Angielczyk, Kenneth D. Department of Geology, Field Museum of Natural History, Chicago, Illinois.
Last reviewed:December 2019
- General appearance
- Life history and growth
- Feeding system
- Taxonomic diversity and mass extinctions
- Related Primary Literature
- Additional Reading
A group of extinct nonmammalian therapsids (Synapsida), often termed “mammal-like reptiles.” Living mammals belong to a larger group of tetrapods called Synapsida. The synapsid lineage is more than 300 million years old and includes numerous extinct animals that document the evolution of mammals from an ancient, lizardlike ancestor. Extinct nonmammalian synapsids are sometimes called “mammal-like reptiles,” but all are more closely related to mammals than to any reptile. One of the most successful of these nonmammalian synapsid groups is Dicynodontia. Dicynodonts were herbivores known from the Middle Permian Period of Earth history [approximately 265 million years ago (MYA)] to at least the Late Triassic Period (approximately 215 MYA); a fragmentary specimen from Australia may imply that they survived until the Early Cretaceous (approximately 105 MYA). Although dicynodonts are not directly ancestral to mammals, they are important because they were major components of Permo-Triassic terrestrial ecosystems and survivors of the largest mass extinction. See also: Animal evolution; Mammalia; Permian; Reptilia; Synapsida; Therapsida; Triassic
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