First tetrapod swim traces and associated ichnofauna from the Mesozoic of Algeria, North Africa

Abstract

We report tetrapod traces and associated ichnofauna from two stratigraphic, dominantly terrestrial levels of the Tiout Formation (Valanginian-latest Albian to lower Cenomanian) in Laghouat and Brezina areas, Central Saharan Atlas (Djebel Amour), northwestern Algeria and discuss their paleoecological implications. The assemblages display abundant footprints that show similarities with crocodylian swim traces assigned to Hatcherichnus known from Jurassic–Cretaceous deposits of North America and Morocco. However, there is also some similarity in shape with traces attributed to swimming pterosaurs by different authors. Because of the isolated materials from Algeria and the lack of distinct trackways, we leave the decision on the tracemaker open. The majority of the traces are tridactyl to tetradactyl imprints consisting of parallel furrows left by the claws of swimming or buoyant individuals. Tetrapod swim traces are identified, described, and figured herein for the first time from the Mesozoic of Algeria. These vertebrate fossil traces are associated with a low-diversity invertebrate marine ichnofauna, including cf. Bergaueria isp., Phycodes isp., Sinusichnus cf. seilacheri, and Thalassinoides suevicus. Together with body fossil data, including abundant fishes and non-avian dinosaurs, they indicate a diverse animal community populating a fluvial system environment with marine influence. Paleoecological and paleoenvironmental features of the Tiout Formation add new information to the ichnoassemblages previously reported from the ‘mid’-Cretaceous of North Africa.