Palaumysis Bacescu

Hanamura, Yukio & Kase, Tomoki, 2002, Marine cave mysids of the genus Palaumysis (Crustacea: Mysidacea), with a description of a new species from the Philippines, Journal of Natural History 36 (3), pp. 253-263 : 254-255

Palaumysis Bacescu and IliOEe, 1986

Palaumysis Bacescu and IliOEe, 1986b: 31.

De W nition

Carapace reduced, leaving last ®ve thoracic somites uncovered. Telson entire, sub-triangular, armed with pair of distal spines, no plumose setae on all margins. Exopod of uropod shorter than endopod, armed laterally with a few setae on posterior half. Eye well developed, cornea globular. Antennule with peduncular segment 3 robust and longest, bearing three to ®ve sensory setae at base of outer ¯agellum, inner ¯agellum very short, composed of four or ®ve articles, male lobe undeveloped. Antennal scale vestigial. Labrum evenly convex anteriorly, without frontal process or spine. Endopods of thoracic limbs 3±8 rather stout, carpo-propod i unsegmented, shorter than meri. Male pleopods rudimentary, unsegmented, pleopod 1 with procurved long seta distally, pleopod 4 ending in strong spine. Female pleopods tiny, unsegmented. Marsupium consisting of two pairs of lamellae.

Type species. Palaumysis simonae Bacescu and IliOEe, 1986.

Remarks

Bacescu and IliOEe (1986b) reported that Palaumysis simonae has no antennal scale. However, re-examination of the paratypes (USNM 227132) and further specimens from the Palau Islands showed that P. simonae possesses a sharp, small process arising from the distodorsal part of the protopod of the antenna. Detailed SEM observations veri®ed this process to be a reduced scale. The original authors might have overlooked this structure.

Bacescu and IliOEe (1986b) proposed the tribe Mancomysini to receive Palaumysis simonae . Nouvel et al. (1999), in contrast, assigned this genus to the tribe Erythropini , and Michthyops W. M. Tattersal l to a new taxon Calyptommini , without a detailed justi®cation for this classi®cation. Although Palaumysis resembles certain Erythropini genera in the shape of the telson, possessing a rudimentary antennal scale and rather stout thoracic endopods, this genus is remarkable in having a combination of the following features: the carapace is considerably reduced, the pleopods are tiny in both sexes and the inner ¯agellum of the antennule is much reduced. We are inclined to support Bacescu and IliOEe’s scheme, giving more weight to reduced, unsegmented male pleopods.

Recently, OrtõÂz et al. (1997) reported an interesting mysid, Gironomysis lalanai , from an anchialine cave in Cuba. Gironomysis in general resembles Palaumysis in having a reduced antennal scale, tail fan and other appendages. However, the carapace of Gironomysis covers nearly the whole of the thoracomeres and the inner antennular ¯agellum has an extraordinary elongated terminal article, which is unusual in all other known mysids. Males of Gironomysis have not been discovered yet, so debate on the higher taxonomic position of this mysid deserves future studies.