Holopea sp.

Holopea sp.

Fig. 3H, I View Fig .

2020 Holopea sp. ; Bertero 2020: p. 54, pl. 3: 14, pl. 6: 3.

Material.— CEGH-UNC 25445–25452 , eight recrystallized teleoconch; from the Hirnantian, Upper Ordovician , Don Braulio Formation (level 2B), Quebrada de la Vinchuca, Sierra de Villicum, San Juan Province, Argentina .

Description.—Globose, turbiniform, small sized-shell with a height of 30−57 mm and a width of 27−58 mm. Pleural angle of 70°−80°. The teleoconch consists of 2 or 3 1/2 rapidly expanding and strongly convex whorls. Sutures incised. The ornament consists of fine orthocline growth lines. Basal, umbilical and apertural characters not visible in the available material.

Remarks.— Holopea is a quite problematic genus considering that it lacks well defined and precise diagnostic characters for its taxonomic assignment ( Yochelson 1963; Wagner 2002). Rohr (1980) ascribed the pleural angle as a character to distinguish different species within the genus. Following Rohr’s 1980) criteria, Holopea sp. is similar to Holopea glindmeyeri Rohr, 1980 (181, pl. 9: 4–8), from the Middle Ordovician of North America, which shows a pleural angle of 75–90°; however, the North America species is much smaller, and each whorls embrace previous whorl at about midline. Holopea elizabethi Rohr, 1980 (180: pl. 9: 28–37), from the Middle/ Upper Ordovician of North America, also shows a similar pleural angle of 72°, but differs from the Argentinean species in having a higher spire and closely spaced and distinct prosocline growth lines. Holopea brucei Rohr, 1980 (181, pl. 9: 25–27), from the Middle Ordovician of North America, has a wider pleural angle of 105°, a narrow and deep umbilicus, closely spaced prosocline growth lines. Holopea mobergi Troedsson, 1918 (in Ebbestad et al. 2013: 318, fig. 10), from the Katian–Hirnantian, Upper Ordovician of Sweden, differs from the Argentinean species in having a much smaller shell and a slightly more pointed spire. Radvanospira antiquata Perner, 1903 ) (in Horný 1997, as Holopea? antiquata : 60, pl. 15, 16; Ebbestad et al. 2019: 456, figs. 13a–g, 14a–h) from the Sandbian–Hirnantian, Upper Ordovician of Spain, Morocco, Bohemia and Iberia, has a more globose or naticiform shell, with more distinctly and dense growth lines and an auriform aperture. Holopea sp. (in Frýda et al. 2001: 125, fig. 3A, B), from the Katian–Hirnantian, Upper Ordovician of Spain, has fine spiral and collabral elements on the shell surface forming reticulate ornament pattern, and strongly prosocline growth lines on last whorl. Considering that Holopea? antiquata was removed to the genus Radvanospira (see Ebbestad et al. 2019), the species here described is the first certain report of Holopea in the Hirnantian, Late Ordovician environments of Gondwana.