerous, very small carinae fragments with denticles that closely resemble those of Sauromitholestes are present in the collection, but are too fragmentary for

definite referral to this taxon. Other important characteristics of Saurorni tholes tes teeth are: recurved distally, sharply pointed, and laterally compressed. Denticles are straight and narrow (labially-lingually), hook distally near the tooth tip, and have deep interdenticle slits. Posterior carinae have approximately 5 denticles/mm and the anterior carinae have 7 denticles/mm, although many

teeth have none. Immature individuals have fewer and smellier denticles than more mature ones (Currie et al., 1990). Sauromitholestes has smaller

posterior denticles than Troodon and has more elongate and sharply pointed

denticles and more pronounced blood grooves than Dromaeosaurus. S. langstoni is the most common small theropod from the Judith River Formation. It had approximately 60 small teeth total, which occurred in sockets. Teeth from the type f>. langstoni (TMP 74.10.5) are 8.9 and 9.2 mm long and have FABLs of 3.9 and 4.5 mm, respectively (Currie et al., 1990). Saurorni tholestes is the most common dinosaur fossil recovered from the conglomerates. Although in other faunas hadrosaurs are the most

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. common, this is not the case here for taphonomic reasons explained in the hadrosaur section. Approximately 60 specimens were recovered from the Terlingua microsite (pers. observation, 1998). Several were also recovered

from the uppermost Aguja (LSUMG, VL-113), but were not referred to Saurom itholestes (Standhardt, 1986). MANIRAPTORA

FAMILY UNKNOWN RICHARDOESTESIA-indet

(Fig. 1.25 A-B; App. 4) Referred Specim ens-LSUM G 140:6140; 489:6233,6235,6236,6237, 6238,

6239; 492:6264. Description—The teeth are small (-3+ mm long), oval in basal cross- sectional view, very straight to slightly recurved, laterally flattened. Denticles are very small (0.1-0.2 mm long), closely packed, uniformly-sized, extend the length of the carinae, and occur on the anterior carinae in two of the teeth.

There are 4-11 denticles/mm. Comparisons and Discussion—Richardoestesia was a small carnivorous

dinosaur. Dentaries contained 18-19 teeth. Anterior mandibular teeth are relatively straight and slightly convex and posterior mandibular teeth are short and recurved. Most characteristic are the very short denticles (0.15 mm long), the shortest of any Judithian theropod. Denticles are usually only

present on the posterior carinae, and there are up to 5 denticles/mm (Currie

et al., 1990). The Talley Mt. specimens match the descriptions and illustrations of Richardoestesia (Currie et al., 1990; Rowe et al., 1992). However, one tooth

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. (V-6239), whose denticles are Richardoestesia-like, also has a twisted posterior

carinae, which is a Dromaeos a urns characteristic. Richardoestesia gilmorei (Currie et al., 1990) was described from the Judith River Formation, Alberta and, although isolated teeth are variable, they can be distinguished from Richardoestesia from the Maastrichtian by the presence of curvature in the proximal part of the tooth. Although several of the teeth described here are slightly recurved, a species designation cannot be

m ade. Only seven specimens are referred to Richardoestesia from the

Terlingua local fauna (pers. observation, 1998). One tooth from the uppermost Aguja (113:1375) may also be from this taxon (referred to as "carnosaur morphotype A"; Standhardt, 1986). Based on these records and on the 8 specimens from the Talley Mt. area, Richardoestesia was the second most common theropod in this area after Sauromitholestes. THEROPODA-indet Referred Specim ens-LSUM G 488:5488,5493,5499,5569,5783; 140:5784,

6108,6132; 489:5708,6232; 491:5545,5781,5785,5966,5980. Description—There are over 40 very small theropod tooth fragments in

the collection. These are often small pieces of carinae with denticles, but are

too fragmentary for further identification. Although Dromaeosaurus teeth were recovered from the Terlingua local fauna, none have been found from the Talley Mt. local fauna. However, they may be represented in some of

these unidentifiable tooth fragments. DISCUSSION Nineteen taxa have been recovered from the conglomerates, including lizards that are new records for the Aguja Formation. The taxonomic

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. composition is very similar to that of the Terlingua local fauna (Rowe et al., 1992), a similar aged microvertebrate fauna also from the upper shale member of the Aguja. The salamander taxa are considered to be primarily aquatic, and were recovered only from the lower conglomerates. Trionychid turtles (which live today in aquatic environments) were found from all of the conglomerates, but are rare. This rarity is probably due to the taphonomic bias against large sized vertebrate fossils in the conglomerates. Several lizard taxa were recovered from the conglomerates, including Chamops and Peneteius sp. nov., which are new records for the Aguja. Peneteius sp. nov is now known from seven specimens in North America, and the Talley Mt. specimen is the southernmost record for this species. Lizards are rare and were only recovered from the lowest two conglomerates (with the exception of Peneteius sp. nov. from the highest conglomerate). The absence of lizards from the higher conglomerates may be more due to sampling or taphonomic biases than to environmental preference. The considerable rarity of lizards in the Talley Mt. compared to the Terlingua is also probably due to their different taphonomic histories. Because lizard jaws and teeth are so fragile, most were probably destroyed before deposition

within the conglomerates. Their rarity is also due to size sorting. Glyptosaurine osteoderms are the most common lizard element from the Terlingua (Rowe et al., 1992), but none have been found from the conglomerates; these osteoderms are larger than most of the fossils (less than 4 mm long) recovered from the conglomerates. Several crocodylian taxa were recovered from the conglomerates: an

indeterminate goniopholidae, Deinosuchus riograndensis. cf.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Brachychampsa. and two indeterminate crocodylians. This assemblage is very similar to that collected from the Terlingua (Rowe et al., 1992). Crocodylians, which live in aquatic areas, have been recovered from all the

conglomerates, but are more abundant from the lowest horizons. Both herbivorous and carnivorous dinosaurs have been recovered from the conglomerates and the taxonomic assemblage is very similar to that

of Terlingua (Rowe et al., 1992). The paleoecologies of these dinosaurs, especially of the theropods, is not well constrained. All of these taxa may have lived in and around swamps and marshes, but could also have lived in

more upland areas. CONCLUSIONS Taxonomically, the herpetofauna from the Talley Mt. is very similar to that of the Terlingua local fauna. However, the total number of fossils and

their diversity is lower in the Talley Mt. fauna. This is due partly to taphonomic and sampling bias. The Terlingua fauna was collected from an estuarine deposit, and it produced more fossils and a higher diversity of taxa than the Talley Mt. fauna. The Talley Mt. fauna, with far fewer fossils and

taxa, was sampled from fluvial channels within marshes that were further inland. The amphibians and crocodylians, which were closely tied to an

aquatic environment, clearly decrease (or are absent) higher in the section,

corresponding to the trend seen in the chondrichthyans and actinopterygians. This documents environmental change during the 0.7 My sampled to a less aquatic setting with a decrease in marine influence. However, the more terrestrial taxa (especially the dinosaurs) do not appear to decrease upsection.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. MAMMALS OF THE TALLEY MT. LOCAL FAUNA, UPPER AGUJA FORMATION (LATE CAMPANIAN), BIG BEND NATIONAL PARK, TEXAS INTRODUCTION The mammalian fauna is described from the late Campanian Talley Mt. local fauna of Big Bend National Park, Texas. The fauna was collected from the lower portion of the upper shale member of the Aguja Formation. The fossils were collected by bulk sampling five horizons of carbonate- cemented, pedogenic-nodule conglomerates. Associated

magnetostratigraphic correlations constrain the fauna to the base of Chronozone 32. Approximately 0.7 My (-73.6 to 74.3 Ma) are estimated to have occurred between the lowest and highest conglomerates. Previous environmental interpretations for the Aguja deposits in the area had suggested that the deposits had formed in a coastal setting, ranging from interdistributary marsh-bay facies at the base of the exposed section to

inland floodplain facies at the top (Lehman, 1982, 1985). The five horizons

sampled are from within the lower portion of the section. The mammalian assemblage is used to provide more detailed biostratigraphic information for

these deposits than was previously available.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SYSTEMATIC PALEONTOLOGY Class MAMMALIA Order MULTITUB ERCULATA

Family QMOLOMYIDAE

(Fig. 1.26 A)

Referred Specimens-LSUMG 489:5681. Description—Ml. Tooth is very worn, has indentations at its base,

recurved cusps, and a long 3rd cusp. Comparisons and Discussion—The molar is referred to the

cimolomyids based on the above characteristics. It resembles Cimolomvs clarkii from the Terlingua local fauna (Rowe et al., 1992; Weil, 1992), but is half its size. It also resembles C. milliensis from the Kaiparowits Formation

(J. Eaton, oral comm., 1998). It may even be a new species (A. Weil, oral comm., 1998). However, because there is only one, fragmentary tooth, the species could not be determined. MENISCOESSUS sp.

