EvoSaurAf · The evolution of long-necked dinosaurs of Africa before the Cenomanian-Turonian extinction

The evolution of long-necked dinosaurs of Africa before the Cenomanian-Turonian extinction

Sauropods were 4-legged plant eating dinosaurs with long necks and tails that thrived for more than 160 million years during the Jurassic and Cretaceous until their extinction at the Cretaceous-Paleogene limit, 66 million years ago. By the beginning of Late Cretaceous (95 million years ago) only two groups remained: Titanosauria (which includes the largest land dwelling animals that ever existed) and Rebbachisauridae (smaller and short limbed sauropods with whip-like tails and shorter necks). At the end of the Cretaceous before the final extinction of dinosaurs with the exception of birds, titanosaurs were the only sauropods that remained. Both rebbachisaurids and titanosaurs had evolved independently air-borne skeletons (pneumaticity) and adaptations to feed on ground level vegetation. However, why rebbachisaurids went extinct 90 million years ago while titanosaurs thrived is unknown. How these terrestrial animals coped with an environment where sea surface temperature rose to 3 to 9 ºC higher than present-day tropical temperatures and with sea levels on the rise, eventually forming shallow seas that completely flooded Europe and divided North America and Africa into separate landmasses might have played a part. The scarce knowledge on African sauropods from the Late Cretaceous in particular was a void for this time period. However, fieldwork throughout the last 25 years in Niger yielded abundant sauropod skeletons dating from 95 million year old beds. Among these finds were seven skeletons of sauropod dinosaurs, three of them rebbachisaurids and four of them titanosaur. These skeletons range from 90 to 50 percent in completion, which is extraordinary for sauropod dinosaurs in general, where most species are known from a handful of bones on average and complete individuals are exceptional. These skeletons not only improve our knowledge on 95 million year old African dinosaur faunas but also to evaluate whether these animals fed on the same or different vegetation, whether their skeletons grew at similar or different rates or if their air sac system differed in meaningful ways in reducing their weight or the impact it had in heat exchange. Evaluation of these biological traits is a first step in understanding how the largest terrestrial animals that ever existed coped with the changing world they lived in.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз