''Ophiacodon'' (meaning "snake tooth") is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

synapsid Synapsids + (, 'arch') > () "having a fused arch"; synonymous with ''theropsids'' (Greek, "beast-face") are one of the two major groups of animals that evolved from basal amniotes, the other being the sauropsids, the group that includes rep ...

belonging to the family

Ophiacodontidae Ophiacodontidae is an extinct family of early eupelycosaurs from the Carboniferous and Permian. '' Archaeothyris'', and ''Clepsydrops'' were among the earliest ophiacodontids, appearing in the Late Carboniferous. Ophiacodontids are among the m ...

that lived from the

Late Carboniferous Late may refer to: * LATE, an acronym which could stand for: ** Limbic-predominant age-related TDP-43 encephalopathy, a proposed form of dementia ** Local-authority trading enterprise, a New Zealand business law ** Local average treatment effe ...

to the

Early Permian 01 or '01 may refer to: * The year 2001, or any year ending with 01 * The month of January * 1 (number) Music * 01'' (Richard Müller album), 2001 * ''01'' (Son of Dave album), 2000 * ''01'' (Urban Zakapa album), 2011 * ''O1'' (Hiroyuki Sawano ...

in North America and Europe. The genus was named along with its

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( ...

''O. mirus'' by paleontologist

Othniel Charles Marsh Othniel Charles Marsh (October 29, 1831 – March 18, 1899) was an American professor of Paleontology in Yale College and President of the National Academy of Sciences. He was one of the preeminent scientists in the field of paleontology. Among ...

in 1878 and currently includes five other species. As an ophiacodontid, ''Ophiacodon'' is one of the most

basal Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''. Science * Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure * Basal (medicine), a minimal level that is nec ...

synapsids and is close to the evolutionary line leading to mammals. Ophiacodon retroversus

Description

''Ophiacodon'' has a large skull with a deep snout. It has the longest skull of any early synapsid, reaching up to in one specimen. The jaws are lined with many small teeth. It was larger than most other

tetrapod Tetrapods (; ) are four-limb (anatomy), limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant taxon, extant and extinct amphibians, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids (p ...

s (four-limbed vertebrates) of its time, ranging from in length and in weight. Specimens of ''Ophiacodon'' vary greatly in size. These differences in size were once used to distinguish species, but are now recognized as

ontogenetic Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the egg to adult. The term can also be used to refer to the s ...

variations related to the ages of individuals. Smaller bones often have more poorly developed joint surfaces than larger bones, implying that they come from juvenile individuals while the larger bones come from adults. Analysis of the

histology Histology, also known as microscopic anatomy or microanatomy, is the branch of biology which studies the microscopic anatomy of biological tissues. Histology is the microscopic counterpart to gross anatomy, which looks at larger structures vi ...

or microscopic anatomy of bones suggests that differences in size represent different growth stages rather than different species.

Range

Remains of ''Ophiacodon'' have been found in North America and Europe. *

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 ...

Kenilworth Kenilworth ( ) is a market town and civil parish in the Warwick District in Warwickshire, England, south-west of Coventry, north of Warwick and north-west of London. It lies on Finham Brook, a tributary of the River Sowe, which joins the ...

Cisuralian The Cisuralian is the first series/epoch of the Permian. The Cisuralian was preceded by the Pennsylvanian and followed by the Guadalupian. The Cisuralian Epoch is named after the western slopes of the Ural Mountains in Russia and Kazakhstan and ...

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan ar ...

: Lower Permian of

Autun Autun () is a subprefecture of the Saône-et-Loire department in the Bourgogne-Franche-Comté region of central-eastern France. It was founded during the Principate era of the early Roman Empire by Emperor Augustus as Augustodunum to give ...

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tota ...

: ** (?)

Nova Scotia Nova Scotia ( ; ; ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. Nova Scotia is Latin for "New Scotland". Most of the population are native En ...

Joggins Formation The Joggins Formation is a Formation (geology), geologic formation in Nova Scotia. It preserves fossils dating back to the Carboniferous Period (geology), period, including ''Hylonomus'', the earliest known reptile. In addition to fossils, the Jog ...

Kasimovian The Kasimovian is a geochronologic age or chronostratigraphic stage in the ICS geologic timescale. It is the third stage in the Pennsylvanian (late Carboniferous), lasting from to Ma.; 2004: ''A Geologic Time Scale 2004'', Cambridge Universi ...

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

: **

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a U.S. state, state in the Southwestern United States. It is the list of U.S. states and territories by area, 6th largest and the list of U.S. states and territories by population, 14 ...

Cutler Formation The Cutler Formation or Cutler Group is a rock unit that is exposed across the U.S. states of Arizona, northwest New Mexico, southeast Utah and southwest Colorado. It was laid down in the Early Permian during the Wolfcampian epoch. Descr ...

Colorado Colorado (, other variants) is a state in the Mountain states, Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the wes ...

