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''Adamanterpeton (''from
Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...
: Αδάμαντας ''adamantas,'' meaning 'diamond' and
Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...
: ἑρπετόν ''herpetón'', meaning 'creeping thing') is a
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of
Edopoid Edopoidea is a clade of primitive temnospondyl amphibians including the genus ''Edops'' and the family Cochleosauridae. Edopoids are known from the Late Carboniferous and Early Permian of North America and Europe, and the Late Permian of Africa. ...
Temnospondyl Temnospondyli (from Greek language, Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') or temnospondyls is a diverse ancient order (biology), order of small to giant tetrapods—often considered Labyrinth ...
within the
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Cochleosauridae. The
type species In International_Code_of_Zoological_Nomenclature, 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 spe ...
''A. ohioensis'' was named in 1998 and is currently the only known species within this genus. ''Adamanterpeton'' is rare in the Linton vertebrate assemblage, with other amphibians like ''
Sauropleura ''Sauropleura'' (meaning "lizard side") is an extinct genus of nectridean tetrapodomorphs within the family Urocordylidae The Urocordylidae are an extinct family (biology), family of nectridean lepospondyl amphibians. Urocordylids lived during ...
'', ''
Ophiderpeton ''Ophiderpeton'' (from , 'snake' and 'creeper') is an extinct genus of aistopod tetrapodomorphs from the early Carboniferous to the early Permian. Remains of this genus are widespread and were found in Ohio, United States, Ireland, and the Cz ...
'', and '' Colosteus'' being more common. Unlike other Linton vertebrates, ''Adamanterpeton'' may have been adapted to a terrestrial lifestyle.


History and Discovery

The species is only known from two specimens in the fossil record. The cochleosaurid specimens were discovered in the fossil-rich
Allegheny Formation The Allegheny Group, often termed the Allegheny Formation, is a Pennsylvanian-age geological unit in the Appalachian Plateau. It is a major coal-bearing unit in the eastern United States, extending through western and central Pennsylvania, weste ...
of Linton, Ohio by
John Strong Newberry John Strong Newberry (December 22, 1822 – December 7, 1892) was an American physician, geologist and paleontologist. He participated as a naturalist and surgeon on three expeditions to explore and survey the western United States. During the C ...
, but were only formally described and figured by
Edward Drinker Cope Edward Drinker Cope (July 28, 1840 – April 12, 1897) was an American zoologist, paleontology, paleontologist, comparative anatomy, comparative anatomist, herpetology, herpetologist, and ichthyology, ichthyologist. Born to a wealthy Quaker fam ...
in 1875. Using Cope's (1875) work, Moodie (1916) attributed the specimens to '' Macrerpeton'' ''huxleyi,'' however, given that the holotype for ''M. huxleyi'' was well described and distinct from the two specimens this attribution was not recognized by future authors. In 1930,
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 ...
categorized the specimens as ''
Anthracosaurus ''Anthracosaurus'' is an extinct genus of embolomere that lived during the Late Carboniferous (around 315 million years ago) in what is now Scotland, England, and Ohio. Measuring around long, it was a large, aquatic eel-like predator. It has a ...
''. In 1947, Romer revised his previous classification and designated them as '' Leptophractus obsoletus''. However, instead of using the
type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * ...
specimen of ''L. obsoletus'' he used the two cochleosaurid specimens and erroneously classified ''L. obsoletus'' as small Temnospondyli belonging to the
Edopoidea Edopoidea is a clade of primitive temnospondyl amphibians including the genus ''Edops'' and the family Cochleosauridae. Edopoids are known from the Late Carboniferous and Early Permian of North America and Europe, and the Late Permian of Africa. ...
family. In 1963, Romer made revisions to what constituted the ''Anthracosaurus'' material from Linton, Ohio, and in doing so removed the two cochleosaurid specimens from its previous classification leaving them with no official
systematic Systematic may refer to: Science * Short for systematic error * Systematic fault * Systematic bias, errors that are introduced by an inaccuracy inherent to the system Economy * Systematic trading, a way of defining trade goals, risk control ...
status or classification. Hook and Baird (1986) identified them as '' Gaudrya'' ''latistoma'', however Sequeira & Milner (1993) disproved this classification. In their 1998 paper, Sequeira and Milner attempted to classify the cochleosaurid specimens and finding no similarities to existing cochleosaurid genera, considered them to be a
plesiomorphic In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorphy, apomorphy, an ...
stem Stem or STEM most commonly refers to: * Plant stem, a structural axis of a vascular plant * Stem group * Science, technology, engineering, and mathematics Stem or STEM can also refer to: Language and writing * Word stem, part of a word respon ...
cochleosaurid and named the corresponding genus ''Adamanterpeton'' and assigned the species name ''ohioensis'' to the type specimen.


