Cretodus
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| Cretodus Temporal range: | |
|---|---|
 | |
| C. crassidens teeth from the Turonian of Italy | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Division: | Selachii |
| Order: | Lamniformes |
| Family: | †Pseudoscapanorhynchidae |
| Genus: | †Cretodus Sokolov, 1965 |
| Type species | |
| †Cretodus crassidens Dixon, 1850 | |
| Species | |
| |
Cretodus is an extinct genus of large mackerel sharks belonging to the proposed family Pseudoscapanorhynchidae.[1] Cretodus lived during the Late Cretaceous, ranging from the Cenomanian[2] to the Coniacian[3] (approximately 100 to 89 million years ago). The genus is well-known from strata deposited in the Western Interior Seaway (North America),[1][2][3] and from the Late Cretaceous of Europe,[4] Africa, and possibly Asia.[citation needed] Cretodus is primarily represented in the fossil record by isolated teeth and vertebral centra, though a couple of associated dentitions and vertebral columns have been found.[1][4]
Dentition
Prior to 2017, Cretodus was mainly known from isolated teeth.[5] The discovery of a virtually complete skeleton suggests the genus possessed a body similar in form to the modern tiger shark, with a wide head that was equipped with powerful jaws, and a stout body.[4] The morphology of Cretodus' placoid scales and vertebral centra suggest a moderate swimming speed, less than that of the fast-cruising contemporaneous macropredatory shark, Cretoxyrhina.[4][1]
Size estimation is only reasonable for the few associated partial skeletons known. Shimada & Everhart (2019) reported an approximate total length of 5.15 m (16.9 ft) for the associated specimen of C. houghtonorum from Kansas which probably died at 22 years of age; they also suggested that the maximum total length of C. houghtonorum would have been 6.84 m (22.4 ft).[1] Amalfitano et al. (2022) reported an estimated total length of 6.6–7.8 m (22–26 ft) for a nearly complete specimen of C. crassidens from Italy which probably died at 23 years of age; they also fitted a van Bertalanffy growth model based on the growth record of this specimen, estimating the parameter of theoretical maximum total length (L∞) for C. crassidens at 9.55–11.28 m (31.3–37.0 ft).[4]
Cretodus teeth have lateral cusplets that are much smaller than the main cusp and well-separated from it, but connected by enamel on the labial face. The enamel surface is smooth, except near the base of the crown, where it forms vertical striae or costulae (grooves and ridges), a feature more prominent on the lingual face. The root is bilobate and has a massive shelf-like lingual root protuberance which diminishes in size in posterior positions.[4][6]
Growth
It is estimated that C. houghtonorum was about 1.18 m (3.9 ft) long at birth, became sexually mature at 10 to 15 years of age, and reached its maximum lifespan at 51 to 55 years of age.[1][4] C. crassidens was about 1.42 m (4.7 ft) long at birth, became sexually mature at 12 to 17 years of age, and reached its maximum life span at 64 years of age.[4]