''Arctotraversodon'' is an extinct

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 ...

of traversodontid

cynodont The cynodonts () (clade Cynodontia) are a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 mya), and extensively diversified after the Permian–Triassic extinction event. Cynodonts had a wide variety ...

s from the

Late Triassic The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch ...

of Canada. Fossils first described from the

Wolfville Formation The Wolfville Formation is a Triassic geologic formation of Nova Scotia. The formation is of Carnian to early Norian age. Fossils of small land vertebrates have been found in the formation, including procolophonid and early archosauromorph reptile ...

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 Eng ...

in 1984 represented the first known traversodontid from North America.Hopson, J.A. (1984). Late Triassic traversodont cynodonts from Nova Scotia and southern Africa. ''Palaeontologia Africana'' Vol. 25; 181-201. 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. * Ty ...

and only species is ''A. plemmyridon'' and is represented by teeth and several

dentary bone In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

Description and history

''Arctotraversodon'' was first tentatively placed in the genus ''

Scalenodontoides ''Scalenodontoides'' is an extinct genus of traversodontidae, a family of herbivorous cynodonts. It lived during the Late Triassic in what is now South Africa. Its type species is ''Scalenodontoides macrodontes''. It was named in 1957 by A. W. Cr ...

'' as a new species, ?''Scalenodontoides plemmyridon''. Only dentary bones and a few teeth were known when it was first named. Postcanine teeth, the primary diagnostic material of most traversodontids, were not known for ?''S. plemmyridon''. Few available features could diagnose ?''S. plemmyridon'' as its own species, but the bones and teeth were clearly different from those of other traversodontids. A traversodontid postcanine tooth was later found from the same formation that was distinct from those of all other species. Unlike other traversodontid lower postcanines which have two cusps on either side of their crowns, these teeth had three cusps. The traversodontid ''

Boreogomphodon ''Boreogomphodon'' is an extinct genus of traversodontid cynodonts from the Late Triassic of the eastern United States. Fossils have been found from the Turkey Branch Formation in Virginia. Description and history ''Boreogomphodon jeffersoni'' w ...

'' from the Turkey Branch Formation of

Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth ar ...

was later found to have three cusps on its lower postcanines, showing that North American traversodontids were distinct from those in Africa and South America. The species was assigned to its own genus, ''Arctotraversodon'', in 1992. ''Arctotraversodon'' means "northern ''Traversodon''" in reference to its northern location and close relation with ''Traversodon''. "Arcto" (from the Greek ''arktos'') can also mean "bear", as the

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 was once informally called the "bear jaw." Features of an upper postcanine tooth that was found on a sea cliff in Nova Scotia were used to diagnose the new genus.

References

Traversodontids Prehistoric cynodont genera Late Triassic synapsids Triassic synapsids of North America Fossil taxa described in 1992 Taxa named by Hans-Dieter Sues Taxa named by Neil Shubin {{paleo-therapsid-stub