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- C2-C5 Sequences (Dillsboro Formation)
Identification in Hand Sample
- Zoarium Morphology: Massive; acanthopores well developed
- Zoecia: Polygonal; thin-walled
- Mesozooids: None
- Monticules: Low
Brown & Daly (1985):
- Diagnosis: Zoarium ramose, with polygonal zooecia, diaphragms throughout, no mesozooecia, and sparse acanthopores.
- Description: Single zoarium a broken stemlike fragment. On unworn surface a few small flush monticules composed of megazooecia, a few smaller tubes, presumably immature zooecia, and spare medium-sized acanthopores. Zooecia irregularly polygonal, rising in gentle curve from thin-walled endozone, becoming slightly thickened in exozone; new zooecia, enlarging to full size in short distance. Intermonticular zooecia in exozone polygonal and large (7+ in 2 mm, 0.28 mm MZD; table 13).
Walls thin in endozone, irregular to straight, locally flexuous; walls thickened slightly into exozone (0.015 mm ZWT), irregular or straight, generally of obscure structure but locally translucent with poorly developed median line. Diaphragm-wall units thin and dark, but of moderately short length.
Diaphragms abundant throughout, spaced one to three tube diameters apart in endozone, and one-fourth to one tube diameter apart in exozone; typically thin and planar, but commonly concave, convex, or inclined; cystose forms sparse in exozone. No mesozooecia.
Acanthopores sparse (3.2 A1M), of medium size (0.029 mm MAD), moderately well defined, of laminated tissue with a large central lumen, generally at wall angles only in exozone.
- Discussion: The single fragment poses inherent difficulties in the erection of a new species; however, the quantitative data from this specimen do not indicate a close relationship with other forms. Among those of Cincinnatian age, C. osgoodensis Hattin and Perry has much larger zooecia and larger and more numerous acanthopores than C. madisonensis. C. waynensis Utgaard and Perry, in contrast, has smaller zooecia and fewer acanthopores than C. madisonensis. C. bulbosa (Billings) has thinner walls and wider spaced diaphragms. C. polygona Bassler has larger zooecia and apparently lacks acanthopores. Among Middle Ordovician forms, only C. acervulosa (Ulrich) appears somewhat similar; that form has much smaller zooecia, much smaller and fewer acanthopores, and wider spaced diaphragms in the exozone.