Description of four new species of the Cirolana ‘parva group’ (Crustacea: Isopoda: Cirolanidae) from Thailand,with supporting molecular (COI) data

Four new species of the Cirolana ‘parva group’ from shallow coastal habitats in Thailand are described: Cirolana andamanensis sp. nov. and C. phangnga sp. nov., from the Andaman Sea, and C. siamensis sp. nov. and C. thailandica sp. nov. from the Gulf of Thailand. Molecular (The cytochrome oxidase subunit I gene) analysis incorporating taxa from the Cirolana ‘tuberculate group’ shows a monophyletic clade (Bayesian inference = 1 and maximum likelihood = 100%) within the Cirolana ‘parva group’ with two clades reflecting morphological characters. Cirolana andamanensis sp. nov. with antennula peduncle articles 1 and 2 entirely fused; male pereopod 1 without a setal fringe; uropod peduncle ventrolateral margin with 1 sensory seta. Cirolana phangnga sp. nov., C. siamensis sp. nov. and C. thailandica sp. nov. share the morphological characters of antennula peduncle articles 1 and 2 distinctly articulated; pereopod 1 in male with a setal fringe on the carpus and propodus; uropod peduncle ventrolateral margin with 3 sensory setae. Uncorrected p-distances strongly support the separation of these species, originally based on morphology, and show that the highest value of 32.1% is between C. thailandica sp. nov. and C. andamanensis sp. nov., while the lowest value of 22.5% is between C. phangnga sp. nov. and C. siamensis sp. nov.