Kansas Kansas () is a state in the Midwestern United States. Its capital is Topeka, and its largest city is Wichita. Kansas is a landlocked state bordered by Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to ...

Fort Riley Fort Riley is a United States Army installation located in North Central Kansas, on the Kansas River, also known as the Kaw, between Junction City and Manhattan. The Fort Riley Military Reservation covers 101,733 acres (41,170 ha) in G ...

Chase Group The Chase Group is a sedimentary rock unit of Lower Permian age. It is defined in east-central Kansas and extends into Oklahoma and Nebraska as well as the Colorado subsurface where it is undivided. The unit was assigned geologic group rank arou ...

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe, New Mexico, Santa Fe , LargestCity = Albuquerque, New Mexico, Albuquerque , LargestMetro = Albuquerque metropolitan area, Tiguex , Offi ...

Ohio Ohio () is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. Of the List of states and territories of the United States, fifty U.S. states, it is the List of U.S. states and territories by area, 34th-l ...

: Greene Formation,

Dunkard Group The Permian Dunkard Group (Pd) is an area of rock, Early Permian in age, in the south of Ohio, southwestern Pennsylvania, West Virginia and the hilltops of the Georges Creek Basin of Maryland. In Ohio, it is found primarily in Washington County. I ...

** Oklahoma:

Ada Formation The Ada Formation is a geologic formation in Oklahoma, within and to west of Ada. It consist mainly of shale with numerous limestone layers which get thinner and eventually disappear to the south, where they are replaced by fine-grained sandston ...

Pennsylvanian Pennsylvanian may refer to: * A person or thing from Pennsylvania * Pennsylvanian (geology) The Pennsylvanian ( , also known as Upper Carboniferous or Late Carboniferous) is, in the International Commission on Stratigraphy, ICS geologic timesca ...

Clyde Formation The Clyde Formation is a geologic formation in Texas. It preserves fossils dating back to the Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period millio ...

Wellington Formation The Wellington Formation is an Early Permian geologic formation in Kansas and Oklahoma. The formation's Hutchinson Salt Member is more recognized by the community than the formation itself, and the salt is still mined in central Kansas. The Well ...

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

Admiral Formation The Admiral Formation is a geologic formation in Texas. It preserves fossils dating back to the Permian period. See also * List of fossiliferous stratigraphic units in Texas * Paleontology in Texas Paleontology in Texas refers to paleontologic ...

Belle Plains Formation The Belle Plains Formation is a geologic formation in Texas. It preserves fossils dating back to the Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period ...

Wichita Group The Wichita Group is a geologic group in the Texas Red Beds. It preserves fossils dating back to the Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period ...

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to its ...

Paleobiology

''Ophiacodon'' most likely lived on land, but paleontologists have sometimes thought that it was semi-aquatic. An aquatic habitat for ''Ophiacodon'' was first proposed by paleontologist

E. C. Case Ermine Cowles Case (1871–1953), invariably known as E.C. Case, was a prominent American paleontologist in the second generation that succeeded Othniel Charles Marsh and Edward Drinker Cope. A graduate of the University of Kansas, with a PhD f ...

in 1907, although he later dismissed the idea. Anatomical features suggesting that it spent much of its time in the water include broad claws that seemed to be adaptations for paddling, thin jaws and numerous small teeth that seemed to be adapted for eating fish, and weakly developed bones, which are seen in many other secondarily aquatic tetrapods. In 1940, paleontologists

Alfred Romer Alfred Sherwood Romer (December 28, 1894 – November 5, 1973) was an American paleontologist and biologist and a specialist in vertebrate evolution. Biography Alfred Romer was born in White Plains, New York, the son of Harry Houston Romer an ...

and Llewellyn Ivor Price proposed that hindlimbs with a greater length than forelimbs was another aquatic adaptation of ''Ophiacodon'', supposedly because the hindlimbs would have been used to propel it through water. Several of these features are no longer thought to be evidence of an aquatic lifestyle; for example, broad claws are seen in most early tetrapods, even those that are known to have been almost exclusively terrestrial, and the long hindlimbs of ''Ophiacodon'' would not have been an effective means of propulsion because the feet were still relatively small and had little surface area over which to form a paddle. Analysis of the vertebrae of ''Ophiacodon'' indicate that it was most likely terrestrial and spent little time in water. A paleobiological inference model for the femur likewise suggests a terrestrial lifestyle for ''Ophiacodon'', even though the rather thick cortex might also suggest amphibious, rather than truly terrestrial habits. Skeletons of ''Ophiacodon'' show a fast growth pattern called fibrolamellar bone (FLB), suggesting at least partial warm-bloodedness. The FLB pattern is also found in birds and mammals.

References

{{Taxonbar, from=Q284818 Ophiacodontids Prehistoric synapsid genera Carboniferous synapsids Cisuralian synapsids of Europe Cisuralian synapsids of North America Carboniferous North America Permian North America Pennsylvanian genus first appearances Cisuralian genus extinctions Taxa named by Othniel Charles Marsh Fossil taxa described in 1878