Uroctoninae Mello-Leitão, 1934

Soleglad, Michael E. & Fet, Victor, 2003, High-level systematics and phylogeny of the extant scorpions (Scorpiones: Orthosterni), Euscorpius 2003 (11), pp. 1-175 : 102-104

Subfamily Uroctoninae Mello-Leitão, 1934

Type Genus. Uroctonus Thorell, 1876 .

Composition. This subfamily, as defined here, includes two genera, Anuroctonus and Uroctonus . The subfamily name is here taken out of synonymy, where it was available under the family Vaejovidae ( Sissom, 2000c: 504) , and transferred to Chactidae . We transfer to Uroctoninae genus Anuroctonus , which was previously listed in Iuridae (Sissom & Fet, 2000b) .

Distribution. North America ( Mexico, USA).

Taxonomic history. Stockwell (1989) used this name as a tribe rank in Vaejovidae but this change remained unpublished. Two genera, which are included here, are transferred from Iuridae ( Anuroctonus ) and Vaejovidae ( Uroctonus ). Placement of Anuroctonus was uncertain for many years: it was placed in Hadrurinae by Stahnke (1974; under Vaejovidae ) and Stockwell (1989, 1992; under Iuridae ), and treated as a genus incertae sedis by Francke & Soleglad (1981) and Sissom (1990). The genus was listed under Iuridae (subfamily Hadrurinae ) by Sissom & Fet (2000b). Here, we follow Werner (1934) in placing Anuroctonus under Uroctoninae .

Biogeographic history. The two North American genera of Chactidae , Anuroctonus and Uroctonus , are sister taxa, ecologically divergent. Anuroctonus is a typical desert borrowing scorpion, found in California, Nevada, Utah, and Idaho ( USA), and also in Mexico (Baja California Norte). Uroctonus is a less xeric species, found in western states of USA (California, Oregon) from sea coast to 2400 m in the montane forests (Gertsch & Soleglad, 1972; Williams, 1986; Sissom, 2000c). Interestingly, the two genera are essentially allopatric in coastal California, Anuroctonus replacing Uroctonus south of the Monterey Peninsula (Hjelle, 1972: Figs. 49–50), extending south into Baja California and east into the Great Basin. In central-eastern California, their ranges somewhat overlap, especially in Kern, Los Angeles, and Inyo counties. Interestingly, the isolated species Uroctonus franckei Williams , only reported at altitudes 2133 m or higher, occurs in the same area as Anuroctonus phaiodactylus , in the high eastern Sierra Nevada ( Williams, 1986). We have examined specimens of A. phaiodactylus from the general type locality of U. franckei , but from a somewhat lower altitude (1244 m).

Relationship between Uroctoninae and the other two chactid subfamilies is unclear. It is unlikely that Uroctoninae has a recent South American origin, and therefore it could be a relict of much earlier distribution of Chactidae . The separation and isolation of chactid subfamilies between South America and North America could result from the decoupling of the North American and South American plates, which played a prominent role in formation of the Caribbean region in late Mesozoic–early Tertiary ( Rosen, 1976; Francke & Soleglad, 1981).

Diagnosis. Synapomorphies. Patellar trichobothria distance between esb 1 and esb 2 considerably greater than distance between em 1 and em 2; ventral edge of cheliceral movable finger with dentition; chelal carina V1 distally curves internal towards internal condyle of finger; patellar spurs DPS and/or VPS well-developed; stigma medium to long in size, oval in shape; 3–4 lateral eyes present. Important Symplesiomorphies. Femur trichobothrium d positioned equal or distal to i; chelal trichobothrium Eb 1 situated on ventral surface or on V1 carina; genital operculum of female separated for most of its length.

Discussion. Establishment of this subfamily in Chactidae involved the transfer of two genera from other families, Uroctonus from Vaejovidae , and notably, Anuroctonus , from a different superfamily, Iuroidea .

