''Scapanops'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

dissorophid Dissorophidae is an extinct family of medium-sized, temnospondyl amphibians that flourished during the late Carboniferous and early Permian periods. The clade is known almost exclusively from North America. History of study Dissorophidae is a ...

temnospondyl Temnospondyli (from Greek language, Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') is a diverse order (biology), order of small to giant tetrapods—often considered Labyrinthodontia, primitive amphi ...

amphibian known from 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), 01'' (Richard Müller album), 2001 * 01 (Son of Dave album), ''01'' (Son of Dave album), 2000 * 01 (Urban ...

Nocona Formation of north-central

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 ...

, United States. It contains only 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 ...

''Scapanops neglecta'', which was named by Rainer R. Schoch and Hans-Dieter Sues in

2013 File:2013 Events Collage V2.png, From left, clockwise: Edward Snowden becomes internationally famous for leaking classified NSA wiretapping information; Typhoon Haiyan kills over 6,000 in the Philippines and Southeast Asia; The Dhaka garment fact ...

. ''Scapanops'' differs from other dissorophids in having a very small

skull table The skull roof, or the roofing bones of the skull, are a set of bones covering the brain, eyes and nostrils in bony fishes and all land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium. In comparati ...

, which means that its eye sockets are unusually close to the back of the skull. The eye sockets are also very large and spaced far apart. ''Scapanops'' was probably small-bodied (around long) with a proportionally large head and short trunk and tail. Like other dissorophids, it probably spent most of its life on land.

Description

The only known skull of ''Scapanops'' is long. ''Scapanops'' is distinguished from other dissorophids by five unique features or autapomorphies: a large spacing between the orbits or eye sockets, giving the skull an oval-shaped outline; a very small skull table behind the orbits; a long snout twice as long as the skull table and proportionally longer than that of any other dissorophid; a jaw joint (the

quadrate Quadrate may refer to: * Quadrate bone * Quadrate (heraldry) * Quadrate lobe of liver * Quadrate tubercle The quadrate tubercle is a small tubercle found upon the upper part of the femur. It serves as a point of insertion of the quadratus femori ...

condyle) positioned farther forward on the skull than it is in other dissorophids; and a

skull roof The skull roof, or the roofing bones of the skull, are a set of bones covering the brain, eyes and nostrils in bony fishes and all land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium. In comparati ...

that is covered in small ridges, but not pits as in most other dissorophids. It shares several features (

synapomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...

) with the dissorophids ''

Conjunctio ''Conjunctio'' is an extinct genus of dissorophid temnospondyl amphibian from the early Permian of New Mexico. The type species, ''Conjunctio multidens'', was named by paleontologist Robert L. Carroll in 1964. History of study The holotype spe ...

'' and '' Cacops'', including and bony plates called

osteoderm Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct amp ...

s that are fused to the

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...

e. The osteoderms form a single row along the back. ''Scapanops'' and ''Conjunctio'' both have numerous small teeth lining their jaws, suggesting that they ate small prey. Other closely related dissorophids have fewer and larger teeth, meaning that they probably ate larger prey.

Discovery

''Scapanops'' is known from a single

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

specimen from the Nocona Formation, which is part of the Early Permian red beds of Texas. It includes most of the skull as well as the

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

, and

clavicle The clavicle, or collarbone, is a slender, S-shaped long bone approximately 6 inches (15 cm) long that serves as a strut between the shoulder blade and the sternum (breastbone). There are two clavicles, one on the left and one on the rig ...

bones, which are preserved underneath the skull. Several vertebrae, ribs, and osteoderms are also known. The fossil, now housed in the Museum of Comparative Zoology at Harvard University, was discovered by American paleontologist Alfred Romer on April 15, 1950 and was first mentioned in the scientific literature by paleontologist

Robert L. Carroll Robert "Bob" Lynn Carroll (May 5, 1938 – April 8, 2020) was an American–Canadian vertebrate paleontologist who specialised in Paleozoic and Mesozoic amphibians and reptiles. Biography Carroll was an only child and grew up on a farm near ...

in 1964. During this time it was thought to belong to the species '' Conjunctio multidens''. In 2013 the specimen was recognized to belong to a separate genus, which was named ''Scapanops'' after the spade-like shape of its skull (from the Greek ''skapane''). The suffix -''ops'' is meant to associate it with the genus '' Cacops'', a closely related dissorophid. The specific name ''neglecta'' references the neglected status of the holotype specimen after its initial description in 1964.

Relationships

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

analysis of dissorophids published in 2013 found ''Scapanops'' to be 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 ...

members of a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

called

Eucacopinae Eucacopinae is an extinct clade (evolutionary grouping) of dissorophid temnospondyls. Eucacopines differ from the other main group of dissorophids, the Dissorophinae, in having more lightly built skeletons and more knobby skulls. The subfamily w ...

. Eucacopines are characterized by their lightly built skeletons and knobby skulls. The most basal eucacopine was found to be ''Conjunctio'' while ''Scapanops'' was positioned close to a

derived Derive may refer to: * Derive (computer algebra system), a commercial system made by Texas Instruments * ''Dérive'' (magazine), an Austrian science magazine on urbanism *Dérive, a psychogeographical concept See also * *Derivation (disambiguatio ...

clade of eucacopines that includes the genus '' Cacops'' (which is also from the Early Permian of the southwestern United States) and the Russian genera ''

Zygosaurus ''Zygosaurus'' is an extinct genus of dissorophid temnospondyl from the Middle-Late Permian of Russia. It was described in 1848 by Eduard Eichwald, making it the first dissorophid to be described and is known from a single species, ''Zygosaurus ...

'' and '' Kamacops''. While members of the derived eucacopine clade have two rows of osteoderms down their backs, ''Scapanops'' and ''Conjunctio'' have only a single row of osteoderms down their backs. A single row of osteoderms is thought to be the ancestral condition for the dissorophid clade including Eucacopinae and its

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

Dissorophinae Dissorophinae is a subfamily of dissorophid temnospondyl Temnospondyli (from Greek language, Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') is a diverse order (biology), order of small to giant t ...

. Like the derived eucacopines, dissorophines also have two rows of osteoderms, meaning that the feature evolved independently in both groups and that ''Scapanops'' represents the point in eucacopine evolution before the two rows of osteoderms appeared. Below is a cladogram from the 2013 analysis:

References

{{Taxonbar, from=Q16758534 Dissorophids Cisuralian temnospondyls of North America Permian geology of Texas Fossil taxa described in 2013 Prehistoric amphibian genera