Carcharodontosaurus

Initial finds being at the top (Fig. 1)|alt=Archival photos of the lost original teeth of Carcharodontosaurus saharicus in side views. The lectotype tooth is at the top. In 1924, two teeth of Carcharodontosaurus were unearthed from wall cuts in different foggaras near Timimoun, French Algeria. These sediments came from the Cretaceous-aged Continental intercalaire Formation. The fossils were taken to the governor of Timimoun, Captain Burté, who gave them to French paleontologist Charles Depéret later that year. In 1925, Depéret and his colleague Justin Savornin described the teeth as coming from a new species of theropod dinosaur, Megalosaurus saharicus. These were the first fossils of theropods to be described from the region. The specific name saharicus refers to the Sahara Desert where the teeth had been found. Two years later, Depéret and Savornin reassigned the same teeth under the name M. (Dryptosaurus) saharicus, thereby placing the species in a subgenus. It is therefore implied that it is a junior synonym of M. saharicus. The two original teeth described by Depéret and Savornin have since been reported as lost, being possibly kept in a collection in Algeria, Paris, or Lyon, and lack distinguishing characteristics from other carcharodontosaurids. Moreover, the genus Megalosaurus is known to have historically been a wastebasket taxon that included several species assigned without justification, the only currently recognised species being M. bucklandii. Later authors mentioned additional fossils from other provinces of Algeria that could belong to Carcharodontosaurus. in 1931, now the holotype of Tameryraptor|alt=Archival photo of a partial theropod dinosaur skeleton mounted in profile view However, a partial skeleton later assigned to C. saharicus was first found in marls near Ain Gedid, Egypt, in early April 1914 by Austro-Hungarian paleontologist Richard Markgraf. Marls from this region derive from the Cenomanian-aged Bahariya Formation, one of many Cretaceous-aged sites of North Africa. In this formation, Markgraf did extensive collecting of dinosaur skeletons for his employer, German paleontologist Ernst Stromer of the Paläontologisches Museum München (Bavarian State Collection of Paleontology). In his 1931 and 1934 descriptions, Stromer designates the smaller of the two teeth originally described by Depéret and Savornin as the type specimen (name-bearing specimen) of the taxon. World War II broke out in 1939, leading SNSB-BSPG 1922 X 46 and other material from Bahariya to be destroyed during a British bombing raid on Munich during the night of April 24/25, 1944. An endocast (cast of the interior of the braincase) was made and survived the war, being the only remaining relic of the specimen. However in 2025, this specimen was redescribed as the holotype of a distinct carcharodontosaurid genus, Tameryraptor. however the postcranial fossils could belong to a different taxon. and several caudal (tail) vertebrae that may belong to a sauropod. though these fossils are now labeled Carcharodontosauridae indet. Additionally, from the Gara Samani Formation, previously a part of the Continental intercalaire, have been identified as Carcharodontosaurus teeth, however they may belong to abelisaurids instead. Resurgent interest Few discoveries of Carcharodontosaurus attributed material were made until 1995 when American paleontologist Paul Sereno found an incomplete skull during an expedition embarked on by the University of Chicago. This skull was found in the Cenomanian-aged rocks of the Lower Douira Formation, Kem Kem Beds, in Errachidia, southeastern Morocco. The skull, since catalogued as SGM-Din 1 at the Ministry of Energy, Mines and Environment in Rabat, Morocco, was first taken to the University of Chicago, where it was initially described in 1996 by Sereno and colleagues in Science. Sereno and colleagues also assigned a multitude of cervical vertebrae described as the spinosaurids Sigilmassasaurus and "Spinosaurus B" to C. saharicus, reasoning that stout cervicals would be needed to carry the skulls of carcharodontosaurids. This conclusion was partially supported by the paper describing Tameryraptor, which noted several major differences between the Moroccan Carcharodontosaurus and the material