Carcharodontosaurus

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Carcharodontosaurus
Temporal range: EarlyLate Cretaceous, 100–93Ma
Carcharodontosaurus skull cast, on display at the Royal Ontario Museum
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Theropoda
Clade: Carnosauria
Family: Carcharodontosauridae
Subfamily: Carcharodontosaurinae
Stromer, 1931
Genus: Carcharodontosaurus
Stromer, 1931
Type species
Megalosaurus saharicus
Depéret & Savornin, 1925
Species
  • C. saharicus
    (Depéret & Savornin, 1925)
  • C. iguidensis
    Brusatte & Sereno, 2007
Synonyms
  • Megalosaurus saharicus Depéret & Savornin, 1925
  • Megalosaurus africanus von Huene, 1956

Carcharodontosaurus /ˌkɑrkərɵˌdɒntɵˈsɔrəs/ is a genus of carnivorous carcharodontosaurid dinosaurs that existed between 100 and 93 million years ago, during the late Albian to early Cenomanian stages of the mid-Cretaceous Period. It is currently known to include two gigantic species, which were among the largest known predatory dinosaurs, as large or slightly bigger than the dinosaurs of the genera Tyrannosaurus and Giganotosaurus, but not as large as Spinosaurus.

The genus Carcharodontosaurus is named after the shark genus Carcharodon[1] (itself named from the Greek καρχαρο karcharo meaning "jagged" or "sharp" and οδοντο odonto meaning "teeth"), and σαυρος sauros, meaning "lizard" — "Carcharodon lizard".

Description

Life restoration of Carcharodontosaurus saharicus

Carcharodontosaurus includes some of the longest and heaviest known carnivorous dinosaurs, with various scientists proposing length estimates for the species C. saharicus ranging between 12 and 13 m (39 and 43 ft) and weight estimates between 6 and 15 metric tons.[2][3][4]

Carcharodontosaurus were carnivores, with enormous jaws and long, serrated teeth up to eight inches long. Paleontologists once thought that Carcharodontosaurus had the longest skulls of any of the theropod dinosaurs. However, the premaxilla and quadrate bones were missing from the original African skull, which led to misinterpretation of its actual size by researchers. A more modest length of 1.6 meters (5.2 ft) has now been proposed for C. saharicus, and the skull of C. iguidensis is reported to have been about the same size.[5] Currently, the largest known theropod skull belongs to another huge carcharodontosaurid dinosaur, the closely related Giganotosaurus (with skull length estimates up to 1.95 m) (6.3 ft).[6]

Brain and inner ear

In 2001, Hans C. E. Larsson published a description of the inner ear and endocranium of Carcharodontosaurus saharicus.[7] Starting from the portion of the brain closest to the tip of the animal's snout is the forebrain, which is followed by the midbrain. The midbrain is angled downwards at a 45 degree angle and towards the rear of the animal. This is followed by the hind brain, which is roughly parallel to the forebrain and forms a roughly 40 degree angle with the midbrain.[7] Overall, the brain of C. saharicus would have been similar to that of a related dinosaur, Allosaurus fragilis.[7] Larsson found that the ratio of the cerebrum to the volume of the brain overall in Carcharodontosaurus was typical for a non-avian reptile.[7] Carcharodontosaurus also had a large optic nerve.[7]

Size comparison of selected giant theropod dinosaurs, C. saharicus in violet

The three semicircular canals of the inner ear of Carcharodontosaurus saharicus, when viewed from the side, had a subtriangular outline.[7] This subtriangular inner ear configuration is present in Allosaurus, lizards, turtles, but not in birds.[7] The semi-"circular" canals themselves were actually very linear, which explains the pointed silhouette.[7] In life, the floccular lobe of the brain would have projected into the area surrounded by the semicircular canals, just like in other non-avian theropods, birds, and pterosaurs.[7]

Restored skull of SGM-DIN 1, the neotype of C. saharicus
Life restoration of C. saharicus.

