| Carcharodontosaurus | |
|---|---|
 | |
| ReconstructedC. saharicus skull,Science Museum of Minnesota | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Family: | †Carcharodontosauridae |
| Subfamily: | †Carcharodontosaurinae |
| Genus: | †Carcharodontosaurus Stromer,1931 |
| Type species | |
| †Carcharodontosaurus saharicus | |
| Other species | |
| Synonyms | |
List
| |
Carcharodontosaurus (/ˌkɑːrkəroʊˌdɒntoʊˈsɔːrəs/; "shark-toothed lizard") is agenus of largetheropoddinosaur that lived inNorthwest Africa from about 100 to 94 million years ago during theCenomanianstage of theCretaceous. Thetaxon was first described in 1925 by FrenchpaleontologistsCharles Depéret andJustin Savornin asMegalosaurus saharicus, based on twofossilteeth discovered in Algeria, which are now lost. A partialskeleton was discovered in Egypt as early as 1914 by crews of German paleontologistErnst Stromer, although he did not report the find until 1931. Based on this specimen, together with the teeth previously described by Depéret and Savornin, Stromer established the genusCarcharodontosaurus and itstype species (species a genus in named for)C. saharicus. Although the Egyptian skeleton was destroyed duringWorld War II, it was subsequently redescribed as theholotype (name-bearing) specimen of a distinctcarcharodontosaurid genus,Tameryraptor. In 1995, a large incompleteskull attributed toC. saharicus was discovered in theKem Kem Beds of Morocco, which was officially proposed as theneotype (replacement holotype) in 2007. In the same year, fossils unearthed from theEchkar Formation of Niger were described and named as another species,C. iguidensis, though this taxon might belong to a different genus.
The type species reaching around 12 m (39 ft) in length and approximately 5–7 metric tons (5.5–7.7 short tons) in body mass,Carcharodontosaurus is one of the largest theropod dinosaurs known. It had a large, lightly builtskull with a triangularrostrum (front of skull). Itsjaws were lined with sharp, recurved, serrated teeth that bear striking resemblances to those of thegreat white shark (genusCarcharodon), the inspiration for the name. Though giant, its cranium was made lighter by greatly expandedfossae (depressions in bone) andfenestrae (holes in the skull), but this made the cranium more fragile thantyrannosaurids'. Studies of thebite force and tooth anatomy ofCarcharodontosaurus have found it to have relatively low bite force compared to other large theropods. Despite the limited postcranial material known, is thought to have had smallforelimbs, powerfulhindlimbs, and a longtail that provided balance. Many gigantic theropods are known from North Africa during this period, including both species ofCarcharodontosaurus as well as thespinosauridSpinosaurus and the possibleceratosaurDeltadromeus. North Africa at the time was blanketed inmangrove forests andwetlands, creating a hotspot offish,crocodyliforms, andpterosaur diversity.
