Spinosaurus (; ) is a genus of large spinosaurid theropod dinosaurs that lived in what is now North Africa during the Cenomanian age of the Late Cretaceous period, about 100 to 94 million years ago. The genus was known first from Egyptian remains discovered in 1912 and described by German palaeontologist Ernst Stromer in 1915. The original remains were destroyed in World War II, but additional material came to light in the early 21st century. It is unclear whether one or two species are represented in the fossils reported in the scientific literature. The type species, S. aegyptiacus, is mainly known from the Bahariya Formation in Egypt and the Kem Kem beds in Morocco. The other species, S. mirabilis, is known from the Farak Formation in Niger. Possible junior synonyms include Sigilmassasaurus and the dubious S. maroccanus from the Kem Kem beds and Oxalaia from the Alcântara Formation in Brazil, though the distinction and validity of these taxa have been debated.
Spinosaurus is among the largest known terrestrial carnivores; other large carnivores comparable to Spinosaurus include theropods such as Tyrannosaurus, Giganotosaurus and the contemporary Carcharodontosaurus. A 2022 study suggests that S. aegyptiacus could have reached in length and in body mass. The skull of Spinosaurus was long, low, and narrow, similar to that of a modern crocodilian, and bore straight conical teeth with few to no serrations. It would have had large, robust forelimbs bearing three-fingered hands, with an enlarged claw on the first digit. The distinctive neural spines of Spinosaurus, which were long extensions of the vertebrae, grew to at least long and were likely to have had skin connecting them, forming a sail-like structure. The hip bones of Spinosaurus were reduced, and the legs were very short in proportion to the body. Its long and narrow tail was deepened by tall, thin neural spines and elongated chevrons, forming a paddle-like structure.
Spinosaurus is known to have eaten both aquatic and terrestrial prey. Evidence suggests that it was semiaquatic, although the extent of its swimming capability has been strongly contested. Spinosauruss leg bones had a high bone density, allowing for better buoyancy control. Multiple functions have been put forward for the dorsal sail, including thermoregulation and display; either to intimidate rivals or attract mates. It lived in a humid environment of tidal flats and mangrove forests alongside many other dinosaurs as well as fish, crocodylomorphs, squamates, turtles, pterosaurs, and plesiosaurs.
Discovery and naming Initial finds
The first discovery of Spinosaurus may have been in October 1898, when French geologist Fernand Foureau unearthed two unusual teeth in Cenomanian-aged sediments of the Djoua Escarpment in what is now southern Algeria, then French Algeria. Foreau found the specimens while on the Foureau-Lamy Expedition of 1898-1900, which traveled across the Sahara from Algeria to Lake Chad. In 1905, French geologist Emile Haug described the fossils unearthed while on the expedition, including the two teeth which he assigned to the fish Saurocephalus. However, in 1915 German paleontologist and describer of Spinosaurus Ernst Stromer reassigned the teeth to Spinosaurus. Later studies have agreed with this assessment, however the teeth themselves has since been lost.
The first confidently referable remains of Spinosaurus were discovered in the autumn of 1912 by Austro-Hungarian paleontologist Richard Markgraf, a fossil collector who was financed by Stromer and the Bavarian Academy of Sciences, in deposits of the Bahariya Formation in the Bahariya Oasis of western Egypt. The sediments of the Bahariya Formation come from the Cenomanian stage of the Late Cretaceous period, one of many Cretaceous-aged formations of North Africa. In 1915, Stromer described these remains as belonging to a new genus and species of dinosaur, Spinosaurus aegyptiacus. The generic name Spinosaurus comes from the Latin spina, meaning "spine", and the Greek sauros, meaning "lizard", and thus "spine lizard". The specific name aegyptiacus derives from Egypt, where the fossils were unearthed. Spinosaurus aegyptiacus type specimen (BSP 1912 VIII 19) consists of elements of the mandible (lower jaw), a maxilla (upper jaw) fragment, cervical (neck), caudal (tail), and dorsal (back) vertebrae, including much of the , ribs, teeth, and some gastralia (belly ribs).
In April 1914, another expedition to the Bahariya Oasis by Markgraf unearthed an incomplete skeleton (BSP 1922 X45) of a spinosaurid. This skeleton was poorly preserved and, as a result of illegal unpacking and insufficient repacking by Anglo-Egyptians during World War I, was greatly damaged. After much deliberation due to the war and poor Anglo-German relations, the skeleton arrived in Germany in 1922 where it was described by Stromer in 1934. Stromer assigned the skeleton to Spinosaurus, but considered it different enough from S. aegyptiacus that it would belong to its own Spinosaurus species, "Spinosaurus B".
