''Lepidotes'' (from el, λεπιδωτός , 'covered with scales') (previously known as ''Lepidotus'') is an extinct genus of
Mesozoic
The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceo ...
ray-finned fish
Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species.
The ray-finned fishes are so called because their fins are webs of skin supported by bony or hor ...
. It has been considered a
wastebasket taxon
Wastebasket taxon (also called a wastebin taxon, dustbin taxon or catch-all taxon) is a term used by some taxonomists to refer to a taxon that has the sole purpose of classifying organisms that do not fit anywhere else. They are typically defined ...
, 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.
[López-Arbarello, A. (2012).]
Phylogenetic Interrelationships of Ginglymodian Fishes (Actinopterygii: Neopterygii).
''PLoS One'', 7(7): e39370. 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, with other species transferred to new genera such as ''
Scheenstia
''Scheenstia'' is an extinct genus of neopterygian ray-finned fish from the Late Jurassic–Early Cretaceous of Europe. Fossils have been found in both marine and freshwater environments.
Most species of the genus were previously referred to the r ...
.''
''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 the family
Lepidotidae, part of the order
Lepisosteiformes within Ginglymodi, with other species occupying various positions within Ginglymodi.
Description
Inhabiting both freshwater lakes and shallow seas, ''Lepidotes'' was typically about long. The body was covered with thick, enamelled
scales
Scale or scales may refer to:
Mathematics
* Scale (descriptive set theory), an object defined on a set of points
* Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original
* Scale factor, a number w ...
.
''Lepidotes'' was one of the earliest fish in which the upper jawbones were no longer attached to the
jugal bone
The jugal is a skull bone found in most reptiles, amphibians and birds. In mammals, the jugal is often called the malar or zygomatic. It is connected to the quadratojugal and maxilla, as well as other bones, which may vary by species.
Anatomy ...
. 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
Carp are various species of oily freshwater fish from the family Cyprinidae, a very large group of fish native to Europe and Asia. While carp is consumed in many parts of the world, they are generally considered an invasive species in parts of ...
.
''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 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.
''L. elvensis''
''L. elvensis'' is the
type species
In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...
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 French National Museum of Natural History, known in French as the ' (abbreviation MNHN), is the national natural history museum of France and a ' of higher education part of Sorbonne Universities. The main museum, with four galleries, is loca ...
. The specimen measures up to long. The specimen is from the
Upper Lias
The Lias Group or Lias is a lithostratigraphic unit (a sequence of rock strata) found in a large area of western Europe, including the British Isles, the North Sea, the Low Countries and the north of Germany. It consists of marine limestones, sha ...
, in
Bavaria
Bavaria ( ; ), officially the Free State of Bavaria (german: Freistaat Bayern, link=no ), is a state in the south-east of Germany. With an area of , Bavaria is the largest German state by land area, comprising roughly a fifth of the total lan ...
. 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
The frontal bone is a bone in the human skull. The bone consists of two portions.''Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bony part of the forehead, par ...
is more than twice the length of the
parietal in the specimens. It also has a comparatively narrow marginal
symphysis
A symphysis (, pl. symphyses) is a fibrocartilaginous fusion between two bones. It is a type of cartilaginous joint, specifically a secondary cartilaginous joint.
# A symphysis is an amphiarthrosis, a slightly movable joint.
# A growing together ...
(articulation).
''L. semiserratus''
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
Yorkshire ( ; abbreviated Yorks), formally known as the County of York, is a Historic counties of England, historic county in northern England and by far the largest in the United Kingdom. Because of its large area in comparison with other Eng ...
.
''L. gallineki''
''L. gallineki'' is known from only an imperfect internal cast of the head and neck, assigned to ''Lepidotes'' by Michael (1863). The estimated length of the species is . The eternal bones are almost all apparently smooth. On the hinder margin, the scales are smooth and not serrated. The specimen was from the
Rhaetic
Rhaetic or Raetic (), also known as Rhaetian, was a language spoken in the ancient region of Rhaetia in the eastern Alps in pre-Roman and Roman times. It is documented by around 280 texts dated from the 5th up until the 1st century BC, which wer ...
of Upper
Silesia
Silesia (, also , ) is a historical region of Central Europe that lies mostly within Poland, with small parts in the Czech Republic and Germany. Its area is approximately , and the population is estimated at around 8,000,000. Silesia is split ...
.
''L. tuberculatus''
This species, named in 1837 by Louis Agassiz, is known from a single
suboperculum (scale-shaped lower opercular bone). It includes an assortment of unidentified remains from
Stonesfield Slate
Stonesfield is a village and civil parish about north of Witney in Oxfordshire, and about 10 miles (17 km) north-west of Oxford. The village is on the crest of an escarpment. The parish extends mostly north and north-east of the village, ...
. The formation dates back to the
Bathonian
In the geologic timescale the Bathonian is an age and stage of the Middle Jurassic. It lasted from approximately 168.3 Ma to around 166.1 Ma (million years ago). The Bathonian Age succeeds the Bajocian Age and precedes the Callovian Age.
Strat ...
of
England
England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...
. The only certain remain that can be assigned to ''L. tuberculatus'' is the suboperculum, so all the other material is considered to be unlikely to belong to it. The specimens provisionally assigned to ''L. tuberculatus'' by Woodward are P. 471, P. 1111, P. 1111a, P. 3524, P. 7411, 28606, 28607, 30569, 37219, 47141, and 47980.
''L. macrocheirus''
''L. macrocheirus'' was described by
Sir Philip Egerton in 1845. It could grow up to long. The trunk of the specimens are very robust, and the head measures one fifth of the total length. Like in ''L. elvensis'', the parietals measure less than half of the frontals. The frontals are three times as long as they are wide. It possessed slightly tumid, but styliform marginal teeth. The inner teeth were large and obtuse, but there pedicles were only moderately high. The species lacked any signs of ring-vertebrae. The fin-fulcra were large, but on the medial fins they were slender. The specimens assigned to it are P. 6839, P. 6899, P. 6900, P. 7412, and P. 7413, from the
Oxfordian of England.
''L. occidentalis''
''L. occidentalis'' is known from five ovular scales, described by
Joseph Leidy in 1860.
The enamel surfacing of all five scales is shiny and smooth. The largest of the scales is long, and the smallest in .
''L. haydeni''
''L. haydeni'' is a species known from a single, rectangular scale, described by Leidy in 1860. The scale is long and wide. The covering of the scale is small, rectangular squares. The root of the scale projects toward the front of one of the long sides. The specific name honors Dr. Hayden, who discovered many remains, including the only scale of ''L. haydeni''.
''L. latifrons''
''L. latifrons'' was named and described by
Arthur Smith Woodward in 1893. It is known from bones and scales from the head and trunk regions. It measured to about long. The scales of this species are large and smooth. There are no traces of rings on the vertebrae. The marginal teeth are slender and styliform. The portion of the
dentary that bears teeth is deepened near the symphysis. It is known from a few, mostly complete specimens, P. 6841, P. 6838, and P. 6840. The specimens date to the
Oxfordian of
Huntingdonshire.
References
Semionotiformes
Prehistoric ray-finned fish genera
Jurassic fish of North America
Jurassic fish of Europe
Early Cretaceous fish of South America
Early Cretaceous fish of Europe
Late Cretaceous fish of Africa
Cretaceous Brazil
Fossils of Brazil
Crato Formation
Romualdo Formation
Cenomanian genus extinctions
Toarcian genus first appearances
Fossil taxa described in 1832
Taxa named by Louis Agassiz
{{Jurassic-fish-stub