CYNOGNATHUS

genus of extinct advanced mammallike reptiles found as fossils in Lower and Middle Triassic deposits in South Africa (those from 245 to 230 million years old). Cynognathus is representative of the Theriodontia, a group of therapsid (mammallike) reptiles that through time gave rise to the earliest mammals. Cynognathus was approximately as large as a modern wolf and, like the wolf, was an active predator. The body of Cynognathus was not massively constructed. The limbs were tucked well under and close to the body, providing the potential for rapid and efficient locomotion. The tail was long and well developed. The animal's skull was long and had openings for the attachment of strong muscles used in opening and closing the jaws. The lower jaw was dominated by the dentary bone; the other lower-jaw elements that are characteristic of reptiles were reduced and insignificant. The teeth were advanced in character; regional specialization of the dentition is evident, a mammalian feature. Incisors were present and adapted to nipping. These were followed by strongly developed canines, important features in predatory animals. Separated from the canines by a gap, or diastema, was a series of cheek teeth that sliced the animal's food into smaller, more easily swallowed particles. A well-developed secondary palate separated food passages from breathing passages. The vertebral column was well differentiated.