archaeopteryx

from WordNet (r) 3.0 (2006)

archaeopteryx
    n 1: extinct primitive toothed bird of the Jurassic period
         having a long feathered tail and hollow bones; usually
         considered the most primitive of all birds [syn:
         {archaeopteryx}, {archeopteryx}, {Archaeopteryx
         lithographica}]

from The Collaborative International Dictionary of English v.0.48

Archaeopteryx \Ar`ch[ae]*op"te*ryx\, n. [Gr. 'archai^os ancient
   + pte`ryx wing.] (Paleon.)
   A fossil bird, of the Jurassic period, remarkable for having
   a long tapering tail of many vertebr[ae] with feathers along
   each side, and jaws armed with teeth, with other reptilian
   characteristics.
   [1913 Webster]