Microthalestris campbelliensis, sp. nov.

Microthalestris campbelliensis sp. nov.

urn:lsid:zoobank.org:act: F47DAF34-B635-46E1-8FE4-AACFEF43218E

Microthalestris forficula (Claus, 1863) var. littoralis sensu Lang (1934)

Differences in the morphology of the P1, female P5 and caudal ramus indicate that Lang’s (1934) material is not conspecific with M. littoralis and deserves distinct specific rank. It differs from all its subantarctic congeners in the armature of P2–P4, including M. minuta comb. nov. with which it shares the proximal position of the inner seta on P1 enp-1.

Original description. Lang (1934): 25–27, Figs 49–56.

Type material. The dissected male specimen illustrated by Lang (1934: Figs 52–56) is here designated as the holotype of P. campbelliensis sp. nov. (ICZN Arts 16.4 and 72.5.6). The species can be differentiated by the characters mentioned in the diagnosis below and those illustrated in Lang (1934) (ICZN Art. 13.1).

Type locality. New Zealand, Campbell Island group, Campbell Island (Motu Ihupuku); Perseverance Harbour (South Harbour); 40 m depth.

Differential diagnosis. Microthalestris. Body length unknown. Antenna with 2-segmented exopod, armature unconfirmed; bearing two setae on exp-1 and two lateral and three apical elements on exp-2; armature of endopod unconfirmed but likely without penicillate spines. P1 exopod about 70% length of endopod; exp-2 elongate, about 2.1 times as long as exp-1, and about 55% length of enp-1; insertion point of inner seta of enp-1 at 20% of inner margin length; exp-3 with four elongate setiform elements; enp-2 with one minute seta and two non-geniculate claws. Armature pattern of ♀ P2–P4: see top of next page.

P3 endopod ♂ 3-segmented, with apophysis on enp-3, armature pattern [1.1.02 + apo]. P 5 ♀ with elongate exopod (about three times as long as maximum width), inner margin and proximal half of outer margin slightly convex, with six elements, outer ones about equally long, outer apical one shorter than inner apical one; endopodal lobe with five elements, innermost one short. P 5 ♂ exopod 3-segmented, with seven elements, outer seta of exp-1 very long, longer than outer basal seta; endopodal lobe with two elements. Armature of P 6 ♂ unconfirmed. Caudal ramus seta V with slightly swollen proximal part.

Etymology. The species name alludes to Campbell Island (Motu Ihupuku), an uninhabited subantarctic island of New Zealand, where the type locality is situated.

Note. Although Lang (1934: 26) claimed his material consisted solely of a pair in amplexus the condition of the caudal ramus (Fig. 49) was figured in two different females. The species is so far only known from the type locality.