New data on the sarcopterygian Koharalepis jarviki (Tetrapodomorpha; Canowindridae) from the Late Devonian of Antarctica, revealed via synchrotron and neutron tomography

Introduction The ‘osteolepiforms’ are an extinct order of lobe-finned fishes that had a cosmopolitan distribution, which are often considered for their proximity to the vertebrate water-to-land transition. The canowindrids are an East Gondwanan clade of tetrapodomorph fishes that exhibit a high level of endemism. However, due to the rarity of canowindrid material and their taphonomy, there is only a single representative preserved wholly in 3D and thus suitable for investigation via modern non-invasive tomography. Methods Here we present an updated description of the holotype of Koharalepis jarviki , a canowindrid collected from the Late Devonian Aztec Siltstone formation in Mt Crean, Antarctica, elucidated via a combination of synchrotron and neutron tomography. Results and discussion New elements of the braincase, palate, mandible and axial skeleton are revealed for the first time, and previously reported anatomy including the dermal skull and position of the orbits are confirmed. A partial braincase and endocast has been reconstructed, enabling rare insight into the neural anatomy of Koharalepis . Phylogenetic analysis confirms Koharalepis as a member of the Canowindridae with Harajicadectes zhumini recovered as sister taxon. The canowindrids occupy a region of the phylogenetic tree with ‘osteolepidid’ taxa and megalichthyids, crownward of rhizodonts but below tristichopterids and elpistostegalids. This work provides greater support for the taxonomic characters and phylogenetic position of the enigmatic canowindrid family, and the 3D preservation of this material has enabled us to infer some behavioural and ecological insight.