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Species / Drepanocheilus Texanus


Original description of Drepanochilus texanus by Stephenson, 1941:

  • "Shell small for the group. Spire conical with apical angle of about 45 degrees. Whorls 5, moderately convex on the sides, with no constriction below the suture. Suture closely appressed, deeply impressed. Protoconch not preserved on the available material. The surface is ornamented with numerous rather closely spaced, axial ribs which vary somewhat in prominence and in the sharpness of their crests; in general these ribs are about equal in width to the interspaces; they trend downward and slightly forward, and the trend is broadly concave toward the aperture. The ribs number 33 on the body whorl, 28 on the penultimate, and 24 on the antepenultimate whorl of the holotype. The axials on the body whorl terminate below against a moderately strong, obscurely noded spiral rib which occupies the periphery of this volution; and dies out apically before reaching the penultimate whorl; a second similar but less prominent spiral parallels the first one about 1.5 mm. farther forward on the base. The periphery of the body whorl is obtusely subangular, and the base rounds down abruptly to the columella. The whole surface is covered with fine spiral threads which override the axials; on the base these threads are stronger than elsewhere and tend to alternate in size. The aperture is imperfect in the available material, but is elongated, passes backward into an angular anal canal, and forward into an anterior narrow canal, which is broken away in all the specimens. The outer lip is mostly broken away on all the shells, but at the posterior margin in adults it is reflected outward and also upward about one-third of the way across the penultimate whorl. The inner lip forms a rather thick callus which is broadly excavated, spreads noticeably forward over the base, and folds neatly forward over the columella in front."

Locus typicus: 3 miles south, 30 west of Thrall, Williamson County, Texas, USA

Stratum typicum: Kemp Clay, Navarro Group, Maastrichtian, Cretaceous

Type specimens: Holotype USNM no. 76953: height 17.5+ mm, diameter 9.3+ mm, (exclusive of the expanded outer lip); one figured paratype no. 76954; 6 unfigured paratypes no. 76955.

Drepanochilus texanus in Stephenson, 1941, pl. 57, fig. 1, 2, 3, 4

  • two left holotype; two right paratype
  • Image courtesy The University of Texas at Austin


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