Cheirolepis
Encyclopedia
Cheirolepis is an extinct genus of ray-finned fish that lived in the Devonian
period of Europe and North America. It is the only genus yet known within the family Cheirolepidae and the order Cheirolepiformes. It was among the most basal
of the Devonian actinopterygians and is considered the first to possess the "standard" dermal cranial bones seen in later actinopterygians.
Cheirolepis was a predatory freshwater fish about 55 centimetres (21.7 in) long. It had a streamlined body with small, triangular ganoid scales
similar to those of the Acanthodii
. Cheirolepis had well-developed fins which gave it speed and stability, and was probably an active predator. Based on the size of its eyes, it hunted by sight. Cheirolepiss jaws, lined with sharp teeth, could be opened very wide, allowing it to swallow prey two thirds of its own size.
, named in 1835, is C. trailli. Remains of this species have been found from Scotland
and date back to the Eifelian and Givetian stages of the Middle Devonian. C. canadensis was described in 1881 from material found in Miguasha
, Canada
that dated back to the middle Frasnian
stage of the Late Devonian. Two species, C. gracilis and C. gaugeri, have been found from Germany
and Belarus
in deposits that are of Givetian age. They were first described in 1973 from scale material that is now of questionable validity. Another species has been found from Belarus that lived during the Eifelian, and has been named C. sinualis. A new species has recently been described from a locality in Red Hill, Nevada
deposited during the Mid-Late Devonian boundary. The specimen from which this species was named, consisting of scales and a lower jaw, was originally referred to C. canadensis. New, more complete specimens have shown it to be distinct from the type, although a species name is yet to be given for the remains.
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
period of Europe and North America. It is the only genus yet known within the family Cheirolepidae and the order Cheirolepiformes. It was among the most basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
of the Devonian actinopterygians and is considered the first to possess the "standard" dermal cranial bones seen in later actinopterygians.
Cheirolepis was a predatory freshwater fish about 55 centimetres (21.7 in) long. It had a streamlined body with small, triangular ganoid scales
Scale (zoology)
In most biological nomenclature, a scale is a small rigid plate that grows out of an animal's skin to provide protection. In lepidopteran species, scales are plates on the surface of the insect wing, and provide coloration...
similar to those of the Acanthodii
Acanthodii
Acanthodii is a class of extinct fishes, sharing features with both bony fish and cartilaginous fish. In form they resembled sharks, but their epidermis was covered with tiny rhomboid platelets like the scales of holosteans...
. Cheirolepis had well-developed fins which gave it speed and stability, and was probably an active predator. Based on the size of its eyes, it hunted by sight. Cheirolepiss jaws, lined with sharp teeth, could be opened very wide, allowing it to swallow prey two thirds of its own size.
Species
Six possible species of Cheirolepis are currently known. The type speciesType species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
, named in 1835, is C. trailli. Remains of this species have been found from Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
and date back to the Eifelian and Givetian stages of the Middle Devonian. C. canadensis was described in 1881 from material found in Miguasha
Miguasha National Park
Miguasha National Park is a protected area near Carleton-sur-Mer on the Gaspé Peninsula of Quebec in Canada. Created in 1985 by the Government of Quebec, Miguasha was designated a World Heritage Site in 1999 in recognition of its wealth of fossils, which display a crucial time during the evolution...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
that dated back to the middle Frasnian
Frasnian
The Frasnian is one of two faunal stages in the Late Devonian epoch. It lasted from 385.3 ± 2.6 million years ago to 374.5 ± 2.6 million years ago. It was preceded by the Givetian stage and followed by the Famennian stage...
stage of the Late Devonian. Two species, C. gracilis and C. gaugeri, have been found from Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
and Belarus
Belarus
Belarus , officially the Republic of Belarus, is a landlocked country in Eastern Europe, bordered clockwise by Russia to the northeast, Ukraine to the south, Poland to the west, and Lithuania and Latvia to the northwest. Its capital is Minsk; other major cities include Brest, Grodno , Gomel ,...
in deposits that are of Givetian age. They were first described in 1973 from scale material that is now of questionable validity. Another species has been found from Belarus that lived during the Eifelian, and has been named C. sinualis. A new species has recently been described from a locality in Red Hill, Nevada
Nevada
Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...
deposited during the Mid-Late Devonian boundary. The specimen from which this species was named, consisting of scales and a lower jaw, was originally referred to C. canadensis. New, more complete specimens have shown it to be distinct from the type, although a species name is yet to be given for the remains.
External links
- Cheirolepis at PalaeosPalaeosPalaeos.com is a web site on biology, paleontology, cladistics and geology and which covers the history of Earth. The site is well respected and has been used as a reference by professional paleontologists such as Michael J. Benton, the professor of vertebrate palaeontology in the Department of...