An unrevealed lineage of platypterygiines (Ichthyosauria) with peculiar forefin structure and semiglobal distribution in the mid-Cretaceous (Albian–Cenomanian)

Recent progress in the study of Cretaceous ichthyosaurians resulted in significant reevaluation of their diversity. However, there are still problematic mid-Cretaceous ichthyosaurian taxa, among which are ‘Ophthalmosaurus’ cantabrigiensis Lydekker, 1888 from the upper Albian – lower Cenomanian of England, Maiaspondylus lindoei Maxwell and Caldwell, 2006a from the Albian of Canada and ‘Platypterygius’ ochevi Arkhangelsky, 2008 from the Albian–Cenomanian of European Russia. The listed taxa have a peculiar morphology of the humerus with three distal facets of subequal sizes. Despite their similarity and nearly contemporaneous occurrence, these taxa were never compared to each other. Here we reevaluate their type materials and reveal the evidence for their close relation. We refer these taxa to the genus Maiaspondylus Maxwell and Caldwell, 2006a, recognizing two species – Maiaspondylus lindoei and Maiaspondylus cantabrigiensis comb. nov., whereas ‘Platypterygius’ ochevi is considered a junior subjective synonym of the later. Our phylogenetic analysis places these taxa within derived platypterygiines, further supporting the existence of a previously unrevealed lineage of modest-sized platypterygiine ichthyosaurians with global distribution in the Northern Hemisphere during the Albian–Cenomanian time interval.