Mastigoproctus mexicanus Butler, 1872

Barrales-Alcalá, Diego, 2018, Systematic Revision Of The Giant Vinegaroons Of The Mastigoproctus Giganteus Complex (Thelyphonida: Thelyphonidae) Of North America, Bulletin of the American Museum of Natural History 2018 (418), pp. 1-64 : 29-32

Mastigoproctus mexicanus Butler, 1872 ,

stat. nov.

Thelyphonus mexicanus Butler, 1872: 201 , fig. 1.

Thelyphonus (?) mexicanus: Tarnani, 1890: 538 .

Mastigoproctus giganteus mexicanus: Pocock, 1902a: 48 ; Mello-Leitão, 1931: 27; Harvey, 2003: 67; Barrales-Alcalá et al., 2016: 26, 46 (part); McMonigle, 2013: 100, fig. unnumbered, 100 (part).

TYPE MATERIAL: MEXICO: holotype ♂ (Natural History Museum, London) [photographs examined].

DIAGNOSIS: Mastigoproctus mexicanus resembles M. vandevenderi , sp. nov., from which it differs as follows. Adult M. mexicanus are densely setose and reddish in color whereas adult M. vandevenderi are sparsely setose and brownish. Spine S3 is longer than the other spines on the prodorsal margin of the pedipalp trochanter of the adult male in M. mexicanus whereas spines S3 and S4 are equal in M. vandevenderi . The tubercles on the retrolateral surface of the pedipalp femur are straight and digitiform in M. mexicanus but curved and cup shaped in M. vandevenderi . The seminal receptacles of the spermathecae are swollen, obovate and anteriorly directed in M. mexicanus but narrow, triangular, and posteriorly directed in M. vandevenderi .

DESCRIPTION: The following description is based on one male and two females.

Total length: Maximum length from anterior margin of carapace to posterior margin of opisthosomal segment XII (pygidium) in adult specimens 55.0 mm (♂) and 50.1 mm (♀) (table 2).

Color: Carapace reddish, anterior margin reddish brown, lateral margins dark reddish brown, median ocular tubercle dark reddish brown. Tergites I–IX reddish, posterior and lateral margins dark reddish. Sternites I and II reddish; III–IX and pygidium reddish brown. Pedipalp trochanter, femur, patella and tibia, dark reddish brown, mesal surfaces with several dark reddish macrosetae; patellar apophysis, fixed finger and basitarsus blackish, with reddish macrosetae. Legs I–IV reddish brown; II– IV coxae, ventral surfaces reddish.

Carapace: Epistoma visible in dorsal aspect. Pair of strongly developed carinae anterolaterally, extending from lateral ocelli to two-thirds the distance to median ocular tubercle (fig. 10B). Three pairs of lateral ocelli with accessory translucent eyespot situated between anterior and posterior ocelli; anterior ocelli almost equal to median and posterior ocelli; anterior two pairs slightly separated from posterior pair by tubercle, distance between median and posterior ocelli 6× distance between anterior and median ocelli. Median ocular tubercle smooth, situated in anterior 10% of carapace (table 2); distance between ocelli almost 1.5× ocular diameter. Carapace surfaces granular, tuberculate mediolaterally, and with sclerotized crests between median ocular tubercle and anterior margin. Posterior fovea present, distinct.

Chelicerae: Retrolateral surface with stridulatory surface (plectrum), comprising approximately 30 short, stout (ca. 7× or 8× longer than wide), anteroventrally directed spiniform macrosetae (figs. 4D, 5D); mesal surface with few short, stout, anteroventrally directed spiniform macrosetae.

Pedipalps: Cuticle punctate and tuberculate, with cristulae. Coxa, retrolateral surface with cristulae; ventral surface rugose; coxal apophysis with one terminal spine; prodorsal surface with long, retroventrally directed macrosetae inserted in cris- tulae, forming stridulatory surface (pars stridens) (fig. 6D). Trochanter longer than wide (♂), or subequal (♀) ; retrodorsal surface tuberculate with long, straight cristulae (♂) or punctate (♀); prodorsal margin with five terminal spines (S1–S5) and one subterminal accessory spine ( AS), varying in size such that S3> S4 ≥ S2 ≥ S5> S1> AS (♂; fig. 7E) or S4> S5 ≥ S3> S2> S1> AS (♀; fig. 7F) ; space between S4 and S3 subequal to length of S3 (♂) or subequal to space between S4 and S5 (♀); prolateral surface with several spiniform tubercles and reddish macrosetae (♂); proventral margin with two spines (♂). Femur laterally compressed (♂) or terete (♀), 2× (♀) to 2.5× (♂) longer than wide (table 2); prolateral surface with two spines, one prodorsal, short, sharply pointed, the other proventral, blunt, length one-fifth femur width (♂; fig. 9E) or short, sharply pointed, and apical (♀); retrolateral surface with sharply pointed digitiform tubercles (♂) or short tubercles proximally (♀). Patella slightly longer (♂) or shorter (♀) than tibia (table 2); prolateral surface with several reddish macrosetae, one spine (♂) or one to two spines (♀) situated distally on proventral margin; one vestigial (♂) or distinct (♀) spine at base of patellar apophysis; retrolateral surface tuberculate proximally. Patellar apophysis elongated, almost one-quarter carapace length, smooth and slender (♂) or shorter and robust (♀) ; prolateral margin with row of blunt, pointed denticles; retrolateral margin smooth (♂) or denticulate (♀), with subterminal macrosetae. Tibia laterally compressed; prodorsal surface with sparse row of denticles; prolateral surface sparsely punctate, with reddish macrosetae; proventral margin with two spines distally; fixed finger, dorsal and ventral margins each with row of denticles. Basitarsus (movable finger), dorsal and ventral margins each with serrate row of denticles; prolateral surface with several reddish macrosetae; apex bifid (♂).