In 1924, two teeth ofCarcharodontosaurus were unearthed from wall cuts in differentfoggaras nearTimimoun,French Algeria. These sediments came from theCretaceous-aged[1]Continental intercalaire Formation.[2] The fossils were taken to the governor of Timimoun, Captain Burté, who gave them to French paleontologistCharles Depéret later that year. In 1925, Depéret and his colleagueJustin Savornindescribed the teeth as coming from a new species oftheropod dinosaur,Megalosaurus saharicus. These were the first fossils of theropods to be described from the region. Thespecific namesaharicus refers to theSahara Desert where the teeth had been found.[3] Two years later, Depéret and Savornin reassigned the same teeth under the nameM. (Dryptosaurus) saharicus, thereby placing the species in asubgenus.[2] By accident, another species ofMegalosaurus, M. africanus, was named by German paleontologistFriedrich von Huene based on the same teeth.[4] It is therefore implied that it is ajunior synonym ofM. saharicus.[5] The two original teeth described by Depéret and Savornin have since been reported as lost, being possibly kept in a collection in Algeria,Paris, orLyon, and lack distinguishing characteristics from othercarcharodontosaurids.[6] Moreover, the genusMegalosaurus is known to have historically been awastebasket taxon that included several species assigned without justification, the only currently recognised species beingM. bucklandii.[7] Later authors mentioned additional fossils from other provinces of Algeria that could belong toCarcharodontosaurus.[1][8]
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However, a partial skeleton later assigned toC. saharicus was first found in marls nearAin Gedid, Egypt, in early April 1914 byAustro-Hungarian paleontologistRichard Markgraf. Marls from this region derive from theCenomanian-agedBahariya Formation, one of many Cretaceous-aged sites ofNorth Africa.[9][10][11] In this formation, Markgraf did extensive collecting of dinosaur skeletons for his employer, German paleontologistErnst Stromer of thePaläontologisches Museum München (Bavarian State Collection of Paleontology).[9] Due topolitical tensions between theGerman Empire and thenBritish-owned Egypt, this skeleton, since numbered as SNSB-BSPG 1922 X 46, took years to get to Germany. It was not until 1922 that they were transported overseas toMunich,[12] where they were described by Stromer in 1931.[9]
Stromer recognized that the skeleton's teeth matched the characteristic dentition of those described by Depéret and Savornin, which led to Stromer conserving the species namesaharicus. However, he found it necessary to erect a new genus for this species,Carcharodontosaurus, for their similarities, in sharpness and serrations, to the teeth of thegreat white shark (Carcharodon carcharias).[9] The genus nameCarcharodontosaurus is therefore derived fromAncient Greek κάρχαρος (kárkharos), meaning "sharp, jagged", ὀδούς (odoús), meaning "tooth", and σαῦρος (saûros), meaning "lizard", and thus, "sharp-toothed lizard".[13] In his 1931 and 1934 descriptions, Stromer designates the smaller of the two teeth originally described by Depéret and Savornin as thetype specimen (name-bearing specimen) of thetaxon.[9][14] Thus, this tooth, although lost, must be considered as thelectotype (a later selected type specimen) ofC. saharicus.[15]World War II broke out in 1939, leading SNSB-BSPG 1922 X 46 and other material from Bahariya to be destroyed during aBritish bombing raid on Munich during the night of April 24/25, 1944.[16][17] Anendocast (cast of the interior of thebraincase) was made and survived the war, being the only remaining relic of the specimen.[18]
However in 2025, this specimen was redescribed as the holotype of a distinct carcharodontosaurid genus,Tameryraptor.[15] Following World War II, few major discoveries ofCarcharodontosaurus were made. Dozens of isolated teeth and bones were referred toCarcharodontosaurus from sites across North Africa including in Morocco, Tunisia, Algeria, and Niger, as it was the only carcharodontosaurid known from the region at the time. This led many fossils of carcharodontosaurids found during French geologic expeditions to North Africa to be assigned toCarcharodontosaurus based on little information[8][19] and traits now found in other genera.[5] This is especially true for isolated teeth, which were believed to bediagnostic for the genus until later research,[15][6] with a 2012 study by American researcher Matthew Carrano and colleagues stated that all isolatedCarcharodontosaurus teeth from the North Africa could only be considered indeterminate carcharodontosaurid teeth due to the presence of other carcharodontosaurid genera in the region.