Re-evaluating the Plagne (Tithonian) theropod trackway: quantitative analyses provide evidence on the presence of Megalosauripus transjuranicus in the French Jura

The Upper Jurassic (Oxfordian–Tithonian) carbonate platforms of the Jura region (France and Switzerland) are key to understanding dinosaur ichnology. This record is notable for both the abundance and exceptional preservation of the tracks, which provide valuable insights for ichnotaxonomic analyses and classification. The Plagne tracksite from the Tithonian of the French Jura, preserves numerous tracks of both theropods and sauropods, including the Brontopodus plagnensis type trackway, and their exceptional preservation enables detailed and quantitative studies. This study quantitatively tests the hypothesis that the theropod trackway PGN02, from the Plagne tracksite, can be assigned to the ichnospecies Megalosauripus transjuranicus. Two quantitative approaches were used: Whole-Track Analysis and two-dimensional geometric morphometrics. Both methods indicate a close morphological affinity between PGN02 and M. transjuranicus, and a distinction from other large theropod ichnotaxa (e.g., Eubrontes, Jurabrontes). The observed differences between PGN02 and the M. transjuranicus holotype are interpreted as size-related shape variation, suggesting that the PGN02 trackmaker was a smaller individual than the one that created the holotype, potentially reflecting ontogenetic variation. Plagne’s PGN02 tracks extend the geographic range of M. transjuranicus to the Tithonian of the French Jura, reinforcing the widespread presence of its trackmaker in Late Jurassic Laurasian ecosystems.