Urophonius somuncura, Acosta, 2003

Acosta, Luis E., 2003, Description of a new Patagonian species of Urophonius Pocock (Scorpiones, Bothriuridae), from Meseta de Somuncurá, Argentina, Zootaxa 187 (1), pp. 1-12 : 2-10

Urophonius somuncura n. sp.

Figs.1­8

Urophonius sp. Maury, 1979a: 67 ; Acosta, 1986: 28, 1988: 27, 32; Acosta & Maury, 1998: 554; Ojanguren Affilastro, 2002: 185.

Type series: Holotype female ( CDA 000.151), 9 female and 7 juvenile paratypes (CDA 000.152), 2 female paratypes (FML), 2 female paratypes (IADIZA), 9 female and 4 juvenile paratypes (LEA 000.232): Argentina. Province of Río Negro. Meseta de Somuncurá, Laguna Pelada , 7 December 1985, L. Acosta leg. — 1 paratype female (MACN), Meseta de Somuncurá, Laguna Chara, 18 December 1968, J.M. Cei leg.

Additional material examined: Argentina. Province of Río Negro : Meseta de Somuncurá, Laguna Pelada, 12 January 1985, L. Acosta leg., 1 female, 1 juvenile, under a stone, daytime ( LEA 000.233); same loc., 13/ 14 January 1985, L. Acosta, G . Flores leg., 8 females, 4 juveniles (U.V.) ( LEA 000.234); Cerro Corona , 17 December 1968, J.M. Cei leg., 1 juvenile ( MACN) .

Etymology: The species is named after the Meseta de Somuncurá; noun in apposition.

Diagnosis: Member of the ' granulatus species group' ( Acosta 1988), as defined by the ventral pigment pattern of metasoma (ventrolateral and axial stripes, not joining in any segment), the number of ventral macrosetae on metasomal segments I­II (2+2, 3+3 respectively), and by the position of trichobothrium e of femur (close to macroseta M1); since males of the new species are unknown, it remains to be determined if features of the lobe region of the hemispermatophore fit into the group definition. Ventral surface of sternite V and metasomal segment I granulous, only VL carinae discernible. Insertion of ventral setae on metasomal segments I­II forming a hemicircular tegumentary border. Carapace pigment almost continuous from the eye mound to the anterior border. Lateral pigment stripe on metasomal segments I­IV not joining the ventrolateral pigment. The nearest relatives of U. somuncura n. sp. are U. granulatus and U. tregualemuensis (see 'Comparisons' below).

Description: Small to medium sized bothriurids; total length (adult females) up to 32 mm (measurements of holotype: Table 1 ). Males unknown. General colour straw yellow, slightly more orange towards the caudal end of the metasoma; pedipalps and legs lighter, pectines whitish yellow; irregular pigment on carapace, mesosomal tergites, metasoma, pedipalps and legs, very faint in pectines.

Pigment patterns. Carapace. With a dense spot between the eyes, the pigment extends, less densely, up to the anterior border, except for some small clear areas; posterior half with larger depigmented areas, the pigment forms several diagonal stripes and an enlarged triangular spot on each side of the posterior border.

Tergites. With pigment very similar to U. granulatus : general appearance of four longitudinal dark stripes intercalated with five more or less depigmented areas on tergites I­ VI; the median clear area is approximately diamond­shaped on the posterior half of tergites III­VI; paramedian pigment consisting in a darker basal portion, an inclined or bracket­shaped middle part, and a fainter medial­anterior portion, often joining medially the opposite paramedian stripe; each paramedian stripe is aligned to a well­defined spot on the pretergite; the paralateral pigment, with an irregular medial edge, is continued in the pretergite, too. Tergite VII: border of the pretergite with a dark line, only medially interrupted; on the tergite proper, two subtrapezoidal dark spots with open areas inside, reaching the posterior border but separated from the anterior and lateral borders, and from each other (clear median line, except for faint anterior projections connecting medially). Sternites I­V depigmented, except for the lateral edges on sternites II­V, and three small dots on the caudal border of the last sternite.

