Gosseletina microstriata sp. nov.

(Fig. 13)

Etymology. From Latin micro, meaning small, and Latin stria, meaning furrow, referring the tiny spiral ornaments.

Holotype. ESKU-19-LP 29.

Paratypes. Two specimens: ESKU-19- LP 5, 14.

Dimensions (mm): ESKU-19- LP 5: height = c. 3.8; width = c. 4.4. ESKU-19- LP 14: height = 2.2; width = 2.2. ESKU-19- LP 29: height = 7.3; width = 8.3.

Type locality and stratigraphical range. Erawan Hill, Chong Sarika sub-district, Phatthana Nikhom district, located about 13 km east of Lopburi Province, Central Thailand (Fig. 1), Khao Khad Formation, Saraburi Group, Middle Permian, Roadian.

Description. Low-spired, globose shell, medium-sized, comprising c. 4.5 whorls; apex obtuse; spire distinctly elevated; body-whorl broad and inflated, covering approximately 80% of the entire height; whorls rapidly increasing; whorls distinctly convex; whorl surface with numerous very thin, faint spiral threads; whorls embracing at periphery; selenizone broad, situated high on whorl, above periphery, flush with whorl surface or very slightly convex, ornamented as on whorl face; suture impressed but shallow; base rounded; aperture unknown.

Remarks. Gosseletina microstriata sp. nov. differs from other Gosseletina species in several aspects. G. aspeniana (Girty, 1927) (Early Carboniferous, USA) is with faint spiral threads but differs by its whorl profile with distinctly convex whorl face above selenizone. G. permiana Batten, 1989 (Permian, USA) has a coarser spiral ornament and deeper sutures. G. nodosa Batten, 1966 a (Early Carboniferous, England) has subsutural axial riblets and lacks a spiral micro-striation. G. portlockiana (de Koninck, 1843) (Early Carboniferous, Europe) has a stronger spiral striation (Batten 1966 a). G. johnsoni Thein & Nitecki, 1974 is more slender and has a cancellate ornament in subsutural position. G. callosa (de Koninck, 1843) (Carboniferous, Belgium), the type species of Gosseletina, lacks spiral ornament (Knight 1941). G. persimplex (Girty, 1915) (Pennsylvanian, USA) lacks spiral ornament and is more low-spired (Hoare 1961). G. subglobosa (Hall in Miller, 1877) (Early Carboniferous, USA) has a coarser spiral ornament. G. spironema (Meek & Worthen, 1866) (Pennsylvanian, USA) has a coarser spiral ornament and prosocyrt folds on whorl face above selenizone (Kues & Batten 2001).