Megaselachus

Megaselachus Temporal range: Early Miocene PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Division:	Selachii
Order:	Lamniformes
Family:	† Otodontidae
Genus:	† Megaselachus Glyckman, 1964
Type species
Megaselachus subauriculatus (Agassiz, 1839)
Other species
†?M. productus(Agassiz, 1838)
Synonyms
Carcharias subauriculatus(Agassiz, 1839) Megaselachus polygorus? (Glickman, 1964) Carcharodon subauriculatus(Agassiz, 1843)

Megaselachus is a possibly dubious extinct genus of otodontid shark. In the past, this particular genus has been used to house other otodontids, such as the famous megalodon. It is sometimes considered a subgenus of Otodus , or merged with other related genera such as Carcharocles . ^[1] The genus lived during the Miocene. Only a single species can be confidentially placed in the genus, Megaselachus subauriculatus. A aditional species, M. productus is now considered a possible synonym of Otodus megalodon .

Taxonomy

The Megaselachus is now considered a dubious name and problematic name. The holotype of M. subauriculatus is the MLP 12-3724,^{[ citation needed ]} that was named in 1839 by Louis Agassiz as Carcharias subauriculatus. ^[2] In 1843, Louis Agassiz realized that the teeth of this species were more similar to those of the Great White Shark (Carcharodon carcharias), than to the genus Carcharias as previously thought. He recombined as junior synonym of Carcharodon subauriculatus (now O. chubutensis) previously in same year.

In 1964, the paleontologist Glickman suggered a separate genus, the Megaselachus and inclued M. subauriculatus, M. megalodon and M. chubutensis in same genus. The M. productus was proposed in 1838, ^[3] and previously suported now as synonym of O. megalodon or O. chubutensis, but are in debate. New studies previously in 2000s, paleontologists started began to question the validity of this genus, assuming that the genus had no characteristics of its own that separated it from Otodus and Carcharocles.

Description

Megaselachus teeth are moderately narrow. They also have a heavily serrated crown. The labial side is convex with a prominent triangular neck, while the lingual side is concave. ^[4]

References

1. Shimada, Kenshu; Chandler, Richard E.; Lam, Otto Lok Tao; Tanaka, Takeshi; Ward, David J. (2017-07-04). "A new elusive otodontid shark (Lamniformes: Otodontidae) from the lower Miocene, and comments on the taxonomy of otodontid genera, including the 'megatoothed' clade" . Historical Biology. 29 (5): 704–714. doi:10.1080/08912963.2016.1236795. ISSN   0891-2963.
2. Agassiz, Louis (1839). Recherches Sur Les Poissons Fossiles. Neuchâtel, Switzerland: Imprimerie de Petitpierre.
3. Woodward, A.S. (1899). Catalogue of the fossil fishes in the British Museum (Natural History), Part I. Containing the Elasmobranchii. British Museum (Natural History). pp. 415–420. doi:10.5962/bhl.title.61854.
4. Laurito, Cesar A.; Calvo, Cristian; Valerio, Ana L.; Calvo, Alejandro; Chacón, Rafael (2014-06-27). "Ictiofauna del Mioceno Inferior de la localidad de Pacuare de Tres Equis, Formación Río Banano, provincia de Cartago, Costa Rica, y descripción de un nuevo género y una nueva especie de Scaridae". Revista geológica de América central (in Spanish). 50: 153–192. doi: 10.15517/rgac.v0i50.15121 . ISSN   2215-261X.