(Fig. 1.26 B) Referred Specimens-LSUMG 491:5779. Description—Ml (anterior fragment). Tooth has robust cusps with a

pocket toward the front of the tooth. Comparisons and Discussion—The molar is too fragmentary for further identification.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Suborder and Family-INCERTAE SEDIS cf. QMEXOMYS

(Fig. 1.26 C) Referred Specim ens-LSUM G 140:6121. Description—Left ml. Cusps: 4:3. Tooth has a large, U-shaped valley

between the cusps. Comparisons and Discussion—The molar closely resembles Cimexomvs sp. (A. Weil and J. Eaton, oral comm., 1998). It is very similar to

specimens from the Terlingua local fauna that were originally referred to Paracimexomvs sp. (Weil, 1992; fig. 7 A-C), but which have been removed from that taxon (A. Weil, oral comm., 1996). This Cim exom vs taxon is

considered to be very primitive; the U-shaped valley between the cusps is common in Asian multi tuber culates (J. Eaton, oral comm., 1998).

PARACIMEXOMVS sp. (Fig. 1.26 D and E) Referred Specimens-LSUM G 489:5684; 491:5778. Description—V-5778 is a worn RM2. Tooth has a low cusp count, a strong diagonal valley, two central cusps, and internal row with three cusps

with the third cusp offset from the others. V-5684 is a worn anterior

fragment of a PM3; it has a 4:3 cusp pattern. Comparisons and Discussion—V-5778 resembles both Paracimexomvs and Cimexomvs (J. Eaton and A. Weil, oral comm., 1998), but is most similar

to the former. Further identification was not possible because it is so worn. V-5684 is a molar with a 4:3 cusp count and a primitive cusp pattern (L- shaped) and most resembles a very large P. magnus (J. Eaton, oral comm., 1998), but could also be from a new species (R. Cifelli, oral comm., 1998). It is

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. from an unnamed southern taxon that is present in the Terlingua and Wahweap local faunas and from one locality in the San Juan Basin (A. Weil, oral comm., 1998). MULTITUB ERCULATA-INDET.

Referred Specimens-LSUMG 488:5508 (ant. px), 5530 (upper incisor); 140:6138 (ant. px); 489:5683 (p4). Description—These specimens are small fragments of teeth. Comparisons and Discussion—All of these specimens are too fragmentary for further identification. Order MARSUPIALIA Family PERADECTID AE

A LPH A PO N ALPHAPON CF. A. SAHNII

(Fig. 1.26 G) Referred Specimens-LSUMG 489:5679 Description— M2, anterior fragment (metacone). Comparisons and Discussion—The molar fragment is similar to A. cf.

A. sahnii from the Terlingua local fauna (OMNH 25221; Cifelli, 1995), but is

slightly smaller (Cifelli, pers. comm., 1998).

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ALPHAPON A LPH A PO N CF. A- HALLEYI Sahni, 1972

(Fig. 1.26 F) Referred specim ens—LSTJMG 492:6252. Description—Left M3. Comparisons and Discussion—The molar is most similar to A. cf. A. hallevi from the Terlingua local fauna (OMNH 22726); it is considerably bigger than A. perexiguus from the Terlingua (Cifelli, 1995:122). MARSUPIALIA-INDET.

Referred specimens—LSUMG 140:6113 (metacone and metastylar blade), 6115 (tooth fragment), 5584 (right partial molar, trigonid), 6124 (Lm, trigonid); 489:5583 (LM3, posterolabial comer), 5676 (RM, protocone), 5678 (p3?), 5679 (M2? protocone), 5680 (LM1, ant-lab comer/fragment), 5685 (I or

PM); 492:5579 (I or PM); 491:5955 (Lm talonid, very twinned), 5959 (partial M, with paracone and stylocone). Descriptions—These specimens are fragments of incisors, premolars,

and molars. Incisors and premolars are not very diagnostic, and the molar fragments are too fragmentary for further identification.

Comparisons and Discussion—Many of these specimens are probably from the common marsupial genus, Alphadon. but are too fragmentary for this referral. Several of the specimens are from very small marsupials, and may be from the small, A. perexiguus. described from the Terlingua local

fauna (Cifelli, 1995). One specimen (LSUMG 5680) is from a very large molar and may be from the large marsupial, Turgidodon lillegraveni. described

from the Terlingua local fauna (Cifelli, 1995).

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. THERIAN-INDET.

Referred specimens—LSUMG 488:5486,5509,5623; 140:5565,6130,6137,

6157; 489:5540,5541,5586,5587,5652; 491:5543; 492:5559,5585. Description—All specimens are too tiny tooth fragments. Discussion—Specimens are too fragmentary to identify beyond this level. DISCUSSION Six mammalian taxa (multituberculates and marsupials) have been recovered from the conglomerates. The taxonomic composition is similar to

the Terlingua local fauna (Rowe et al., 1992), a similar aged microvertebrate fauna also from the upper shale member of the Aguja. Mammal fossils have

been found from all of the conglomerates (except VL-490), but are very rare and usually very fragmentary. They are most abundant in the second lowest

conglomerate (VL-489/140). The Terlingua local fauna produced considerably more mammalian fossils and taxa than the Talley Mt. local fauna. The Terlingua mammalian assemblage is considered to represent part of the Judithian LMA (Rowe et al., 1992). However, because it contains species that have only been found from the Big Bend area and does not contain many taxa found in similar faunas to the north, it is considered to be very endemic (Rowe et al., 1992; Weil, 1992; Cifelli, 1995).

CONCLUSIONS The mammalian fauna from the Talley Mt. local fauna is similar to that of the Terlingua local fauna, but contains fewer total fossils and a lower diversity of taxa. This is due partly to taphonomic and sampling biases. The Terlingua was collected from an estuarine deposit which produced more

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. fossils and a higher diversity of taxa. The Talley Mt. fauna, with far fewer fossils and taxa, was sampled from fluvial channels within marshes that were further inland. In the Talley Mt. fauna, fewer multituberculate fossils were found than marsupials, but a slightly higher taxonomic diversity of multituberculates is represented. Only marsupial fossils were found from the highest

conglomerates, possibly reflecting a habitat preference to the less aquatic environments higher in the section. This interpretation is supported by the Terlingua fauna, which is from an estuarine deposit and which contained proportionally fewer marsupials.

The mammalian taxa are all represented in the Judithian-aged Terlingua local fauna and in other Judithian faunas further to the north. The magnetostratigraphic correlation to the base of C32 brackets the fauna to the between -73.6 to 74.3 Ma, with -0.7 My between the lowest and highest conglomerates.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CONCLUSIONS The late Campanian Talley Mt. local fauna, from the lower portion of the upper shale member of the Aguja Formation, contains 35 vertebrate taxa of both terrestrial and aquatic environments (shallow marine and brackish to freshwater). The taxa include: 8 chondrichthyans, including 3 sharks; 2 actinopterygians; 3 amphibians; 1 trionychid turtle; 4 lizards; 5 crocodylomorphs; 6 dinosaurs; and 6 mammals (multituberculates and marsupials). Two lizard taxa are new records for the upper Aguja (Chamops and Peneteius sp. nov). The fauna was collected by bulk sampling fossiliferous, pedogenic nodule-rich, carbonate-cemented, conglomeratic rocks from five horizons within the upper Aguja. All five sampled conglomerates formed in channels in marshes within a coastal floodplain. Twenty meters of stratigraphic

thickness separate the lowest and highest sampled conglomeratic horizon. The fossils reflect a change upsection into less aquatic environments; there was almost no marine influence during deposition of the highest

conglomerate (VL-492). Paleoenvironmental reconstructions previously made for these upper Aguja outcrops had been based, in part, on bone accumulations of Deinosuchus riograndensis (Crocodylia), Chasmosaurus mariscalensis and Kritosaurus cf. K. navajovius (Dinosauria), and on fragmentary remains of other vertebrates (Lehman, 1982; 1985; 1989). With more taxa known and from multiple levels, a more complete paleoenvironmental reconstruction is possible. This work has demonstrated that these conglomeratic deposits, common in the upper Aguja Formation, are rich microvertebrate sites. This is an important discovery given the rarity of rich vertebrate microsites in the

