Abstract

We describe the skull roof anatomy of PRPRC 2007.08.81, a new specimen of late Olenekian (Spathian) ichthyopterygian from the Vega-Phroso Siltstone Member of the Sulphur Mountain Formation of British Columbia, Canada. Based on the presence of a well-developed anterolateral prefrontal process, parietal that is deeply excavated along its posteromedial margin, and skull roof sutural patterns, PRPRC 2007.08.81 closely resembles other Olenekian forms such as Utatsusaurus, Grippia, Chaohusaurus, and Gulosaurus (a new taxon recently described from British Columbia, Canada). However, due to their shared apomorphic supratemporal terrace morphology, PRPRC 2007.08.81 is identified as Utatsusaurus sp. With the only other known conclusive Utatsusaurus material retrieved from the Osawa Formation (Lower Triassic) of Japan, the broad palaeogeographic distribution of this taxon suggests a radiation event for Ichthyopterygia occurring prior to the latter part of the Olenekian. However, despite this inference, the palaeogeographic origin of Ichthyopterygia continues to be unclear; only the acquisition and interpretation of additional chronologically early ichthyopterygian material will resolve the early evolutionary history of this group.

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