Type Species: Chaetetes venusta (Ulrich, 1878)
Species found in the Cincinnatian, USA
- Crepipora impressa (Ulrich, 1890)
- Crepipora simulans (Ulrich, 1890)
- Crepipora solida (Ulrich, 1890)
- Crepipora venusta (Ulrich, 1878)
Middle Ordovician (?Chazy., Mohawkian) – Late Ordovician (Richmondian)
- C5 Sequence (Fairmount)
- C4 Sequence (Clays Ferry: Southgate: Economy)
Identification in Hand Sample:
- Hollow branches
- Autozooecia with cavity subangular to subcircular, moderately small, commonly rhombically packed
- Boundary irregular, sinuous; forming broad, dark zone
- Pores with larger diameter at one end
- Mesopores generally restricted to the maculae, which are elevated or depressed
Crepipora from the Whitewater Formation of Ohio (CMC 56395)
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Holland (UGA Strat Lab, 2013):
- Genus has hollow branches.
Treatise on Invertebrate Paleontology Part G (1983):
- Zoarium encrusting expansions, hollow ramose or solid ramose with conspicuous monticles. Autozooecia with cavity subangular to subcircular, moderately small, commonly rhombically packed. Wall laminae short, irregular; not concentric around living chamber. Boundary irregular, sinuous; forming broad, dark zone. Communication pores abundant in outer endozone and exozone; subcircular in cross section. Proximal surface of pore perpendicular to wall, distal surface commonly oblique, pores with larger diameter at one end; locally, both surfaces parallel and oblique to wall. Lunaria moderately large in endozone of ramose zoaria, moderately small in inner endozone of zoaria with basal layer; lunaria becoming slightly larger in outer exozone, ends in some projecting into autozooecial cavity. Radius of lunarium conspicuously smaller than radius of autozooecium. Central core or cores in many lunaria. Diaphragms thin to thick, irregularly spaced. Exilazooecia never abundant, commonly rare or absent in intermonticular areas; walls commonly thinner than in autozooecia. Communication pores present but less common in walls between adjacent autozooecia. Diaphragms rare in exilazooecia. Acanthostyles small, few to many in monticular exilazooecial walls, rare, usually lacking in autozooecial walls in intermonticular areas. Monticules having core of small to large, circular to irregularly shaped exilazooecia, acanthostyles, and ring or marginal zooecia slightly larger than intermonticular autozooecia. Lunaria in some areas partly radially arranged. Monticular centers rarely subsolid.
- Type species.–Chaetetes venustus Ulrich, 1878, by subsequent monotypy, Ulrich, 1882b, p. 257. The change in the type species makes little change in the generic concept. C. venusta differs from C. simulans mainly in the shape of the colony, which is probably not a generic character in this group of bryozoans. The original description of the genus read (Ulrich 1882a, p. 157): “Usually incrusting, sometimes irregularly ramose with hollow branches. Cell-apertures very little oblique, rhomboidal, with a slightly projecting “lip.” Interstitial cells usually restricted to the “maculae,” which are distributed at rather regular intervals over the surface. Two delicate longitudinal lamellae are present in each tube. Diaphrams are developed in moderate number.
- The “projecting lip” and the “longitudinal lamellae” both refer to the same structure, the lunarium, being crescent-shaped in cross section.
- Remarks.-Several species from the Middle Ordovician to the Silurian have been referred to Crepipora. It is outside the scope of this paper to discuss all of them and their affinities. A group of species with thin, granulose walls and generally small lunaria must be excluded from the genus (i. e. C. perampla Ulrich 1893, and C. subaequata Ulrich 1893). C. incrassata Bassler 1911, and probably C. lunatifera Bassler 1911 differ also too much from the type species to be included in the genus. C. lunariata Henning 1908, the only well-known Silurian species, is rather like the type species, differing from it only in zoarial shape and in having acanthopores in the maculae.
- The details of the interior, especially the wall structure, have not been studied in sufficient detail in most ceramoporoids, and it is, therefore, premature to attempt a classification of the family. In addition to the microstructure of the zooecial walls, the structure of the maculae might be of major taxonomic importance. Borg (1944) referred the Ceramoporoids to his division Calyptrostega of the Stenolaemata. If this assignment is right, the maculae might represent the cover of the zoarial broodchamber, and be of considerable taxonomic importance.
- The sharp division of the walls into an exozone and an endozone might be a reflection of the zoarial shape, and this problem must be studied further before much taxonomic importance is ascribed to this feature in the ceramoporoids. It is not certain if these zones correspond to similar appearing zones of the trepostome bryozoans, or if they correspond to the inner and outer part of the exozone in the trepostome genus Trematopora (Boardman 1959).
- Zoarium incrusting lamellate or massive, or in one species forming hollow branches; zooecia long, tubular, thin-walled, with diaphragms; apertures angular or subpyriform, lunarium not overarching, its ends usually projecting; mesopores generally restricted to the maculae, which are elevated or depressed.
- Genotype.—Crepipora simulans Ulrich. Upper Ordovician (Maysville) of the Ohio Valley.
- Crepipora is closely related to the genus Ceramoporella, incrusting forms of the former being very similar to such species as Ceramoporella uxnormensis described on page 82. Perhaps the most obvious generic difference is the practically complete restriction of the mesopores to the maculae in Crepipora, although other equally good characteristics are the more direct zooecial apertures, the better-developed maculae, and the greater distinctness of the lunarium.
- The zoarial growth in Crepipora varies from thin, incrusting sheets to solid massive or hemispherical, and in one case regular hollow branches. The surface shows thin-walled, erect, rhomboidal to polygonal zooecia, each having a small but distinct lunarium on the proximal edge. Maculae of mesopores developed at regular intervals are a feature of the surface, where they appear as minutely porous elevations or depressions. In thin sections, the maculae and lunaria are most evident, although the ceramoporoid structure described under the discussion of the family is likewise conspicuous.
- At least 15 new or described American species of Crepipora are known, and these, in addition to the three new forms here defined , make the genus one of the more prolific members of the Ceramoporidae. The three Russian forms have little relationship with each other specifically but are good examples of the range of structure in the genus. The first, C. schmidti, is closely related to the genotype C. simulans, from the middle Cincinnatian strata of the United States, differing particularly in having considerably larger zooecia. The second species is unusual in the irregular angularity of its zooecia, its very distinct crescentic lunarium, and the unusual development of mesopores. C. incrassate has particularly thick walls, but a quite unusual character seen only in this species, so far as known, is the rounded, ovicell-like structure noted in the thin sections of the type-specimen.
- The occurrence of these cystlike bodies in an undoubted species of Crepipora is of great interest in its bearing upon the zoological position of the ceramoporoids and related monticuliporoids. These two groups, together with the fistuliporoids, have been assigned to the alcyonarian corals by most writers, but with the present discovery in Crepipora, ovicell-like structures are now known to occur in representatives of each group. This fact, together with others indicating the bryozoan relations of these disputed organisms, will be discussed in another paper at a later date.
Nickles & Bassler (1900):
- Zoarium encrusting, lamellate or massive, or, in one species, forming hollow branches; zooecia long, tubular, thin-walled, with diaphragms; aperatures angular or subpyriform, lunarium not overarching, its ends usually projecting; mesopores generally restricted to the maculae, which are elevated or depressed.
- Genotype: Crepipora simulans Ulrich. Ordovician. Eight described and six new species.