First record of Ichthyosaurus anningae outside the United Kingdom: New evidence from the Lower Jurassic of northern Spain

Abstract

A new specimen of Ichthyosaurus anningae from Asturias (Northern Spain) is described in detail, representing the first unambiguous record of this species outside the type locality Dorset (UK). The associated ammonite assemblage firmly constrains the stratigraphic position of the specimen within the Rodiles Formation, Jamesoni Zone (Pliensbachian, Lower Jurassic). It aligns the Asturian faunal succession with coeval northwestern European basins. The new material preserves diagnostic cranial and postcranial features that refine the morphological characterization of I. anningae, including previously undocumented details of the skull anatomy. Based on the length of the humerus, the specimen described here represents the largest known individual of I. anningae. Incorporation of the specimen into an updated phylogenetic dataset supports the monophyly of Ichthyosaurus and reinforces the distinctiveness of I. anningae relative to other Pliensbachian taxa. The co-occurrence of I. anningae and Leptonectes sp. in the Rodiles Formation provides new evidence for niche partitioning among Early Jurassic ichthyosaurs in the Asturian Basin, paralleling patterns documented in localities in southwestern England. Taken together, these discoveries extend the paleobiogeographic range of Early Jurassic ichthyosaurs, provide new insights into the diversity and complexity of the faunas of the Iberian margin, and offer further evidence of the close affinities of marine communities in Northern Spain with those of the Jurassic subboreal sea of the United Kingdom.