Pseudouroctonus peccatum, a new scorpion from the Spring Mountains near “Sin City,” Nevada (Scorpiones, Vaejovidae)

Abstract A new scorpion species is described from the Spring Mountain Range near Las Vegas, Nevada. The new species appears to be geographically isolated from other closely related species of Uroctonites Williams & Savaryand Pseudouroctonus Stahnke. We tentatively place the new species in Pseudouroctonus and provide detailed descriptions and illustrations of type material. We compare the new species to 17 congeneric taxa, briefly discuss the taxonomic history of Pseudouroctonus, and provide DNA barcodes for two paratypes to assist ongoing research on the systematics of family Vaejovidae.


introduction
Low dispersal potential and ecological specialization (stenotopy) are thought to make certain groups of scorpions predisposed to accelerated diversification (Prendini 2005;Bryson et al. 2013a). Scorpions restricted to highland ecosystems are particularly diverse, perhaps resulting from allopatric divergence on small spatial scales (microallopatry, see Fitzpatrick et al. 2008) facilitated by historical changes in geomorphology and climate regimes (Bryson et al. 2013a(Bryson et al. , 2013b. Recently, this hypothesis has been repeatedly supported by the discovery of numerous new scorpion species from isolated mountain ecosystems, especially from the "sky islands" region of the North American aridlands (Graham 2007;Ayrey 2009Ayrey , 2012Graham and Bryson 2010;Ayrey and Soleglad 2011;Hughes 2011;Graham et al. 2012;Sissom et al. 2012;Ayrey and Webber 2013).
The Spring Mountain Range, located just outside of Las Vegas in southern Nevada, is among the most insular of the sky islands, reaching elevations more than 3,400 m above the Mojave Desert lowlands. While conducting diurnal surveys for myriapods in the Spring Mountains, we serendipitously discovered yet another new scorpion that appears to be restricted to a sky island ecosystem. After numerous diurnal and nocturnal (using UV light;Stahnke 1972) surveys, we only managed to collect a total of five individuals from mixed pine-oak woodlands in Kyle Canyon, one of the most heavily visited regions in the Spring Mountains. Unfortunately, forest fires ravaged the type locality shortly after we collected the type series and surveys in other areas of the mountains were unsuccessful.
The new species is clearly a member of family Vaejovidae, and is most similar to genera Pseudouroctonus and Uroctonites, both of which are stenotypic and contain species endemic to sky island ecosystems in southwestern North America. Interestingly, the Spring Mountains are situated in the middle of a substantial gap between the known distributions of these two genera ( Fig. 1), so the new species could prove to be a missing link in our understanding of the biogeography of this group (Bryson et al. 2013a) and the southwestern sky islands. Herein, we tentatively place the new species in Pseudouroctonus, although we predict that the genus is polyphyletic and in need of a thorough systematic revision.
Since the population at the type locality may have been extirpated during recent fires, we provide DNA barcodes (COI) for two specimens (paratypes) to assist colleagues in their ongoing research on the biogeography and systematics of family Vaejovidae. Given that the species went undetected for so long despite occurring in a populated region near one of the most visited cities in the world, we suspect that similar new species may still await discovery in the more remote and less-explored sky islands of southern Nevada and California.
Brief taxonomic history. Of the 22 species and subspecies currently comprising genera Pseudouroctonus and Uroctonites (including the new species described herein), sixteen were described by Gertsch and Soleglad (1972). At that time, twelve of these species were placed in genus Uroctonus (now in family Chactidae) and the other four in genus Vaejovis. Stahnke (1974) moved most of the species placed in Uroctonus into genus Vaejovis and created the new genus Pseudouroctonus solely for P. reddelli. Stockwell (1992) reversed most of Stahnke's taxonomic acts by moving the species Stahnke placed in Vaejovis into Pseudouroctonus. In their important paper, Williams and Savary (1991) defined the new genus Uroctonites comprised of a new species, U. giulianii, and three Pseudouroctonus species originally defined by Gertsch and Soleglad (1972). Finally, four other species have now been placed in Pseudouroctonus: P. m. minimus (Kraepelin, 1911), P. glimmei Hjelle, 1972, P. sprousei Francke & Savary, 2006, and P. saavasi Francke (2009. See Soleglad and Fet (2003:103-104) for a more detailed discussion on the taxonomic history of these interesting scorpions.
