Comparative analysis of Late Jurassic sauropod trackways from the Jura Mountains (NW Switzerland) and the central High Atlas Mountains (Morocco): implications for sauropod ichnotaxonomy

Abstract

Late Jurassic sauropod trackways from the Jura Mountains (NW Switzerland) and the central High Atlas Mountains (Morocco) are described and compared. Emphasis is put on track preservation and trackway configuration. The trackways are similar with respect to preservation and the pes and manus track outlines, but they show a large range of trackway configuration. Only one of the trackways reveals digit and claw impressions, and thus differences in trackway gauge and the position of pes and manus tracks are the most explicit characters for their distinction. The Late Jurassic to Early Cretaceous ichnotaxa Brontopodus, Parabrontopodus and Breviparopus are reviewed and a differential diagnosis is given for the trackways studied. The reference trackway of Breviparopus corresponds to one of the studied trackways of Morocco. Parabrontopodus and Breviparopus are considered to be both valid ichnotaxa, even though we recommend the latter to be formally erected based on better-preserved tracks than those currently exposed. The analysed trackways and ichnotaxa suggest that trackway configuration, notably trackway gauge (width), is not decisively influenced by extrinsic factors such as ontogenetic stage, locomotion speed and substrate properties. However, it cannot be excluded that it is related to other factors such as individual behaviour or even sexual dimorphism.