Sarcosuchus (), from Ancient Greek σάρξ (sárx), meaning "flesh", and Σοῦχος (Soûkhos), meaning "Sobek", is a genus of crocodyliform that lived during the Early Cretaceous (Hauterivian to Albian ages, ) in North Africa and Brazil. The genus was first described in 1966 by French paleontologists Frances de Broin and Philippe Taquet on the basis of an incomplete skull that was discovered in Gadoufaoua, northern Niger. They named the type species S. imperator. Prior to 1966, fragmentary fossils of S. imperator had been found in French expeditions to the Sahara as well. In 1977, the species Crocodylus hartti, which had been discovered in Early Cretaceous deposits in Brazil in the 1850s-60s, was reassigned to Sarcosuchus. S. hartti is known from largely fragmentary material compared to S. imperator and is smaller in size. The best-preserved remains of Sarcosuchus were not unearthed until 1997 and 2000, when American paleontologist Paul Sereno and University of Chicago crews collected six new specimens, including several skulls and postcranial remains, of S. imperator.
Sarcosuchus is a member of the extinct family Pholidosauridae, a clade of largely aquatic neosuchians distantly related to living crocodylians. S. imperator is one of the biggest crocodylomorphs known, with fully grown individuals estimated to have reached up to in total length and in weight. It had somewhat telescoped eyes and a long snout accounting for 75% of the length of the skull. The longest reported skull is in length, while the longest confirmed skull is slightly shorter at long. There were 35 teeth in each side of the upper jaw, while in the lower jaw there were 31 teeth in each side. The length of the upper jaw was also noticeably greater than that of the lower one, leaving a gap between them when the jaws were shut that created an overbite. In young individuals, the shape of the snout resembled that of the living gharial, but in fully grown individuals have much broader snouts.
Sarcosuchus may have had a Nile crocodile-like lifestyle in which it hunted large, terrestrial prey. This could have included dinosaurs such as the ornithopod Ouranosaurus and the sauropod Nigersaurus. However, biomechanical analyses of Sarcosuchus fossils indicate that it was not capable of a crocodile-like "death roll". In the Early Cretaceous, North Africa and Brazil were blanketed in mangrove forests and wetlands, fostering a hotspot of dinosaur, fish, crocodyliform, and pterosaur diversity. Isotopic analyses of S. imperator bones suggest that it had a diet composed of both fish and large dinosaurs.
Discovery and naming Early findings
Fossils of Sarcosuchus were first discovered in the Fort Montserrate and Plataforma localities in the city of Salvador, Bahia State in northeastern Brazil in the 1850s by British petrologist Samuel Allport. Geologically, these locales are composed of highly-fossiliferous (fossil-bearing) conglomerates, sandstones, shales. This consisted of several isolated crocodilian teeth that were unearthed alongside fossils of fish, molluscs, and other crocodilians. Allport described them in 1860, where he assigned them to an indeterminate crocodilian. From 1864-65, an expedition enacted by Swiss-American naturalist Louis Agassiz and American professor Charles F. Hartt known as the Thayer Expedition collected additional fossils from the area. Two miles northwest of the locality at a site in proximity to the Bahia Railroad, the expedition collected additional remains, including a large, distinct, crocodilian tooth. All of the crocodilian teeth were then divided into two morphotypes: one with deep, continuous striae (morphotype 1) and one with a wrinkled surface (morphotype 2). These teeth were then sent to American paleontologist Othniel Charles Marsh who described them in 1869. Marsh placed the teeth into two new species: Thoracosaurus bahiensis, based on morphotype 1, and Crocodylus hartti, based on morphotype 2. However, the former is now classified as a nomen dubium. Marsh failed to select a holotype (name-bearing) specimen for C. hartti, though one of the teeth, now cataloged at the Yale Peabody Museum as YPM 516, was later selected as the lectotype while the rest of the teeth described by Allport (1860) are paralectotypes. In 1907, a host of other gigantic crocodilian remains were described by British paleontologists Joseph Mawson and Arthur Smith Woodward. These subsisted of specimens recovered over years of field work in Bahia, including an incomplete mandible (lower jaw) (BMNH R3423), a dorsal (top) osteoderm (dermal scute), and two teeth (BMNH R3079, 2983), that they referred to C. hartti. Mawson and Woodward (1907) went on to reclassify C. hartti as well into the British genus Goniopholis.
