Thorellius atrox Soleglad & Fet, 2008

Soleglad, Michael E. & Fet, Victor, 2008, Contributions to scorpion systematics. III. Subfamilies Smeringurinae and Syntropinae (Scorpiones: Vaejovidae), Euscorpius 71 (71), pp. 1-115 : 94-96

T. atrox (Hoffmann, 1931) , stat. nov., comb. nov.

T. cisnerosi (Ponce Saavedra et Sissom, 2004) , comb. nov.

T. cristimanus (Pocock, 1898) , stat. nov., comb. nov.

T. intrepidus (Thorell, 1877) , comb. nov.

T. occidentalis (Hoffmann, 1931) , comb. nov.

T. subcristatus (Pocock, 1898) , comb. nov.

Distribution. Mexico (Aguascalientes, Colima, Guerrero, Guanajuato, Hidalgo, Jalisco, Mexico, Michoacán, Nayarit, Oaxaca, Puebla, Querétaro, Veracruz, Zacatecas).

Genus Thorellius distribution is contiguous, exhibiting no disjunctions (see map in Fig. 204 ). The most northern species, T. intrepidus , is found as far north as Nayarit, and species T. cristimanus and T. atrox occur in Jalisco and Colima. Hoffmann (1931) also reported T. intrepidus from Veracruz. Species T. cisnerosi , T. occidentalis , and T. subcristatus occur the furthest south in Mexico, the latter two species reported for states Guerrero and Puebla.

Etymology. The new generic name (masculine) is a patronym honoring Swedish arachnologist Tord Tamerlan Teodor Thorell (1830–1901), one of the prominent scorpion taxonomists of the 19 th century, and the author of many scorpion taxa, including family Vaejovidae .

Diagnosis. Carapace anterior edge lacking conspicuous emargination, if present never extending to lateral eyes, median area either straight or with wide subtle indentation; metasomal segments IV–V length-to-width 1.4–1.7 (1.54) and 1.8–2.3 (2.12) for males, and, 1.3–1.6 (1.45) and 1.9–2.4 (2.10) for females; metasomal segments I–III ventromedian (VM) carinae usually smooth to granular; chelal carinae usually smooth to strongly marbled.

Taxonomic history. Scorpions of this genus were previously placed in the informal “intrepidus ” group of Vaejovis ; see Sissom (2000: 537–538).

Discussion. Genus Thorellius contain some of the largest species in family Vaejovidae . T. intrepidus has been reported up to 94 mm (Sissom, 2000: 537); only Syntropis or Smeringurus species may be slightly longer albeit much more slender. The smallest species in Thorellius are T. occidentalis and T. subcristatus , though both reach 50 mm. Unlike its sister genus Kochius , Thorellius may exhibit dark pigmentation and patterns; one species, T. atrox , is almost completely black in color.

As discussed above for genus Kochius , the metasoma of Thorellius is much thicker, approaching that seen in genus Hoffmannius . The heavy chelae, common to both Kochius and Thorellius , have their carinae less granular in Thorellius , but instead the carinae are irregular and “marbled” in appearance (see the digital (D1) carina in Figs. 144–145 for T. intrepidus and T. atrox ). The carapace anterior edge ( Figs. 134– 135 ) in Thorellius does not exhibit an emargination extending to the lateral eyes and the narrow median indentation is not present as seen in Kochius ( Figs. 128– 133 ).

Ponce Saavedra & Sissom (2004) described species T. cisnerosi from Michoacán, Mexico. The authors were reluctant to place this species into one of the established Vaejovis groups stating: “… Vaejovis cisnerosi is very unique in morphology, rendering its placement in established species group … difficult. … is unlike all other species of Vaejovis … carinae of the dorsal and lateral surfaces of the metasoma greatly reduced … smooth … metasomal setation is highly reduced … lowest setal counts of any species in genus … features are autapomorphic”. Clearly the hemispermatophore, with its well developed lamellar hook, the mating plug with its toothed barb, and the multiple pairs of ventral distal spinules of the leg tarsus imply this species is a member of tribe Syntropini . The chelal and metasomal carination of this species is unique (see Table 4) where the former exhibits vestigial to smooth carinae and the ventral carinae of the latter are obsolete. The existence of carinae on the chelae, though smooth, and the somewhat robust chelae imply this species is a member of subtribe Thorelliina . The carapace in T. cisnerosi lacks the anterior emargination extending to the lateral eyes as seen in Kochius and the placement of chelal trichobothrium Dt is well distal of the palm midpoint, indications of genus Thorellius (see histogram in Fig. 17 ). Finally, of somewhat less importance, the large size of this species, its large pectinal tooth count (20–22 for males and 20–21 for females), and its geographical distribution also indicates genus Thorellius .

