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 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 largest 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). 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. However, some propose that this group (which is known as the Megalosauroidea) is paraphyletic and that spinosaurs represent either the most basal tetanurans or the basal carnosaurs which are less derived than the megalosaurids. 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.
History of discovery
The first spinosaurid fossil, a single conical tooth, was discovered circa 1820 by British paleontologist Gideon Mantell in the Wadhurst Clay Formation. In 1841, naturalist Sir Richard Owen mistakenly assigned it to a crocodilian he named Suchosaurus (meaning "crocodile lizard"). A second species, S. girardi, was later named in 1897. However, the spinosaurid nature of Suchosaurus was not recognized until a 1998 redescription of Baryonyx. The first fossils referred to a spinosaurid were discovered in 1912 at the Bahariya Formation in Egypt. Consisting of vertebrae, skull fragments, and teeth, these remains became the holotype specimen of the new genus and species Spinosaurus aegyptiacus in 1915, when they were described by German paleontologist Ernst Stromer. The dinosaur's name meant "Egyptian spine lizard", in reference to the unusually long neural spines not seen previously in any other theropod. In April 1944, the holotype of S. aegyptiacus was destroyed during an allied bombing raid in World War II. In 1934, Stromer referred a partial skeleton also from the Bahariya Formation to a new species of Spinosaurus; the specimen has since been alternatively assigned to another African spinosaurid, Sigilmassasaurus. In 1983, a relatively complete skeleton was excavated from the Smokejacks pit in Surrey, England. These remains were described by British paleontologists Alan J. Charig and Angela C. Milner in 1986 as the holotype of a new species, Baryonyx walkeri. After the discovery of Baryonyx, many new genera have since been described, with the majority from very incomplete remains. However, other finds bear enough fossil material and distinct anatomical features to be assigned with confidence. Paul Sereno and colleagues described Suchomimus in 1998, a baryonychine from Niger, on the basis of a partial skeleton found in 1997. In 2004, partial jaw bones were recovered from the Alcântara Formation, these were referred to a new genus of spinosaurine named Oxalaia in 2011 by Alexander Kellner. Fragmentary remains belonging to a large spinosaurid were collected in 2021 from the Vectis Formation on the Isle of Wight. The material lacks distinct characteristics that would prompt the erection of a new species. However, the size of the bones is comparable to the size of Spinosaurus, making the "White Rock spinosaurid" one of the largest theropods ever found in Europe in addition to the first theropod identified in the Vectis Formation. In 2024, Riojavenatrix lacustris became the fifth spinosaurid species to be named from material found in the Iberian Peninsula, following Camarillasaurus, Iberospinus, Protathlitis, and Vallibonavenatrix. The fossils hail from the Early Cretaceous Enciso Group of La Rioja, Spain. In 2026, Paul Sereno and colleagues described Spinosaurus mirabilis, a new species of Spinosaurus from the Farak Formation of Niger.
Description
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