Paleoenvironment and Geology

The species is only known from the Diamond coal mines of Linton, Ohio. Linton fossils are preserved in a coal deposit known as the Upper Freeport coal, which is a thin deposit of
cannel coal Cannel coal or candle coal is a type of bituminous coal, also classified as terrestrial type oil shale. Hutton(1987) Dyni (2006), pp. 3–4 Speight (2012), pp. 6–7 Due to its physical morphology and low mineral content cannel coal is considered ...
that lies beneath a locally thick layer of
bituminous coal Bituminous coal, or black coal, is a type of coal containing a tar-like substance called bitumen or asphalt. Its coloration can be black or sometimes dark brown; often there are well-defined bands of bright and dull material within the coal seam, ...
at the top of the Allegheny Group. The area was likely a
meander A meander is one of a series of regular sinuous curves in the Channel (geography), channel of a river or other watercourse. It is produced as a watercourse erosion, erodes the sediments of an outer, concave bank (cut bank, cut bank or river cl ...
of a larger river that was cut off, thus forming an
oxbow lake An oxbow lake is a U-shaped lake or stream pool, pool that forms when a wide meander of a river is meander cutoff, cut off, creating a free-standing body of water. The word "oxbow" can also refer to a U-shaped bend in a river or stream, whether ...
. A reduction in sediment deposits to the lake led to an increase in
peat Peat is an accumulation of partially Decomposition, decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, Moorland, moors, or muskegs. ''Sphagnum'' moss, also called peat moss, is one of the most ...
-forming
mire A peatland is a type of wetland whose soils consist of Soil organic matter, organic matter from decaying plants, forming layers of peat. Peatlands arise because of incomplete decomposition of organic matter, usually litter from vegetation, du ...
s which allowed for peat to directly accumulate over
sapropel Sapropel (a contraction of Ancient Greek words ''sapros'' and ''pelos'', meaning putrefaction and mud (or clay), respectively) is a term used in marine geology to describe dark-coloured sediments that are rich in organic matter. Organic carbon conc ...
found in abandoned channel segments, which is what eventually formed the coal deposits. The considerable depth of the lake was also thought to contribute to the extended length of time that the sapropelic conditions existed for in the area after the lake dried up. The area is thought to have produced somewhere between 200 and 300 Temnospondyl specimens, of which only two represent ''A. ohioensis'' effectively making it the rarest Temnospondyl and one of the rarer tetrapods from the assemblage. Milner and Sequeira (1998) attribute its scarcity in the Linton fauna to its terrestrial nature, suggesting it wasn't naturally found in this aquatic environment and was likely an accidental preservation. '' C. florensis'' was found in an assemblage in
Florence Florence ( ; ) is the capital city of the Italy, Italian region of Tuscany. It is also the most populated city in Tuscany, with 362,353 inhabitants, and 989,460 in Metropolitan City of Florence, its metropolitan province as of 2025. Florence ...
,
Nova Scotia Nova Scotia is a Provinces and territories of Canada, province of Canada, located on its east coast. It is one of the three Maritime Canada, Maritime provinces and Population of Canada by province and territory, most populous province in Atlan ...
that is considered similar to the Linton assemblage in terms of its depositional setting. Both ''C. florensis'' and ''A. ohioensis'' have relatively corrugated skulls that measure between 100 and 500 mm in length, a feature commonly associated with terrestrial Temnospondyls, which led Milner and Sequeira to hypothesize that the Cochleosaurid family included
amphibian Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...
s and small terrestrial
carnivore A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they ar ...
s.