Fossils of the type species, S. imperator, were first unearthed between 1946 and 1959 during a series of French geological expeditions led by French paleontologist Albert-Félix de Lapparent to outcrops of the Cretaceous-aged "Continental Intercalaire" Formation outside of Aoulef, Algeria, Fogarra Ben Draou, Mali, and Jebel El Kambout, Tunisia in the then-French Sahara. Among the fossils recovered included teeth, osteoderms, ribs, skull fragments, and incomplete vertebrae (backbones). In 1957, during a separate volume of expeditions, French geologist Hugues Faure discovered Sarcosuchus teeth in northern Niger. Although believed to come from a deposit of the Elrhaz Formation, later research by American paleontologist Paul Sereno and colleagues has interpreted it as belonging to the Cenomanian-aged Farak Formation instead. In 1964, a research team from the French Atomic Energy Commission looking for uranium discovered a nearly complete skull of a large crocodylomorph at the Gadoufaoua locality, a series of strata from the Elrhaz Formation in the western Ténéré of Niger. Gadoufaoua is represented by a long-stretch of pre-Cenomanian sandstones, likely deriving from the Barremian to Albian stages of the Lower Cretaceous period. This indicates it is between 125 and 112 million years old. The next year, this skull was transported to the National Museum of Natural History in Paris for study, though it now resides in the Musée National Boubou Hama in Niamey, Niger. In 1966, French paleontologists Frances de Broin and Philippe Taquet described all of the remains recovered on French expeditions as belonging to a new genus and species of pholidosaurid crocodylomorph, named Sarcosuchus imperator. They established the skull as the holotype specimen. The genus name, Sarcosuchus, comes from the Ancient Greek σάρξ (sárx), meaning "flesh", and Σοῦχος (Soûkhos), meaning "Sobek", in reference to the crocodile-headed god of Egyptian lore. The specific name, imperator, is from the Latin word imperare meaning "to command".
Later discoveries
In 1977, French paleontologists Philippe Taquet and Eric Buffetaut reassigned Goniopholis hartti to Sarcosuchus based on commonalities between the teeth, jaws, and osteoderms of S. imperator and G. hartti. This has been supported by later studies, including a full redescription by Brazilian paleontologist Rafael Souza and colleagues in 2019. During the 1990s and 2000s, renewed interest in the Cretaceous strata of northern Africa led to a series of expeditions by the University of Chicago. This included to the Tiourarén Formation of Morocco in 1993, the Kem Kem Beds of Morocco in 1995, and the Elrhaz Formation in 1997 and 2000. On his 1997 expedition to outcrops of the Elrhaz Formation in the Ténéré Desert in northern Niger, American paleontologist Paul Sereno and his crew unearthed numerous remains of dinosaurs, turtles, and Sarcosuchus. The follow-up expedition in 2000 was more successful in unearthing Sarcosuchus remains. Partial skeletons, numerous skulls and 20 tons of assorted other fossils were recovered from the deposits of the Elrhaz Formation. It took about a year to prepare the Sarcosuchus remains.
A tooth enamel from the Ifezouane Formation (lower Kem Kem beds) of Morocco was identified as cf. Sarcosuchus. Fossil teeth from the area of Nalut in northwestern Libya, possibly Hauterivian to Barremian in age, might be referable to S. imperator. Indeterminate Sarcosuchus material including dorsal osteoderms in anatomical connection, isolated teeth and fragmentary skeletal remains including a left scapula, mandible fragment, dorsal vertebrae, ilium and a proximal portion of a femur was described from the Oum Ed Dhiab Member in Tunisia in 2018. Description Size
A common method to estimate the size of crocodiles and crocodile-like reptiles is the use of the length of the skull measured in the midline from the tip of the snout to the back of the skull table, as in living crocodilians there is a strong correlation between skull length and total body length in subadult and adult individuals irrespective of their sex. This method was used by Sereno et al. (2001) for Sarcosuchus due to the absence of a complete enough skeleton. Two regression equations were used to estimate the size of S. imperator, they were created based on measurements gathered from 17 captive gharial individuals from northern India and from 28 wild saltwater crocodile individuals from northern Australia, both datasets supplemented by available measurements of individuals over in length found in the literature. The largest known skull of S. imperator (the type specimen) is long ( in the midline), and it was estimated that the individual it belonged to had a total body length of . Its snout-vent length of was estimated using linear equations for the saltwater crocodile and in turn this measurement was used to estimate its body weight at . This shows that Sarcosuchus was able to reach a maximum body size not only greater than previously estimated but also greater than that of the Miocene Rhamphosuchus, the Late Cretaceous Deinosuchus, and the Miocene Gryposuchus and Purussaurus according to most estimates at the time and a few years after.
However, extrapolation from the femur of a subadult individual as well as measurements of the skull width further showed that the largest S. imperator was significantly smaller than was estimated by Sereno et al. (2001) based on modern crocodilians. O'Brien et al. (2019) estimated the length of the largest S. imperator specimen at nearly and body mass at based on longirostrine crocodylian skull width to total length and body width ratio. The highest upper quartile reconstructed length and body mass for the specimen is and , respectively. Skull Sarcosuchus has a very long skull proportionally with a relatively elongated snout, which makes up about 75% of the total cranial length. Furthermore, it is broader than in gharials and other narrow-snouted crocodyliforms. The longest reported skull is in length, however it remains undescribed, while the longest confirmed skull is slightly shorter at long, with a long and wide snout. For reference, one of the largest skulls of the other giant crocodylomorph Deinosuchus was placed at in length. In contrast, a lightly-built skull from a juvenile Sarcosuchus only measures in length and bears a long and a wide snout. This indicates a snout length/cranial length ratio of 0.77 in adults while it is 0.74 in juveniles. The orbit, which is telescoped and angled dorsally (to the top), is only slightly smaller than the subtriangular supratemporal fossae (large openings in bone).