Lonchidion | |
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Teeth of an indeterminate species from the Tendaguru Formation | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Chondrichthyes |
Subclass: | Elasmobranchii |
Order: | † Hybodontiformes |
Family: | † Lonchidiidae |
Genus: | † Lonchidion Estes, 1964 |
Lonchidion is a genus of extinct hybodont in the family Lonchidiidae. The genus first appears in the fossil record during the Middle Triassic (Ladinian) [1] and was among the last surviving hybodont genera, with its youngest known fossils dating to the very end of the Cretaceous (Maastrichtian). [2]
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. [3] 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, [4] 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. [5]
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 3.5 centimetres (1.4 in) in length. [6] Other possible body remains of Lonchidion have been reported from other Early Cretaceous sites in Spain. [7] [8] Lonchidion humblei is suggested to have reached an adult length of 25 centimetres (9.8 in). [9]
The teeth of the genus are low crowned, and probably served to grind hard prey (durophagy). [10]
Xenacanthida is an order or superorder of extinct shark-like chondrichthyans known from the Carboniferous to Triassic. They were native to freshwater, marginal marine and shallow marine habitats. Some xenacanths may have grown to lengths of 5 m (16 ft). Most xenacanths died out at the end of the Permian in the End-Permian Mass Extinction, with only a few forms surviving into the Triassic.
Hybodus is an extinct genus of hybodont, a group of shark-like euselachians that lived from the Late Devonian to the end of the Cretaceous. Species closely related to the type species Hybodus reticulatus lived during the Early Jurassic epoch. Numerous species have been assigned to Hybodus spanning a large period of time, and it is currently considered a wastebasket taxon that is 'broadly polyphyletic' and requires reexamination.
Acrodus is an extinct genus of hybodont spanning from the Early Triassic to the Late Jurassic. It was durophagous, with blunt, broad teeth designed for crushing and grinding. Some Middle Triassic species have been suggested to have grown to lengths of 1.8–2.5 metres (5.9–8.2 ft). Species are known from both marine and freshwater environments, with all Middle and Late Jurassic species only known from freshwater.
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 (Neoselachii) as part of the clade Euselachii. They are distinguished from other chondrichthyans by their distinctive fin spines and cephalic spines present on the heads of males. An ecologically diverse group, they were abundant in marine and freshwater environments during the late Paleozoic and early Mesozoic, but were rare in open marine environments by the end of the Jurassic, having been largely replaced by modern sharks, though they were still common in freshwater and marginal marine habitats. They survived until the end of the Cretaceous, before going extinct.
Galverpeton is an extinct genus of prehistoric salamander. It lived during the Barremian-Aptian stages in the Early Cretaceous, in what is now Western Europe. The type species, Galverpeton ibericum, was described by Estes and Sanchíz in 1982. It was found in the Castellar Formation, part of the Galve fossil assemblage. The fossil is in the Institut Paleontologic Miquel Crusafont, Sabadell.
Metaceratodus is an extinct genus of prehistoric lungfish in the family Ceratodontidae, with an indeterminate specimen known from the Late Triassic (Norian)-aged Lissauer Breccia of Poland and more complete specimens known from the Late Cretaceous of Queensland, Australia and Argentina. The genus was named and described by Frederick Chapman in 1914.
Lissodus is an extinct genus of hybodont. While fossils attributed to this genus are known spanning from the latest Devonian (Famennian) to the very end of the Cretaceous (Maastrichtian), others consider the genus to have a more narrow range, spanning from the Early Triassic to the end of the Early Cretaceous (Albian). Lissodus is often placed in the family Lonchidiidae, though other authors consider it incertae sedis within Hybodontiformes. Lonchidion has often been regarded as synonymous, but many recent authors consider it to be a distinct but closely related genus.
Montsecosuchus is an extinct genus of atoposaurid crocodylomorphs. It is the replacement generic name for Alligatorium depereti, which was described in 1915 from the Montsec Lithographic Limestone quarry of Spain. Fossils found from this locality are from the Early Cretaceous, being Upper Berriasian-Lower Valanginian in age, belonging to the La Pedrera de Rúbies Formation While many publications concerning atoposaurids after 1915 have included mentions of A. depereti, none has offered a redescription or revision of the species, though some recognized that great differences existed between it and other members of the genus. In these publications, the skull of A. depereti was shorter in relation to body length than any other species of Alligatorium, and this may have been evidence for the genetic distinction of the species, although no replacement name was proposed. However, better preparation of the holotype specimen MGB 512, a nearly complete articulated skeleton embedded in a limestone matrix now housed in the Museu de Ciències Naturals de Barcelona, allowed for a revision of the species in 1990 in which the name Montsecosuchus was first used.
The La Pedrera de Rúbies Formation is an Early Cretaceous (late Berriasian to early Barremian geologic formation in Catalonia, Spain. The formation crops out in the area of the Montsec in the Organyà Basin. At the La Pedrera de Meià locality, the formation consists of rhythmically laminated, lithographic limestones that formed in the distal areas of a large, shallow coastal lake. It is noted for the exceptional preservation of articulated small vertebrates and insects, similar to that of the Solnhofen Limestone.
The Chinle Formation is an extensive geological unit in the southwestern United States, preserving a very diverse fauna of Late Triassic animals and plants. This is a list of fossilized organisms recovered from the formation.
Palaeoxyris is a morphogenus of eggs cases, widely thought to have been produced by hybodonts, with a predominant occurrence in ancient freshwater environments. They comprise a beak, a body and a pedicle. They display a conspicuous right-handed spiral of collarettes around the body, and in some cases, the pedicle, resulting in a rhomboidal pattern when flattened during fossilisation. At the end of the beak was a tendril which attached the egg to vegetation during development. The body of the egg ranges in length from 1.2–8.9 centimetres (0.47–3.50 in), depending on the species.
The Erfurt Formation, also known as the Lower Keuper, is a stratigraphic formation of the Keuper group and the Germanic Trias supergroup. It was deposited during the Ladinian stage of the Triassic period. It lies above the Upper Muschelkalk and below the Middle Keuper.
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