Neoleptastacus ornamentus Sak et al. 2008

Neoleptastacus ornamentus (Mielke, 1987) Arenopontia ornamenta Mielke, 1987 Arenopontia (Neoleptastacus) ornamenta Mielke, 1987: Bodin (1988: 163) Neoleptastacus ornamentus (Mielke, 1987) Sak et al. (2008: 412) Original description. Mielke (1987): 338–342; Abb. 15–17. Type locality. Chile, Antofagasta Region, Antofagasta Province, 25 km north of Antofagasta, La Rinconada, few km north of La Portada; fine grey-brown sandy beach. Body length. 300–410 μm (♀), 350–380 μm (♂). Remarks. Neoleptastacus ornamentus and N. reductaspina are the only species of the acanthus -group that exhibit a conspicuous integumental pattern of elongate rectangular plates on the ventral and dorsal surfaces of the urosomites (except the anal somite). Similar plates have also been reported in a single species, N. clasingi, of the spinicaudatus -group. Such internal integumental reinforcements interspersed with areas of almost membranous cuticle is an obvious adaptation to life in the interstitial habitat, enhancing flexibility and wriggling ability in the lacunae between the sediment grains. Similar integumental patterns have been observed on the prosome and/or urosome of members of other marine mesopsammic families, including the Leptastacidae (Huys 1992; Huys et al. 1996a), Paramesochridae (Huys 1995; Mielke 1987, 1988) and Psammopsyllidae (Mielke 1983; Karaytuğ & Sak 2005). The species is so far restricted to northern Chile, having been reported from Iquique (Tarapacá Region) and north of Antofagasta (Mielke 1987). It can be differentiated from N. reductaspina by differences in P3–P5, anal somite and caudal rami (see below).