Tetrapod burrows from the Triassic of Antarctica

Abstract

ABSTRACT Two new tetrapod trace fossil records from the Triassic of Antarctica are described. The first is a giant terminal chamber collected from the lower Fremouw Formation (Lower Triassic) at Wahl Glacier (Beardmore Glacier region, central Transantarctic Mountains). Comparison to South African burrows known to contain the cynodont Thrinaxodon liorhinus, suggests that the Antarctic fossil was created by a tetrapod of similar size. The second set of tetrapod burrow casts was collected from Member ‘A’ of the Lashly Formation (lower Middle Triassic) and, if correctly interpreted, represent the first evidence of tetrapods from the Middle Triassic of Victoria Land. Our findings demonstrate that tetrapods were present in Victoria Land during the Middle Triassic, despite not being recovered as body fossils until the Upper Triassic in that region. Comparison to morphologically similar South African trace fossils suggests that procolophonids might have produced the Antarctic burrows, but this attribution is necessarily speculative because burrow inhabitants have not been found in situ and no morphological feature uniquely ties procolophonids to this type of trace fossil. We propose that underground burrows and dens were important shelters for Antarctic terrestrial vertebrates during the Triassic, despite a relatively moderate climate.