Orobothriurus bivittatus (Thorell 1877)

Acosta, Luis E., 2005, Rediscovery of Orobothriurus bivittatus (Thorell 1877) stat. n., comb. n. in the Sierra del Tontal, Argentina (Scorpiones, Bothriuridae), Zootaxa 916, pp. 1-15 : 3-11

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https://doi.org/ 10.5281/zenodo.171062



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Orobothriurus bivittatus (Thorell 1877)


Orobothriurus bivittatus (Thorell 1877) stat. n., comb. n.

Figs. 1–7 View FIGURES 1 – 5 View FIGURES 6 – 7

Cercophonius brachycentrus var. bivittatum Thorell 1877a: 183 [recte bivittatus ].

Urophonius brachycentrus bivittatus: Mello­Leitão 1931: 99 –100; 1933: 35; 1934: 48, 51; 1938: 94–95; 1945: 213, 215; Acosta & Maury 1998: 559; Lowe & Fet 2000: 44.

Urophonius brachicentrus bivittatus: Mello­Leitão 1939: 612 ; Abalos 1959: 592; 1963: 117; Roig Alsina 1973: 200 (incorrect subsequent spelling).

? [ Orobothriurus alticola View in CoL ]: Maury 1977: 148 (synonymy and combination suspected, not formally proposed)

Orobothriurus alticola: Acosta 2002: 177 View in CoL (formal synonymy, here removed).

Type material. Holotype juvenile ( NRS), examined. This specimen is stored in a small vial with the label " Urophonius brachycentrus bivittatus (Thorell) , E. Maury det. 1971". In turn, this vial is placed within a larger vial labeled: " Cercophonius brachycentrus Thor. , Córdova (pullus), S. Juan, Argentina, Weijenb.", and containing a further small vial with one adult male and a second juvenile (these two specimens constituting the type series of Urophonius brachycentrus ). Because the original holotype is a poorly preserved juvenile, it provides little information on the species identity, what may render it as a nomen dubium. Therefore, an application was sent to the ICZN to set it aside, and to designate the male described below as neotype, according to Art. 75.5 (Case 3332). Conditions qualifying this material as neotype, especially the evidence that it is consistent on what is known on the species and its probable locality, are shown below. This new specimen will have the advantage of being an adult male, bearing the most valuable taxonomic features (especially the hemispermatophore), and the type locality will become precise. Until a decision is made by the ICZN, the current usage ( NRS holotype) is to be maintained.

Additional material examined. ARGENTINA. Province of San Juan. Parque Nacional El Leoncito, Sierra del Tontal, near 'Portezuelo del Tontal' (3450 m), U.V., 25 NΟvɵmbɵr 2003 (L. Acosta), 1 male ( CDA 000.364).

Description (adult male).

Coloration. General color reddish hazel, ventral side and legs lighter, pectines whitish yellow. Carapace with a dense pigment reticle, leaving a clear depigmented area on the anterior border, between the lateral eyes. Tergites I–VI with two wide paralateral pigmented stripes, leaving a clear median space in between (representing 15.9% of the tergite V width), and narrow clear areas each side; tergite VII with dense paramedian reticles, irregularly connected in the middle. Sternites depigmented. Metasomal segments I–III with a dark median dorsal spot, shield­like, which does not reach the posterior border, but bears three anterior projections; this spot is vestigial on segment IV, as a tenuous reticle with similar arrangement; dorsal side of segment V almost depigmented. Lateral side of segments I–IV with two longitudinal well­defined stripes of dense pigment. The lateral stripe occupies the basal half on segment I, between DSM and DL, while it is almost complete on segments II–IV, extended along DL; on segment V it is faint and reticulate. The ventrolateral stripe, of darker pigment, extends from the VL carina to the lateral side, and is well developed along the entire metasoma; on segments I–III it is separated from the lateral stripe by a narrow space, while a feeble reticle connects these stripes on segments IV– V. Ventromedian line absent on segment I, on segments II–V it is well defined, and remains independent from the lateroventral pigment. Vesicle with faint ventral pigment, a narrow median stripe is separated from the lateral pigmented areas by two clear lines. Chelicerae just with a vestigial reticle. Pedipalp femur dorsally covered by pigment, except for an elongated clear area on the basal half; remaining sides only with faint reticles. Patella with dense reticle on the retrolateral side, and some pigment on the prodorsal and proventral borders. Chela with a large ventral, retrolateral and prolateral spot on the fingers' base, connected to the hand base by several irregular, faint stripes. Legs spotted on the external and dorsal sides (especially femur and patella), other sides clear.

