Ischnotelson, Lauren A. Esposito & Humberto Y. Yamaguti & Cláudio A. Souza & Ricardo Pinto-Da-Rocha & Lorenzo Prendini, 2017

Lauren A. Esposito, Humberto Y. Yamaguti, Cláudio A. Souza, Ricardo Pinto-Da-Rocha & Lorenzo Prendini, 2017, Systematic Revision of the Neotropical Club-Tailed Scorpions, Physoctonus, Rhopalurus, and Troglorhopalurus, Revalidation of Heteroctenus, and Descriptions of Two New Genera and Three New Species (Buthidae: Rhopalurusinae), Bulletin of the American Museum of Natural History 415, pp. 1-134 : 61-65

publication ID	https://doi.org/ 10.1206/0003-0090-415.1.1
DOI	https://doi.org/10.5281/zenodo.4610664
persistent identifier	https://treatment.plazi.org/id/8F65ED57-FFF7-B115-3897-CE62B39368B9
treatment provided by	Admin
scientific name	Ischnotelson
status	gen. nov.

Treatment

Ischnotelson View in CoL , gen. nov.

Figures 1 View FIG. 1 B View FIG , 2C View FIG , 9A View FIG , 10A View FIG , 12E View FIG , 15A, B View FIG , 17B View FIG , 19A, B View FIG , 21C View FIG , 22C View FIG , 23O–R View FIG , 36–40 View FIG View FIG View FIG View FIG View FIG

Rhopalurus guanambiensis Lenarducci et al., 2005 (= Ischnotelson guanambiensis ( Lenarducci et al., 2005) View in CoL , comb. nov.), type species, here designated.

Rhopalurus View in CoL (part): Lenarducci et al., 2005: 1 –7, figs. 1–11; Teruel, 2006: 52; Lourenço, 2007: 359; 2008: 3; Prendini et al., 2009: 222; Brazil and Porto, 2010: 50; Porto et al., 2010: 293, 295, table 1 View TABLE 1 ; Lourenço, 2014: 69; Ubinski et al., 2016: 122.

DIAGNOSIS: Ischnotelson , gen. nov., differs from all other rhopalurusine genera by the fused lateral ocular, central lateral and posterior central submedian carinae of the carapace, and the laterally compressed telson vesicle. It differs further from Heteroctenus, Jaguajir , gen. nov., and Rhopalurus by the absence of a pecten-sternite stridulatory organ; from Centruroides and Troglorhopalurus by the robust metasoma, increasing in width posteriorly (more so in the adult male); from Heteroctonus by the presence of two lateral depressions in the male pectinal plate; from Jaguajir by the separate (unfused) lateral ocular and anterior central submedian carinae of the carapace; from Physoctonus by the larger size (30–70 mm), the more distinct carapacial carinae, the setose proximal dorsal fulcra of the pectines, the incrassate pedipalp chela manus of the adult male, the bifurcate prolateral pedal spur of leg I, and the oblique subrows of primary denticles on the pedipalp chela fingers flanked closely by pro- and retrolateral accessory (supernumerary) denticles; and from Troglorhopalurus by the proximal dentate margin of the chela fixed and movable fingers of the adult male emarginate, with a distinct gap evident between them, when closed.

ETYMOLOGY: A fusion of the Greek words ischnos, meaning “thin” or “slender,” and telson, referring to the remarkable, laterally compressed telson of the two species in this genus. Masculine in gender.

DESCRIPTION: The following general description outlines characters common to both species of Ischnotelson , gen. nov.

Total length: Medium-sized scorpions (total length, 30–44 mm).

Color: Carapace and tergites I–VI brown, tergite VII yellow (fig. 1B). Coxosternal region, pectines and sternites pale yellow. Metasomal segments, dorsal surfaces yellowish (segments I–III) to brown (IV and V); ventral surfaces darker; segments IV and V darker than preceding segments, with V darker than IV, almost black. Telson dark orange, aculeus dark brown to black. Legs and chelicerae yellowish. Pedipalps yellow with chela fingers darker than manus, reddish brown.

Chelicerae: Base, dorsal surface with medial transverse row of well-developed tubercles.

Carapace: Median ocular tubercle relatively shallow (fig. 15A–B); two median ocelli; three pairs of lateral macroocelli; one pair of lateral microocelli. Anteromedian, median ocular, and posteromedian sulci well developed, forming single, almost continuous, longitudinal sulcus. Lateral ocular, central lateral and posterior central submedian carinae distinct, finely granular to costate-granular and fused (posterior end of one carina connected to anterior end of subsequent carina) forming single nearly continuous, oblique carina, extending along almost entire length of carapace; anterior central submedian carinae distinct, finely granular and separate.

