Taxonomy of the archosaur Ornithosuchus: Reassessing Ornithosuchus woodwardi Newton, 1894 and Dasygnathoides longidens (Huxley 1877)

Abstract

The pseudosuchian archosaur Ornithosuchus, from the Lossiemouth Sandstone Formation (Late Triassic), Scotland, was the first ornithosuchid to be discovered, and the only one recorded, in the northern hemisphere. The fossil record of Ornithosuchus longidens is mainly based on natural moulds and, in a few cases, three-dimensional bony elements, complicating the interpretation of its anatomy. The taxonomy of this species has changed several times since the late 1800s and here we revisit its current status. The synonymy of Dasygnathoides longidens and Ornithosuchus woodwardi proposed by Walker (1964) is rejected, based on new interpretations of the holotype and referred specimens of Dasygnathoides longidens. The latter species is considered as a nomen dubium, because it lacks diagnostic features and cannot be identified beyond Pseudosuchia. As a result, Ornithosuchus woodwardi is resurrected as a valid species and its diagnosis is emended. The body size range of Ornithosuchus woodwardi is reduced to about a half, because ELGNM 1, previously considered the largest specimen of the genus, can no longer be referred to it. Dasygnathoides longidens cannot be assigned to any of the known archosauriforms from the Lossiemouth Sandstone Formation, but it still represents the largest predator currently known for its fauna.