Morphology. Small sized scorpion, with slender and delicate appearance; measurements, see Table 1. Carapace depressed, with very low eye mound, front border straight. Tegument of carapace and tergites I–VII finely granular, acarinate; tergite VII is more granulous and bears four incomplete posterior keels. Sternites I–IV smooth; sternite V granulous, with one pair of paralateral keels on the posterior half. Metasomal segments I– IV. DL keels complete and granulous, in each segment granules are caudally larger and more acute (ending in a posterior larger granule), but carinae become weaker from segment I to IV. LSM complete in segment I; only present on the caudal one third on segment II; just as a smooth tegumentary elevation and a few isolated posterior granules on segment III; lacking on segment IV. LIM complete and conspicuous in segment I, then decreasing suddenly on segment II to just a few posterior granules, and disappearing on segments III–IV. Ventral surface of segment I granulous, VL and VSM well developed and conspicuous (also a granulous area between LIM and VL); on segment II granulation is markedly reduced, VL are just tegumentary borders with very few sparse granules and VSM are not discernible; both VL and VSM are absent on segments III–IV (ventral surface smooth). Metasomal segment V: DL carinae almost lacking, with just very few and inconspicuous basal granules. Lateral surface with LM only insinuated. VL almost complete but somewhat dispersed in an irregular double row in the middle, with large granules alternating with smaller ones. Few sparse granules represent the otherwise lacking VSM. VM complete, more 'regular' than VL, expanded on the posterior end. Telson: vesicle elongated and low, aculeus short. Movable finger of chelicerae with two subdistal teeth. Pedipalps slen­ der and smooth, except for the prolateral face of femur, densely granulous, and a few granules on the prodorsal and proventral borders of the patella. Chela slender, with an acute prolateral apophysis. Trichobothriotaxy according to the genus pattern (as described by Ochoa 2004); Et3 slightly more basal than Est, Esb situated above Eb2. Telotarsal spination on legs I–IV: 1+1, 2+2, 3+3, 3+3. Number of pectinal teeth: 19­19. Hemispermatophore very slender, like in other members of the "species group A" (as recognized by Acosta & Ochoa 2001), the lamina is sharply divided in a straight basal part, and an Scurved apical part (apex); frontal crest along the border of the basal part of the lamina with two portions (proximal oblique and straight distal); a lobular projection each side of the crest at the inflexion point; basal lobe as typical "tortuous" stem, tipped by a delicate distal process (the subdistal "spoon­like" dilatation is suspected to have been damaged during dissection).

Total body length 24.4

Carapace length 3.1

Anterior / posterior width 1.9 / 3.5

Mesosoma length 6.4

Metasoma total length 15.0

Metasomal segment I length / width 1.5 / 1.9

Metasomal segment II length / width 1.8 / 1.7

Metasomal segment III length / width 1.9 / 1.6

Metasomal segment IV length / width 2.4 / 1.5

Metasomal segment V length / width / height 3.4 / 1.4 / 1.2

Telson length / width / height 4.0 / 1.3 / 1.1

Aculeus length 0.8

Pedipalp total length 11.2

Femur length / width 3.0 / 0.8

Patella length / width 2.9 / 1.0

Chela length / width / height 5.3 / 1.4 / 1.4

Movable finger length 2.9 Holotype, juvenile (presumably female). Damaged, only the following parts remain: carapace, mesosoma and caudal segments I–IV, together with left pedipalp trochanter and femur, right I–II legs (leg I without telotarsus), and pectines; metasomal segment V and right pedipalp are loose; all remaining body parts or appendages missing. Pectinal teeth: 15–12 [in the latter it is evident that several teeth are lacking].

Comparisons. Both the external morphology and the hemispermatophore shape place O. bivittatus in the so­called "group A" ( Acosta & Ochoa 2001), which proved to be a monophyletic ensemble ( Ochoa 2004). Within the group, it is closely related to O. alticola .

