Abstract.  An exceptionally well-preserved cephalopod mouthpart was discovered in a phosphate
 concretion from the lower Missourian (Upper Pennsylvanian) in Tulsa, Oklahoma, U. S. A. lt con@-
 sists of an almost complete jaw apparatus and a radula, both of which are in the living orientation.
 The black upper and lower jaws, preserved as phosphate, were probably chitinous. The lower jaw
 is slightly larger than the upper and is charaeterized by a widely open outer lamella. The upper jaw
 is built up of a large outer lamella and a short, scallop-shaped inner lamella; the former is distinctly
 divided into two portions in the posterior region.  The radula is preserved in the anterior portion of
 the buccal cavity; it is made of more than ten rows of teeth, each consisting of seven tooth ele-
 ments with a pair of marginal plates.  The overall features of the jaws and radula are essentially
 similar to those described in association with ammonoids rather than nautiloids and coleoids, sug-
 gesting that this mouthpart can be referred to the Arnmonoidea.  However, the lower jaw in our
 specimen differs from previously desscribed mandibles of Carboniferous Gastrioceratoidea,
 Neoglyphioceratoidea, Gonioloboceratoidea, and Dimorphoceratoidea in its less elongate outline.
 For this reason, we refer the cephalopod mouthpart to the Arnmonoidea other than the above
 superfamilies with reservation.

Key words: Ammonoidea, cephalopod mouthpart, Oklahoma, Upper Pennsylvanian.