Metasoma. Segments I­IV: a dark line along the DL carinae, in some specimens dashed; on segments I­III this line reaches the posterior border, diverging from there laterally and almost touching the lateral pigment; the dorsal surface has paired spots on segments I­III (in a few specimens joining to form a single median spot), as diagonal stripes on segment I, as shield­like spots on segments II­III, in all cases touching the DL lines in the middle; segment IV only has tenuous longitudinal lines on the dorsal face; lateral side of segments I­IV with a well­defined dark stripe, with irregular borders, it remains independent both from the dorsal and the ventral pigment; ventral face with well­defined ventrolateral and axial lines, which do not coalesce all along the metasoma; segment I is variable concerning the ventral pigment, in many specimens very faint or almost vanishing; this variation ranges from 'axial line present', bordered by vestigial paramedian 'ramifications' originating in the ventrolateral stripes (as in the holotype: Fig. 4 ) to 'ventral surface nearly completely depigmented' (see Variability); the axial line can also be slightly interrupted shortly before the posterior border on segment II, less frequently on segment III. Segment V: ventral axial line complete, lateroventral stripes widening posteriorly (the area has no dense pigment but a rather 'dotted' appearance); on the caudal end the pigment expands to the lateral side (joining there an irregular lateral stripe), and to the dorsal side, forming a dorsolateral stripe. Telson with brown pigment on the ventral side, dorsal side yellowish.

Pedipalps. Pro and retrodorsal borders of femur with irregular pigment; patella with similar pigmentation, plus a dark stripe on the retrolateral surface; chela with longitudinal, irregular stripes; legs irregularly spotted, being more remarkable on femur and patella.

Morphology. Carapace, tergites I­VI and sternites I­IV smooth; tergite VII with granulous carinae on the posterior half; sternite V with a median­posterior granular area. Metasomal carinae on segments I­IV: DL complete, denticulate and conspicuous; LSM also complete, formed by small granules roughly aligned; the surface between DL and LSM with scattered small granules; LIM less defined, granulous, forming an irregular row on segments I­II, but almost disappearing in a less granulous sector on segments III­IV; VL less developed, yet well defined on segments I­II, they become tenuous on segments III­ IV; on segment I they delimit a ventral area, irregularly granulous, which represents the undefined VSM; the granulous ventral area is less accentuated on segment II, almost disappearing on III­IV; 2+2 ventral macrosetae on segment I, 3+3 on segments II­III; on segments I­II, the insertion of each macroseta is anteriorly bordered by a slight tegumentary hemicircle, often formed by an arch of granules. Segment V: DL restricted to the basal quarter, with large, blunt granules; LM represented by an inconspicuous 'stripe' of tiny granules, which joins caudally to the ventral granulation; ventral side densely granulous; VL and VM carinae complete, they are normally somewhat hidden by the general granulation, but can still be recognised by their larger granules (especially on the posterior half) and because they are on slightly elevated ridges; VM widening posteriorly into a triangular granulous area; the ventral granulation leaves only smooth basal sectors on each side of VM. Telson irregularly granulous on the ventral side, dorsally smooth. Pedipalps: femur slender, with granulous pro­ and retrodorsal borders, trichobothrium e situated close below the macroseta M1 or a little more basally; chela slender, with relatively long fingers; cutting edge of fingers with one single row of granules, and 5+5 accesory granules; like in females of other Urophonius species , the medial side of the chela shows a small (vestigial?) tubercle near ib. Trichobothriotaxy as for the genus. Tarsal spine count: holotype with III 5­6 / 5­6, IV 6­7 / 5­6 (see Variability). Pectinal teeth 13 to 16, holotype with 16­ 15 (see Variability).

Variability: Tarsal spine formula, based on 50 specimens, with some tarsi lost (in a pair, the first number refers to the retrolateral row: Maury 1977). Frequencies on T III (n = 97 tarsi): 4­4 spines (2 tarsi), 3­5 (2), 4­5 (15), 4­6 (3), 5­5 (39), 5­6 (35), 5­7 (1). Frequencies on T IV (n = 94): 4­5 (1), 4­6 (2), 5­5 (4), 5­6 (38), 6­6 (15), 6­7 (32), 5­7 (2).

Number of pectinal teeth. Frequencies in adult females (n = 66 pectines): 13 teeth (2 pectines), 14 (20), 15 (35), 16 (9).

Ventral pigment on metasomal segment I (n = 50 specimens): with evident paramedian spots, median line well developed (8 specimens); with just small traces of the paramedian spots, median line may be more or less reduced (18); no trace of the paramedial spots, median line either well developed or reduced (15); all parts of ventral pigment absent or vestigial (8).

