Lytvolasma canadense Fedorowski and Bamber 2001

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 The last ephebic stage (Fig. 6C 3), more or less at the calice floor, shows all septa withdrawn from the axis and the axial area becomes large.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 ”.

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.