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- C1 Sequence (Lexington/Pt. Pleasant)
Identification in Hand Sample
- Zoarium Morphology: Flattened discoidal to subconical; occasionally lobate; wrinkled epitheca on under surface; base concave; presence of a small, conical, sharp pointed groove on epitheca; diameter usually smaller than P. simulatrix (~2mm)
- Zoecia: Subcircular; generally surrounded by angular mesopores; acanthopores present, but not numerous or strong
- Mesozooids: Small, angular abundant
- Maculae: Conspicuous with larger apertures and more numerous mesopores
Diagnosis: Colloquially referred to as “Chocolate Drop” bryozoans, because the morphology of their zoaria resembles the shape of a Hershey’s Kiss.
- Description — Zoaria discoidal to hemispherical, variable in size, approximately 10-100 mm wide at base, 10-30 mm high on the average, commonly with concave lateral surfaces locally. Zoarial basal layers exceedingly thin, imperforate, thinly laminated or nonlaminate locally. Basal layers occasionally bifurcated in some zoaria, extending distally, forming mesothecalike budding surfaces from which autozooecia bud in opposite directions. Endozones narrow, indistinct. In endozones, autozooecia recumbent for short distances, becoming erect at base of exozones, generally extending distally at right or slightly oblique angles to basal layers. In exozones, autozooecia erect in zoarial centers, slightly curving outward laterally, occurring at right angles to zoarial surface, sparingly intercalated in inner exozones, more commonly in outer exozones; arising occasionally from mesozooecia; zones of autozooecial rejuvenation sparse.Autozooecia straight to slightly sinuous, subpolygonal to subcircular in cross section, without preferred alignment, partly contiguous, separated by mesozooecia, locally contiguous in outer exozones. Autozooecial walls generally thin, approximately 0.01-0.02 mm thick on the average, thickened locally by styles. Autozooecial boundaries narrowly serrated throughout zoaria. Styles common, scattered, occurring generally in autozooecial and mesozooecial corners, occasionally inflecting zooecial walls, projecting locally into zooecial chambers. Style cores exceedingly thin, nonlaminated; sheaths laminated, variable in thickness; sheath laminae occasionally transecting cores locally. Cystiphragms abundant, occurring generally in longitudinal, rarely superimposed series, extending approximately two-thirds to three-fourths of circumference of autozooecia, locally around entire autozooecium. Cystiphragms occasionally occurring singly or lacking locally in outer exozones of some autozooecia. Basal diaphragms abundant, planar or slightly curved, concave distally, occurring at right angles to chamber axis, abutting autozooecial walls and cystiphragms; generally evenly spaced, occasionally scattered or lacking in late exozones of some autozooecia. Mesozooecia common to abundant, polygonal to subpolygonal in cross section, variable in size, partly separating, locally surrounding autozooecia in intermacular areas, occurring in clusters in maculae. Mesozooecia arising and terminating throughout exozones, terminating more commonly in outer exozones, occasionally extending distally as autozooecia. Mesozooecial walls straight or slightly inflected at junctions with diaphragms, locally thickened by styles. Mesozooecial diaphragms abundant, evenly and closely spaced. Maculae common, generally on level with zoarial surface, centers approximately 3-4 mm apart, occurring in rhombic pattern. Maculae consisting of clusters of mesozooecia, variable in size, at centers and of polymorphs slightly larger than autozooecia in margins, intergrading gradually in size with autozooecia. Chambers of polymorphs generally extending along zooecial walls facing centers of maculae.
- Discussion of the differences between P. falsei and P. simulatrix:
- Remarks — Prasopora falesi characteristically has distinct small and relatively large styles as well as abundant mesozooecia throughout intermacular areas and in clusters in maculae and proximately onlapping cystiphragms in regular series, extending two-thirds to three-fourths the circumference of autozooecia (cystiphragm type 1 of Ross, 1967a, p. 406) in most parts of exozones. Cystiphragms, however, occasionally occur singly and are restricted laterally in outer exozones of autozooecia of P. falesi. P. falesi is closely related to P. simulatrix Ulrich. The species are similar in their hemispherical growth habits, the shape and size of their autozooecia, the distribution of their basal diaphragms, the shape and general arrangement of their cystiphragms, and their polymorphism. P. falesi differs from P. simulatrix, however, in having distinct styles throughout exozones. Styles in P. simulatrix (acanthopores of Bork and Perry, 1968b, p. 1058) are commonly lacking, or are exceedingly small and occur, sparingly, only in peripheral parts of zoaria (the acanthoporelike structures of Ross, 1967a, p. 412). P. falesi and P. simulatrix both have cystiphragms of type 1 of Ross (1967a). P. falesi, however, differs from P. simulatrix in having cystiphragms that occasionally occur singly or in pairs and are locally restricted laterally. Both species have numerous mesozooecia that partly separate autozooecia, but P. falesi has fewer mesozooecia than P. simulatrix. P. falesi has approximately 20 mesozooecia per unit of area in exozones (tables 18-20), whereas P. simulatrix has approximately 27 (Bork and Perry, 1968b, tables 12-14).
- Resemble small individuals of P. simulatrix, characterized by the presence of a conical, sharp pointed groove impression on the wrinkled under surface. Distinguished by its smaller size (~2mm in diameter), flatter form, weaker epitheca, and the presence of small acanthopores.