<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Worthenia humiligrada Ketwetsuriya & Karapunar & Charoentitirat & Nützel 2020, sp. nov.</title> <meta http-equiv="content-type" content="text/html; charset=UTF-8"/> </head> <body> <h2> <i> Worthenia humiligrada</i> sp. nov.</h2> <p> ( Fig. 14 A–I)</p> <p> <b> Etymology.</b> From Latin humilis, meaning low, and Latin gradus, meaning step, referring to the low-stepped whorl profile.</p> <p> <b> Holotype.</b> ESKU-19-LP 22.</p> <p> <b> Paratypes.</b> ESKU-19- LP 23, 33, 34, 35, 74</p> <p> Dimensions (mm): ESKU-19- LP 22: height = 6.8; width = 7.0; apical angle = 98º. ESKU-19- LP 23: height = 10.5; width = 12.7. ESKU-19- LP 33: height =<i> c</i>. 16.0; width = 13.8; apical angle = 92º. ESKU-19- LP 34: height =<i> c</i>. 9.0; width = 11.3; apical angle = 110º. ESKU-19- LP 35: height =<i> c</i>. 10.9; width = 13.6; apical angle = 110º. ESKU- 19- LP 74: height =<i> c</i>. 1.7; width =<i> c</i>. 3.1.</p> <p> <b> Type locality and stratigraphical range.</b> 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.</p> <p> <b> Description.</b> Shell low-spired for genus, gradate, trochiform; first whorl planispiral; early teleoconch whorls (about first two or three whorls) low-spired, smooth, convex, rounded; second and third whorls with fine spiral and axial ribs; suture distinct and impressed; later whorls sharply angulated at about mid-whorl face, the middle angulation separates subsutural ramp from subvertical lower whorl face; subsutural ramp slightly convex near adapical suture to concave on the remaining part; ramp inclining at an angle of 35–50°; subsutural ramp ornamented with up to eight spiral ribs and equally spaced prosocyrt fine collabral ribs or strengthened growth lines; spiral ribs and collabral ribs form nodes at intersections, forming fine reticulate pattern; ornamentation more prominent near adapical suture; lower whorl face subvertical, concave, ornamented with up to six strong spiral cords and numerous faint prosocyrt collabral threads or growth lines; mid angulation forms crest-like periphery of whorl where selenizone situated; selenizone sharply angular covered by v-shaped lunulae; lunulae form nodes when intersecting with angulation; selenizone bordered with fine spiral ribs, upper rib represents lowest spiral rib of subsutural ramp, while lower rib represents uppermost spiral rib of the subvertical lower whorl face; intersections of lunulae and angulation nodular; basal edge sharply angulated; base convex, ornamented by several evenly spaced spiral ribs and very weak opisthocyrt collabral threads; suture shallow, indistinct; narrowly phaneromphalous; aperture unknown.</p> <p> <b> Remarks.</b> The convex early teleoconch whorls, the position and the ornamentation pattern of the selenizone suggest that this species belongs to the genus<i> Worthenia</i> de Koninck, 1883. The distinguishing characters of<i> Worthenia humiligrada</i> sp. nov. are the relatively low spire, wide umbilicus, weak subsutural convexity of the ramp, sharp angulation at the basal edge and nodular selenizone. The combination of these characters distinguishes<i> W</i>.<i> humiligrada</i> sp. nov. from the other species belonging to the genus<i> Worthenia</i>.</p> <p> There are some similar Permian species in Southeast Asia which have been assigned to<i> Worthenia</i>, for instance<i> W</i>.<i> multicarinata</i> ( Mansuy, 1912) from the Carboniferous of Yunnan, China ( Mansuy 1912) and the Permian of Cambodia ( Delpey 1941) and Malaysia ( Batten 1972, p. 32, figs 36–38) is very similar in shape but it has more prominent subsutural nodes on the upper whorl face, a distinctly impressed suture and its basal edge is rounded angular and ornamented with nodes. The type specimens of<i> W</i>.<i> schirjaevensis</i> ( Stuckenberg, 1905) from the Upper Carboniferous of Samara, Russia and the specimens assigned to<i> W</i>.<i> schirjaevensis</i> from the Permian of Cambodia ( Delpey 1941, fig. 27) has a very similar whorl profile and ornamentation but they differ from<i> W</i>.<i> humiligrada</i> sp. nov. by having a higher spire. According to Batten (1972, fig. 38),<i> W</i>.<i> schirjaevensis</i> ( Stuckenberg, 1905) lacks nodes on the selenizone.<i> W</i>.<i> arizonensis</i> Winters, 1963 from the Permian of Arizona is another species with planispiral early whorl but differs from<i> W</i>.<i> humiligrada</i> sp. nov. by having a narrower upper whorl face, a very prominent subsutural convexity, by lacking the sharp angulation at the basal edge and by having a very narrow or no umbilicus.<i> W</i>.<i> crenulata</i> Batten, 1989 from the Permian of southwestern United States, with steeper upper whorl face and more prominent nodes on its selenizone. The specimens assigned to<i> W</i>.<i> corrugata</i> Chronic, 1952 by Batten (1989) differ from<i> W. humiligrada</i> by having a stronger spiral ornament, a sharper collabral ornament and by the presence of axial folds on its upper whorl face. The specimens assigned to<i> W</i>.<i> corrugata</i> by Kulas & Batten (1997) from the Permian of Wyoming differ by having a narrow umbilicus and faint lunulae.</p> </body> </html>