Dromatheriidae

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 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.