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. upper Aguja Formation, and provides a source of vertebrate fossils in areas, such as the Talley Mt. area, where previously only large bones had been found. Conglomeratic horizons are often present at many closely-spaced

stratigraphic levels, providing the rare opportunity to sample for vertebrates at more than one level. This allows more detailed vertebrate biostratigraphy and interpretations of paleoenvironmental conditions for the upper Aguja Formation. However, due to sorting of clasts within the streams that transported the material, the conglomerates mostly contain small fossils, in the size range of small shark and mammal teeth (less than 4 mm in length). Although large pieces of fossil bone and teeth are present in the conglomerates, they are usually too broken to be identified. Sampling such

rocks for vertebrate fossils produces a sample biased towards very small vertebrate bones and teeth. However, if these samples are supplemented by collections of larger bones and teeth, a representative sample of the original fauna is probably assembled. It was expected that the Talley Mt. and Terlingua local faunas, both from the lower portion of the upper shale member of the Aguja Formation,

would be generally similar in taxonomic composition and possibly in age. Taxonomically, the two faunas are very similar and both contain Judithian

mammal taxa. It is not possible, with the current collections, to determine if one fauna is older than the other. Additionally, the Talley Mt. fauna, collected from five horizons spanning 20 m of section, represents ~0.7 My. The Terlingua fauna, collected from only one horizon, represents a

considerably shorter span of time. It is difficult to definitely determine the stratigraphic relationships between the two areas for the following reasons:

140

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1) The two areas are separated by 40 km and there are no continuous Aguja outcrops which might be traced between the two areas. 2) The upper shale member of the Aguja thins to the east; outcrops in the

Terlingua area are considerably thicker than they are in the Talley Mt. area (Lehman, 1985). There are striking differences between the samples of fossils from the

two areas. The Terlingua local fauna was sampled from one unusually fossil- rich horizon from a small fluvial channel within an estuarine setting (Weil, 1992). The horizon has produced hundreds of vertebrate bones and teeth (as well as invertebrate and plant fossils). The vertebrate fossils include a greater variety of sizes, from very small mammal teeth to medium-sized turtle carapace fragments to large dinosaur bones. Remarkably fragile bones from bird and pterosaurs are also present. Based on this size variety and on the

presence of such fragile bones, less fluvial sorting and damage occurred within the Terlingua microsite compared to the Talley Mt. conglomerates. This greater variety in fossil sizes and the presence of even the most fragile bones and teeth is responsible for the larger number of total fossil specimens

preserved and the greater number of taxa (52) represented at the Terlingua microsite. Terlingua's higher taxonomic diversity is a direct result of more

fossils collected (with a greater variety of sizes and durability), so that even

very rare taxa are included in the sample. In order to provide an independent age control for the Talley Mt. fauna, magnetostratigraphic correlations was done. (Isotopic age determination could not be done because there are no igneous rocks or ashes in these deposits). Paleomagnetic samples were collected from very closely- spaced intervals to avoid missing polarity changes of short duration. The

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. polarity sequence is correlated to the base of Chronozone 32, based on the following reasons: 1) The marine Terlingua Creek sandstone member of the Aguja Formation,

which underlies the upper shale member, is within the middle Campanian

(Lehman, 1985; Rowe et al., 1992). 2) The lower portion of the upper shale member of the Aguja Formation is within the late Campanian, based on its vertebrate fossils (Rowe et al., 1992). Both the Terlingua and Talley Mt. local faunas, from localities within this unit, contain Judithian mammal taxa (Cifelli, 1995; Rowe et al., 1992; Sankey,

this paper; Weil, 1992). The Judithian LMA spans the upper part of C33 and

the lower part of C32 (Lillegraven and McKenna, 1986). 3) The uppermost part of the upper shale member of the Aguja Formation is early M aastrichtian (Lehman, 1985; Rowe et al., 1992; Standhardt, 1986). These points constrain the magnetostratigraphic correlations to within

the late Campanian, and within this time, the base of C32 is the only polarity zone known to contain two closely-spaced reversed zones of short duration.

The presence of Judithian mammal taxa within the Talley Mt. and Terlingua

local faunas, further support this correlation. Lehman (1991:15) estimated that the sedimentation rates for the upper shale member of the Aguja Formation ranged from 10-21 m/M y, and averaged -13 m/M y (based on paleomagnetic stratigraphy of younger rocks and on biostratigraphic correlation of vertebrate faunas). However, previous

to this present work, no magnetostratigraphy had been done on the Aguja Formation, so Lehman's estimated sedimentation rates lacked good age control. Based on magnetostratigraphic correlations from the Talley Mt.

1 4 2

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. section, the rates of sedimentation were considerably higher, ranging from 15 to 37 m/M y, and averaging -29 m/My. Using this higher rate of sedimentation (-29 m/My) and the datum,

VL-491 (-74.0 Ma), approximate ages were calculated for the sampled conglomeratic units. These ages range from -73.6 to 74.3 Ma, with a -0.7 My duration between the lowest and highest conglomerates. The entire 52 meter polarity section is -1.8 My (-72.7 to 74.5 Ma). These age estimates are tentative, but are useful at present to focus further research towards testing them. If, after further research, these age estimates are still accepted, then the Talley Mt. fauna will be one of the best age constrained Judithian faunas and the only one that includes several

stratigraphically closely-spaced fossil horizons. If -0.7 My separates the lowest and highest conglomerates, then faunal differences might be detected through the section. Such interpretations are complicated by the fact that very different quantities of conglomeratic rock were collected and processed from each horizon (Appendix II): VL-488 (281 kg); VL-140/489 (-553 kg); VL-491 (304 kg); VL-490 (18 kg); and VL-492 (474 kg).

These sample size differences should be kept in mind when interpreting the presence or absence of taxa. For example, the absence of many taxa from VL-

490 is best explained by its very small sample, and does not reflect any

meaningful difference from the other conglomerates. Additionally, the conglomerates varied greatly in fossil abundance: VL-488 was the least fossiliferous and VL-489/140, the most. However, given the large samples collected from each horizon (except for VL-490), the following general differences are probably real and not due to sampling or taphonomic biases. Environmental interpretations based on the less common vertebrates (such

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. as the lizards) should be viewed with caution because presence or absence of these taxa may be due to sampling or taphonomic factors. The most obvious change is one from a more aquatic environment

with a marine influence (lower in the section) to a less aquatic environment with a weaker marine influence and with drier, more seasonable climates (higher in the section). For example, between the four lowest and the highest

conglomerates there is a dramatic decrease upsection in aquatic taxa (chondrichthyans, actinopterygians, and salamanders); they are extremely rare or absent in the highest conglomerate. In particular, the sharks (Hvbodus sp. and Scapanorhvnchus texanus) which are considered mainly

shallow marine taxa, only occurred in the lowest two conglomerates. The other shark recovered, Lissodus (=Lonchidion) selachos. considered to be a brackish water taxon, is present in all the conglomeratic beds, but only one tooth has been found from the highest conglomerate. The fish give a similar environmental signal. Lepisosteids, considered to be brackish to freshwater taxa, are much less common in the highest conglomerates. The salamanders, Albanerpeton and Scapherpeton. considered to be primarily aquatic, were not

recovered from the highest conglomerate. The more terrestrial vertebrates do not provide as clear a signal for the environmental change. Trionychid turtles (aquatic) have been found from

all conglomerates, but they are very rare from all of them. This rarity is probably more due to the taphonomic bias against large sized vertebrate

fossils in the conglomerates. Lizards are rare and were only recovered from the lowest two conglomerates (with the exception of one tooth from

Peneteius sp. nov.) from the highest conglomerate. The paleoecology of these lizards is not well known and their absence from the higher

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. conglomerates may be more of a sampling or taphonomic relict. Crocodylians, which live in aquatic areas, have been recovered from all the conglomerates, but are more common from the lowest ones. Dinosaurs, both herbivorous and carnivorous, have been found from all the conglomerates. However, the paleoecologies, especially of the theropods, are not well known. Although mammals are very rare, they have been recovered from all the conglomerates (except, VL-490), but are most common from VL-489/140. Their paleoecologies are also not well known, and their abundance lower in the section may be due to taphonomic and sampling biases. Despite the estimated -0.7 My that separate the lowest and highest conglomerates, the fossil samples (especially of the mammals) are too small and fragmentary to use to detect any taxonomic differences among the conglomerates. Lumping the fossils from all the conglomerates together, the fauna is very similar in taxonomic composition to the Terlingua local fauna, and both faunas contain Judithian mammal taxa. However, it is not possible with the collections to determine whether one fauna is older or younger than the other or where within the Judithian LMA these faunas occur.

