Heterosubulites longusapertura, 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 : 34

Heterosubulites longusapertura sp. nov.

( Fig. 22G )

Etymology. Latin, because of the long-shape aperture.

Holotype. Only one specimen: ESKU-19-LP 215 .

Dimensions (mm): ESKU-19- LP 215: height = 1.6; width = 0.9; apical angle = 82 º.

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 very small, fusiform; whorls smooth; whorls embracing high on the whorls; whorls evenly convex with periphery above mid-whorl; spire whorls only slightly convex; spire small, blunt, rounded; body-whorl inflated, much higher than spire with height about 90% of total height; sutures indistinct; base flat; aperture elongated, narrow, with wide and short anterior siphonal canal; outer lip almost straight.

Remarks. Heterosubulites longusapertura sp. nov. is very close to the type species H. blatta ( Knight, 1931 a, p. 203–204, pl. 21, fig. 2a–d) (see also Bandel 2002 a) from the Pennsylvanian of Missouri, USA in shape, size and shell proportions, but H. longusapertura n. sp. differs from H. blatta having a narrower aperture, a much broader anterior siphonal canal and a much more arched outer lip. H. fusiformis Nützel, 2012 from the Middle Permian Akasaka Limestone, Japan is also similar but its shell is larger, the shell is more slender, whorls embrace lower on preceding whorl, its aperture is wider and its anterior siphonal canal is narrower.

Figures

FIGURE 22. A–C, Strobeus? sp. 1, A–B, ESKU-19-LP 49. C, ESKU-19-LP 90. D–E, Strobeus? sp. 2, D, ESKU-19-LP 217. E, ESKU-19-LP 220. F, Girtyspira? sp., ESKU-19-LP 222. G, Heterosubulites longusapertura sp. nov. ESKU-19-LP 215, holotype. Scale bars represent: 2 mm (A–C); 200 μm (D–G).

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.