described by Stromer. Because the neotype proposal was in accordance with the ICZN article 75.3 and 75.4, the describers of Tameryraptor agreed that SGM-Din 1 is a valid neotype.In 2013, another genus and species of carcharodontosaurid, Sauroniops pachytholus, was named by Andrea Cau and colleagues based on a single frontal (bone at front and top of skull), though more material may be referrable to the taxon. Furthermore, several remains belonging to an unnamed carcharodontosaurid distinct from Carcharodontosaurus, possibly the same as Sauroniops, were described by Paterna and Cau (2022). However, it was much smaller than proposed and may belong to C. saharicus or Sauroniops based on its carcharodontosaurid traits and origin. The South American genus Giganotosaurus was synonymized with Carcharodontosaurus in 1998 by Brazilian author Silvério Domingues Figueiredo and in 2010 by American paleontologist Gregory S. Paul, but no authors have since followed this assessment. However, it lacks the traits of carcharodontosaurid teeth and instead is more similar to that of other allosauroids. • In a 1970 study, teeth deriving from the Gokwe Formation of Zimbabwe were described as being similar to those of Carcharodontosaurus. However, later studies have found these teeth to be indeterminate. • Teeth from the Alcantara Formation and the Itapecuru Group of Brazil have placed in Carcharodontosaurus, but this has been disputed based on its geographic origin and lack of diagnostic features. • Several vertebral (base of vertebrae), a tarsal (bone in the heel), a metatarsal (foot/ankle bone), and a pedal phalanx from Wadi Milk Formation of Sudan were compared Carcharodontosaurus, but were now considered to be indeterminate carcharodontosaurids, some of which are similar to the genus. • Fossils from the Campanian Quseir Formation of western Egypt have been tentatively assigned to Spinosaurus and Carcharodontosaurus, but these specimens were never described in detail and thus classified as indeterminate. ==Description==

Size , C. saharicus in orange, far right Stromer hypothesized that C. saharicus was around the same size as the tyrannosaurid Gorgosaurus, which placed it at around long, based on his specimen SNSB-BSPG 1922 X 46 (now Tameryraptor). This makes Carcharodontosaurus saharicus one of the largest known theropod dinosaurs and one of the largest terrestrial carnivores. with different researchers arguing that Tyrannosaurus, Carcharodontosaurus, or Spinosaurus was the largest theropod. A later study by American paleontologist Matthew Carrano and colleagues in 2012 estimated the skull length of C. saharicus to be long, still slightly longer than that of the largest Tyrannosaurus individuals. In 2010, Gregory S. Paul suggested that the skulls of carcharodontosaurs had been reconstructed as too long in general. In a 1997 interview, Argentine paleontologist Rodolfo Coria estimated Giganotosaurus to have been long and weighing based on new material, larger than Carcharodontosaurus. Sereno countered that it would be difficult to determine a size range for a species based on few, incomplete specimens, and both paleontologists agreed that other aspects of these dinosaurs were more important than settling the "size contest". In 2007, Canadian researcher François Therrien and American researcher Donald M. Henderson found that Giganotosaurus would have approached in length and in weight, while Carcharodontosaurus would have approached in length and in weight (surpassing Tyrannosaurus). Skull Cranium and teeth The neotype skull of C. saharicus would measure when complete, around the same size as the largest Tyrannosaurus skulls. No skulls of the genus preserve premaxillae, complete posterior skull regions, or mandibles. Skulls of carcharodontosaurids tend to be more slender and lightly built than those of later tyrannosaurids, which have robust builds and adaptations for crushing. The neotype cranium tapers towards the front in side view creating a triangular outline. This is similar to that of other carcharodontosaurids like Mapusaurus and Giganotosaurus. Its skull was lighter than that of tyrannosaurids, with the antorbital fenestra composing over 30% of the total skull length as well as being surrounded by in the maxillae, nasals (nose