Cranial anatomy of the extinct amphisbaenian Rhineura hatcherii (Squamata, Amphisbaenia) based on high-resolution X-ray computed tomography
Article first published online: 17 NOV 2004
Copyright © 2004 Wiley-Liss, Inc.
Journal of Morphology
Volume 264, Issue 1, pages 1–33, April 2005
How to Cite
Kearney, M., Maisano, J. A. and Rowe, T. (2005), Cranial anatomy of the extinct amphisbaenian Rhineura hatcherii (Squamata, Amphisbaenia) based on high-resolution X-ray computed tomography. J. Morphol., 264: 1–33. doi: 10.1002/jmor.10210
- Issue published online: 9 MAR 2005
- Article first published online: 17 NOV 2004
- NSF. Grant Numbers: IIS-9874781, IIS-0208675
- Rhineura hatcherii;
- cranial anatomy;
- computed tomography;
- White River Group;
- worm lizards
The fossilized skull of a small extinct amphisbaenian referable to Rhineura hatcherii Baur is described from high-resolution X-ray computed tomographic (HRXCT) imagery of a well-preserved mature specimen from the Brule Formation of Badlands National Park, South Dakota. Marked density contrast between bones and surrounding matrix and at bone-to-bone sutures enabled the digital disarticulation of individual skull elements. These novel visualizations provide insight into the otherwise inaccessible three-dimensionally complex structure of the bones of the skull and their relationships to one another, and to the internal cavities and passageways that they enclose. This study corrects several previous misidentifications of elements in the rhineurid skull and sheds light on skull construction generally in “shovel-headed” amphisbaenians. The orbitosphenoids in R. hatcherii are paired and entirely enclosed within the braincase by the frontals; this is in contrast to the condition in many extant amphisbaenians, in which a large azygous orbitosphenoid occupies a topologically distinct area of the skull, closing the anterolateral braincase wall. Rhineura hatcherii retains a vestigial jugal and a partially fused squamosal, both of which are absent in many extant species. Sculpturing on the snout of R. hatcherii represents perforating canals conveying sensory innervation; thus, the face of R. hatcherii receives cutaneous innervation to an unprecedented degree. The HRXCT data (available at www.digimorph.org) corroborate and extend previous hypotheses that the mechanical organization of the head in Rhineura is organized to a large degree around its burrowing lifestyle. J. Morphol. © 2004 Wiley-Liss, Inc.