Although the sample of mammal fossils from the conglomerates is very small and fragmentary, two observations are possible. First, although

considerably fewer multituberculate fossils were found compared to marsupials, more multituberculate taxa are represented, possibly reflecting a greater taxonomic diversity among the multituberculates during this time. Second, only marsupials were found from the highest conglomerates, possibly reflecting a habitat preference to less aquatic environments or to the different vegetation further inland.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Additional approaches can be pursued in the future to answer other questions such as: 1) What is the paleomagnetic polarity zonation for the section that contains the Terlingua fauna? 2) What are the radiometric ages for the newly discovered ashes in the uppermost Aguja (Lehman, pers. comm., 1998)? Do the dates alter or support the magnetostratigraphic interpretations presented here?

1 4 6

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SUMMARY The major results and conclusions of this research are the following: 1. The Talley Mt. 52 meter magnetic polarity sequence (from the lower part of

the upper shale member of the Aguja Formation) contains two reversed

polarity zones, and are correlated to the base of Chronozone 32, C32r.2 and C32r.l, respectively. 1) Magnetic correlations were constrained by the ages of the

Aguja Formation, based on its invertebrate and vertebrate faunas, and by the Judithian mammals in the Talley Mt. fauna. 2) Estimated sedimentation rates for the lower part of the upper shale member of the upper Aguja Formation were -29 m /M y in the Talley Mt. area. 3) Based on this sedimentation rate and on the magnetostratigraphic correlations, the following values were calculated for the Talley Mt. polarity section: -52 m eter polarity section: -72.7 to 74.5 Ma (—1.8 My) -Five sampled conglomerates: -73.6 to 74.3 Ma (-0.7 My)

VL-492: -73.6 Ma VL-490: -73.9 Ma

VL-491: -74.0 Ma

VL-489/140: -74.2 Ma VL-488: -74.3 Ma 2. The Talley Mt. local fauna (acquired by disaggregating five carbonate- cemented, conglomeratic channel deposits spanning 20 meters of section):

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1) Contains 35 vertebrate taxa, including: 8 chondrichthyans, 2 actinopterygians, 3 amphibians, 1 trionychid turtle, 4 squamates, 5 crocodylomorphs, 6 dinosaurs,

and 6 mammals. 2) Conglomeratic units are rich microvertebrate sites, and are common within the upper Aguja Formation at multiple stratigraphic levels. Due to fluvial transport, samples of vertebrate fossils are biased towards small size (<4 mm) and of high durability. 3) Within the Talley Mt. fauna, aquatic taxa decrease in abundance upsection, reflecting both the marine regression from the area

and the existence of dry seasons. 4) The Talley Mt. and Terlingua local faunas are taxonomically similar. Differences between them were caused by different depositional environments and taphonomic histories. 5) The Talley Mt. local fauna is the second Judithian fauna from west Texas. It is one of the only southern Judithian faunas associated

with magnetostratigraphy.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. REFERENCES CITED

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDIX I PALEOMAGNETIC RESULTS The following figures show the paleomagnetic results for all the

samples collected from the 52-m section in the Talley M t field area (JS-1; Fig. 1.9,1.10,1.11,1.14,1.15). Samples are numbered in the following way: 52.1 is the first sample from site 52 (at meter level 52). Each page contains the

following: top left, As-Zijderveldt diagrams (explanation in Fig. 1.12); top right, all the thermal demagnetization steps; middle right, equal area plots; and bottom, intensity vs. demagnetization diagrams of samples during demagnetization.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. AGUJA NRM - 5.83E-07 STEP DECL INCL AMP NSC 1 NRM 100..4 -26..9 0. 32 2 TD150 171..5 -56..2 0..96 3 TD200 173 .6 -55. .2 0..99 4 TD300 171 .8 -59..0 1..00 5 TD350 177 .6 -56..8 0..91 6 TD400 174 .2 -54. .5 0..67 7 TD400 171 .4 -53..9 0..66 8 TD450 205 .6 -68..3 0..23 9 TD550 291.3 -85..6 0..12 10 TD600 344 .7 -31..9 0..08 W.-H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 3.84E-06 N T U ACUJA 1.1 AMP NSC STEP DECL INCL 1 NRM 98.4 -1.7 1.00 2 TD150 187.9 -37.4 0.10 3 TD200 174.2 -38.1 0.11 4 TD300 186.2 -47.8 0.10 5 TO3S0 197.0 -42.0 0.07 6 TD400 184.6 -42.4 0.05 7 TD450 204.4 -45.5 0.0 3 8 TD550 220.4 -47.4 0.00 9 TD600 146.8 -68.3 0.01 H.-H £

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.58E-06 NSC STEP DECL INCL AMP 1 NRM 350.2 5.2 1.00 2 TD150 139.7 -51.3 0.29 3 TO200 157.3 -45.7 0.32 4 TD300 141.4 -69.9 0.25 5 TD350 145.5 -67.1 0.13 6 TD400 108.2 -62.6 0.09 7 TD450 141.9 -57.8 0.07 8 TD550 110.3 -44.9 0.02 9 TD600 48.9 61.4 0.01 E.+H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 7.30E-07 INCL AMP NSC STEP DEC-t 1 NRM 179.2 -6.6 0.96 2 TD150 177.2 -3.3 1.00 3 TD200 184.3 -24.8 0.89 4 TD300 182.2 -23.8 0.69 5 TD350 186.5 -16.2 0.59 6 TD400 171.0 -32.9 0.26 7 TD450 170.6 -47.0 0.17 8 TD550 164.5 -56.7 0.06 9 TD600 41.8 51.8 0.04 W.-H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 5.10E-07 INCL AMP NSC STEP DEGL 1 NRM 186.5 -41.9 1.00 z TD150 192.9 -28.3 0.98 3 TD200 189.5 -18.3 0.88 4 TD300 179.2 -24.8 0.94 5 T0350 201.3 -32.2 0.46 6 TD400 205.0 -26.4 0.30 7 TD450 194.5 -44.8 0.18 8 TD550 220.3 0.4 0.16 9 TD600 138.5 44.6 0.03 W.-H E, +H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 3.82E-07 AMP NSC STEP DECL INCL 1 NRM 200.7 -13.4 0.81 2 TD150 201.9 -28.0 1.00 3 TD200 203.8 -34.7 0.97 4 TD300 194.6 -30.8 0.73 5 TD3S0 210.9 -31.2 0.54 6 TD400 208.6 -35.5 0.43 7 TD450 214.5 -39.0 0.30 8 TD550 208.8 -5.2 0.25 9 TD600 354.4 24.0 0.04 W.-H T3T

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 8.16E-07 NSC STEP DECL INCL AMP 1 NRM 353.3 54.5 1.00 2 TD150 353.1 46.4 0.29 3 TD200 348.0 34.6 0.17 4 TD300 264.9 25.3 0.17 5 TO350 170.6 71.2 0.22 6 TD400 165.1 44.8 0.43 7 TD450 170.9 73.1 0.28 8 TD5S0 144.8 56.4 0.36 9 TD600 113.0 74.6 0.16 W.-H E.+H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.00E-07 DEC4. INCL AMP NSC STEP 1 NRM 175.6 35.0 0.24 2 TD150 172.1 -77.5 0.64 3 TD200 158.7 -67.3 1.00 4 TD300 208.6 -73.1 0.98 5 TD350 220-7 -44.7 1.00 6 TD400 224.2 -47.8 0.72 7 TD450 239.1 -38.7 0.65 8 TD550 287.5 -54.9 0.35 9 TD600 169.3 10.8 0.07

