Richteria migrans ( Barrande, 1872 )

Legiot, Nicolas, 2019, Silurian myodocope ostracods from Poland, Acta Palaeontologica Polonica 64 (2), pp. 379-397 : 385-387

Richteria migrans ( Barrande, 1872)

Fig. 2F .

1872 Entomis migrans Barr. ; Barrande 1872: 514, pl. 24: 10–14, pl. 27: 22.

1873 Entomis migrans Barr., 1872 ; Jones 1873: 416.

1896 Entomis migratoria n. sp.; Gürich 1896: 374.

1899 Entomis migrans Barr. ; Canavari 1899: 151.

1900 Entomis migrans Barr. ; Canavari 1900: 193, pl. 25: 1, 2.

1900 Entomis Lamarmorai n. f.; Canavari 1900: 195, pl. 25: 3–5.

1900 Entomis n. f.?; Canavari 1900: 196, pl. 25: 6.

1900 Entomis Meneghinii n. f.; Canavari 1900: 196, pl. 25: 7–11.

1934 Entomis (Richteria) migrans Barr. ; Kegel 1934: 413.

1934 Entomis migrans Barrande ; Bassler and Kellett 1934: 304 (pars).

1936 Entomis (Richteria) migrans Barrande, 1872 ; Bouček 1936: 57, pl. 6: 5, 6; text-fig. 2a, 2b.

1937 Entomis (Richteria) migrans Barrande ; Chaubet 1937: 186, pl. 4: 8a–c.

1951 Entomozoe (Richteria) migrans (Barrande) ; Přibyl 1951: 11, pl. 1: 4.

1952 Entomozoe migrans Barrande, 1872 ; Kupfahl 1952: 178.

1958 Entomozoe (Richteria) migrans (Barrande) ; Pokorný 1958: 311, text-fig. 1032.

1961 Entomozoe meneghinii Canavari ; Sylvester-Bradley 1961: 389, text-fig. 312.2g –j.

1961 Richteria lamarmorai Canavari ; Sylvester-Bradley 1961: 390, text-fig. 313.1a–e.

1984 “ Entomis ” migrans Barrande ; Siveter 1984: 78, pl. 2: 12, 13, text-fig. 3.

1988 Richteria migrans ( Barrande, 1872) ; Přibyl 1988:113, text-fig. 5.1.

1990 “ Entomis ” migrans ; Siveter and Vannier 1990: 64, text-fig. 23.

1995 “ Entomis ” aff. lamarmorai Canavari, 1900 ; Kříž and Bogolepova 1995: 580, pl. 70: 12.

2000 E. migrans Barrande, 1872 ; Groos-Uffenorde et al. 2000: text-fig. 2.

2003 Richteria migrans taimyrica Abushik , subsp. nov.; Abushik et al. 2003: 122, pl. 27: 1, 2.

2007 Richteria migrans ( Barrande, 1872) ; Perrier et al. 2007: 156, text-figs. 6–10.

2009 “ Entomis ” migrans Barrande, 1872 ; Siveter 2009: pl. 9: 14.

2009 Richteria migrans ( Barrande, 1872) ; Gnoli et al. 2009: pl. 1: 1–11.

2012 Richteria migrans ( Barrande, 1872) ; Perrier 2012: text-fig. 7G, H.

2013 Richteria migrans ; Perrier and Siveter 2013: text-fig. 22.6D.

2014a Richteria migrans ( Barrande, 1872) ; Perrier et al. 2014a: 56, pl. 1: A–N., text-figs. 2, 3.

2019 Richteria migrans ( Barrande, 1872) ; Perrier et al. 2019: pl. 12: 1–3, 11, 12.

Lectotype: An incomplete right valve; on slab NM-L 22944; subsequently designated by Přibyl (1951: 111); figured by Barrande (1872: pl. 24: 12–14); Bouček (1936: text-fig. 2a); Perrier et al. (2007: text-fig. 6a, b).

Type locality: Former Dvorce quarry (today Podolí swimming pool), Podolí district of Prague, Czech Republic.

Type horizon: Kopanina Formation, 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 = 1.4, H = 1.1 ( ZPAL O.63/27) to L = 3.05, H = 2 ( ZPAL O.63/28). Lectotype: L = 2.25, H = 1.50 ( NM-L 22944). L/H ratio and adductor muscle position for seven specimens from two localities

Fig. 4 ).

Description.—Valve large, bean-shaped in lateral outline. Greatest length is slightly above mid height; greatest height is at the adductorial sulcus. Dorsal margin shorter than valve length. Preadductorial and postadductorial areas very slightly curved dorsally; ventral, anterior and posterior margins convex. Right valve slightly larger and overlaps left valve along entire free margin. Contact list in left valve is narrow, ornamented by very fine striation. Anterior valve margin shows a faint notch in some large specimens. Adductorial sulcus long, deep, crescent shaped, extends twothirds of valve height from in front of mid length near dorsal margin to below the preadductorial node. A simple elliptical adductor muscle scar is present at the slightly widened ventral extremity of the sulcus. Dorsal part of sulcus is deeper and narrower, ending at a small “bridge” (height about 50 μm) connecting preadductorial and postadductorial areas. Preadductorial node is generally unornamented but can be weakly ribbed, and is less developed in some specimens. External valve surface has up to 25 longitudinal ribs, including in some specimens short, intercalated and bifurcated ribs. The alignment of ribs is not disturbed by the adductorial sulcus. Ribs merge posteriorly, converge on a triangular smooth area anteriorly and curve slightly away from the valve margin ventrally. Some specimens show what seems to be very weak secondary reticulate ornament between the ribs. No evidence for presence of hinge structure; conjoined open valves are consistently connected along dorsal margin.

Remarks.—From its description and occurrence Entomis migratoria Gürich, 1896 (nomen nudum), is likely to be conspecific with Richteria migrans .

Stratigraphic and geographic range.—Ludlow Series, Holy Cross Mountains, Poland. Also known from the upper part of the Ludlow Series in the Czech Republic, France, Sardinia, Poland, Central Asia, Arctic Russia, England, Wales, and possibly Germany and Sweden (see Perrier et al. 2007, 2014a, 2019).

Length/height

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

Type species: Nudator inflatus Perrier, Siveter, Williams, and Palmer, 2019 . Ludlow Series, Silurian, Powys, Wales, UK.

Species included: Type species and Nudator angiportatus Perrier, Siveter, Williams, and Palmer, 2019 , Nudator artumatus Perrier , Sivet- er, Williams, and Palmer, 2019, N. elegantulus sp. nov. and Nudator sp. nov. A of Perrier et al. 2019.

Emended diagnosis.— Entomozoidae with bean-shaped to ovoid lateral outline, dorsal margin slightly rounded. Adductorial sulcus narrow, well developed, extending up to 3/4 of valve height. Prominent postadductorial node present in type species only. Faint notch in anterior valve margin. Valve smooth or bearing minute ornament (modified after Perrier et al. 2019).

Remarks.— Nudator differs from other entomozoid genera in having unornamented or very faintly ornamented valves. Sineruga Perrier, 2012 and Nudator differ mainly in valve outline in lateral view.

Stratigraphic and geographic range.—Wenlock and Ludlow Series, Silurian of England, Wales ( Perrier et al. 2019), Poland, and possibly France ( 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.