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Keywords:

  • Anchisaurus;
  • Ammosaurus;
  • sauropodomorph;
  • Newark Supergroup;
  • Connecticut;
  • Massachusetts

Abstract:  The taxonomic status of the sauropodomorph dinosaurs from the Newark Supergroup of north-eastern USA is reviewed. The inclusion of the three articulated skeletons from Wolcott’s Quarry, Manchester, Connecticut in a single species is supported. Despite claims to the contrary the Manchester skeletons can be referred to the species Anchisaurus polyzelus, which is based on a fragmentary specimen from Massachusetts. Two autapomorphies: dorsoventrally flattened ischial blades set at a low angle to each other and slender sacral ribs of the first sacral vertebra, link the holotype of A. polyzelus to the Manchester specimens. A revised diagnosis of the species and new skull reconstruction are presented. Recent anatomical observations of A. polyzelus indicate that several character states used to assess its phylogenetic position require revision. However, these are not sufficient to overturn previous cladistic analyses. A revised cladistic analysis continues to find support for Anchisaurus as a relatively derived basal sauropodomorph that lies outside of the clade Melanorosaurus + Sauropoda but is more closely related to it than to ‘core prosauropods’ such as Plateosaurus and Massospondylus.