bone), jugals (cheekbone), and lacrimals (front orbit bone). Akin to other genera, its nasal is elongated and its exposed side is covered in a rugose surface. These bumps were likely extended by keratin sheaths, creating a horn-like structure as in Ceratosaurus. A similar rugosity is found on the lacrimal which would also be lengthened by keratin, forming a similar element. The jugals are broad and triangle-shaped. The lower jaw articulation was placed farther back behind the occipital condyle (where the neck is attached to the skull) compared to other theropods. Estimations of the tooth count of Carcharodontosaurus vary, but a recent estimate of 30 dentary, 8 premaxillary, and 24 maxillary teeth for a total of 62 teeth was made. Carcharodontosaurus teeth are some of the largest of any dinosaur group, with the lectotype maxillary tooth being tall, thick, and wide. Brain and inner ear In 2001, Canadian paleontologist Hans C. E. Larsson published a description of the inner ear and endocranium of C. saharicus. The brain of Carcharodontosaurus is made up of three main sections: the forebrain, the anteriormost section, the midbrain, the middle section, and the hindbrain, the posteriormost section. The midbrain is angled downwards at a 45-degree angle and towards the rear of the animal. This is followed by the hindbrain, which is roughly parallel to the forebrain and forms a roughly 40-degree angle with the midbrain. Overall, the brain of C. saharicus would have been similar to that of a related dinosaur, Allosaurus fragilis. Larsson found that the ratio of the cerebrum to the volume of the brain overall in Carcharodontosaurus was typical for a non-avian reptile. Carcharodontosaurus also had a large optic nerve. The three semicircular canals of the inner ear of Carcharodontosaurus saharicus—when viewed from the side—had a subtriangular outline. This subtriangular inner-ear configuration is present in Allosaurus, lizards, and turtles, but not in birds. The semi-"circular" canals themselves were very linear, which explains the pointed silhouette. In life, the floccular lobe of the brain would have projected into the area surrounded by the semicircular canals, just like in theropods and pterosaurs. This cervical vertebra is stout and (concave posterior ends). Another incomplete cervical vertebra was tentatively referred to the genus by Cau and colleagues (2025) on the basis of its stratigraphic and geographic position. The vertebra is likely from the 4th to 6th position in the cervical column and shares general morphology, size, and proportions with cervicals of Acrocanthosaurus. ==Classification==

Systematics of C. saharicus|325x325px Carcharodontosaurus is the type genus of the family Carcharodontosauridae and subfamily Carcharodontosaurinae. This subfamily contains Carcharodontosaurus itself as well as the other carcharodontosaurines Giganotosaurus, Mapusaurus, Meraxes, and Tyrannotitan; however, these genera make up an independent tribe: Giganotosaurini. Carcharodontosauridae was a clade created by Stromer for Carcharodontosaurus and Bahariasaurus, though the name remained unused until the recognition of other members of the group in the late 20th century. He noted the likeness of Carcharodontosaurus bones to the American theropods Allosaurus and Tyrannosaurus, leading him to consider the family part of Theropoda. This was based on "Allosaurus" tendagurensis and "Megalosaurus" ingens, which are two theropods known from fragmentary remains from the Late Jurassic Tendaguru Formation. However, later studies have not supported these conclusions, with Bahariasaurus being suggested to be a ceratosaur, Paul Sereno's description of Carcharodontosaurus fossils in 1996 led to the realization of a transcontinental clade of carcharodontosaurids. As more carcharodontosaurids were discovered, their interrelationships became even clearer. The group was defined as all allosauroids closer to Carcharodontosaurus than Allosaurus or Sinraptor by the American paleontologist Thomas R. Holtz and colleagues in 2004. Carcharodontosaurus is less well-known than most other carcharodontosaurids, with Meraxes and Giganotosaurus represented by nearly complete skeletons. In the phylogenetic analyses of their 2025 paper, Kellermann, Cuesta & Rauhut recovered