Bothrophyllum okense Kossovaya, 2001

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 : 26

Bothrophyllum okense Kossovaya, 2001

( Fig. 13B 1–B 4 ).

Material: One preserved corallite (RAh 37), collected from the basal shales of lower member of the Aheimer Formation. Three transverse thin-sections are available.

Description: External characters: The corallite is ca. 20 mm in length. Calyx and apical end parts of are largely eroded. The external wall is partly damaged, eroded and enclosed in fossiliferous mud ( Fig. 13B 1 ). The outer wall of the corallite in cross section is irregular.

Internal characters: The early preserved growth stage ( Fig. 13B 2 ), in a diameter of 14 mm there are 30 major septa. All major septa are long, some reach more than 2/3 of the corallite radius, leaving a small axial area which is filled with a diagenetically altered axial structure formed from the axial ends of the major septa and axial tabellae. Septa are strongly thickened in the tabularium, but thin in the very narrow dissepimentarium that consists of two rows of dissepiments. In the following higher section ( Fig. 13B 3 ) cardinal and counter septa are long and meet in the corallite center forming an axial septum that contributes with other septal axial ends in making a loose axial structure. At this stage, there are 31 septa for about 14 mm. In the higher mature thin-section near the eroded calice ( Fig. 13B 4 ), all septa are broken due to the compaction of the calicular part. There are about 34 septa in 13.5 mm compressed diameter. The counter septum is still long and reach the corallite centre, in contrast to the cardinal septum that seems to be shorten ( Fig. 13B 4 ). The axial structure that formed of the axial tabellae and inner ends of the longest major sept is still present. In a fairly good-preserved part of the corallite wall, a narrow dissepimentarium composed of 2 rows of simple concentric inter-septal dissepiments is present ( Fig. 13B 4 ). Cardinal fossula is poorly developed. Minor septa are very short, confined to the dissepimentarium in the mature section ( Fig. 13B 4 ), enter the tabularium as thick pegs.

Discussion: The specimen shows greatest similarity to Bothrophyllum okense Kossovaya, 2001 from the Moscovian of the Moscow Basin in Russia, despite the incomplete preservation and the diagenetic alteration of the skeleton of the current species. It was compared with the Egyptian slightly older bothrophyllids (Rod EL Hamal Formation) and with other Moscovian and Kasimovian Bothrophyllum spp. from the type region of the Moscow Basin have been discussed by Kora et al. (2019; Table 1 ).

Figures

Fig. 13 A Ufimia sp. A1 External view of the specimen RAh (101), showing a straight conical corallite with eroded calice rim and apex. Positions of thin-sections indicated. A2–A3 Two successive transverse thin-sections in the mature part of the corallite show the thick, rhopaloid major septa meet in the corallite centre. Scale bars:A1: 5 mm; A2, A3: 2 mm. B Bothrophyllum okense Kossovaya, 2001. B1 External view of the partly preserved corallite (RAh 37), with partly eroded wall. Positions of thin-sections indicated. Successive transverse thin-sections from the lower less mature part in B2 up to the more mature section below the calice in B4, the transverse sections show the axial septum and a very narrow dissepimentarium. Scale bars: 5mm

Fig. 1 Geological map of the eastern cliffs of the Northern Galala Plateau, modified after Abdallah and El Adindani (1965)

Fig. 4 Effects of diagenesis on some coral specimens: A Thin-section in the calice of the specimen RAh (44) shows a completely compressed calice filled with fossiliferous mud. B Thin-section below the calice of the Bothrophyllum okense (RAh 37) shows beginning of compression and breakage of septa. C Thin-section below the calice of the specimen RAh (79), shows completely broken and altered septa, probable outer dissepimentarium and axial structure, filled with ferruginous mud. D Thin-section of a completely compressed specimen RAh (200) shows high alteration,breakage and ferrugination of skeletal elements.E Thin-section in the early mature part of the Actinophrentis crassithecata n. sp.(RAh 11), shows ferrugination affects a large part of the interior skeleton. F Mature thin-section of Rotiphyllum exile (RAh 29), shows ferrugination and dolomitization of skeletal elements.G, H Thin-sections of mature part of the specimen (RAh 81) in G and the immature part of the specimen RAh (99) in H show extensive dolomitization and ferrugination of the internal skeletal elements

Fig. 2 A Lithostratigraphic succession of the Aheimer Formation studied along the eastern cliffs of the Northern Galala Plateau after Kora and Mansour (1992). B Enlargement of the mudstone dominated basal shale part of the lower member of the Aheimer Formation studied herein (see also Fig. 3A)

Fig. 3 Field aspects of the Aheimer Formation; A General view of the studied succession of the lower member exposed in a faulted block to the north of Porto Sukhna; the shales mudstones close to the base (rectangle) are interbedded with thin, hard dolomitic bands. B Close up view on of the lower fossiliferous shale mudstone beds of A. C, D Close-up view on of two rugose corals entombed in the shale mudstone beds.E Close-up view on of a rugose coral species with diagenetically compressed calyx. Note strong ferrugination of corallite and surrounding matrix within the fossiliferous shale. F Fossiliferous shales mudstone with thin bands of ferruginous dolomitic limestone and secondary evaporite veinlets; Cr = crinoidal stems. G Crinoid columnals (Cr) and rugose corals (RC) are embedded in the shale mudstone. H Close-up view on of a spiriferid valve shell within the shale (arrow). Diameter of coins in C–E, G: 25 mm