Definition of "therapsid" []

• Any of various reptiles of the order Therapsida of the Permian and Triassic periods, many of which are considered to be direct ancestors of mammals. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Descended from creatures called therapsid reptiles, bats first took flight in the Triassic period more than two hundred million years ago."
• "My first therapsid drawings were downright atrocious."
• "His book “From the Beginning” was also a surprisingly detailed introduction to extinct fish, reptile, and therapsid art."