''Lonchidion'' is a genus of extinct

hybodont Hybodontiformes, commonly called hybodonts, are an extinct group of shark-like cartilaginous fish (chondrichthyans) which existed from the late Devonian to the Late Cretaceous. Hybodonts share a close common ancestry with modern sharks and rays ( ...

in the family Lonchidiidae. The genus first appears in the fossil record during the Middle Triassic (

Ladinian The Ladinian is a stage and age in the Middle Triassic series or epoch. It spans the time between Ma and ~237 Ma (million years ago). The Ladinian was preceded by the Anisian and succeeded by the Carnian (part of the Upper or Late Triassic ...

) and was among the last surviving hybodont genera, with its youngest known fossils dating to the very end of the Cretaceous (

Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...

). ''Lonchidion'' was first described by

Richard Estes Richard Estes (born May 14, 1932, in Kewanee, Illinois) is an American artist, best known for his photorealist paintings. The paintings generally consist of reflective, clean, and inanimate city and geometric landscapes. He is regarded as one of ...

in 1964, and the type species is ''L. selachas''. Fossils of ''Lonchidion'' have been found worldwide. The genus has been proposed to be

euryhaline Euryhaline organisms are able to adapt to a wide range of salinities. An example of a euryhaline fish is the short-finned molly, '' Poecilia sphenops'', which can live in fresh water, brackish water, or salt water. The green crab ('' Carcinus m ...

, and is often found in freshwater and brackish deposits. Hybodont egg cases ('' Palaeoxyris'') associated with juvenile teeth of ''L. ferganensis'' in the Triassic lake deposits of the

Madygen Formation The Madygen Formation (Russian language, Russian: Madygen Svita) is a Middle Triassic, Middle–Late Triassic (Ladinian–Carnian) geologic formation and lagerstätte in the Batken Region, Batken and Osh Regions of western Kyrgyzstan, with minor ...

of Kyrgyzstan suggests that this species spawned in freshwater environments, with ''Palaeoxyris'' egg cases found in freshwater deposits of the Late Triassic

Chinle Formation The Chinle Formation is an Upper Triassic continental geological formation of fluvial, lacustrine, and palustrine to eolian deposits spread across the U.S. states of Nevada, Utah, northern Arizona, western New Mexico, and western Colorado. In ...

in North America suggested to have been produced by ''Lonchidion humblei''. While the genus is primarily known from teeth, a preserved body impression of a subadult individual is known from the Early Cretaceous freshwater Las Hoyas site in Spain. This specimen is among the smallest known elasmobranchs, at around in length. Other possible body remains of ''Lonchidion'' have been reported from other Early Cretaceous sites in Spain. ''Lonchidion humblei'' is suggested to have reached an adult length of . The teeth of the genus are low crowned, and probably served to grind hard prey (

durophagy Durophagy is the eating behavior of animals that consume Seashell, hard-shelled or exoskeleton-bearing organisms, such as corals, shelled mollusks, or crabs. It is mostly used to describe fish, but is also used when describing reptiles, including ...

). Some authors have proposed that ''Lonchidion'' is not a valid genus, and that its teeth instead represent a morphological type present among many juvenile hybodonts but that is later lost in adults.

Species

* ''Lonchidion anitae'' Thurmond, 1971 * ''Lonchidion breve'' Patterson, 1966 * ''Lonchidion crenulatum'' Patterson, 1966 * ''Lonchidion humblei'' Murry, 1981 * ''Lonchidion indicus'' Yadagiri, 1986 * ''Lonchidion inflexum'' Underwood & Rees, 2002 * ''Lonchidion microselachos'' Estes & Sanchíz, 1982 * ''Lonchidion selachas'' Estes, 1964 * ''Lonchidion selachos'' Estes, 1964 * ''Lonchidion striatum'' Patterson, 1966 * ''Lonchidion ferganensis'' Fischer et al., 2011 * ''Lonchidion conrugis'' Wick & Lehman, 2025

References

External links

''Lonchidion''
at the

Paleobiology Database The Paleobiology Database (PBDB) is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database originated in the NCEAS-funded Phanerozoic Marine Pale ...

Triassic cartilaginous fish Cretaceous cartilaginous fish Hybodontiformes Triassic fish of Asia Hell Creek fauna Laramie Formation Camarillas Formation Madygen Formation Fossil taxa described in 1964 {{paleo-cartilaginous-fish-stub