therapsid

American  

[thuh-rap-sid] / θəˈræp sɪd /

noun

1. any of various groups of mammallike reptiles of the extinct order Therapsida, inhabiting all continents from mid-Permian to late Triassic times, some of which were probably warm-blooded and directly ancestral to mammals.

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adjective

1. of or relating to the Therapsida.

therapsid British  

/ θəˈræpsɪd /

noun

1. any extinct reptile of the order Therapsida, of Permian to Triassic times: considered to be the ancestors of mammals

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therapsid Scientific  

/ thə-răp′sĭd /

1. Any of a group of amniotes that emerged in the Permian Period. Therapsids developed differentiated dentition, with nipping, biting, and crushing teeth, and (unlike diapsids) had forelimbs that were more greatly developed than hindlimbs. Therapsids include the so-called mammallike reptiles of the Permian and Triassic Periods, as well as mammals.

2. Compare anapsid diapsid synapsid

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Etymology

Origin of therapsid

< New Latin Therapsida (1905), equivalent to Greek thēr- (stem of thḗr wild beast) + apsid- (stem of apsís arch, vault, referring to the temporal arch of the skull) + New Latin -a neuter plural ending ( -a ¹ )

Example Sentences

In 2023, one of the oldest fossils of a therapsid was discovered in South Africa, which is where “Mammal Origins” spends much of its time.

From The Wall Street Journal • Feb. 10, 2026

The therapsid masseter, as an external muscle unhindered by the crowding of surrounding organs, was readily available for the many modifications that have been achieved among the mammals.

From The Adductor Muscles of the Jaw In Some Primitive Reptiles by Fox, Richard C.