Pseudoleptomesochrella Lang 1965

Genus Pseudoleptomesochrella Lang, 1965

Diagnosis (amended). Ameiridae. Body cylindrical and slender, without clear demarcation between prosome and urosome; integument smooth, not strongly chitinized. Hyaline frills of cephalothorax and somites bearing P2–P5 usually plain; those of abdominal somites plain or digitate with rectangular lappets. Female genital and first abdominal somites completely fused to form genital double-somite; original segmentation sometimes marked by dorsolateral, transverse internal ribs. Anal operculum smooth (spinulose in P. pontica?). Caudal ramus conical, short; with 7 setae. Sexual dimorphism in body size, antennule, P1 (inner basal spine), P4 endopod, P5, P6, and in genital segmentation.

Rostrum small, not demarcated at base. Antennule slender and elongate; setae smooth; 8-segmented in Ψ (7-segmented in P. i n c e r t a?), with aesthetasc on segments 4 (extremely long, longer than antennule) and 8; 11- segmented and haplocer in ɗ, with geniculation between segments 8 and 9 and aesthetasc on segments 5 and 11. Antenna with basis and proximal endopod segment completely or incompletely separated; endopod with 2 lateral and 6 distal elements (longest geniculate seta fused at base to naked seta). Antennary exopod 2-segmented; armature formula [1,2]; exp-1 without ornamentation; exp-2 minute, with apical seta longer than lateral one. Mandibular palp uniramous, 2-segmented, comprising basis and 1-segmented endopod; basis with 1 pectinate and 2 pinnate setae; endopod with 2 lateral and 3 apical setae. Maxillule with 1 element on coxal endite; basis and rami (endopod; exopod probably absent) partly fused; represented by total of 7 setae. Maxillary syncoxa with 2 well developed endites, proximal one drawn out into apically serrate element and with 1 flaccid plumose seta; distal endite with 1 pinnate and 2 plumose setae; allobasis drawn out into a claw and with pinnate spine; endopod minute, unisetose. Maxilliped subchelate; syncoxa with 1 seta; endopod represented by minutely pinnate claw with 1 accessory seta.

P1–P4 with 3-segmented exopods and 2- (P2–P4) or 3-segmented (P1) endopods. P1 exopod without inner seta on exp-2; exp-3 with 2–3 outer spines and 2 geniculate setae distally. P1 endopod prehensile, with enp-1 at least as long as enp-2 and -3 combined, but shorter than exopod; inner seta of enp-2 short. Inner basal spine of P1 modified in ɗ, forming a strong recurved hook. P2–P4 with inner seta on exp-1, exp-2 and enp-1. P4 endopod ɗ slightly modified; inner element on enp-2 reduced in size; distal spine sometimes shorter and recurved (Atlantic complex). Armature formula P1–P4 as follows:

* Note that inner distal seta on exp-3 is thin and minute P5 with separate baseoendopod and exopod in both sexes; baseoendopods fused medially in ɗ; Ψ with 3– 4 setae on baseoendopod; exopod semicircular or ovate, with 3–4 setae; ɗ with 1–3 setae on baseoendopod and 3–4 setae on exopod. Female genital field with large copulatory pore leading via chitinized copulatory duct to median seminal receptacle; gonopores covered by common genital operculum derived from P6 with 1 plumose seta and 1 spinous process on either side. Male P6 slightly asymmetrical, with 3 simple setae, of which outer one longest.

Type-species: Nitocrella halophila Noodt, 1952 = Pseudoleptomesochrella halophila (Noodt, 1952) [by original designation].

Other species: P. incerta (Chappuis & Delamare Deboutteville, 1956); P. m a r i n a (Chappuis & Rouch, 1961); P. b i s e t o s a Lindgren, 1975; P. venezolana Mielke, 1995.

Species inquirenda: P. pontica Apostolov, 1969