Uroctonus . Uroctonus has long been a member of family Vaejovidae . Interestingly, the two genera now comprising Uroctoninae were considered related by earlier workers, having shared the same vaejovid subfamily Uroctoninae (old definition, as recognized by Mello-Leitão (1934: 81)) with genera Uroctonoides Chamberlin (= Teuthraustes , synonymized by Soleglad, 1973), and Physoctonus Mello-Leitão (= Rhopalurus , fam. Buthidae , synonymized by Francke, 1977). These genera were separated from Vaejovinae, in part, by their reduced number of pectinal middle lamellae, a somewhat minor and superficial character for subfamilial distinctions. Gertsch & Soleglad (1972) named several new species which they placed in genus Uroctonus . The primary character used for this placement was the crenulation found on the ventral edge of the cheliceral movable finger; in addition, secondary characters included the robust pedipalp chelae, the indentation on the anterior edge of the carapace, and reduced pectinal tooth counts. In general, these characters taken together, which were shared with Uroctonus , were unprecedented in the vaejovids. Issues involving trichobothria positions were not considered at that time since the use of trichobothriotaxy was new to the North American systematists (albeit Gertsch & Soleglad (1972) illustrated some of the first trichobothrial patterns of North American scorpion genera.). Based on other characters, Stahnke (1974) rejected the inclusion of most of these species in Uroctonus (he, correctly, only accepted U. grahami ), placing them in genus Vaejovis . Stockwell (1992) then moved most of these species into Pseudouroctonus , a genus originally created by Stahnke (1974) for species P. reddelli . Williams & Savary (1991) created Uroctonites for three of these species placed in Pseudouroctonus as well as naming a new fourth species. Stockwell (1989) offered the only cladistic treatment of these genera, considering the clade “ Pseudouroctonus + ( Uroctonites + Uroctonus )” monophyletic in Vaejovidae . Therefore, whether one agreed or not to which species belonged in Uroctonus , there seemed to be general agreement that they were all closely related. In this present study, we disagree with this conclusion, transferring Uroctonus to the family Chactidae . This transfer is based on several key positions of orthobothriotaxic trichobothria, involving both the chela (the ib–it, eb–et, and V 1 –V 4 series) and the patella (the ventral location of trichobothrium v 3). Secondary characters such as the completely separated genital operculum of the female and the termination of the dorsal lateral carinae of metasomal segment IV coinciding with the articulation condyle, are exhibited in Uroctonus and other chactids but are not found in the vaejovids.