In 1936, Stromer worked with Dr. Erhardt (the first name is unknown) to create a skeletal reconstruction of Spinosaurus based on fossils of the holotype, "Spinosaurus B", and related taxa. Although Stromer was hesistant about the lack of known remains, he and Erhardt produced a restoration that filled in missing elements of Spinosaurus''' skeleton with the tyrannosaurid theropods Tyrannosaurus and Gorgosaurus. Unfortunately, during the night of April 24/25, 1944, the building of the Paläontologisches Museum München (Bavarian State Collection of Paleontology) of the Bavarian Academy of Sciences was severely damaged during the British Bombing of Munich. Due to personal and political tensions between Stromer and the museum's director Karl Beurlen, who was a fervent Nazi, the Spinosaurus fossils held there were not rehoused and subsequently destroyed as a result of the bombing. Stromer's finds, including Spinosaurus, received little academic or public attention. In 1995, Stromer's son donated his father's archives to the Paläontologische Staatssammlung München, leading to a 2006 study by American researcher Joshua Smith and colleagues of the photographs, two of which were of Spinosaurus holotype. Based on these photographs of the mandible and the entire specimen as mounted, Smith concluded that Stromer's original 1915 drawings were slightly inaccurate. No more spinosaurid material would be described from Africa until the latter half of the 20th century, with Spinosaurus remaining an enigmatic and mysterious theropod.
Additional finds
Beginning in the 1980s, Spinosaurus material began being described from sites in Algeria, Morocco, and Tunisia, although these fossils were often isolated and fragmentary. In 1986, a paper referred several teeth found in Cretaceous deposits in Tunisia to Spinosaurus, being the first evidence of the taxon's existence in the country. In 1989, French paleontologist Eric Buffetaut assigned two jaw fragments and a tooth that had been unearthed in a deposit of the Kem Kem Beds in Taouz, Morocco to Spinosaurus sp., expanding the known distribution of the genus to Morocco. In the 1990s, a wealth of spinosaurid remains were described from South America, Asia, Africa, and Europe, strengthening the understanding of Spinosaurus and Spinosauridae. However, much of the anatomy of Spinosaurus still remained obscure and many studies proposed that fossils previously assigned to the genus or Sigilmassasaurus were actually from iguanodont ornithischians,Canale, Juan & Novas, Fernando & Haluza, Alejandro. (2008). Comments about the cervical vertebrae referred to the African theropods Carcharodontosaurus and Sigilmassasaurus. Actas III Congreso Latinoamericano de Paleontología de Vertebrados. Neuquén 22-25 Septiembre, 2008. megaraptorans, carcharodontosaurids, or other forms of theropod.
Additional fossils of Spinosaurus were recovered from the Kem Kem Beds in the Tafilalt Oasis of Morocco, near the site of the ancient city of Sigilmassa. In 1996, Canadian paleontologist Dale Russell described these fossils, consisting of three cervical vertebrae, two mandible fragments, and the neural spine of a dorsal vertebra, as belonging to a new species of Spinosaurus, S. maroccanus. The specific name, maroccanus, derives from royaume du Maroc ("Kingdom of Morocco"), where the fossils were unearthed. The site where S. maroccanus fossils were found is located in the south of the country and made up of red sandstone, known by various names, including the Grès rouges infracénomaniens, Continental Red Beds, and lower Kem Kem Beds. Of these fossils, one cervical vertebra (cataloged at the Canadian Museum of Nature as NMC 50791), was selected as the holotype of S. maroccanus.S. maroccanus was differentiated from S. aegyptiacus based on the length of its neck vertebrae. Specifically, Russell claimed that the ratio of the length of the centrum (body of vertebra) to the height of the posterior was 1.1 in S. aegyptiacus and 1.5 in S. maroccanus. Later authors have been split on this topic, with some authors noting that the length of the vertebrae can vary from individual to individual, that the holotype specimen was destroyed and thus cannot be compared directly with the S. maroccanus specimen, and that it is unknown which cervical vertebrae the S. maroccanus specimens represent. Therefore, though some have retained the species as valid without much comment, most researchers regard S. maroccanus as a nomen dubium (dubious name), a junior synonym of S. aegyptiacus, or a junior synonym of Sigilmassasaurus brevicollis. Some studies have referred to the holotype and other referred specimens of S. maroccanus (NMC 50791 and MNHN SAM 124–128) as S. cf. aegyptiacus. The specimens previously ascribed as paratypes of S. maroccanus (NMC 41768 and NMC 50790) were reidentified as spinosaurid specimens that are currently not identifiable at the generic level.
In 1996, a study by American paleontologist Paul Sereno and colleagues assigned cervical vertebrae referred to "Spinosaurus B" and the spinosaurid Sigilmassasaurus (a possible synonym of Spinosaurus) to the carcharodontosaurid Carcharodontosaurus. This was based on the erroneous belief that a cervical vertebra (SGM Din-3) found nearby a skull of Carcharodontosaurus (SGM Din-1) belonged to the same individual. Sereno and colleagues also reasoned that stout cervicals like those of Sigilmassasaurus would be needed to carry the skulls of carcharodontosaurids, however later analyses have proven that "Spinosaurus B" and Sigilmassasaurus are not synonyms or contain fossils from Carcharodontosaurus. Some studies have continued to refer "Spinosaurus B" to Sigilmassasaurus, although this is still debated. In 2003, Oliver Rauhut suggested that Stromer's Spinosaurus holotype (name-bearing) specimen was a chimera, composed of vertebrae and neural spines from a carcharodontosaurid similar to Acrocanthosaurus and a mandible from Baryonyx or Suchomimus, an analysis that was rejected in at least one subsequent paper.
Proposed neotype