Tholacosaurus

Tholacosaurus is a genus of large, herbivorous sauropod dinosaur that lived during the Late Cretaceous period, approximately 75 to 70 million years ago, in what is now North America. It is known from a single, nearly complete skeleton discovered in the Two Medicine Formation of Montana, United States. The type species is Tholacosaurus atavus.

Tholacosaurus is one of the largest known sauropods, with some estimates suggesting it could have reached lengths of up to 30 meters (98 feet) and weighed as much as 20 tons. Its body was likely supported by a long, whip-like tail, which may have helped it maintain balance while walking on its long legs. The forelimbs were relatively short, ending in five-fingered hands, while the hindlimbs were robust and ended in three-toed feet.

The most distinctive feature of Tholacosaurus is its skull, which is characterized by a unique combination of features. It has a long, low snout with a prominent ridge running along the top, and a pair of large, upward-curving horns above the eyes. The jaws were filled with numerous, closely spaced teeth, adapted for cropping vegetation.

Tholacosaurus is classified within the family Diplodocidae, a group of long-necked sauropods that includes well-known genera like Diplodocus and Apatosaurus. Its discovery has provided valuable insights into the diversity and evolution of sauropods during the Late Cretaceous period. However, due to the fragmentary nature of the fossil record, much about Tholacosaurus' biology and ecology remains unknown.