Legs: Leg I, basitarsal and telotarsal tarsomeres I–VII gradually decreasing in length, with tarsomere I longest, tarsomere VIII four-fifths length of tarsomere I. Legs I–III coxae, lateral surfaces and IV, dorsal surface each with setose spiniform tubercles. Legs I–IV trochanters, dorsal and lateral sur- faces with setose spiniform tubercles; femora dorsal and ventral surfaces with setose spiniform tubercles, situated proximally on I, II–IV, retroventral surfaces each with setose spiniform tubercle terminally, with macroseta inserted subterminally; tibiae each with one ventrodistal spur; basitarsi each with two ventrodistal spurs. Leg I tibia with two trichobothria distally; legs II–IV tibiae each with one trichobothrium distally.

Opisthosoma: Tergites almost smooth with few dark macrosetae; I without median longitudinal suture; II with median longitudinal suture, extending from anterior margin to midsegment; tergites III–IX undivided; X (first segment of pygidium) with distinct lateral longitudinal sutures (pleuron); XII with pair of lateral, ovobate ommatoids posterolaterally. Sternite II (genital) with pair of V-shaped (♂) or lanceolate (♀) depressions submedially, posterolateral surfaces inflated (♂) or flat (♀), and posterior margin protruding markedly (♂) or slightly (♀) posteriorly into median lobe, emarginate medially and overlapping sclerotized area in space between sternites II and III (♀) ; III divided longitudinally (♂) or undivided (♀), linear (♂) or with pronounced emargination (♀) anteriorly, posterior margin with (♂) or without (♀) median bulge with patch of reddish macrosetae ; IV undivided longitudinally; V with (♂) or without (♀) patch of fine macrosetae medially ; VI –VIII surfaces smooth, with few dark macrosetae (♂) ; IX surface smooth, asetose. Spermathecae seminal receptacles obovate, anteriorly directed (fig. 11E, F); spermathecal neck short, narrow; aperture of uterus curved, with medial notch; dorsal atrium pentagonal in dorsal aspect.

Sexual dimorphism: Adult males present several characters that differ from the females and immature stages. The pedipalps of the male are relatively elongated (fig. 9E), unlike the pedipalps of the female, which are shorter and more robust. A wider gap is present between spines S3 and S4 than between other spines on the prodorsal margin of the pedipalp trochanter in the male (fig. 7E, F) whereas all spines along the prodorsal margin are evenly spaced in the female. Long, digitiform tubercles are present on the retrolateral surface of the femur in the male, whereas short tubercles and cristulae are present on the retrolateral surface of the female. The retroventral spine on the pedipalp femur is short and situated proximally in the male, whereas it is longer and situated distally in the female. The patellar apophysis is slender and elongated in the male, whereas it is short and stout in the female. The posterolateral surfaces of sternite II are slightly inflated in the male, but flat in the female. Sternite III is not emarginate anteriorly and its posterior margin exhibits a posteromedian bulge with a patch of macrosetae in the male, whereas sternite III is conspicuously emarginate anteriorly, its posteromedian margin does not protrude, and a patch of macrosetae is absent in the female (fig. 15B, D).

ADDITIONAL MATERIAL EXAMINED: MEX- ICO: Aguascalientes: Municipio Calvillo: 3 km E Presa Alamitos, 21°44′06.468″N 102°41′51.108″W, 2,440 m, 24.vii.2012, D. Barrales, G. Contreras, O. Francke, and A. Valdez, oak forest, 1 ♂, 1 ♀, 1 subad. ♂, 9 juv. (CNAN [Ur57]).

DISTRIBUTION: Known only from the vicinity of Presa Alamitos, in the municipality of Calvillo, Aguascalientes, Mexico (fig. 2).

NATURAL HISTORY: Mastigoproctus mexicanus inhabits oak forest, at elevations of 2000–2400 m, with a temperature range of 18°–22° C and mean annual precipitation of 660 mm. Specimens were collected under large rocks, and it was not unusual to find juveniles and adults together under the same shelter. The species is fairly abundant in the area. No aggressive behavior was observed.