Tritylodontidae

Tritylodonts Temporal range: 221–113 Ma PreЄ Є O S D C P T J K Pg N Late Triassic - Early Cretaceous
Life restoration of Oligokyphus
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Order:	Therapsida
Suborder:	Cynodontia
Clade:	Mammaliamorpha
Family:	†Tritylodontidae Cope, 1884
Genera
See below

See below

Tritylodontids ("three knob teeth", named after the shape of animal's teeth) were small to medium-sized, highly specialized and extremely mammal-like cynodonts, bearing several mammalian hallmarks like erect limbs, endothermy and lactation. They were the last known family of the non-mammalian synapsids. One of the last cynodont lines to appear, the Tritylodontidae descended from a Cynognathus-like cynodont. The tritylodontids were herbivorous, chewing through vegetation, such as stems, leaves, and roots, though recent studies indicate some may have had more omnivorous diets. Tritylodontid fossils are found in the Americas, South Africa, and Eurasia - they appear to have had an almost global distribution, including Antarctica.

The tritylodont's skull had a high flat crest. They retained the reptilian joint between the quadrate bone of the skull and the articular bone of the lower jaw, but they were reduced. It is only through the retention of the vestigial reptilian jawbones that they are technically regarded to not be mammals. The back of the skull had huge zygomatic arches for the attachment of its large jaw muscles. They also had a very well-developed secondary palate. The tritylodont dentition was very different from that of other cynodonts. They did not have canines. The front pair of incisors were enlarged and were very similar to rodents of today. Tritylodontids had a large gap, the diastema, that separated the incisors from the square-shaped cheek. Each of the cheek teeth in the upper jaw had three rows of cusps running along its length that had grooves in between. The lower teeth had two rows of cusps which fitted into the grooves in the upper teeth. The matching of the cusps allowed the teeth to occlude more precisely than in most earlier cynodonts. It would grind its food between the teeth in somewhat the same way that a modern rodent would with their food, though unlike rodents tritylodontids had a palinal jaw stroke (front-to-back), instead of a propalinal one (back-to-front). The teeth were well suited for shredding plants matter; however, there is evidence that some tritilodontids had more omnivorous diets, much in the same vein as modern mammals with "herbivore dentitions" like modern rats.