Actinophrentis crassithecata, 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 : 9-11

publication ID	https://doi.org/ 10.1186/s13358-023-00296-0
DOI	https://doi.org/10.5281/zenodo.12783837
persistent identifier	https://treatment.plazi.org/id/49386916-7F11-FFF2-FC91-FC53FB0DFE48
treatment provided by	Felipe
scientific name	Actinophrentis crassithecata
status	sp. nov.

Treatment

Actinophrentis crassithecata n. sp.

( Fig. 6A View Fig 1–A View Fig 5 View Fig , B 1–B View Fig 2 View Fig )

Derivation of the name: From the Latin crassus—means thick, theca—F cover—after the great thickness of the external wall.

Holotype: Specimen RAh 57 , illustrated in Fig. 6A View Fig 1–A View Fig 4 View Fig . Three transverse thin-sections are available.

Material: In addition to the holotype, two moderately to badly preserved corallites (RAh 11 and RAh 42) are paratypes, with 11 transverse thin-sections. Although looking good preserved in their external form, keeping a good preserved outer epitheca with septal furrows and concentric growth lines ( Fig. 6B View Fig 1 View Fig , B 2 View Fig ), serial thin-sections of the specimens (RAh11, 42) are not suitable for illustrations as they suffer from either compaction or ferrugination (e.g., Fig. 4E View Fig ), The proximal ends of the corallites are largely eroded. They are collected from the basal shales of the lower member of the Aheimer Formation.

Type locality: Eastern cliffs of the Northern Galala plateau (Lat. 29° 28 ′ 21 ″ N and Long. 32° 27 ′ 38 ″ E), northern Eastern Desert, western side of the Gulf of Suez, Egypt GoogleMaps .

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

Diagnosis: Actinophrentis with thick external wall (about 1.5 mm thick), having maximum n:d ratio at calice floor 24:11. Major septa are pinnately arranged. Cardinal septum shortened with maturity. Counter septum elongated from the immature stage up to calice floor.

Description: External characters: Corallites only faintly conical (see minimal increasing n:d ratios below) and slightly curved ( Fig. 6A View Fig 1, B1–B View Fig 2 View Fig ). The preserved parts are 2–2.5 cm long. Calices are deep. If preserved, they are compressed due to compaction. Apexes are not preserved. The thick external wall (1.5 mm-thick) bears distinct furrows of major and minor septa. The latter could only be detected inside the calyx ( Fig. 6A View Fig 1 View Fig ).

Internal characters (transverse sections): the ontogenetically earliest preserved part has a n:d ratio of 22: 7 mm ( Fig. 6A View Fig 2 View Fig ). Major septa are pinnately arranged. Cardinal fossula is distinguishable. Alar fossulae are also distinct, they are marked by the underdeveloped last pair of major septa in the counter quadrants. All septa meet in the corallite axis. The cardinal septum is thinner than the other major septa, whereas the counter is slightly thicker. External wall about 1.5 mm thick and internally enforced by steroplasmatic layer in the most external septal loculi. The mature morphology seen in the next transverse section ( Fig. 6A View Fig 3 View Fig ) is characterised by a pinnate arrangement of long major septa with n:d ratio of 24:8. Major septa are conspicuously acutely thickened in their peripheries and wedge-like rooted in the thick external wall ( Fig. 6A View Fig 5 View Fig ); they are also slightly thickened to contiguity in their inner ends. Cardinal septum shortens, whereas the counter is the longest. Pericardinal septa are as short as the cardinal. The cardinal fossula extends to the corallite axis, where it moderately widens. Alar septa are long and meet with the axial end of the long counter septum in the axis. The alar fossulae are still well-marked. Minor septa are absent. Peripheral interseptal loculi are filled by stereoplasma, thus apparently increasing the prominent, about 1.8 mm thick external wall ( Fig. 6A View Fig 5 View Fig ). One row of axially updomed tabulae well-developed in peripheral interseptal loculi of right cardinal and counter quadrant. Opposed, strongly horseshoe-arched, isolated and small peripheral, convex tabulae (i.e., inclined towards the external wall) are mostly confined to the left cardinal and counter quadrants. The last mature section below the calice ( Fig. 6A View Fig 4 View Fig ) has a n:d ratio of 24:11. Major septa are withdrawn from the corallite axis, leaving a free axial area, invaded by the distinctly elongated counter septum. Cardinal septum strongly shortened. Minor septa are absent. No tabulae are visible except for one in right alar fossula. Like in previous cross section ( Fig. 6A View Fig 3 View Fig ) septa are wedge-like thickened in external wall, which is 1.9 mm thick.

Discussion: Actinophrentis columnare Fedorowski, 1987 is of similar size with n:d ratios ranging from 20: 8 in the holotype to 24: 10 in the largest paratype. However, in contrast, it has a remarkable thick counter septum at maturity forming a weak columella in the calice. In the studied species the counter septum thins with maturity and/or has the same thickness as the other major septa or is only slightly thicker. Its wall is conspicuously thicker than the wall of the A. columnare . The current species differs from the smaller Actinophrentis bonespringense Fedorowski, 1987 in the wall thickness and n:d ratios. The Actinophrentis sp. ( Fedorowski, 2004), previously named Zaphrentites paralleloides de Groot, 1963 differs in the radial arrangement of the major septa that extends from the earliest growth stages up to the calice, vs. the pinnate arrangement in the current species. Diameter and the number of septa in the Spanish species are much smaller. In addition, the type species of the genus, A. donetziana Fomichev, 1953 appears to be smaller with a higher number of septa (n:d = 23:8.5); its wall is conspicuously thinner (based on fig. 203, 7a, b in Hill, 1981).