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Species / Pterocerella Poinsettiformis


Original description of Pterocerella poinsettiformis by Stephenson, 1941:

  • "Shell of moderate size, thin, conical, apical angle 54 degrees. Protoconch small, trochoid, smooth, dextral, coiled about 3 times, and rather sharply distinguishable from the first whorl of the conch. The whorls are 6 in number on adults, are moderately convex on the sides, and have no axial ornamentation. Suture closely appressed, moderately impressed. A narrow, prominent sharply round-crested revolving carina traverses each whorl a little below the middle, and extends back to the junction of the conch with the protoconch. A similar narrow carina, a little less prominent, marks the periphery of the body whorl; this carina is not quite overridden by the posterior margin of the growing conch, so that its crest appears as a narrow, sharply defined band just above the suture. The base is abruptly constricted, and is smooth with the exception of 2 gentle revolving swells which divide the base into 3 bands of nearly equal width. The outer lip is fantastically expanded and subdivided into a series of 6 long, widely flaring, paddle-like wings of more or less irregular outline, separated by deep, wide indentations. The two carinae on the body whorl and the two revolving swells on the base pass forward onto the outer lip, following respectively the centers of the 4 inner wings, on which they all appear as sharp, narrow, prominent carinae; the two outer wings, that is the posterior and anterior of the 6 wings, are also marked centrally by similar carinae; these 2 outer wings appear as having forked off from the nearest adjacent wings. The under side of each wing is cut longitudinally by a channel which opposes the carina on the outside of the wing, and this channel is closely bordered on each side by a narrow prominent carina; these channels connect with the aperture, which is somewhat elongated though fairly wide open. The inner lip of adults is thick and stands out prominently away from the base of the shell."

Locus typicus: Vicinity of Kaufman, Kaufman County, Texas, USA

Stratum typicum: Nacatoch Sand, Navarro Group, Maastrichtian, Cretaceous

Type specimens: Holotype U.S.N.M. no. 76969, height disregarding the downward expansion of the wings, 34 mm.; diameter measured to the base of the wings, about 22 mm. The maximum wing spread is 70 mm. or more; 3 paratypes, nos. U.S.N.M. 20994, U.S.N.M. 21061, U.S.N.M. 76970.

Pterocerella poinsettiformis Stephenson, 1941, pl. 58, fig. 9, 10, 11, 12

  • Image courtesy The University of Texas at Austin

History and Synonymy


Pterocerella poinsettiformis in Sohl, 1960, pl. 13, fig 1, 2

  • image courtesy of the U.S. Geological Survey

Specimens from institutional collections

Pterocerella poinsettiformis Stephenson, 1941; Coon Creek Tongue, Selma Group, Ripley Formation, Maastrichtian, Cretaceous; Mr. Dave Weeks' farm, on Coon Creek, 3.5 mi S of Enville and 7.5 mi N of Adamsville, McNairy County, Tennessee, USA; Coll. Yale Peabody Museum of Natural History YPM IP 009046


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