Evidence of theropod dinosaurs in the upper hauterivian–lower barremian of Jebel Kebar (central Tunisia): Paleobiogeographic implications

Abstract

The fossil record of Mesozoic dinosaurs in Tunisia has long been thought to be restricted exclusively to the southern part of the country. Although tidal and continental environments have been recognized within Cretaceous formations in central Tunisia based on sedimentological analyses, no skeletal remains ascribable to dinosaurs have been found in these deposits. The hypothesis of a possible land connection between central and southern Tunisia during the Early Cretaceous has not been previously explored due to notable lateral variations in facies, marked by the recurrent occurrence of shallow marine deposits separating these domains. The vertebrate ichnological record in the Central Tunisian Atlas was limited to isolated tridactyl footprints exclusively observed in the Albian Kebar Formation. Here, we report the first dinosaur tracks from the pre-Albian Cretaceous (upper Hauterivian–lower Barremian) of central Tunisia. These tracks consist of large tridactyl footprints left behind by medium to large-sized non-avian theropods. They occur within an extensively fractured dolostone bed and exhibit poor morphological preservation. Besides their dimensions, some tracks show morphological features, including broad digit impressions with some terminating in sharp claw traces, low to moderate mesaxony, and a wide divarication angle of the outer digits, reminiscent of the ichnogenus Megalosauripus. However, due to their poor state of preservation and limited number, we refrain from assigning these tracks to the ichnogeneric level and refer to them as indeterminate eubrontid footprints. The occurrence of theropod tracks in the Lower Cretaceous of central Tunisia confirms the sedimentology-based hypotheses about a temporal emergence of parts of this area, which was probably related to tectonic events. We compile previous biostratigraphic, sedimentological, and paleoichnological data to suggest possible periodic connections between the mainland in the south and the tidal flat environments within the central basins. Additionally, two possible scenarios regarding the biogeographic implications of the Jebel Kebar tracks are discussed. The first scenario suggests that a Gondwanan theropod fauna would have been exploring and residing in newly emerged regions of higher latitudes, whereas the alternative scenario posits the existence of a paleogeographic link between the northern margin of Gondwana and Adria, which would have allowed an interchange of theropod faunas between the two landmasses at least in the early Barremian.