Pedipalps: Pedipalp femur retrolateral accessory carinae absent. Pedipalp chela manus of adult male incrassate, fixed and movable fingers curved proximally (fixed finger curved dorsally, movable finger curved ventrally), such that proximal dentate margin emarginate, distinct gap present between fingers proximally, when closed (fig. 36), manus of female not incrassate, fixed and movable fingers not curved proximally, such that proximal dentate margin sublinear, little or no gap present between them proximally, when closed; manus, proventral carina present, promedian carina absent; fixed and movable fingers, median denticle rows each comprising eight oblique subrows of primary denticles flanked closely by pro- and retrolateral accessory (supernumerary) denticles; movable finger without proximal lobe ( fig. 17 View FIG. 17 B). Pedipalps orthobothriotaxic Type A, α configuration; femur with five dorsal trichobothria, trichobothrium d 2 situated on prolateral surface; patella trichobothrium d 3 situated retrolateral to dorsomedian carina; chela fixed finger trichobothrium db proximal to trichobothrium et.

Legs: Legs III and IV, tibial spurs absent; I–IV, basitarsi each with bifurcate prolateral pedal spur; telotarsi each with distinct pro- and retroventral rows of fine, acuminate macrosetae.

Pectines: Pectinal plate with two lateral depressions (male), anterior margin with sulcus (fig. 19A–B). Pectines not proximally expanded, at least 1.5× wider proximally than medially; proximal dorsal fulcra setose; pectinal teeth almost straight, slightly curved laterally, proximal teeth, dorsal surfaces covered with small denticles, without striations, dorsobasal surfaces with macrosetae absent or present; pectinal sensillae peg shaped (fig. 12E).

Mesosoma: Tergites III–V slightly wider than I and II in female; I–VI tricarinate, dorsosubmedian carinae finely granular, absent on I and II, restricted to posterior quarter on III– VI; dorsomedian carinae finely granular, vestigial on I and II, restricted to posterior third on III–VI. Tergite VII pentacarinate, dorsomedian carina restricted to anterior two thirds of segment. Sternites smooth, carinae absent or obsolete; sternite III, lateral margins not forming smooth, raised carina, ventromedian carina not elevated anteriorly, ventrosubmedian surfaces not forming paired depressions, finely and irregularly granular (figs. 10A, 19A–B); respiratory spiracles (stigmata) width less than 3× length.

Metasoma: Metasoma robust, increasing in width posteriorly, segment V wider than I, more markedly so in adult male (figs. 37, 38). Segments I–III each with 10 distinct, costategranular carinae, IV with eight distinct, costate-granular carinae, V with seven distinct but less pronounced, granular carinae; dorsosubmedian carinae obsolete, reduced to rows of granules on dorsal surfaces of segments I–IV, more pronounced on segment I; dorsolateral carinae complete on segments I–IV, and terminating in prominent, spiniform granules posteriorly on III and IV, absent on V; lateral supramedian carinae complete on segments I–V; lateral inframedian carinae complete on segments I and II, complete but obsolete on III, absent on IV and V; ventrosubmedian carinae complete on segments I–IV, restricted to anterior third of V; ventromedian carina absent on segments I–IV, complete on V. Intercarinal surfaces finely granular, less so on dorsal surfaces, especially on segment V.

Telson: Vesicle small, slightly elongate and laterally compressed, width ca. half height, considerably narrower than metasoma V, width less than half metasoma V (fig. 22C); anterodorsal lateral lobes reduced; lateral and ventral surfaces smooth, without ventromedian carina; subaculear tubercle pronounced and spinoid.

Hemispermatophore: Flagelliform; flagellum, elongate and narrow (fig. 23O–R); trunk markedly concave; three lobules, ental (LI), ectal (LE), and basal (LB); LI inclined sinistrally relative to axis of trunk and continuous until flagellar base; flagellar base wide (half maximum width of trunk); LE length ca. two thirds that of LI, with curved tip ending in small protuberance, width ca. two thirds that of LB; LB short, carina shaped with sharp tip, ca. 60° angle between LB and LE.

Cytogenetics: The diploid chromosome number of I. guanambiensis is 2n = 25 and of I. peruassu , sp. nov., is 2n = 26 ( table 2 View TABLE 2 ) ( Ubinski et al., 2016).

INCLUDED SPECIES: Ischnotelson guanambiensis ( Lenarducci, Pinto-da-Rocha and Lucas, 2005), comb. nov.; Ischnotelson peruassu , sp. nov.

DISTRIBUTION: Ischnotelson , gen. nov., is endemic to northeastern Brazil. The type and only known locality of I. guanambiensis is in the state of Bahía, whereas the two known localities of I. peruassu , sp. nov., are close to each other (fig. 9A) in the state of Minas Gerais.

ECOLOGY: The known localities of Ischnotelson , gen. nov., occur at the ecotone of Brazilian caatinga and cerrado (fig. 2C).

REMARKS: The consistent paraphyly of Rhopalurus in the analyses by Esposito et al. (in review) and the identification of a well defined, monophyletic group comprising R. guanambiensis and the new species described below, justifies the creation of the new genus and the transfer of R. guanambiensis to it, resulting in a new combination (fig. 13). The recognition of a new genus is consistent with the cytogenetic study of Ubinski et al. (2016) which identified a diploid chromosome number of 2n = 25 for R. guanambiensis and 2n = 26 for I. peruassu , sp. nov., and a third, as yet undescribed species ( table 2 View TABLE 2 ).