A new specimen of Dacentrurus armatus Owen, 1875 (Ornithischia: Thyreophora) from the Upper Jurassic of Spain and its taxonomic relevance in the European stegosaurian diversity

Abstract Dacentrurus armatus was the first stegosaur described in the European Upper Jurassic at the end of the 19th century. The description of a second dacentrurine taxon, ‘Miragaia longicollum’, diagnosed from material non-comparable with the D. armatus holotype, has been controversial, and its validity has been challenged. In this study, we describe a new relatively complete stegosaurian postcranial skeleton from the Villar del Arzobispo Formation (Upper Jurassic, Spain). The systematic study of this new specimen and a comprehensive taxonomic assessment of the material not attributed to Stegosaurus from the Upper Jurassic of Europe, reveal high morphological homogeneity and an absence of morphological criteria for distinguishing two dacentrurine taxa. Therefore, ‘Mi. longicollum’ is proposed as a subjective junior synonym of D. armatus. Moreover, a new diagnosis for D. armatus is suggested based on the holotype and referred specimens. As a result, only two stegosaurian species, Stegosaurus stenops and D. armatus, are recognized in Europe during the Late Jurassic. Finally, the species longispinus from the Morrison Formation (Upper Jurassic, USA) is returned to the genus Alcovasaurus.