[5] Additionally, very little overlap exists between theC. saharicus neotype and the fossils found on these expeditions, exacerbating this issue.[20][21] In 1960, French paleontologistAlbert-Félix de Lapparent assigned teeth and bones from outcrops of the Continental intercalaire, Echkar Formation, and Irhazer Shale in North Africa toCarcharodontosaurus,[8] however they were assigned to the genus without detailed taxonomic discussion or reasoning.[5][15] In 1976, apostorbital (skull bone forming right side of orbit) and several postcranial remains assigned to the genus were found in theElrhaz Formation of northern Niger. French paleontologistPhilippe Taquet noted that the postorbital was similar to that ofAcrocanthosaurus, another carcharodontosaurid, suggesting it may be fromCarcharodontosaurus[22] however the postcranial fossils could belong to a different taxon.[15] Some of the fossils were misidentified, such an isolatedpedal phalanx (toe bone) from the Echkar Formation was assigned toCarcharodontosaurus by Lapparent (1960), but it likely is from a spinosaurid instead,[23] and severalcaudal (tail) vertebrae that may belong to asauropod.[15] Teeth and a caudal vertebra from theChenini Formation of southernTunisia have been assigned toCarcharodontosaurus.[24] Though, these fossils are now labeled Carcharodontosauridae indet.[25] Additionally, from the Gara Samani Formation, previously a part of the Continental intercalaire, have been identified asCarcharodontosaurus teeth, however they may belong to abelisaurids instead.[26]
Few discoveries ofCarcharodontosaurus attributed material were made until 1995 when American paleontologistPaul Sereno found an incompleteskull during an expedition embarked on by theUniversity of Chicago. This skull was found in the Cenomanian-aged rocks of theLower Douira Formation, Kem Kem Beds, inErrachidia, southeastern Morocco.[10] The presence ofCarcharodontosaurus in this formation was first suggested in 1954 by French palaeontologistRené Lavocat on the basis on fragmentary fossils.[19] The skull, since catalogued as SGM-Din 1 at theMinistry of Energy, Mines and Environment inRabat, Morocco, was first taken to the University of Chicago, where it was initially described in 1996 by Sereno and colleagues inScience.[10] In 2007, SGM-Din 1 was officially proposed as theneotype (replacement type specimen) ofC. saharicus due to the loss of the lectotype teeth and the similar age and geographic location to previously noted material.[6] Several other fossils ofC. saharicus have been unearthed from the Kem Kem Beds, such asdentary (lower jaw) fragments, twocervical (neck)vertebrae, and many teeth.[27][21][28][29]
Sereno and colleagues also assigned a multitude of cervical vertebrae described as thespinosauridsSigilmassasaurus and "Spinosaurus B" toC. saharicus, reasoning that stout cervicals would be needed to carry the skulls of carcharodontosaurids.[6][10] Later research proved otherwise, with the vertebrae being assigned toSpinosaurus aegyptiacus.[30] In a 2016 study, it was suggested that the neotype ofC. saharicus was similar to but distinct from the skeleton described by Stromer in the morphology of themaxillary (upper jaw bone)interdental plates.[31] This conclusion was partially supported by the paper describingTameryraptor, which noted several major differences between the MoroccanCarcharodontosaurus and the material described by Stromer. Because the neotype proposal was in accordance with theICZN article 75.3 and 75.4, the describers ofTameryraptor agreed that SGM-Din 1 is a valid neotype.[15]
In 2007, another species ofCarcharodontosaurus, C. iguidensis, was described by American paleontologistsSteve Brusatte and Paul Sereno. Fossils ofC. iguidensis had been uncovered during an expedition to theEchkar Formation of Iguidi, Niger, with a partial maxilla (MNN IGU2) being designated the holotype. The species nameiguidensis is after Iguidi, where the fossils were unearthed. Several other remains such as a braincase (part of skull surrounding brain), alacrimal (skull bone in front oforbit), a dentary, a cervical vertebra, and a collection of teeth were assigned toC. iguidensis based on size and supposed similarities to otherCarcharodontosaurus bones.[6] However, a 2016 paper by Italian researchers Alfio Alessandro Chiarenza andAndrea Cau identified the non-holotypic material ofC. iguidensis as belonging toSigilmassasaurus (later assigned toSpinosaurus sp.)