A new onychodontid (Osteichthyes, Sarcopterygii) from the Upper Devonian (Frasnian) of Devon Island, Nunavut Territory, Canada

Abstract

We describe a new onychodontid, Onychodus mikijuk, from the Upper Devonian (Frasnian) Nordstrand Point Formation of the Grinnell Peninsula, Devon Island, Nunavut Territory, Canada, represented by tooth whorls, partial lower jaws, and a partial premaxilla. Among the species of Onychodus, O. mikijuk is distinguished by macroscopic raised longitudinal enamel ridges along the parasymphyseal teeth, a symphyseal plate that is taller than it is long with a raised posterior corner, and a weakly expanded contact between the lingual dentary flange and symphyseal plate. The lateral denticles of the parasymphyseal tooth whorl are inclined against the parasymphyseal teeth, as in adult Onychodus jandemarrai, which may indicate that, at least the largest specimens of this new species, were small adults rather than juveniles. This new species is the first record of an onychodontid from the Upper Devonian of the Canadian Arctic, the first from a riverine environment, and one of the youngest occurrences of the clade.