Middle Permian (Roadian) gastropods from the Khao Khad Formation, Central Thailand: Implications for palaeogeography of the Indochina Terrane Author Ketwetsuriya, Chatchalerm Author Karapunar, Baran Author Charoentitirat, Thasinee Author Nützel, Al- Exander text Zootaxa 2020 2020-04-17 4766 1 1 47 journal article 22833 10.11646/zootaxa.4766.1.1 ed4d1bf6-284a-4898-952a-58943d5a3026 1175-5334 3763907 urn:lsid:zoobank.org:pub:B1B5DA41-5035-4783-8D47-28857B6305AE Trachydomia suwanneeae sp. nov. ( Fig. 21 A–D) Etymology. In honor of Suwannee Phomprasith for her work in biodiversity in Thailand . Holotype . ESKU-19-LP 26 . Paratypes . ESKU-19- LP 27, 94. Dimensions (mm): ESKU-19- LP 26: height = 12.1; width = 9.2; apical angle = 82 º . ESKU-19- LP 27: height = 6.4; width = 5.7. ESKU-19- LP 94: height = 5.4; width = 4.2. 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 naticiform to turbiniform; spire acute; whorls round, convex; body whorl distinctly higher than spire; whorls ornamented with distinct small nodes which are especially well-developed on the body whorl and weak or absent on the earliest preserved whorls; nodes roughly arranged in opisthocline arranged nodes; distance between nodes exceeds diameter of nodes; suture distinct; whorls convex with periphery at mid-whorl of body whorl but below mid-whorl of whorl face of spire whorls, with narrow subsutural ramp; base convex with gradually embracing of body whorl at transition below the periphery; aperture unknown; anomphalous. Remarks. Based on the shell characters of the studied specimens such as having a naticiform shell and pustules on whorl face, the present material represents undoubtedly the genus Trachydomia . Trachydomia suwanneeae sp. nov. resembles most closely T . dussaulti Mansuy, 1913 a (p. 101, pl. 11, fig. 5a–b) from the Permian Productus Limestone of Laos in shape and ornaments that was also reported by Batten (1979 , p. 17, fig. 20) from the Permian of Perak , Malaysia and by Delpey (1941 , p. 268, fig. 10) from the Permian of Cambodia . However, T. dussaulti is not as high-spired and hence its spire is not as acute. T. dussaulti has more nodes and the nodes are more densely spaced. The specimen illustrated as T . dussaulti Mansuy, 1913 a by Delpey (1941) has a more distinctly inflated body whorl, a blunter spire and finer nodes, whereas the specimens assigned to T . nodusum ( Meek & Worthen, 1866 ) by Delpey (1941 , p. 268, fig. 9) is more similar to the present specimens in having an acute spire and a rather elongated shape. Knight (1933 b ) has reported several specimens of T . nodusum from the Pennsylvanian, USA (from which this species was originally described) differs distinctly from the studied specimens in having a lower spire, a broader and more pronounced ramp, stronger and coarser nodes and more inflated body whorl. T . suwanneeae sp. nov. also resembles T . whitei Knight, 1933 b , both in having small and widely spaced nodes and a similar whorl profile but T . whitei differs from T . suwanneeae sp. nov. by its wider, more pronounced subsutural ramp, by being broader and by having stronger nodes. T . suwanneeae sp. nov. is also similar to T . takhliensis Nützel & Ketwetsuriya, 2016 ( Ketwetsuriya et al . 2016 , p. 502, fig. 19J–M) from the Middle Permian of the Tak Fa Limestone, Thailand . However, the shell of T . takhliensis is broader, its spire is less acute and it has more inflated body whorl. T . takhliensis has more densely spaced, somewhat coarser and more protruded nodes and a more pronounced ramp.