Eusarcus xambioa, Júnior & Ázara & Ferreira, 2021

Júnior, Gilson Argolo dos Santos, Ázara, Ludson Neves de & Ferreira, Rodrigo Lopes, 2021, Three new species of Eusarcus Perty, 1833 (Opiliones, Gonyleptidae) from Brazilian caves, European Journal of Taxonomy 740 (1), pp. 36-54: 47-52

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Eusarcus xambioa

sp. nov.

Eusarcus xambioa   sp. nov.

Figs 7–11 View Fig View Fig View Fig View Fig View Fig


Eusarcus xambioa   sp. nov. resembles E. aduncus   , E. armatus   , E. cavernicola   , E. dandara   , E. fulvus   , E. mirabilis   and E. oxyacanthus   by having coxa IV with one transversal, proapical, acute and conical apophysis but can be distinguished by the following characters: short (shorter than trochanter IV width) probasal apophysis on trochanter IV, high ocularium with spine, and femur IV with proventral and retroventral rows of acuminate tubercles increasing in size apically.


The specific epithet ʻ xambioa   ʼ means ʻfast birdʼ in the TUpi langUage and refers to a groUp of natives of the Araguaia River. It also refers to the municipality where the type was found.

Material examined

Holotype BRAZIL • ♂; Tocantins State, Xambioá MUnicipality, Caverna da Explosão ; 6°25′36.8″ S, 48°22′30.0″ W; 21 Feb. 2018; R.L. Ferreira et al. leg; ISLA 60386. GoogleMaps  


Male (holotype, ISLA 60386)

MEASUREMENTS. DSL 3.77, DSW 3.19, femur I 2.38, II 4.80, III 3.25, IV 4.49.

DORSUM ( Fig. 7A, C View Fig ). Blunt PAM; acuminate median paracheliceral projection similar in size to PAM. High ocularium with median spine (about twice times ocularium height). Carapace with scattered granules. Scutal areas I–IV with scattered granules with some tubercles among them. Posterior margin of dorsal scutum with scattered granules. Lateral margins with blunt tubercles about the same size as those on the scUtUm. Free tergites I–III with a defined row of granUles. Anal opercUlUm with scattered granules.

VENTER ( Fig. 7B View Fig ). Coxa I with irregular row of setiferous tubercles, coxae II–IV densely and irregularly granulate.

CHELICERAE. Segment I with two ectal-basal tubercles and one mesal-basal tubercle.

PEDIPALPS. Trochanter with sparse tubercles dorsally. Femur with one mesal apical setiferous tubercle. Tibia setation: ectal IiIi, mesal IiIi; tarsus setation: ectal IIIi, mesal IIi.

LEGS ( Fig. 8 View Fig ). Coxae I–III with scattered granules; coxa IV with one transversal, prolateral and apical apophysis, which is conical and short. Trochanters I–IV with scattered tubercles; trochanter IV with one probasal apophysis, which is conical, short and dorsally oriented. Femur III with proventral and retroventral rows of acute tubercles increasing in size apically; tibia III with proventral and retroventral

rows of acuminate tubercles. Femur IV slightly sinuous, with small PDS and RDS, proventral row of acuminate tubercles increasing in size apically and retroventral row with reduced tubercles; tibia IV with proventral and retroventral rows of acuminate tubercles increasing in size subapically.

PENIS ( Fig. 9 View Fig ). Ventral plate with substraight lateral margins; distal margin slightly concave; ventral surface entirely covered with type T1 microsetae; with three pairs of lateral-distal MS C1–C3, three pairs of A1, one pair of B1, one pair of minute D1 and E1 absent. Stylus with ventrally-tilted medianventral trichomes. Ventral process tUbUlar, cUrved, with apex with flabelliform projection.

COLOURATION (in alcohol) ( Figs 7–8 View Fig View Fig ). Body and appendages background colour Deep Orange Yellow (69), appendages Strong Orange Yellow (68).



Geographical distribution

Known only from the type locality ( Fig. 11 View Fig ).

Ecological remarks

Caverna da Explosão is a limestone cave with 1203 meters of horizontal projection. The main entrance of the cave collapsed in the past, so that the access to the cave interior is currently made through a small entrance located at the base of the outcrop, leading to a very narrow passage. Most of the cave floor is covered with terrigenoUs sediments, althoUgh a few fallen blocks are also present. Most of the organic resources occurring in the cave are vegetal debris transported by water during strong rains and especially bat guano, produced by a variety of bat species, although droppings of hematophagous bats are the most common ones. Despite the lack of any regUlar water flow, several areas of the cave can be partially submerged during the rainy period. The single collected specimen was observed freely walking on the cave floor ( Fig. 10C View Fig ), close to a gUano pile prodUced by hematophagoUs bats. Since the cave was not completely surveyed during our sampling, there is no indication of the size of the species’ population and its density inside the cave. The region presents an Aw5 climate according to the Köppen classification system, with an average annUal precipitation of aroUnd 1558 mm and an average annual temperature of 26.3ºC. The external area is quite altered, especially due the replacement of natural vegetation by Eucalyptus L’Hér.   plantations. However, the outcrop where the cave is located is surrounded by secondary forest. As with the other species described herein, the area outside the cave was not sampled, so it is impossible to determine the habitat preference for this species.