Stigmatella

Classification
Phylum: Bryozoa
Class: Stenolaemata
Order: Trepostomatida
Family: Heterotrypidae
Genus: Stigmatella Ulrich & Bassler, 1904
Cincinnatian species: Stigmatella dychei

Taxonomic Details

Type Species: Stigmatella crenulata (Ulrich & Bassler, 1904)
Synonyms: Dannunziopora Vinassa de Regny, 1921; Dannunzioporina Vinassa de Regny, 1921Species found in the Cincinnatian (Bryozoa.net)

  • Stigmatella acanthera (Brown & Daly, 1985)
  • Stigmatella alcicornis (Cumings & Galloway)
  • Stigmatella clavis (Ulrich, 1883)
  • Stigmatella conica (Brown, 1965)
  • Stigmatella crenualata (Ulrich & Bassler)
  • Stigmatella dubia (Perry & Hattin, 1960)
  • Stigmatella dychei (James, 1882)
  • Stigmatella incrustans (Cumings & Galloway)
  • Stigmatella interporosa (Ulrich & Bassler, 1904)
  • Stigmatella irregularis (Ulrich)
  • Stigmatella multispinosa (Brown, 1965)
  • Stigmatella nichlesi (Ulrich & Bassler)
  • Stigmatella nana (Ulrich & Bassler, 1904)
  • Stigmatella personata (Ulrich & Bassler, 1904)
  • Stigmatella sessilis (Cumings & Galloway, 1913)
  • Stigmatella spinosa (Ulrich & Bassler, 1904)

Stratigraphic Occurrences

Stigmatella_strat

Geologic Range
Ordovician

Geographic Occurrences

Stratigraphic Distribution

Sequences (Formations)

  • C5 Sequence (Liberty, Waynesville)
  • C4 Sequence (Arnheim)
  • C2 Sequence (Bellevue)
  • C1 Sequence (Clays Ferry/Kope: McMicken, Southgate, Economy/Fulton)

Identification in Hand Sample:
Stigmatella

  • Zoarium Morphology: Encrusting, massive, or ramose
  • Zoecia: Thin-walled, polygonal to subrounded; styles small and weak
  • Mesozooids: Variable (often confined to maculae)
  • Monticules: Present
  • Maculae: composed of mesozoids

Species Differentiation

Published Description

Steven Holland (UGA Strat Lab, 2013):

  • Stigmatella may be encrusting, massive, or ramose, and typically has maculae composed of mesozooids. Zooecial walls are thin but are thickened at regular intervals in the exozone. Diaphragms are thin and delicate. Mesozooids may or may not be present, and they are often confined to maculae. Styles, though always present, are small and typically developed in narrow zones where walls are thickened.

Karklins (1984):

  • The original definition by Ulrich and Bassler (1904, p. 33) for the genus Stigmatella is followed here. They characterized Stigmatellaas having zoaria with irregular and various growth habits, polygonal to subrounded autozooecial shapes in cross-section, relatively few basal diaphragms, and numerous but irregularly distributed styles (acanthopores of Ulrich and Bassler). Mesozooecia (mesopores of Ulrich and Bassler) were characterized as sparse or irregularly variable in abundance.

Treatise on Invertebrate Paleontology, Part G (1953):

  • Typically ramose, also incrusting to massive. Zooecial tubes crenulated. Acanthopores in periodically developed mature zones.

McFarlan (1931):

  • Genus: Zooarium variable. Characterized by periodic thickening of the walls of zooecial tubes, the development of acanthopores in these zones, and the meagre development of diaphragms.

Bassler (1911):

  • This genus was established for a group of the Heterotrypidae differing from other divisions of the family in having the walls of the zooecial tubes noticeably thickened at periodic intervals, and in developing acanthopores only in these zones of thick walls. This periodic thickening of the zooecial walls with an accompanying accelerated development of the acanthopores has been found characteristic of a number of Ordovician species which range in growth from the incrusting to irregularly massive and ramose. In all other respects, these species are typical Heterotrypidae. The generic name was selected for the reason that many of the species have unusually distinct maculae or “spots” composed of mesopores distributed over the zoarium at regular intervals. Thin sections are almost a necessity for the initial determination of a species of Stigmatella, although additional specimens of a species can readily be detected after the first example has been sectioned. The areas of thickened walls and numerous acanthopores undoubtedly represent repeated mature zones in the zoarium, for it is here only that mature zooecial characters can be observed. Mesopores may be few, indeed absent, or numerous. Without sections, an incrusting species without mesopores would be confused with a Leptotrypa like L. hexagonalis figured on page 208, but a single layer of the Stigmatella would show several alternately thin and thick walled areas. Comparison with other genera of the Heterotrypidae might be made, but in every case, the distinct zones of Stigmatella remain the most diagnostic feature. Another characteristic is the sparse development of diaphragms, in which feature the genus approaches Dekayia, although differing in its numerous mesopores. The following species include one with crenulated walls characteristic of the typical members of the genus, and two others conspicuous mainly for their extravagant development of small acanthopores indenting the zooecial cavity.
  • Genotype.—Stigmatella crenulata Ulrich and Bassler. Earliest Silurian (Richmond), Ohio Valley.

S. dychei