Taxonomic History (Nickles & Bassler, 1900)
- 1883 Atactopora typicalis Ulrich, Jour. Cincinnati Soc. Nat. Hist., VI, p. 248, pl. xii, 3-3d.
- 1895 Atactopora typicalis J.F. James, Jour. Cincinnati Soc. Nat. Hist., XVIII, p. 80.
- 1896 Atactopora typicalis Ulrich, Zittel’s Textb. Pal. (Engl. ed.), fig. 450, (p. 272).
- 1897 Atactopora typicalis Simpson, Fourteenth Ann. Rep. State Geologist New York for the year 1894, figs. 165-167 (p. 585).
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- C1 Sequence (Clays Ferry/Kope: Economy/Fulton)
Identification in Hand Sample
- Zoarium Morphology: Thin, parasitic expansions (often encrusting on other bryozoa). Thickness of each layer typically no more than 0.03 inches. Some lobate to subramose.
- Zoecia: Floriform apertures, small spines at the wall; regularly arranged in intersecting series; numerous very small acanthopores
- Mesozooids: Numerous, but difficult to see externally
- Monticules: Low, rounded, arranged at unequal intervals; sometimes not elevated
- Maculae: Cells slightly larger than average
Atactoporella typicalis from Decorah Formation of Decorah, Indiana. (CMC 597)
Holland (UGA Strat Lab, 2013)
- Atactoporella is typically encrusting, but can also be ramose to massive. Zooecia are thin-walled and bear diaphragms and cystiphragms, which often form overlapping series. Mesozooids are large and numerous, almost isolating zooids and bearing numerous diaphragms. Styles very numerous, causing zooecial openings to be petaloid.
- Compared with other species, A. typicalis is readily distinguished by the exceedingly tenuity of the zooecial walls, and the greater projection inward of the acanthopores. The latter are more numerous than in any of the other Minnesota species known.
- Zooarium (in it’s typical condition) forming thin parasitic expansions over other bryozoa, having a thickness rarely exceeding 0.03 of an inch, and then only by the addition of another layer. A few specimens are lobate, and by an excessive development of the lobes, they have become, to a small extent, subramose. At rather unequal intervals, averaging perhaps 0.1 inches, the surface exhibits groups of cells slightly larger than the ordinary, which may be raised into low, rounded monticules, or remain on a level with the surrounding plane of the surface. Cells regularly arranged in diagonally intersecting lines, about 12 in the space of 0.1 inches, separated by interspaces, usually of less width than the diameter of their orifices, which has averages of about 0.001 inch. Cell apertures are distinctly floriform, the wall at each of the indentations, being raised into a small spine, representing the surface extension of the spiniform tubuli. Interstitial cells numerous, but not readily recognized externally, being shallow, and much obscured by the spiniform tubuli…
- This species differs from all the other species of the genus now known, in its greater regularity of cell structure, and more numerous interstitial tubes.