''Ambedus'' is an extinct

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 possible

diadectid Diadectidae is an extinct family of early tetrapods that lived in what is now North America and Europe during the Late Carboniferous and Early Permian, and in Asia during the Late Permian. They were the first herbivorous tetrapods, and also the f ...

reptiliomorph Reptiliomorpha (meaning reptile-shaped; in PhyloCode known as ''Pan-Amniota'') is a clade containing the amniotes and those tetrapods that share a more recent common ancestor with amniotes than with living amphibians (lissamphibians). It was defi ...

. Fossils have been found 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 (Urban Zakapa album), ''01'' (Urban Zakapa album), 2011 * ''01011 ...

Dunkard Group of Monroe County,

Ohio Ohio ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Erie to the north, Pennsylvania to the east, West Virginia to the southeast, Kentucky to the southwest, Indiana to the ...

. 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. pusillus'' was named in 2004. The genus name comes from the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

word ''ambedo'' meaning "to nibble", in reference to its herbivorous diet. The specific name ''pusillus'' means "tiny" in Latin.

Description

''Ambedus'' is a small tetrapod, possible Diadectid, known only from

maxilla In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...

e and

dentary 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 ...

bones. It is usually considered the most primitive diadectid because unlike other forms it had a small, shallow lower jaw and many simple, conical teeth. It was also smaller than the later, rather bulky diadectids. Later diadectids have deep jaws with few teeth and forward-projecting incisiforms at the tips of the jaws for consuming plant material, and a corresponding greater girth.

Phylogeny

David Berman's 2013 paper argued against the inclusion of Ambedus in Diadectidae. He stated in his paper that its assignment to Diadectidae is based only on several isolated maxillae and dentaries containing cheek teeth that only exhibited a resemblance in their molar-like morphology to those in Diadectids. There are also a number of other characteristics that distinguish Ambedus from all other Diadectids, such as a shallow rather than deep deep dentary, and relatively high maxillary and dentary tooth counts, among other characteristics that distinguish them from Diadectids. Furthermore, the appearance of Ambedus pusillus so late in the fossil record, after all known Diadectomorphs have died out, also casts a doubt on the fact that it is supposed to represent the basalmost member of the Diadectid lineage. In contrast, the first Diadectids from the Upper Pennsylvanian were way more developed and had the characteristic dentary and maxillary features of the Diadectid lineage. This implicates that there should be a ghost lineage that goes back all the way back to the Middle Pennsylvanian, which is highly unlikely according to Berman.

Paleobiology

The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

specimen of ''Ambedus'' was found from an outcrop of the Early Permian the

Greene Formation Greene Formation is a geologic formation located in Ohio, West Virginia and Pennsylvania that has been dated to the Seymouran Land-vertebrate faunachron, Land-Vertebrate Faunachron of the Early Permian. It is the youngest formation within the Dunk ...

on Clark Hill in Monroe County, Ohio. It was found alongside fossils of the

lungfish Lungfish are freshwater vertebrates belonging to the class Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, inc ...

'' Sagenodus'', the

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 ...

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 ...

Trimerorhachis ''Trimerorhachis'' is an extinct genus of dvinosaurian temnospondyl within the family (biology), family Trimerorhachidae. It is known from the Early Permian of the southwestern United States, with most fossil specimens having been found in the Re ...

'', an

embolomere Embolomeri is an order of tetrapods or stem-tetrapods, possibly members of Reptiliomorpha. Embolomeres first evolved in the Early Carboniferous ( Mississippian) Period and were the largest and most successful predatory tetrapods of the Late Carbon ...

reptiliomorph, and the

synapsid Synapsida is a diverse group of tetrapod vertebrates that includes all mammals and their extinct relatives. It is one of the two major clades of the group Amniota, the other being the more diverse group Sauropsida (which includes all extant rept ...

Ctenospondylus ''Ctenospondylus'' ("comb vertebra") is an extinct genus of sphenacodontid synapsid. Species were about three meters (ten feet) long. The genus is known only from the 'Seymouran' Land Vertebrate Faunachron, which is equivalent to the upper part ...

''. These animals likely lived alongside a freshwater lake or pond.

References

{{Taxonbar, from=Q2841993 Diadectidae Artinskian genera Kungurian genera Cisuralian tetrapods of North America Permian Ohio Paleontology in Ohio Fossil taxa described in 2004 Taxa named by Robert R. Reisz