Dromatheriidae is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

family of

prozostrodontia Prozostrodontia is a clade of cynodonts including mammaliaforms and their closest relatives such as Tritheledontidae and Tritylodontidae. It was erected as a node-based taxon by Liu and Olsen (2010) and defined as the least inclusive clade contai ...

cynodont Cynodontia () is a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 Megaannum, mya), and extensively diversified after the Permian–Triassic extinction event. Mammals are cynodonts, as are their extin ...

s, closely related to mammals. Members of the family are known 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 a ...

( Carnian to Rhaetian) of

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and

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. Apart from a few jaw fragments, dromatheriids are mainly known from their sectorial (flesh-slicing) postcanine teeth. The teeth were fairly typical among early prozostrodontians, as they were labiolingually compressed (flattened sideways), with a single root and crown hosting a longitudinal row of sharp cusps. Dromatheriids in particular have a very narrow and symmetrical crown (when seen from above) without a prominent cingulum (a ridge or array of cuspules adjacent to the main cusps). Dromatheriid teeth on average have four main cusps, though some have as few as two ('' Dromatherium'') or three ('' Tricuspes''), or as many as six ('' Inditherium'', '' Pseudotriconodon''). Although the teeth have a single root, a vertical furrow on each side of the root appears to be a trait incipient towards the two fully divided roots of mammaliaforms. Making note of this condition, some authors have suggested that dromatheriids are a

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

group ancestral to mammaliaforms. Other studies instead consider the closest relatives of dromatheriids to be the " therioherpetids" '' Therioherpeton'' and '' Meurthodon'', which may even be placed within the family. However, the broader cusps of ''Therioherpeton'' and the divided root of ''Meurthodon'' dissuade their position within Dromatheriidae.

References

Prozostrodontia Prehistoric therapsid families {{Paleo-cynodont-stub