Nudator inflatus Perrier, Siveter, Williams, and Palmer, 2019

Legiot, Nicolas, 2019, Silurian myodocope ostracods from Poland, Acta Palaeontologica Polonica 64 (2), pp. 379-397 : 387

Nudator inflatus Perrier, Siveter, Williams, and Palmer, 2019

Fig. 2I, J .

2019 Nudator inflatus sp. nov.; Perrier et al. 2019: 43, pl. 13: 1–14.

Holotype: A laterally compressed right valve ( OUMNH 35000 ); Perrier et al. (2019: pl. 13: 4, 5).

Type locality: Radnorshire (loc. 10 of Perrier et al. 2019), Powys, Wales, UK.

Type horizon: “ nilssoni-scanicus blue Mudstones” of Kirk (1947), Cucullograptus (Lobograptus) scanicus Biozone, Gorstian Stage, Ludlow Series.

Material.—Tens of valves, from two localities (Widełki and Niestachów), Holy Cross Mountains, Poland; Ludlow Series, Silurian.

Measurements (in mm).—Size range: L = 2.9, H = 2 ( ZPAL O.63/9, Fig. 2I, J ) to L = 3.85, H = 2.35 ( ZPAL O.63/29). Holotype: L = 2.00/H = 1.70 ( OUMNH 35000). L/H ratio and adductor muscle position for two specimens from two localities ( Fig. 4 ).

Description.—Valve large, bean-shaped in lateral outline. Greatest length is just above mid height; greatest height is at the adductorial sulcus. Valve outline in lateral view is almost straight dorsally, gently curved ventrally, posteriorly and anteriorly is evenly rounded. Valve surfaces gently inflated overall, lacking distinct or discrete lobes. Anterior valve margin in some cases has a faint indentation. Adductorial sulcus narrow, occurs just in front of mid-length, extends almost vertically from dorsal margin to just below mid-height ending with the adductor muscle spot. Prominent postadductorial tubercle variable in shape and size, diameter 15–25% of valve length. Adductorial sulcus generally curves around the front of the tubercle, in some specimens the sulcus appears to bifurcate and border both sides of tubercle. A simple elliptical adductor muscle scar occurs at the slightly widened ventral extremity of the sulcus. Valves smooth. No evidence for presence of hinge structure, but open valves in “butterfly position” are consistently to be connected along dorsal margin.

Remarks.— Nudator inflatus is distinguished from all other Nudator species by the presence of its large postadductorial node.

Stratigraphic and geographic range.—Ludlow Series, Holy Cross Mountains, Poland. Also known from the Gorstian Stage, Ludlow Series of England and Wales ( Perrier et al. 2019).

Figures

Fig. 2. Selected Silurian myodocope species, Holy Cross Mountains, Poland; Ludlow Series, Silurian. A, B. Bolbozoe anomala Barrande, 1872. A. ZPAL O.63/1, incomplete left valve. B. ZPAL O.63/2, juvenile right valve. C. Bolbozoe psittaca Perrier, Siveter, Williams, and Palmer, 2019, ZPAL O.63/3, left valve. D, E. Parabolbozoe bohemica (Barrande, 1872). D. ZPAL O.63/4, juvenile left valve. E. ZPAL O.63/5, right valve. F. Richteria migrans (Barrande, 1872), ZPAL O.63/6, left valve. G, H. Nudator angiportatus Perrier, Siveter, Williams, and Palmer, 2019. G. ZPAL O.63/7, juvenile left valve. H. ZPAL O.63/8, left valve. I, J. Nudator inflatus Perrier, Siveter, Williams, and Palmer, 2019. I. ZPAL O.63/9, right valve showing post-mortem diagenetic structures. J. ZPAL O.63/9, right valve. K. Silurocypridina retroreticulata Perrier, Vannier, and Siveter, 2011, ZPAL O.63/10, incomplete right valve. L. Silurocypridina calva Perrier, Vannier, and Siveter, 2011, ZPAL O.63/11, right valve. M. Cypridinid?, ZPAL O.63/12, right valve. All light photographs in lateral view. A–H, J, M, silicone casts of external moulds; I, K, L, internal moulds. Scale bars 1 mm, except M 2 mm.

Fig. 4. Valve length/height plot (A) and position of the adductor muscle scar (A/B, where A and B are the distance between the muscle scar and the posterior end of the valve and the ventral margin, respectively) against length/height (B) of complete specimens of entomozoid species from the Holy Cross Mountains, Poland; Ludlow Series, Silurian.