Birabenella, Grismado, 2010

Grismado, Cristian J., 2010, Description of Birabenella, a New Genus of Goblin Spiders from Argentina and Chile (Araneae: Oonopidae), American Museum Novitates 2010 (3693), pp. 1-24 : 3-7

Birabenella , new genus

TYPE SPECIES: Birabenella homonota , n. sp .

ETYMOLOGY: The generic name is in honor of the late Argentine arachnologist Max Birabén (1893–1977), who was the first to describe a species assigned here to this genus ( O. argentinus ), in recognition of his valuable contributions to the knowledge of the oonopids from Argentina. Gender feminine.

DIAGNOSIS: The putative synapomorphies proposed for Birabenella , new genus, are the unipectinate tarsal claws (figs. 6, 7–8, 10–11) and the stout and flattened setae on the dorsum of the abdomen (figs. 18, 26, 39, 54, 63). Other probable synapomorphies are the conspicuous ventral digitiform projection on the male palpal bulb (figs. 33, 49) and the strongly thickened anterior wall of the posterior diverticle in the female genitalia (figs. 35, 59, 68).

DESCRIPTION: Male (males of B. elqui and B. pizarroi are unknown): CEPHALOTHORAX: Carapace without any pattern, broadly oval in dorsal view, pars cephalica almost flat in lateral view, anteriorly narrowed to between 0.5 and 0.75 times its maximum width, with rounded posterolateral corners, posterolateral edge without pits, posterior margin not bulging below posterior rim, anterolateral corners without extension or projections, posterolateral surface without spikes, surface of pars cephalica strongly reticulate, sides also strongly reticulate, thorax without depressions, fovea absent, without radiating rows of pits; lateral margin straight, rebordered, without denticles; plumose setae near posterior margin of pars thoracica absent; nonmarginal pars thoracica setae needlelike; marginal setae needlelike. Clypeus margin unmodified, curved downwards in front view, vertical in lateral view, high, ALE separated from edge of carapace by their radius or more, median projection absent; setae present. Chilum absent. Eyes: six, well developed, all subequal, all eyes circular; posterior eye row recurved from above, straight from front; ALE separated by more than their diameter, ALE-PLE separated by ALE radius to ALE diameter, PME separated by less than their radius, PLE-PME separated by PME radius to PME diameter. Sternum as long as wide, uniform, not fused to carapace, median concavity absent, surface finely reticulate, without pits, microsculpture covering entire surface, sickle-shaped structures absent, anterior margin unmodified, posterior margin extending posteriorly beyond anterior edges of coxae IV as single extension, anterior corner unmodified, lateral margin without infracoxal grooves, distance between coxae approximately equal, extensions of precoxal triangles absent; setae sparse, dark, needlelike, evenly scattered, originating from surface, without hair tufts. Mouthparts: chelicerae straight, anterior face with the base slightly swollen; without teeth on both promargin and retromargin; without toothlike projections, directed medially, shape normal, without prominent basal process, tip unmodified; setae needlelike, evenly scattered; paturon inner margin with scattered setae, distal region unmodified, posterior surface unmodified, promargin unmodified, inner margin unmodified, laminate groove absent. Labium subpentagonal, elongate, not fused to sternum, anterior margin indented at middle, same as sternum in sclerotization. Endites strongly convergent, anterior tip with one strong, spinelike projection (as in fig. 47), distally not excavated, serrula present in single row, posteromedian part unmodified, same as sternum in sclerotization. ABDOMEN: ovoid, without long posterior extension, rounded posteriorly; dorsum soft portions white, without color pattern (a small, weakly sclerotized dorsal scutum is present in B. homonota ). Book lung covers large, round, without setae, anterolateral edge unmodified. Posterior spiracles connected by groove. Pedicel tube short, unmodified, scuto-pedicel region unmodified, scutum absent, but abdomen not extending anterior of pedicel, plumose hairs absent, matted setae on anterior ventral abdomen in pedicel area absent, cuticular outgrowths near pedicel absent. Epigastric scutum absent. Postepigastric scutum absent. Spinneret scutum absent. Supraanal scutum absent. Dorsum setae present, stout and flattened. Epigastric area setae uniform, needlelike. Postepigastric area setae present, needlelike. Dense patch of setae anterior to spinnerets absent. Colulus absent. LEGS: without color pattern; femur IV not thickened, same size as femora I– III, tibia I unmodified, tibia IV specialized hairs on ventral apex absent, tibia IV ventral scopula absent, metatarsi I and II mesoapical comb absent, metatarsi III and IV weak ventral scopula absent. Tarsi I to IV without inferior claw. Superior claws unipectinate. Leg spines present only in B. homonota . GENITALIA: Epigastric region with sperm pore not visible with light microscope; furrow without Ω-shaped insertions, without setae. Palp normal size, not strongly sclerotized, right and left palps symmetrical, proximal segments pale orange; embolus light, prolateral excavation absent; trochanter normal size, unmodified; femur normal size, two or more times as long as trochanter, without posteriorly rounded lateral dilation, attaching to patella basally; patella shorter than femur, not enlarged, without prolateral row of ridges, setae unmodified; tibia trichobothria not examined; cymbium pale orange, ovoid in dorsal view, not fused with bulb, not extending beyond distal tip of bulb, plumose and stout setae absent, without distal patch of setae; bulb pale orange, 1 to 1.5 times as long as cymbium, stout, tapering apically, with a large, oval opening from which the embolus and accessory membranes arise. The seminal duct is visible with clarification (figs. 33, 49).

Female (females of B. argentina are unknown): As in males except as noted. CEPHALO- THORAX: Carapace surface of elevated portion of pars cephalica reticulate or smooth, sides strongly ( B. homonota ) to finely reticulate ( B. elqui and B. pizarroi ). Clypeus setae dark, needlelike. Sternum surface reticulate ( B. homonota ) or smooth ( B. elqui and B. pizarroi ). Labium with 1 or 2 setae on anterior margin, subdistal portion with unmodified setae. Endites anteromedian tip unmodified. Female palp claws absent; spines absent; tarsus unmodified, patella without prolateral row of ridges. LEGS: patella plus tibia I near as long as carapace. Tarsal proclaws and retroclaws inner face striate (at least in B. homonota and B. pizarroi ). Tarsal organ with two or three sensilla visible (at least in legs I in B. homonota and B. pizarroi ). GENITALIA: anterior diverticle duct shaped, with thin lumen, associated with a transverse sclerite (visible through cuticle, with at least two pairs of muscles attached). Anterior to the transverse sclerite there is an anterior process with a transversely widened structure. Posterior receptaculum with the anterior wall strongly sclerotized, with internal ducts variable shape and length (see below, under species descriptions).