Revisiting Megalosauripus transjuranicus: new ichnotaxonomical insights from the Plagne tracksite (Tithonian, France) and implications for Late-Jurassic theropod ichnotaxonomy

The Jura region (France and Switzerland) is a key area for studying Late-Jurassic (Kimmeridgian–Tithonian) dinosaur tracks. Cyclical fluctuations in sea levels during this period exposed the Jura carbonate platform, creating land bridges that facilitated the dispersal of vertebrates and the formation of track-bearing surfaces. As a result, there are numerous tracksites in both countries. They exhibit well-preserved tracks with strong morphological similarities and possible ichnotaxonomical affinities. Dinosaur ichnotaxonomy is based primarily on morphological rather than behavioural characteristics, and in many studies, the correct attribution of footprints to specific ichnotaxa has been problematic. In this study, we propose classifying Plagne theropod tracks in Megalosauripus transjuranicus through a quantitative approach, using two landmark-based analyses: Geometric Morphometrics (GM) and Whole-Track Analysis (WTA). Our results reveal clear clustering in morphospace for GM and morphological overlap in the WTA, supporting this attribution. Utilizing a dataset including other Jurassic theropod ichnotaxa, new ichnotaxonomical affinities have been revealed. This study records the presence of M. transjuranicus in the French Jura and highlights the utility of this approach in ichnotaxonomical identification. Furthermore, it extends the known stratigraphic range of Megalosauripus transjuranicus into the Tithonian in France and up to the Berriasian in Spain, suggesting a longer persistence than previously documented for large theropods in these areas.