C. iguidensis as a non-carcharodontosaurine member of the Carcharodontosauridae outside the genus Carcharodontosaurus, suggesting that this species belongs to a different genus. The 2025 analyses of Kellermann, Cuesta & Rauhut found support for a sister taxon relationship of carcharodontosaurids and metriacanthosaurids, which the authors named as a new clade, Carcharodontosauriformes. The results of their analysis using merged OTUs (operational taxonomic units; a group of organisms under phylogenetic study) are displayed in the cladogram (a graphical depiction of the results of a phylogenetic study) below: Sereno and colleagues found that the presence of carcharodontosaurids in Africa (Carcharodontosaurus), North America (Acrocanthosaurus), and South America (Giganotosaurus), showed the group had a transcontinental distribution by the Early Cretaceous period. Dispersal routes between the northern and southern continents appear to have been severed by ocean barriers in the Late Cretaceous, which led to more distinct, provincial faunas, by preventing exchange. The subfamily Carcharodontosaurinae, in which Carcharodontosaurus belongs, appears to have been restricted to the southern continent of Gondwana (formed by South America and Africa), where they were probably the apex predators. ==Paleobiology==

Lifting capabilities A biomechanical analysis of Carcharodontosaurus lifting capabilities was conducted by American paleontologists Donald Henderson and Robert Nicholls in 2015. The authors used 3D models of the animal as well as a subadult sauropod Limaysaurus, which although not found alongside Carcharodontosaurus, is similar to the rebbachisaurids of the Kem Kem Beds. The models included the size of the lungs and other pneumatic structures of the two, fostering an accurate weight simulation of the scenario. Henderson & Nicholls' study found that an adult C. saharicus could hold a maximum of , half the weight of an adult Limaysaurus. However, two C. saharicus adults could together lift as much as . In a 2015 study on dinosaur tooth function, teeth of Carcharodontosaurus, Tyrannosaurus, and a variety of other dinosaurs were analyzed by X-ray microscopy. The internal microstructures of Carcharodontosaurus enamel were shown to have cracked enamel tufts near the dentinoenamel junction, a trait that may have made the teeth more damage resistant and crack shielding, similar to that of humans. Evidence of bone-crunching bites is observed in Allosaurus, which would engage in ritual face-biting with other individuals and bite into the pelves of Stegosaurus as shown by bite marks. Bite forces of Carcharodontosaurus as well as other giant theropods including Acrocanthosaurus and Tyrannosaurus have been analyzed. Studies reported that carcharodontosaurids had much lower bite forces than Tyrannosaurus despite being in the same size class. The anterior bite force of C. saharicus was estimated in a 2022 paper to be 11,312 newtons while the posterior bite force was 25,449 newtons. This is much lower than that of Tyrannosaurus, implying that it did not eat bones. Finite element accounts of the skulls of theropods have also been taken, which further supported the idea that Carcharodontosaurus ate softer food than tyrannosaurids. Great amounts of stress were recovered in the posterior part of the cranium near the quadrate in Carcharodontosaurus, Spinosaurus, and Acrocanthosaurus. The skulls of these theropods had higher relative stress quantities in opposition to that of smaller genera. This indicates that the crania of giant taxa (ex. Carcharodontosaurus) were unstable due to having large pneumatic structures to save weight instead of creating a firm build. However, Spinosaurus and Suchomimus experienced even greater values of stress meaning that they could only consume light, small prey instead of larger items, which the stronger skull of Carcharodontosaurus could bite while sustaining the stress. Isotopic analyses of the teeth of C. saharicus have found δ18O values that are higher than that of the contemporary Spinosaurus, suggesting the latter pursued semi-aquatic habits whereas Carcharodontosaurus was more terrestrial. This is further supported by the taphonomy of C. saharicus teeth, which are more often found in land terrains than aquatic