Bauriidae is an extinct

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

therocephalia Therocephalia is an extinct suborder of eutheriodont therapsids (mammals and their close relatives) from the Permian and Triassic. The therocephalians ("beast-heads") are named after their large skulls, which, along with the structure of their ...

therapsid Therapsida is a major group of eupelycosaurian synapsids that includes mammals, their ancestors and relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including limbs that were oriented more ...

s. Bauriids were the latest-surviving group of therocephalians after the

Permian–Triassic extinction event The Permian–Triassic (P–T, P–Tr) extinction event, also known as the Latest Permian extinction event, the End-Permian Extinction and colloquially as the Great Dying, formed the boundary between the Permian and Triassic geologic periods, as ...

, going extinct in the

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy. The Middle Triassic spans the time between Ma and ...

. They are among the most advanced eutherocephalians and possess several mammal-like features such as a

secondary palate The secondary palate is an anatomical structure that divides the nasal cavity from the oral cavity in many vertebrates. In human embryology, it refers to that portion of the hard palate that is formed by the growth of the two palatine shelves medi ...

and wide postcanine teeth at the back of the jaws (analogous to mammalian

molars The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone to ...

). Unlike other therocephalians, bauriids were

herbivorous A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpar ...

. They were also smaller than earlier members of the group. Two subfamilies are classified within Bauriidae: Nothogomphodontinae and Bauriinae.

Description

Bauriids have a dentition characteristic of herbivores with the exception of '' Nothogomphodon''. There are four incisors on either side of the upper jaw. Like other therocephalians, bauriids have moderately enlarged canines. The postcanine teeth behind the canines are broad. The postcanines of the upper and lower jaw fit tightly together as an adaptation to processing plant material. An

autapomorphy In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to ...

or unique feature of Bauriidae is the expansion of the dentary bone of the lower jaw inward toward the jaw midline, forming a wide shelf of bone to either side of the tooth row. A similar expansion of the

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates 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. T ...

in the upper jaw is also seen in bauriids, although it is not unique to the group as the feature has also evolved in a group of cynodont therapsids called gomphodonts (which, like bauriids, were herbivorous).

Phylogeny

Bauriids belong to a large clade or evolutionary grouping of therapsids called Therocephalia that is closely related to mammals (mammals are part of Cynodontia, the

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 ...

of Therocephalia in most studies). Within Therocephalia, bauriids are part of a subgroup called Eutherocephalia, which includes all but the most basal therocephalians. Nested within Eutherocephalia is a clade called Baurioidea, of which bauriids are the most derived members (baurioids that fell outside Bauriidae were traditionally all placed within a group called Scaloposauria, but the group is now thought to be a paraphyletic assemblage of basal baurioids). The inter-group relationships of Bauriidae are uncertain. Battail and Surkov (2003) split it into two subfamilies: Nothogomphodontinae, which included the genus ''Nothogomphodon''; and Bauriinae, which included all other bauriids. In his

phylogenetic analysis 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 ...

of therocephalians, Huttenlocker (2014) found support for ''Nothogomphodon'' being more basal than other bauriids, but also found a clade containing '' Ordosiodon'' and '' Hazhenia'' (Chinese therocephalians that had previously been grouped together under the family

Ordosiidae ''Ordosia'' is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived from 501 to 490 million years ago during the Dresbachian faunal stage of the late Cambrian Period The Cambrian Period ( ; sometime ...

) to be the sister group of these other bauriids, with ''Nothogomphodon'' occupying a more basal position. Huttenlocker therefore restricted the name Bauriidae to the sister group of Ordosiidae. The

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 ...

below is modified from Huttenlocker (2014), showing the position of Bauriidae within Therocephalia and the interrelationships of bauriids supported by his analysis:

References

External links

Bauriidae
in the

Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database (PBDB) originated in the NCEAS-funded Phanerozoic Marine Pale ...

{{Taxonbar, from=Q4873580 Permian first appearances Middle Triassic extinctions Prehistoric therapsid families