THE BRAINCASE OF YOUNGINA CAPENSIS (REPTILIA, DIAPSIDA):
NEW INSIGHTS FROM HIGH-RESOLUTION CT SCANNING OF THE HOLOTYPE

Nicholas M. Gardner, Casey M. Holliday, and F. Robin O'Keefe

ABSTRACT

Detailed descriptions of braincase anatomy in early diapsid reptiles have been historically rare given the difficulty of accessing this deep portion of the skull, because of poor preservation of the fossils or the inability to remove the surrounding skull roof. Previous descriptions of the braincase of Youngina capensis, a derived stem-diapsid reptile from the Late Permian (250 MYA) of South Africa, have relied on only partially preserved fossils. High resolution X-ray computed tomography (HRXCT) scanning, a new advance in biomedical sciences, has allowed us to examine the reasonably complete braincase of the holotype specimen of Youngina capensis for the first time by digitally peering through the sandstone matrix that filled the skull postmortem. We present the first detailed 3D visualizations of the braincase and the vestibular system in a Permian diapsid reptile. This new anatomical description is of great comparative and phylogenetic relevance to the study of the structure, function and evolution of the reptilian head.

Nicholas M. Gardner. Department of Biological Sciences, Marshall University, Huntington, West Virginia. 
Casey M. Holliday. Department of Pathology & Anatomical Sciences, University of Missouri, Columbia, Missouri.
F. Robin O'Keefe. Department of Biological Sciences, Marshall University, Huntington, West Virginia.

KEY WORDS: Youngina capensis, diapsid reptiles, CT scanning, 3D models

PE Article Number: 13.3.19A
Copyright: Society for Vertebrate Paleontology November 2010
Submission: 14 September 2009. Acceptance: 8 September 2010

NOTE IN PROOF:

Reisz et al. (2010) find a non-diapsid position for Apsisaurus as a varanopid synapsid, but unfortunately, their paper came too late for us to correct Figure 1 by removing it from our tree. We are aware that our placement in the tree for Apsisaurus is outdated, this is the  unfortunate nature of shifting topologies as new data are incorporated. However, our tree was taken from Müller (2003) who noted that the exclusion of Apsisaurus from his data set does not affect the rest of the tree topology in the final analysis.