Thalerosphyrus sinuosus Navás, 1933 (Figures 2 (a–c), 6(b), 7(b), 8(a), 9(b), 10(b), 11(b)) Materials examined THAILAND; 1 larva (on slide), Ton Sator waterfall, Phatthalung Prov., 7.195383°N, 100.071533°E, alt. 101 m, 12-III-2016, B. Boonsoong leg. (ZMKU); 4 larvae (2 on slides; 2 in ethanol), Khao Luang waterfall, Lan Sa Ka, Nakhon Si Thammarat Prov., 8.369071°N, 99.735035°E, alt. 533 m, 2-VII-2016, B. Boonsoong leg. (ZMKU); 3 larvae (1 on slide; 2 in ethanol), Boripat waterfall, Songkla Prov., 6.995033°N, 100.150933°E, alt. 171 m, 12-III -2016, B. Boonsoong leg. (ZMKU); 3 larva (1 on slide; 2 in ethanol), Ton Nga Chang, Songkla Prov., 6.949000°N, 100.235033°E, alt. 119 m, 12-III-2016, B. Boonsoong leg. (ZMKU); 1 larva (in ethanol), Huai Sat Lek, Hua Hin district, Prachuap Khiri Khan Prov., 12.635750°N, 99.509917°E, alt. 166 m., 25-II-2018, B. Booonsoong leg. (ZMKU); 2 larvae (in ethanol), Chan Ta Then waterfall, Sri Racha, Chonburi Prov., 13.242400°N, 101.044200°E, alt. 162 m, 6-VI-2018, B. Boonsoong leg. (ZMKU); 1 larva (in ethanol), Nok Ngang, Ranong Prov., 9.706066°N, 98.577366°E, alt. 11 m., 21-IV-2018, B. Booonsoong leg. (ZMKU) Head. Labrum slightly expanded laterally, ca. 3.5 times larger than long, with rounded apexes; dorsal surface and anterior margin covered with long and thin setae. Crown of the galea-lacinia of the maxillae with ca. 22–25 comb-shaped setae. Right mandible with 7–8 fimbriate setae below the inner incisor and ca. 4–5 long simple and thin setae below the mola. Left mandible with 10–11 simple and fimbriate setae below the inner incisor and ca. 6–7 long simple and thin setae below the mola. Hypopharynx with robust lingua bearing a tuft of small setae, superlinguae densely covered with long and thin setae up to the lower part of the superlinguae. Labium with glossae rhomboid slightly concave on their inner and outer margin near apex (Figure 6 (b)). Thorax. Pronotum slightly expanded laterally and posteriorly and basally fused to mesonotum (Figure 2 (a–b)). Femora with submarginal rows of pointed bristles on inner and outer margins, increasing in numbers from the fore to the hind leg. Bristles on dorsal surface of hind femora arrow shaped, clearly pointed (Figure 7 (b)). Hind tibia with two rows of thin setae (Figure 8 (a)) and a row of 7–8 arrow-shaped bristles in the marginal or submarginal position. Tarsal claw with 3–4 teeth (Figure 9 (b)). Abdomen. Posterolateral expansion not developed on segment I, weakly developed on segment II, strongly developed on segment III and increasing size up to VIII and divergent with the body (Figure 2 (c)). Gill I with asymmetrical elongated and rounded plate, 2 times longer than wide (Figure 10 (b)). Gill III–VI strongly asymmetrical, wider than long. Gill VII oval and almost symmetrical with inner concave margin near apex. Posterior margin of the tergites with irregularly pointed teeth, and numerous microdenticle rows (Figure 11 (b)). Cerci whitish in proximal part, with 3–4 dark brown bands increasing size towards apex.

Published as part of Sutthacharoenthad, Waranid, Sartori, Michel & Boonsoong, Boonsatien, 2019, Integrative taxonomy of Thalerosphyrus Eatonı 1881 (Ephemeropteraı Heptageniidae) in Thailand, pp. 1491-1514 in Journal of Natural History 53 (23) on page 1496, DOI: 10.1080/00222933.2019.1657513, http://zenodo.org/record/3670187