Monophyllum Fomichev, 1953

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 : 16-18

Genus Monophyllum Fomichev, 1953 .

Type species: Monophyllum sokolovi Fomichev, 1953 .

M. sokolovi Fomichev, 1953 ;? 1953 M. parvum Fomichev 1953 ; M. cassum Fedorowski, 1987 .

Diagnosis: Non-dissepimented, small solitary corals, with major septa radially arranged, may withdraw a little from corallite axis in maturity; cardinal septum shortened from early maturity; counter septum permanently elongated to corallite axis; alar septa slightly elongated at least in some portion of growth; minor septa underdeveloped (after Fedorowski, 1987a, p. 67).

Remarks: In contrast to Hill (1956, 1981), de Groot (1963) and Weyer (1975) who listed Monophyllum Fomichev, 1953 as a synonym of Rotiphyllum Hudson, 1942 , Fedorowski (1987a) considered it as a separate genus. This view was followed by Kossovaya (1996, 2001), Ogar (2012) and Wang et al. (2017). Fedorowski (1987a) mentioned the following differences to Rotiphyllum and further similar antiphyllinid genera (see also Table 1 ):

• Monophyllum differs from Rotiphyllum by: (1) the strongly and permanently elongated counter septum reaching the corallite axis, even on the calice floor, where it may form an incipient columella, (2) shortening of the cardinal septum not only on the calice wall as in Rotiphyllum , but also on the calice floor, (3) the triangular shape of at least peripheral parts of the cardinal fossula at maturity.

• Monophyllum differs from Bradyphyllum by the permanently elongated counter septum that reaches the corallite axis and tends to form an incipient columella. Although Monophyllum develops a tendency to form an axial area free of septa, like most of the genera included in Antiphyllinae (Illina, 1970), its counter septum remains elongated, which is not the case in Bradyphyllum .

• Monophyllum differs from Actinophrentis Fomichev, 1953 by (1) the radial arrangement of septa in the mature portions of Monophyllum vs. the pinnate arrangement of the major septa lasting up to the calice floor in Actinophrentis and (2) the lacking tendency of Actinophrentis to form a free axial area.

Species described by Fomichev (1953) to be “ Stereolasma ” might belong to Rotiphyllum (in toto, see Hill, 1956; de Groot, 1963), to Monophyllum and/or other Antiphyllinidae ( Fedorowski, 1987a, p. 36, 68).

Geographic and stratigraphic range: Monophyllum is a long ranging but relatively rare genus. It is known from the Bashkirian of the Donets Basin ( Fomichev, 1953; Kossovaya, 1986, Fig. 7 ; Fedorowski, 2022, Fig. 2 : M. sokolovi Fomichev, 1953 , M. parvum Fomichev, 1953 ), the Moscovian of the same region ( Fomichev, 1953: original designation of the type species M. sokolovi ; Kossovaya, 1986, Fig. 7 ; Ogar, 2012) and the Moscovian of Novaya Zemlya (fide Fedorowski, 1981 and Wang et al., 2022). It is also known from the Pennsylvanian–Permian transition and the Wolfcampian (Asselian–middle Artinskian) of southwest Texas ( Fedorowski, 1987a: M. cassum Fedorowski, 1987 ). Kossovaya et al., (2001, Fig. 6 ) figured? Monophyllum sp. from the late Artinskian of the Urals and/or northern Timan Ridge (not further specified). Herein, we report the genus from the Kasimovian west of the Gulf of Suez, Egypt.

Figures

Fig. 7 Lytvolasma aheimerensis n. sp. A External view of the specimen RA (2), showing a straight corallite with partly eroded calice and non-preserved apical part, positions of thin-sections indicated.B–D Successive transverse thin-sections in the early preserved growth stages, shows very thick major septa joining together near the centre.The cardinal septum is deformed in D. E–G Successive thin-sections in the early mature stages show the formation of a stereozone with a free axial area,shortening of the cardinal septum with maturity and the longest counter septum with a rhopaloid end. H–I Two transverse thin-sections below the calice, deformed due to rejuvenation in H and lateral compaction in I. Scale bars: 2.5 mm, except A: 5 mm. Black dots indicate the positions of cardinal septum (below), counter septum (above) and the two alar septa

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. 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