Roemerella, Hall and Clarke, 1890

Baliński, Andrzej, 2006, Brachiopods and their response to the Early-Middle Frasnian biogeochemical perturbations on the South Polish carbonate shelf, Acta Palaeontologica Polonica 51 (4), pp. 647-678 : 653-654

Roemerella ? sp.

Fig. 5 .

Material.— Thirty four strongly flattened and crushed specimens from Kostomłoty II (= Małe Górki) and one specimen from Kostomłoty V (= Kostomłoty Mogiłki) .

Remarks.—This species has been included in this report despite its occurrence in a slightly distant locality (ca. 10 km NW of Wietrznia) because of its faunistic importance. It was revealed in the late Givetian–early Frasnian boundary interval represented by middle Szydłówek Beds which are characterised by interlayering of marly shales and marly limestones (e.g., Satenaer and Racki 1992; Racki at al. 2004). These sediments represent deeper basinal setting than that at Wietrznia I. The only articulated brachiopod revealed in this soft−bottom environment of the interval is large−shelled rhynchonelloid Phlogoiderhynchus polonicus ( Roemer, 1866) (see description below; see also Biernat and Szulczewski 1975). It seems that these shells were frequently used as the only firm attachment site for Roemerella ? sp. Out of 89 specimens of P. polonicus revealed at Kostomłoty II during the present study, 13 (i.e., 15%) bear Roemerella ? sp. attached. Number of attached specimens on one shell of P. polonicus varies from 1 to 12 ( Fig. 5 ).

All studied specimens are strongly flattened and crushed as a result of compaction of the marly shales in which the species occurs. The largest specimen, which preservation allows measurement, attains 9.7 mm in diameter. In most cases only dorsal valve is visible because ventral one is concealed underneath resting on the surface of the host shell. The surface of the dorsal valve is ornamented by dense microscopic growth lines and very dense radial striae (24–40 per 1 mm; Fig. 5C ). Externally, the studied specimens are like Roemerella but lack of details on the interior of the ventral valve makes the generic identification somewhat tentative.

Occurrence.—The species is quite common, occurring as epifauna on the shells of Phlogoiderhynchus polonicus ( Roemer, 1866) from middle part of the Szydłówek Beds of Kostomłoty II quarry, and, much less frequently, in the same interval that crops out at Kostomłoty V quarry (both a few kilometres NNW of Kielce). This is the first record of the genus in Poland.

Figures

Fig. 5. Discinoid Roemerella? sp. from middle Szydłówek Beds, Kostomłoty II. A. ZPAL Bp 60/27−10, nine specimens adhered to large shell of Phlogoiderhynchus polonicus (Roemer,1866). B. ZPAL Bp 60/27−9, strongly flattened speci− men adhered in the sulcus of a shell of Phlogoi− derhynchus polonicus. C. ZPAL Bp 60/27−6, enlargement of flattened and crushed specimen showing details of surface ornamentation.