Hydrasmilia laciana, Roniewicz, 2011

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 : 424-425

Hydrasmilia laciana sp. nov.

Fig. 6A.

Etymology: From the name of the substage Lacian.

Holotype: A fragment of phaceloid corallum GBA 2009 /019/28.

Type locality: Austria, Northern Calcareous Alps, southern Dachstein Plateau, north−east of Feisterscharte.

Type horizon: Norian, Lacian 3, massive limestone above horizon with the Epigondolella triangulari s and Norigondolella navicula assemblage.

Diagnosis.— Hydrasmilia with corallites of ca. 15 mm in diameter and more than 100 septa differentiated into four size orders.

Material.— Dachstein Plateau: the holotype specimen represents a 70×100× 50 mm fragment of a very large corallum. Gosaukamm: NHMW, field nos. 1991/5, 1991/16, 1991/21 from the Lacian; NHMW 1991 /37 from the Alaunian; all with thin sections .

Measurements (in mm): Description.—Corallum phaceloid. Corallites parallel, densely crowded, with rhythmically expanding and contracting diameters, in contact where diameters are enlarged. Axial fossa very narrow. Septal apparatus composed of numerous thin septa, zigzag adaxially, differentiated into four size orders: the S1 septa reaching the axial fossa, the S2 septa slightly shorter than the former, the S3 septa ca. four−fifths the length of the S1 septa, the S4 septa developed in the majority of systems, variable in length up to one−third that of the S1 septa. Septal sides with abundant, small and obtuse granules. Internal borders of the longest septa can produce a parietal columella. Endotheca dense, built of low, horizontally expanding dissepiments axially, and vesicular peripherally. Wall originally thin, pellicular, secondarily slightly thickened from the internal side by a sclerenchymal deposit. Monocentric subcircular and oval corallites are typical, but prolonged detachment of the corallites after budding produced clusters of two to three and even four individuals. Increase by intracalicular budding gave subequivalent and unequivalent corallites (ratio of new to adult corallite diameters is about 1:6). In some corallites creation of a new centre took place by an interruption of two to three septa. In others, new corallites resulted through simple elongation of the adult and separation of an elongated part. The corallites became isolated from each other by a thin dividing wall and detached in developing deep and narrow invaginations of the external wall. Division took place after formation of a wall.

Remarks.—Three species were described from Hydra Island, Greece ( Turnšek and Senowbari−Daryan 1994): H. rhythmica , H. fossulata , and H. ornamenta , differing slightly in number of septa and ornamentation, and in diameters. In corallite dimensions, the Alpine form is closest to H. fossulata , but it differs from all of them in a much lower density of septa ( H. fossulata : 7–8 in 2 mm, H. ornamenta : 11–12 in 2 mm).

Three specimens from the Gosaukamm were collected by Martin Schauer in the 1980s: two close to the Lacian exposures in the Armkar, and one specimen from the Alaunian exposure in the Oberes Armkar (locality details after Schauer in Roniewicz 1996: fig. 1).

Stratigraphic and geographic range.— Austria: Northern Calcareous Alps, Dachstein Plateau, north of Feisterscharte, massive ”reef” facies of the Lacian 3, above the conodont−bearing horizon with the association of Epigondolella triangularis and

Norigondolella navicula ; Gosaukamm Armkar, Lacian, and Oberes Armkar, Alaunian.