Acronyms of depository.-AMNH, American Museum of Natural History, New York, New York, USA; MRG, personal collection of Matthew R. Graham, Willimantic, Connecticut, USA.

Molecular analysis
We extracted total genomic DNA from leg tissue from the left side of the two female paratypes using a DNeasy Extraction Kit (Qiagen Inc.). A portion of the cytochrome oxidase subunit I (COI) gene, which is used for barcoding, was amplified with forward primer COI_modF (5' -ATCATAAGGATATTGGGACTATGT -3', Bryson et al. 2013) and reverse primer LE1r (5' -GTAGCAGCAGTAAARTARGCYCGAGTATC -3', Esposito 2011). Double-stranded cycle sequencing was performed using the same primers and the Big Dye Terminator v. 3.1 Cycle 6 Sequencing Kit (Applied Biosystems). The COI sequences were submitted to the Barcode of Life Data system (BOLD, Ratnasingham and Hebert 2007), and GenBank (Accession Nos. KF841448 & KF841449). Etymology. The specific epithet is Latin for "sin" in reference to the proximity of the type locality to Las Vegas, which is known informally as "Sin City."
Description of holotype. Color: Carapace, trochanter, femur, patella, tergites, and metasoma have a yellow-orange base color with dark brown to black markings along the carinae of the pedipalp and metasoma. Legs are light yellow. Pedipalp chelae are dark brown in color with darker reddish-brown coloration at the anterior portion of the palm where the fixed finger and movable finger meet. Chelicerae are light yellow on proximal half with dark reddish-brown fingers. Vesicle portion of the telson is yellow-orange with a dark reddish-brown to black aculeus. Pectines and genital operculum are light yellow.
Morphology: Carapace: trapezoidal with noticeably emarginated anterior margin; surface finely granular with scattered small granules, with larger granules symmetrically flanking the lateral and median eyes; median furrow is slight and traverses length of carapace; ratio of location of median eyes location (from anterior edge)/carapace length = 0.338. Tergites: surface with small granules on distal 1/3-1/2 of tergites I-VI; tergite VII with two pairs of granular lateral carinae, and a slight median hump. Sternites: III-VI smooth to very finely granular and without carinae; VII with granular ventral lateral carinae on posterior 4/5, median carinal pair essentially obsolete. Spiracles: ellipsoid and with median side rotated 40° away from posterior sternite margin. Genital Operculum: sclerites separated on posterior 1/5. Pectines: tooth count 13/13; middle lamellae 8/8; sensorial areas present on all Chelicerae: dorsal edge of fixed finger with four teeth, one distal, one subdistal, one median, and one basal, the latter two denticles formed as a bicuspid; ventral edge with seven low-profile pigmented protuberances, the distal two smaller in size; dorsal edge of movable finger has five teeth total comprised of one distal, two subdistal, one median tooth, and one basal tooth; ventral edge of movable finger has seven small pigmented crenulated teeth; serrula with approximately 23 tines. Pedipalps: trichobothrial pattern type C, orthobothriotaxic: trichobothria ib-it positioned on extreme base of fixed finger, Dt located considerably basal of palm midpoint, Db ventral of digital carina, patellar trichobothria v 3 adjacent to et 3 ; ratio of chela length/width 3.57; femur length/width 2.60; patella length/width 2.79; fixed finger length/carapace length 0.78. Chela: median denticles (MD) of fixed finger aligned and divided into six subrows by five outer denticles (OD); flanked by six inner denticles (ID); movable finger with six subrows of MD, five OD and seven ID. Chela carinae: Digital carina rounded, rough, and somewhat flattened; subdigital essentially obsolete, formed by two granules; dorsosecondary flat, rounded, and roughly textured; dorsomarginal very rounded, with large scattered granules; dorsointernal rounded, with scattered granules; ventroexternal rounded, roughly textured, terminating at external condyle of movable finger; ventromedian flat, essentially obsolete; ventrointernal rounded, with small granules scattered distally; external carina very rounded, roughly textured. Femur: dorsointernal, and ventrointernal carinae denticulate and black in color, ventroexternal