Vol. 29, Supplement to No. 3

Vol. 29, Supplement to No. 3, September 2009

University of Bristol Volume 29, Supplement to Number 3 September 2009 DETAIL MAP Program and Abstracts Avon Gorge Hotel Bristol/Pr B3129 A369 , via the Suspension Bridge Bu rwa Clifton Goldne Clifton Hill House T Bristol A38, A4 , aunton , lls M5

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Society of Vertebrate Paleontology ISSN 0272-4634 Poster Session III, (Friday) of isolated tridactyl footprints (and of both bipedal and quadrupedal trackways). However, LATE MICROVERTEBRATE FAUNA FROM THE NORTHERN most footprint shapes and shape variability have been treated descriptively so far, and no STATE OF COAHUILA, MEXICO study has yet tried to exploit the potentials of quantitative characterizations, in particular, MONTELLANO, Marisol, Instituto de Geologia, UNAM, Mexico, Mexico; MONROY, using geometric morphometrics (GM), which are perfectly suited for this particular. Using Heidi, Facultad de Estudios Superiores, Iztacala, Mexico, Mexico; HERNÁNDEZ-RIVERA, GM, we pursue to explore and visualize for the first time the variation of the ornithopod René, Instituto de Geologia, Mexico City, Mexico; TORRES, Esperanza, Posgrado Ciencias track record from Cameros Basin, as well as to disentangle the possible presence of two Biológicas, UNAM, Mexico City, Mexico distinct ornithopod footprint morphotypes. A sample of 43 well-preserved ornithopod Cameros tracks was implemented for comparison with other specimens from the world’s In Mexico, the microvertebrate faunas are poorly known. For several fossil record. The footprints were digitalized from field schemes and pictures, and thereafter years field work had been carried on in the northwestern corner of the State of Coahuila, a configuration of landmarks and semilandmarks where used to capture the geometry and where outcrops of the Aguja Formation are present. Previous paleomagnetic studies showed the outline of the footprints. On the one hand, a principal components analysis allows a normal polarity which correlates to the chron C33.1n and corresponds to the upper visualizing that, 1) digit width, the relatively footprint elongation, and the location of both Campanian. Sediments had been collected and screen washed for microfossils, which are hypex, and 2) the relatively footprint width related to digital angulation, both account for not very abundant. The recovered taxa include the chondricthyes Lonchidion selachos, more than 50% of the sample variability. On the other hand, multivariate regressions reveal Squalicorax sp., the rays Myledaphus bipartitus, Myledaphus sp., and Ptychotrygon sp., that footprint shape is statistically correlated with size, in such a way that larger footprints the osteichthyes Lepisosteus sp., and an indetermined phyllodontid form. This assemblage tend to be broader whereas smaller tend to be more slender. This result suggests that the of aquatic forms indicate brackish to freshwater environment, like an estuarine. Also the long-time observed morphotypes are possibly contained within an allometric continuum, crocodiles Goniopholis sp., Brachychampsa sp, and the giant Deinosuchus riograndesis and therefore, that they may have important implications in dinosaur foot morphology and/ are present; the dinosaurs are represented by the small theropods: cf. Troodon, three forms or biomechanics. of the genus Saurornitholestes, S. langstoni, S. n. sp. A? and S. n. sp. C., remains of other theropods: a form of an indetermined tyrannosaurid and teeth of kritosaurinae hadrosaur were also identified. Unusually, Richardoestesia is missing, this taxa had been reported as Poster Session I, (Wednesday) abundant in the Campanian southern faunas. The diversity recognized until now is poor BITE FORCE IN MEGALANIA compared to that reported from the fauna of the Big Bend National Park, Texas, remains of MORENO, Karen, UNSW, Paris, France; PINO, Andrea, PUC, Valparaiso, Chile; WROE, amphibians, lizards and mammals had not yet been recovered. The remains of osteichthyes Steven, UNSW, Sydney, Australia; MCHENRY, Colin, U of Newcastle, Newcastle, Australia are the most abundant, follow by those of crocodile, theropods and chondrichthyes. This relative abundance of taxa is similar to that present in the southern faunas such as in the We performed 3D finite element analyses of the skulls ofVaranus komodoensis and V. Big Bend National Park, Texas; compared to the northern faunas (p.e., Two Medicine Fm., giganteus, two of the largest modern varanids. The results show that their bite force is Dinosaur Provincial Park) where the theropod material is much more abundant. So far, proportional to the square of the linear dimensions, despite distinct bone stress distributions this fauna shares most of the genera and species of microvertebrates with the Campanian and feeding behaviors (“hold-and-pull” vs. “puncture-crushing”). We find however, that the southern faunas, supporting the hypothesis of the faunal latitudinal gradient proposed by horizontal component of the bite force is greater in V. komodoensis. This is due to specific previous authors. features in its skull architecture, which are almost certainly related to a distinct feeding behavior. Here, we use morphology and performance data obtained on V. komodoensis and V. giganteus to constrain the feeding behavior of an extinct varanid, Megalania prisca, for Technical Session IX, Thursday 2:30 which remains are too incomplete to build an accurate model of its skull. We find that the INSIGHTS INTO THE PRESERVATIONAL PATTERNS OF VERTEBRATE feeding behavior of M. prisca seems to resemble that of V. giganteus. Furthermore, the bite FOSSILS IN A FLUVIAL SYSTEM USING A TWO-DIMENSIONAL COMPUTER force of M. prisca is estimated to have been under 200N, an extremely low