Phylum: Bryozoa
Class: Stenolaemata
Order: Trepostomatida
Family: Mesotrypidae
Genus: Peronopora Ulrich, 1882
Species: Peronopora decipiens, Peronopora vera, Peronopora milleri

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Type species: Chaetetes decipiens (Nicholson, 1874 ); = Chaetetes decipiens Rominger, 1866
Synonym: Homotrypella Ulrich, 1886 (Type species Homotrypella instabilis (Ulrich, 1886)) (Fide Martinsch, 1998)
Species in Cincinnatian of Ohio, Indiana, Kentucky (

  • Peronopora decipiens (Rominger, 1866)
  • Peronopora browni (Anstey and Pachut, 2004)
  • Peronopora compressa (Ulrich, 1879)
  • Peronopora decipiens (Rominger, 1866)
  • Peronopora dubia (Cumings and Galloway, 1913)
  • Peronopora horowitzi (Pachut and Anstey, 2002)
  • Peronopora milleri (Nickles, 1905)
  • Peronopora pachymura (Utgaard and Perry, 1964)
  • Peronopora pauca (Utgaard and Perry, 1964)
  • Peronopora sparsa (Brown and Daly, 1985)
  • Peronopora uniformis (Ulrich, 1882)
  • Peronopora vera (Ulrich, 1888)

Taxonomic History (Nickles & Bassler, 1900)

  • 1881 Peronopora Nicholson, Genus Monticulipora, pp. 102, 215.
  • 1882 Peronopora Ulrich, Jour. Cincinnati Soc. Nat. Hist., V, p. 153.
  • 1886 Peronopora Waagen and Wentzel, Pal. Indica, Ser. XIII, p. 875.
  • 1890 Peronopora Ulrich, Geol. Sur. Illinois, VIII, p. 370.
  • 1896 Peronopora (in part) Zittel’s Textb. Pal. (Engl. ed.), p. 104.
  • 1896 Peronopora Ulrich, Zittel’s Textb. Pal. (Engl. ed.), p. 272.

Note: It is unclear why lists so few species in this genus, whereas the UGA stratigraphy lab lists more than 10. The species typically described from the Cincinnatian are: Peronopora vera, Peronopora decipiens, and Peronopora milleri (McFarlan, 1931; Davis, 1998).
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Geologic Range
Middle Ordovician – Late Ordovician

Stratigraphic Occurrences


Geographic Occurrences

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Sequences (Formations)

  • C6 Sequence (Elkhorn)
  • C5 Sequence (Lower Whitewater, Liberty)
  • C4 Sequence (Arnheim)
  • C3 Sequence (Mt. Auburn, Corryville)
  • C2 Sequence (Bellevue, Fairview: Fairmount, Mount Hope)
  • C1 Sequence (Clays Ferry/Kope: McMicken, Southgate, Economy/Fulton)

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Identification in Hand Sample:

  • Zoarium Morphology: Bifoliate (usually); often fan-shaped
  • Zoecia: Circular to subpolygonal; often thick-walled (ring-like in cross-section)
  • Mesozooids: Variable to numerous
  • Monticules: Low, inconspicuous (surface smooth)
  • Maculae: Central cluster of mesozooids and/or larger zooecia

Species Differentiation

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Holland (UGA Strat Lab, 2013):

  • Peronopora is typically bifoliate, but may also be encrusting, ramose, or massive. Monticules may be defined by increased style diameter, a cluster of mesozooids, or larger zooecia. The median layer may be absent in some specimens, causing it to appear frondose. Cystiphragms form continuous overlapping series, beginning at the median layer and extending through most of exozone. Cystiphragms are typically on the distal side of zooecia, but may be adjacent to a monticule. Diaphragms are present but thin. Styles are generally abundant and large, and they may inflect zooecial walls. Mesozooids are usually large and abundant but become progressively crowded out distally.

Davis (1998):

  • Typical fan shape
  • This genus differs from all others by having zooecia on both sides of a fan separated by thin wall which way be seen best in thin-section

Karklins (1984) (On Peronopora):

  • Type species.— Chaetetes decipiens Rominger, 1866, p. 115; subsequent designation by ICZN (1968, Opinion 838) upon application submitted by Utgaard and Boardman (1965); “Corryville Member of the McMillan Formation, Maysville Group, Upper Ordovician” (Boardman and Utgaard, 1966).
  • Remarks.— Boardman and Utgaard (1966) discussed the zoarial development of Peronopora and revised the concept for the genus. The definition of the genus Peronoporaas given by Boardman and Utgaard (1966) is followed here.

Karklins (1984) (On Homotrypella – synonym):

  • Type species.— Homotrypella instabilis Ulrich, 1886, p. 83; by original designation; Decorah Shale, Rocklandian Stage, Middle Ordovician.
  • Remarks.—The taxonomic status of the genus Homotrypella is somewhat uncertain, but the concept for the genus has been used in studies of bryozoan fauna from the Upper Ordovician strata in Indiana (Utgaard and Perry, 1964, p. 61). Subsequently, Astrova (1978, p. 94) reevaluated the genera Homotrypa and Homotrypella mainly on the basis of material from the Middle Ordovician (D2 of Astrova) and Upper Ordovician (D3 of Astrova) rocks of the U.S.S.R. and considered Homotrypella to be a subjective junior synonym of Homotrypa. However, Homotrypella is herein retained as a separate genus. The definition of Homotrypella by Ulrich (1893, p. 228) is followed herein in sensu lato until additional material of Homotrypella instabilis Ulrich, the type species of Homotrypella, is redescribed and is compared with Homotrypa curvata Ulrich, 1882, the type species of Homotrypa.

Nickles & Bassler (1900) (On Peronopora):

  • Peronopora Nicholson: Zoarium bifoliate, through branching of the fronds, often forming convoluted masses; surface smooth, usually with maculae; zooecia with rather thick walls, ring-like in transverse section, not inflected by the acanthopores; cystiphragms abundant; apertures circular or subpolygonal; mesopores and acanthopores variable in number.

Nickles & Bassler (1900) (On Homotrypella – synonym):

  • Homotrypella [synonym of Peronopora, see above] Ulrich: Zoarium irregularly ramose or laminar; surface smooth, with small maculae; zooecia rather thin-walled, cystiphragms usually confined to the earlier part of the mature region and never present in the axial region; apertures subcircular, sometimes faintly pelatoid; mesopores abundant, more or less completely isolating the zooecia; acanthopores numerous.

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P. decipiens

P. vera