Lepidotes
Lepidotes (from Greek: λεπιδωτός lepidōtós, 'covered with scales') (previously known as Lepidotus)[4] is an extinct genus of Mesozoic ray-finned fish. It has been considered a wastebasket taxon, characterised by "general features, such as thick rhomboid scales and, for most of the species, by semi-tritorial or strongly tritorial dentition."[5] with dozens of species assigned to it.[3] Fossils attributed to Lepidotes have been found in Jurassic and Cretaceous rocks worldwide.[2][6][7][8] It has been argued that Lepidotes should be restricted to species closely related to the type species L. gigas, which are only known from the Early Jurassic of Central Europe, with most other species being not closely related.[9] Lepidotes belongs to Ginglymodi, a clade of fish whose only living representatives are the gars (Lepisosteidae). The type species L. gigas and close relatives are thought to be members of Lepisosteiformes within Ginglymodi, with other species occupying various positions within Ginglymodi, such as the Semionotiformes.[9]
Inhabiting both freshwater lakes and shallow seas, Lepidotes was typically about 30 centimetres (12 in) long. The body was covered with thick, enamelled scales.[10] Batteries of peg-like teeth enabled Lepidotes to crush the shells of its molluscan prey. Fossil examples of these teeth were collected in medieval times as 'toadstones', claimed to be found within the heads of toads and to have magical powers against poisoning.
Lepidotes was one of the earliest fish in which the upper jawbones were no longer attached to the jugal bone. This allowed the jaws to be stretched into a 'tube' so that the fish could suck in prey from a greater distance than in previous species.[10] This system is still seen in some modern fish, such as carp.
Lepidotes scales are ovular in shape, and are 18.5 millimetres (0.73 in) long and 3 millimetres (0.12 in) thick at the thickest point.[11] The scales are smooth and shiny on the external surface, with only a few small depressions scattered toward the centre that are shaped like punctures.[11]
L. elvensis is the type species of Lepidotes. It was described by Ducrotay de Blainville in 1818. It is known from an almost complete specimen housed in the Paris Museum of Natural History. The specimen measures up to 75 centimetres (2.46 ft) long. The specimen is from the Upper Lias, in Bavaria. The specimens P. 7406, P. 7407, P. 7408, P. 2014, P. 2054, P. 3529a, P. 3529b, 18992, 18993/94 19662, 32421, and 32422 have all been assigned to this species. The external bones of this species are smooth, but some have sparsely-placed coarse tuberculations (protuberances). The frontal bone is more than twice the length of the parietal in the specimens. It also has a comparatively narrow marginal symphysis (articulation).[3]
This species was named by Agassiz in 1837 and is known from some incomplete remains. It has been classified as closely related to L. elvensis. It is more elongate than L. elvensis, being four times as long as tall. It also has more sharply angulated sutures between its parietals, and the parietals are also proportionally longer. It is known from the specimens P. 1127, P. 7409, P. 2012, P. 2012a, P. 3527, P. 3528, P. 3528a, P. 5213, P. 5228, P. 6394, P. 7410, and 35556, all from the Upper Lias of Yorkshire.[3]
