1. Plural of pelycosaur; an extinct group of large carnivorous and herbivorous reptiles that lived during the Carboniferous and Permian periods, characterized by a sail-like structure on the back formed by elongated vertebral spines.
Usage: paleontology; plural form; also called synapsids in broader classification

Examples

• Pelycosaurs were among the dominant predators of the Permian period.
• The distinctive sail on the back of some pelycosaurs may have been used for thermoregulation or display.
• Dimetrodon is one of the most well-known pelycosaurs found in fossil records.
• Pelycosaurs are considered important ancestors in the evolutionary line leading to mammals.
• Museum exhibits often feature skeletal reconstructions of various pelycosaurs.