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.12E-06 AMP NSC STEP DEC-t INCL 1 NRM 177.8 45.8 0.69 2 TD150 192.1 3.9 0.94 3 TD200 195.9 2.2 1.00 4 TD300 205.2 -1.1 0.71 5 TD350 225.6 45.6 0.42 6 TO400 234.3 53.7 0.27 7 TD450 273.4 57.6 0.21 S TD550 17.5 50.9 0.14 9 TD600 340.1 17.6 0.06 W,-H E.+H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.74E-07 NSC STEP OECL INCL AMP 1 NRM 97.6 -11.3 1.00 2 TD150 149.6 -41.0 0.77 3 TD200 170.2 -25.5 0.93 4 TD300 158.0 -44.8 0.94 5 TD350 165.5 -51.9 0.44 6 TD400 141.7 -46.0 0.40 7 TD450 130.6 -51.4 0.18 8 TD5S0 99.5 -36.7 0.38 9 TD600 19.3 -19.3 0.14 W, -H E.+H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.23E-07 AMP NSC STEP 0E6L INCl 1 NRM 289.9 -41.1 0.71 2 TD150 198.2 -64.9 0.78 3 TD200 173.8 -54.6 1.00 4 TD300 192.7 -64.9 0.87 5 TD350 182.0 -50.7 0.51 6 TD400 165.3 -68.9 0.39 7 TD450 126.6 -55.2 0.29 8 TD550 142.8 12.8 0.27 9 TD600 354.8 -0.2 0.14 N.-H E.+H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 2.09E-07 NSC STEP DECL INCL AMP 1 NRM 127.8 -36.9 1.00 2 TD150 139.0 -70.2 0.85 3 TD200 124.5 -49.0 0.74 4 TD300 139.4 -55.5 0.77 5 TD350 142.7 -52.1 0.68 6 TD400 123.8 -50.5 0.41 7 TD4S0 124.8 -47.8 0.32 8 TD550 74.6 7.1 0.39 9 TD600 353.2 51.0 0.10 W, -H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. AGUJA 5.1 NRM - 4.28E-06 INCL AMP NSC STEP OEGL NRM 341.7 36.1 1.00 TD150 103.2 -46.5 0.21 TD200 112.9 -45.0 0.23 TD300 113.5 -44.8 0.24 TD350 119.5 -46.6 0.20 TD400 121.3 -49.4 0.13 TD450 119.3 -80.9 0.05 TD5S0 329.3 -54.2 0.01 TD600 329.1 6.2 0.03 W.-H E.+H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.29E-05 NSC STEP DECt INCL AMP 1 NRM 334.8 34.7 1.00 ? TD150 103.9 -50.9 0.06 i TD200 111.2 -48.8 0.07 4 TD300 116.3 -47.2 0.07 5 TD350 117.3 -55.3 0.03 6 TD400 118.1 -68.7 0.02 7 TD450 302.9 -70.7 0.01 8 TD550 322.2 -20.3 0.01 9 TD600 318.3 23.7 0.00 W, E.+H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 2.38E-06 NSC STEP DECt INCL AMP 1 NRM 56.7 6.4 1.00 2 TD150 57.4 4.9 0.70 3 TD200 60.8 5.4 0.60 4 TD300 54.1 6.9 0.43 5 TD350 SI.4 10.0 0.35 6 TD400 45.6 13.0 0.28 7 TD450 29.9 16.1 0.21 8 TO550 357.2 26.3 0.19 9 TD600 344.8 45.9 0.10 +H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. *

NRM - 1.04E-06 NSC STEP DECt INCl AMP 1 NRM 179.8 57.7 1.00 z TD150 182.0 48.6 0.58 3 TDZ00 173.3 51.2 0.42 4 TD300 193.0 59.8 0.32 5 TD350 182.9 72.9 0.22 6 TD400 248.1 55.1 0.21 7 TD450 302.2 17.3 0.29 8 TD550 301.1 75.4 0.10 9 TD600 16.5 2.1 0.07 W.-H E.+H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.24E-06 DECL INCL AMP NSC STEP 1 NRM 98.1 35.3 1.00 2 TD150 94.2 24.6 0.70 3 TO200 92.8 23.9 0.65 4 TO300 80.5 23.2 0.51 5 TD350 75.9 22.7 0.42 6 TD400 76.3 21.5 0.34 7 TD450 78.8 18.7 0.24 8 TD550 44.0 27.9 0.24 9 TD600 84.5 2.2 0.16 W.-H E.+H

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176

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 5.22E-07 DEO. INCL AMP NSC STEP 1 NRM 89.9 40.1 1.00 2 TD150 83.2 -1.9 0.61 3 TD200 88.1 -15.0 0.55 4 TD300 59.9 -42.9 0.32 5 TO350 11.4 -63.9 0.35 6 TD400 343.5 -75.8 0.34 7 TD450 257.5 -70.8 0.41 8 TD550 186.7 0.8 0.57 9 TD600 248.2 44.4 0.29 W.-H E,+H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.23E-06 DECl. INCL AMP NSC STEP 1 NRM 18.5 -8.1 1.00 2 TD150 29.3 -29.5 0.60 3 TD200 39.4 -35.9 0.52 4 TD300 35.5 -37.5 0.47 5 TO350 31.0 -39.1 0.46 6 TD400 22.0 -38.8 0.46 7 TD450 19.9 -39.2 0.47 8 TD550 13.6 -48.1 0.24 9 TD600 0.4 43.6 0.11 W.-H

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178

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.37E-06 AMP NSC STEP DE61. INCl 1 NRM 191.8 -6.5 0.93 2 TD150 192.2 -11.4 1.00 3 TO200 189.9 -8.8 0.96 4 TD300 191.3 -7.1 0.71 5 TD350 201.5 -1.2 0.63 6 TD400 195.2 1.4 0.42 7 TD450 178.6 15.9 0.26 8 TD550 242.7 -14.8 0.13 9 TD600 260.6 21.8 0.12 W,-H

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179

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. AGUJA 11.3.1 NRM - 6.40E-07 INCL AMP NSC STEP DECL 1 NRM 2.2 43.3 1.00 2 TO150 1.3 43.3 0.67 3 TD200 346.6 42.9 0.51 4 TO300 342.0 41.S 0.41 5 TD350 349.1 39.8 0.41 6 TD400 336.2 32.5 0.38 7 TD4S0 336.8 32.3 0.43 S TO550 320.9 31.5 0.33 9 TD600 0.4 27.8 0.12 W, -H E.+H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.56E-06 . AGUJA 11.3.2 NSC STEP DECL INCL AMP 1 NRM 29.5 15.6 1.00 2 TD150 29.1 5.2 0.63 3 TD200 29.2 -1.5 0.49 4 TD300 19.3 -1.4 0.46 5 TD3S0 12.0 0.1 0.44 6 TD400 353.9 2.7 0.42 7 TD450 352.8 4.9 0.47 8 TDS50 356.7 -2.7 0.41 9 TD600 350.8 -2.1 0.22 W, E.+H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.64E-06 AMP NSC STEP DEGt. INCL 1 NRM 329.3 49.9 1.00 2 TO150 321.7 36.1 0.79 3 TD200 331.8 39.3 0.68 4 TD300 338.6 47.4 0.38 S TD350 352.4 63.5 0.24 6 TD400 126.4 71.6 0.17 7 TD450 137.6 34.S 0.17 8 TD550 116.4 31.0 0.19 9 TD600 119.7 45.7 0.16 W.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 8.95E-07 AGUJA 12.9.1 NSC STEP DEC-t INCL AMP 1 NRM 373.7 31.1 1.00 2 TD150 372.9 20.2 0.50 3 TD200 7.1 10.9 0.35 4 TD300 1.2 9.1 0.39 5 TD350 356.9 15.5 0.48 6 TD400 353.7 8.0 0.49 7 TD450 350.7 7.5 0.53 8 TD550 344.8 18.3 0.38 9 TD600 330.7 5.9 0.17 W,

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. .AGUJA 14.1 NRM - 1.07E-06 DEC! INCL AMP NSC STEP NRM 120.6 66.9 1.00 TD150 157.1 13.7 0.59 TD200 161.4 6.4 0.52 TD300 147.2 10.8 0.26 TD350 164.2 57.3 0.26 TD400 134.1 66.8 0.14 TD450 25.9 85.7 0.16 TD5S0 1.9 74.4 0.11 TD600 236.9 42.7 0.04 W.-H E.+H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. AGUJA 14.2 NRM - 1.02E-06 OECt INCL AMP NSC STEP 1 NRM 219.6 62.9 1.00 2 TD150 210.2 13.5 0.79 3 TD200 210.7 -1.7 0.58 4 TD300 250.5 8.8 0.28 5 TD350 301.9 28.4 0.32 6 TD400 311.5 21.8 0.34 7 TD450 313.1 21.8 0.40 8 TD550 334.4 9.7 0.28 9 TD600 2.0 -1.0 0.08 W.-H E.+H

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185

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.14E-06 NSC STEP DECL INCL AMP 1 NRM 52.4 48.8 1.00 2 TD150 147.8 -15.1 0.25 3 TD200 168.1 -22.2 0.27 4 TD300 180.0 -31.6 0.19 5 TD350 191.9 -35.5 0.10 6 TO400 208.7 -46.9 0.07 7 TD450 293.7 -12.8 0.08 8 TD550 318.1 -6.3 0.04 9 TD600 68.8 -68.3 0.0S W.-H E.+H