Similarities concern both the pigment pattern and the external morphology, being difficult indeed to find a sharp morphological discrimination. Only the hemispermatophore provides reliable differences. The fact that just one male of O. bivittatus is hitherto available – i.e. variability remains unknown – lessens to some extent the strength of these conclusions, but the differences encountered, together with the apparent geographical isolation, support the latter being regarded as an independent entity. Whether it represents a separate species or a subspecies (in which case the name should be subordinated to O. alticola ) is probably a useless question. With the taxonomic situation being subtle, both the conditional precedence of alticola and the designation of a neotype for bivittatus are considered valuable nomenclatural tools to ensure stability at different levels. As shown in Fig. 9 View FIGURE 9 , O. alticola is hitherto known from two quite separate areas on the east side of the Andes in western Argentina ( Acosta & Ochoa 2001): surroundings of Puente del Inca, province of Mendoza (type locality), and of Paso del Agua Negra, province of San Juan (referred to as MZA and SJ, respectively). These two populations evidence some slight external differences (see below), but the hemispermatophore morphology is identical. In comparison, the hemispermatophore of O. bivittatus is in overall outline more slender, especially regarding the basal part of the lamina ( Figs. 6 View FIGURES 6 – 7 –8). Other differences are recorded in the partial key below. O. bivittatus seems to be smaller, with total length (24.4 mm) below the size range of O. alticola (MZA: 26.9–31.5 mm, mean= 28.7 mm, SJ: 27.1–31.5 mm, mean= 28.9 mm); females reach 34.2 mm in MZA and 37.5 mm in SJ. To insert O. bivittatus in the key provided by Ochoa (2004), the very last couple should be modified, as follows:

7. Sternite V granous, carinae not discernible. Ventral side of metasomal segment V covered by dense granulation that hides carina VM. Legs III–IV with 3+4 telotarsal spines. Ventral pigment of metasoma: axial stripe joins distally the ventrolateral pigment on segments I–III (not joining on segments IV–V) ........................................... O. atiquipa

– Sternite V little granulous, with 2–4 carinae. Ventral side of metasomal segment V without dense granulation, carina VM well defined. Legs III–IV with 3+3 telotarsal spines. Ventrolateral and ventro­axial pigment stripes independent along the entire metasoma ......................................................................................................................8

8. Hemispermatophore: apex reduced, it represents only 38% of the lamina length; front crest almost not surpassing its connection to the apex, and without lobular expansion at the inflexion point. Metasomal segment II with VSM carinae. Metasomal segment IV with six VSM macrosetae. Total length (males): 27–31.5 mm ................. O. alticola

– Hemispermatophore: apex larger, 47% of the lamina length; front crest surpassing its connection to the apex, forming in lateral view a 'spur­like' projection (notch in between with slightly different curvature: Figs. 6 View FIGURES 6 – 7 –8), and with lobular expansions at the inflexion point. Metasomal segment II without VSM carinae. Metasomal segment IV with eight VSM macrosetae. Total length (male): 24.4 mm ................. O. bivittatus In other features, currently employed in the species­level taxonomy of Orobothriurus ( Acosta & Ochoa 2001) , the single specimen O. bivittatus fits within the variability range of O. alticola :

Frequencies of the number of pectinal teeth.— O. bivittatus (19­19). MZA males (n=12 pectines): 18 teeth (2 pectines), 19 (2), 20 (6), 21 (2); females (n=11): 15 (7), 16 (4); SJ males (n=16 pectines): 19 teeth (7 pectines), 20 (5), 21 (4); females (n=16): 15 (1), 16 (5), 17 (9), 18 (1).

Number of VSM macrosetae on metasomal segment I.— This feature shows the most noticeable difference between the two populations of O. alticola . MZA: 3+3: 10 specimens (83.3%), 3+2: 2 specimens (16.7%); SJ: 3+3: 4 specimens (25.0%), 3+2: 3 spec. (18.7%), 2+2: 9 spec. (56.2%). The single available O. bivittatus has 3+3 setae.

Telson, length/height ratio.— O. bivittatus (3.64). MZA males (n=3): 3.1–3.8, females (n=3): 3.1–3.2; SJ males (n=6): 3.8–4.2 (mean=3.9), females (n=8): 2.8–3.3 (mean=3.0).

Pedipalp chela, length/width ratio.— O. bivittatus (3.9). MZA males (n=3): 3.3–3.6, females (n=3): 3.4–3.7. SJ males (n=6): 3.5–4.2 (mean=3.8), females (n=8): 3.3–3.5 (mean=3.4).

Relative width of the median clear stripe.— O. bivittatus (15.9% of the width of tergite V). MZA: 14.4–19.3% (mean=15.9%), n=8; SJ: 11.1–16.1% (mean=14.5%), n=15.