value for an MODEL animal this mass. Indeed, M. prisca is the largest terrestrial varanid known (5 meters) and MOORE, Jason, Texas A&M University, College Station, TX, USA allegedly a top predator in Australian Pleistocene. As the prey of Megalania were potentially large, its feeding behavior is unlikely to have been based solely on bite strength. The three-dimensional distribution of vertebrate fossils preserved in a lithological sequence can vary greatly from formation to formation. Some rock units show preferential preservation in channel lag or fill deposits, others in lacustrine or distal floodplain Poster Session III, (Friday) environments. In addition, the taphonomic characteristics of fossil assemblages (for example A HIGH-DIVERSITY EGGSHELL LOCALITY FROM THE - the size-frequency distribution of elements or the degree of modification by weathering BARREMIAN TRANSITION OF THE IBERIAN PENINSULA and abrasion) can also vary greatly. An understanding of the processes controlling these MORENO-AZANZA, Miguel, Grupo Aragosaurus. Universidad de Zaragoza, Zaragoza, variations is necessary to accurately assess the information lost from fossil assemblages, Spain; GASCA, José Manuel, Grupo Aragosaurus. Universidad de Zaragoza, Zaragoza, to determine when it is possible to validly compare assemblages and potentially to enable Spain; CANUDO, José Ignacio, Grupo Aragosaurus. Universidad de Zaragoza, Zaragoza, prediction of the fossiliferousness of unstudied units. To investigate the patterns of Spain preservation in fluvial systems, I have created a two-dimensional model of an aggrading floodplain with a meandering channel, inhabited by a steady-state vertebrate community. La Cantalera site is located near the village of Josa (Iberian Range, Teruel, Spain). La During each time-step of the model, a proportion of the individuals in the community Cantalera site is an outcrop of Early Cretaceous clays from the Blesa Formation. The die, disarticulate and are transported across the floodplain. As the river migrates and fossiliferous beds are grey clays with abundant vegetal remains, charophytes, ostracods, the floodplain aggrades, the remains of these individuals become buried.The elements gastropods and vertebrate remains. The site was formed in a restricted palustrine are subject to degradation based on their individual physical properties whilst in the environment with periodic droughts. The charophyte assemblage dates the site as late taphonomically active zone, but are considered preserved once they are buried below this Hauterivian-early Barremian in age. level. By altering the parameters of the model, the influence of different properties on the distribution of fossils in a rock unit can be investigated. Altering the rate, severity or style The highly diverse vertebrate fossils comprise isolated teeth, disarticulated complete or of river flooding significantly influences the distance over which elements are transported. fragmented bones, eggshell fragments and coprolites. Up to 29 different vertebrate taxa The balance of floodplain aggradation and river erosion is one control on the distribution of have provided recognizable skeletal remains. Dinosaurs are the most diverse vertebrates, skeletal elements between channel and more distal floodplain facies. Models run without any with 16 taxa identified, including theropods, sauropods, thyreophorans and ornithopods. element destruction in the taphonomically active zone provide some suggestions as to the Other archosaurs are represented by four crocodylians and two pterosaurs. One turtle, two magnitude of loss of elements that must occur in even the most fossiliferous of vertebrate amphibians, one lacertid and three mammals make up the vertebrate assemblage. The most assemblages. The results of this model provide a “null model” against which fossil abundant remains are shed teeth of ornithopod dinosaurs, crocodylian teeth and theropod teeth. distributions in the geological record can be compared. Several thousand eggshell fragments have been recovered through the washing and sifting of three tons of sediment. At least eight different ootaxa have been recognized, including the oofamilies Elongaloolithidae, , Spheroolithidae?, Krokoolithidae and Technical Session X, Friday 11:30 Testudoolithidae. Most of the eggshell fragments belong to the Elongaloolithidae oofamily, ASSESSING DINOSAUR ICHNO-VARIABILITY WITH GEOMETRIC and most of them can be referred to the oospecies turolensis. Prismatoolithidae MORPHOMETRICS. THE ORNITHOPOD TRACKS FROM THE CAMEROS eggshells include sp. and a new highly sculptured form in the process of BASIN (LOWER CRETACEOUS, SPAIN) AS A CASE STUDY being described. Krokoolithidae eggshells are provisionally identified asKrokoolithes sp. MORATALLA, José Joaquín, Instituto Geologico y Minero de España, Madrid, AL, Spain; Noticeable is the presence of two different aff. Testudoolithus species, by contrast with MARUGÁN-LOBÓN, Jesús, Universidad Autónoma de Madrid, Madrid, AL, Spain the low number of turtle bone remains preserved. Also, the number of cf. Spheroolithidae eggshell fragments, commonly related to ornithopod dinosaurs, is unexpectedly low despite The Cameros Basin constitutes a sedimentary area especially well-known by its dinosaur the huge number of ornithopod teeth recovered. Due to its high diversity, La Cantalera tracksites. It represents a geographically large area (about 8000 km2) that encompasses an proves to be a key locality in the study of European Lower Cretaceous ootaxa. enormous time span, ranging from the Upper (Tithonian) to the Lower Cretaceous (Aptian). The Cameros dinosaur ichnocenosis is markedly dominated by theropods (about 86%), followed by ornithopods (about 11%), and lastly, by sauropods (3%), and consists

JVP 29(3) September 2009—ABSTRACTS 151A