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Species / Anchura Umbrana

Original description of Anchura umbrana by Stephenson, 1953, p. 64:

  • "Shell rather small for the genus, high-turreted, with spiral angle of about 30 degrees. Protoconch not preserved. Whorls 6 or 7, gently convex on the side, the larger whorls ornamented with axial ribs and spiral lirae; on the penultimate whorl the axials are small, closely crowded, and number at least 22; they are strongly oblique and sinuous in trend, being slightly convex forward below, broadly concave forward above, bending strongly forward just below the suture; the spirals are small, obscure centrally, and become a little stronger toward the sutures both below and above. On the body whorl the axials extend well down the basal slope, becoming weaker toward the lip; they are broadly convex forward in trend except near their upper ends where they bend forward to the suture. The spirals are obscure on the inflated part of the body whorl but become stronger above, the uppermost just below the suture being relatively coarse; about 10 spirals are present on the basal slope, the upper 4 or 5 being weak to obscure, and the lower 5 or 6 relatively strong; low rounded nodes mark the intersections of the axials with the stronger spirals. The aperture is ovate-elongate. The outer lip is expanded and winglike but is poorly preserved in the available material. A rather obscure impression on one paratype (pl.13, fig. 30), and one wing broken from its parent shell (pl. 13, fig. 30) indicate the presence of one thick, winglike, upturned projection; the latter figure shows the interior of the broken wing. The inner lip forms a rather broad band of callus over the parietal wall."

Locus typicus: Hauted Hill, 3.5 northwest of Moody, McLennan County, Texas, USA

Stratum typicum: Pepper Shale Member, Woodbine Formation, Cenomanian, upper Cretaceous

Types: holotype USNM 108360, paratypes 108361, 108362

Dimensions: Of the incomplete holotype: diameter exclusive of the expanded lip, about 11.5 mm; height 24+ mm;

Anchura umbrana Stephenson, 1953, pl. 13, fig. 25 - 30


  • Davila-Alcocer, V.M. 1974. Geologia del area de Atenango del Rio, Estado de Guerrero. Tesis Profesional, Universidad Nacional Autonoma de Mexico, Facultad de Ingenieria, 109 pp.
  • Stephenson, 1953

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