Pathology

SGM-Din 1, a Carcharodontosaurus saharicus skull, has a circular puncture wound in the nasal and "an abnormal projection of bone on the antorbital rim".[8]

Discovery, etymology and taxonomic history

Carcharodontosaurus tooth

In 1924, two teeth were found in the Continental intercalaire of Algeria, showing what were at the time unique characteristics, this teeth were described by Depéret and Savornin (1925) as representing a new taxon, which they named Megalosaurus saharicus[9] and later referred by the same authors to the subgenus Dryptosaurus.[10] Some years later, paleontologist Ernst Stromer described the remains of a partial skull and skeleton from Cenomanian aged rocks in the Bahariya Formation of Egypt (Stromer, 1931),[1] originally excavated in 1914, the remains consisted on a partial skull, teeth, vertebrae, claw bones and assorted hip and leg bones.[1] The teeth in this new finding matched the characteristic of those described by Depéret and Savornin which lead Stromer to conserve the species name saharicus but found necessary to erect a new genus for this species, Carcharodontosaurus, for their strong resemblance to the teeth of Carcharodon (Great white shark).[1]

The fossils described by Stromer were destroyed in 1944 during World War II but a new more complete skull was found in the Kem Kem Formation of Morocco during an expedition lead by paleontologist Paul Sereno in 1995, not too far from the Algerian border and the locality where the teeth described by Depéret and Savornin (1925) were found, the teeth found with this new skull matched those described by Depéret and Savornin (1925) and Stromer (1931), the rest of the skull also matched that described by Stromer. This new skull was designated as the neotype by Brusatte and Sereno (2007) who also described a second species of Carcharodontosaurus, C. iguidensis from the Echkar Formation of Niger, differing from C. saharicus in aspects of the maxilla and braincase.[5]

References

  1. ^ a b c d Stromer, E. (1931). "Wirbeltiere-Reste der Baharijestufe (unterestes Canoman). Ein Skelett-Rest von Carcharodontosaurus nov. gen." Abhandlungen der Bayerischen Akademie der Wissenschaften, Mathematisch-naturwissenschaftliche Abteilung, 9(Neue Folge): 1–23.
  2. ^ Sereno, P. C.; Dutheil, D. B.; Iarochene, M.; Larsson, H. C. E.; Lyon, G. H.; Magwene, P. M.; Sidor, C. A.; Varricchio, D. J.; Wilson, J. A. (1996). "Predatory Dinosaurs from the Sahara and Late Cretaceous Faunal Differentiation". Science 272 (5264): 986–991. doi:10.1126/science.272.5264.986. PMID 8662584.  edit
  3. ^ Seebacher, F. (2001). "A New Method to Calculate Allometric Length-Mass Relationships of Dinosaurs". Journal of Vertebrate Paleontology 21: 51–52. doi:10.1671/0272-4634(2001)021[0051:ANMTCA]2.0.CO;2. ISSN 0272-4634.  edit
  4. ^ Therrien, F.; and Henderson, D.M. (2007). "My theropod is bigger than yours...or not: estimating body size from skull length in theropods". Journal of Vertebrate Paleontology 27 (1): 108–115. doi:10.1671/0272-4634(2007)27[108:MTIBTY]2.0.CO;2. ISSN 0272-4634. 
  5. ^ a b Brusatte, S.L. and Sereno, P.C. (2007). "A new species of Carcharodontosaurus (dinosauria: theropoda) from the Cenomanian of Niger and a revision of the genus." Journal of Vertebrate Paleontology, 27(4): .
  6. ^ Calvo, J.O., and Coria, R.A. (1998) "New specimen of Giganotosaurus carolinii (CORIA & SALGADO, 1995), supports it as the largest theropod ever found." Gaia, 15: 117–122.
  7. ^ a b c d e f g h i Larsson, H.C.E. 2001. Endocranial anatomy of Carcharodontosaurus saharicus (Theropoda: Allosauroidea) and its implications for theropod brain evolution. pp. 19–33. In: Mesozioc Vertebrate Life. Ed.s Tanke, D. H., Carpenter, K., Skrepnick, M. W. Indiana University Press.
  8. ^ "Acrocanthosauridae fam. nov.," in Molnar (2001). Pg. 342.
  9. ^ Deparet, C. and Savornin, J. (1925). "Sur la decouverte d'une faune de vertebres albiens a Timimoun (Sahara occidental)." Comptes Rendus, Academie du Sciences, Paris, 181: 1108-1111.
  10. ^ Deparet, C. and Savornin, J. (1927). "La faune de reptiles et de poisons albiens de Timimoun (Sahara algérien)." Bulletin de la société géologique de France, 27: 257-265.

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