Nanopsis coquena Salas, Vannier, and Williams, 2007

Salas, María José & Vaccari, N. Emilio, 2012, New insights into the early diversification of the Ostracoda: Tremadocian ostracods from the Cordillera Oriental, Argentina, Acta Palaeontologica Polonica 57 (1), pp. 175-190 : 182-183

Nanopsis coquena Salas, Vannier, and Williams, 2007

Fig. 6 .

Material.— Over 100 specimens including the figured material CEGH−UNC 24015 , 24018–19 , 24021 , 24023 and JUY−P 045. The specimens we have examined range from 0.53 mm to 1.41 mm in length .

Remarks.—This species was described by Salas et al. (2007), the authors defined the species having only few specimens from the Floresta and Coquena formations. Here, new and abundant material from the Floresta Formation and from the Humacha Member of the Santa Rosita Formation provides additional morphological information which allows the recognition of the species with its intraspecific variations. The valves bear three well defined and short lobes that not reach the ventral half of the valves. L1 and L2 are in the anterodorsal part of valves. L1 is rounded, adjacent to anterior margin, and could reach the dorsal margin, L2 is shorter, and narrower, and is immediately behind L1. L3 is bigger than the other lobes, bulbous, and it generally reaches the dorsal margin. L4 is a very faint elevation, more visible in the valves than in the internal moulds ( Figs. 6A, C ). The main variation in the species is the development of the lobes, which are more or less visible on the surface of the valves. The most variable lobe is L4 which is very faint in some specimens, and mainly in the internal moulds. On the basis of the new material found, some specimens illustrated by Salas et al. (2007: figs. 4.1–4.4) should be removed from the species due to their too prominent and long lobes that reach the ventral half of the valve. Moreover, these specimens have a punctuated surface not observed in the rest of the material.

With respect to the other species of the genus, Nanopsis coquena differs from N. nanella ( Moberg and Segerberg, 1906) and N. pilloides ( Schallreuter, 1998) in that N. coquena is larger in size (L reaches the 1.41 mm) and mainly in the well−developed sulcus S3, which is not present in the other species.

Stratigraphic and geographic distribution.— Nanopsis coquena is known from the Floresta Formation (Tr2, Paltodus deltifer Biozone ) along the Road N° 9 (km 1,651.5 km), and from the Humacha Member, Santa Rosita Formation, in the middle part of the Humacha section (Tr3). Northwest Argentina.

Figures

Fig. 6. Late Tremadocian ostracod Nanopsis coquena Salas, Vannier, and Williams, 2007 from the Cordillera Oriental Argentina. A, B, D–F. Humacha Member, middle levels of the Humacha section. A. CEGH−UNC 24015, left valve in lateral view. B. CEGH−UNC 24018, left valve in lateral view. C. Iglesias collection, Floresta Formation, Abra de Santa Laura section; JUY−P 045, internal mould of right valve, lateral view. D. CEGH−UNC 24021, right valve in lateral view. E. CEGH−UNC 24019, left valve in lateral view. F. CEGH−UNC 24023, right valve in lateral view. Scale bars 100 µm.