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New information on Lethiscus stocki (Tetrapoda, Lepospondyli, Aistopoda) from high-resolution computed tomography and a phylogenetic analysis of Aistopoda

Jason S. Anderson, Robert L. Carroll and Timothy B. Rowe
New information on Lethiscus stocki (Tetrapoda, Lepospondyli, Aistopoda) from high-resolution computed tomography and a phylogenetic analysis of Aistopoda
Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre (August 2003) 40 (8): 1071-1083

Abstract

High-resolution computed tomography provides an alternative to serial sectioning and other destructive techniques of studying fossils (data available at http://www.DigiMorph.org). This technology was used to study the oldest aistopod Lethiscus stocki. The fossil is found to have approximately 30 closely spaced teeth on its maxilla and dentary, a short vomer, a palatine running nearly the entire length of the maxilla that is toothed at least posteriorly, and a choana that is located at the premaxilla-maxilla suture. It has a lower jaw with a high articular facet for the quadrate condyle; a lateral fossa for the adductor musculature, superficially similar to the mammalian masseteric fossa; and a sutural pattern that closely resembles that of Oestocephalus. Previously reported pectoral elements are not evident in the scans and may be best interpreted as fractures on the surface of the nodule associated with sedimentary inclusions. Relationships among all relatively complete aistopods were analyzed using parsimony. Two most parsimonious trees were found, differing in the arrangement of the outgroup taxa. Phlegethontia and Pseudophlegethontia are found to be sister taxa to Coloraderpeton and Oestocephalus, with Ophiderpeton and Lethiscus placed as successively more distant taxa. This topology renders Ophiderpetontidae, as previously conceived, paraphyletic. Lethiscus is confirmed to be the most basal aistopod. A new classification of Aistopoda is presented. This study shows that the palatoquadrate of higher aistopods is derived in-group, which is consistent with the trends in aistopods of peramorphosis in the endochondral skeleton and paedomorphosis in the dermal skeleton.


ISSN: 0008-4077
EISSN: 1480-3313
Coden: CJESAP
Serial Title: Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre
Serial Volume: 40
Serial Issue: 8
Title: New information on Lethiscus stocki (Tetrapoda, Lepospondyli, Aistopoda) from high-resolution computed tomography and a phylogenetic analysis of Aistopoda
Affiliation: Western University of Health Sciences, College of Veterinary Medicine, Pomona, CA, United States
Pages: 1071-1083
Published: 200308
Text Language: English
Summary Language: French
Publisher: National Research Council of Canada, Ottawa, ON, Canada
References: 65
Accession Number: 2004-009831
Categories: Vertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendix
Illustration Description: illus. incl. 1 table
Secondary Affiliation: McGill University, CAN, CanadaUniversity of Texas at Austin, USA, United States
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200403
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