[32] and a non-carcharodontosaurine, and therefore chose to limitC. iguidensis to the holotype pending future research.[31] This conclusion has been supported byphylogenetic analyses (a study of the evolutionary relationships between taxa), with several finding the holotype and referred material ofC. iguidensis as belonging to different taxa.[21][15] A 2025abstract presented by British paleontologist Charlie Scherer and colleagues at theSociety of Vertebrate Paleontology annual meeting stated thatC. iguidensis is from a distinct genus of carcharodontosaurid due to anatomical, phylogenetic, andbiogeographic differences withC. saharicus. The authors went on to state that they would be establishing a new genus forC. iguidensis.[33]
C. saharicus
C. iguidensis
Possible specimensIn 2013, another genus and species of carcharodontosaurid,Sauroniops pachytholus, was named by Andrea Cau and colleagues based on a singlefrontal (bone at front and top of skull),[34] though more material may be referrable to the taxon.[21]Sauroniops' validity has been questioned by several papers, with some stating that it isdubious (a species lacking diagnostic features)[15] or a synonym ofC. saharicus.[35] This proposed synonymy has been disputed by others.[31][21][36][20] Furthermore, several remains belonging to an unnamed carcharodontosaurid distinct fromCarcharodontosaurus, possibly the same asSauroniops, were described by Paterna and Cau (2022).[20][21] In 2015, a largeneural arch (projection of bone at the top of a vertebra) of a dorsal vertebra from the Kem Kem Beds was informally described as belonging to a new genus and species ofmegaraptoran or carcharodontosaurid dubbed "Osteoporosia gigantea". This specimen is owned by the head of a Polish theme park chain who described it as belonging to a 15 metres (49 ft) long carnosaur similar toMapusaurus andCarcharodontosaurus.[37] However, it was much smaller than proposed and may belong toC. saharicus orSauroniops based on its carcharodontosaurid traits and origin.[38] The South American genusGiganotosaurus was synonymized withCarcharodontosaurus in 1998 by Brazilian author Silvério Domingues Figueiredo[39] and in 2010 by American paleontologistGregory S. Paul,[40] but no authors have since followed this assessment.[41][6]
Stromer hypothesized thatC. saharicus was around the same size as thetyrannosauridGorgosaurus, which placed it at around 8–9 metres (26–30 ft) long, based on his specimen SNSB-BSPG 1922 X 46 (nowTameryraptor).[9] This individual was around 15% smaller than the neotype.[53] The latter was estimated to be 12–12.5 metres (39–41 ft) in length and approximately 5–7 metric tons (5.5–7.7 short tons) in body mass.[54][40][55][56] This makesCarcharodontosaurus saharicus one of the largest known theropod dinosaurs and one of the largest terrestrial carnivores.[41][40]C. iguidensis was much smaller, only reaching 10 metres (33 ft) in length and 4 metric tons (4.4 short tons) in body mass.[40]
Debate over what was the largest theropod dinosaur has ensued since the mid-1990s,[57] with different researchers arguing thatTyrannosaurus,[58]Carcharodontosaurus,[10]Giganotosaurus,[59] orSpinosaurus[60] was the largest theropod.[23] In 1996, Paul Sereno and colleagues estimated the skull ofC. saharicus to be 1.60 metres (5 ft), similar in size to that ofGiganotosaurus and possibly longer than that of theTyrannosaurus specimen "Sue". In an interview for a 1995 article entitled "new beast usurpsT. rex as king carnivore", Sereno noted that these newly discovered theropods from South America and Africa competed withTyrannosaurus as the largest predators, and would help in the understanding of Late Cretaceous dinosaur faunas, which had otherwise been very "North America-centric".[61] A later study by American paleontologist Matthew Carrano and colleagues in 2012 estimated the skull length ofC. saharicus to be 1.42 metres (5 ft) long, still slightly longer than that of the largestTyrannosaurus individuals.[62] In 2010, Gregory S. Paul suggested that the skulls of carcharodontosaurs had been reconstructed as too long in general.[63] In a 1997 interview, Argentine paleontologistRodolfo Coria estimatedGiganotosaurus to have been 13.7 to 14.3 metres (45 to 47 ft) long and weighing 8–10 metric tons (8.8–11.0 short tons) based on new material, larger thanCarcharodontosaurus. 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".[64] In 2007, Canadian researcher François Therrien and American researcher Donald M. Henderson found thatGiganotosaurus would have approached 13 metres (43 ft) in length and 13.8 t (15.2 short tons) in weight, whileCarcharodontosaurus would have approached 13.3 metres (44 ft) in length and 15.1 t (16.6 short tons) in weight (surpassingTyrannosaurus).[65]
