The Campanian Terlingua Local Fauna, with a Summary of Other Vertebrates from the Aguja Formation, Trans-Pecos Texas Author(s): Timothy Rowe, Richard L. Cifelli, Thomas M. Lehman, Anne Weil Source: Journal of Vertebrate Paleontology, Vol. 12, No. 4 (Dec. 15, 1992), pp. 472-493 Published by: The Society of Vertebrate Paleontology Stable URL: http://www.jstor.org/stable/4523473 Accessed: 12/04/2010 20:53 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. 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S- MNH (approx.)-- -..,58/TMM43057 RattlesnakeMt. sandstone mbr. McKinneySprings tongue of PenFm. o ----lower shale mbr. basal sandstonembr - PEN FORMATION (marine) TEXAS OMNHV58/ TMM 43057 FIGURE 2. Stratigraphicrelationships of the Pen and Aguja formationsthrough Big Bend National Park, includinginformal units designated by Lehman (1985a, 1989). The shaded area of the map, includingthe approximatelocation of the microsite, is BrewsterCounty, Texas. centrate contained abundant residual carbon, the sam- continuous lignite that contains twigs and branches of ples were subsequently separated with the heavy liquid carbonized wood, leaf material, amber, and angio- zinc bromide (e.g., Reynolds, 1983), adjusted to a spe- sperm seeds. The microvertebrate-bearing bed is 13 to cific gravity of between 2.3 and 2.4, prior to picking 18 cm thick, and consists of discontinuous stringers of concentrate under a dissecting microscope. Processing fine (granule to small pebble) conglomerate separated of samples collected in 1988 yielded approximately 17 by thin lenses of fine sandstone and clayey siltstone. mammal specimens per 100 kg of original rock matrix, The conglomerate stringers are the principal source of a high level of productivity by Cretaceous standards. the microvertebrate fossils. Clasts in the conglomerate range up to 2 cm in diameter, although most are less than 1 cm. The clasts THE TERLINGUA LOCAL FAUNA LOCALITY comprise clay balls, wood, coal, amber, coprolites, and abundant, disarticulated mi- The microvertebrate locality (OMNH V58; TMM crovertebrate bones and teeth. The site also produces 43057) lies approximately 8 km NNE of Study Butte, isolated larger bones, most notably isolated limb ele- Brewster County, Texas (Figs. 1, 2). Detailed locality ments and vertebrae of a hadrosaur, and shell frag- information is on file at the Oklahoma Museum of ments of a huge trionychid turtle. Many bones in all Natural History and the Vertebrate Paleontology and size classes are broken. Some bones exhibit varying Radiocarbon Laboratory of the University of Texas. degrees of abrasion and rounded edges indicative of The locality is stratigraphically within the lower part transport before burial. Branches of carbonized wood of the upper shale member of the Aguja Formation, lacking preferred orientation are common at the top within several meters of the top of the underlying ma- of the bone-producing horizon. Most of this wood con- rine Terlingua Creek sandstone member (Fig. 2). The tains mud filled Teredolites (shipworm) borings. bone-producing bed rests upon a distinctive, laterally The bone-bearing deposit ranges up to 10 m wide, ROWE ET AL.- VERTEBRATES OF THE CRETACEOUS AGUJA FORMATION 475 and represents deposition in a shallow channel with a Slaughter (1972), only some of the Aguja archosaurs sluggish current. Downcutting into the underlying lig- were subsequently described (Coombs, 1978; Davies, nite was not observed at the locality itself, but it does 1983; Lehman, 1982, 1985a, 1989). Much of the work occur in similar, adjacent deposits at the same strati- carried out by Louisiana State University in the Aguja graphic level. Overlying the channel are overbank de- Formation was summarized in a dissertation (Stand- posits of clay-rich siltstone, typical of Lehman's (1985a) hardt, 1986), but apart from a faunal summary tabu- coastal floodplain facies. lated by Standhardt (in Langston et al., 1989), none of Both the geology and faunal composition (see below) this work is published. indicate a predominantly terrestrial source for the sed- iment and