and dorsoexternal carinae denticulate with small granules throughout, internal surface has 6 prominent dentate granules. Patella: dorsointernal carinae are denticulate, dorsoexternal carinae are mildly crenate, ventral internal carinae are dentate, ventroexternal carinae are moderately denticulate, internal surface has 11 prominent granules. Legs: Ventral surface of tarsus with single median row of 7-17 spinules terminating distally with one to two pairs of spinules. The terminal spinules are slightly stouter than the those comprising the median row. Flanking setal pairs are essentially absent in legs I-II, with 2-3 irregularly positioned and sized pairs on legs III-IV. Basitarsus spinule rows are limited, 2 rows on leg I, 1 row on leg II, 1 weak row on III, and absent on IV. Basitarsus populated with large irregularly placed darkly pigmented setae. Hemispermatophore: Left hemispermatophore is 5.7 mm in length; lamina length 3.71, Figure 16. Pseudouroctonus peccatum sp. n. female holotype, Spring Mountains, Clark Co., Nevada, USA. Trichobothrial pattern. lamellar hook length 1.03, and trough different (vertical distance between ventral and dorsal troughs) 0.55. Lamellar edges sub-parallel, except for slight expansion on mid-area of the internal edge; terminus blunted with a distinct distal crest on the dorsal side. Lamellar hook extends somewhat from lamina base, is distinctly bifurcated, and is formed entirely from the dorsal trough. A modest basal constriction and a deep truncal flexure are present. Sclerotized mating plugs with smooth barbs were extracted from the ventrointernal aspect of both hemispermatophore median areas. DNA barcodes (COI) -MRG1221 (paratype, GenBank no. KF841448):    TATGTTTCATTCTGGGGGGTCTGTTGATATGACTATTTTTTCGT-TACATTTGGCTGGTGTTTCTTCAATTTTAGGAGCTATTAATTTTAT-TACTACTATTTTGAATATGCGAAGATCTGGAATATTGTTGGAGCGTG-TGCCTTTATTTGTATGGTCTGTTAAGATTACTGCTATTCTTCTGTT-GTTGTCTCTTCCAGTTCTTGCGGGTGCAATTACTATGCTATTAACA-GATCGAAATTTTAATACTTCTTTTTTTGATCCAGCGGGTGGAGGG-GATCCTATTTTGTACCAACATTTATTTTGATTTTTTGGTCATCCTGAG-GTTTATATTTTAATTCTTCCGGGATTTGGAATGATTTCTCATATTATT-AGTCATCATACTGGGAAGAGGGAACCTTTCGGAGCTTTAGGAATGATT-TATGCTATGGTGGCTATTGGGTTTTTGGGTTTTGTGGTTTG. MRG1222 (paratype, GenBank no. KF841449):

Discussion
The adult male and female can be differentiated by the larger pectinal tooth counts in the male (15 versus 13-14), the completely separated genital operculum in the male and the presence of genital papillae (in the female the sclerites are only separated on the posterior one-quarter and papillae are absent). The adult female is larger in size, 52 mm versus 36 mm. The metasoma of the male is slightly thinner than in the female, exhibiting the following percentage differences for all five segments when the segment's length is compared to its width (2.4-10.8%).
On the dorsal edge of the right cheliceral movable finger of the female holotype, a small bifurcation is present on the distal aspect of the median (m) denticle (see Fig.  10). This bifurcation is not present on the left chelicerae, so we consider it an anomaly.

Distribution
Known only from the type locality in the Spring Mountains of Southern Nevada where it was collected at an elevation of 2,103 m. Soleglad and Fet (2008: fig. 196) considered Uroctonites and Pseudouroctonus to form a distinct clade within the vaejovid subfamily Vaejovinae. Pending results from detailed morphological and molecular analyses, we place Pseudouroctonus peccatum sp. n. in this group based on the following characters: (1) the chelae are thick with swollen palms that are somewhat flat in appearance due to the weak to obsolete development of the dorsosecondary and ventromedian carinae; (2) the carapace exhibits a conspicuous anterior emargination; (3) the median eyes are reduced in size and located considerably anterior of the carapace midpoint; (4) the ventral edges of the cheliceral movable finger and fixed finger are equipped with small crenulations and protuberances, respectively; these two characters are found in many species of this group and likewise generally absent in the other genera comprising the subfamily (Vaejovis and Franckeus); (5) the serrulae are well-developed; (6) the pectinal tooth counts as compared to the scorpion's adult size are relatively small.