The neotype skull ofC. saharicus would measure 1.6 metres (5.2 ft) when complete, around the same size as the largestTyrannosaurus skulls. No skulls of the genus preservepremaxillae, 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 likeMapusaurus andGiganotosaurus. Its skull was lighter than that of tyrannosaurids, with theantorbital fenestra composing over 30% of the total skull length as well as being surrounded byfossae in the maxillae,nasals (nose bone),jugals (cheekbone), andlacrimals (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 bykeratin sheaths, creating a horn-like structure as inCeratosaurus. A similar rugosity is found on the lacrimal which would also be lengthened by keratin, forming a similar element.[66][10]Carcharodontosaurus' skull has sculpted exteriors on its maxillae, which is a trait unique to the genus.C. iguidensis has antorbital fossae limited to the proximity of the maxillary fenestrae (a gap in the skull in the maxilla), crests running along the outer face of the maxillae, and aprocess along the anteriomedial section of the maxillae. Additionally, the braincase ofC. iguidensis has a deep fossa on the anterior end on the upper ridge of thelaterosphenoid. These traits are missing inC. saharicus, differentiating the two species.[6]
14 teeth sockets are present in each maxilla. Parts of the braincase are known though much of their morphology is the same asGiganotosaurus'. However,C. saharicus has a much more prominentnuchal crest, which overhangs the skull roof. The frontal bones are firmly fused, a characteristic evident in most theropods.[67] The jugals are broad and triangle-shaped. Thelower jaw articulation was placed farther back behind theoccipital condyle (where the neck is attached to the skull) compared to other theropods.[10] Two dentary (lower jaw bone) fragments which were assigned toC. saharicus by Ibrahim and colleagues in 2020 have deep and expandedalveoli (tooth sockets), traits found in other large theropods.[27][29] If likeTyrannotitan andGiganotosaurus, the dentary would have 16 alveoli (tooth sockets).[68]
Estimations of the tooth count ofCarcharodontosaurus vary, but a recent estimate of 30 dentary, 8 premaxillary, and 24 maxillary teeth for a total of 62 teeth was made.[69]Carcharodontosaurus teeth are some of the largest of any dinosaur group, with the lectotype maxillary tooth being 6.5 centimetres (2.6 in) tall, 1.5 centimetres (0.59 in) thick, and 3.2 centimetres (1.3 in) wide.[3] However, they are extremely thin, with most being under or around a centimetre thick. Serrations are numerous on the anterior and posterior margins, with over 18 to 20 serrations per centimetre of edge inC. saharicus and up to 32 per centimetre inC. iguidensis.[6][9] Its teeth are straight, laterally flattened, and spindle-shaped in cross-section. However, dentition towards the back of the mouth became more recurved than those in the maxilla. The posterior margin of thesecrowns are recurved and convex at its termination. Bowedenamel wrinkles are present on both dorsoventral sides of the crowns. These wrinkles curve towards the marginal serrations, composing a band-shape along the ends.[10][68]Carcharodontosaurus andGiganotosaurus have some of the most exaggerated enamel wrinkles of any theropod, especially on parts of the teeth near the serrations.Carcharodontosaurus is unique amongst most theropods in that it has enamel wrinkles on teeth throughout the upper jaw, not just on the broadest teeth like inGiganotosaurus.[70]
In 2001, Canadian paleontologist Hans C. E. Larsson published a description of theinner ear andendocranium ofC. saharicus. The brain ofCarcharodontosaurus is made up of three main sections: theforebrain, the anteriormost section, themidbrain, the middle section, and thehindbrain, 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-degreeangle with the midbrain. Overall, the brain ofC. saharicus would have been similar to that of a related dinosaur,Allosaurus fragilis. Larsson found that the ratio of thecerebrum to the volume of the brain overall inCarcharodontosaurus was typical for a non-avian reptile.Carcharodontosaurus also had a largeoptic nerve.[71]