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186

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. AGUJA 15.2 NRM - 2.66E-07 INCL AMP NSC STEP DEO. NRM 34.8 9.9 1.00 TD150 76.8 -72.1 0.94 TD200 145.4 -74.5 0.99 TD300 84.6 -84.1 0.81 TD350 355.1 -74.9 0.76 TO400 348.0 -75.8 0.66 TD450 350.1 -61.3 0.51 TD550 234.7 -14.5 0.29 TD600 56.1 48.3 0.13 W.-H E.+H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.01E-06 NSC STEP DEC! INCL AMP 1 NRM 98.5 43.0 1.00 z TD150 129.6 24.9 0.63 3 TD200 137.7 13.4 0.52 4 TD300 143.6 23.0 0.27 5 TD350 121.1 55.5 0.24 6 TD400 117.9 60.0 0.16 7 TD4S0 8.1 56.1 0.15 8 TD550 356.3 -1.1 0.10 9 TD600 90.7 -0.6 0.04 H.-H E, +H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.36E-06 NSC STEP DEO. INCL AMP 1 NRM 100.7 43.2 1.00 2 TO150 99.9 12.6 0.46 3 TD200 98.4 -5.2 0.35 4 TD300 60.6 -31.6 0.17 5 TD350 17.1 -23.5 0.16 6 TD400 350.2 -33.5 0.15 7 TD450 350.3 -22.1 0.13 8 TD550 339.2 -10.0 0.11 9 TD600 352.2 -8.2 0.05 W. E.+H

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189

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. AGUJA 17.2 NRM - 1.83E-06 AMP NSC STEP OECL INCL 1 NRM 25.0 13.6 1.00 2 TD150 29.7 6.6 0.67 3 TD200 33.3 6.6 0.53 4 TD300 12.1 8.5 0.27 5 TD350 1.6 16.9 0.23 6 TD400 343.1 34.5 0.20 7 TD450 315.1 51.4 0.14 8 TD550 268.0 51.5 0.09 9 TD600 335.5 33.7 0.10

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 4.37E-07 NSC STEP DEC-C INCL AMP 1 NRM 156.1 55.7 1.00 2 TD150 173.3 21.4 0.85 3 TD200 174.9 0.1 0.97 4 TD300 165.9 -9.6 0.43 5 TO350 164.6 -4.5 0.26 6 TD400 73.8 -39.1 0.19 7 TD450 154.0 -26.4 0.10 S TD550 100.7 -27.0 0.16 9 TD600 7.5 -30.7 0.20 W,-H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 7.33E-07 OECL INCl AMP NSC STEP 1 NRM 259.2 11.8 1.00 2 TD150 241.0 7.6 0.82 3 TD200 232.7 6.9 0.80 4 TD300 264.3 23.8 0.49 5 TD350 245.8 37.7 0.51 6 TD400 268.4 34.1 0.41 7 TD450 269.7 25.9 0.34 8 TD550 265.7 28.4 0.28 9 TD600 240.0 38.2 0.23 W.-H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 2.63E-06 AGUJA 19.1 AMP NSC STEP DEO- INCL 1 NRM 178.6 -2.4 1.00 2 TD1S0 175.8 -11.5 0.75 3 TD200 172.6 -14.8 0.66 4 TD300 183.8 -23.4 0.41 5 TD350 195.0 -28.6 0.31 6 TD400 208.3 -21.8 0.21 7 TD450 227.9 -27.1 0.17 8 TD550 260.7 -14.7 0.09 9 TD600 253.7 27.4 0.07 W,-H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.45E-06 INCL AMP NSC STEP DECL 1 NRM 112.3 63.2 1.00 2 TD150 138.1 59.8 0.65 3 TD200 139.2 53.1 0.52 4 TD300 143.3 46.3 0.35 5 TD350 131.8 49.2 0.27 6 TD400 138.3 50.3 0.20 7 TD450 130.8 52.5 0.12 8 TD550 160.5 48.4 0.16 9 TD600 27.3 -1.9 0.03 W, -H

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194

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. AGUJA 20.1 NRM . 1.81E-06 STEP DECL INCL AMP NSC NRM 217.8 17.9 1.00 TD1S0 219.5 16.9 0.86 TD200 221.1 IS.8 0.71 TD300 227.4 23.4 0.44 TD350 254.9 50.0 0.26 TD400 276.3 53.6 0.16 TO4S0 310.8 53.4 0.20 TD550 302.3 45.7 0.18 TD600 162.0 -0.3 0.0S H.-H

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195

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACUJA 20.2 NRM - 1.53E-06 DECL INCL AMP NSC STEP NRM 216.7 3.3 1.00 TD150 219.6 -4.6 0.87 TO200 220.1 -7.7 0.74 TO300 235.6 -6.9 0.43 TD3S0 249.6 -4.5 0.25 TD400 263.7 -17.5 0.21 TD450 276.9 -29.8 0.20 TD550 260.5 3.6 0.11 TD600 187.0 -28.1 0.05

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196

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.20E-07 NSC STEP DECtr INCL AMP 1 NRM 320.7 14.7 0.46 2 TD150 231.3 -37.4 0.76 3 TD200 226.0 -39.4 1.00

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 4.01E-07 INCL AMP NSC STEP DECL 1 NRM 91.2 63.1 1.00 2 TD150 182.4 21.5 0.57 3 TD200 200.1 10.5 0.68 4 TD300 200.2 18.3 0.49 5 TD350 212.1 35.6 0.51 6 TD400 212.3 12.0 0.44 7 TD450 229.0 8.0 0.25 8 TD550 273.0 24.2 0.23 9 TD600 14.1 4.7 0.19

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 2.05E-06 NSC STEP DEC-L INCL AMP 1 NRM 182.1 3S.3 1.00 2 TD150 189.7 21.8 0.78 3 TD200 186.4 20.0 0.69 4 TD300 206.1 21.5 0.43 5 TD350 202.6 17.8 0.37 6 TD400 216.6 18.7 0.27 7 TD450 228.2 12.7 0.25 8 TD5S0 242.3 23.0 0.14 9 TD600 261.3 9.0 0.03 W.-H

INTENSITY VS. DEMAGNETIZATION

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.05E-06 AMP NSC STEP 0ECL INCL 1 NRM 4.6 46.0 1.00 2 TD150 10.4 41.6 0.58 3 TD200 18.0 41.6 0.40 4 TD300 9.4 23.0 0.30 S TD350 18.5 27.7 0.32 6 TD400 9.8 17.8 0.34 7 TD4S0 0.1 20.9 0.25 8 TD550 28.8 41.0 0.19 9 TD600 185.7 -6.4 0.17 W.

INTENSITY VS. DEMAGNETIZATION

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200

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.20E-06 NSC STEP DEC-l INCL AMP 1 NRM 41.0 51.4 1.00 2 TD150 65.8 49.8 0.64 3 TD200 80.3 49.3 0.55 4 TD300 7 8.2 44.9 0.49 5 TD350 72.9 46.4 0.52 6 TD400 67.2 47.4 0.44 7 TD450 57.3 54.8 0.42 8 TDS50 57.9 51.8 0.37 9 TD600 82.7 5.7 0.18

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201

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACUJA 24.1 NRM - 1.22E-07 INCL AMP NSC STEP DEQL 1 NRM 186.2 58.0 0.73 2 TD150 198.6 -41.2 0.41 3 TD200 196.0 -39.8 0.78 4 TD300 319.5 -18.8 0.33 5 TD350 329.7 3.0 0.60 6 TD400 342.5 6.6 1.00 7 TD450 326.5 11.7 0.60 8 TD550 321.3 14.2 0.73 9 TD600 315.9 21.5 0.99

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202

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 6.60E-07 NSC STEP DEC-l INCL AMP 1 NRM 78.1 16.2 1.00 2 TD150 95.4 -3.6 0.62 3 TD200 110.3 -12.4 0.52 4 TD300 107. 7 -24.5 0.28 5 TD350 94.7 -3.3 0.20 6 TD400 81.3 -28.1 0.21 7 TD450 48.0 -7.4 0.12 8 TDSS0 85.4 21.6 0.14 9 TD600 327.9 68.3 0.17 W,-H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 3.45E-07 DECL INCL AMP NSC STEP 1 NRM 305.5 66.8 1.00 2 TD150 160.8 -34.3 0.57 3 TDZ00 146.7 -37.3 0.75 4 TD300 114.3 -40.1 0.70 5 TD350 108.3 -41.8 0.56' 6 TD400 97.5 -37.7 0.62 7 TD450 87.9 -31.9 0.49 8 TD550 81.7 -22.5 0.45 9 TD600 88.3 51.7 0.15 *».

