Spinosauridae

Spinosauridae (or spinosaurids) is a clade or family of tetanuran theropod dinosaurs comprising ten to seventeen known genera. Spinosaurid fossils have been recovered worldwide, including Africa, Europe, South America, and Asia. Their remains have generally been attributed to the Early to early Late Cretaceous.

Spinosaurids were large bipedal carnivores. Their crocodilian-like skulls were long, low, and narrow, bearing conical teeth with reduced or absent serrations. The tips of their upper and lower jaws fanned out into a spoon-shaped structure similar to a rosette, behind which there was a notch in the upper jaw that the expanded tip of the lower jaw fit into. The nostrils of spinosaurids were retracted to a position further back on the head than in most other theropods, and they had bony crests on their heads along the midline of their skulls. Their robust shoulders wielded stocky forelimbs, with three-fingered hands that bore an enlarged claw on the first digit. In many species, the upwards-projecting neural spines of the vertebrae (backbones) were significantly elongated and formed a sail on the animal's back (hence the family's etymology), which supported either a layer of skin or a fatty hump.

The genus Spinosaurus, from which the family, one of its subfamilies (Spinosaurinae) and tribe (Spinosaurini) take their names, is among the longest known terrestrial predators from the fossil record, with an estimated length of up to 14 meters (46 ft) and body mass of up to 7.4 metric tons (8.2 short tons) (similar to the weight of an African elephant). The closely related genus Sigilmassasaurus may have reached a similar or greater size, though its taxonomy is disputed. Direct fossil evidence and anatomical adaptations indicate that spinosaurids were at least partially piscivorous (fish-eating), with additional fossil finds indicating they also fed on other dinosaurs and pterosaurs. The osteology of spinosaurid teeth and bones has suggested a semiaquatic lifestyle for some members of this clade. This is further indicated by various anatomical adaptations, such as retracted eyes and nostrils; and the deepening of the tail in some taxa, which has been suggested to have aided in underwater propulsion akin to that of modern crocodilians. Spinosaurs are proposed to be closely related to the megalosaurid theropods of the Jurassic. This is due to both groups sharing many features such an enlarged claw on their first manual ungual and an elongated skull.^[8] However, some propose that this group (which is known as the Megalosauroidea) is paraphyletic and that spinosaurs represent either the most basal tetanurans^[9] or as basal carnosaurs which are less derived than the megalosaurids.^[10] Some have proposed a combination of the two ideas with spinosaurs being in a monophyletic Megalosauroidea inside a more inclusive Carnosauria that is made up of both allosauroids and megalosauroids.^[11]