Phylogenetic data for: Upside down: ‘Cryobatrachus’ and the lydekkerinid record from Antarctica

Temnospondyl amphibians are a common component of non-marine Triassic
assemblages, including in the Fremouw Formation (Lower to Middle Triassic)
of Antarctica. Temnospondyls were among the first tetrapods to be
collected from Antarctica, but their record from the lower Fremouw
Formation has long been tenuous. One taxon, ‘Austrobrachyops jenseni,’ is
represented by a type specimen comprising only a partial pterygoid, which
is now thought to belong to a dicynodont. A second taxon, ‘Cryobatrachus
kitchingi,’ is represented by a type specimen comprising a nearly complete
skull, but the specimen is only exposed ventrally, and uncertainty over
its ontogenetic maturity and some aspects of its anatomy has led it to be
designated as a nomen dubium by previous workers. Here we redescribe the
holotype of ‘C. kitchingi,’ an undertaking that is augmented by
tomographic analysis. Most of the original interpretations and
reconstructions cannot be substantiated, and some are clearly erroneous.
Although originally classified as a lydekkerinid, the purported
lydekkerinid characteristics are shown to be unfounded or no longer
diagnostic for the family. We instead identify numerous features shared
with highly immature capitosaurs, a large-bodied clade documented in the
upper Fremouw Formation of Antarctica and elsewhere in the Lower Triassic.
Additionally, we describe a newly collected partial skull from the lower
Fremouw Formation that represents a relatively mature, small-bodied
individual and that we provisionally refer to Lydekkerinidae; this
specimen represents the most confident identification of a lydekkerinid
from Antarctica to date.