Penicillicaris gen. nov.

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Ever since the discovery and description of Thalestris pectinimana Car, 1884, the presence of penicillate elements on the antennary endopod and the distal exopodal and endopodal segments of P 1 in various related forms (Scott 1894a; Brian 1921; Monard 1928; Willey 1935; Sewell 1940; Bodin 1964; Vervoort 1964) has been uncritically accepted as part of the documented variability allegedly displayed by Parastenhelia spinosa (Lang 1948 and others) and unfortunately did not receive the attention it deserved. Sewell (1940) for example, claimed that Monard’s (1928) penicillate form from Banyuls-sur-Mer referred to Parastenhelia littoralis while his own material from Bermuda listed under the latter name cannot possibly be conspecific with the species described by Sars (1911). A new genus, Penicillicaris gen. nov., is proposed here to accommodate four forms that had previously been subsumed in the Parastenhelia spinosa complex and are attributed full species rank.Another three forms are placed with reservations in the genus as species inquirendae: Microthalestris forficula (Claus, 1863) sensu Scott (1894a), M. littoralis Sars, 1911 sensu Brian (1921) and M. littoralis Sars, 1911 f. scotti sensu Sewell (1940).

A number of records refer to the penicillate form but are not accompanied by illustrations. Such indeterminable records include those from Visakhapatnam (formerly Waltair), Andhra Pradesh in India (Krishnaswamy 1957 – as Parastenhelia littoralis f. pencillata [sic]), Dalkey Island and The Muglins, Co. Dublin (Roe 1958) and Lough Hyne (Ine), Co. Cork (Roe 1960; Sloane et al. 1961) in Ireland (all P. spinosa f. penicillata), and Rovinj in Croatia (Zavodnik 1969 – as P. spinosa var. penicillata).

Diagnosis. Parastenheliidae. Sexual dimorphism in antennule, P3 endopod, P5–P6 and urosomal segmentation; occasionally in P4 endopod (Pe. penicillata sp. nov.). Body subcylindrical; condition of hyaline frills of cephalothorax and somites unconfirmed. Rostrum defined at base, reaching at most to halfway second segment of antennule; linguiform. Anal operculum semicircular, bordered with fine setules. Caudal ramus wider than long, without conspicuous spinular ornamentation; with at least six setae, setae IV–V typically inflated at base in ♀.

Antennule ♀ slender and typically 8-segmented (occasionally 9-segmented), with aesthetascs on segments 4 and 8 (or 9). Antennule ♂ haplocer and presumably 10-segmented; with geniculation between segments 6 and 7, and four segments distal to geniculation; segment 5 swollen and with aesthetasc; segmental homologies in ♂: I, II– VIII, IX – XII, XIII, XIV – XVIII, XIX – XX, XXI – XXII, XXIII, XXIV – XXV, XXVI – XXVIII. Antenna not sexually dimorphic; allobasis completely fused or partially divided, with endopodal pinnate seta on abexopodal margin; exopod 2-segmented, proximal segment with two setae, distal segment with 1–2 lateral and three apical elements; free endopod with two penicillate elements. Mandible with 2 elements on basis; endopod with two lateral and 3–4 apical setae; exopod 1-segmented, with two setae. Maxillulary coxal epipodite and maxilla unconfirmed. Maxilliped with 0–1 seta(e) on syncoxa; basis with one seta on palmar margin; endopod represented by claw with unconfirmed number of accessory setae.

P1 inner basal spine not sexually dimorphic. P1 exopod 3-segmented; exp-2 elongate and much longer than others, with inner seta; exp-3 with two penicillate spines, a geniculate seta or additional penicillate spine, and one non-geniculate seta. P1 endopod 2-segmented; enp-1 longer than exopod, with short, proximally inserted, pinnate inner seta, inner segment margin without area of reduced chitinization; enp-2 with one naked minute seta and two penicillate claws. P2–P4 rami typically 3-segmented, P2–P3 endopods ♀ occasionally 2-segmented (Pe. penicillata sp. nov.); inner seta of P2–P4 exp-1 reduced in size. P3 endopod ♂ 3-segmented; enp-3 with spinous apophysis and no inner setae. P4 endopod ♂ occasionally without inner setae on enp-3 [1.1.021; in Pe. penicillata sp. nov.]. Armature formula of P2–P4 as follows:

P 5 ♀ endopodal lobe with five setae; inner margin without series of transverse striae. P 5 ♀ exopod elongate, with six elements. P 5 ♂ endopodal lobe with two elements, outer one typically shortest; exopod 1-segmented, with seven elements. P6 unconfirmed in both sexes.

Etymology. The generic name is derived from the Latin penicillus, meaning paintbrush, and the Greek suffix -caris, meaning shrimp, and refers to the presence of penicillate spines on the antennary endopod and both rami of the first swimming leg. Gender: feminine.

Type species. Thalestris pectinimana Car, 1884 = Penicillicaris pectinimana (Car, 1884) comb. nov. (by original designation herein).

Other species. P. maldivensis sp. nov.; P. penicillata sp. nov.; P. sewelli sp. nov.

Species inquirendae. Microthalestris forficula sensu Scott (1894a); M. littoralis Sars, 1911 sensu Brian (1921); M. littoralis Sars, 1911 f. scotti sensu Sewell (1940).