New Middle Triassic tetrapods from the upper Fremouw Formation of Antarctica and their depositional setting

Abstract

<div><p>ABSTRACT</p><p>Renewed field work in the Beardmore Glacier region of Antarctica has led to a new collection of tetrapod fossils from the upper member of the Fremouw Formation near Fremouw Peak. This locality records a sedimentary environment remarkably similar to that preserved at Gordon Valley, the only other locality known to preserve <i>Cynognathus</i> Assemblage Zone–equivalent taxa from Antarctica. Fossil bones are generally disarticulated and mixed with logs and reworked mudrock clasts, forming an intraformational channel-lag conglomerate. To date, very few bones of small-bodied taxa have been recovered from the upper Fremouw conglomerates, suggesting that they did not survive the reworking process. We use an apomorphy-based approach to record three previously unrecognized taxa from the upper Fremouw Formation: the dicynodont <i>Angonisaurus</i>, an indeterminate therocephalian therapsid, and an indeterminate crown-group archosaur. Combined with previous data, our work demonstrates that 10 distinct taxa can be recognized from the upper Fremouw, including two endemic temnospondyl species. Our recognition of <i>Angonisaurus</i> in the upper Fremouw Formation provides a new piece of evidence in favor of a correlation with the <i>Cynognathus</i> C subzone (uppermost Burgersdorp Formation) of South Africa and the Lifua Member of the Manda beds of Tanzania.</p><p>SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at <a href="http://www.tandfonline.com/UJVP" target="_blank">www.tandfonline.com/UJVP</a></p></div