Comparisons: U. somuncura differs from its nearest relatives, U. granulatus and U. tregualemuensis , by the following characters: VL and VSM carinae on metasomal segment I well developed and granulous in U. granulatus , forming conspicuous tegumentary elevations ( Maury 1979a, Acosta 1988); in U. tregualemuensis the VSM carinae are low but still recognizable as an irregular row of pearl shaped granules, spreading also in a granulous area towards VL; in U. somuncura, VSM carinae no longer exist, but instead are completely dispersed in a flat ventral area, with small scattered granules. Similarly, ventral carinae are well developed on the posterior half of sternite V of U. granulatus , but not in U. tregualemuensis and U. somuncura , just represented by a posterior granular area.

For both U. tregualemuensis and U. somuncura the insertion of the ventral submedian macrosetae on metasomal segments I­II determines the formation of a hemicircular tegumentary border around each seta (see Acosta 1988: fig. 3); these borders are conspicuous in the Chilean species, and much less noticeable in U. somuncura . Ventral setae of U. granulatus do not form tegumentary borders.

The position of trichobothrium e of femur shows a subtle variation among the species in the group ( Acosta 1988): in U. granulatus it is more distal than M1; in most specimens of U. tregualemuensis it is clearly more basal, while in U. somuncura it lies close below the previously mentioned macroseta or just a little more basally.

Like U. granulatus , the metasomal segment I of U. somuncura always bears 2+2 ventral macrosetae; in U. tregualemuensis some variability exists (either 2+2, 2+3 or 3+3 macrosetae; Acosta 1988).

Both in U. granulatus and U. somuncura the lateral pigment stripe on metasomal segments I­IV does not join the ventrolateral pigment; in U. tregualemuensis an irregular reticle fills the area between those stripes, thereby connecting them.

In U. somuncura , the carapace pigment covers almost continuously the area from the eye mound to the front edge, while in U. granulatus a transversal clear sector separates the ocular and frontal spots; the pattern in U. tregualemuensis is distinct, since the pigment leaves a large triangular area clear on the anterior border, or at most with a tiny median dot or line.

Some specimens of U. somuncura show vestigial paramedian pigment on the ventral side of metasomal segment I (see Fig. 4 ), a condition never seen in both U. granulatus and U. tregualemuensis .

To insert the new species in the genus key provided by Acosta (1988), couple 5 has to be modified, as follows:

5. VSM carinae on metasomal segment I and sternite V well defined, on tegumentary elevations. Insertion of ventral setae (segments I­II) does not form tegumentary borders. Trichobothrium e more distal than M1 ............................................................................................... U. granulatus

­ VSM carinae on metasomal segment I and sternite V dispersed on a granulous area. Insertion of ventral setae (segments I­II) forms anteriorly a tegumentary hemicircle. Trichobothrium e close below or more basal than M1...................................................................................................... 6 6. Carapace with an anterior clear triangle free of pigment, with just a tiny spot or line. Mesosomal tergites I­VI with a single median clear stripe. Lateral pigment stripe on metasomal segments I­IV connected with the ventrolateral stripe through a dense reticle. Ventral surface of metasomal segment I with pearl­shaped granulation. Ventral setae of segment I can be either 2+2, 2+3 or 3+3; hemicircular tegumentary elevations around the setae well developed............ ........................................................................................................................ U. treg ualemuensis

­ Carapace with pigment filling the preocular area up to the anterior border. Mesosomal tergites I­VI with one median and two paralateral clear stripes. Lateral pigment stripe on metasomal segments I­IV does not join the ventrolateral stripe. Ventral surface of metasomal segment I with small, scattered granulation. Always 2+2 ventral setae on segment I; hemicircular tegumentary elevations around the setae feeble ................................................. U. somuncura n. sp.

Habitat and natural history: Urophonius somuncura n. sp. has been hitherto collected only on the higher plains of the Meseta de Somuncurá. According to the detailed descriptions by Cei (1969) and Ruiz Leal (1972), well­defined altitudinal belts can be identified in this tableland, which are easily recognizable along the road that leads from the locality of Valcheta (192 m a.s.l., 40°39'S 66°09'W) up to the Meseta ( Fig. 9 ). Between 200 and 500 m the typical Monte physiognomy, dominated by Larrea spp. ('jarilla') is observed. On the initial spurs of the tableland some Patagonian elements appear, gradually replacing Monte elements as the ascent progresses; it is thus an ecotonal belt (~ 500­900 m), which was denoted by Cei (1969) as 'belt of the ravines' or 'belt of the filtrating streams'. From 900 m upwards the environment has a definite Patagonian character. Cei (1969) named the sector between 900 and 1400 m as 'belt of the plains' or 'belt of the argillaceous ponds'. Indeed, the lowest part of this belt (900­1200 m) still shows a rough and undulated landscape, with extensive shrub­sized vegetation, especially formed by the hemispheric bush known as 'neneo' ( Mulinum spinosum ); near the 1200 m altitude the conspicuous silverly plants of Senecio filaginoides also appear. The scorpion species Bothriurus burmeisteri Kraepelin, 1894 , widespread in the Monte region ( Maury 1979b), was found to reach both the ecotonal sector (500­900 m) and the lower portion of the plains belt ( Acosta 1986); in January, many specimens of B. burmeisteri were collected at Puesto La Cortadera (ca. 1000 m), including a couple in courtship.

