Cynodonts

Part of speech: noun

Definitions

1. A group of advanced synapsids that lived during the late Permian and Triassic periods, possessing features that foreshadow mammals
2. Extinct members of the clade Cynodontia, characterized by dental adaptations and possibly warm-blooded traits, leading to mammalian evolution
3. An ancient lineage of vertebrates known for their mammal-like characteristics, including specialized teeth and skeletal structures indicative of early mammalian traits

Etymology: Cynodonts, as the word is used, belong to the same lineage that produced mammals, and the name itself is a Greek compound: "kyon" (dog) and "odous" (tooth), a reference to the dog-like teeth of the earliest members, with their distinct canines and cheek teeth. Paleontologists coined the term in the 19th century for this group of therapsids, the mammal-like reptiles of the Permian and Triassic. The most striking detail is that these animals were not mammals by the usual definition, yet they show the transition clearly. Their jaws gradually reorganized, with the lower jaw bone enlarging while the bones behind it shrank, and some of the small bones there migrated into the middle ear. Many also had secondary palates, letting them breathe while chewing, which suggests a high metabolic rate. Because the group changed so gradually, the boundary between cynodonts and mammals is drawn by convention rather than by any single dramatic event. The word is therefore a label for a sliding scale of features rather than a sharply defined creature.