Eremocosta arenarum, Ballesteros, Alfonso & Francke, Oscar F., 2007

Ballesteros, Alfonso & Francke, Oscar F., 2007, A new species of sun-spider from sand dunes in Coahuila, Mexico, (Arachnida: Solifugae: Eremobatidae), Zootaxa 1665, pp. 61-68 : 62-67

Eremocosta arenarum sp. nov.

Figs. 1–6

Type material: Holotype and six paratypes from Dunas de Bilbao, (25° 25.586’N, 102° 53.654’W, 1 0 98 m, Municipio Viesca, Coahuila, México) 20 July 2006, Oscar F. Francke, Kari J. McWest, Abigail Jaimes-Barrientos, Milagros Córdova-Athanasiadis and Alfonso Ballesteros leg.

Type depositories: Holotype CNAN-T0264, and paratypes CNAN-T0265 (putative female), CNAN- T0266 (one male and one immature) deposited in the Colección Nacional de Arácnidos, Instituto de Biología, UNAM, México City. Three male paratypes deposited in the American Museum of Natural History, New York.

Etymology: The specific epithet is the plural genitive of the Latin noun for sand “ arena”, and it means “of the sands”.

Diagnosis: The new species belongs in the montezuma species group, along with E. montezuma (Roewer) , E. fusca (Muma) and E. acuitlapanensis (Vázquez & Gaviño-Rojas) , and they differ from all other Eremocosta members in bearing abdominal ctenida. This new species is readily differentiated from the rest of the Eremocosta montezuma species group, because it is the only one in which the males possess two ctenidia, whereas the males of the other species have four ctenidia. E. montezuma and E. fusca , differ in that both possess a shallow but distinct fondal notch, whereas E. arenarum lacks that notch. Differences in cheliceral dentition of the movable finger are also present; according to the figures in Muma (1970, fig. 3.) E. montezuma possesses an apical tooth near the base of principal tooth, and the two intermediate teeth grow on the base of the principal tooth. E. fusca resembles E. arenarum in having well-separated principal and apical teeth, but intermediate teeth are considerably smaller in E. fusca than in E. arenarum (c.f. with figs. 1 and 2 in Muma, 1987). The most similar species to E. arenarum seems to be Eremocosta acuitlapanensis from Acuitlapan, Guerrero, in that males of both species share the possession of long ctenidia and a shallow and indistinct fondal notch. However, the “tooth like” process that E. acuitlapanensis possesses mesoventrally near the base of the fixed finger ( Vázquez & Gaviño-Rojas, 2000), and the number of ctenidia (four instead of two), easily separate them.

Description. Male Holotype:

BL 16.0; CL 5.12; CW 2.12; FFW 0.37; PL 2.37; PW 3.50; PpL 20.0; LI 13.0; LIV 26.0; A/CP 7.87; CW/ FFW 5.72; PL/PW 0.677.

Prosoma. Pale yellow overall except for the eye tubercle, covered with several hair like bifid setae, and without spines.

Chelicerae ( Figs. 1–3 ). Pale yellow without markings. Fixed finger broad, without teeth on its ventral edge, except for two small denticles at the base, the distal one very small and indistinct; mesoventral groove very shallow, not reaching the base of the finger. Flagellum complex composed exclusively of tubular setae. Mesal row of fondal teeth graded in size from bigger to smaller as follows: I-III-II-IV, ectal row: I-III-IV-II. Fondal notch very shallow and indistinct. Movable finger with two intermediate teeth between the principal and apical teeth, the proximal one slightly bigger than the distal; mesal tooth present.

Pedipalpi. Pale yellow except for dusky markings at the distal end of femur, tibia and tarsus, these fading at the tip. Tarsus and tibia without papillae.

Opisthosoma. The abdomen is also pale yellow but somewhat transparent, appearing brownish due to the color of the viscera. First post-spiracular sternite with two needle-like ctenidia, and slightly curved outwards ( Fig. 4 ), which reach the posterior edge of the next sternite.

Legs. Leg I pale yellow, legs II–IV dusky at proximal half of the patella. Leg I with one small broad triangular claw at the tip of the palpal tarsus, normally obscured by several bristles. Malleoli on ventral surface of leg IV white. Legs II–III basitasus and tarsus armed with several spines on ventral and dorso-posterior surface.

Paratype (putative female)

BL 19.0; CL 7.37; CW 2.62; PL 3.62; PW 5.25; PpL 20.0; LI 18.0; LIV 29.0; A/CP 6.09; PL/PW 0.689.

Coloration similar to the male, but eye tubercle dusky instead of dark, and without any markings on pedipalpus and legs. Distal segments of palpus and leg I, appear reddish due to the presence of numerous short and dense bristles.

