Saetograptus argentinus argentinus ( Cuerda, 1969 )

Saetograptus argentinus argentinus ( Cuerda, 1969)

Fig. 7A, B View Fig , 8E, I View Fig .

1969 Monograptus argentinus ; Cuerda 1969: 231–234, pl. 1: a–d; pl. 2: 4–6.

1971 Monograptus argentinus Cuerda, 1969 ; Cuerda 1971: 399, pl. 5: 1–11, pl. 31: 4–6.

1996 Saetograptus (? Colonograptus ) argentinus ( Cuerda, 1969) ; Rickards et al. 1996: 120, figs. 7e–h, 11h.

2002 Saetograptus argentinus argentinus ( Cuerda, 1969) ; Maletz et al. 2002: 334–336, text-fig. 2g, i–m, pl. 1: 2, 4.

2019 Saetograptus argentinus? ( Cuerda, 1969) ; Lopez 2019: 77, figs. 21h–i, 22b.

2022 Saetograptus argentinus argentinus ( Cuerda, 1969) ; Lopez 2022: 28–30, figs. 3.1–3, 3.5–8, 4.1–3.

Material.—Several juvenile and mature tubaria (INGEO- PI-2138–2146, 2178, 2190, 2195–2197, 2202–2203, 2206, 2208A– B, 2214–2217, 2219, 2221–2227, 2247) well preserved and filled by carbonate siltstone from levels PNN-04N, 05N, 04S, 07S, 08’S, and 08S, middle to upper Los Espejos Formation, lower Gorstian, lower Ludlow, upper Silurian. Poblete Norte section, Talacasto area, San Juan Province, Argentina.

Description.—The material found in the Los Espejos Formation possesses both juvenile and mature specimens with an absent proximal end, and a few complete tubaria preserved in relief, filled by carbonate or oxidized pyrite. Straight tubaria, with a maximum length of 26.4 mm, having thirty-one thecae and a broken proximal end. The proximal dorso-ventral width without spines is 0.82–1.11 mm at Th1, 0.93–1.39 mm at Th2, 1.07–1.44 mm at Th3, 1.11–1.36 mm at Th5, and 2.07–2.51 mm distally. Thecae possess ventrally directed lateral apertural spines up to Th3–6, with a rapid distalward transition to pristiograptid thecae with even apertures. The sicula is 2.05–2.26 mm long, and 0.25–0.46 mm wide at the aperture which possesses 0.37–0.44 mm long virgella and 0.14–0.51 mm antivirgellar spine. Sicular apex reaches up to the level of the aperture of Th2–3. The 2TRD is 1.17–1.21 mm at Th2, and 1.79–1.97 mm distally. Thecal spacing equals 5–8 thecae in 5 mm, and the thecal overlap is one half proximally to three-fifths distally. The thecal inclination decreases from 50° proximally to 36–30° distally.

Remarks.— These measures agree with those reported by Cuerda (1965), Cuerda (1969), Rickards et al. (1996), Maletz et al. (2002) and Lopez (2022) for S. a. argentinus . This subspecies can be differentiated from S. a. robustus mainly by its narrower tubarium (2.51 mm vs 3.2–3.8 mm) and much lower thecal inclination distally (30° vs 55°).

Stratigraphic and geographic range.—Levels PNN-04N, 05N, 04S, 07S, 08’S, and 08S, middle to upper Los Espejos Formation, lower Gorstian, lower Ludlow, upper Silurian. Poblete Norte section, Talacasto area, San Juan Province of Argentina.