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单词 Ophiacodontia
释义

Ophiacodontia

英语百科

Synapsid

Eothyris, an early synapsid with multiple canines
The sea otter has the densest fur of modern mammals.
Sail-back pelycosaurs like Edaphosaurus indicate an early trend toward temperature regulation in synapsids.

Synapsids (Greek, 'fused arch'), synonymous with theropsids (Greek, 'beast-face'), are a group of animals that includes mammals and every animal more closely related to mammals than to other living amniotes. They are easily separated from other amniotes by having a temporal fenestra, an opening low in the skull roof behind each eye, leaving a bony arch beneath each; this accounts for their name. Primitive synapsids are usually called pelycosaurs or pelycosaur-grade synapsids; more advanced mammal-like ones, therapsids. The non-mammalian members are described as mammal-like reptiles in classical systematics; they can also be called stem mammals or proto-mammals. Synapsids evolved from basal amniotes and are one of the two major groups of the later amniotes; the other is the sauropsids, a group that includes modern reptiles and birds. The distinctive temporal fenestra developed in the ancestral synapsid about 312 million years ago, during the Late Carboniferous period.

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