Margarogyra hirsuta, 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 : 410-412

Margarogyra hirsuta sp. nov.

Fig. 3B–D.

Etymology: From Latin hirsuta , hairy, rough; from the rough surface of the septa.

Type series: Holotype: GBA 2009 /019/9, with thin sections; paratypes: 2009/019/3, 8–10, with thin sections.

Type locality: Austria, Northern Calcareous Alps , southern Dachstein Plateau, site ca. 50 m north−west of Feisterscharte .

Type horizon: Norian, Lacian 1, Epigondolella quadrata Conodont Zone ; light−grey organodetritic limestones.

Diagnosis.—Coryphylliid with circumoral budding. Central corallite large, with up to 90 septa, encircled by smaller corallites with up to 40 septa. Septa thin adaxially, moderately enlarged peripherally; the S1–S2 septa distally thick, with distal border rounded.

Material.— The type series (see above) and fragments in detritic limestone GBA 2009 /019/4, 5, and 17, all with thin sections .

Measurements (in mm):

d s

D

GBA (colony) central other central other sd/5

calice calices calice calices

90 11–13 2009/01

60–80 ca. 40 20 38, 40 11–12 9/9

6 15

Description.—Colonies fungiform, with flat upper surface and a short, monocalicular trunk (GBA 2009/019/17). Circumoral budding with lamellar linkages; central corallite (or 2–3 corallites) large, other corallites far smaller, unequal in diameter, more or less parallelling the colony margin. New individuals initiated by division of calices, or through interruption of septa of adult corallites. Central corallite oval, multiseptal (GBA 2009/ 019/9); other corallites regularly radial, with a small number of septa. Axial pits circular and small. The distance between the central and the nearest corallites 12 to 23 mm (GBA 2009/019/3); the distance between the corallites outside the central one is septal border (B 4); traces of septal microstructure in transverse section (B 5). C. GBA 2009/019/ 3 f. Transverse section of colony with numerous thin−walled dissepiments in the interseptal space. D. GBA 2009/019/10 b. Fragment of calice in transverse section near to the axial part showing irregular granulation of septal sides. E. Distichophyllia sp. ; GBA 2009/019/7. Polished section of a damaged specimen. F. Cuifia marmorea ( Frech,1890) ; GBA 2009/019/4e. Fragment of corallum in transverse section showing septa strongly differentiated in size orders. G. Volzeia sp. ; GBA 2009/019/6 a and 6 e, respectively. Phaceloid corallum in transverse (G 1) and longitudinal (G 2) sections. Note thin, but resistant wall and abundant dissepiments.

doi:10.4202/app.2009.0092

from 10 to15 mm. Septal apparatus composed of septa from two to four size orders: (i) in large corallites, the S1septa are thick (up to 1 mm) and approaching the axis, the S2 septa thinner adaxially and shorter than the S1septa, the S3 septa very thin and short, the S4 septa extremely thin (50–75 µm), low, and appearing irregularly; (ii) in small, regular corallites, only thick and long S1 septa and short S2 septa are observed; (iii) in calices at the colony rim, the S4 septa are developed in some systems. The S3 septa and S4 septa are zigzag and very thin in comparison with the S1 septa. Distally, the S1–S2 septa, subequal in height, have thick, rounded margins; the S3 septa and S4 septa are of a conspicuously smaller height. The adaxial part of the septa is thin, zigzag, and covered with sharp, rather rare granulations; more peripherally the blades become thick and their faces are covered with densely crowded, uniform, sharp granules (5–6 per 1 mm in transverse section). Endotheca built of small vesiculae.

Microstructure. The thinnest parts of the S3 septa and S4 septa show well individualised and thin fibre portions diverging from the septal plane. Their nature, either thin−trabecular or only fascicular, could not be recognised, but such an arrangement closely resembles that observed in some margarophylliid septa where the lateral offsets of thin trabeculae diverge from the midseptal plane. The diverging elements of 50–75 µm are thinner than those in margarophylliid septa. The original structure of the fibre portions has not been examined due to recrystallisation; however, in the related Noriphyllia anatoliensis , a relatively well preserved skeleton ( Roniewicz and Stanley 2009; Fig. 3A–C) shows fascicular fibre portions, some with a faintly marked axis of fibre orientation.

Stratigraphic and geographic range.—As for the type specimens.