Nanomysis siamensis W.M. Tattersall, 1921

Yolanda, Rofiza, Ambarwati, Reni, Rahayu, Dwi Anggorowati, Budijastuti, Widowati, Fitrihidajati, Herlina, Kuntjoro, Sunu, Rachmadiarti, Fida & Purnomo, Tarzan, 2023, An annotated checklist of the species of Lopogastrida and Mysida (Crustacea Peracarida) from Thailand and its adjacent waters, Zootaxa 5244 (3), pp. 201-232 : 214

Nanomysis siamensis W.M. Tattersall, 1921

Type locality. Songkhla Lagoon System, Thailand (W.M. Tattersall 1921) .

Record from Thailand. Songkhla Lagoon System, southern Thailand (W.M. Tattersall 1921; Lheknim & Yolanda 2020; Yolanda 2021; Yolanda & Lheknim 2021; Yolanda et al. 2022a).

Habitat and depth range. From the shallow zone of the lagoon (~ 1 to 2 m) to the middle of the lagoon ( Lheknim & Yolanda 2020; Yolanda 2021; Yolanda & Lheknim 2021; Yolanda et al. 2022a).

Distribution. This species is only known from the Songkhla Lagoon System, southern Thailand (W.M. Tattersall 1921; Lheknim & Yolanda 2020; Yolanda 2021; Yolanda & Lheknim 2021; Yolanda et al. 2022a) and there is no record that this species occurs outside of the lagoon, such as the Gulf of Thailand or the Andaman Sea.

Remarks. A total of three species of the genus Nanomysis have been identified from Southeast Asia water, N. insularis , N. siamensis and N. philippinensis . The species N. siamensis may be distinguished from N. philippinensis by the following characteristics; (1) the anterior median part of the carapace bearing short stout triangular process, while no process in N. philippinensis , (2) the precoxal lobe of the maxillule bearing five long barbed and four simple setae, while three long stout and six simple setae in N. philippinensis , (3) the adult males and females of N. siamensis are larger than N. philippinensis , (4) the telson is armed with 5–13 lateral spines and convex posterior margin with 8–21 spines, while N. philippinensis has 5–9 lateral spines concaved posterior margin with 5–10 spines.

Nanomysis siamensis also differs from N. insularis where (1) the eye is slightly depressed, sub-quadrangular and cornea about 2/5 of the whole eye from dorsal aspect, while it is globular and cornea about 1/2 of the whole eye in N. insularis , (2) 1/3 part lateral margin of the antennular peduncle armed with four hooked setae in male and female, while only two hooked setae present in female of N. insularis , (3) the outer margin of the second article of the mandibular palp bearing seven or eight setae, while 13 setae in N. insularis , (4) the telson is armed with 5–13 lateral spines and convex posterior margin with 8–21 spines, while N. insularis has 11–12 lateral spines concaved posterior margin with 15 spines ( Yolanda et al. 2022a)