The Collaborative International Dictionary of English v.0.48:

Cordaitales \Cordaitales\ n.
   an order of extinct plants having tall arborescent trunks
   comparable to or more advanced than cycads; known from the
   Pennsylvanian; probably extinct since the Mesozoic.

   Syn: order Cordaitales.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Cordaitales
    n 1: extinct plants having tall arborescent trunks comparable to
         or more advanced than cycads; known from the Pennsylvanian
         period; probably extinct since the Mesozoic era [syn:
         Cordaitales, order Cordaitales]