Source : Webster's Revised Unabridged Dictionary (1913)

Platycoelian \Plat`y*c[oe]"li*an\, a. [Platy + Gr. ? hollow.]
   (Anat.)
   Flat at the anterior and concave at the posterior end; --
   said of the centra of the vertebr[ae] of some extinct
   dinouaurs.