Extremidades estruturais em um dinossauro do Cretáceo

quarta-feira, fevereiro 10, 2010

Structural Extremes in a Cretaceous Dinosaur

Paul C. Sereno1*, Jeffrey A. Wilson2, Lawrence M. Witmer3,John A. Whitlock2, Abdoulaye Maga4, Oumarou Ide4,Timothy A. Rowe5

1 Department of Organismal Biology and Anatomy, University of Chicago, Chicago, Illinois, United States of America, 2 Museum of Paleontology and Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan, United States of America, 3 Department of Biomedical Sciences, College of Osteopathic Medicine, Ohio University, Athens, Ohio, United States of America, 4 Institute for Human Science, University of Niamey, Niamey, Republic of Niger, 5 Jackson School of Geological Sciences, The University of Texas at Austin, Austin, Texas, United States of America

Abstract

Fossils of the Early Cretaceous dinosaur, Nigersaurus taqueti, document for the first time the cranial anatomy of a rebbachisaurid sauropod. Its extreme adaptations for herbivory at ground-level challenge current hypotheses regarding feeding function and feeding strategy among diplodocoids, the larger clade of sauropods that includes Nigersaurus. We used high resolution computed tomography, stereolithography, and standard molding and casting techniques to reassemble the extremely fragile skull. Computed tomography also allowed us to render the first endocast for a sauropod preserving portions of the olfactory bulbs, cerebrum and inner ear, the latter permitting us to establish habitual head posture. To elucidate evidence of tooth wear and tooth replacement rate, we used photographic-casting techniques and crown thin sections, respectively. To reconstruct its 9-meter postcranial skeleton, we combined and size-adjusted multiple partial skeletons. Finally, we used maximum parsimony algorithms on character data to obtain the best estimate of phylogenetic relationships among diplodocoid sauropods. Nigersaurus taqueti shows extreme adaptations for a dinosaurian herbivore including a skull of extremely light construction, tooth batteries located at the distal end of the jaws, tooth replacement as fast as one per month, an expanded muzzle that faces directly toward the ground, and hollow presacral vertebral centra with more air sac space than bone by volume. A cranial endocast provides the first reasonably complete view of a sauropod brain including its small olfactory bulbs and cerebrum. Skeletal and dental evidence suggests that Nigersaurus was a ground-level herbivore that gathered and sliced relatively soft vegetation, the culmination of a low-browsing feeding strategy first established among diplodocoids during the Jurassic.

Citation: Sereno PC, Wilson JA, Witmer LM, Whitlock JA, Maga A, et al. (2007) Structural Extremes in a Cretaceous Dinosaur. PLoS ONE 2(11): e1230. doi:10.1371/journal.pone.0001230

Academic Editor: Tom Kemp, University of Oxford, United Kingdom

Received: November 2, 2007; Accepted: November 7, 2007; Published: November 21, 2007

Copyright: © 2007 Sereno et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: Supported by the David and Lucile Packard Foundation, National Geographic Society, Island Fund, and Women's Board of the University of Chicago (to PCS); National Science Foundation (IOB-0343744, IOB-0517257) and the Ohio University College of Osteopathic Medicine (to LMW); Scott Turner Award of the University of Michigan and Geological Society of America (8689-07) (to JAW-2).

Competing interests: The authors have declared that no competing interests exist.

* To whom correspondence should be addressed. E-mail: dinosaur@uchicago.edu

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