\Di`no*sau"ri*a\, n. pl. [NL., fr. Gr. ? terrible + ?
lizard.] (Paleon.)
An order of extinct mesozoic reptiles, mostly of large size
(whence the name). Notwithstanding their size, they present
birdlike characters in the skeleton, esp. in the pelvis and
hind limbs. Some walked on their three-toed hind feet, thus
producing the large ``bird tracks,'' so-called, of mesozoic
sandstones; others were five-toed and quadrupedal. See
Illust. of {Compsognathus}, also Illustration of Dinosaur in
Appendix.