Gomphodontia is 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, ...

cynognathia Cynognathia ("dog jaw") is one of two major clades of cynodonts, the other being Probainognathia. Cynognathians included the large carnivorous genus ''Cynognathus'' and the herbivorous traversodontids. Cynognathians can be identified by several ...

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 that includes the families Diademodontidae,

Trirachodontidae Trirachodontidae is an extinct, possibly paraphyletic family of cynognathian cynodonts from the Triassic of China and southern Africa. Trirachodontids appeared during the Early Triassic soon after the Permian-Triassic extinction event and quickl ...

, and

Traversodontidae Traversodontidae is an extinct family of herbivorous cynodonts. Traversodonts were primarily Gondwanan, with many species known from Africa and South America. Recently, traversodonts have also been found from Europe and eastern North America. Tra ...

. Gomphodonts are distinguished by wide and closely spaced molar-like postcanine teeth, which are convergent with those of mammals. Other distinguishing characteristics of gomphodonts include deep

zygomatic arch In anatomy, the zygomatic arch, or cheek bone, is a part of the skull formed by the zygomatic process of the temporal bone (a bone extending forward from the side of the skull, over the opening of the ear) and the temporal process of the zygomati ...

es, upper postcanines with three or more cusps spanning their widths and lower postcanines with two cusps spanning their widths. Gomphodonts first appeared in the

Early Triassic The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which is a un ...

and became extinct at the end of 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 ...

. Fossils are known from southern Africa, Argentina and southern Brazil (Paleorrota geopark), eastern North America, Europe, China, and Antarctica. Gomphodontia was first named by paleontologist

Harry Seeley Harry Govier Seeley (18 February 1839 – 8 January 1909) was a British paleontologist. Early life Seeley was born in London on 18 February 1839, the second son of Richard Hovill Seeley, a goldsmith, and his second wife Mary Govier. When his fat ...

in 1895. He considered it an order of wide-toothed therapsids (then called

anomodont Anomodontia is an extinct group of non-mammalian therapsids from the Permian and Triassic periods. By far the most speciose group are the dicynodonts, a clade of beaked, tusked herbivores.Chinsamy-Turan, A. (2011) ''Forerunners of Mammals: Ra ...

s) from South Africa, distinct from Cynodontia. By the 1930s Gomphodontia was considered a suborder of Cynodontia and included the families Diademodontidae, Trirachodontidae, Traversodontidae, and

Tritylodontidae Tritylodontidae ("three-knob teeth", named after the shape of their cheek teeth) is an extinct family of small to medium-sized, highly specialized mammal-like cynodonts, bearing several mammalian traits like erect limbs, endothermy and detail ...

. These four families have also been grouped in the superfamily Traversodontoidea, named by paleontologist

Edward Drinker Cope Edward Drinker Cope (July 28, 1840 – April 12, 1897) was an American zoologist, paleontologist, comparative anatomist, herpetologist, and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested ...

in 1884. Tritylodontoidea has occasionally replaced Gomphodontia in various cynodont taxonomies. In 2001 Gomphodontia was defined as a stem-based clade including all cynodonts more closely related to ''

Exaeretodon ''Exaeretodon'' is an extinct genus of fairly large, low-slung traversodontid cynodonts from the southern parts of Pangea. Four species are known, from various formations. ''E. argentinus'' is from the Carnian-age (Late Triassic) Cancha de Boch ...

'' than to ''

Cynognathus ''Cynognathus'' is an extinct genus of large-bodied cynodontian therapsids that lived in the Middle Triassic. It is known from a single species, ''Cynognathus crateronotus''. ''Cynognathus'' was a long predator closely related to mammals and ha ...

''. This placed it within the larger clade

Cynognathia Cynognathia ("dog jaw") is one of two major clades of cynodonts, the other being Probainognathia. Cynognathians included the large carnivorous genus ''Cynognathus'' and the herbivorous traversodontids. Cynognathians can be identified by several ...

, one of the two main groups of eucynodonts (the other being

Probainognathia Probainognathia is one of the two major subgroups of the clade Eucynodontia, the other being Cynognathia. The earliest forms were carnivorous and insectivorous, though some groups eventually also evolved herbivorous diets. The earliest and most ...

). Since then most studies have removed Tritylodontidae from Gomphodontia and reclassified it within Probainognathia as a group more closely related to mammals than are the convergently similar gomphodonts. Tritylodontoidea has fallen into disuse while Gomphodontia continues to be used in many studies.

Cladogram

Below is a

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...

from Ruta, Botha-Brink, Mitchell and Benton (2013) showing one hypothesis of gomphodont relationships:

References

{{Taxonbar, from=Q5581262 Cynognathians Early Triassic first appearances Late Triassic extinctions