Type locality. The type specimen is said to come from "San Juan", without further detail. This material was sent to Thorell by the Dutch zoologist Hendrik Weyenbergh, together with other arachnids collected 'around Córdoba and San Juan' ( Thorell 1877b, 1878). In addition to " Cercophonius brachycentrus var. bivittatum ", Thorell (1877a) described other four scorpion species on that material, and two harvestmen and one pseudoscorpion were added in a further publication ( Thorell 1877b, 1878). The place of origin given in some cases was questioned, and some confusion between these two localities is to be suspected. Despite Thorell's (1877b, 1878) statement that all specimens were collected by Weyenbergh himself, those from San Juan were actually obtained by the botanist Saile Echegaray. As Hieronymus (1881) complained, Weyenbergh never was in San Juan, and the mistaken statement of Thorell (1877b, 1878) was said to be a 'printer's error'. This fact might have contributed to the confusion of labelling, but at the same time gives additional evidence to our case, as we will see. The species with presumably wrong localities are:

Telegonus weijenberghi Thorell 1877a: 173 ( Scorpiones View in CoL , Bothriuridae View in CoL ; currently under Brachistosternus Pocock 1893 ). Supposedly collected at "Córdoba". The species was never found there ( Acosta 1989, Acosta & Rosso de Ferradás 1996), while, in contrast, it was recorded in localities from Western and Northwestern Argentina ( Ojanguren Affilastro 2002), among them several sites in province of San Juan.

Cercophonius brachycentrus Thorell 1877a: 180 ( Scorpiones View in CoL , Bothriuridae View in CoL ; currently under Urophonius Pocock View in CoL ). The type series comprises two specimens: an adult male is stated to be from "San Juan", and a juvenile from "Córdoba". The latter is correct, but the male is probably mislabeled. This species is widely distributed in central Argentina, being quite common in Córdoba, but was never found in San Juan ( Maury 1977, Acosta & Rosso de Ferradás 1996).

Pachylus butleri Thorell 1877b: 207 View in CoL ( Opiliones View in CoL , Gonyleptidae View in CoL , currently under Pachyloidellus Müller 1916 View in CoL ). From "San Juan". This species is not found there, but is very common and frequently collected in Córdoba instead ( Acosta 1993a).

Meanwhile, the type localities of Isometrus fuscus Thorell 1877 (Córdoba) , Telegonus ferrugineus Thorell 1877 (Córdoba) and Ostracidium pertyi Thorell 1877 View in CoL (Córdoba) are consistent with their known range, and thus deemed to be correct ( Abalos 1953, Maury 1974, Acosta 1989, Acosta 1993b, Acosta & Rosso de Ferradás 1996). Species from Córdoba can easily be assumed to have been collected in the surroundings of the city, in those times little more than a small village. Urophonius brachycentrus View in CoL , Pachyloidellus butleri View in CoL , Brachistosternus ferrugineus , Neopucroliella pertyi View in CoL are still occasionally collected in the city suburbs, while Zabius fuscus View in CoL can be caught in sites less than 15 km from the center ( Acosta 1989, 1993a, 1993b). In contrast, the exact collecting sites in 'San Juan' seem not as easy to determine, since neither Brachistosternus weijenberghi nor any Orobothriurus View in CoL species exist in the 'surroundings' of the capital city ( Roig Alsina & Maury 1981, Ojanguren Affilastro 2002, Acosta & Ochoa 2001). The right answer should be searched in the itinerary of the collector, Saile Echegaray, in his botanical trip in this province.

Echegaray (1878) traveled to San Juan in November 1875. His excursion was targeted to the locality of "Leoncito", today best known as "Estancia El Leoncito", which is now partially embraced in the Parque Nacional El Leoncito. It was an extensive farm, whose main settlement can still be seen on the base of the western slopes of the Sierra del Tontal, at about 2300 m. This mountain belongs to the Precordillera orographic system and reaches over 4000 m a.s.l. In his report, Echegaray (1878) indicates he visited the 'Cerro Tontal' where he collected many plant samples. At the present day there is no practicable road crossing this range, but surprisingly enough, in Echegaray's times the so called 'road of Tontal' was the only available communication between the city of San Juan and El Leoncito. This road, abandoned long ago, crosses the mountain at the pass known as 'Portezuelo del Tontal' or 'Portezuelo de la Virgen', at 3640 m. Taking all the evidence together, the most plausible locality for Thorell's (1877a) scorpions collected in 'San Juan' appears to be 'somewhere in the Sierra del Tontal'. Against that reasoning, Roig­Juñent et al. (2003) stated (as a 'prediction' of their analysis) that the scorpion genus Orobothriurus does not occur in the Precordillera; but as seen, this is not supported by the facts. Therefore I hereby restrict the type locality of Cercophonius brachycentrus bivittatus (and also of Telegonus weijenberghi ) to a so far undetermined site along the old road on the Sierra del Tontal, at least above 3000 m.

