Questioning hagfish affinities of the enigmatic Devonian vertebrate Palaeospondylus.

Author(s): Zerina Johanson, Moya Meredith Smith, Sophie Sanchez, Tim Senden, Kate Trinajstic, Cathrin Pfaff
Abstract: Palaeospondylus gunni Traquair, 1890 is an enigmatic Devonian vertebrate whose taxonomic afﬁnities have been debated since it was ﬁrst described. Most recently, Palaeospondylus has been identiﬁed as a stem-group hagﬁsh (Myxinoidea). However, one character questioning this assignment is the presence of three semicircular canals in the otic region of the cartilaginous skull, a feature of jawed vertebrates. Additionally, new tomographic data reveal that the following characters of crown-group gnathostomes (chondrichthyans + osteichthyans) are present in Palaeospondylus: a longer telencephalic region of the braincase, separation of otic and occipital regions by the otico-occipital ﬁssure, and vertebral centra. As well, a precerebral fontanelle and postorbital articulation of the palatoquadrate are characteristic of certain chondrichthyans. Similarities in the structure of the postorbital process to taxa such as Pucapampella, and possible presence of the ventral cranial ﬁssure, both support a resolution of Pa. gunni as a stem chondrichthyan. The internally mineralized cartilaginous skeleton in Palaeospondylus may represent a stage in the loss of bone characteristic of the Chondrichthyes.
Organisation(s): Department of Palaeontology, Department of Evolutionary Biology
External organisation(s): Natural History Museum London, Uppsala University, European Synchrotron Radiation Facility ESRF, Australian National University, Curtin University, King's College London
Journal: The Royal Society Open Science
No. of pages: 8
DOI: https://doi.org/10.1098/rsos.170214
Publication date: 2017
Peer reviewed: Yes
Austrian Fields of Science 2012: 105118 Palaeontology
Keywords
ASJC Scopus subject areas: General
Portal url: https://ucrisportal.univie.ac.at/en/publications/fe0707dd-cac7-4e88-b1e5-64b9256259a2

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