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A juvenile specimen of the sauropod dinosaur Alamosaurus sanjuanensis from the Upper Cretaceous of Big Bend National Park, Texas

Published online by Cambridge University Press:  14 July 2015

Thomas M. Lehman  and
Alan B. Coulson
Thomas M. Lehman
Affiliation:
Department of Geosciences, Texas Tech University, Lubbock 79409-1053,
Alan B. Coulson
Affiliation:
Department of Geosciences, Texas Tech University, Lubbock 79409-1053,
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Abstract

A juvenile specimen of the titanosaurid sauropod Alamosaurus sanjuanensis, recovered from just below the Cretaceous/Tertiary boundary horizon in Big Bend National Park, Texas, is from an individual less than half the size of adult specimens referred to this species. The disarticulated skeleton was preserved in deposits of a shallow flood-plain pond and includes elements not previously described, allowing for an improved diagnosis for this species. The elongate opisthocoelous cervical vertebrae have non-bifid posteriorly deflected neural spines with deep postspinal fossae. The dorsal vertebrae have wide spatulate neural spines with strong prespinal laminae, and lack hyposphene-hypantrum articulations. Alamosaurus sanjuanensis exhibits a unique morphology of the ischium, evident even in this juvenile specimen. Comparison with other titanosaurid species suggests that A. sanjuanensis is most closely related to an unnamed titanosaur from Peiropolis, Brazil and Neuquensaurus australis from Argentina.

Type
Research Article
Information
Journal of Paleontology , Volume 76 , Issue 1 , January 2002 , pp. 156 - 172
Copyright
Copyright © The Paleontological Society

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