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SAURISCHIAN DINOSAURS

How were Cretaceous period saurischian dinosaurs different from Jurassic dinosaurs?

When compared to the Jurassic period, the Cretaceous period saurischian dinosaurs were still divided into the large, plant-eating sauropods (Sauropoda) and the carnivorous theropods (Theropoda). However, the only important family of sauropods in the Cretaceous were the titanosaurids (Titanosauridae); the other groups, such as the diplodocids and brachiosaurs, lost their dominance. Overall, the theropods became more diverse.

What were the titanosaurids?

The titanosaurids (or titanosaurs, the members of the groups Titanosauria and/or Titanosauroidea) were the major group and truly the only dominant group of sauropods that lived during the Cretaceous period. They represent a great mystery for paleontologists, too. In fact, only recently have skulls or relatively complete skeletons (such as the Rapetosaurus) of any of the roughly 50 species of titanosaurs been discovered.

These dinosaurs had small, slender, pencil-like teeth, similar to the diplodocids. Because of this, until recently, paleontologists put the diplodocids and titanosaurids into the same family even though parts of both dinosaurs skulls were very different. In general, the titanosaurs had small, elongated heads, large nostrils, and crests formed from the nostril bones. Most of the titanosaurs lived in the southern continents of Gondwana, especially the southern parts of todays South America and India. Bones of these dinosaurs have also been found in many other places, including Brazil, Malawi, Spain, Madagascar, Laos, Egypt, Romania, France, and the southern United States.

Were there any other sauropods that survived into the Cretaceous period?

There were very few sauropod species that survived into the Cretaceous period. Most of them, except the titanosaurids in Gondwana, were almost extinct. But there were still a few. For example, although they were abundant in the late Jurassic period, some brachiosaurs survived into the Early Cretaceous, with fossils found in Europe and Africa. There were probably more, but fossil evidence especially whole skeletons of Cretaceous sauropods (except for the titanosaurids) is scarce.

Titanosaurids

Saltasaurus: Also seen spelled incorrectly as Saltosaurus, this relatively small about 39 feet (12 meters) long sauropod had bony plates covering its back in a kind of chain-mail body armor. Fossils have been found in Argentina and, more recently, in Uruguay.

Alamosaurus: This dinosaur was up to 53 feet (16 meters) long, with relatively long forelimbs. It may have been one of the last dinosaurs to go extinct.

Spinosaurus, a species of tetanuran, was a camosaur considered to be more closely related to birds than almost any other dinosaur species (iStock).

Argentinosaurus: A good candidate for one of the largest land animals that ever lived. This sauropod evolved in South America during the Middle Cretaceous, around 100 million years ago, and may have been more than 85 feet (26 meters) in length.

How did the theropods change during the Cretaceous period?

During the Cretaceous period, the theropods became much more diverse, with ceratosaurs and the tetanurans well represented. The subgroups of the tetanurans (carnosaurs and coelurosaurs) evolved new species. For instance, the coelurosaurs, composed of the ornithomimosaurs and maniraptorans, became very diverse, although some, such as the carnosaurs, became less dominant.

Did any ceratosaurs live in the Cretaceous period?

There were some ceratosaurs (Ceratosauria, or horned reptiles) theropods that arose during the Triassic period and grew in number during the Jurassic period in the Cretaceous period. One is from a group of unusual ceratosaurs, called the Abelisauridae, a family (or clade) of ceratosaurian theropod dinosaurs. The Abelisaurids thrived during the Cretaceous period on the ancient southern supercontinent of Gondwana (now South America). One example is the up to 30-foot- (9- meter-) long, strange-looking, horned dinosaur called a Carnotaurus (meat bull).

 
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