Apachella thailandensis, Ketwetsuriya & Karapunar & Charoentitirat & Nützel, 2020

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 : 14-15

Apachella thailandensis sp. nov.

( Fig. 11 )

Etymology. After the country of Thailand.

Holotype. ESKU-19-LP 62 .

Paratypes. Four specimens: ESKU-19- LP 25, 60, 89, 100.

Dimensions (mm): ESKU-19- LP 25: height = c. 9.4; width = 5.5; apical angle = 75º. ESKU-19- LP 62: height = 8.5; width = 5.2; apical angle = 60º. ESKU-19- LP 60: height = c. 4.6; width = c. 4.6. ESKU-19- LP 89: height = c. 7.1; width = c. 4.1; apical angle = 66º. ESKU-19- LP 100: height = c. 6.5; width = c. 4.8.

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. Shell high-spired, consisting of 8 whorls, first whorl planispiral; first two teleoconch whorls smooth, rounded, third whorl ornamented with spiral threads; selenizone starts within the 4th whorl; suture slightly impressed; subsutural ramp slightly convex, ornamented with 3–4 spiral ribs that are ornamented with nodes; selenizone concave, ornamented with very faint lunulae, bordered by two straight spiral ribs; lower rib forms periphery; lower whorl face twice as wide as the upper whorl face; lower whorl face slightly convex, ornamented with one spiral rib just above suture, equal in strength to spiral rib bordering the lower edge of selenizone; lower whorl face further ornamented with two spiral threads between two spiral ribs; base convex, ornamented with several evenly spaced spiral ribs of same strength as ribs on lower whorl face; base convex, anomphalous; aperture unknown.

Remarks. Apachella thailandensis sp. nov. has a wider upper whorl face (above selenizone) than other species of Apachella . The ratio of the height of the upper and the lower whorl face of A. thailandensis sp. nov. is similar to that of A. alimillana ( Girty, 1909) . However, the latter lacks spiral ribs on upper whorl face. A. powwowensis Batten, 1995 has a wider selenizone, a median spiral lira on its selenizone and only one spiral rib on its upper whorl face. A. franciscana ( Chronic, 1952) differs by having two faint spiral ribs on the upper whorl face adjacent to the suture, more prominent ribs bordering the selenizone, a stepped whorl profile and a higher whorl expansion rate.

Figures

FIGURE 11. Apachella thailandensis sp. nov.A–D, ESKU-19-LP 62, holotype. E, ESKU-19-LP 25, paratype. F–G, ESKU-19- LP 89, paratype. All scale bars represent 2 mm.

FIGURE 1. Geological map of the study location at Erawan Hill, Chong Sarika sub-district, Phatthana Nikhom district, located about 13 km east of Lopburi Province, Central Thailand.