Lepidotes
Lepidotes is an extinct genus of Mesozoic ray-finned fish. It has long 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 with dozens of species assigned to it. Fossils attributed to Lepidotes have been found in Jurassic and Cretaceous rocks worldwide. 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 Western and Central Europe, with most other species being not closely related, with other species transferred to new genera such as Scheenstia. ''Lepidotes belongs to Ginglymodi, a clade of fish whose only living representatives are the gars. The type species L. gigas'' and close relatives are thought to be members of the family Lepidotidae, part of the order Lepisosteiformes within Ginglymodi, with other species occupying various other positions within Ginglymodi.
Description
Inhabiting both freshwater lakes and shallow seas, Lepidotes was typically about long. The body was covered with thick, enamelled scales.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. This system is still seen in some modern fish, such as carp.
Lepidotes scales are ovular in shape, and are long and thick at the thickest point. 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.
Stomach contents of Lepidotes from the Early Jurassic of Germany have found remains of crustacean cuticles, and it is suggested that they fed on relatively soft-bodied prey, which was grasped with the slender marginal teeth, before being crushed by the rounded palatal teeth.
Distinguishing characteristics
Many characteristics were identified by Woodward in 1895, and they are listed below:- a fusiform trunk only moderately compressed;
- the fact that the marginal teeth are compressed;
- the presence of stouter inner teeth that are smooth;
- ossified ribs;
- very large fin-fulera on all fins;
- that all paired fins are small;
- short and deep dorsal and anal fins;
- very robust, smooth or feebly oriented scales;
- flank scales that are not much deeper than wide;
- scales ventrally nearly as deep as broad;
- and the presence of inconspicuous dorsal and ventral ridge-scales.
Taxonomy