Thorellius cristimanus , stat. nov. and T. atrox , stat. nov. are elevated here to species rank. These two taxa have been previously listed as Vaejovis intrepidus subspecies (Hoffmann, 1931: 378–385; Sissom, 2000: 538). The largest of the three species, T. intrepidus , has a much thinner metasoma than species T. cristimanus and T. atrox . In Table 4 we see that metasomal segments IIIII are longer than wide in both genders in T. intrepidus whereas segment II is wider than long and segment III is approximately as wide as long in T. cristimanus and T. atrox . To further quantify these differences, we compared two female T. intrepidus specimens from Tepic, Nayarit against two females of T. cristimanus from Autlán, Jalisco. Comparing morphometric ratios for each metasomal segment (length / width, averaged for the two female specimens per species), we found the following percentage differences: segment I = 17.2 %, segment II = 29.2 %, segment III = 25.0 %, segment IV = 24.7 %, and segment V = 25.3 %, showing that segments II–IV are 25 % thinner in T. intrepidus than in T. cristimanus . We found similar percentage differences between the male of these two species (one T. intrepidus from Mexico and two T. cristimanus from Autlán, Jalisco): segment I = 28.4 %, segment II = 26.4 %, segment III = 21.7 %, segment IV = 24.3 %, and segment V = 13.8 %. The metasomal segment proportions are essentially the same in T. cristimanus and T. atrox . However, the chelae in T. atrox are thinner than in T. intrepidus and T. cristimanus . In the female, comparing the length to the palm depth, we see a ratio of 2.882 in T. atrox versus 2.379 in T. cristimanus , a 21.1 % difference. The chela in T. intrepidus is even more robust, exhibiting a ratio of 2.160 for the female, showing a 33.4 % difference from T. atrox . This difference in the chela proportions is quite visible in Figs. 144–145 . Finally, T. atrox is a very dark scorpion, almost black, while T. intrepidus and T. cristimanus are much lighter, exhibiting a rich mahogany color with contrasting reddish carinae on the pedipalps and metasoma. The pectinal tooth numbers are slightly larger in T. intrepidus , 22–25 and 21–22 for male and female respectively, versus 21–24 and 19–21, and 19–20, for T. cristimanus and T. atrox (female only), respectively (data based on specimens examined and Hoffmann, 1931).

“Incertae sedis” members of subfamily Syntropinae

Two species, currently placed in genus Vaejovis (Sissom, 2000) , are clearly members of subfamily Syntropinae : Vaejovis flavus Banks, 1900 and Vaejovis pequeno Hendrixson, 2001 . These species, however, cannot be placed in a genus with certainty for the reasons detailed below: for V. flavus , the true identity of the type specimen of V. flavus is still in question, although Soleglad (1973a) redescribed V. flavus from a type specimen obtained from MCZ; for V. pequeno , interpretation of some characters as reported needs to be reevaluated.

“ Vaejovis ” flavus . Soleglad (1973a) redescribed V. flavus from a presumed type specimen obtained from MCZ. At that time both W. J. Gertsch and H. W. Levi were of the opinion that this was indeed Banks type specimen. Soleglad (1973a: 168–169) placed V. flavus in the “eusthenura ” group of Vaejovis although noting discrepancies both when compared with Banks’s (1900) original key (the only place that V. flavus was described) and with Williams’ (1970d) description of the group. In particular, the chelal palm carinae were well defined (see Soleglad, 1973a: fig. 5), the ventromedian carinae of the metasomal are crenulate, and a somewhat large pectinal tooth count for a female (22/21) was present.