The threesemicircular canals of the inner ear ofCarcharodontosaurus saharicus—when viewed from the side—had a subtriangular outline. This subtriangular inner-ear configuration is present inAllosaurus,lizards, andturtles, but not inbirds. The semi-"circular" canals themselves were very linear, which explains the pointed silhouette. In life, thefloccular lobe of the brain would have projected into the area surrounded by the semicircular canals, just like in theropods and pterosaurs.[71]
Few postcranial elements are confidently known fromCarcharodontosaurus, though many isolated bones from the Sahara have been assigned to the genus without detailed study.[6][30][22][8] However, the description of other carcharodontosaurids from North Africa such asTameryraptor andSauroniops has put into question the referral of carcharodontosaurid remains that lack overlap with theC. saharicus neotype.[15][20] Like other carcharodontosaurids, it was robust with smallforelimbs, an elongatedtail, and short neck. A single cervical vertebra was assigned to the genus by Canadian researcherDale A. Russell in 1996.[72] This cervical vertebra is stout andopisthocoelus (concave posterior ends).[73][68] Its preserved length is 148 millimetres (5.8 in). As inGiganotosaurus, the vertebra is topped by a lowneural spine (a dorsal projection of bone forming a spine) joined with sturdytransverse processes (projections of bone coming out of the sides of the centrum) which hung over thepleurocoels (shallow depressions on the sides of centra), which would containpneumatic air sacs to lighten the vertebrae. The centrum however lacks the keels observed in other carcharodontosaurids, possibly due to it being an anterior cervical vertebra.[74] 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 ofAcrocanthosaurus.[21]
Carcharodontosaurus is the type genus of the family Carcharodontosauridae and subfamily Carcharodontosaurinae. This subfamily containsCarcharodontosaurus itself as well as the other carcharodontosaurinesGiganotosaurus, Mapusaurus,Meraxes, andTyrannotitan; however, these genera make up an independent tribe: Giganotosaurini. Carcharodontosauridae was a clade created by Stromer forCarcharodontosaurus andBahariasaurus, though the name remained unused until the recognition of other members of the group in the late 20th century. He noted the likeness ofCarcharodontosaurus bones to the American theropodsAllosaurus andTyrannosaurus, leading him to consider the family part of Theropoda.[75][9] From the 1950s to the 1980s,Carcharodontosaurus was classified as a member ofMegalosauridae, another family of carnivorous theropods, alongside theropods likeAntrodemus/Allosaurus,Megalosaurus, andEustreptospondylus.[76]
In a 1995 paper, German researcher Oliver Rauhut analyzed the systematics ofCarcharodontosaurus—though this was based on the material now referred toTameryraptor—andBahariasaurus. Rauhut theorized thatCarcharodontosaurus andBahariasaurus were the only two named members of Carcharodontosauridae, but that the family may have originated in Tanzania.[77] This was based on"Allosaurus"tendagurensis and "Megalosaurus"ingens, which are two theropods known from fragmentary remains from theLate JurassicTendaguru Formation.[78][79] However, later studies have not supported these conclusions, withBahariasaurus being suggested to be aceratosaur,[21] "A."tendagurensis being an indeterminatetetanuran,[80][79][81] and"M." ingens possibly being a species ofTorvosaurus.[82][83]
Paul Sereno's description ofCarcharodontosaurus 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 toCarcharodontosaurus thanAllosaurus orSinraptor by the American paleontologistThomas R. Holtz and colleagues in 2004.[84]Carcharodontosaurus is less well-known than most other carcharodontosaurids, withMeraxes andGiganotosaurus represented by nearly complete skeletons.[85][86] Carcharodontosaurians have been recognized from theLate Jurassic to the Mid-Cretaceous of every continent except Antarctica.[41][87][10][88]
In the phylogenetic analyses of their 2025 paper, Kellermann, Cuesta & Rauhut recoveredC. iguidensis as a non-carcharodontosaurine member of the Carcharodontosauridae outside the genusCarcharodontosaurus, suggesting that this species belongs to a different genus.[15] Similar results were recovered by Cau & Paterna in their analysis of large Cretaceous theropods from Africa, who also argued for the removal ofC. iguidensis from the genus.[21]
