\Rhyn`cho*ceph"a*la\, n. pl. [NL., fr. Gr.
"ry`gchos snout + kefalh` head.] (Zo["o]l.)
An order of reptiles having biconcave vertebr[ae], immovable
quadrate bones, and many other peculiar osteological
characters. Hatteria is the only living genus, but numerous
fossil genera are known, some of which are among the earliest
of reptiles. See {Hatteria}. Called also {Rhynchocephalia}.