Naticopsis, McCoy, 1844

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 : 28

Naticopsis sp. 2

( Fig. 20 D–F)

Material. One specimen: ESKU-19- LP 46.

Dimensions (mm): ESKU-19- LP 46: height = 9.3; width = 10.3; apical angle = 112 º; apertural height = 7.5; apertural width = 7.7.

Description. Moderately low-spired shell, naticiform, consisting of three rapidly expanding whorls; whorls smooth, strongly convex, rounded, embracing at periphery; spire low but distinctly elevated; body-whorl inflated, very large and much higher than spire with height about 90% of total height; periphery at about mid-whorl; base convex; suture shallow but impressed; anomphalous; aperture evenly rounded in cross section, lip thin, inner lip arched.

Remarks. Naticopsis sp. 2 differs from Naticopsis sp. 1 in having more flattened upper whorl surface, lacking callus, having a higher whorl expansion rate and a rounded aperture. It resembles Naticopsis subovata Worthen in Meek & Worthen (1873) as illustrated by Knight (1933 b, p. 379, pl. 43, fig. 2a–j) in size, shell shape and pleural angle. N. wortheni Knight, 1933 b (p. 377, pl. 43, fig. 3a–k) is also similar. Knight (1933 b) mentioned that these two species, N. subovata and N. wortheni , are very close to each other but N. subovata can be differentiated from N. wortheni in having a swelling just above the mid-whorl height, and by the shape of the columellar lip, which is evenly crescent-shaped in N. subovata while it is slightly angled in N. wortheni . Although the parietal area of the present specimen is obscure it seems closer to N. subovata . The present specimen is also similar to the specimens illustrated and described as N. praealta Wanner, 1922 by Batten (1979; p. 14, fig. 16a–b) from the Permian of Perak, Malaysia but the latter specimens are more slender and relatively high-spired.

Figures

FIGURE 20. A–C, Naticopsis sp. 1, ESKU-19-LP 47. D–F, Naticopsis sp. 2, ESKU-19-LP 46. G–I, Naticopsis? sp. 3, ESKU- 19-LP 32. J, Naticopsis? sp. 4, ESKU-19-LP 52. K–L, Naticopsis cf. heshanensis Pan & Erwin, 2002, ESKU-19-LP 44. Scale bars represent: 2 mm (A–J); 5 mm (K–L).