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 8.72E-07 INCL AMP NSC STEP DECL 1 NRM 241.2 67.3 1.00 2 TD150 221.8 10.7 0.58 3 TD200 220.7 -0.6 0.61 4 TD300 247.1 -7.6 0.38 5 TD350 241.1 -5.9 0.39 6 TD400 253.6 -10.7 0.42 7 TD450 265.8 -8.9 0.39 8 TD550 283.2 12.6 0.35 9 TD600 269.7 63.2 0.14

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205

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 7.91E-07 AMP NSC STEP DEGL INCL 1 NRM 71.2 35.3 1.00 2 TD150 92.4 4.8 0.53 3 TD200 100.7 -0.8 0.40 4 TO300 108.6 -34.8 0.27 5 TD350 124.7 -48.0 0.20 6 TD400 92.2 -77.2 0.15 7 TD450 332.3 -40.8 0.15 8 TDS50 355.2 3.3 0.10 9 TD600 157.1 79.4 0.09 W,

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.71E-06 NSC STEP DECL INCL AMP 1 NRM 58.4 4.7 1.00 2 TD150 84. 8 -12.8 0.69 3 TD200 94.6 -12.3 0.65 4 TD300 112.3 -16.9 0.49 5 TD350 106.8 -18.7 0.40 6 TD400 110.S -18.0 0.33 7 TD450 111.9 -15.5 0.27 8 TD550 125.5 -8.9 0.13 9 TD600 124.3 -41.8 0.04 W.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. AGUJA 28.1 NRM - 1.94E-06 AMP NSC STEP DECL INCL 1 NRM 7.8 10.8 1.00 2 TD150 1.0 2.0 0.78 3 TD200 357.7 0.6 0.70 4 TD300 356.7 -2.3 0.60 5 TD350 351.8 -1.5 0.58 6 TD400 349.4 -2.5 0.53 7 TD450 345.5 -1.7 0.46 8 TD550 352.6 0.1 0.25 9 TD600 348.0 -15.2 0.06 W,

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 9.49E-07 NSC STEP DECL INCL AMP 1 NRM 89.8 10.3 1.00 2 TD1S0 95.3 -8.0 0.58 3 TD200 101.9 -10.1 0.55 4 TD300 104.8 -20.4 0.43 5 TD350 69.5 -23.6 0.20 6 TD400 60.0 -14.8 0.16 7 TD450 64.8 -2.8 0.20 8 TD550 59.8 -1.9 0.13 9 TD600 47.3 -2.9 0.05 W.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 8.98E-07 INCL AMP NSC STEP DEC-l 1 NRM 39.6 22.5 1.00 2 TD1S0 34.2 -2.7 0. 44 3 TD200 34.6 -10.8 0.35 4 TD300 63.6 -26.0 0.37 5 TO350 34.1 -25.0 0.24 6 TD400 32.5 -22.6 0.26 7 TO450 37.1 -19.1 0.24 8 TD550 36.2 -13.2 0. 18 9 TD600 201.8 24.4 0.06 W.

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210

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.89E-06 DE6L INCl AMP NSC STEP 1 NRM 19.4 26.5 1.00 2 TD150 23.9 12.4 0.76 3 TD200 24.7 14.1 0.63 4 TD300 27.9 16.7 0.47 5 TD350 23.0 15.9 0.42 6 TD400 18.1 18.0 0.30 7 TD450 17.8 20.1 0.29 8 TD550 356.0 29.9 0.21 9 TD600 85.2 16.4 0.06 W,

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 9.41E-07 AMP NSC STEP DECL INCL 1 NRM 54.4 -51.6 1.00 2 TD150 14.7 -37.0 0.34 3 TD200 339.0 -16.0 0.22 4 TD300 356.3 -18.1 0.12 5 TD350 313.6 34.4 0.35 6 TD400 322.5 32.1 0.33 7 TD450 331.0 -1.3 0.27 8 TD550 358.1 16.9 0.25 9 TD600 334.9 14.7 0.33 W. E.+H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. AGUJA 29.7.2 NRM - 2.06E-06 INCL AMP NSC STEP DECL 1 NRM 1074 34.2 1.00 2 TD150 29. S 43.0 0.43 3 TD200 39.0 58.1 0.33 4 TD300 6.4 41.5 0.29 5 TD350 35.9 47.3 0.34 6 TD400 21.2 47.3 0.26 7 TD450 6.1 22.6 0.21 8 TDS50 340.7 21.2 0.23 9 TD600 299.3 15.5 0.11 W.-H E.+H

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. AGUJA 29.7.3 NRM - 7.53E-07 DECL INCL AMP NSC STEP 1 NRM 20.7 15.2 1.00 2 TD1S0 59.0 23.2 0.69 3 TD200 62.8 23.1 0.62 4 TD300 59.9 10.7 0.62 S TD350 86.9 6.2 0.53 6 TD400 101.1 9.2 0.48 7 TD450 106.4 -2.3 0.33 8 TO550 101.9 -4.0 0.29 9 TD600 219.9 45.3 0.06 W.-H

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214

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 6.84E-06 INCL AMP NSC STEP DECL 1 NRM 82.8 -2.9 1.00 2 TD150 87.7 -8.2 0.87 3 TD200 91.4 -8.7 0.80 4 TO300 90.8 -7.8 0.59 5 TD350 85.6 -7.3 0.42 6 TD400 82.0 -5.9 0.25 7 TD450 85.8 -4.2 0.15 8 TD550 92.0 -12.9 0.05 9 TD600 144.6 -40.8 0.01 W,

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 4.81E-05 NSC STEP OECL INCl AMP 1 NRM 117.4 -0.5 1.00 2 TD150 124.4 -1.6 0.89 3 TD200 123.7 -1.0 0.80 4 TD300 123.6 -0.9 0.52 5 TD350 123.2 0.2 0.38 6 TD400 119.1 -0.4 0.26 7 TO450 120.4 -0.2 0.16 8 TD550 116.6 7.3 0.02 9 TD600 141.4 -23.3 0.00 W.

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 2.95E-06 INCL AMP NSC STEP DECL 1 NRM 46.2 21.7 1.00 2 TD150 75.8 13.7 0.71 3 TD200 74.5 13.0 0.52 4 TD300 63.6 17.6 0.29 5 TD350 70.6 20.9 0.23 6 TD400 72.0 14.4 0.15 7 TD450 55.1 18.5 0.11 8 TD550 68.3 24.7 0.06 9 TD600 206.8 -79.2 0.06 W.

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217

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 9.97E-07 NSC STEP DECL INCL AMP 1 NRM 54.8 40.4 1.00 z TD150 73.0 21.7 0.55 3 TD200 84.4 11.6 0.44 4 TD300 56.3 6.9 0.15 5 TD350 59.0 -63.5 0.12 6 TD400 81.7 -71.3 0.18 7 TD450 33.2 -28.1 0.12 8 TD550 94.0 37.7 0.04 9 TD600 146.1 59.4 0.15

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.85E-06 NSC STEP DECL INCL AMP 1 NRM 101.8 3.2 1.00 2 TD150 100.9 -15.5 0.68 3 TD200 94.3 -22.3 0.54 4 TD300 91.4 -36.2 0.23 5 TD350 123.8 -22.7 0.17 6 TD400 150.2 -11.7 0.12 7 TD450 163.8 -2.2 0.14 8 TD550 156.8 -18.6 0.06 9 TO600 64.0 24.7 0.04 W,

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 2.16E-06 AMP NSC STEP DECL INCL 1 NRM 47.3 16.2 1.00 2 TD150 55.0 10.7 0.67 3 TD200 60.0 7.8 0.47 4 TD300 57.3 9.2 0.29 5 TD350 56.1 18.9 0.19 6 TD400 51.4 9.3 0.12 7 TD450 54.9 1.7 0.09 8 TD550 64.1 -18.7 0.07 9 TD600 182.7 -13.3 0.02 W.

