Stigmatella dychei

Phylum: Bryozoa
Class: Stenolaemata
Order: Trepostomatida
Family: Heterotrypidae
Genus: Stigmatella
Species: Stigmatella dychei

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Taxonomic History:

  • 1882 Monticulipora (Monotrypa) dychei James, Paleontologist, no. 6, p. 52.
  • 1883 Monticulipora dychei James, Journ. Cincinnati Soc. Nat. Hist., vol. 6, p. 235, pl. 10, figs. 2-2e.
  • 1888 Monticulipora dychei James & James, ibid, vol. 11, p. 25.
  • 1895 Monticulipora (Monotrypa) dychei James, ibid.,vol. 18, p. 83.
  • 1900 Leptotrypa? dychei Nickles & Bassler, Bull. U.S. Geol. Surv., vol. 173, p. 298.
  • 1904 Stigmatella dychei Ulrich & Bassler, Smiths. Misc. Coll, Quart., vol. 47, p. 34, pl. 10, fig. 11.
  • 1906 Stigmatella dychei Bassler, Proc. U.S. Nat. Mus., vol. 30, p. 54, pl. 3, figs. 8-10.

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Stratigraphic Occurrences


Geographic Occurrences

Map point data provided by iDigBio.
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Sequences (Formations)

  • C4 Sequence (Arnheim)
  • C3 Sequence (Mt. Auburn)

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Identification in Hand Sample

Stigmatella dychei from the Mt. Auburn Formation of Cincinnati, Ohio (CMC 57487)

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Holland (UGA Strat Lab, 2013):

  • Loosely encrusting, with thin-walled angular zooecia, a lack of mesopores, acanthopores in zones, and almost no diaphragms.

Bassler (1905):

  • Both the internal and external features of this species have been figured by its author satisfactorily enough for its recognition, and additional illustrations of the internal structure are given here only to bring out points mentioned by James nor shown in his figures.
  • The zoarium is an expansion loosely incrusting crinoid columns and sometimes attains considerable size, the type specimen being about 180 mm. in length and varying from a minimum diameter of 5 mm. at the ends to a maximum of 60 mm.
  • In vertical sections, the noticeable features are the almost complete absence of diaphragms and the development of the acanthopores in zones, the latter feature in combination with the former being the principal characteristic of the genus Stigmatella. Tangential sections passing through one of these zones of acanthopores exhibit these structures of a fair size at the zooecial angles, but a section through any other part of the zoarium shows thinner-walled zooecia with the acanthopores either very small or not present at all.
  • The loosely incrusting method of growth, thin-walled angular zooecia with mesopores practically wanting, the development of acanthopores in zones and the almost entire absence of diaphragms are characters causing this species to be easily recognized. S. clavis (Ulrich), a common and highly characteristic fossil of the Eden shales, also grows on crinoid columns, but it can not be confused with S. dychei, its zoaria being much smaller and the surface nearly always spinulose.

James (1876):

  • Corallum sub-fusiform in outline, parasitic on a crinoid column, with rough, nodular swellings, low ridges, and annular constrictions. Surface with slightly raised, rounded monticules, irregularly distributed over the surface and occupied by calices slightly larger than the average. Calices polygonal; walls of cells thin and sharp; interstitial tubes wanting.
  • Obs. – This species is one easily recognized by the peculiar form, and its place of growth. The crinoid stem upon which the corallum grows is easily seen at either end. The type specimen is seven inches long, and tapers both ways from a diameter of two inches to little more than the size of the crinoid stem.

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