Ambulantactus, Monjaraz-Ruedas & Prendini & Francke, 2019

Monjaraz-Ruedas, Rodrigo, Prendini, Lorenzo & Francke, Oscar F., 2019, Systematics Of The Short-Tailed Whipscorpion Genus Stenochrus Chamberlin, 1922 (Schizomida: Hubbardiidae), With Descriptions Of Six New Genera And Five New Species, Bulletin of the American Museum of Natural History 2019 (435), pp. 1-93 : 18-22

Ambulantactus , gen. nov.

Figures 1 , 6, 7A, B, 8A, 10D, 12C, 13A, B, 14C, 15A–C, 16A–F, 17A–C; tables 1, 2, 5

TYPE SPECIES: Ambulantactus montielae , sp. nov., type species, here designated.

DIAGNOSIS: Ambulantactus , gen. nov., may be separated from other hubbardiid genera by the following combination of characters. Propeltidium anterior process with two anterior setae (one posterior to the other) and three pairs of dorsosubmedian setae (fig. 11A); corneate eyes absent. Metapeltidium entire. Tegument without clavate setae. Cheliceral movable finger smooth; single guard tooth at end of serrula; setal group G3 with G3-3 setae situated anteriorly (fig. 13A, B). Pedipalps homeomorphic; trochanter with mesal spur, apical process small and acute (fig. 7A, B); femur Fv 1 and Fv 2 setae acuminate, Fvr 1–3 setae present; patella with three acuminate Pe setae and five feathered Pm setae; tibia setal formula 4-3-5 (Ter-Tmr- Tir) (fig. 14A). Leg IV femur anterodorsal margin produced at ca. 90° angle. Opisthosomal tergite II with one pair of setae (Dm). Opisthosomal segments IX–XII not elongated; XII (♂) without posterodorsal process. Pygidial flagellum (♂) dorsoventrally compressed, deltoid, with pair of posterodorsal depressions, fused posteriorly (fig. 16A–F); flagellum (♀) with two annuli (fig. 17A– C). Spermathecae (♀) with two pairs of lobes; lateral lobes slightly smaller than (ca. 3/4 the length) but similar in width to median lobes; both pairs of lobes linear, with apex directed vertically, unsclerotized apically (figs. 8A, 10D), and without bulbs; median lobe bases posterior to lateral lobe bases (fig. 10D), with duct openings; chitinized arch inverse arch shaped, without anterior branch, with lateral tips tapering; gonopod wide and short.

COMPARISONS: Species of Ambulantactus , gen. nov., are most similar morphologically to species of Schizophyxia , gen. nov. Both genera possess a pair of posterodorsal depressions on the male pygidial flagellum, and the lobes of female sper- mathecae are of similar length. The two genera differ in the shape of the male flagellum, which is deltoid in Ambulantactus , but spear shaped in Schizophyxia . Additionally, the chitinized arch of the female spermathecae is inverse arch shaped in Ambulantactus , but U-shaped in Schizophyxia . Finally, the pedipalp tibia setal formula is 4- 3-5 in Ambulantactus and 3- 3-4 in Schizophyxia .

Species of Ambulantactus resemble species of Heteroschizomus , stat. rev., and Nahual , gen. nov., in the linear median and lateral lobes of the female spermathecae. However, the lobes are considerably larger in Ambulantactus than in the other genera. Furthermore, the lobes are smooth in Ambulantactus but apically sclerotized in Nahual , and cylindrical in Ambulantactus but conical in Heteroschizomus .

Species of Ambulantactus also resemble species of Olmecazomus , nom. nov., especially Olmecazomus brujo , comb. nov., in the shape of the female spermathecae, and the posterior depressions of the male flagellum. However, Ambulantactus are considerably smaller than Olmecazomus and pedipalp setae Fv 1 and Fv 2 are acuminate setiform in Ambulantactus , but form spiniform setiferous tubercles in Olmecazomus .

ETYMOLOGY: The genus name is a compound word derived from the Latin words ambulans, meaning “walking,” and tactus, meaning “touch,” and refers to the distinctive walking gait of schizomids. It is neuter in gender.

INCLUDED SPECIES: Ambulantactus aquismon , sp. nov.; Ambulantactus davisi ( Gertsch, 1940) , comb. nov.; Ambulantactus montielae , sp. nov.

DISTRIBUTION: The known species of Ambulantactus , gen. nov., are endemic to Mexico, where they display a disjunct distribution across three states (fig. 1). Ambulantactus montielae , sp. nov., occurs in Morelos, A. aquismon , sp. nov., in San Luis Potosí, and A. davisi , comb. nov., in Tamaulipas. This distribution resembles the distributions of some taxa in family Protoschizomidae , with species occurring in the north and south of Mexico, on either side of the Mexican Transvolcanic Belt. Ambulantactus is probably distributed along the entire length of the Sierra Madre Oriental.

NATURAL HISTORY: The species of Ambulantactus , gen. nov., are epigean, occurring under rocks in rainforest and tropical dry forest.

REMARKS: Species of Ambulantactus , gen. nov., closely resemble some species of Schizophyxia , gen. nov., in the general shape of the female spermathecae. Ambulantactus montielae , sp. nov., was designated as the type species of the genus because it is the only species in which the female is known. Despite the absence of females of A. aquismon , sp. nov., and A. davisi , comb. nov., and the absence of molecular data for A. davisi , the two species grouped with A. montielae in the simultaneous analysis (fig. 6).

Figures

FIG. 1. Map of central Mexico, plotting known locality records for the short-tailed whipscorpion genus Ambulantactus, gen. nov. (squares), and the species recently tranferred to Pacal Reddell and Cokendolpher, 1995 (circles) (Schizomida: Hubbardiidae Cook, 1899), based on data from museum collections and the literature.