Stylophyllopsis sp. A

Stolarski, Jarosław & Russo, Antonio, 2002, Microstructural diversity of the stylophyllid (Scleractinia) skeleton, Acta Palaeontologica Polonica 47 (4), pp. 651-666 : 659-662

publication ID	https://doi.org/ 10.5281/zenodo.13174414
DOI	https://doi.org/10.5281/zenodo.13174504
persistent identifier	https://treatment.plazi.org/id/03D75713-243C-A032-FCE3-F9DAC5DE224E
treatment provided by	Felipe
scientific name	Stylophyllopsis sp. A
status

Treatment

Stylophyllopsis sp. A .

Figs. 9 View Fig , 10A, B View Fig .

Material.— 11 specimens (IPUM−Sic.1, 2, 4, 6–13).

Description.— Corallum trochoid to subcylindrical, variable in shape and size up to 23 × 20 mm in calicular diameter and 45 mm in height; juvenile portions are not preserved (see Fig. 9 View Fig ). Septa hexamerally arranged in 4 full cycles, and some S5inlargerspecimens;septalformulaS1–2>S3>S4>S5.S1–2 extend nearly to calicular center and may be a part of loose axial structure ( Fig. 9B View Fig ). S3 extend to ca. 3/4 of the calicular radius, S4 may reach half of the calicular radius (then often occur short S5) but can be much shorter (then S5 are not developed). Septal spines may dissociate from the lower cycle septa (S1–3) in axial region, but in coralla with damaged uppermost parts, septal spines are distinguishable in sections by bulbous axial septal portions. Septal faces are smooth or, occasionally, covered with minute granulations. In transverse section, septa are spindle−shaped with a well−developed costal part that is covered with pellicular epitheca (e.g., Fig. 10A View Fig 1 View Fig , A 2 View Fig ). Endotheca consists of sparse, arched dissepiments.

The skeleton is diagenetically altered (entirely calcitic as proven by X−ray diffraction). As in Stylophyllopsis sp. cf. S. rugosa , darker and lighter coloration of some distinct structures can be distinguished. Often, in transverse sections of proximal portions of corallum, a distinct mid−septal zone is visible ( Figs. 9B, D View Fig , 10A View Fig 2 View Fig ). This narrow and often dark zone occurs as a semi−continuous “line” in costal parts of septa but in axial septal portions it dissociates into modules, often restricted to the bulbous septal portions ( Fig. 10A View Fig 2 View Fig ). Commonly, several smaller units may be seen within a mid−septal zone; these are much smaller bodies of about 80µm in diameter of dark ( Fig. 9D View Fig ) but also light ( Fig. 10A View Fig 2 View Fig ) coloration. In more distal portions of the same coralla (e.g., Fig. 9C, E View Fig ), the mid−septal zone may still occur in costal portions of septa, but oval structures with diagenetic pattern similar to that in septal spines of Stylophyllopsis sp. cf. S. rugosa (see Fig. 7E View Fig ) often occur there.

Remarks.—Sections of nine Sicilian specimens (IPUM−Sic.1, 2, 4, 6–8, 10–12) show a consistent pattern of skeletal diagenetic alteration. Anarrow, mid−septa zone, often composed of row of about 80 µm bodies, can be seen in transverse sections of septa, particularly from the proximal corallum parts. Small−sized bodies represent, most likely, vestiges of calcification centers. In this respect, Stylophyllopsis sp. A . resembles “minitrabecular” corals (= Caryophylliina sensu Roniewicz 1989 ), in which the mid−septal zone consists of numerous, small−sized calcification centers aligned in a row or zig−zag line ( Fig. 10B View Fig 1 View Fig , B 2 View Fig ; see also Roniewicz 1984; RoniewiczandMorycowa1993).Alsospindle−likeshapesoftransversely sectioned septa strengthen similarity with “minitrabecular” corals (compare Fig. 10A View Fig 2 View Fig and 10B View Fig 1 View Fig , B 2 View Fig ). However, spines that dissociate from adaxial regions of some septa or are distinguished in sections as series of bulbous septal swellings with individual mid−septal zones ( Fig. 10A View Fig 2 View Fig ), suggest transitional minitrabecular−stylophylline skeletal architecture of that species. Diagenetic structures of such spines also resemble those observed e.g., in Stylophyllopsis sp. cf. S. rugosa ( Fig. 7B, E View Fig ).

The Sicilian Stylophyllopsis sp. A . may represent a new species, but it is described under open nomenclature pending revision of various Early Jurassic stylophyllid corals described as “ Montlivaltia ”.

Occurrence.—Early Jurassic (Sinemurian), Sicily.