Systematics of the keyserlingii Group of Diplocentrus Peters, 1861 (Scorpiones: Diplocentridae), with Descriptions of Three New Species from Oaxaca, Mexico

ABSTRACT The scorpion genus Diplocentrus Peters, 1861, comprising more than 50 species, most of which are endemic to Mexico, is the most diverse in the family Diplocentridae Karsch, 1880 (Santibáñez-López et al., 2011). Hoffmann (1931) divided the Mexican species into two groups, the whitei group and the keyserlingi group, based largely on differences in size and coloration. Francke (1977) redefined these groups. The whitei group, renamed the mexicanus group because it included the type species of the genus, comprised species with short cheliceral fingers and the pedipalp femur wider than high. The keyserlingii group comprised species with long cheliceral fingers and the pedipalp femur higher than wide. Several new species of Diplocentrus were since described, but no attempt was made to synthesize the taxonomy of the species assigned to either group or further clarify the validity of the groups. In the present contribution, the species of Diplocentrus with the pedipalp femur higher than wide are reviewed. An operational diagnosis is provided for the keyserlingii group. Diplocentrus formosus Armas and Martín-Frías, 2003, previously synonymized with Diplocentrus tehuano Francke, 1977, is reinstated. Revised, updated diagnoses are provided for all previously described species and three new species, Diplocentrus kraepelini, n. sp., Diplocentrus sagittipalpus, n. sp., and Diplocentrus sissomi, n. sp., are described. The female of Diplocentrus mitlae Francke, 1977, is described for the first time. A dichotomous key is provided for identification of the 10 species in the keyserlingii group.


INTRODUCTION
The scorpion genus Diplocentrus Peters, 1861, comprising more than 50 species, most of which are endemic to Mexico, is the most diverse in the family Diplocentridae Karsch, 1880 (Santibanez-Lopez et al., 2011). Hoffmann (1931) divided the Mexican species into two groups, the whitei group and the keyserlingi group, based largely on differences in size and coloration. Francke (1977) rede¬ fined these groups in a key to identification of the Diplocentrus species occurring in the Mexican state of Oaxaca. The whitei group, renamed the mexicanus group because it included the type species of the genus, Diplocentrus mexicanus Peters, 1861, comprised species with short cheliceral fingers and the pedipalp femur wider than high. The keyserlingii group comprised species with long che¬ liceral fingers and the pedipalp femur higher than wide. Francke (1978) realized that this distinction was problematic, however, because the diagnostic characters of the pedipalp femur were also used to separate other genera in subfamily Diplocentrinae Karsch, 1880. Several new species of Diplo¬ centrus were since described (e.g., Stockwell, 1988;Sissom, 1994;Armas and Martfn-Frias, 2000;Santibanez-Lopez et al., 2011), but no attempt was made to synthesize the taxonomy of the species assigned to either group or to further clarify the validity of the groups.
In the present contribution, the species of the keyserlingii group of Diplocentrus are reviewed ( fig. 1). An operational diagnosis is provided for the group, but its monophyly is not assumed, pending further investigation of phylogenetic relationships within the genus. Diplo¬ centrus formosus Armas andMartfn-Frfas, 2003, previously synonymized with Diplocentrus tehuano Francke, 1977, is reinstated. Revised, updated diagnoses are provided for all previously described species and three new species, Diplocentrus kraepelini, n. sp., Diplocentrus sagittipal¬ pus, n. sp., and Diplocentrus sissomi, n. sp., are described. The female of Diplocentrus mitlae Francke, 1977, is described for the first time. A dichotomous key is provided for identification of the 10 species in the keyserlingii group. Scorpions were collected mostly at night with ultraviolet (UV) light detection . Fossorial species of Diplocentrus were captured doorkeeping at their burrow entrances, by snatching them with forceps. When attempts to snatch individuals retreating into their burrows were unsuccessful, burrow locations were marked and the burrows excavated the following day.
Material is deposited in the following collections: American Museum of Natural History, New York (AMNH), with tissue samples stored in the Ambrose Monell Cryocollection (AMCC); Natural History Museum, London, UK (BMNH); Coleccion "Luis F. de Armas," Instituto Tecnologico del Valle de Oaxaca, Mexico (CALA); Coleccion Nacional de Aracnidos, leg telotarsi (tarsomeres), counts of which have long been used as species-level diagnostic char¬ acters in Diplocentridae, were incorrectly referred to as "spines" by some authors (e.g., Francke, 1977;Armas and Martin-Frias, 2003;Francke and Ponce Saavedra, 2005) prior to Francke and Quijano-Ravell (2009). Lamoral (1979) first pointed out that these articulated structures are setae, rather than spines or spinules (fixed cuticular projections), an observation that was later corrobo¬ rated (e.g., Williams and Savary, 1991;Prendini, 2000;Me West, 2009). Spiniform macrosetae on the leg basitarsi, informative in the systematics of Scorpionidae Latreille, 1802 (Prendini et al., 2003), were not previously studied in Diplocentridae. The configuration of spiniform macrosetae on the basitarsi of the third and fourth legs is informative at the generic level in Diplocentridae and within the Diplocentrus, providing a diagnostic character for the keyserlingii group ( fig. 2).
