Phylum: Bryozoa
Class: Stenolaemata
Order: Trepostomatida
Family: Mesotrypidae
Genus: Atactoporella Ulrich
Cincinnatian Species: Atactoporella newportensis, Atactoporella schucherti, Atactoporella typicalis

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Type species: Atacoporella typicalis (Ulrich, 1883)
Species in Cincinnatian of Ohio, Indiana, Kentucky (

  • Atactoporella multigranosa (Ulrich, 1879)
  • Atactoporella mundula (Ulrich, 1879)
  • Atactoporella newportensis (Ulrich, 1883)
  • Atactoporella ortoni (Nicholson, 1874)
  • Atactoporella schucherti (Ulrich, 1883)
  • Atactoporella tenella (Ulrich, 1879)
  • Atactoporella typicalis (Ulrich, 1883)

Taxonomic History (Nickles & Bassler, 1900)

  • 1879 Atactopora (in part) Ulrich, Jour. Cincinnati Soc. Nat. Hist., II, p. 119.
  • 1881 Peronopora (in part) Nicholson, Genus Monticulipora, p. 215.
  • 1883 Atactoporella Ulrich, Jour. Cincinnati Soc. Nat. Hist., VI, p. 247.
  • 1889 Atactoporella Miller, North American Geol. Pal., p. 293.
  • 1890 Atactoporella Ulrich, Geol. Surv. Illinois, VIII, p. 370.
  • 1893 Atactoporella Ulrich, Geol. Minnesota, III, p. 222.
  • 1896 Atactoporella Ulrich, Zittel’s Textb. Pal. (Engl. ed.), p. 272.
  • 1897 Atactoporella Simpson, Fourteenth Ann. Rep. State Geologist New York for the year 1894, p. 585.

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Geologic Range
Late Ordovician

Stratigraphic Occurrences

Geographic Occurrences

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Sequences (Formations)

  • C5 Sequence (Lower Whitewater, Waynesville)
  • C4 Sequence (Arnheim)
  • C3 Sequence (Mt. Auburn, Corryville)
  • C2 Sequence (Bellevue, Fairview: Fairmount)
  • C1 Sequence (Clays Ferry/Kope: Economy/Fulton)

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Identification in Hand Sample:

  • Zoarium Morphology: Usually encrusting; occasionally lobate/subramose; generally composed of more than one superimposed (overlapping) layers
  • Zoecia: Rounded to pelatoid apertures with thin walls; numerous acanthopores
  • Mesozooids: Numerous, angular, often isolating zooecia
  • Monticules: More or less elevated; rounded or conical
  • Maculae: Cells slightly larger, wider interspaces
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Holland (UGA Strat Lab, 2013):

  • Atactoporella is typically encrusting, but can also be ramose to massive. Zooecia are thin-walled and bear diaphragms and cystiphragms, which often form overlapping series. Mesozooids are large and numerous, almost isolating zooids and bearing numerous diaphragms. Styles very numerous, causing zooecial openings to be petaloid.

Karklins (1984):

  • Remarks.—Bassler (1953, p. G95) redefined the genus. Subsequently, Astrova (1978, p. 98) redescribed Atactoporella in her posthumous monograph on the Order Trepostomata. Astrova’s definition of Atactoporella is essentially the same as that of Bassler (1953),which is followed herein.

Nickles & Bassler (1900):

  • Atactoporella Ulrich: Zoarium generally incrusting, sometimes lobate or subramose; zooecia with very thin, inflected walls; apertures irregularly pelatoid; mesopores numerous, frequently isolating the zooecia, largely filled by a secondary deposit; acanthopores very numerous.

Ulrich (1882):

  • …new genus [Atactoporella] differs from Atactopora…. in having numerous tabulated interstitial cells, cystoid diaphragms in the proper zooecia, and thin, instead of thick, walls.…Monticulipora differs in having no true interstitial cells…. difference in …habits of growth, the zooarium of Peronopora is double-leaved (and perhaps, occasionally frondescent), while that of Atactoporella is constantly more or less parasitic.

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A. newportensis

A. schucherti

A. typicalis