ones. Orbit In many large-skulled theropods, the orbits bear unusual shapes and are nearly divided into dorsal and ventral sections. However, the purpose of this large, split orbit is unknown. In Carcharodontosaurus, Abelisaurus, and some other theropods, this is created by an anterior projection of the postorbital bone into the orbit. In 1998, American paleontologist Daniel Chure suggested that these projections were caused by the ligamentum suborbitale, a thin ligament in birds that forms the ventrolateral (bottom-side) wall of the orbit. and suggested that theropods with bony shelves above their orbits, like Carcharodontosaurus, did the same. Chure went on to suggest that the orbit size may indicate niche partitioning, with large-headed theropods like Carcharodontosaurus being diurnal whereas smaller forms like Stenonychosaurus were nocturnal or crepuscular. Vision A 2006 study by American biologist Kent Stevens analyzed the binocular vision capabilities of the allosauroids Carcharodontosaurus and Allosaurus as well as several coelurosaurs including Tyrannosaurus and Stenonychosaurus. By applying modified perimetry to models of these dinosaurs' heads, Stevens deduced that the binocular vision of Carcharodontosaurus was limited, a side effect of its large, elongated rostrum. Its greatest degree of binocular vision was at higher elevations, suggesting that Carcharodontosaurus may have habitually held its head at a downward 40° angle with its eyes facing up accordingly to achieve maximum binocular vision. The range of vision seen in these allosauroids is comparable to that of crocodiles, suggesting that they were ambush predators. They likely sensed prey via motion parallax between prey and background, with a narrow binocular field of vision helping predators judge prey distances and time attacks. Pathology The neotype skull of C. saharicus is one of many allosauroid individuals to preserve pathologies, with signs of biting, infection, and breaks observed in Allosaurus and Acrocanthosaurus among others. This skull bears a circular puncture wound in the nasal and an unusual bony projection coming from the nasal's antorbital rim. == Paleoenvironment ==

region and its outcrops Fossils of Carcharodontosaurus are known from several Cretaceous-age sites across North Africa, similar to the ranges of Spinosaurus and Deltadromeus. Isotopes from Carcharodontosaurus and Spinosaurus fossils suggest that the Kem Kem Beds witnessed a temporary monsoon season rather than constant rainfall, similar to modern conditions present in sub-tropical and tropical environments in Southeast Asia and Sub-Saharan Africa. These riverine deposits bore large fishes, including the sawskate Onchopristis, coelacanth Axelrodichthys, and bichir Bawitius. This led to an abundance of piscivorous crocodyliformes evolving in response, such as the giant stomatosuchid Stomatosuchus in Egypt and the genera Elosuchus, Laganosuchus, and Aegisuchus from Morocco. Morocco also bore an abundance of pterosaurs like Siroccopteryx and Nicorhynchus. The composition of the dinosaur fauna of these sites is an anomaly, as there are fewer herbivorous dinosaur species relative to carnivorous dinosaurs than usual. This indicates that there was niche partitioning between the different theropod clades, with spinosaurids consuming fish while other groups hunted herbivorous dinosaurs. Isotopic evidence supports this, which found greater quantities of sizable, terrestrial animals in the diets of carcharodontosaurids and ceratosaurs from both the Kem Kem Beds and Elrhaz Formation. Carcharodontosaurids are represented by C. saharicus and Sauroniops in the Kem Kem Beds, Tameryraptor in the Bahariya Formation, Eocarcharia and potentially Carcharodontosaurus in the Elrhaz Formation, and C. iguidensis in the Farak Formation, initially identified as the layers of the Echkar Formation. A tooth found alongside the holotype of the sauropod Paralititan was assigned to cf. Carcharodontosaurus by American paleontologist Joshua Smith and colleagues in 2001. This tooth was theorized to be found with the Paralititan individual due to scavenging. These fossils were unearthed in a site in the Bahariya Formation, where all fossils of Carcharodontosaurus were reassigned to Tameryraptor, ==References==