Monophyllum galalaensis, El-Desouky & Herbig & Kora, 2023

El-Desouky, Heba, Herbig, Hans-Georg & Kora, Mahmoud, 2023, Kasimovian (late Pennsylvanian) cornute rugose corals from Egypt: taxonomy, facies and palaeogeography of a cool-water fauna from northern Gondwana, Swiss Journal of Palaeontology (32) 142 (1), pp. 1-39 : 18-19

publication ID	https://doi.org/ 10.1186/s13358-023-00296-0
DOI	https://doi.org/10.5281/zenodo.12783851
persistent identifier	https://treatment.plazi.org/id/49386916-7F08-FFEA-FF2B-FAD2FE64FCE8
treatment provided by	Felipe
scientific name	Monophyllum galalaensis
status	sp. nov.

Treatment

Monophyllum galalaensis n. sp.

( Fig. 9A View Fig 1–A View Fig 82 View Fig , B 1–B View Fig 6 View Fig , 12B View Fig ).

Derivation of the name: From the type locality (eastern cliffs of the Northern Galala Plateau ) .

Holotype: Specimen RAh 9 ; collected from the basal shales of the lower member of the Aheimer Formation and illustrated in Fig. 9A View Fig 1–A View Fig 82 View Fig . Six transverse thin-sections are available.

Material: Paratypes are represented by five partly preserved corallites (RAh 13, RAh 41, RAh 52, RAh 80 and RAh 92); collected from the lower shales of the Aheimer Formation. The internal structures of these corallites are diagenetically altered. Eighteen transverse thin-sections are available, four of them belonging to RAh (13) are extremely altered by diagenesis and thus excluded from illustrations.

Type locality: Eastern cliffs of the Northern Galala plateau (Lat. 29° 28 ′ 01 ″ N and Long. 32° 27 ′ 38 ″ E) GoogleMaps , northern Eastern Desert, western side of the Gulf of Suez, Egypt.

Type horizon: Basal shales of the lower member of the Aheimer Formation; Upper Pennsylvanian (Kasimovian).

Diagnosis: Monophyllum having maximum n:d ratio 24:11. Major septa meet in the corallite axis forming a stereocolumn; they retreat near the calice floor, forming a small free axial area occupied only by the incipient columella resulting from the elongated counter septum. Cardinal septum moderately shortened from early maturity.

Description: External characters: Corallites are ceratoid, about 2.2– 3 cm long. Calyx and apex are not preserved in the holotype ( Fig. 9A View Fig 1 View Fig ) but preserved in most of the paratype specimens ( Fig. 9B View Fig 1 View Fig ). When preserved, calyx is deep and laterally compressed. A remarkably long counter septum that forms an incipient columella with its end can be detected on its floor ( Fig. 9A View Fig 2 View Fig ). Delicate growth lines and distinct septal furrows are visible in the good preserved external wall ( Fig. 9A View Fig 1–A View Fig 2 View Fig ).

Internal characters: The young stages of ontogeny are described from the paratype specimen ( Fig. 9B View Fig 2–B View Fig 3 View Fig ), where the apical part is well-preserved. In the earliest ontogenetically preserved section (nepionic stage) of the paratype RAh (13) only 3 protosepta can be traced in about 1 mm diameter ( Fig. 9B View Fig 2 View Fig ). The subsequent section records the early neanic stage ( Fig. 9B View Fig 3 View Fig ), where there are 14 major septa in 2.5 mm diameter, all meet near the corallite axis with their thick inner ends. The subsequent neanic growth stages of the paratype have n:d of 19–22: 5–6.7 mm. These sections are not suitable for illustration as stated before.

The two earliest preserved ontogenetic sections of the holotype have 21–22 septa in 6–6.5 mm diameter ( Fig. 9A View Fig 3–A View Fig 4 View Fig ). In this stage major septa are thick, except for the cardinal septum. The counter septum is slightly thicker than the others and is longer. Septa are pinnately to sub-radial arranged and meet in the centre to form a stereocolumn. Minor septa are mostly missing. In the successively youngest sections ( Fig. 9A View Fig 5–7 View Fig View Fig View Fig , B 4 View Fig ), major septa count 23–24 in 8–10.5 mm diameter. They are joined with their thickened axial ends to form a dense axial column, with a narrower free axial area. The counter septum is the longest and exceeds all the majors in the axial stereocolumn with a rhopaloid thickened end. Cardinal septum thins towards the axis ( Fig. 9A View Fig 5 View Fig ), immediately becoming short, situated within a triangular, adaxial open cardinal fossula, which is located on the concave side of the corallite ( Fig. 9A View Fig 6–7 View Fig View Fig ). Alar fossulae are not visible. In the last mature sections, below the calice floor ( Fig. 9A View Fig 81 View Fig , 2 View Fig , B 5 View Fig ), and within the calice ( Fig. 9B View Fig 6 View Fig ), major septa are a little withdrawn from the axis and a narrow free axial area is developed that disappears in the lower, less mature sections. They are radially arranged. Minor septa are underdeveloped and form small triangular spikes at the inner wall. However, the long rhopaloid counter septum, incipient columella, and the short cardinal septum in the triangular fossula are still developed. The arrangement of the major septa changes from radial to pseudo-radial and then pinnate when going down towards the successively older parts of the corallite.

Discussion: The species discussed differs from the Upper Moscovian type species Monophyllum sokolovi Fomichev, 1953 in the strong elongation of the counter septum up to the calice floor, forming an incipient columella. Monophyllum parvum Fomichev, 1953 differs in its smaller n:d ratio ( Fig. 12B View Fig ). The current species differs from M. cassum Fedorowski, 1987 by its larger n:d ratio (24:11.5 vs. 22:9.3). In addition, M. cassum shows withdrawing of major septa from the corallite axis already in the late neanic/early ephebic stage, while this happens in the late ephebic stage near or at the calice floor in the Egyptian species. The formation of a stereocolumn is missing in M. cassum .