Trachyspira eleganta, 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 : 32

Trachyspira eleganta sp. nov.

( Fig. 21 G–K)

Etymology. From Latin, meaning elegant, beautiful.

Holotype. Only one specimen ESKU-19-LP 28 .

Dimensions (mm): ESKU-19- LP 28: height = 17.6; width = 13.3; apical angle = 75 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. Medium-size, moderately high-spired shell, conical, subturbiniform, consisting of approximately 5 whorls; apex acute, spire angle 75°; body whorl height about 80 percent of the total height; suture adpressed; earliest two whorls without visible ornament (preservation?), convex; following whorl with fine pustules and narrow shoulder; last two preserved whorls ornamented with two categories of nodes, large nodes arranged in spiral rows and fine, densely spaced nodes arranged in opisthocline rows tending to fuse to opisthocline ribs; body whorl with three rows of nodes,10–14 nodes per row; uppermost nodular row near adapical suture, forming edge of narrow ramp; middle row of nodes strongest, situated near abapical suture; third row with weakest nodes, situated on base; whorl angulated at nodular rows; whorl face concave between nodular rows; base rounded, anomphalous, ornamented with numerous spiral cords consisting of small pustules representing continuations of opisthocline rows on whorl face; aperture acute adapically, outer and anterior lip evenly rounded.

Remarks. This single specimen at hand is assigned to the genus Trachyspira Gemmellaro, 1889 which is characterized by having two different size-categories of nodes: numerous small pustules, aligned in opisthocline rows and few large nodes arranged in spiral rows ( Knight et al. 1960). It is the first report of this genus from Thailand.

Trachyspira eleganta sp. nov. from the Khao Khad Limestone resembles the specimens illustrated and described as T. obliquinodula Wang, 1982 by Pan & Erwin (2002) from the Permian of Guangxi and Yunnan Provinces, South China. The type material of this species as illustrated by Wang (1982) is poorly preserved and not well-documented. However, these specimens as well as those illustrated by Pan & Erwin (2002) are much broader and stouter and hence have a larger apical angle (> 90°) and the nodules are much coarser.

The type species T. delphinuloides Gemmellaro, 1889 as illustrated by Batten (1979, p. 21, figs 29–31) from North Africa and Malaysia is also similar to T. eleganta sp. nov. in having three principal rows of nodes with the second row dominant but Batten’s (1979) specimen have a larger apical angle and the second order pustules are larger in the African specimen. However, the original illustration of T. delphinuloides given by Gemmellaro (1889) shows a specimen with relatively small first order nodules that are spirally elongated. Knight (1941, pl. 56) figured a specimen form the type series that differs considerably from Gemmellaro’s (1889) figure. Nevertheless, Knight (1941) identified this specimen as possible holotype. This specimen (probably the one used for the drawing in the Treatise, Knight et al. 1960, fig. 182/6) differs from our specimen in having a broader ramp, finer second order and stronger first order nodes, especially the adapical ones. T. heshanensis Pan & Erwin, 2002 (p. 25, fig. 12.11–12.14) from the Late Permian of China has a larger apical angle (close to 90°), the first order nodes are weaker at comparable growth stages and it lacks a third row of first order nodes on the base. T. quangxiensis Pan & Erwin, 2002 (p. 25, fig. 12.9–12.10) from the Late Permian of China has more convex whorls, a wider ramp and three instead of two rows of first order nodes on the whorl face.

Figures

FIGURE 21. A–D, Trachydomia suwanneeae sp. nov., ESKU-19-LP 26, holotype. E–F, Trachydomia cf. nodusum (Meek & Worthen, 1866), ESKU-19-LP 92. G–K, Trachyspira eleganta sp. nov., ESKU-19-LP 28, holotype. Scale bars represent: 2 mm (A–D, G–K); 1 mm (E–F).

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.