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220

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.62E-06 NSC STEP DE6L INCL AMP 1 NRM 56.0 41.2 1.00 2 TD150 61.0 27.6 0.69 3 TD200 67.5 28.1 0.59 4 TD300 70.0 38.2 0.23 S TO350 53.9 28.0 0.19 6 TD400 34.0 28.0 0.12 7 TD4S0 56.4 51.8 0.08 8 TO550 58.4 12.5 0.12 9 TD600 158.1 1.5 0.08 *»,

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 3.86E-06 NSC STEP DECL INCL AMP 1 NRM 352.9 -12.9 1.00 2 TD150 347.8 -16.6 0.78 3 TD300 346.3 -18.9 0.39 4 TD350 351.3 -16.5 0.30 S TD400 342.6 -16.4 0.22 6 TO450 340.3 -10.2 0.14 7 TD550 326.1 -1.1 0.08 8 TD600 15.4 37.4 0.01

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. NRM - 1.92E-06 NSC STEP DEEt INCL AMP 1 NRM 13.8 51.2 1.00 2 TD1S0 22.0 56.4 0.69 3 TD300 18.8 63.4 0.37 4 TD350 17.1 60.9 0.30 5 TD400 350.1 65.4 0.21 6 TD450 348.4 60.5 0.19 7 TD550 345.0 48.4 0.16 8 TD600 187.4 40.9 0.03

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Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. -1753.4 123.9 Totals VL- 492 490.3 1.0 9.6 43.3 VL- 490

-19months -3 months -10 months 22.9 .20.1 16.2 326.1 18.1 491 304.2 17.9 474.1 -1630.5 4.3 VL- APPENDIX II -181? -181? — VL-140 - CONGLOMERATES SAMPLED CONGLOMERATES ...... -22 months 8.6 489 372.4 w 19.8 2 yrs 280.8 VL- 488 30-mesh This table shows the weights of conglomeratic rocks sampled and matrix picked from the Talley Mt. field of 140 140 and VL-489 are samples from the same conglomeratic horizon. Although weights for VL-140 (collected Rockcollected (kg) 352.9 385 Voucherkept (kg) 72.1Amount rock soaked (kg) Amount matrix picked (kg) 12.6 0 during 1984) were not kept, we estimate that approximately 400 lbs (181 kg) were collected. At total of -1,770 Commons liters gallons) (467 of acetic add were used to break down these -1630 kg of rocks. Over 361 hours were spent Total time area (locations of conglomerates are shown in Fig. 1.10 and their stratigraphic levels in Fig. 1.11). Note that VL- picking the resulting 30-m matrix.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. oval oval oval oval sectional shape Cross- ID-oval (Appendix III continued) ~8 (vv small) ~4 (v.v. small) oval ~5 (ie, v. small M axim um num ber of denticles/mm carinae on anterior 7 5 5 num ber of denticles/mm 4 M axim um carinae on posterior 4 — 3.2 — 3.7 M axim um FABL (mm) 9 APPENDIX III III APPENDIX ““ ““ (mm) Total length MEASUREMENTS OF SAURORNITHOLESTES TEETH near base base near tip tip base Position of fragment within tooth base Measurements of Saurornitholestes teeth follow those of Currie et al. (1990). Values for the specimens 140:6185 140:6186 140:6183 140:6184 140:6139 LSUMNS LSUMNS LSUMNS LSUMNS LSUMNS Specimen # LSUMNS 488:5483 from TMP (Tyrrell Museum of Palaeontology)Currie and et al. UA(1990). (University is FABL fore-aft basal of length.Alberta) are Missing from data Sues is (1978) indicatedand by —.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. oval oval oval 0 8 ■“ 6 too worn to 6 65 0 7 m easure 4 2.4 3.9 — 2.0 5 0 4.5 — 2.1 2.6 7 5.1 8.9 9.2 — 3.1 9 m id-tooth complete tooth nearly complete nearly complete LSUMNS LSUMNS LSUMNS LSUMNS 12339 74.10.5 74.10.5 (2 teeth from type) 489:6234 491:5950 TMP TMP 492:5158 489:5659 86.36.117 TMP 88.121.39 TMP 81.20.259 UA t o ■O*

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. oval oval oval oval oval sectional shape Cross- 5 0 0 oval carinae M axim um denticles/mm on anterior num ber of -11 (v. small) 0 oval -11 (v. small) 0 oval 9 8 9 carinae denticles/mm on posterior M axim um num ber of APPENDIX IV IV APPENDIX 1.8 1.4 8 (v. small) 2.1 5.53.2 6 4 0 3.8““ 5 0 2.2 M axim um FABL (mm) ““ — ““ 3 3.2 (mm) Total length MEASUREMENTS OFRICHARPOESTESIA TEETH -com plete tip -com plete -com plete base tip base base Position of fragment within tooth Measurements of Richardoestesia teeth follow those of Currie et al. (1990). FABL is fore-aft basal length. LSUMNS LSUMNS LSUMNS 140:6140 489:6239 492:6264 LSUMNS LSUMNS LSUMNS LSUMNS 489:6236 489:6238 489:6235 LSUMNS 489:6233 489:6237 Missing data is indicated by Specimen #

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. VITA Julia T. Sankey was bom in Santa Barbara, California, on August 25, 1964. She earned her bachelor of science degree in biology from Albertson College of Idaho (Caldwell) in 1987. She was awarded seven undergraduate grants and scholarships. Her senior thesis is titled, "Mammals from the Sinker Butte Area, Upper Glenns Ferry Formation, Owyhee County, Southwestern Idaho". She worked in the Orma J. Smith Museum of Natural

History at the college from 1983-1987. From 1987-1988, she took geology courses at the University of Arizona (Tucson) and worked in the vertebrate paleontology lab. She was awarded a scholarship from the university to attend geology field camp. From 1988-1991, she attended Northern Arizona University (NAU) and completed a master of science degree in Quaternary Studies in 1991. Her master's thesis is titled, "A Late Blancan-Early Irvingtonian Vertebrate Fauna and Magnetostratigraphy from the Upper Glenns Ferry and Lower

Bruneau Formations, Near Murphy, Southwestern Idaho" (206 pp). Publications from this work include: 5 abstracts (1987-1994), 1 field guide

chapter (1995), and 2 papers (1998). She received grant support for this research from the American Museum of Natural History, Sigma Xi-NAU

chapter, NAU Graduate College, and the U.S. Geological Survey. She worked for the U.S. Geological Survey, Paleomagnetics Lab during her three years in

Flagstaff. From 1991-1994, she worked for paleontological consulting companies, and worked on field projects in California, Idaho, Oregon, and Washington.

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. From 1994-1998 she was a graduate student in the Department of Geology and Geophysics, Louisiana State University (L.S.U.). During this time she was employed by the L.S.U. Museum of Natural History as Collections Manager of the Vertebrate Paleontology Collections. She also helped teach a L.S.U. introductory geology course for gifted freshmen in Colorado during summer, 1997. She was the president of the Baton Rouge chapter of the Association for W omen in Science (1996). Julia was the field trip coordinator for a Department of Geology and Geophysics trip through western Venezuela in 1997, which was subsidized by $7,050 from oil companies, part of which she helped raise. This trip resulted in a field guide

written by the participating students. Her dissertation is titled, "Vertebrate Paleontology and Magnetostratigraphy of the Upper Aguja Formation (Late Campanian), Talley Mountain Area, Big Bend National Park, Texas". This work has resulted in four abstracts (1995-1997), and from it several papers will be submitted. In 1996, she and her advisor, Dr. Judith A. Schiebout, were awarded a $10,827 research grant from the Dinosaur Society for this research. In 1997, she was chosen to participate in the Romer student prize competetion at the Society

of Vertebrate Paleontology annual meeting. While at L.S.U., Julia also

received $2,690 in travel grants from the Department of Geology and Geophysics, Graduate School, Geoscience Associates, Museum of Natural

Science, AAPG-LSU chapter, and the GSA. Julia is a member of the following professional societies: American

Association for the Advancement of Science, American Association of

Petroleum Geologists, Association for Women Geoscientists, Association for

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Women in Science, Geological Society of America, Paleontological Society; Society for Sedimentary Geology, and the Society of Vertebrate Paleontology. Julia will graduate with a the degree of Doctor of Philosophy in

Geology in August, 1998.

251

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. DOCTORAL EXAMINATION AND DISSERTATION REPORT

Candidate: Julia T. Sankey

Major Field: Geology

Title of Dissertation: Vertebrate Paleontology and Magnetostratigraphy of the Upper Aguja Formation (Late Campanian), Talley Mountain Area, Big Bend National Park, Texas

Approved:

Major Profess Chairman

le Graduate School

EXAMINING COMMITTEE:

Date of Examination:

May 12, 1998______

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