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bioRxiv · 10.1101/2024.09.11.612576

Unique dental arrangement in a new species of Groenlandaspis (Placodermi, Arthrodire) from the Middle Devonian of Mount Howitt, Victoria, Australia

Fitzpatrick, A. N.·Clement, A. M.·Long, J. A.
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Abstract

Well-preserved specimens of an undescribed species of arthrodiran placoderm, Groenlandaspis howittensis sp. nov. (Middle Devonian of Victoria, Australia), reveals previously unknown information on the dermal skeleton, body-shape and tooth arcade of the wide-spread genus Groenlandaspis. The new material includes, dual pineal plates, extrascapular plates, and cheek bones cheek bones showing the presence of cutaneous sensory organs. The anterior supragnathal, usually a paired element in arthrodires, is a fused medial bone in G. howittensis sp. nov. It is positioned anterior to the occlusion of the mouth between the lower jaw (infragnathals) and upper jaw (posterior supragnathals) bones, indicating a specialised feeding mechanism and broadening the known diversity of placoderm dental morphologies. G. howittensis sp. nov. differs from all other groenlandaspidids by a less pronounced posterior expansion of the nuchal plate; the shape of the posterior dorsolateral plate and the presence of a short accessory canal on the anterior dorsolateral plate. A new phylogenetic analysis positions Groenlandaspididae in a monophyly with the phlyctaeniid families Arctolepidae and Arctaspdidae, however, the specific intrarelationships of groenlandaspidids remain poorly resolved.

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Fitzpatrick, A. N., Clement, A. M., Long, J. A.. 2024-09-16. Unique dental arrangement in a new species of Groenlandaspis (Placodermi, Arthrodire) from the Middle Devonian of Mount Howitt, Victoria, Australia. https://doi.org/10.1101/2024.09.11.612576

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