Illustration of Spinosaurus.
Spinosauridae is a family of unusual theropod dinosaurs. Members of this group were generally rather large, bipedal predators with elongated, crocodile-like skulls, sporting conical teeth with no or only very tiny serrations. The front dentary teeth were fanning out giving the animal a characteristic look. The name of this family alludes to the typically conspicuous sail-like structure protruding from the back of at least some species. The purpose of the sail is disputed, but a popular explanation is that it may have served as a thermoregulator or as a way to scare off potential attackers.
All spinosaurids appeared during the Cretaceous period without ever, judging by the scarce findings, becoming abundant. Spinosaurid fossils have been recovered in Africa, Europe, South America, and Asia.
The family Spinosauridae was named by Ernst Stromer in 1915 to include the single genus Spinosaurus. The family was expanded as more close relatives of Spinosaurus were uncovered. The first cladistic definition of Spinosauridae was provided by Paul Sereno in 1998 (as "All spinosaurids closer to Spinosaurus than to Torvosaurus).
Spinosauridae ontains two subfamilies--Spinoaurinae and Baryonychinae. The subfamily Spinosaurinae was named by Sereno in 1998, and defined by Holtz et al. (2004) as all taxa closer to Spinosaurus aegyptiacus than to Barynonyx walkeri. The subfamily Baryonychinae was named by Charig & Milner in 1986. They erected both the subfamily and the family Baryonychidae for the newly discovered Baryonyx, before it was referred to the Spinosauridae. Their subfamily was defined by Holtz et al. in 2004, as the complimenary clade of all taxa closer to Barynonyx walkeri than to Spinosaurus aegyptiacus.
- Superfamily Megalosauroidea
Evidence shows that spinosaurids fed on fish as well as a variety of other small to medium sized animals, including small dinosaurs. Baryonyx was found with fish scales and the digested bones of a young Iguanodon in its stomach cavity, one specimen of Spinosaurus had a fish bone lodged in one tooth socket, and there is one documented example of a spinosaurid having eaten a pterosaur (Buffetaut et al., 2004).
- Buffetaut, E., D. Martill & F. Escuillié (2004). "Pterosaurs as part of a spinosaur diet." Nature, 430: 33.