Source : Webster's Revised Unabridged Dictionary (1913)

Rhynchocephala \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}.

Source : WordNet®

Rhynchocephalia
     n : tuataras; extinct forms from middle Triassic [syn: {order
         Rhynchocephalia}]