The 2025 analyses of Kellermann, Cuesta & Rauhut found support for asister taxon relationship of carcharodontosaurids andmetriacanthosaurids, which the authors named as a new clade,Carcharodontosauriformes. The results of their analysis using mergedOTUs (operational taxonomic units; a group of organisms under phylogenetic study) are displayed in thecladogram (a graphical depiction of the results of a phylogenetic study) below:[15]
| Carcharodontosauriformes |
| ||||||||||||||||||||||||||||||||||||||||||
Argentine paleontologists Rodolfo Coria andLeonardo Salgado suggested that theconvergent evolution of gigantism in theropods could have been linked to common conditions in their environments orecosystems.[86] 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 Cretaceousperiod.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.[89][10] Previously, it was thought that the Cretaceous world wasbiogeographically separated, with the northern continents being dominated by tyrannosaurids, South America by abelisaurids, and Africa by carcharodontosaurids.[90] The subfamily Carcharodontosaurinae, in whichCarcharodontosaurus belongs, appears to have been restricted to the southern continent ofGondwana (formed by South America and Africa), where they were probably theapex predators.[84] The South American tribe Giganotosaurini may have been separated from their African relatives throughvicariance, when Gondwana broke up during theAptian–Albian ages of the Early Cretaceous.[91]
A biomechanical analysis ofCarcharodontosaurus' lifting capabilities was conducted by American paleontologistsDonald Henderson andRobert Nicholls in 2015. The authors used 3D models of the animal as well as a subadultsauropodLimaysaurus, which although not found alongsideCarcharodontosaurus, is similar to therebbachisaurids of the Kem Kem Beds. The models included the size of thelungs and other pneumatic structures of the two, fostering an accurate weight simulation of the scenario. Henderson & Nicholls' study found that an adultC. saharicus could hold a maximum of 424 kg (935 lb), half the weight of an adultLimaysaurus. However, twoC. saharicus adults could together lift as much as 850 kilograms (1,870 lb).[54]
The dentition of allosauroids is distinct, with carcharodontosaurid teeth being uniquely thin and blade-like. However, their thin nature mean they likely could not sustain impact against hard surfaces like bone without potentially bending and snapping. This danger is exacerbated by the straight edges, slightly recurved tips, andsinusoidal shapes observed in their dentition. Despite these traits, the teeth are still much more robust than those of smaller theropods and due to their overall size could take more pressure.Carcharodontosaurus also had a high tooth replacement rate, meaning that damaged teeth could be replaced easily in contrast to extant bone-crushing mammals who spend much of their energy maintaining their teeth.[92][93] In a 2015 study on dinosaur tooth function, teeth ofCarcharodontosaurus, Tyrannosaurus, and a variety of other dinosaurs were analyzed by X-ray microscopy. The internal microstructures ofCarcharodontosaurus enamel were shown to have crackedenamel tufts near thedentinoenamel junction, a trait that may have made the teeth more damage resistant and crack shielding, similar to that of humans.[94] Evidence of bone-crunching bites is observed inAllosaurus, which would engage in ritual face-biting with other individuals and bite into the pelves ofStegosaurus as shown by bite marks.[95][96][97]
Bite forces ofCarcharodontosaurus as well as other giant theropods includingAcrocanthosaurus andTyrannosaurus have been analyzed. Studies reported that carcharodontosaurids had much lower bite forces thanTyrannosaurus despite being in the same size class. The anterior bite force ofC. 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 ofTyrannosaurus, implying that it did not eat bones.[98][99] Finite element accounts of the skulls of theropods have also been taken, which further supported the idea thatCarcharodontosaurus ate softer food than tyrannosaurids. Great amounts of stress were recovered in the posterior part of the cranium near the quadrate inCarcharodontosaurus, Spinosaurus, andAcrocanthosaurus. 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 andSuchomimus experienced even greater values of stress meaning that they could only consume light, small prey instead of larger items, which the stronger skull ofCarcharodontosaurus could bite while sustaining the stress.[100]