Description

Both specimens only consist of a skull and lack any post cranial materials. The skulls of both specimens aren't fully preserved, however, the type specimen skull measures to be about 130 mm in length and the other specimen measuring around 120 mm. The honeycomb pattern produced from the pit-and-ridge system, that is characteristic of Temnospondyls, is also observed in ''Adamanterpeton''. However, this ornament pattern is significantly reduced in the area between the
anterior Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...
snout and the posterior
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, including land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium. In comparati ...
margin, and in the
lacrimals The lacrimal bones are two small and fragile bones of the facial skeleton; they are roughly the size of the little fingernail and situated at the front part of the medial wall of the orbit. They each have two surfaces and four borders. Several bon ...
and jugals, which is a pattern also observed in ''C. bohemicus'' and ''C. florensis''. The specimens also display a pattern where
ossified Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in t ...
struts extend from either side of the midline of the premaxilla, which then extend to the midline of the nasals and the frontals, and finish along the parietals. The struts are a feature considered to be characteristic of Cochleosaurids. Similar to '' Procochleosaurus, Adamanterpeton'' retains a pineal foramen unlike the other members of the ''Cochleosaurid'' family, where the pineal foramen is either completely closed or only open in juveniles. It is unknown whether the pineal foramen ever closes in their evolutionary history, however, the size of the foramen in both genera suggest that they do not and instead have the primitive condition found in tetrapods. The skull roof of the specimens were considered to be representative of the primitive Temnospondyl condition, either through direct observation of the features or through inference, which was necessary as regions of the
squamosal The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestra ...
and
quadratojugal The quadratojugal is a skull bone present in many vertebrates, including some living reptiles and amphibians. Anatomy and function In animals with a quadratojugal bone, it is typically found connected to the jugal (cheek) bone from the front and ...
were missing from both specimens. The palate is also considered to be representative of a primitive Temnospondyl, as it retains primitive features such as smaller interpterygoid vacuities, paired vomers, ectopterygoids and pterygoids. The vomers are elongated, in addition to an elongated prechoanal and interchoanal region, both of which can be associated with elongated
choana The choanae (: choana), posterior nasal apertures or internal nostrils are two openings found at the back of the nasal passage between the nasal cavity and the pharynx, in humans and other mammals (as well as crocodilians and most skinks). They ...
e, features that are all typical of cochleosaurid as well. The
parasphenoid The parasphenoid is a bone which can be found in the cranium of many vertebrates. It is an unpaired dermal bone which lies at the midline of the roof of the mouth. In many reptiles (including birds), it fuses to the endochondral (cartilage-derived ...
plate of the cranium is wider than it is long in ''Adamanterpeton'', similar to ''C. bohemicus''. It also contains three shallow depressions on its ventral surface that are thought to maybe be homologous with the parasphenoid tubera that are present in other edopoids. The
mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...
was relatively shallow and made up of the same bones typically observed in Temnospondyls, which is a feature also observed in '' Cochleosaurus and
Nigerpeton ''Nigerpeton'' (''Niger'', for the country, and ''herpeton'' (Greek), meaning crawler)Sidor, C.A., O’Keefe, F.R., Damiani, R., Steyer, J.S., Smith, R.M.H., Larsson, H.C.E., Sereno, P.C., Ide, O., Maga, A., 2005. Permian tetrapods from the Sahara ...
.'' This is contrasted with the ''Procochleosaurus'' condition where the mandible is deeper and more robust. They had simple, pointed teeth and fangs, that were implanted into the bone with the tooth socket remaining separate. Teeth were arranged in the typical Temnospondyl condition with three pairs of fangs on the palatal bones.


Classification

Adamanterpeton is classified as a stem '' Cochleosaurus,'' along with ''Procochleosaurus'' however, there is uncertainty about whether ''Adamanterpeton'' should be more stemward or ''Procochleosaurus'', as despite ''Adamanterpeton'' having all the Cochelosaurid character states it lacks the
apomorphies 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 hav ...
shared by more derived cochelosaurids. However, ''Procochleosaurus'' data is quite scarce, it is less than 50% complete, so its phylogenetic position remains ambiguous and up to interpretation. Despite the ambiguity of the order of the stem groups, there has been repeated support for a
monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...
Cochleosauridae family that consists of ''Procochleosaurus'' and ''Adamanterpeton'' as stem groups to the crown group that consists of ''Cochleosaurus, Nigerpeton'' and '' Chenoprosopus''. The characters that diagnose this family are thought to be pineal foramen closure, anteriorly broad choanae, extreme anterior vomerine elongation, jugal expansion on the palatal surface and are generally agreed upon by researchers, although there has been pushback against the inclusion of pineal foramen.


References

{{Taxonbar, from=Q4680106 Edopoidea Carboniferous temnospondyls of North America Fossil taxa described in 1998