The oldest evidence for birds in Northern Gondwana? Small tridactyl footprints from the Middle Jurassic of Msemrir (Morocco)

We revise a famous set of fossil footprints that were described in the mid-1980s from the Middle Jurassic (Bathonian) of Morocco and that have often been considered to be an early record for Mesozoic birds. If correct, these tracks are the oldest records of birds from Gondwana and would have critical biogeographic and palaeobiological implications. The oldest skeletal fossils of avians are from the Late Jurassic of Germany (Laurasia). Thus, these important historical footprints are re-described and re-examined and new analyses are carried out on the additional tracks that also occur on the surface but that have never been described before. All the tracks on the surface show the same morphological characteristics, though their size is variable, and are compared here to known dinosaur and bird ichnotaxa. We used a laser scanner to generate a 3D digital model of the slab; this new approach allowed detailed descriptions of the specimens, the identification of new footprints on the surface, and the conclusion that they were likely left by non-avian dinosaurs (rather than birds). We show the potential of this new approach to the study of fossil footprints and trackways; high-resolution imaging and laser scanning add new information fundamental for a revision of the criteria for distinguishing between closely-related vertebrate groups, in this case dinosaurs and birds.