New information on the stem tetrapod group Canowindridae, based on synchrotron studies of Koharolepis from the Middle Devonian of Antarctica

John Long, Alice Clement, Benedict King, Chen Wei Choo

Research output: Contribution to conferencePaper

Abstract

The evolution from water to land represents one of the greatest vertebrate evolutionary transitions, and much of our knowledge comes form study of the tetrapodomorph fishes (Osteichthyes: Sarcopterygii) which form the stem to the Tetrapoda.. Debate continues around the timing of this evolutionary step, and also whether the stem tetrapods first emerged in either the Northern or Southern Hemisphere, with the currently oldest representatives of the lineage found in China (Lu et al. 2012). Within various phylogenies the Canowindridae (comprising Canowindra, Beelarongia and Koharolepis) emerge as clade of basal stem tetrapods just crownward of rhizodontids and basal Chinese forms like Tungsenia and Kenichthys. They are characterised by having broad, flat skulls with triangular wide extratemoporal bones, lacking clear sutures between certain postparietal dermal bones, very small eyes, and some bear expanded cheek plates with additional postorbital bones. With the aid of the Australian synchrotron we herein present new imagining data using Mimics and Drishti on a key Gondwanan taxa, Koharalepis jarviki Young, Long & Ritchie1992 from the Middle Devonian Aztec Siltstone of Antarctica. The new CT data shows the presence of the braincase and articulated hyomandibula, some of the gill-arches and elucidates aspects of the lower jaw morphology. A new canowidridoid which we are currently describing from the Harajicca Sandstone, Northern Territory (see abstract by Choo et al, this volume), also shows details of parasphenoid and palate anatomy. All these data combine to build a clearer concept of the anatomy and functional morphology of the canowindrids, which appear to occupy a niche similar to glyptolepid porolepiforms in most East Gondwana Middle-Late Devonian faunas.
Original languageEnglish
DOIs
Publication statusPublished - 2017
Event14th International Symposium on Early and Lower Vertebrates -
Duration: 3 Jul 2017 → …

Conference

Conference14th International Symposium on Early and Lower Vertebrates
Period3/07/17 → …

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