Cyclonema humerosum

Phylum: Mollusca
Class: Gastropoda
Order: Euomphalina
Family: Platyceratidae
Genus: Cyclonema
Species: Cyclonema humerosum (Ulrich, 1897)


Stratigraphic Occurrences


Geographic Occurrences

Map point data provided by iDigBio.

Stratigraphic Description

Sequences (Formations)

  • C5 Sequence (Waynesville)
  • C4 Sequence (Arnheim)
  • C3 Sequence (Mount Auburn, Corryville)
  • C2 Sequence (Bellevue)

Identification in Hand Sample

  • Deeply channeled suture
  • Angular shoulder
  • Broad ramp
  • Whorl profile straight to concave between sutures
  • Variable ornament generally consists of three orders of 9-10 spiral lines crossed by growth lirae

Cyclonema humerosum from the Waynesville Formation of Waynesville, Ohio (OUIP 1801)

Cyclonema humerosum (Click to view in 3D!)

Cyclonema humerosum (Click to view in 3D!)

Published Description

Morris & Felton (1993):

  • In contrast, Cyclonema humerosum, a coarsely ornamented species and the one most commonly found attached to Glyptocrinus calices, appears to have been adapted to a higher energy, shallower environment. Cyclonema humerosum commonly occurs in stratigraphic units such as the Mt. Auburn, Oregonia, and reworked zones of the Corryville Member, in which the bottom was often above wave base, causing reworking of bottom sediments and the development of a skeletal sand/skeletal hash substrate. If Cyclonema humerosum did require a firm substrate on which to develop, larval stages of this species being dispersed out over a mud substrate might have found available Glyptocrinus calices an optimal and suitable site for settlement.

Thompson (1970):

  • Diagnosis. — Deeply channeled suture, angular shoulder, broad ramp; otherwise similar to C. bilix.
  • Description. — Trochiform gastropod with deeply channeled sutures, horizontal ramps, and angular to rounded shoulders; nucleus unknown; whorl profile straight to concave between sutures; aperture polygonal, flattened at base and oblique abaperturally, outer lip rounded to straight and sometimes expanded onto body whorl at upper suture, inner margin straight, columellar lip thickened, lunate, and excavated. Variable ornament generally consists of three orders of 9-10 spiral lines crossed by growth lirae; cords may be separated by costae and threads, or coarse, prominent, and widely separated by two or three threads, or numerous, thin, closely packed and separated by threads, cords extend over half of basal surface; growth lirae are coarse and widely separated or fine and closely spaced to form pits on the shell surface; strong growth wrinkles at aperture often obscure spiral ornament, produce depressions in suture, and cause concave whorl profiles.

Ulrich & Scofield (1897):

  • The average size in this species is somewhat greater than in either of the preceding forms, while the apical angle is generally wider and more constant, the majority of the specimens varying comparatively but little either way from 85°. The principal feature, however, is it strongly developed shoulder, giving a deeper suture than in any other species of the genus. This shoulder may be rounded or, especially in the Richmond group form, quite angular. In the latter the slope of the outer side of the last whorl is very often distinctly concave, and not infrequently undulated in the direction of the lines of growth. The same conditions occur less frequently though quite as well marked in the Lorraine form. The surface markings are fairly constant. About ten principal subequal carinae occur on the outer slope of the body whorl, and about the same number of smaller ones on the periphery and base. The larger ones usually alternate with a much thinner set.