Stromboidea

• Aporrhaidae
  • Drepanochilus
    • Drepanochilus evansi Cossmann, 1904

Original Description of Rostellaria americana by Evans & Shumard, 1857, p. 42:

• "Shell elongate-conic, spire elevated; spiral angle 30°; body whorl obtusely angulated, and bearing two distinct carinae, which diverge as they approach the outer lip, and become nearly obsolete before reaching entirely around the volution; upper carina most prominent, and rendered subnodulose by longitudinal, moderately prominent, double-arched folds; surface with distinct revolving striae, of which there are about five in the space between the two carinae; striae below the carinae rather sharper than those above; aperture elongate subtriangular.
• Length of last volution, 6 1/2 lines; width, 5 1/2 lines (not including the prolongations of the lip, which are broken off); length of aperture, 4 1/2 lines.
• Locality. — Moreau and Grand Rivers."

Cossmann, 1904, p. 75

Chenopus (Drepanochilus) evansi in Cossmann, 1904, pl. VI, fig. 11, 12

History and Synonymy

1857

Rostellaria americana Evans & Shumard, 1857:42

1960

Drepanochilus evansi in Sohl, 1960, pl. 11, fig 23, 26

• image courtesy of the U.S. Geological Survey

1974

Drepanochilus evansi Erickson, 1974, pl. 14, fig. 10, 11, 12, 13

Erickson, 1974, p.173:

• "Drepanochilus evansi Cossmann, 1904. Diagnosis. — Shell large for genus; body whorl strongly bicarinate, upper carina developing into long upturned pointed canal on flaring outer lip; lip becoming infilled and thickened in old age. Early whorls covered with threads crossing strong, almost evenly opisthocline ribs; on body whorls ribs are lost, seen only as nodes on upper carina, numerous small cords develop over body whorl as well. Pleural angle 25-30 degrees. Discussion. — Because this is a common form from the Western Interior it has often been cited in the older literature and has thus developed an involved synonymy. It was a junior homonym of Rostellaria americana d'Orbigny a problem recognized and corrected by Cossmann in 1904 (p. 75) when he referred the species to Arrhoges (Drepanochilus) evansi, retaining Meek's (1864) subgeneric designation. Arrhoges as now used is a genus containing species with well-defined ribs on the last whorl and a blunt, broad outer lip to which D. evansi does not conform. It remains as the type of Drepanochilus which contains several Western Interior species that form a distinct evolutionary group in the midcontinent region. It was recorded from the Cannonball Formation by Stanton in 1921 (p. 37) and is not new to the state; Cvancara (1956) recorded it from the Fox Hills Formation. Types. - Hypotypes UND 13448, 893, 13455. Type locality. — "Moreau and Grand Rivers" (Evans and Shumard, 1857, p. 42); this is in the type area of the Fox Hills Formation in South Dakota. Occurrence. — D. evansi is common at two localities; from concretions in the Trail City Member at locality A469 and from fine and medium-grained sandstone of the Timber Lake Member at locality A460. Geologic range. — Maestrichtian-Paleocene."

Specimens from institutional collections

Aporrhais americana (Evans and Shumard, 1857); Fort Pierre Beds, Cretaceous; Belle Fourche River, South Dakota, USA; Coll BMNH no. G. 10047

Drepanocheilus evansi Cossmann, 1904; Pierre Shale, Campanian, Cretaceous; Western Interior, Moreau River, South Dakota, USA; Coll. Yale Peabody Museum of Natural History YPM IP 008883

References:

• Cossmann M. (1895-1924). Essais de paléoconchologie comparée. Paris, published by the author. Part 1: 1-159, pl. 1-7 [1895]. Part 2: 1-179, pl. 1-8 [1896]. Part 3: 1-201, pl. 1-8 [1899]. Part 4: 1-293, pl. 1-10 [1901]. Part 6: 1-261, pl. 1-7 [1904]. Part 7: 1-261, pl. 1-14 [1906]. Part 8: 1-248, pl. 1-4 [1909]. Part 9: 1-248, pl. 1-4 [1912]. Part 10: 1-292, pl. 1-12 [1916]. Part 11: 1-388, pls 1-11 [1918]. Part 12: 1-348, pls 1-10 [1921]. Part 13: 1-345, pls 1-12 [1924]. Fulltext
• Erickson (1974)
• Evans, J.; Shumard, B. F. (1857). On some new species of fossils from the Cretaceous Formation of Nebraska Territory. Transactions of the Academy of Science of St. Louis. 1: 38-42, Fulltext
• Sohl, 1960