Lonchidion derenzii, sp. nov., a new lonchidiid shark (Chondrichthyes, Hybodontiforms) from the Upper Triassic of Spain, with remarks on lonchidiid enameloid

Lonchidiidae Herman, 1977 Herman, J. 1977. Les Sélaciens des terrains néocrétacés and paléocènes de Belgique et des contrées limitrophes. Eléments d'une biostratigraphic intercontinentale. Mémoires pour servir à l'explication des Cartes géologiques et Miniéres de la Belgique 15:1–401., represents one of the most diverse and controversial families of Hybodontiformes, the sister group of Neoselachii (i.e., modern sharks, skates, and rays). It was initially erected as a monogeneric family including only Lonchidion Estes, 1964 Estes, R. 1964. Fossil vertebrates from the Late Cretaceous Lance Formation, Eastern Wyoming. University of California Publications, Geological Sciences 49:1–187., a genus of small euryhaline hybodonts from the Mesozoic. Recently, Cappetta (2012 Cappetta, H. 2012. Handbook of Paleoichthyology, Volume 3E. Chondrichthyes. Mesozoic and Cenozoic Elasmobranchii: Teeth. Verlag Dr. Friedrich Pfeil, Munich, 512 pp.) recognized up to eight genera within the family: Baharyodon, Diplolonchidion, Vectiselachos, Hylaeobatis, Isanodus, Parvodus, Lissodus, and Lonchidion, although the content of the family is still under discussion (see, e.g., Rees, 2008 Rees, J. 2008. Interrelationships of Mesozoic hybodont sharks as indicated by dental morphology - preliminary results. Acta Geologica Polonica 58:217–221.[Web of Science ®]; Khamha et al., 2016). Major discrepancies concern the phylogenetic relationships between Lonchidion and Lissodus and the taxonomic status of the latter. Thus, based on the general similarity of their teeth, Duffin (1985 Duffin, C. 1985. Revision of the hybodont selachian genus Lissodus Brough (1935). Palaeontographica Abteilung A 188:105–152., 2001 Duffin, C. 2001. Synopsis of the selachian genus Lissodus Brough, 1935. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 221:145–218.[Web of Science ®]) considered Lonchidion as a junior synonym of Lissodus. Subsequently, Rees and Underwood (2002 Rees, J., and C. J. Underwood. 2002. The status of the shark genus Lissodus Brough, 1935, and the position of nominal Lissodus species within the hybodontoidea (Selachii). Journal of Vertebrate Paleontology 22:471–479.[Taylor & Francis Online], [Web of Science ®], [CSA]) restored Lonchidion as a valid genus, closely related to Lissodus, within the family Lonchidiidae (together with Vectiselachos, Parvodus, and Hylaeobatis). This interpretation has been followed by several authors (e.g., Fischer, 2008 Fischer, J. S. 2008. Brief synopsis of the hybodont form taxon Lissodus Brough, 1935, with remarks on the environment and associated fauna. Freiberger Forschungshefte C 528:1–23.; Cappetta, 2012 Cappetta, H. 2012. Handbook of Paleoichthyology, Volume 3E. Chondrichthyes. Mesozoic and Cenozoic Elasmobranchii: Teeth. Verlag Dr. Friedrich Pfeil, Munich, 512 pp.; Johns et al., 2014 Johns, M. J., G. L. Albanesi, and G. G. Voldman. 2014. Freshwater shark teeth (Family Lonchidiidae) from the Middle–Upper Triassic (Ladinian–Carnian) Paramillo Formation in the Mendoza Precordillera, Argentina. Journal of Vertebrate Paleontology 34:512–523.[Taylor & Francis Online], [Web of Science ®]). In contrast, Rees (2008 Rees, J. 2008. Interrelationships of Mesozoic hybodont sharks as indicated by dental morphology - preliminary results. Acta Geologica Polonica 58:217–221.[Web of Science ®]) considered Lonchidion and Lissodus not so closely related to each other, excluding Lissodus from Lonchidiidae.

The majority of Lonchidion species has been described on the basis of disarticulated teeth, and complete or partial articulated skeletons have been known only recently from juvenile specimens, assigned to Lonchidion sp., from the inland lacustrine Konservat-Lagerstätten outcrop of Las Hoyas (Lower Cretaceous, Spain) (Soler-Gijón et al., 2016 Soler-Gijón, R., F. J. Poyato-Ariza, J. G. Maisey, and J. A. Lane. 2016. Chondrichthyes; pp. 103–113 in F. J. Poyato-Ariza and A. D. Buscalioni (eds.), Las Hoyas: A Cretaceous Wetland. Verlag Dr. Friedrich Pfeil, Munich.). Currently, the stratigraphic distribution of the ranges from the Middle–Upper Triassic (Fischer et al., 2011 Fischer, J., S. Voigt, J. W. Schneider, M. Buchwitz, and S. Voigt. 2011. A selachian freshwater fauna from the Triassic of Kyrgyzstan and its implication for Mesozoic shark nurseries. Journal of Vertebrate Paleontology 31:937–953.[Taylor & Francis Online], [Web of Science ®]; Johns et al., 2014 Johns, M. J., G. L. Albanesi, and G. G. Voldman. 2014. Freshwater shark teeth (Family Lonchidiidae) from the Middle–Upper Triassic (Ladinian–Carnian) Paramillo Formation in the Mendoza Precordillera, Argentina. Journal of Vertebrate Paleontology 34:512–523.[Taylor & Francis Online], [Web of Science ®]) to the Upper Cretaceous (Estes, 1964 Estes, R. 1964. Fossil vertebrates from the Late Cretaceous Lance Formation, Eastern Wyoming. University of California Publications, Geological Sciences 49:1–187.).

In the present study, we describe a new species assigned to Lonchidiidae, Lonchidion derenzii, sp. nov., based on distinctive isolated teeth from the Upper Triassic (Carnian) of Spain, representing the earliest well-documented occurrence of the genus in Europe.