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.