Above, on the plains proper, the vegetation turns to a grassland dominated by the 'coirón' ( Poa spp. , Stipa spp. , Festuca spp. ), together with numerous cushion­shaped plants, like the rock­hard Azorella sp. ('leña de piedra' = 'stone firewood'). These upper plains are only slightly undulating and have a rigorous climate, with wide daily and seasonal variations in temperature and continuous winds, predominantly from the SW. They contain several depressions or 'ponds' of centripetal drainage, whose borders are partially surrounded by basaltic cliffs of diverse size. The water content of these ponds originates from the sporadic rainfalls, as well as from summer thawing, and may persist for several weeks, even for years in the larger ones, thanks to their argillaceous bottom. Urophonius somuncura n. sp. was collected in this belt, together with Bothriurus sp. ( Acosta 1986) . A few volcanic peaks elevate above the plains level, especially in the SE portion of the Meseta, such as the Cerro Corona (ca. 1700 m), the highest elevation in Somuncurá; Cei (1969) distinguishes here the 'belt of the volcanic peaks' (1400­ca. 1700 m). Most specimens studied of U. somuncura n. sp. come from the type locality (near the pond called 'Laguna Pelada'), while material already examined by Maury (1979a) was collected near Laguna Chara and at the base of Cerro Corona.

The east­faced cliffs that surround the Laguna Pelada offer some protection against the WSW winds, and this allows the development of quite dense shrub vegetation ( Fig. 10 ). Amongst the blocks of rock, tortuous and almost hanging saxicolous shrubs ( Schinus sp. , Berberis sp. ) develop, forming together with the numerous and irregular crevices many potential shelters for faunal elements. Other pools were examined (Lagunas Valerio, Paraguay Chico, Paraguay Grande), but only Laguna Pelada had a cliff protected enough, with such dense shrub vegetation. Samples were obtained during separate summers, in January and December 1985, in the same site around Laguna Pelada. Diurnal search was very difficult (specimens are suspected to hide in the deep crevices), but with U.V. light, scorpions were easily detected during the night. In December, 34 specimens (females and juveniles) of U. somuncura n. sp. were caught, together with a single juvenile Bothriurus sp. In January, the sampling yielded 14 specimens of U. somuncura n. sp. (females and juveniles) and 16 specimens of Bothriurus sp. (males, females, couples in courtship). No male of U. somuncura n. sp. was found during the mentioned months. To interpret these results, observations made by Maury (1979a) on the close relative U. granulatus could be extrapolated here. In southern Patagonia, males of U. granulatus are most frequent at the beginning of the surface activity period (October­November), and become very rare in JanuaryFebruary, when almost only females and juveniles are collected. U. somuncura n. sp. might have a similar pattern of surface activity, with females showing a decreasing activity in December­January, as revealed in the samples. For their part, males and females of Bothriurus sp. seem to appear almost simultaneously by the turn of the year. These results may be consistent with slightly asynchronous surface activities of the two scorpion species that are sympatric in the pond area. In January, when the proportion of these species is approximately similar, Bothriurus sp. was found in more diverse locations within the site ( Fig. 10 , below): on the upper side of the cliff, which is exposed to the winds (either near the base of 'coiron' plants or under the tangle of shrub twigs); at the base of the rocky wall, and even more than 500 m away from the pond, under a stone by the road; in very few occasions, Bothriurus specimens were detected climbing on the vertical wall. In that month all U. somuncura n. sp. were on the rocky wall, normally half hidden by small irregularities of the rock, none being found on the exposed areas. By contrast, in December (i.e. when Bothriurus sp. was apparently still not active), specimens of U. somuncura n. sp. were seen in all previously mentioned locations (upper exposed area, base, and vertical wall). Thus, it is also possible that occupying a differential 'microhabitat' might help U. somuncura n. sp. to avoid predation by Bothriurus sp. (of larger size) during this overlapping period.

