Original paper
A model for the origin of ichthyosaurs
Tarsitano, S.
Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen Band 164 Heft 1-2 (1982), p. 143 - 145
6 references
published: Dec 22, 1982
DOI: 10.1127/njgpa/164/1982/143
ArtNo. ESP155016401032, Price: 29.00 €
Abstract
Through the examination of a mostly uncrushed ichthyosaur, Leptopterygius acutirostris (Geologisches Institut Tübingen, Cat. No. 1576), the skull morphology of ichthyosaurs can now be understood. By viewing the ichthyosaur skull as the culmination of processes centering on the enlargement and posterior migration of the eye and the evolution of the jaw adductor system, the changes in and the origin of the ichthyosaur skull can perhaps be illuminated. This study advocates that ichthyosaurs are derived from a diapsid reptile lineage. According to ROMER (1956, 1968), the origin of the ichthyosaurs is a mystery. ROMER (1968) believed that ichthyosaurs were a branch of cotylosaurs. VON HUENE (1922) thought that ichthyosaurs originated from mesosaurs. KUHN-SCHNYDER (1963) derived ichthyosaurs directly from amphibians. All of the above studies relied on primitive characters in order to establish relationship. Thus, the validity of these studies can not be tested. The present study attempts to find derived features which are part of known functional complexes found in ichthyosaurs and some other amniote taxon.
Keywords
skull morphology • jaw adductor system • diapsid reptiles • cotylosaurs • lizards • squamosal