Diplocentrus hoffmanni resembles D. keyserlingii, D. kraepelini, n. sp., and D. sissomi, n. sp., in adult size and coloration but can be distinguished as follows. The pedipalp patella ventro¬ median carina (d) is weakly developed to obsolete, the pedipalp chela manus, dorsal surface (9) weakly reticulate, and the digital carina (d)  to the presence of stones in the soil matrix ( fig. 1A). The area where this species was collected was heavily disturbed, but there were remnants of oak forest. The habitat and habitus of D.
Hemispermatophore: Lamelliform, weakly sclerotized ( fig. 9B); total length, 6.5 mm; distal lamella, length, 3.5 mm; capsular region, width, 1.6 mm; median lobe narrow, margin entire. Distribution: Diplocentrus kraepelini, n. sp., is known only from the type locality in the San Cristobal Suchixtlahuaca municipality of Oaxaca ( fig. 3A). Ecology: This species was observed doorkeeping at burrow entrances at night with UV detection, and was excavated during the daytime. The burrows, constructed at an angle of ca.
30° to the ground surface, were ca. 30 cm long, and mostly straight with some turns around stones in the soil matrix. The dominant vegetation in the area was oak forest. An undetermined species of Centruroides Marx, 1890, related to C. nigrovariatus, Vaejovis dzahui Santibanez-Lopez and Francke, 2010, and an undetermined species of Vaejovis were collected in sympatry.
Diplocentrus mitlae resembles D. rectimanus and D sagittipalpus, n. sp., in adult size and coloration but can be distinguished as follows. The pedipalp chela dorsal surface is smooth (d, 9) in D. mitlae but reticulate (d) or granular (9) in D. rectimanus, and granular-reticulate (d) or granular (9) in D. sagittipalpus, n. sp. The pedipalp chela digital carina (d) is weakly developed in D. mitlae but strongly developed in D. rectimanus and D. sagittipalpus, n. sp. The counts of spiniform macrosetae on the telotarsi of legs III and IV are lower (5/5:5/5) in D.
Description of the Female: The original description of D. mitlae was based on the holotype male, and the female remained unknown until now.
Diplocentrus rectimanus resembles D. mitlae and D. sagittipalpus, n. sp., in adult size and coloration but can be distinguished as follows. The pedipalp chela dorsal surface is reticulate (8) or granular ($) in D. rectimanus but smooth (8, 9) in D. mitlae, and the counts of spiniform macrosetae on the telotarsi of legs III and IV are higher (6/6) in D. rectimanus than in D. mitlae (5/5). The base coloration is brown to pale brown in D. rectimanus but reddish to ferruginous in D. sagittipalpus, n. sp., and the pedipalp patella dorsoexternal carina is obsolete in D. rectimanus but moderately developed and crenulate to weakly granular in D. sagittipalpus, n. sp.
Metasoma: Metasomal segments I-V, dorsal intercarinal surfaces moderately to weakly granular anteriorly on segments I-III, weakly granular to smooth on IV and V; lateral inter¬ carinal surfaces moderately to weakly granular on I-III, moderately granular or granular-retic¬ ulate on IV and V; ventral intercarinal surfaces smooth to shagreened on I-IV, sparsely granular on V. Segments I-IV, dorsolateral carinae obsolete to weakly developed, granular (d) or weakly granular (9); lateral supramedian carinae weakly to moderately developed, granular on I-III, weakly developed, granular on IV; lateral inframedian carinae weakly to moderately developed, granular to slightly crenulate on I-III, weakly developed, granular on IV; ventrolateral carinae strongly developed, granular to crenulate on I-III, weakly to moderately developed, granular to crenulate on IV; ventrosubmedian carinae strongly developed, granular to crenulate on I-III, weakly to moderately developed, slightly granular to crenulate on IV. Segment V length:pedipalp femur length ratio, 1.28 (d) 9C); total length, 7.5 mm; distal lamella, length, 3.9 mm; capsular region, width, 1.6 mm; median lobe narrow, margin crenulate. orange (9); tergites moderately (d) to densely (9) infuscate; sternites orange to pale orange.