Zoogeographic comments: As mentioned above, the Meseta de Somuncurá was deemed to be like a Patagonian 'peninsula' within the Monte Province ( Ruiz Leal 1972; Cabrera & Willink 1973). Regarding its scorpiofauna, however, it should be best considered a distributional island ( Acosta & Maury 1998). The insular condition is actually restricted to the 'coiron'­fields plateau, since, as has been seen, below 1200 m only Monte scorpions have been found. One of the relatives of U. somuncura n. sp., U. granulatus , inhabits the southern end of the Patagonian steppe, mainly in the Argentinean province of Santa Cruz and adjacent sites in south Chile ( Maury 1979a); the northernmost locality of this species is Los Altares, province of Chubut (43°53'S 68°24'W; see Acosta 1988: fig. 15), which lies around 300 km south of the Meseta de Somuncurá. Except for this northern record, the known range of U. granulatus corresponds well with the 'southern Patagonian area' as defined by Cei (1979); the dominant vegetation of this area consists of 'coirón' grasslands, similar to the upper plains in Somuncurá, so it can be stated that these two closely related species occupy comparable biotopes. The northern Patagonian area resembles more the 'neneo' sub­belt, that is, the lower portion of the Somuncurá plains. Concerning Bothriurus sp. , its nearest relatives are the members of the ' patagonicus species group', which include the nominal species B. patagonicus Maury 1968 , and some undescribed entities as well ( Maury 1968, Mattoni & Acosta, in prep.). The distribution of the patagonicus group ranging from a narrow strip near the Andes in the province of Neuquén, and widening into a broader area southwards, in the province of Santa Cruz ( Maury 1979b) fits well into the 'Patagonian scorpiogeographical area' as defined by Acosta & Maury (1998); only Bothriurus sp. from Somuncurá shows a disjunct pattern. It is worth noting that the Somuncuran herpetofauna (lizards and amphibians) contains six species that are widespread in Patagonia, as well as three species and two subspecies that are endemic to the Meseta ( Cei 1979). The endemics Atelognathus reverberii ( Cei, 1969) ( Leptodactylidae Telmatobiinae) and Liolaemus ruizleali Donoso Barros & Cei, 1971 (Liolaemidae) were found above 1000 m ( Cei 1979).

Figures

FIGURE 9. Location of the Meseta de Somuncurá (S) in northern Patagonia, Argentina. The type locality is indicated with a star, the Cerro Corona with a black triangle. Dark grey: areas above 900 m; adjacent solid line: 600 m altitude. Dotted line near Valcheta: the 'Arroyo Valcheta' stream. Dashed line: administrative boundary. Inset: location of the represented area in South America.

FIGURE 10. Above: west side of Laguna Pelada, type locality of Urophonius somuncura n. sp.; the collecting site is located around the cliffs and rocky outcrops, with scrub vegetation on the right. Below: Schematic representation of a profile of the type locality (not to scale); locations where scorpions were found are indicated by numbers (1-5). In January, U. somuncura n. sp. was collected only at location number 2, and Bothriurus sp. at locations 1 and 3-5. In December, U. somuncura n. sp. was detected in all 1-5 spots.

FIGURES 1­8. Urophonius somuncura n. sp. 1­7: holotype female (CDA), 8: generalised from several individuals. 1, metasomal segment V and telson, lateral view; 2, metasomal segment V, ventral view; 3­4, sternite V and metasomal segments I­II, ventral view, 3, morphology (ventral macrosetae as black dots), 4, pigment pattern (macrosetae as open circles); 5­6, right pedipalp chela, 5, ventromedial view, 6, lateral view; 7, right pedipalp femur, retrolateral view (indicated trichobothrium e and macroseta M1). 8: pigment pattern on tergite V. Scale lines: 1 mm.

Tables

TABLE 1. Measurements (mm) of the holotype female of Urophonius somuncura n. sp.

Body length	31.8
Carapace length	4.1
anterior / posterior width	2.8 / 4.4
Mesosoma length	8.9
Metasoma length	18.8
Metasomal segment I length / width	1.9 / 2.5
Metasomal segment II length / width	2.2 / 2.3
Metasomal segment III length / width	2.3 / 2.2
Metasomal segment IV length / width	2.9 / 2.2
Metasomal segment V length / width / height	4.3 / 2.1 / 1.9
Telson length / width / height	5.2 / 1.9 / 1.5
Aculeus length	1.3
Pedipalp total length	13.4
Femur length / width	3.5 / 1.0
Patella length / width	3.8 / 1.3
Chela length / width / height	6.1 / 1.2 / 1.3
Movable finger length	4.0