Sissom (2000: 532) writes: “… The identity of this species, briefly described in a key couplet by Banks (1900), has long been problematic. Soleglad (1973a) redescribed the species, based on a specimen in the MCZ presumed to be the type. This specimen is apparently not the type (J. Bigelow, pers. comm.), and the true type is in the USNM. The specimens are not conspecific. Until V. flavus is redescribed from the USNM material, its identity cannot be known with certainty; Bigelow (pers. comm.) indicates, however, that it is a member of the eusthenura group. The MCZ specimen belongs to an undescribed species in the punctipalpi group .

Nothing matching either the original description or Soleglad’s redescription has subsequently been collected in the Albuquerque area (or anywhere else in New Mexico), despite extensive efforts ( Sissom , unpublished). A specimen I believe to be conspecific with that in the MCZ was found as part of the type series of V. punctipalpi in the USNM (Cokendolpher & Peck, 1991). Whether this specimen was actually part of the original type series cannot be confirmed; if it was, then this species would occur in Baja California Sur . …”

If, as suggested by Bigelow (see above), the USNM specimen is definitely in genus Hoffmannius (i.e., the “eusthenura ” group), then it would be closer to Banks’s (1900) “one-line description” than the MCZ specimen, thus can be designated as the lectotype. It was also suggested (C. Baptista, 2008, pers. comm.) that the USNM specimen may be Stahnke’s Hoffmannius confusus , further complicating the situation. The USNM specimen was not available for examination for this study.

For the MCZ specimen, we tend to agree with Sissom’s (2000) assessment, in part, as to group affiliation, certainly the crenulated palm and metasomal ventromedian carinae would be consistent with his suspicion. However, the high pectinal tooth count for a female is considerably out of the range of any known Kochius species, female or male, and therefore possibly its sister genus Thorellius is a better match. In Thorellius we have no less than three species with pectinal teeth in the range of the MCZ specimen. In either case, this specimen is a member of subtribe Thorelliina , probably a new species, and its locality is most likely incorrect. If our suspicion of a Thorellius match is correct, then the MCZ specimen is clearly an immature and probably originated from central Mexico.

“ Vaejovis ” pequeno . Hendrixson (2001) described Vaejovis pequeno , an interesting little scorpion from Sonora, Mexico, a species he did not place in any existing Vaejovis group. Hendrixson (2001) was quite meticulous in his description accounting for almost every important diagnostic character (albeit, the structure of the female genital operculum was not described and some trichobothria data were missing). This species was also discussed by Graham & Soleglad (2007) and compared to their new species Gertschius crassicorpus since they were similar “looking” and occupied the same geographic area in Sonora, Mexico. Based on Hendrixson’s (2001) description, Vaejovis pequeno clearly belongs to subfamily Syntropinae and tribe Stahnkeini : hemispermatophore with well developed lamellar hook, extending well beyond the ventral trough, with a conspicuous basal constriction; mating plug barb is smooth; chelal trichobothria ib – it not found on extreme finger base; dorsal carinae of metasomal segments I – IV straight proximally terminating with enlarged denticle; leg tarsus with a single distal spinule pair; cheliceral movable finger with well developed serrula; and the Total Length (TL) / Pectinal Tooth Count (PTC) ratio for the female is 1.463, well within the range of Stahnkeini (1.429 – 2.484 (1.941), see discussion elsewhere). Although there is no information on the spacing of chelal ventral trichobothria and the construction of the female genital operculum is not known, we feel comfortable that this species is not a member of subfamilies Smeringurinae or Vaejovinae . Therefore this species does not belong in genus Vaejovis , whose definition is now restricted considerably by the results of this paper.

