Discinisca fallens ( Wood, 1872 )

Dulai, A., 2013, Sporadic Miocene brachiopods in the Naturalis Biodiversity Center (Leiden, the Netherlands): Records from the Mediterranean, the North Sea, and the Atlantic Ocean, Fragmenta Palaeontologica Hungarica 30, pp. 15-51 : 27

Discinisca fallens ( Wood, 1872)

( Figs 15–24)

Material – Dingden (1 dorsal valve); Haamstede (246 dorsal valves: 132–135

m: 7; 132–144 m: 7; 138–141 m: 1; 141–144 m: 1; 144–147 m: 230); Winterswijk-

Miste (2 dorsal valves); Delden (1 dorsal valve); Cacela Velha (1 dorsal valve). Size (mm) –

Length 2.9 2.1 2.9 1.3 2.5 2.8 1.9 4.0 3.0

Width 2.5 1.9 2.4 1.2 2.2 2.5 1.8 3.3 2.7

Notes – Two Discinisca species are known from the Neogene of the North Sea Basin. At first, the discinide specimens of the Coralline Crag at Sutton ( Great Britain) were doubtfully regarded as possibly conspecific with recent Orbicula lamellosa by DAVIDSON (1852). However, later it was separated as a distinct species, D. fallens by WOOD (1872).

BOSQUET (1862) described Discina suessi from the Elsloo Conglomerate (Elsloo, the Netherlands). Later it was mentioned erroneously as Discina Nysti by DAVIDSON (1874) and THOMSON (1927). On the figures of the classical papers D. suessi has rectangular, slightly trapezoidal outline and cranioid-type internal structure ( BOSQUET 1862: figs 1–5; DAVIDSON 1874: Pl. 7, figs 4–5). Recently, RADWAŃSKA & RADWAŃSKI (2003) revised Bosquet’s discinide material, and described a new species, Discinisca elslooensis , as the species name suessi was preoccupied. D. elslooensis is medium-sized, quadrangular, thick-walled, and lowconical with subposterior-posterior apex and almost devoid of ornamentation ( RADWAŃSKA & RADWAŃSKI 2003).

The relatively numerous discinide brachiopods in NBC collection, derived from the southern part of the North Sea Basin and from the Atlantic locality of Cacela Velha are characterised by rounded, smooth dorsal valve and ornamented only by concentrical growth lines. All of these specimens can be attributed to D. fallens , originally described from the northern part of the North Sea Basin. The available dorsal valves are small-sized, more or less circular, thin-walled, conical with central-subcentral apex and well-visible growth lines ( Figs 15–24). Drilling predation on D. fallens specimens is very limited, especially as compared to Discradisca multiradiata from Amberre (Atlantic Ocean, France). In the Haamstede material 1 out of 7 specimens was drilled near to the apex in 132–144 m sample and 1 out of 230 specimens in 144–147 m sample (see Figs 16–18). This is the first known record of D. fallens from the Miocene of Portugal and the Miocene of the Atlantic Ocean.

Geochemical composition of Dutch Miocene Discinisca (Haamstede) was discussed by KOCSIS et al. (2012). See comments at the notes of Glottidia dumortieri .