Upside down: 'Cryobatrachus' and the lydekkerinid record from Antarctica

Bryan M. Gee, Peter J. Makovicky, Christian A. Sidor

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Temnospondyl amphibians are common in 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, which we provisionally refer to Lydekkerinidae; this specimen represents the most confident identification of a lydekkerinid from Antarctica to date.

Original languageEnglish (US)
Pages (from-to)658-683
Number of pages26
JournalJournal of Paleontology
Issue number3
StatePublished - May 14 2022
Externally publishedYes

Bibliographical note

Funding Information:
Thanks to M. Norell, R. O'Leary, and C. Mehling for the loan of AMNH FARB 9503 and for granting permission for CT scanning, as well as J. Maisano and M. Colbert for their valiant efforts to scan this cumbersome specimen. Thanks to C. Mehling for assistance with historic collection numbers. Thanks to W. Simpson, A. Stroup, and A. Shinya for the loan of FMNH PR 5020, to M. London for preparation of this specimen, and to M. Rich for photography. Thanks to the editor, H.-D. Sues, and to E. Eltink and one anonymous reviewer for constructive feedback that improved this manuscript. Fieldwork resulting in the recovery of FMNH PR 5020 was supported by NSF ANT-1341304 and ANT-1341645, with additional research and analysis supported by NSF ANT-1947094.

Publisher Copyright:
Copyright © The Author(s), 2021. Published by Cambridge University Press on behalf of The Paleontological Society.


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