Enchodus (fromGreek:ἔγχοςenchos, 'spear' andGreek:ὀδούςodoús 'tooth')[2] is an extinctgenus ofaulopiformray-finned fish related tolancetfish andlizardfish. Species ofEnchodus flourished during theLate Cretaceous, where they were a widespread component of marine ecosystems worldwide, and there is some evidence that they may have survived to thePaleocene orEocene; however, this may just represent reworked Cretaceous material.[3][4][5]
Enchodus species were small to medium in size, withE. 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 thepalatine bones, leading to its misleading nickname amongfossil hunters andpaleoichthyologists, "the saber-toothedherring". These fangs, along with a long sleek body and large eyes, suggestEnchodus was apredatoryspecies.[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 theNiobrara Chalk, theMooreville Chalk Formation, thePierre Shale, and other geological formations deposited within theWestern Interior Seaway and theMississippi 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 moderndeep-sea fishes, such asanglerfish andviperfish. Other species, such asE. parvus, were considerably smaller, measuring only some centimetres (a few inches) long.[9]
Despite being a formidable predator, remains ofEnchodus are commonly found among the stomach contents of larger predators, includingsharks, other bony fish,mosasaurs,plesiosaurs and seabirds such asBaptornis advenus.[citation needed]
Species ofEnchodus are generally classified into two differentclades, the North American and the Mediterranean. It has been proposed that this distinction is the result of severalisolated events between the two populations over the Late Cretaceous.[13] The earliest known species isE. zimapanensis from the late Albian or earliest Cenomanian of Mexico.[14] Potentially earlier remains are known from the lateBarremian/early Aptian of Brazil (Morro de Chaves Formation), but these specimens are too fragmentary to confidently assign to this genus.[15][16]
Specimen ofE. gracilisReconstructed school ofE. petrosusSpecimen ofE. 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. 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, andMerchantville, 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. tineidaeHollowayet 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 validEnchodus species are based on only isolated teeth and bones.[15] The genusParenchodus, considered to be the sister genus ofEnchodus, has been synonymized with this genus based on some studies.[15] However, more recent studies have found it to be a valid genus distinct fromEnchodus.[13][18]
^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.
^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.
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