Late Triassic aetosaur (Archosauria) from Krasiejow (SW Poland): new species or an example of individual variation?

An aetosaur discovery in Krasiejow (SW Poland), in Late Triassic deposits, was first described by Sulej in 2010 as a new species carrying the name Stagonolepis olenkae. However, new fossil material suggests that its taxonomical position is not as clear as was initially presumed. In the new material from the Triassic' site of Krasiejow, the typical features of Stagonolepis robertsoni, described by Walker in 1961 from the Elgin area of Scotland, were identified (i.e. frontal/prefrontal width ratio), as well as features of S.olenkae (i.e. angle between ventral edge of the maxilla and ventral edge of the antorbital fenestra). However, distinct features from both species, such as the shape of the canal at the dorsal surface of the frontal, are present. Some of the variation is similar to sexual dimorphism observed in recent amphibians and reptiles. These variations, as well as the fact that the postcranial skeleton was previously described as S.robertsoni by Lucas and co-workers in 2007, suggest that the taxonomical affiliation of the Krasiejow aetosaur (and/or the number of aetosaur species) should be re-considered. Copyright (c) 2015 John Wiley & Sons, Ltd.