COROSAURUS ALCOVENSIS CASE AND THE PHYLOGENETIC INTERRELATIONSHIPS OFTRIASSIC STEM-GROUP SAUROPTERYGIA

The holotype and other material of Corosaurus alcovensis Case from the Alcova Limestone of Gasper, Wyoming, was further prepared using a com bination of chemical techniques. anatomical revision resulted in the d efinition of new characters for the analysis of the phylogenetic inter relationships of Triassic stem-group Sauropterygia that document parap hyly of the Eusauropterygia. Corosaurus is the sister-taxon to a clade comprising Cymatosaurus, Pistosaurus, and by extension, plesiosaurs a nd pliosaurs. (C) 1998 The Linnean Society of London.