Phylum: Bryozoa
Class: Stenolaemata
Order: Trepostomatida
Family: Halloporidae
Genus: Hallopora Bassler, 1911
Cincinnatian Species: Hallopora andrewsi

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Type Species: Callopora elegantula (Hall, 1852)Species found in the Cincinnatian (Bryozoa.net)

  • Hallopora congrua (Utgaard & Perry, 1964)
  • Hallopora elegantula (Unknown)
  • Hallopora multitabulata
  • Hallopora onealli (James)
  • Hallopora rugosa
  • Hallopora ramosa
  • Hallopora andrewsi (Nicholson)
  • Hallopora subnodosa (Ulrich)
  • Note: Probably all species referred to as Hallopora from the type Cincinnatian are actually Parvohallopora. (Holland, 2013)

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Stratigraphic Occurrences


Geologic Range
Ordovician – Devonian

Geographic Occurrences

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Sequences (Formations)

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

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Identification in Hand Sample:

  • Zoarium Morphology: consists of branches with bushy clumps
  • Zoecia: round to oval
  • Monticules: absent
  • Maculae: absent

Species Differentiation

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Corneliussen and Perry (1973):

  • Hall’s original description (1852, p. 144) of Callopora (non Gray, 1848, p. 109,146) included ramose or encrusting forms having a columnar structure or form; zooecia rarely septate, the zooecial apertures circular or petaloid but not contiguous; and intermediate spaces occupied by angular transversely septate mesopres. Bassler (1911, p.325) added to Hall’s original definition as follows: “… the zoaria are almost always solid ramose and bushy… the apertures are closed by perforated, ornamented covers which, as growth proceeds, form the diaphragms of succeeding layers.” Ross (1969, p. 270-271) restudied the type species, Hallopora elegantula (Hall) and presented an emended diagnosis of the genus.

Fritz (1965):

  • The branches are solid and somewhat flattened, largest diameter observed 7 mm. All specimens are embedded in a highly, fossiliferous crystalline limestone. Since bryozoa cannot be freed from the matrix the surface of the bryozoans cannot be observed. From thin section, however, it would seem that neither the maculae nor monticules are present. In tangential thin section, the zooecia are round to oval, five to six or seven are present in the space of 2 mm.; angular mesopores, varying in size, surround the zooecia, usually in one row, but more may occur.
  • In longitudinal thin section the zooecia and mesopores curve gently to the surface and open, for the most part, directly; wall structure completely crystallized, but walls thinner in the axial than in the mature region; four or five diaphragms (a few oblique) occur in the mature region, although one tube shows seven; diaphragms apparently absent in the axial region; mesopores with many closely spaced diaphragms.

Treatise on Invertebrate Paleontology, Part G (1953):

  • Ramose; intertwined branches may form clumps 30 cm. wide. Zooecial apertures commonly closed by ornamented perforated covers which become diaphragms when left behind during growth.

Bassler (1911):

  • Unfortunate as it may seem to the paleontologist, the well-known generic name Callopora Hall must, according to the rules of nomenclature, be replaced by another term. Nickles and Bassler recognized the facts, and in their Synopsis of American Fossil Bryozoa published the following:
    • In 1848 Gray (Proc. Zool. Soc. London, Appendix, 1848, and List of British Animals in the collection of the British Museum, 1848, pp. 109, 146) proposed the generic term Callopora for a single species, the Flustra lineata of Linnaeus, but the term failed to gain acceptance, and the species lineata is now considered to be a Membranipora. As Callopora Hall has become deeply engrafted into literature, it seems undesirable under the circumstances to replace it by a new name.
  • However, Gray gave a description of his genus, poor as it may be considered from the standpoint of today, and the important point of his work is that he selected a type species. Callopora must, therefore, stand based upon this species, even though more recent work should prove it to be a Membranipora. Such excellent authorities in the study of recent Bryozoa as Levinsen and Norman have worked out the details of Gray’s Callopora lineata and consider the genus a valid one.
  • In the view of the above, I propose the name Hallopora in honor of the distinguished paleontologist James Hall, to replace his Paleozoic genus Callopora. This new name seems most appropriate in commemoration in a small way of Professor Hall’s work upon fossil Bryozoa, and particularly upon this generic group.
  • The zooaria of Hallopora are almost always solid ramose and bushy. In the perfect state the apertures are closed by perforated, ornamental covers which, as growth proceeds, form the diaphragms of succeeding layers.
  • Genotype.—Callopora elegantula Hall. Early Silurian of America and Europe.

Nickles & Bassler (1900; Under Callopora):

  • Zoarium usually ramose, the branches frequently anastomosing and forming bushy clumps; zooecia at first prismatic, four to eight sided, gradually becoming cylindrical in most cases; at first with closely set diaphragms, then diaphragms more distant, finally in the mature region diaphragms usually closely set; apertures closed at times by perforated, often ornamented covers; mesopores more or less numerous, angular, crowded with diaphragms

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H. andrewsi