Parvohallopora subnodosa

Phylum: Bryozoa
Class: Stenolaemata
Order: Trepostomatida
Family: Halloporidae
Genus: Parvohallopora
Species: Parvohallopora subnodosa (Ulrich, 1890)

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Includes: Callopora subnodosa, Hallopora subnodosa, Callopora pulchella, Callopora frondosa, Parvohallopora laevigata Singh, 1979 (UGA Strat Lab, 2013)Taxonomic History (Nickles & Bassler, 1900; Under Callopora subnodosa)

  • 1890 Callopora subnodosa Ulrich, Geol. Surv. Illinois, VIII, p. 417, pl. xxxiii, 5, 5c, fig. 3d (p. 308).
  • 1889 Callopora subnodosa (Ulrich in press), Miller, North American Geol. Pal., fig. 465 (p. 296).

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Stratigraphic Occurrences


Geographic Occurrences

Map point data provided by iDigBio.
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Sequences (Formations)

    • C5 Sequence (Saluda, Lower Whitewater, Liberty, Waynesville)
    • C4 Sequence (Arnheim)
    • C3 Sequence (Mt. Auburn)
    • C2 Sequence (Bellevue, Fairview))

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Identification in Hand Sample
E. falciformis

  • Zoarium Morphology: Ramose (branching); 6-12 mm in diameter
  • Zoecia: Smoothly circular; uniform in shape and well separated, surrounded by a variable number of mesopores
  • Mesozooids: Numerous, small, angular; in some cases, completely isolating zooecia
  • Monticules: Low rounded monticules
  • Maculae: Larger apertures, more numerous mesopores

Parvohallopora subnodosa from the Whitewater Formation of Clarksville, Ohio (OUIP 2120)

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Brown & Daly (1985):

  • Diagnosis: Zoaria ramose to subfrondescent, with abundant flush to conical monticules, thin-walled ovate zooecia, sparse diaphragms, and numerous small mesozooecia.
  • Description: Zooecia in endozone polygonal, arising throughout axis from polygonal proximal tips, curving gently outward into generally deep exozone. Intermonticular zooecia large (7+ in 2 mm, 0.21 mm MZD; table 22), commonly ovate, less commonly subpolygonal or polygonal to circular, originating deep within endozone or in curved region, and direct to surface. Zooecial apertures generally ovate and occasionally with lining of concentric laminations.
    Zooecial walls in endozone thin, mostly straight but locally irregular, thickening slowly through curved region in exozone and moderately thick (0.04 mm ZWT) in exozone, occasionally greatly so. Walls composed of translucent laminae, generally sharply pointed where walls are thin and broadly curved where walls are thickened, with dark proximal ends to laminae, and with thin to thick translucent wall lining.
    A few diaphragms in proximal tips of zooecia (5.5 DmmP), then generally absent throughout endozone, and sparse to absent in exozone (1.5 DmmX). Diaphragms in endozone thin and planar, mostly planar in exozone, occasionally inclined, rarely curved and thickened only slightly. Diaphragms continuous into walls as long diaphragm-wall lining units, but not seen merging into wall laminae.
    Mesozooecia numerous (20+ M1M), at almost every wall angle, polygonal to subrounded, originating in outer endozone or early exozone and continuing to surface. Mesozooecia generally well tabulate, long, and presenting striking appearance in longitudinal sections.
    Monticules composed of several megazooecia slightly larger than usual and more numerous mesozooecia than in intermonticular areas.
  • Discussion: The general sparseness to absence of zooecial diaphragms in P. subnodosa is enough to separate it from other Cincinnatian species of the genus. Examination of cotypes of C. pulchella Ulrich (USNM 43525) and the cotypes of subnodosa (USNM 43393) reveals no significant differences between these two forms. Accordingly, we consider that pulchella is a junior subjective synonym of P. subnodosa.

Brown & Daly (1981):

  • ZTM (zooecia in 2mm distance measured parallel to axis of growth) averages 7+ to 6+. This is probably due to its thinner zooecial walls, lack of zooecial lining, and other characters which may affect the ZTM.
  • P. subnodosa has diaphragms sparse to absent beyong proximal tips; it also has thinner walls in the exozone.
  • P. subnodosa is clearly a separate stock. The zooecial wall thickness and the sparseness or even absence of zooecial diaphragms favour separation. Two species reported from the Cincinnatian strata appear to be identical with subnodosa, H. frondosa (Cumings) and P. laevigata Singh.

McFarlan (1931):

  • Zoarium dendroid, 6-12 mm. in diameter. Surface with low rounded monticules composed of apertures larger than normal and more numerous mesopores. Zooecial apertures circular, surrounded by a variable number of mesopores. Diaphragms numerous only in the proximal end of tubes, rare or absent above. Cumings (1908 p. 797) notes considerable variation in the tabulation.
    A common Richmond fossil from the upper Waynesville up.

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