Phylum: Bryozoa
Class: Stenolaemata
Order: Trepostomatida
Family: Monticuliporidae
Genera: Aspidopora Ulrich, 1882
Cincinnatian Species: Aspidopora eccentrica, Aspidopora newberryi

Taxonomic Details

Type species: Aspidopora aerolata (Ulrich, 1882)
Synonym: Prasopora but this is questionable (; Astrova (1978) considered Aspidopora to be a synonym of Prasopora but Karklins (1983) retains it as a speparate genus (Holland, UGA Strat Lab)
Often called: Monticulipora aerolata, M. newberryi, M. eccentrica (Holland, UGA Strat Lab)Species in Cincinnatian of Ohio, Indiana, Kentucky (

  • Aspidopora areolata (Ulrich, 1882)
  • Aspidopora newberryi (Nicholson, 1875)
  • Aspidopora eccentrica (James, 1882)

Taxonomic History (Nickles & Bassler, 1900)

  • 1882 Aspidopora Ulrich, Jour. Cincinnati Soc. Nat. Hist., V, p. 155.
  • 1889 Aspidopora Miller, North American Geol. Pal., p. 293.
  • 1890 Aspidopora Ulrich, Geol. Sur. Illinois, VIII, p. 373.
  • 1893 Aspidopora Ulrich, Geol. Minnesota, III, p. 254.
  • 1897 Aspidopora Simpson, Fourteet Ann. Rep. State Geo.

Stratigraphic Occurrences


Geologic Range
Ordovician – Silurian

Geographic Occurrences

Stratigraphic Distribution

Sequences (Formations)

  • C1 Sequence (Clays Ferry/Kope: McMicken, Southgate, Economy/Fulton)

Identification in Hand Sample:

  • Zoarium Morphology: Discoidal, Composed of 2 or more superimposed layers; lower side concave, with wrinkled epitheca
  • Zoecia: Circular to sub-elliptical
  • Mesozooids: Numerous, sometimes isolating the zooecia
  • Monticules: None; surface smooth
  • Maculae: Composed of larger apertures

Species Differentiation

Published Description

Holland (UGA Strat Lab, 2013):

  • Thin section work: Zooecia circular to subelliptical, and nearly separated by mesozooids bearing numerous diaphragms in outer exozone; cystiphragms are common, but diaphragms are rare to absent; tiny styles are present.
  • Aspidopora colonies are thin discs. Zooecia are circular to subelliptical, and they are nearly separated by mesozooids bearing numerous diaphragms in outer exozone. Cystiphragms are common, but diaphragms are rare to absent. Tiny styles are present.
  • Astrova (1978) considered Aspidopora to be a synonym of Prasopora, but Karklins (1983) retains it as a separate genus.

Parks and Dyer (1922):

  • Ulrich’s original description of this genus is as follows:
    Very thin free expansions with a concentrically and radially striated epitheca covering the lower side. Composed of (according to age) from one to many unequal convex spaces. Cells gradually increasing in size from the margin of each convex space to near the centre of the same. Interstitial cells numerous. Both kinds of tubes crossed by diaphragms. Spiniform tubuli present.
  • In the report of the Geological Survey of Minnesota (op. cit.) he modifies this description as follows:
    Diaphragms horizontal and closely set in the mesopores, usually wanting in the zooecial tubes, but one or more cystiphragms occur in most of the latter. In previous publications on this genus I did not mention the presence of cystiphragms because these structures seem to be wanting in the type species. My present opinion is that the supposed diaphragms figured by me for Aspidopora areolata are really cystiphragms, in part incorrectly drawn.
  • All later species ascribed to Aspidopora are characterized in particular by the presence of cystiphragms and the absence of diaphragms in the zooecial tubes. This feature together with the characteristic manner of growth define the genus Aspidopora as at present accepted. It is unfortunate that no further description or figures of the type species, Aspidopora areolata, have appeared. The original figures certainly do no suggest the absence of diaphragms or the presence of cystiphragms and despite Ulrich’s emendation it seems very unlikely that he would have overlooked in the type species so striking a characteristic.

Nickles & Bassler (1900):

  • Aspidopora Ulrich: Zoarium a thin expansion, sometimes of superimposed layers, usually free, with epitheca on underside; typically composed, according to age, of from one to many subequal parts, each gently convex, with the zooecia diminishing in size from center to margin; diaphragms wanting; cystiphragms few in the zooecia; mesopores numerous, with close diaphragms; acanthopores usually present, always small.

A. eccentrica

A. newberryi