Chelicerae ( Figs. 5, 6 ). Fixed finger principal tooth larger than the anterior tooth, but smaller than the medial tooth. Two intermediate teeth between the principal tooth and the medial tooth, one intermediate tooth between medial and anterior tooth. Fondal teeth graded in size I-III-II-IV in mesal row and III-II-I-IV on ectal row. Movable finger with two intermediate teeth between principal and apical teeth, the distal one smaller than the proximal and only appreciable in mesal view; mesal tooth indistinct, appearing more like a soft ridge below the principal tooth of movable finger.

Opisthosoma. Genital sternite without pits, not sclerotized, almost indistinct, triangular shaped and with both edges, anterior and posterior rounded. The apical lobes of the genital opercula seem to connect in the middle on both the anterior and posterior edges.

Variation. Adult males measurements (n= 4): BL 14.0–16.0; CL 4.62–5.50; CW 2.00–2.37; FFW 0.37; PL 2.25–2.62; PW 3.37–3.62; PpL 18.0–19.0; LI 12.0–13.0; LIV 22.0–25.0; A/CP 7.03–7.56; CW/FFW 5.40–6.4; PL/PW 0.667–0.723. Immature: BL 9.0; CL 3.5; CW 0.75; PL 2.0; PW 2.75; PpL 8.0; LI 6 LIV 13.0 A/CP: 4.9.

Some variation in color is also present, the three male paratypes show faded dusky markings on the apical end of the patella of pedipalpus, instead of the pale yellow coloration of the holotype.

The immature paratype exhibits a cheliceral dentition similar to that of the putative female. The tarsi, metatarsi, tibiae, and distal half of the femora of palpi of the immature are dusky, and its abdomen is somewhat greenish.

Distribution. Known only from the type locality.

Life history and habitat preferences. All specimens were collected in an unconsolidated and actively drifting dune field that was sparsely vegetated with bushes.

They were detected with the aid of portable ultraviolet lamps and were captured by hand ( Fig. 7 ).

Remarks. Female identification at the species level within the montezuma group is complicated. First, the female of E. montezuma is unknown. Second, those of E. fusca are not clearly diagnosed, as the female paratypes described by Muma are from different localities and show differences in size, color, and the operculum (Muma 1987), and it is probable that at least some of those specimens belong to a species other than E. fusca .

The paratype (CNAN-T000265) of the new species is probably an immature female. It does not have the genital sternite sclerotized, as the adult females in this family normally show. The specimen is bigger than the adult males collected and although size has been shown to be very variable, females are usually bigger than males. The specimen was dissected and we could not confirm the presence of mature ovaries, or testes. Although it was not possible to accurately determine the sex or life-stage of this paratype, we decided to illustrate the cheliceral dentition, because it could be useful in further comparisons.

Females of E. acuitlapanensis differ from the putative female paratype of E. arenarum in the cheliceral dentition of both fingers. The females of E. acuitlapanensis exhibit a conspicuous mesal tooth on the movable finger, which is vestigial to obsolete in the putative female paratype of E. arenarum (see description above). Females of E. fusca are similar to E. arenarum in having an indistinct mesal tooth on the movable finger, but the cheliceral profile of E. fusca (fide Muma, 1987) shows the intermediate teeth of both cheliceral fingers rising near the anterior edge of the principal tooth, whereas in E. arenarum the intermediate teeth are well separated.

Members of the montezuma group of Eremocosta differ from other members of Eremocosta in having an indistinct crease on the mesal face of the male's fixed cheliceral finger. This feature is shared with members of the genus Eremorhax , which differ, however in other respects (such as leg length). Members of the montezuma group differ further from other members of Eremocosta in the possession of abdominal ctenidia. While these differences could justify the erection of a new genus, we defer such a taxonomic decision until a thorough cladistic analysis of the entire family can be performed

Figures

FIGURE 4. Eremocosta arenarum sp. nov. Sternites X – XII of males showing ctenidia

FIGURE 7. Landscape in the type locality (Photograph by Kari J. McWest).

FIGURES 1 – 2. Eremocosta arenarum sp. nov. 1 Ectal view of right male chelicera lateral view, 2 Mesal view of right male chelicera. Scale 1 mm.

FIGURE 3. Eremocosta arenarum sp. nov. Detail of male cheliceral fixed finger, showing the mesoventral groove.

FIGURES 5 – 6. Eremocosta arenarum sp. nov. 5 Ectal view of right chelicerae of the putative female, 6 Mesal view of right putative female chelicera. Scale 1 mm.