Paraleptomesochra Wells, 1967

Huys, Rony & Mu, Fanghong, 2021, Johnwellsia, a new intertidal genus of Parastenheliidae (Copepoda, Harpacticoida) from the Taiwan Strait, China, including a review of the family and key to genera, Zootaxa 5051 (1), pp. 236-318 : 288-289

Paraleptomesochra Wells, 1967

The justification for the proposal of this genus ( Wells 1967: 300) was based exclusively on the 2-segmented condition of the P1 exopod in the type species P. minima Wells, 1967 . Additional apomorphic character states shared with its congener, P. wellsi Rao, 1972 , included the 8-segmented condition of the ♀ antennule, the presence of a modified distal element (“… expanded, bifid, hyaline structure…”) on exp-2 of the antenna, proximal endopodal segment of antenna without allobasis, reduction of the mandibular exopod (absent or represented by short seta), mandibular basis with only two setae; maxilliped with reduced armature (at most one seta on syncoxa, none on basis), inner basal spine of ♂ P1 modified (with recurved tip), various reductions in the armature of P2–P4 ( Tables 1–2 ), P5 endopodal lobe ♀ with only three elements, and P5 exopod ♂ with only four elements. The modification of the inner basal spine of P1 is shared with Psammoleptomesochra and Foweya ; however, in members of the latter genus the inner spine is not recurved but typically straight, bifid apically, and carrying a flagellate extension at its tip (cf. Gee 2006: Figs 10D, 13A). It is conceivable that, within the Parastenheliidae , Paraleptomesochra is most closely related to Psammoleptomesochra ( Mielke 1994a) .

Both species of Paraleptomesochra are small-sized (♀: 274–336 μm; ♂: 276–315 μm) and exclusively known from sandy beaches. Rao (1980: 166) listed a species under the name “ Paraleptomesochra africana (Kunz) ” but this is a lapsus calami referring to Praeleptomesochra africana ( Kunz, 1951) (family Ameiridae ) (cf. Dev Roy & Venkataraman 2018). Finally, as yet unidentified species of Paraleptomesochra have been reported from shallow depths off the coast of northwestern Florida ( Suderman & Thistle 1998) and from Heron Reef, Great Barrier Reef ( Iwasaki 1994).

Diagnosis. Parastenheliidae . Sexual dimorphism in antennule, P1 inner basal spine, P5–P6 and urosomal segmentation. Body cylindrical, short; posterior margin of prosomites and urosomites (except anal somite) with denticulodigitate hyaline frills. Rostrum fused at base, small, pointed. Anal operculum semicircular, bordered with fine setules. Caudal ramus about as long as wide, with dorsal spinular row; with at least six setae, setae IV– V not basally inflated in ♀ .

Antennule ♀ elongate and 8-segmented in ♀, segment 1 not elongate, segments 6–7 shortest, with aesthetascs on segments 4 and 8. Antennule ♂ haplocer with three segments distal to geniculation; segmentation partly unconfirmed but probably at least 9-segmented with segmental homologies as follows: I, II– VIII, IX – XII, XIII, XIV – XVIII, XIX – XX, XXI – XXIII, XXIV – XXV, XXVI – XXVIII.Antenna not sexually dimorphic; proximal endopodal segment completely separated from basis, without seta on abexopodal margin; exopod 2-segmented, proximal segment with two setae, distal segment with 1–2 lateral and two apical elements (one of which enlarged, hyaline and bifid); distal endopodal segment without penicillate elements. Mandible with two elements on basis; endopodal armature unconfirmed; exopod absent or represented by a short seta. Maxillulary coxal epipodite unconfirmed. Maxilla with three endites on syncoxa; endopod unconfirmed. Maxilliped with 0–1 seta€ on syncoxa; basis without armature on palmar margin; endopod represented by claw without accessory setae .

P1 inner basal spine sexually dimorphic (recurved in ♂). P1 exopod 2-segmented; exp-2 slightly longer than exp-1, with two distal and two outer pinnate elements. P1 endopod 2-segmented; enp-1 elongate, at most slightly longer than exopod, with short inner seta, segment margins probably without area of reduced chitinization; enp-2 very small, with one outer distal spine and one inner distal geniculate seta. P2–P4 rami 3-segmented; enp-2 and -3 without inner seta(e); inner seta of P2–P3 exp-1 reduced in size, absent in P4. P2–P3 endopods ♂ without sexual dimorphism. Armature formula of P2–P4 as follows:

P 5 ♀ endopodal lobe with three setae (one inner, two distal); inner margin without transverse striae. P 5 ♀ exopod ovate, with six elements. P 5 ♂ endopodal lobe with 1–2 elements; exopod 1-segmented, with four elements. Vestigial P 6 ♀ represented by one seta. P 6 ♂ with two setae.

Type species. Paraleptomesochra minima Wells, 1967 (by original designation).

Other species. P. wellsi Rao, 1972 .

Notes. Both Wells (1967) and Rao (1972) state that the rostrum is fused to the cephalothorax which, if correct, would be a unique condition in the family. The segmental homologies of the haplocer male antennule are unconfirmed although Rao (1972) describes it as 7-segmented with the sixth segment partially divided by an indistinct suture in P. wellsi . The description of the armature on the caudal ramus (with four setae in P. minima , five in P. wellsi ) is almost certainly incorrect. The presence/absence of the coxal epipodite of the maxillule is unconfirmed since neither Wells (1967) nor Rao (1972) describe the appendage. Similarly, it is not clear whether the maxillary endopod is expressed or the maxillipedal claw has any accessory elements.