New Mixosaurid Ichthyosaur specimen from the Middle Triassic of SW China: Further evidence for the Diapsid Origin of Ichthyosaurs

Liu, Jun, Aitchison, Jonathan C., Sun, Yuan-Yuan, Zhang, Qi-Yue, Zhou, Chang-Yong and Lv, Tao (2011) New Mixosaurid Ichthyosaur specimen from the Middle Triassic of SW China: Further evidence for the Diapsid Origin of Ichthyosaurs. Journal of Paleontology, 85 1: 32-36. doi:10.1666/09-131.1


Author Liu, Jun
Aitchison, Jonathan C.
Sun, Yuan-Yuan
Zhang, Qi-Yue
Zhou, Chang-Yong
Lv, Tao
Title New Mixosaurid Ichthyosaur specimen from the Middle Triassic of SW China: Further evidence for the Diapsid Origin of Ichthyosaurs
Journal name Journal of Paleontology   Check publisher's open access policy
ISSN 0022-3360
Publication date 2011
Year available 2011
Sub-type Article (original research)
DOI 10.1666/09-131.1
Volume 85
Issue 1
Start page 32
End page 36
Total pages 5
Place of publication New York, NY United States
Publisher Cambridge University Press
Language eng
Formatted abstract
Recent cladistic analyses have all suggested a diapsid origin of ichthyosaurs. However, an intermediate evolutionary stage of the lower temporal region of ichthyosaurian skull between basal diapsids and derived ichthyosaurs has been absent from the fossil record. Here we describe the cranial skeleton of a new mixosaurid ichthyosaur specimen with a well-preserved lower temporal region from the Anisian Guanling Formation of eastern Yunnan. It is characterized by the most primitive lower temporal region within known ichthyosaurs. The primitive characters of the lower temporal region include both external and internal separation between the jugal and the quadratojugal, an anterior process of the quadratojugal, an apparent posteroventral process of the jugal, and a large lower temporal opening surrounded by the jugal, the postorbital, the squamosal, and the quadratojugal. The lower temporal region of this specimen provides the most direct evidence to the diapsid origin of ichthyosaurs. It also suggests that the disappearance of the lower temporal fenestra is caused initially by the reduction of the lower temporal arcade rather than the enlargement of the surrounding bones.
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Geography, Planning and Environmental Management Publications
 
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Created: Wed, 29 Jul 2015, 10:34:16 EST by Helen Smith on behalf of School of Geography, Planning & Env Management