Zootaxa 1877: 37-48 (2008)

A new species of freshwater crab of the genus Geothelphusa, G. siasiat sp. nov., is described from Hsinchu and Miaoli counties, northwestern Taiwan. The new species can be distinguished morphologically from similar and geographically close species from western Taiwan by a suite of characters of the carapace, ambulatory legs, thoracic sternum, male abdomen, and male first pleopods. Comparisons of the DNA sequences encoding parts of the mitochondrial large subunit (16S) rRNA and cytochrome oxidase subunit I (COI) genes of specimens from western Taiwan further corroborate this finding. The opportunity is taken here to discuss the taxonomy of the poorly known species, Geothelphusa candidiensis Bott, 1967, based on a re-examination of the holotype, and the distribution of Geothelphusa species from western Taiwan. The report of G. siasiat sp. nov. brings the total number of species of Geothelphusa species known to 52.

Key words: 16S rRNA, cytochrome oxidase I, Geothelphusa siasiat, G. candidiensis, G. olea, Taiwan, taxonomy

FIGURE 2. Male right first and second gonopods of Geothelphusa siasiat sp. nov. (holotype, NMNS 5688-001). a, G1, ventral view.; b, G1, dorsal view; c, distal part of G1, proximal ventral view (distal half of synovial membrane is situated in a horizontal position); d, G1, inner view; e, G2. Scales, 1 mm.

FIGURE 3. Geothelphusa candidiensis Bott, 1967. a, habitus, dorsal view of the holotype (SMF 2855); b, cephalothorax, ventral view of the holotype; c, live coloration of a male, dorsal view; d, frontal view of a live male.

FIGURE 4. Male left first and second gonopods of Geothelphusa candidiensis Bott, 1967 (holotype, SMF 2855). a, G1, ventral view; b, G1, dorsal view; c, distal part of G1, proximal ventral view (distal half of synovial membrane is situated in a horizontal position); d, G1, inner view; e, G2. Scales, 1 mm.

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