fossils at the site. there preserved However, THE TERLINGUA LOCAL FAUNA is also evidence of significant marine influence on the faunal composition, which is not surprising given the Below is a list of taxa comprising the Terlingua local stratigraphic proximity of marine sediments. Teredoli- fauna, and a brief discussion of its major components. tes indicates a brackish or saline environment, and We adopted a conservative approach in taxon iden- relatively direct communication to an open marine tification, taking names only to the levels permitted by environment. There are eight sharks in the fauna (see material recovered from this locality. For example, below) that further support this interpretation, in that although isolated ceratopsian teeth recovered from the all eight taxa have also been recovered from marine locality probably represent Chasmosaurus mariscalen- sediments. Lepisosteids and amiids, also well repre- sis, named from material collected elsewhere in the sented in the fauna, are primarily freshwater taxa al- Aguja (Lehman, 1982, 1989, 1990a), we prefer to as- though both have high salinity tolerances and are con- sign them to Ceratopsidae until more specifically diag- sistent with an estuarine environment (Hoese and nostic material is identified in collections from the site. Moore, 1977; Bryant, 1987). We also note that many identifications are based more on phenetic resemblances than on the presence of de- monstrable because VERTEBRATE COLLECTIONS FROM THE synapomorphies, phylogenetic at levels are not available for most AGUJA FORMATION analyses alpha yet of the taxa at issue. Thus, many of the names used Significant collections from the Aguja Formation below could be thought of as "form taxa" rather than were first made between 1938 and 1940 under the monophyletic entities. The major exception to this is direction of William Strain (University of Texas at El in our discussion of the squamates, which benefits from Paso), who directed a Works Progress Administration the phylogenetic hypotheses developed by Estes paleontological project in west Texas. At nearly the (1983b), Estes et al. (1988), Gauthier (1982) and Gau- same time, collections were made by Barnum Brown thier et al. (1988). Taxa marked with an asterisk (*) for the American Museum of Natural History, and by represent first occurrences for the Aguja Formation. William McAnulty, Donald Savage, and Wann Lang- Voucher specimens are listed in Appendix 1 for all ston, Jr., for the University of Oklahoma (for details taxa discussed below. see Lehman, 1985a, 1989; Langston et al., 1989; Da- vies and Lehman, 1989). From the 1960s through the CHONDRICHTHYES 1980s, Dr. Langston assembled a large collection of Euselachii Aguja vertebrates for the Vertebrate Paleontology Lab- Hybodontoidea oratory of the University of Texas, an effort carried on Hybodontidae by some of his students (e.g., Davies, 1983; Lehman, *Hybodus sp. 1982, 1985a, 1989). Most of this work focused on the Hybodontidae, indet. megafauna, but a recent collaborative effort by the Uni- Polyacrodontidae versity of Oklahoma and University of Texas collected Lissodus (=Lonchidion) selachos a large sample of Aguja microvertebrates that signifi- Lamniformes cantly increased the documented diversity of Aguja Mitsukurinidae vertebrates (Cifelli and Rowe, 1990). Judith Schiebout Scapanorhynchys sp. and Barbara Standhardt of Louisiana State University Batomorphii made additional microvertebrate collections in the Rajiformes 1970s and early 1980s. The net result of these 50 years Sclerorhynchidae of collecting in the Aguja is more than 1,000 cataloged Onchopristis dunklei specimens representing roughly 70 vertebrate species. *Ischyrhiza avonicola Although Aguja vertebrates have been known for Rajiformes incertae sedis more than half a century, few Aguja taxa have received Squatirhina americana comprehensive treatment in the literature. The first Ptychotrygon sp. descriptions of these materials were by Brown (1942), Batomorphii indet. followed by Colbert and Bird (1954) on the giant croc- Myliobatiformes odilian Deinosuchus