| Summary: | An ichthyosaur from the Oxfordian—Kimmeridgian of Melville Island, Northwest Territories, Canada, is redescribed. This specimen was previously referred to as Ophthalmosaurus chrisorum Russell, 1993, but exhibits several features incompatible with this generic assignment. Here, I refer this specimen to a new genus, Arthropterygius, characterized by a basioccipital with an extremely reduced extracondylar area, a foramen for the internal carotid artery located on the posterior surface of the basisphenoid, a humerus with a well-developed distal facet for the articulation of a preaxial accessory element, and a radius and ulna with highly angular proximal surfaces for articulation with the humerus. Arthropterygius can be referred to the Ophthalmosauria based on the presence of a preaxial element anterior to the radius and ulna. This referral is supported by a phylogenetic analysis, in which a sister-group relationship between Arthropterygius and the South American genus Caypullisaurus is recovered. This specimen represents the most complete ichthyosaur from the Canadian Arctic, and has important implications for marine reptile diversity at high latitudes during the Jurassic.
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