Lonchidion is a genus of extinct hybodont in the family Lonchidiidae. The genus first appears in the fossil record during the Middle Triassic (Ladinian) and was among the last surviving hybodont genera, with its youngest known fossils dating to the very end of the Cretaceous (Maastrichtian).
Lonchidion was first described by Richard Estes in 1964, and the type species is L. selachas. Fossils of Lonchidion have been found worldwide. The genus has been proposed to be euryhaline, 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 of Kyrgyzstan suggests that this species spawned in freshwater environments,Jan Fischer, Sebastian Voigt, Jörg W. Schneider, Michael Buchwitz and Silke Voigt (2011). "A selachian freshwater fauna from the Triassic of Kyrgyzstan and its implication for Mesozoic shark nurseries". Journal of Vertebrate Paleontology 31 (5): 937–953. . with Palaeoxyris egg cases found in freshwater deposits of the Late Triassic Chinle Formation 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.GOMEZ-PALLEROLA, J. E. 1985. Nuevos Hybodóntidos del Cretácico Inferior de Santa María de Meyá (Lérida) [New Hybodontids from the Early Cretaceous of Santa María de Meyá (Lérida)]. Boletin Geologico y Minero, 96(4):372–380.GOMEZ-PALLEROLA, J. E. 1992. Nota sobre los tiburones hybodontos de las calizas litográficas del Cretácico Inferior del Montsec (Lérida). [Note on hybodont sharks from the Lower Cretaceous lithographic limestones of Montsec (Lérida)] Boletin Geologico y Minero, 103:3–33. 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). 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 minimorsus Keeble et al., 2026 Lonchidion selachas Estes, 1964 Lonchidion selachos Estes, 1964 Lonchidion striatum Patterson, 1966 Lonchidion ferganensis Fischer et al., 2011 Lonchidion conrugis Wick & Lehman, 2025 Lonchidion khoratensis Cuny, Suteethorn, Kamha, Buffetaut, Philippe, 2006
References
External links Lonchidion at the Paleobiology Database