Enchodus (from Greek: ἔγχοςenchos, 'spear' and Greek: ὀδούςodoús 'tooth')[2] is an extinct genus of aulopiformray-finned fish related to lancetfish and lizardfish. Species of Enchodus flourished during the Late Cretaceous, where they were a widespread component of marine ecosystems worldwide, and there is some evidence that they may have survived to the Paleocene or Eocene; however, this may just represent reworked Cretaceous material.[3][4][5]
Description
Enchodus species were small to medium in size, with E. zinensis reaching 172.2 centimetres (67.8 in) long.[6] One of the genus' most notable attributes are the large "fangs" at the front of the upper and lower jaws and on the palatine bones, leading to its misleading nickname among fossil hunters and paleoichthyologists, "the saber-toothed herring". These fangs, along with a long sleek body and large eyes, suggest Enchodus was a predatoryspecies.[7]
E. petrosus, with standard length around 76.7 centimetres (30.2 in)[6] and sometimes over 1 metre (3 ft 3 in),[8] is known from common remains coming from the Niobrara Chalk, the Mooreville Chalk Formation, the Pierre Shale, and other geological formations deposited within the Western Interior Seaway and the Mississippi Embayment. Large individuals of this species had fangs measuring over 6 centimetres (2.4 in) in length, giving its skull an appearance somewhat reminiscent of modern deep-sea fishes, such as anglerfish and viperfish. Other species, such as E. parvus, were considerably smaller, measuring only some centimetres (a few inches) long.[9]
Despite being a formidable predator, remains of Enchodus are commonly found among the stomach contents of larger predators, including sharks, other bony fish, mosasaurs, plesiosaurs and seabirds such as Baptornis advenus.[citation needed]
Species of Enchodus are generally classified into two different clades, the North American and the Mediterranean. It has been proposed that this distinction is the result of several isolated events between the two populations over the Late Cretaceous.[13] The earliest known species is E. zimapanensis from the late Albian or earliest Cenomanian of Mexico.[14] Potentially earlier remains are known from the late Barremian/early Aptian of Brazil (Morro de Chaves Formation), but these specimens are too fragmentary to confidently assign to this genus.[15][16]
Species
Specimen of E. gracilisReconstructed school of E. petrosusSpecimen of E. faujasi
Enchodus was a diverse, long-lived genus with many species known throughout its temporal and geographic range. The following valid species are known:[12][1][15][17]
E. elegansDartevelle & Casier 1949 - Coniacian of Angola (Itombe Formation), Maastrichtian of Brazil (Gramame Formation), Niger, Syria, and Jordan (Alhisa Phosphorite Formation); Maastrichtian to potentially Danian of Morocco (Ouled Abdoun Basin)
E. gladiolus(Cope, 1872) - Cenomanian to Maastrichtian of the United States (Greenhorn Limestone of Colorado, Kansas & Iowa, Graneros Shale & Carlile Shale of Nebraska, Mancos Shale of New Mexico, Carlile Shale of Kansas, Arkansas, and Merchantville, Navesink & Hornerstown Formations of New Jersey), Santonian to Campanian of Russia (Orenburg, Rybushka Formation), Maastrichtian of Argentina (Jagüel Formation), potentially Peru (Vivian Formation)[10]
E. gracilis(von der Marck, 1858) - Campanian of Germany (Ahlen Formation)
E. libycus (Quaas, 1902) - Cenomanian to Maastrichtian of Brazil (Cotinguiba Formation, Gramame Formation), Campanian of Egypt, Maastrichtian to potentially Danian of Morocco (Ouled Abdoun Basin)[21]
E. shumardiLeidy, 1856 - Cenomanian to Santonian of the United States (Greenhorn Limestone of Iowa, Kansas & Colorado, Carlile & Graneros Shale of Nebraska & Kansas, Niobrara Formation of Kansas & South Dakota) and Canada (Ashville Formation of Saskatchewan, Kaskapau Formation of Alberta)
E. subaequilateralisCope, 1885 - Maastrichtian of Brazil (Gramame Formation)
E. tineidaeHolloway et al., 2017 - Campanian of Egypt (Duwi Formation)[13]
Many other dubious species based on insufficient remains have been described throughout its range. Even most of the valid Enchodus species are based on only isolated teeth and bones.[15] The genus Parenchodus, considered to be the sister genus of Enchodus, has been synonymized with this genus based on some studies.[15] However, more recent studies have found it to be a valid genus distinct from Enchodus.[13][18]
^Fielitz, Christopher; González-Rodríguez, Katia A. (2010). "A New Species of Enchodus (aulopiformes: Enchodontidae) from the Cretaceous (albian to Cenomanian) of Zimapán, Hidalgo, México". Journal of Vertebrate Paleontology. 30 (5): 1343–1351. Bibcode:2010JVPal..30.1343F. doi:10.1080/02724634.2010.501438. JSTOR40864352. S2CID84281080.
^ abcRana, R. S.; Kumar, K.; Singh, H.; Rose, K. D. (2005). "Lower vertebrates from the Late Palaeocene–Earliest Eocene Akli Formation, Giral Lignite Mine, Barmer District, western India". Current Science. 89 (9): 1606–1613. JSTOR24110948.
^ abDavis, Matthew P.; Fielitz, Christopher (December 2010). "Estimating divergence times of lizardfishes and their allies (Euteleostei: Aulopiformes) and the timing of deep-sea adaptations". Molecular Phylogenetics and Evolution. 57 (3): 1194–1208. Bibcode:2010MolPE..57.1194D. doi:10.1016/j.ympev.2010.09.003. PMID20854916.
^ abDíaz-Cruz, Jesús Alberto; Alvarado-Ortega, Jesús; Ramírez-Sánchez, Marcia M.; Bernard, Emma Louise; Allington-Jones, Lu; Graham, Mark (November 2021). "Phylogenetic morphometrics, geometric morphometrics and the Mexican fossils to understand evolutionary trends of enchodontid fishes". Journal of South American Earth Sciences. 111: 103492. Bibcode:2021JSAES.11103492D. doi:10.1016/j.jsames.2021.103492.
^Chida, Mori; Brinkman, Donald B.; Murray, Alison M. (October 2023). "A large, new dercetid fish (Teleostei: Aulopiformes) from the Campanian Bearpaw Formation of Alberta, Canada". Cretaceous Research. 150: 105579. Bibcode:2023CrRes.15005579C. doi:10.1016/j.cretres.2023.105579. S2CID258803963.
^Everhart, M.J. (2017). Oceans of Kansas, Second Edition: A Natural History of the Western Interior Sea (Life of the Past). Indiana University Press. p. 117. ISBN978-0253026323.
Russell, Dale A. (1988). A Check List of North American Marine Cretaceous Vertebrates Including Fresh Water Fishes. Tyrrell Museum of Palaeontology. ISBN978-1-55006-106-2.
Davis, Matthew P.; Fielitz, Christopher (December 2010). "Estimating divergence times of lizardfishes and their allies (Euteleostei: Aulopiformes) and the timing of deep-sea adaptations". Molecular Phylogenetics and Evolution. 57 (3): 1194–1208. Bibcode:2010MolPE..57.1194D. doi:10.1016/j.ympev.2010.09.003. PMID20854916.