The placement of Vaejovis pequeno into one of the four Stahnkeini genera recognized here is problematic. Wernerius can be eliminated because V. pequeno does not have a subaculear tubercle. Similarly, Serradigitus and Stahnkeus can be excluded since V. pequeno does not exhibit the exaggerated modified female pectines, highly serrated finger MD and OD denticles with elongated distal tips, and inner accessory denticles (IAD) are lacking. Genus Gertschius is the closest taxon to V. pequeno , but this can’t be decided until certain details of key structures are ascertained. We believe the real questions to this issue are the interpretations by Hendrixson of “modified basal pectinal teeth” and what constitutes a “serrated” denticle edge. Soleglad & Fet (2006) quantified these characters in great detail breaking them up into substructures. They also chronicled the history of these characters over time as described by authors dealing with species in genera Serradigitus and Stahnkeus . Interestingly, many authors did not view or described these diagnostic characters in the same fashion, and their interpretations changed over time. Many authors lumped several “subcomponents” of these characters (as defined by Soleglad & Fet, 2006) and if one or more subcomponents were missing, the structure was interpreted differently. Gertschius crassicorpus is a species where the serrated condition is reduced to only the median denticles (MD), the outer denticles (OD) are not serrated. In addition the elongated distal tooth, usually accompanied by a “whitish patch” was reduced or absent in this genus. The latter is probably due to the fact that G. crassicorpus appears not to be lithophilic. The lack of sensilla on the basal pectinal teeth of the female is restricted to the basal tooth in G. crassicorpus , and the tooth is not particular enlarged or ovoid. However, the number of MD + OD denticles is considerably reduced, conforming to the density quotient established for Stahnkeini by Soleglad & Fet (2006: tab. 1). These characters need to be reevaluated in V. pequeno before genus placement can be determined.

Figures

Figure 17: Histogram showing position of chelal trichobothrium Dt in relation to the palm length (Dt_pos/Palm_L: Dt_pos measured from palm base). More than 100 species and subspecies of family Vaejovidae and subfamily Uroctoninae (Chactidae) are represented. The extreme basal position of Dt in Uroctoninae is shown in contrast with Vaejovidae since at one time genus Uroctonus was considered a vaejovid. Vertical arrow indicates palm midpoint (i.e., ratio = 0.500). See Fig. 1 for explanation of histogram components.

Figure 204: General distribution of scorpion subfamily Syntropinae (tribe Syntropini, subtribe Thorelliina) in North America with the ranges of genera Kochius and Thorellius delineated.

Figures 140–151: Chela, external view, of representative Kochius, Thorellius, Hoffmannius, and Syntropis species, showing carination and trichobothria pattern. In particular note the well developed subdigital (D2) carina, the mid-palm position of trichobothrium Dt, and location of Db dorsal of the digital (D1) carina. 140. Kochius punctipalpi punctipalpi, female, Cabo San Lucas, Baja California Sur, Mexico. 141. K. hirsuticauda, female, Indian Gorge Canyon, ABDSP, California, USA. 142. K. bruneus loretoensis, male, Loreto, Baja California Sur, Mexico. 143. K russelli, female, Deming, New Mexico, USA. 144. Thorellius intrepidus, male, Mexico. 145. T. atrox, female, Colima, Colima, Mexico. 146. Hoffmannius eusthenura, male, Cabo San Lucas, Baja California Sur, Mexico. 147. H. gravicaudus, female, Santa Rosalia, Baja California Sur, Mexico. 148. H. globosus, female, Zacatecas, Zacatecas, Mexico. 149. H. puritanus, male, Jasper Trail, ABDSP, California, USA. 150. H. viscainensis, female, Las Bombas, Baja California Sur, Mexico. 151. Syntropis williamsi, male paratype, Los Aripes, Baja California Sur, Mexico (after Soleglad et al., 2007: fig. 13, in part).

Figures 128–139: Carapace, anterior half, of representative Syntropini species, emphasizing differences in the anterior emargination and median indentation. 128. K. punctipalpi punctipalpi, female, Cabo San Lucas, Baja California Sur, Mexico. 129. K. bruneus loretoensis, male, Loreto, Baja California Sur, Mexico. 130. K. hirsuticauda, female, Indian Gorge Canyon, ABDSP, California, USA. 131. K. cazieri, male, Cuatro Ciénegas, Coahuila, Mexico. 132. K russelli, female, Deming, New Mexico, USA. 133. K. kovariki, female holotype, Durango, Durango, Mexico. 134. T. atrox, female, Colima, Colima, Mexico. 135. T. cristimanus, male, Autlán, Jalisco, Mexico. 136. H. eusthenura, male, Cabo San Lucas, Baja California Sur, Mexico. 137. H. gravicaudus, female, Santa Rosalia, Baja California Sur, Mexico. 138. H. globosus, female, Zacatecas, Zacatecas, Mexico. 139. Syntropis aalbui, holotype female, Cataviña, Baja California, Mexico (after Soleglad et al., 2007: fig. 17, in part).