Peltidium nayarit Suárez-Morales & Jarquín-González 2013

Female: Body (Fig. 2A) broad, dorsoventrally flattened, arched along longitudinal axis. Cephalosome accounting for about half the body length, with its greatest width at first pedigerous somite, behind which the body gradually tapers posteriorly. Epimera of genital somite and preceding somite pointed and backwardly directed. Length of holotype: 1.03 mm measured from tip of rostrum to posterior margin of anal somite. Length range of type females from 0.93 mm to 1.05 mm, average length 0.96 mm, n=16. Rostrum fused to cephalosome, broad, downwardly directed. Cephalosome with a few small, sparsely distributed sensilla on lateral margins (Fig. 2A), posterior margin smooth. Succeeding prosomites, bearing legs 2-4, with flat, laterally expanded subtriangular margins ornamented with a mixed pattern of long and minute spinules (detail in Fig. 2A). First urosomite, bearing leg 5, slightly longer than succeeding genital double-somite; posterior margin of genital double-somite smooth. Anal somite with rounded posterior margin; somite naked in dorsal view, but with a row of long setae along ventral margin (Fig. 3B). Anal area moderately deep, with inner rows of short setules along margin of anal operculum. Caudal rami cylindrical, about twice as long as wide, with 7 setae. Middle caudal apical seta (V) longest. Dorsal seta (VII) about half as long as ramus (Fig. 3C). Antennule (Fig. 2B) 7-segmented; first segment slightly longer than second, ornamented with distal row of spinules. Armature of antennulary segments (s=setae, ae=aesthetasc) as: 1(1), 2(10s), 3(6s), 4(3s+2ae), 5(1s), 6(2s), 7(9s+1ae). Aesthetasc on fourth segment long, about 70% of antennule length. Antenna (Fig. 2C). Coxa small, Allobasis with short abexopodal seta and longitudinal patch of spinules on outer margin. Exopod two-segmented, elongated, first segment with short slender seta, second segment bearing three setae distally, distal margin with row of short spinules. One exopodal seta modified, with regular pectinate ornamentation along both margins (see detail in Fig. 2C). Free endopodal segment with outer row of long spinules, armed with one spine and two lateral setae plus seven distal setal elements, four of them being articulated stout setae. Mandible (Fig. 2D) short, tapering distally. Gnathobasis with narrow diastema, armed with 5-6 monocuspidate teeth, plus stout dorsal seta fused to gnathobasis, ornamented with row of short setules. Mandibular palp small, represented by a subrectangular coxa-basis segment and a single-segmented endopod armed with an inner row of spinules, six terminal setae plus a single outer seta. Maxillule (Fig. 2E). Praecoxal arthrite armed with eight teeth and one distal short seta. Coxa and basis fused, indistinguishable, with three terminal setae. Endopodite represented by one seta. Exopodite one-segmented, with two setae. Maxilla (Fig. 2F). Syncoxa robust, short, with two endites, the proximal small and bearing one broad seta, distal endite cylindrical, armed with two subequal, pinnate setae; allobasis forming a strong terminal claw and with one inner basal seta, one outer basal seta and two subequal outer endopodal setae. Maxilliped (Fig. 3A) subchelate. Coxa and basis elongate. Basis with smooth surface, bearing a well-developed seta, as depicted. First endopodal segment robust, ornamented with single row of spinules and large patch of spinules, as shown. Endopodal claw slender, slightly curved, about 1.3 times as long as basis, with single accompanying seta. Leg 1 (Fig. 3D). Coxa elongate, ornamented with single row of small spinules on inner and outer margins, plus single short seta on inner middle part of segment. Basis wide, inner margin and part of outer margin ornamented with spinules. Inner distal basipodal seta reaching distal margin of first endopodal segment. Outer basipodal seta reaching distal end of basis. Exopod three-segmented, second exopodal segment longest, about 1.5 times as long as first segment, with patch of minute spinules on outer distal margin. Two exopodal claws on distal position of third exopodal segment; outer claw half as long as inner claw. Endopod two-segmented, shorter than exopod. Endopodal segments wide, globose (sensu Wells 2007), ornamented with rows of short setules along the inner and outer margins. Terminal elements include a spine ornamented with distal row of minute spinules and two equally long slender setae. Leg 2 (Fig. 4A). Coxa small, basis transversely elongated. Basis with outer seta. Endopod three-segmented, longer than exopod, exopod reaching midlength of third endopodal segment. Exopod three-segmented, with spinules on outer margins of third segment and spinules at insertion of spines on first and second segments. Leg 3 (Fig. 4B). Coxa, basis, and relative length of endopodal and exopodal rami as in leg 2. Endopod and exopod three-segmented. Leg 4 (Fig. 4C). Coxa and basis as in leg 3. Exopod three-segmented, third segment with 8 setal elements. Insertion points of exopodal spines and outer margins of second and third exopodal segments with rows of spinules. Endopod three-segmented, slightly longer than exopod, outer margins of segments ornamented with rows of short spinules. Armature of swimming legs 1-4 as in Table 1. Leg 5 (Fig. 3E) exopod and baseoendopod separated. Baseoendopod bearing single inner seta. External seta long, borne on elongate cylindrical lobe of baseoendopod reaching half the length of exopodal lobe. Exopodite slender, with 5 setal elements (I-V) (sensu Wells 2007), two inserted on inner margin (I, II), three (III-V) distal. Elements I-III represented by stout, distally pinnate setae, elements IV and V represented by equally long slender setae. Male: Unknown. Armature of swimming legs 1-4 (spines in Roman numerals, setae in Arabic) of Peltidium nayarit sp. n. Sequence follows external to internal positions. basis endopod exopod leg 1 1-1 0-I; 2,I 1-0;1-1; 1,II leg 2 1-0 0-1;0-2;II,1,2 I-0;I-1;III,I,1,2 leg 3 1-0 0-1;0-2;II,1,2 I-0;I-1;III,1,2 leg 4 1-0 0-1;0,2;2,2 I-1; I-1; III,I,1,3