Anuroctonus . Although Stockwell (1992) formally transferred Anuroctonus to the family Iuridae (now superfamily Iuroidea ), much of the foundation for this move was established earlier in his unpublished dissertation ( Stockwell, 1989), where he hypothesized that Anuroctonus is the sister genus to Hadrurus . It is of interest here to note that, out of 137 single state characters defined by Stockwell (1989), only one differed across the genera Hadrurus and Anuroctonus , that dealing with the arrangement of the chelal median denticle (MD) row (we discuss this below). In 1992, Stockwell presented his rationale for moving Anuroctonus to the iuroids. First, Stockwell limited his choices for Anuroctonus placement (it was incertae sedis at the time) to either Vaejovidae or Iuroidea , completely dismissing Chactidae . Chactidae was not considered as an alternative because all pedipalp patellar ventral trichobothria were restricted to the ventral surface in this family, and therefore, it was noticed in contrast that one or more ventral trichobothria are found on the external surface in Vaejovidae and Iuroidea . Although we consider the displacement of patellar ventral trichobothria to the external surface an important derivation if they are orthobothriotaxic, we do not necessarily think it is important if the trichobothrium in question is accessory (i.e., unlike the orthobothriotaxic trichobothrium, the accessory trichobothrium did not move to the external surface—it originated there). Anuroctonus and Hadrurus both exhibit major neobothriotaxy and both share the unusual feature of the patellar ventral series “wrapping” around distally to the external surface. We agree with Stockwell that some of these displaced trichobothria in Hadrurus probably do involve trichobothrium v 3 because this trichobothrium is also found on the external surface in all other members of Iuroidea . However, we cannot make this same assumption with Anuroctonus . The trichobothria extending to the external surface are located on the extreme distal aspect of the segment ( Fig. 82). If Anuroctonus belongs to Chactidae , an option Stockwell should have considered as well, then we can equally conclude that these trichobothria are much too distal to include v 3 —thus this important derivation is absent in this genus, therefore eliminating any connection with Hadrurus . This alternative conclusion is based on two orthobothriotaxic chactid genera ( Belisarius ( Fig. 87) and Uroctonus ( Fig. 81)), where we see that v 3 is located more midsegment. Therefore, in Stockwell’s argument, he must assume Anuroctonus belongs to either Vaejovidae or Iuridae in order to conclude that v 3 indeed is one of these trichobothria found on the external surface—clearly a circular argument. Chactidae is an equally valid alternative. In our argument we use positions of important orthobothriotaxic trichobothria of the chela to form a connection between Anuroctonus and the chactids and then, based on this connection, can conclude that v 3 is indeed located on the ventral surface, not on the external surface as assumed by Stockwell. Stockwell also considered major neobothriotaxy as a common character between these two genera, which is true, but it certainly is not unique and he did not present arguments for establishing that they had the same derivation (i.e., major neobothriotaxy is quite common in the chactoids and scorpionoids). For example, in genera Paravaejovis and Anuroctonus , the ventral trichobothria of the chela extend to the external surface of the palm ( Figs. 66 and 82), but they do not extend to the external surface in Hadrurus . The somewhat unique fully separated genital operculum found in the females of Hadrurus and Anuroctonus is another character Stockwell thought important; again, however, this same condition is also found in the chactids. Finally, more important than any of these characters offered by Stockwell (1992), are the dentition of ventral edge of the cheliceral movable finger, the alignment of the median denticle (MD) row of the chelal finger, and the unique spinule configuration of ventral surface of the leg tarsus. Stockwell (1989) considered the small denticle(s) found on the base of the ventral edge of the cheliceral movable finger of Anuroctonus to be homologous to the large single denticle found in Iuroidea . We refute this homology for two reasons: 1) small denticle(s) are not homologous to a large single denticle, which is consistently found in, and only in, the iuroids; 2) the presence of minor crenulation on the ventral edge of the cheliceral movable finger is not unusual in the chactoids, so the necessity to consider the minor dentition found in Anuroctonus and not other similar crenulations found in some vaejovids (e.g., Paruroctonus gracilior , P. stahnkei , etc.), homologous to the substantial tooth found in Iuroidea , is clearly arbitrary and therefore unfounded. All iuroids have their median denticle (MD) groups of the chelal finger aligned obliquely; the MD row is straight in Anuroctonus , as it is in most chactoids. We have demonstrated in this paper that the oblique MD groups exhibited in the iuroids are directly inherited from the primitive condition as found in the primitive parvorders Pseudochactida , Buthida , and Chaerilida (which those parvorders, in turn, inherited from the fossil orthosterns such as palaeopisthacanthids). Anuroctonus inherited the straight MD row from an earlier derivation which occurred at the node “ Scorpionoidea + Chactoidea ”. [Note: the obliquely arranged MD row found in the chactoid family Superstitioniidae is considered a “recent” secondary derivation from a straight MD row]. It was established in this paper (see Character Analysis section) that the ventral armature of the leg tarsus found in all five iuroid genera is based on a unique spinule cluster configuration. In genus Hadrurus the spinule clusters, which are quite exaggerated in its sister subfamily Caraboctoninae , are fused into a solid “spinule-looking” structure. In Anuroctonus we see the conventional spinule row common to chactid subfamilies Chactinae and Uroctoninae . Of course, Stockwell (1989, 1992) was not aware of this unique development of the iuroid leg tarsus median spinule row.