New material from the Upper Devonian (Frasnian) Fram Formation of Ellesmere Island, Nunavut, Canada, represents the second holoptychiid (Porolepiformes) species to be described from the formation. The quality of preservation and preparation of the material enables description of underrepresented anatomy for Holoptychius including the braincase (ethmosphenoid and otico-occipital). The new species of Holoptychius is diagnosed by, a quadrate articulation positioned on the lingual surface of the lower jaw, the presence of a marginal tooth field on all three coronoids, and the presence of a third mandibular sensory canal located dorsal to the infradentary foramina. Traditional use of the name Holoptychius has resulted in an overabundance of species. In recent years, efforts have been made to re-diagnose Holoptychius according to discrete cranial features rather than more widely distributed aspects of scale morphology. The new species is diagnosed as Holoptychius without any scales attributed to it With this new description, the recent Nunavut Paleontological Expeditions continue to expand the Fram Formation's diverse vertebrate fauna, one that additionally includes the elpistostegalian Tiktaalik roseae.
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Vol. 162 • No. 1