Zoogeographic comments. Orobothriurus bivittatus is likely a high­altitude endemic in the Sierra del Tontal. This mountain continues southerly into the Sierra de Uspallata, province of Mendoza ( Fig. 9 View FIGURE 9 ), which is a part of the Precordillera, too. Both chains are separated from the Andes by the "Uspallata­Calingasta" tectonic depression, a xeric, N­S oriented 'valley' composed by two adjacent basins ( Fig. 9 View FIGURE 9 : Ca, Us), with watershed at around 2200 m. The Uspallata­Calingasta valley is covered by Monte (sub­Andean) vegetation ( Martinez Carretero 1995). Though being quite narrow (50–100 km), it likely represents an effective barrier for low vagility high­Andean elements (Roig Juñent et al. 2003). At the Sierra del Tontal the Monte ascends the west­faced slopes, reaching as high as 2800–3000 m (e.g., at Pampa del Jarillal); at least on the path to Portezuelo del Tontal, pure grasslands only appear above 3200 m (Acosta, pers. obs.). In general, the upper regions of the Tontal and Uspallata ranges should be ascribed to the Puna vegetation ( Martinez Carretero 1995), but the most elevated sites of the former show many high­Andean elements, even with a marked ecotonal character (E. Martínez Carretero, in litt. 2004). Grasslands of the Sierra del Tontal are just 60 km away from the Andes, and this isolation might explain the hemispermatophore differences between the close relatives O. alticola and O. bivittatus . In contrast, the two populations of O. alticola (MZA­SJ), though separated by 280 km, are very probably continuous along the intricate Andes eastern slope ( Fig. 9 View FIGURE 9 ), and thus their hemispermatophores do not show any divergence. Since differences between alticola and bivittatus are small, a relatively recent separation is supposed. Past fluctuations of the altitudinal belts, in which the high­altitude vegetation might have lowered its limit in colder/more humid periods, would have connected the Andes and the Precordillera; in such case, the continuity of the ancestor range would have been enabled along these two mountain regions, being then split during a retraction phase. Palynological studies made by Markgraf (1983) show that a locality at 2000 m in the Uspallata­Calingasta depression had a predominance of graminous vegetation between 5,000 and 4,000 yr B.P., decreasing thereafter, to give place to present Monte elements. This scenario contradicts the presumed unrelatedness of the Andes and the Precordillera, as proposed by Roig Juñent et al. (2003). These authors mention the evidence of several tenebrionid beetles, which are endemic to the Andes (e.g. Falsopraocis ) but do not occur in the Precordillera at the same latitude. Their results, however, might have been biased by the scarce information on Andean and Precordilleran species considered in their analysis. Since the arthropod fauna of the Sierra del Tontal is poorly known, it is highly advisable to re­analyze the Andes­Precordillera links by including new information from this neglected range.

Considering the lowest records in Argentina (2450 m for O. famatina, 2700 m for O. alticola ), Orobothiurus would be expected to exist in the Sierra de Uspallata. But despite repeated sampling efforts, no species of this genus has hitherto been found there. It is worth noting that the Sierra de Uspallata only slightly surpasses 3000 m at its highest elevation, and this altitude is not continuous with the Sierra del Tontal, but a lower area (at ~ 2700 m) separates the upper portions of the two ranges. All known Argentinean records of Orobothriurus ( Maury 1976, Acosta & Ochoa 2001) originate from mountains whose maximal altitude reaches or surpasses 3500 m.


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Orobothriurus bivittatus (Thorell 1877)

Acosta, Luis E. 2005

Orobothriurus alticola:

Acosta 2002: 177

Urophonius brachicentrus bivittatus: Mello­Leitão 1939 : 612

Roig 1973: 200
Abalos 1959: 592
Mello-Leitao 1939: 612

Urophonius brachycentrus bivittatus: Mello­Leitão 1931 : 99

Lowe 2000: 44
Acosta 1998: 559
Mello-Leitao 1931: 99

Cercophonius brachycentrus

Thorell 1877: 183

Telegonus weijenberghi

Thorell 1877: 173

Cercophonius brachycentrus

Thorell 1877: 180

Pachylus butleri

Thorell 1877: 207
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