Aeginecta longicauda, Pessacq, 2018

Aeginecta longicauda View in CoL n. sp.

( Fig. 1 View Figure 1 )

Type material. Holotype, male: Argentina. Chubut Province: Bajo de los Huesos: temporary pool, ~ 5 m asl (43°09′14″ S 64°46′13″ W), about 45 km northeast of Trelew city; 7 October 2003; M. Archangelsky legitor. Deposited at Museo de La Plata (La Plata, Buenos Aires province, Argentina): MLP-Cr 27304 GoogleMaps Paratype, in collections of DCR.

Type locality. ( Fig. 2 View Figure 2 ) Aeginecta longicauda n. sp. is only known from the type locality, a single pool at Bajo de los Huesos, Chubut Province, Argentina. Bajo de los Huesos ephemeral pond lies within a xeromorphic shrubland region, which has very sparse and low vegetation; annual rainfall in this region is about 200 mm. Morrone (2006) places it in the biogeographic province of Central Patagonia (Patagonian subregion, Andean region), and according to Cabrera (1976) it is located in the phytogeographic province of Monte (Chaqueño domain, Neotropical region).

Diagnosis. As for the genus.

Description. Length of preserved material:22.0 mm from apex of head to apex of telson.

Male. ( Fig. 1A View Figure 1 ) Head rounded, with frons lateral margins projecting over eye peduncle and base of compound eye. Anterior surface of head, frontal appendage and antennae II flattened, with integument slightly thickened, and expanded laterally.

Frontal appendage short, transverse, flattened, 60% as long as antenna II proximal antennomere. Frontal appendage covered in rows of fine denticulate spines, bilobed, with each lobe less than one fifth the total appendage length.Frontal appendage fitting into a recess formed by the antennal II proximal antennomeres.

Compound eye reduced. Eye diameter 1.6 times longer than peduncle. Eye peduncle extremely short, smooth, conical, expanding distally to compound eye.

Antenna like appendages absent.

Antenna I filiform, approximately 70% length of antenna II proximal antennomere.

Antenna II proximal antennomere rectangular, as long as wide in anterior view, with lateral margin broadly projecting. Posteriolateral corner triangular, projecting dorsally in front of compound eye. Anterior, anteriomedial and anteriolateral surfaces with transverse rugae, which are more pronounced anteriomedially. Proximomedial margin excavate, forming a cavity in which the antennal appendage lies.

Antenna II distal antennomere 2.4 times longer than proximal antennomere, broadly arcuate, curving medially approximately 120 degrees from normal, flattened anterioposteriorly with a posterior and an anterior longitudinal groove.

Labrum broad, smooth, with posteriolateral corners rounded and directed dorsally. Labrum apex flattened laterally, bent ventrally approximately 80 degrees from normal, and covered in fine denticles.

Mandible large, transverse, lacking an incisor.

Maxilla I unobserved.

Maxilla II hemispherical, bearing a single spine.

Thoracic segments smooth, unadorned.

Thoracopods serially homologous. Thoracopod V ( Fig. 1B View Figure 1 ) with endites flexible as one unit, able to articulate in the posterior direction, capable of folding back against the limb surface. All endites thick, each endite at least as thick as 0.5 times the endite length, each with the distal end bearing a well separated anterior and a posterior margin, both margins with setae and/ or spines. Endite I+II lobiform, broadly rounded, ~0.5 times as thick as long, with anterior margin bearing a single long, sinuate spine, directed dorsally, ~0.4 times as long as endite is broad. Endite I + II with posterior margin bearing a dorsal short transverse row of mounds, each tipped with a simple seta, medial and ventromedial margin with spiniform setae, bearing elongated filiform apices, directed dorsally, ~2.3 times as long as spiniform base.

Endite III lobiform, ~0.4 times as broad as endite I+II, with anterior margin bearing a single long, straight spine, directed dorsally. Posterior edge margined with spiniform setae, bearing elongated filiform apices directed dorsally, ~2.3 times as long as spiniform base.

Endite IV angular, sloping wider from dorsal to ventral end, subequal in width to endite III. Anterior edge margined with spines directed medially, each bearing a short setaform apex, ~0.4 times the length of the spiniform base. Posterior margin with a short apical row of spiniform setae, bearing elongated filiform apices directed dorsally, ~2.3 times as long as spiniform base.

Endite V angular, sloping wider from dorsal to ventral end, width ~0.7 width of endite III. Anterior edge margined with spines directed medially, each bearing a short setaform apex, ~0.4 times the length of the spiniform base. Posterior margin with a short apical row of spiniform setae, bearing elongated filiform apices directed dorsally, ~2.3 times as long as spiniform base.

Endite VI angular, sloping wider from dorsal to ventral end, width ~0.8 width of endite V. Anterior edge margined with spines directed medially, each bearing a short setaform apex, ~0.4 times the length of the spiniform base. Posterior margin with a short apical row of spiniform setae, bearing elongated filiform apices directed dorsally, ~2.3 times as long as spiniform base.

Endopodite broadly ovate, medial edge and apex margined with pectinate spines, ventral and lateral edge margined with simple setae.

Exopodite ovate, dwarfed by endopodite, lying on posterior endopodite surface. Medial margin entire, lateral margin weakly serrate, each serration tipped by a stout simple seta. Medial edge margined with filiform simple setae.

Epipodite reniform, very large, nearly as long as entire limb, lacking setae or spines, weakly serrate. Praeepipodite lying dorsoanterior to epipodite, subequal in size to exopodite, reniform, lacking marginal setae or spines, very weakly serrate.

First genital segment(thoracic segment XII)( Fig.1C View Figure 1 ) tumid, with several ventral folds, overlapping gonopod bases anteriorly, and laying over base of second genital segment (thoracic segment XIII) on lateral sides of gonopods. First thoracic segment transversely ridged dorsally, seminal vesicles dorsally looped. Gonopod ( Fig. 1D, E View Figure 1 ) basal portions close set to medial line, bulbous, smooth, directed ventrally, directly away from body axis. Gonopod proximal portion with an apical, transverse cleft, enclosing eversible distal portion. Proximal portion distally, posterior to cleft, with transverse rows of fine denticles. Distal eversible portion as for genus description.

Abdominal segments subcylindrical, smooth, unadorned.

Telson ( Fig. 1F View Figure 1 ) short, flattened dorsoventrally, and subrectangular in ventral view. Cercopods elongate, nearly 70% as long as abdomen, dorsoventrally flattened, laterally margined with stiff spines, proximal most spines arcing posteriorly, distal most spines directed posteriorly. Cercopod medial edge margined with fine filiform setae proximally, then in proximal third with spines directed posteriorly.