Lytvolasma Soshkina 1925

Genus Lytvolasma Soshkina, 1925. Type species: Lytvolasma asymetrica Soshkina, 1925 [sic!]. Diagnosis: Non dissepimented small solitary corals; cardinal fossula deep, key-hole shaped, often bordered by half aulos in counter quadrants; cardinal septum shortened late in ontogeny; counter septum slightly elongated; major septa semi-radial in arrangement; minor septa very short; microstructure of septa trabecular (Fedorowski, 1987a). Remarks: Lytvolasma is a complex genus with unclear relations to several other taxa, as extensively discussed by Fedorowski (1987a). He modified the diagnosis by Hill (1981) who questioned the validity of Lytvolasma and considered it as a possible junior synonym of Bradyphyllum Grabau, 1928. However, due to morphological differences Fedorowski (1987a) considered both genera as valid and did not include the presence of long, slightly curved, thickened septa that are laterally contiguous over much of their length and almost reach the axis from Hill’s diagnosis. However, opposed to Fedorowksi, these characteristics were confirmed by Chwieduk (2013, tab. 3). According to Fedorowski (1987a), intimate relations of the genus exist with further Antiphyllinae, as Lytvolasma specimens were attributed by authors in part to Actinophrentis Ivanovski, 1967, as well as to species of Allotropiophyllum Grabau, 1928 and Bradyphyllum. In addition, the type species of the hapsiphyllinid Parasterophrentis, P. virgata Fomichev, 1953 has to be transferred to Lytvolasma. Opposed, Lytvolasma (?) cf. L. geinitzi (Toula, 1875) described by Flügel (1973) from the Upper Permian of eastern Greenland was included in Tachylasma rhizoides Soshkina, 1925 by Fedorowski (1982). He also excluded Lytvolasma from Northeast China figured by Guo (1980), but opposed, Fedorowski and Bamber (2001) did not rule out the possibility that some of Guo’s specimens might be included. Lytvolasma described from Tibet (Wang and Liu, 1982; Wu, 1975) and Xingjiang (Wang and Yu, 1986) were included in Euryphyllum (Fedorowski, 1982). Similarities to further genera were extensively discussed by Fedorowksi (1987a). According to the author, Lytvolasma Soshkina, 1925 shows some similarities to Allotropiophyllum Grabau, 1928. It is distinguished from the latter by the elongation of counter septum and the alar septa in the early growth stage, a slightly but permanently elongated counter septum at maturity, shortening of the cardinal septum late in ontogeny, and the calice floor deeper in the cardinal quadrants. Based on the holotype of the type species of Allotropiochisma Fedorowski, 1982, Allotropiochisma longiseptata (Flügel, 1973), this genus is sufficiently different from Lytvolasma in having a narrow cardinal fossula, lacking an elongated counter septum, "biform reduction" of minor septa, and biform peripheral–most tabularium. In addition, Euryphyllum Hill, 1938 is similar. In fact, Lytvolasma sp. No. 2 described from the Lower Permian of the Northern Urals (Dobrolyubova, 1936) and at least some specimens described as Lytvolasma by Wu (1975) and Lin (1983) from the Lower Permian of Tibet might belong to that genus, as well as some specimens described by Guo (1980) from Northeast China (Fedorowski and Bamber, 2001). Geographic and stratigraphic range: Lytvolasma is a spatiotemporally widespread genus. It is known from the Bashkirian of the Donets Basin and the Southern Urals/ Bashkirian Mountains (Kossovaya, 1986), but was not listed from the Bashkirian of the Donets Basin by Fedorowski (2022). According to Fedorowski (1987a), it occurs there from Kasimovian to Gzhelian (C 2 3 –C 3 3). The genus is known from the Kasimovian of Egypt (Kora and Mansour, 1991 and this paper) and Donets Basin, from the Pennsylvanian–Permian transition of the Glass Mountains, western Texas (Uddenites -bearing shale member of Gaptank Formation, Fedorowski, 1987a), from the upper Artinskian and lowermost Kungirian (lower Saranian) of the Central Urals (Kossovaya et al., 2001; Kossovaya, 2007, Fig. 6; Shoshkina, 1925), the Sakmarian of Spitsbergen (Chwieduk, 2013) and from the Wordian (Middle Guadalupian) of the Canadian Arctic Archipelago (Fedorowski and Bamber, 2001). The existence of Lytvolasma in Tibet (Wu, 1975) was rejected by Fedorowski (1987a), but Fang and Fan (1994; not seen) again reported a “ Lytvolasma fauna” in SW Yunnan (Baoshan–Pengchong). To us, the presence of Lytvolasma in Tibet and the Baoshan Block, southwestern Yunnan, i.e., in terranes originally bordering the northern margin of Gondwana, remains unsure and needs revaluation.

Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.