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

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

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

Fig. 2G, H .

2019 Nudator angiportatus sp. nov.; Perrier et al. 2019: 44, pl. 14: 1–15. Holotype: A laterally compressed left valve (OUMNH 35267); Perrier et al. (2019: pl. 14: 5–8, 14, 15).

Type locality: Loc. 56 of Perrier et al. (2019), Long Mountain , Wales, UK .

Type horizon: Lower part of the Irfon Formation, 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 = 1.05, H = 0.85 ( ZPAL O.63/30) to L = 3.6, H = 2.6 ( ZPAL O.63/8, Fig. 2H ). Holotype: L = 2.70, H = 2.35 ( OUMNH 35267). L/H ratio and adductor muscle position for 19 specimens from two localities ( Fig. 4 ).

Description.—Valve large, bean-shaped in lateral outline. Greatest length is just above mid height; greatest height just in front of the adductorial sulcus at the site a small anterodorsal inflation of the carapce. Valve outline in lateral view is slightly concave dorsally, gently curved ventrally, posteriorly is evenly rounded, anteriorly above mid-height is more sharply rounded, and anteriorly has a weak indentation. Valve surfaces gently inflated overall, lacking distinct or discrete lobes. Adductorial sulcus narrow, occurs just in front of mid-length, originates just posteriorly of the small anterodorsal protuberance and curves forward from dorsal margin to just below mid-height ending with the adductor muscle spot. Anterior-anteroventral valve margin appears slightly concavely indented in lateral view in some specimens and has an apparent incisure (gape). 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 conjoined open valves but open valves in “butterfly position” are connected along dorsal margin. During ontogeny valve shape changes from sub-triangular to more rounded/ovoid.

Stratigraphic and geographic range.—Ludlow Series, Holy Cross Mountains, Poland. Also known from the Wenlock and 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.