What are the Differences Between Synapsids and Sauropsids?
Synapsids include mammals and our distant ancestors, including pelycosaurs and therapsids, while sauropsid is another word for reptiles. Synapsid means “fused arch,” a reference to skull structure. Another name for a synapsid is theropsid, which means “beast face,” in contrast to sauropsid, which means “lizard face.” Synapsids are sauropsids are the two evolutionary lineages of amniotes, which includes all non-amphibians tetrapods and their descendants (such as whales, which descended from tetrapods but lost their legs when they became exclusively marine). Early synapsids used to be called “mammal-like reptiles,” but this is a misnomer, as they were not reptiles at all. Synapsids and sauropsids split off from each other approximately 320 million years ago, during the late Carboniferous period. Both looked like small lizards. At the time, tetrapods had existed in the water for about 45 million years, and on land for at least 20 million years. Both are amniotes, that is animals with comp
