Lytvolasma cf. canadense Fedorowski and Bamber,, 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 : 12

Lytvolasma cf. canadense Fedorowski and Bamber, 2001.

( Fig. 6C 1–C 3 , 12A ).

cf. 2001 Lytvolasma canadense Fedorowski and Bamber. —Text-Fig. 8, pl. 3, Fig. 2 , pl. 5, Fig. 5 .

Material: Only one worn specimen (RAh 66) with calice rims and a large part of the corallite not preserved, collected from the basal shales of the lower member of the Aheimer Formation. Two transverse sections are available.

Description: External characters: The preserved mature part of the corallite is 17 mm long. It does not show any furrows or ridges on the outer wall except for very delicate growth lines. The calice is not preserved, and also the apex and a large part of the immature ontogenetic stages are not preserved.

Internal characters: Only two transverse sections in the mature part of the corallite are available for study. An ontogenetically earliest section ( Fig. 6C 1–C 2 ) shows sub-radial arrangement of septa, with short cardinal septum and long counter septum with a rhopaloid axial end. The axial area is free of septa, only the swollen end of the counter septum invading the centre. A typical half aulos is developed in the counter quadrants. At this stage n:d is 26: 10 mm. Minor septa are underdeveloped. Biform morphology is developed. The last ephebic stage ( Fig. 6C 3 ), more or less at the calice floor, shows all septa withdrawn from the axis and the axial area becomes large. Only the counter septum is still prominently longer, and the cardinal septum is slightly shorter than the others. The n:d ratio is 26:12.8 mm. Minor septa are rudimentary. Cardinal fossula is slightly triangular, but open adaxially.

Discussion: The current species closely resembles Bradyphyllum counterseptatum described by Fedorowski (1987a). It differs from it in the n:d ratio in the ephebic stage; the current species is larger in dimensions than the former species. It also differs in the length of the counter septum; which is longer and thicker in the currently described species than the former. Lytvolasma canadense is distinguished from all other Lytvolasma species by its greater dimensions ( Fig. 12A ), the stronger elongation of its counter septum and in the underdevelopment of its minor septa. The shortening of the last major septa in all quadrants is not expressed herein. However, in the n:d ratio ( Fig. 12A ) and further morphological aspects our specimen seems to be identical to L. canadense (see Fedorowski and Bamber, 2001, Fig. 8c, d ) from the Guadalupian (Wordian) of Ellesmere Island (Sverdrup Basin, Canadian Arctic). Due to the fragmentary nature of our single Egyptian specimen and considerable geographic and stratigraphic differences we did not include it into the nominate species and retained determination as “cf ”.

Figures

Fig. 6 A Actinophrentis crassithecata n. sp.: (Holotype specimen RAh (57). A1 External view showing a thick walled, slightly curved corallite with septal furrows ornamenting the external wall. Position of thin-sections indicated. A2 Transverse thin-section near the non-preserved apical part, shows thick major septa meeting in the centre and adaxially thinning cardinal septum. A3 Transverse thin-section in the middle part of the corallite, shows major septa meeting in the centre and noticeable fossular breaks. A4 Last adult transverse thin section just below the calice shows septa withdrawn a little from the centre.A5 Details of the external wall of A3. B1, B2 External lateral views of the specimen RAh (11) showing a thick walled,slightly curved corallite with septal furrows and concentric growth lines on the external wall. C Lytvolasma cf. canadense Fedorowski and Bamber,2001, specimen RAh (66). C1, C2 Transverse thin-section in the middle mature part of the corallite, shows a short cardinal septum and a long counter septum with a rhopaloid axial end. C3 Transverse thin-section in the calice, shows a long counter septum. Scale bars: 2.5 mm, except A2–A5: 2 mm. 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. 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)

Fig. 5 Internal morphological characters of the non-dissepimented rugose corals referred to in the systematic descriptions, after Denayer and Hoşgör (2014). A Transverse section. B Longitudinal section

Fig. 8 A Lytvolasma paraaucta n. sp. A1 Lateral external view of the holotype specimen (RAh 54). Note that, calice is compressed due to compaction.A2 Transverse thin-section in the immature part, showing major septa with irregular zaphrentoid arrangement.A3 Transverse thin section in the early mature part of the corallite, showing radially arranged major septa with rhopaloid ends. A4 Laterally compressed section in the calice base,showing a deformed fossula. A5 Transverse thin-section in the compressed calice, with calcareous mud filling. B1 Lateral external view of the paratype specimen (RAh 19). B2–B5 Successive transverse thin-sections from the immature part near the apex (B2) to the last mature part in the calice (B5)