Bohemograptus bohemicus ( Barrande, 1850 )

Lopez, Fernando E., Conde, Osvaldo A., Braeckman, Alejandro R., Segura, Diego G., Drovandi, Juan M., Bueno, Andrea J. & Abarca, Ulises, 2024, New Ludlovian, upper Silurian, graptolite faunas from the Los Espejos Formation, Central Precordillera, San Juan Province, Argentina: correlations and biostratigraphic remarks, Acta Palaeontologica Polonica 69 (3), pp. 351-370 : 358-359

Bohemograptus bohemicus ( Barrande, 1850)

Figs. 4K , 8A, B .

1850 Graptolithus bohemicus ; Barrande 1850: 40, pl. 1: 15–18.

1936 Monograptus bohemicus ( Barrande, 1850) ; Bouček 1936: 3–4, pl. 1: 1–3.

1958 Pristiograptus bohemicus ( Barrande, 1850) ; Urbanek 1958: 77– 80, figs. 46, 47, 49.

1967 Bohemograptus bohemicus ( Barrande, 1850) ; Přibyl 1967: 136, pl. 1: 1–6.

1990 Bohemograptus bohemicus bohemicus ( Barrande, 1850) ; Lenz 1990: figs. 3A, B.

1997 Bohemograptus bohemicus bohemicus ( Barrande, 1850) ; Zhang and Lenz 1997: 1236, figs. 6M–S, 7I, 7K–M.

2002 Bohemograptus bohemicus ( Barrande, 1850) ; Nilsson 2002: 16, figs. 8B, 9B, C.

2004 Bohemograptus bohemicus bohemicus ( Barrande, 1850) ; Lenz and Kozłowska-Dawidziuk 2004: 32, pl. 37: 1–5, 7; pl. 44: 1–5.

2012 Bohemograptus bohemicus ( Barrande, 1850) ; Sachanski et al. 2012: pl. 1e.

2014 Bohemograptus bohemicus ( Barrande, 1850) ; Štorch et al. 2014: 1032, fig. 13D.

Material.— Two specimens (INGEO-PI-1865, 1879B) with sicula and firsts thecae, well preserved as carbon film and filled by carbonate siltstone from levels PNN-02N and 07S middle to upper Los Espejos Formation , lower Gorstian , lower Ludlow , upper Silurian. Poblete Norte section, Talacasto area, San Juan Province, Argentina .

Description.—Specimens moderate to strongly ventrally curved, only with sicula and firsts thecae present. The dorso-ventral width varies between 0.54–0.66 mm at Th1, 0.56–0.73 mm at Th2, 0.74–0.84 mm at Th3, 0.94–1.02 mm at Th4, and 0.94 mm at Th5. Sicula is slightly ventrally curved, 1.81–1.98 mm long, a moderately flared 0.28–0.29 mm wide aperture, and its apex reaches the Th1 aperture level or slightly above. Virgella and dorsal process visible, with 0.34– 0.14 mm long and 0.05–0.16 mm long, respectively. Th1 shows a concave ventral wall in profile, whereas Th2–5 present tube-like thecae or slightly undulated ventral walls. Thecae incline 31–36° to the tubarium axis. 2TRD values range from 1.37–1.50 mm proximally, the thecal spacing counts 6 in 5 mm, and the overlap is ½.

Remarks.—Uncommon component of the Los Espejos Formation graptolite fauna. The specimens collected in the Los Espejos Formations resemble Bohemograptus bohemicus as described and illustrated by Berry (1964), Urbanek (1970), Lenz (1984), Nilsson (2002), Koren’ and Sujarkova (2004), Lenz and Kozłowska-Dawidziuk (2004), and Wilkinson (2021). This species differs from its derivative species Bohemograptus tenuis ( Bouček, 1936) in its greater width and thecal overlap ( Lenz and Kozłowska-Dawidziuk 2004).

A possible B. bohemicus was mentioned but no illustrated by Suarez-Soruco (1975) in lower Ludlovian levels. This contribution presents the first description and illustration of this taxon in South America.

Stratigraphic and geographic range.—Level PNN-02N and 07S, middle to upper Los Espejos Formation, lower Gorstian, lower Ludlow, upper Silurian. Poblete Norte section, Talacasto area, San Juan Province of Argentina.

Genus Lobograptus Urbanek, 1958

Type species: Monograptus scanicus Tullberg, 1883 ; Ludlow of the Scania ( Sweden) .

Figures

Fig. 4. The early Gorstian (Ludlow, Silurian) graptolite fauna: Uncinatograptus uncinatus notouncinatus (Cuerda, 1969) (A–C), Uncinatograptus elsae sp. nov. (D–F), Uncinatograptus lisandroi sp. nov. (G–J), and Bohemograptus bohemicus(Barrande, 1850) (K) of the Los Espejos Formation, Talacasto Range, San Juan Province, Argentinian Precordillera. A. INGEO-PI-2028, level PNN-06S. B. INGEO-PI-2067, level PNN-02N. C. INGEO-PI-2122, level PNN-02N. D. INGEO-PI-1870, level PNN-02N. E. INGEO-PI-2042, level PNN-02N. F. INGEO-PI-2087, level PNN-02N. G. INGEO-PI-2134A, level PNN-02N. H. INGEO-PI-2048A, level PNN- 02N. I. INGEO-PI-2133, level PNN-02N. J. INGEO-PI-2126, level PNN- 02N. K., INGEO-PI-1865, level PNN-02N. Scale bars 1 mm.

Fig. 8. Line drawings of the Ludlow (Silurian) graptolite fauna of the Los Espejos Formation, Talacasto Range, San Juan Province, Argentinian Precordillera: early Gorstian Bohemograptus bohemicus (Barrande, 1850) (A, B), Saetograptus cf. S. varians (Bouček, 1936) (C, D), and Lobograptus sp. (E), the early Gorstian to early Ludfordian Saetograptus argentinus argentinus (Cuerda, 1969) (F–I). A. INGEO-PI-1865, level PNN-02N. B. INGEO-PI-1879 B, level PNN-08S. C. INGEO-PI-2187, level PNN- 04S. D. INGEO-PI-2198A, level PNN-04S. E. INGEO-PI-2144A, level PNN-05N. F. INGEO-PI-2199A, level PNN-04S. G. INGEO-PI-2195, level PNN-04S. H. INGEO-PI-2195, level PNN-04S. I. INGEO-PI-2200A, level PNN-04S.