Protostylus, Mansuy, 1914

Ketwetsuriya, Chatchalerm, Karapunar, Baran, Charoentitirat, Thasinee & Nützel, Al- Exander, 2020, Middle Permian (Roadian) gastropods from the Khao Khad Formation, Central Thailand: Implications for palaeogeography of the Indochina Terrane, Zootaxa 4766 (1), pp. 1-47 : 38-40

Protostylus sp.

( Fig. 25 F–H)

Material. Two specimens: ESKU-19- LP 39, 64.

Dimensions (mm): ESKU-19- LP 39: height = c. 16.8; width = 7.8. ESKU-19- LP 64: height = c. 6.9; width = 2.9.

Description. Shell high-spired, slender, consisting of approximately 7 whorls (apex missing); whorls smooth; whorls slightly convex to almost straight, periphery somewhat below mid-whorl; base evenly rounded, convex; anomphalous; sutures shallow but distinct; aperture unknown.

Remarks. These unornamented high-spired shells resemble several Permian Protostylus species e.g. from the Middle Permian Tak Fa Limestone from Thailand ( Ketwetsuriya et al. 2016) but the body-whorl of the present specimens seems to be more inflated. The Japanese Protostylus species from the Middle Permian Akasaka Limestone (Nützel & Nakazawa 2012) are much smaller. Protostylus sp. from the Permian of Ratburi Limestone, Thailand ( Ketwetsuriya et al. 2020) is more slender in shape. The type species, Protostylus lantenoisi Mansuy, 1914 from the Carboniferous of South China (Yunnan) and the specimens illustrated by Batten (1985) from the Permian of Malaysia, differ from the present specimens in being more slender smaller and having lower whorls. The Permian Malaysian species Omphaloptychia paleozoica Batten, 1985 is similar in having high whorls, but it has a moderately high-spired turbiniform shape and a more step-like whorl profile. The studied specimens are also similar to Knightella irregularis ( Longstaff, 1933) but its whorls are somewhat lower and less convex, and it has shallower sutures.

Figures

FIGURE 25. A, Donaldospira sp., ESKU-19-LP 85. B–E, Knightella irregularis (Longstaff, 1933), B–C, ESKU-19-LP 41. D–E, ESKU-19-LP 84. F–H, Protostylus sp., F, ESKU-19-LP 39. G–H, ESKU-19-LP 64. I–N, Trypanocochlea lopburiensis sp. nov. I, M, ESKU-19-LP 210, holotype; oblique view of early whorls to show protoconch. J, ESKU-19-LP 201, paratype. K, ESKU-19-LP 203, paratype. L, ESKU-19-LP 206, paratype; lateral view of early whorls to show protoconch. N, ESKU-19-LP 221, paratype. O–R, Streptacis? khaokhadensis sp. nov., O–P, ESKU-19-LP 214, holotype. Q–R, ESKU-19-LP 213, paratype. Scale bars represent: 2 mm (A–H); 200 μm (I–R).