Thamnomargarosmilia Melnikova, 1996

Roniewicz, Ewa, 2011, Early Norian (Triassic) corals from the Northern Calcareous Alps, Austria, and the intra-Norian faunal turnover, Acta Palaeontologica Polonica 56 (2), pp. 401-428 : 416

Genus Thamnomargarosmilia Melnikova, 1996

Type species: Thamnomargarosmilia prima Melnikova, 1996 , Rhaetian, SE Pamirs, Tajikistan .

Thamnomargarosmilia aff. prima Melnikova, 1996 Fig. 5F .

Material.— GBA 1995/2/1 /2, a fragment of corallum of. T. aff. prima in organodetrital limestone, with thin sections .

Measurements (in mm): Description.—Corallum phaceloid. Corallites circular in section with small, circular and empty axial pit. Septa uniform in thickness, differentiated into four size orders: the S2 septa slightly shorter than the S1 septa, the S3 septa attaining ca. three−quarters the length of the S1 septa, the S4 septa variable in length. Dissepiments small and homogeneous. Epithecal wall very thin, pellicular, mostly damaged. Increase through intracalicular budding, with the centre of a new corallite initiated as an interruption of some two to three septa of the adult. Bi− and tri−centric states of corallites are observed with temporary lamellar connections between the centres. The new corallite diverge from the parent at nearly right angles.

Remarks.—The Alpine coral has smaller corallite diameters and more numerous septa than the example from the Pamirs T. prima Melnikova, 1996 ( Melnikova 1996: 12, pl. 2: 1). The Pamirian form, represented by the holotype only, shows a bushy morphology composed of phaceloid−thamnasterioid embranchments.

In addition to the fragmentary corallum of T. aff. T. prima , the sample contains fragments of solitary Cuifia marmorea (see above) and a solitary coral described below as “solitary dwarfish coral gen. indet.”

Stratigraphic and geographic range.— Austria: Northern Calcareous Alps, Dachstein Plateau, north of Feisterscharte, lower Norian, Epigondolella quadrata Conodont Zone. The Pamir species comes from the upper Carnian–lower Norian, Shaimak Svite, SE Pamirs, Djilgakochusu Valley, Tajikistan.

Figures

Fig. 5. Margarosmiliid corals from vicinity of Feisterscharte, Austria, early Norian, Triassic. A–C. Ceriostella aff. variabilis Roniewicz and Stanley, 1998. A. GBA 2009/019/20; a colony in polished section. B. GBA 2009/019/22; transverse thin sections (B1, B2), note cerioid colony and a lack of columella; longitudinal section (B3) showing mode of growth of corallites at the periphery of lamellar colony. C. GBA 2009/019/23a; calice in longitudinal/oblique section showing rare granules on the septal side and internal border micromorphology (at the middle). D. Magarosmilia nova Turnšek, 1991; GBA 2009/019/4 i; transverse section. E. Margarophyllia cf. capitata (Münster, 1841); GBA 2009/019/2c; transverse section. F. Thamnomargarosmilia aff. prima Melnikova, 1996; GBA 1995/2/1/2f, c; transverse sections showing budding with lamellar linkages between centres (F1), and a typical circular shape of adult corallite (F2) with a new one growing laterally. G, H. Margarosmilia adhios sp. nov. G. GBA 2009/019/18a; a fragment of transverse section (G1) of a corallite with traces of microstructure; longitudinal section (G2) of corallite showing small dissepiments. H. GBA 2009/019/19a, c; transverse section of phaceloid corallum (H1); a section of the corallite at a preliminary stage of sub−symmetric division (H2).