History (Nickles & Bassler, 1900)
- 1882 Ptilodictya maculata Ulrich, Jour. Cincinnati Soc. Nat. Hist., V, p. 163, pl. vi, 17, pl. vii, 4, 4a.
- 1890 Ptilodictya maculata Ulrich, Geol. Surv. Illinois, VIII, fig. 6b (p. 317).
- 1893 Escharopora maculata Ulrich, Geol. Minnesota, III, p. 167.
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- C2 Sequence (Fairmount)
- C1 Sequence (Cynthiana)
Identification in Hand Sample
- Zoarium Morphology: Unbranching, simple “frond”; more robust: width up to 4mm, length up to 13 mm, thickness 2-3mm
- Zoecia: Sub-elliptical; arranged diagonally in intersecting series (angles between 50* and 80*)
- Mesozooids: Few
- Monticules: Conspicuous, elevated
- Maculae: Several mm apart, composed of larger apertures
Escharopora maculata from the Kope Formation of Maysville, Kentucky (OUIP 2413)
Holland (UGA Strat Lab, 2013):
- Forms flaring fronds, intermediate in shape between E. falciformis and E. pavonia.
- E. maculata: A more robust form. Width up to 4 mm, length up to 13 mm, thickness 2-3 mm. Characterized by conspicuous, usually elevated, maculae several mm apart, composed of larger apertures
- Zoarium consisting of single, unbranched, flattened, two-edged frond, which is more or less curved, and gradually expands from the pointed articulating “head” upwards. The width of the frond above varies in different examples from one-half an inch to one and a half inches. The total length may exceed five inches, while the greatest thickness of a robust specimen does not exceed one-tenth of an inch. From one to two-tenths of an inch above the extremity of the striated and more or less pointed articulating process, the zoarium suddenly expands and forms a kind of shoulder. Cells rhomboidal or hexagonal, with oval or circular apertures, and arranged in intersecting diagonal lines, the regularity of which is interrupted at intervals of about .1 inch, by groups of cells or a larger size than the average, which occupy slight elevations of the surface. Between these groups, about twelve cells occupy the space of .1 inch. Walls of cells at the surface moderately thin. Sections show that the walls are thick and perforated by connecting foramina, and diaphragms are developed at corresponding levels in contiguous tubes. In tangential sections the cells are usually, irregularly petaloid; the pseudo-septa number in each tube from one to five.
- The characters of this species are intermediate between those of P. falciformis, Nicholson, and P. pavonia, D’Orbigny. From the former, it is distinguished by its much more robust fronds, and groups or larger-sized cells. From the latter, it is separated by its comparatively narrow fronds, which never expand so irregularly, nor nearly so much as those of P. pavonia.
- In this connection, it is proper to consider the characters of Ptilodictya pavonia, D’Orb., since Dr. Nicholson (“Monticulipora,” p. 196, 1881), has questioned my view of the affinities of this species. D’Orbigny originally referred the species to the genus Ptilodictya, which course I believe to have been unquestionably correct. In his discussion of the subject, Dr. Nicholson says (loc. cit.): “This beautiful form presents a considerable superficial resemblance to Ptilodictya and has been referred to this genus. It wants, however, the definitely circumscribed and peculiarly marked lateral margins of the fronds of the Polyzoan type; and, what is more important, it is without the peculiarly striated central lamina of the Ptilodictya. It is true that the bases of the corallites in M. pavonia, D’Orb., are so united with one another as to give rise to an irregular calcareous membrane, which separates the two halves of the corallum; but none of the specimens that I have seen exhibit any tendency to split along the line of this membrane, nor can the corallites be forcibly removed from one side of it, exposing the median lamina as a definitive structure. In both these respects, the Ptilodictyae would show quite different phenomena.” The first character – i.e. the nonporiferous margin which Dr. Nicholson erroneously regards as lacking in P. pavonia – is, of course, not developed along the growing margin of the fronds, but in all specimens preserving the “articulating process,” the non-poriferous margin may be traced along the edges of the lower portion of the frond. The non-poriferous margin in P. pavonia (Plate VII, fig. 3a), is precisely like that of either P. falciformis or P. maculate. Judging from the above quotation, it would appear that Dr. Nicholson has entirely misconceived the character of the median laminae of the Ptilodictyonidae. If I understand him correctly, he believes that the exis is constituted by a definitive structure from which the two layers of cells may be striped. This impression is manifestly erroneous, nor do I know of a single double-leaved Bryozoan in which such a structure may be demonstrated. In Ptilodictya the facets are, simply, that we have two layers of cells which are grown together back to back by the adhesion of the epithecal laminae of each layer. This fact may be readily demonstrated either in thin sections of fractures. In both tests, the characters presented by P. pavonia, are precisely like those observed in other species of the genus. On plate VII., figs. 3 and 3a, are represented two specimens of P. pavonia, both of which preserve a portion of the frond and the articulating process. The importance of the fact that this species possesses a jointed zoarium can not be overestimated, since it completes the chain of evidence that established the near relationship of P. pavonia to some of the more typical species of the genus.