Comparison to similar species
Within the clade, P. peccatum clearly has a closer affinity to Pseudouroctonus than Uroctonites. The sides of the hemispermatophore lamina are sub-parallel (not tapered), the terminus is truncated (not pointed); lamellar hook is located distal of dorsal trough (not adjacent to), and the terminus is bifurcated (not intact). The mating plug is sclerotized (not partially gelatinous). Ventral setal pairs of the leg tarsus are irregularly positioned and sized, and of medium development (not aligned, the same size, and stout). Although the relative pectinal tooth counts in this species are somewhat small, they are not as small as seen in Uroctonites. For example, P. peccatum and U. huachuca are similarly sized species, but P. peccatum has 67% (females) and 76% (males) more teeth than U. huachuca. Pectinal tooth counts in the four species of Uroctonites range 7-10 in females and 8-10 in males.
Pseudouroctonus is comprised of eighteen species (including P. peccatum). The new species can be separated from the other species based on the structure of its hemispermatophore, cheliceral and chelal dentition, pectinal tooth counts, and morphometrics of the fifth metasomal segment (see Table 2 for character comparisons across all species). Before addressing each of the seventeen species, we must point out that P. peccatum has a distal crest on the hemispermatophore lamina terminus and its lamellar hook is somewhat removed from the lamina base, providing a small basal constriction. Both of these characters are unknown from any of the hemispermatophores so far reported for this genus [note: we have information on the hemispermatophore for fifteen Pseudouroctonus species, only three are unknown. See Williams and Savary (1991: figs 21-29), Francke and Savary (2006: figs 15-21), Soleglad and Fet (2008: figs 67-69), and Francke (2009: figs 2-4)]. Although it is clear, based on Table 2, that more than one diagnostic character is available for separating P. peccatum from the other species, we will restrict our discussion to discrete characters thus minimizing the dependence on meristic and morphometric data. Pseudouroctonus peccatum does not have a secondary hook on the hemispermatophore as found in P. williamsi, P. angelenus, P. bogerti, P. glimmei, and P. iviei. Although P. peccatum is equipped with crenulated denticles on the ventral edge of the cheliceral movable finger, as well as small protuberances on the venter of the fixed finger, they are not enlarged and tooth-like as found in P. reddelli, P. sprousei, and P. cazieri. The lamellar hook on the hemispermatophore of P. peccatum is distal from the dorsal trough, whereas in P. lindsayi it is adjacent. Pseudouroctonus peccatum has two subdistal (sd) denticles on the cheliceral movable finger dorsal edge, whereas the cave adapted species P. saavasi has only one. Pseudouroctonus peccatum has seven inner denticles (ID) on the chelal movable finger, whereas P. andreas has only six. As expected given its somewhat large size, P. peccatum has a relatively large pectinal tooth count (i.e., 15 male and 13-14 female), separating it from P. chicano, P. apacheanus, and P. rufulus which range from 10-11 in males and 9-10 in females. Although P. peccatum has a relatively stout metasomal segment V, it is not as robust as that found in P. minimus minimus, P. minimus castaneus, and P. minimus thompsoni. Segment length/width ratios are 1.908 for the female holotype and 1.953 for the male paratype, compared to 1.364-1.565 in females and 1.402-1.667 males for the P. minimus subspecies.
Interestingly, P. peccatum was not found within the known range of any of the Pseudouroctonus species, and was discovered closer to two species of Uroctonites, U. giulianii and U. sequoia; the distances between the type localities are roughly 258 and 282 km, respectively. The most geographically proximate species of Pseudouroctonus are all found in southern California: all three subspecies of P. minimus, P. angelenus, P. bogerti, P. williamsi, and P. andreas. The distance from these type localities ranges 290-426 km. Based on Table 2, P. peccatum appears more closely related to P. andreas, the smallest species in the genus, and the three subspecies of P. minimus. The other Pseudouroctonus spp. (P. angelenus, P. bogerti, and P. williamsi) exhibit considerable differences in the hemispematophore structure.