Zaphrentites cf. parallela (Carruthers, 1910)

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 : 21-24

Zaphrentites cf. parallela (Carruthers, 1910) .

( Fig. 11A 1–A 3 , B 1–B 4 , 12D ).

cf. 1910 Zaphrentis parallela Carruthers. - p. 533, Pl. 37, Fig. 4 .

cf. 2014 Zaphrentites parallela (Carruthers) .- Denayer and Hoşgör, p. 350, Fig. 4 : 6a–d, 14 (cum syn.).

Material: Three corallites (RAh 109, RAh 111 and RAh 118); collected from the basal shales of the lower member of the Aheimer Formation. Nine transverse thin-sections are available.

Description: External characters: Straight, conical corallites, about 1.5 cm long, slightly curved in the immature stage. Calyx is largely eroded, apex not preserved. Septal furrows and delicate growth lines are distinctly marked on the external wall ( Fig. 11B 1 ). An attachment scar is visible in one corallite near the apical part.

Internal characters: In the earliest ontogenetic preserved stage ( Fig. 11A 1 ), septa are very thick, reaching the corallite axis. There are 16 septa at a corallite diameter of about 3 mm; of them the counter septum is the thickest. At diameter of 3.7 mm ( Fig. 11B 2 ), major septa are still thick, they join in the centre forming a thick stereocolumn; a parallel sided cardinal fossula can be recognised. In the subsequent early mature growth stage at a diameter of 5 mm, there are 20 major septa ( Fig. 11A 2 ). Minor septa are absent. The axial ends of major septa join to form an axial stereocolumn slightly staggered towards the counter quadrants. Septa of the counter quadrants are radially arranged, the counter septum is slightly thicker and has the same length as the adjacent septa. Those in the cardinal quadrants are grouped pinnately around a long parallel sided cardinal fossula. The thin cardinal septum is straight, long and reaches beyond the corallite axis to join the stereocolumn at the upper end of the cardinal fossula in the counter quadrants. It further thins towards the axis. Further mature, at a diameter of 6.5 mm, there are 21 septa ( Fig. 11B 3 ); the cardinal septum becomes slightly shorter.

The uppermost mature transverse section near the calice floor ( Fig. 11A 3 , B 4 ) is slightly deformed due to compaction and some of the septa are broken. In this stage there are maximum 26 septa in 8.6 mm ( Fig. 11B 4 ). Axial ends of the major septa in cardinal quadrants are bent to sides with the two pericardinal septa, curved most distinctly. Such septal morphology makes the cardinal fossula opens towards the free axial area. The cardinal fossula is slightly deformed. The cardinal septum is short, and the counter is slightly longer and thicker than the adjacent septa. All major septa are thick at the base, join at their rhopaloid ends around the well-developed cardinal fossula, which invades the counterpart, being longer than the radius of the corallite. Pseudoalar fossulae are not markedly developed. Minor septa are absent from the corallite lumen, they are visible in the stereoplasm of the wall.

Discussion: According to the septal arrangement and the axial stereocolumn, the current species clearly belongs to the genus Zaphrentites . It is closely similar to Z. parallela (Carruthers, 1910) in the septal arrangement and more or less in the shape of the cardinal fossula, with the cardinal septum withdrawn in late stages. However, our specimens reach larger n:d ratios ( Fig. 12D ) in the last mature stage near the calice (26:8.6 vs. 20:5.6). Z. delanouei ( Milne-Edwards and Haime, 1851) and Z. crassus Hudson, 1944 are both larger and have more septa than the herein described species. It is quite similar to Z. parallela of Denayer and Hoşgör (2014) from the Lower Carboniferous of Turkey. It differs in the n:d ratio of the last mature stage (21:8.5) and in general counts more septa at the same diameter.

Figures

Fig. 11 A, B Zaphrentites cf. parallela (Carruthers,1910). A1–A3 Successive transverse sections in the specimen RAh (118), starting from the early immature stage with zaphrentoid arrangement of the septa in A1 to the last mature stage below the calice in A3. B1 External lateral view of the specimen RAh (109), showing strong longitudinal ribbing on the corallite wall. Positions of thin-sections indicated. B2–B4 Successive transverse sections represent the ontogenetic development, starting from the immature section in the apical part in B2 to the last mature section below the calice floor in B4. C Zaphrentites sp. C1 External view of the specimen RAh (84). C2–C4 Successive transverse sections; from the immature section in C2 to the last mature section below the calice floor in C4. Black dots indicate the positions of cardinal septum (below), counter septum (above) and the two alar septa

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

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

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. 12 Relation between number of major septa and coralla alar diameters for: A Lytvolasma paraaucta n. sp.,L aucta Fedorowski,1987, L. asymetrica Soshkina, 1925 described by Chwieduk (2013), L. canadense Fedorowski and Bamber, 2001 and the current studied L. cf. canadense Fedorowski and Bamber, 2001. B Monophyllum galalaensis n. sp. and M. parvum Fomichev, 1953. C Rotiphyllum exile de Groot, 1963. D Zaphrentites cf. parallela (Carruthers,1910) and Zaphrentites sp

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)