Orthonybyoceras dyeri

Phylum: Mollusca
Class: Cephalopoda
Order: Orthocerida
Family: Proteoceratidae
Genus: Orthonybyoceras
Species: Orthonybyoceras dyeri (Miller, 1875)

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Originally: Orthoceras dyeri, Ormoceras? covingtonense, Orthonybyoceras covingtonense (Holland, UGA Strat Lab 2013)
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Stratigraphic Occurrences


Geographic Occurrences

Map point data provided by iDigBio.
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Sequences (Formations)

  • C4-C6 Sequence (Bull Fork)
  • C3 Sequence (Grant Lake)
  • C2 Sequence (Fairview)

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Identification in Hand Sample

  • Rapidly expanding longicone
  • Small to medium sized phragmocone (~25 cm in length)
  • Compressed siphuncle segments
  • Short septal necks
  • Connecting rings between septa are thin
Orthonybyoceras dyeri

Orthonybyoceras dyeri from Maysville formation of Hamilton County, Ohio (CMCIP 352)

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Davis (1998):

  • Cephalopod. One of numerous cephalopods of the Richmondian. (See plate 1 fig 25). Especially abundant in Waynesville.

Frey (1995):

  • Diagnosis. – Small to medium-sized , rather rapidly expanding orthoconic longicone with compressed, subcentral siphuncle segments one-third to one-fourth the diameter of the shell; short recumbent septal necks, and thin connecting rings adnate dorsally to adjacent septa.
  • Description. – Small to medium-sized (phragmocone at least 25 cm in length and up to 4.3 cm in diameter), rapidly expanding (apical angle 8.5-10 degrees) orthoconic longicones; circular to slightly depressed in cross section with straight transverse sutures. Camerae short having cameral lengths ranging from one-fifth to one-seventh the diameter of the shell, decreasing in length with ontogeny relative to shell diameter. Body chamber poorly known, at least one-fifth the total diameter of the shell. Periphract dorsomyarian. Shell exterior smooth.
  • Siphuncle subcentral most of the length of the shell, becoming more ventral in position with ontogeny. Siphuncle segments expanded, compressed, the SCR values ranging from 1.3 at shell diameters of 25 mm to 1.7 at diameters of 35 mm. Segments from one-third to one-fourth the diameter of the shell, decreasing slightly in diameter with ontogeny. Septal necks short, with recumbent brims. Connecting rings thin, homogeneous, adnate to either adoral or adapical septa dorsally; ventrally adnate to adapical septa or not adnate at all. Dorsal endosiphuncular deposits consisting of annuli developed more or less symmetrically about the septal necks; deposits more asymmetrical ventrally, consisting of annulisiphonate deposits that are much thicker in development in the region adoral to septal necks. Perispatia well developed. Dorsal radial canals intersect the connecting ring wall at midpoint of segment. Ventrally, radial canals intersect connecting ring wall in adoral half of segment. Cameral deposits consisting of episeptal and hyposeptal deposits that, adorally, are more heavily developed ventrolaterally.

James (1886):

  • Shell medium size or large, gradually tapering; septa arched, distant from one-fifth to two-ninths the diameter of the shell; siphuncle subcentral or eccentric, varying in position and in size; outer shell unknown.

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