Isotopic analyses of the teeth ofC. saharicus have found δ18O values that are higher than that of the contemporarySpinosaurus, suggesting the latter pursued semi-aquatic habits whereasCarcharodontosaurus was more terrestrial.[101] This is further supported by the taphonomy ofC. saharicus teeth, which are more often found in land terrains than aquatic ones.[69]Carcharodontosaurus was also ahomeotherm with anendotherm-likethermophysiology as inferred by these isotopes meaning that most of its oxygen was accumulated by drinking water rather than being in it.[102][103]
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. InCarcharodontosaurus,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 theligamentum suborbitale, a thin ligament in birds that forms the ventrolateral (bottom-side) wall of the orbit.[104] Most of the theropods with split orbits also have bony projections which overhang the orbit dorsally, such as horns inCarnotaurus and a bony shelf inCarcharodontosaurus. In his study, Chure recounted the idea that the horns ofCarnotaurus were used for "head-butting fights"[105] and suggested that theropods with bony shelves above their orbits, likeCarcharodontosaurus, did the same. Chure went on to suggest that the orbit size may indicateniche partitioning, with large-headed theropods likeCarcharodontosaurus beingdiurnal whereas smaller forms likeStenonychosaurus werenocturnal orcrepuscular.[104]
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A 2006 study by American biologist Kent Stevens analyzed thebinocular vision capabilities of the allosauroidsCarcharodontosaurus andAllosaurus as well as severalcoelurosaurs includingTyrannosaurus andStenonychosaurus. By applyingmodified perimetry to models of these dinosaurs' heads, Stevens deduced that the binocular vision ofCarcharodontosaurus was limited, a side effect of its large, elongated rostrum. Its greatest degree of binocular vision was at higher elevations, suggesting thatCarcharodontosaurus 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 wereambush predators. They likely sensed prey viamotion parallax between prey and background, with a narrow binocular field of vision helping predators judge prey distances and time attacks.[106]
The neotype skull ofC. saharicus is one of many allosauroid individuals to preservepathologies, with signs of biting, infection, and breaks observed inAllosaurus andAcrocanthosaurus among others.[107][108] This skull bears a circular puncture wound in the nasal and an unusual bony projection coming from the nasal's antorbital rim.[108] A later study theorized that this was the result of craniofacial bites.[109]
Fossils ofCarcharodontosaurus are known from several Cretaceous-age sites across North Africa, similar to the ranges ofSpinosaurus andDeltadromeus.[27][10] North Africa during this period bordered theTethys Sea, which transformed the region into amangrove-dominated coastal environment filled with vasttidal flats andwaterways.[110][111] Isotopes fromCarcharodontosaurus andSpinosaurus fossils suggest that the Kem Kem Beds witnessed a temporarymonsoon season rather than constant rainfall, similar to modern conditions present insub-tropical andtropical environments inSoutheast Asia andSub-Saharan Africa.[101][112] These riverine deposits bore large fishes, including thesawskateOnchopristis,coelacanthAxelrodichthys, andbichirBawitius.[113][114] This led to an abundance of piscivorouscrocodyliformes evolving in response, such as the giantstomatosuchidStomatosuchus in Egypt and the generaElosuchus,Laganosuchus, andAegisuchus from Morocco.[115][116] Morocco also bore an abundance of pterosaurs likeSiroccopteryx andNicorhynchus.[117][118]
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.[119] 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.[120][8] It also coexisted with the sauropodRebbachisaurus which is found in the Kem Kem Beds.[121] Carcharodontosaurids are represented byC. saharicus andSauroniops in the Kem Kem Beds,Tameryraptor in the Bahariya Formation,Eocarcharia and potentiallyCarcharodontosaurus in the Elrhaz Formation, andC. iguidensis in the Echkar Formation.[6] A tooth found alongside the holotype of the sauropodParalititan was assigned to cf.Carcharodontosaurus by American paleontologist Joshua Smith and colleagues in 2001. This tooth was theorized to be found with theParalititan individual due toscavenging. These fossils were unearthed in a site in the Bahariya Formation, where all fossils ofCarcharodontosaurus were reassigned toTameryraptor,[15] however this tooth specifically has not received further attention.[122]
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