Otodus auriculatus
| Carcharocles auriculatus Temporal range: Late Eocene-Early Oligocene
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| Genus: | Disputed; †Otodus or †Carcharocles
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| Species: | †O. auriculatus
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| Disputed; Otodus auriculatus or Carcharocles auriculatus Jordan, 1923
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Carcharocles auriculatus[1] is a large extinct shark species of the family Otodontidae, closely related to the sharks of the genus Otodus, and also closely related to the later species megalodon. Its teeth are large, having coarse serrations on the cutting edge, and also with two large cusplets. The teeth can reach up to 130 mm, and belonged to a large "megatoothed" shark.
Assignment to the genus Carcharocles rather than Otodus
It is known that there is at least one genus in the family Otodontidae, that being Otodus. But the names and number of the genera in Otodontidae is controversial and the family's accepted phylogeny varies among paleontologists in different parts of the world. In the USA and Britain the most widespread genus name for otodontids with serrated teeth is Carcharocles, and the owners of unserrated ones Otodus. In countries of the former USSR, like Ukraine or Russia, all of these genera were attributed to Otodus, because scientists like Zhelezko and Kozlov[2] thought that the absence or presence of tooth serrations is not enough to place these sharks in different taxa.
Size
The tooth length of C.auriculatus is relatively large - from 25 to 114 mm.[1] However, it is smaller than that of megalodon and Carcharocles angustidens; the tooth length of C. megalodon is 38–178 mm and C. angustidens 25–117 mm.[1]
Distribution
Most C. auriculatus teeth come from South Carolina.[1] However, many Eocene shark teeth are known from Khouribga Plateau, in Morocco.[3]
Evolution
Carcharocles auriculatus is the most primitive known member of the genus Carcharocles.
Species list
- Cretolamna appendiculata
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- Carcharocles auriculatus
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Evolution of genera
The family of Otodontidae is well known and famous because of its last member - Megalodon. Yet, there were many other genera in this family, first appearing in the Cretaceous. The first one was Cretalamna,[4] one of the largest sharks in the Cretaceous. The teeth basal morphology was similar to the teeth of later Otodus. First, the crown was triangular. This feature helped the shark to bite harder, and this is the feature to which the otodontid evolution was leading for.[5] Second, there was a small protuberance on the labial side of the crown, which is also present in many other species of the family. But there was a feature, which limited the bite force, decreasing the area of the bite, the cusplets. The completely similar absolutely triangular unserrated (all the teeth of Cretalamna had no serrations, the cutting edge was smooth) cusplets were present in a later Otodus obliquus from Paleocene and Eocene. Otodus obliquus is the first large form of otodontid. The maximum size of the teeth was up to 100mm.