Worthenia, de Koninck, 1883

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 : 20

Worthenia sp.

( Fig. 14 O–S)

Material. One specimen: ESKU-19- LP 88.

Dimensions (mm): ESKU-19- LP 88: height = 6.4; width = 4.8; apical angle = 74º.

Description. Shell moderately high-spired, trochiform, consisting of at least 6 whorls; first two teleoconch whorls smooth, convex, rounded; third whorl ornamented with fine spiral threads; mid angulation develops starting from the 4th whorl; suture slightly impressed; subsutural ramp slightly convex, becoming concave just above selenizone; ramp inclining at an angle about 45–55°; subsutural ramp ornamented with four spiral ribs, uppermost two ribs ornamented with weak nodes, lowest one represents upper border of selenizone; mid angulation represents periphery where selenizone is situated; selenizone prominent, ornamented with equally spaced small nodes; lower whorl face concave just below the selenizone, slightly convex otherwise, ornamented with three spiral ribs, uppermost spiral rib represents lower border of selenizone; spiral ribs on lower whorl face stronger than ribs on ramp; suture situated between lowermost two ribs; base convex, ornamented with several evenly spaced, prominent spiral ribs of about same strength as ribs on lower whorl face; base anomphalous; aperture unknown.

Remarks. Worthenia sp. differs from Worthenia cf. pagoda in ornamentation pattern and has a narrower and less ornamented selenizone. The whorl profile of Worthenia sp. is similar to that of W.? constantini ( Mansuy, 1912) from the Carboniferous of Yunnan, but the latter without nodular spiral ribs.

Figures

FIGURE 14. A–I, Worthenia humiligrada sp. nov. A–D, ESKU-19-LP 22. E–F, ESKU-19-LP 33. G–H, ESKU-19-LP 23. I, ESKU-19-LP 34. J–N, Worthenia cf. pagoda Mansuy, 1912, J, ESKU-19-LP 17. K–N, ESKU-19-LP 66. O–S, Worthenia sp., ESKU-19-LP 88. Scale bars represent: 2 mm (A, B, G, H, I, K, L, O); 1 mm (C, D, J, M, N, P–S); 5 mm (E, F).