from
The Collaborative International Dictionary of English v.0.48
Mosasauria \Mos`a*sau"ri*a\, n. pl. [NL. See {Mosasaurus}.]
(Paleon.)
An order of large, extinct, marine reptiles, found in the
Cretaceous rocks, especially in America. They were
serpentlike in form and in having loosely articulated and
dilatable jaws, with large recurved teeth, but they had
paddlelike feet. Some of them were over fifty feet long. They
are, essentially, fossil sea serpents with paddles. Called
also {Pythonomarpha}, and {Mosasauria}.
[1913 Webster]