Opistophthalminae Rossi, 2016

Prendini, Lorenzo & Loria, Stephanie F., 2020, Systematic Revision Of The Asian Forest Scorpions (Heterometrinae Simon, 1879), Revised Suprageneric Classification Of Scorpionidae Latreille, 1802, And Revalidation Of Rugodentidae Bastawade Et Al., 2005, Bulletin of the American Museum of Natural History 2020 (442), pp. 1-480 : 435-437

Subfamily Opistophthalminae Rossi, 2016 ,

stat. nov.

Opistophthalmini Rossi, 2016a: 20, 26, type genus: Opistophthalmus C.L. Koch, 1837 .

Protophthalmini Rossi, 2016a: 20 , 22, 26, type genus: Protophthalmus Lawrence, 1969 ; syn. nov.

DIAGNOSIS: Most species of Opistophthalminae can be separated from the other subfamilies of Scorpionidae by means of the following characters ( Prendini et al., 2003): cheliceral coxae with stridulatory setae (scaphotrix) on prodorsal surfaces and chemoreceptive lamelliform setae (trichocopae) on promedian surfaces. Opistophthalminae can be further separated from Heterometrinae and Pandininae by means of the following characters: absence of a stridulatory organ, comprising a “rasp” (granular tubercles) and “scraper” (stridulatory setae or scaphotrix), on opposing surfaces of the coxae of the pedipalps and the first pair of legs; digital carina of pedipalp chela usually distinct; counts of pro- and retroventral spiniform macrosetae increasing from telotarsi I and II to III and IV. Opistophthalminae can be further separated from Heterometrinae and Scorpioninae by means of the following character: pedipalps neobothriotaxic major, with more than 26 trichobothria (including more than 13 trichobothria in e series of patella).

INCLUDED TAXA: As redefined in the present contribution, a single genus, Opistophthalmus , with 59 species ( Prendini, 2001a), is currently recognized in Opistophthalminae but the systematics of the subfamily is undergoing active revision by the first author. As discussed below, the synonymy of Protophthalmus by Newlands (1972a), confirmed by the phylogenetic analyses of Lamoral (1978a, 1979), Prendini (2000a) and Prendini et al. (2003), is upheld pending evidence to the contrary.

DISTRIBUTION: Africa: Angola, Botswana, Lesotho, Malawi, Mozambique, Namibia, South Africa, Swaziland, Tanzania, Zambia, Zimbabwe.

Opistophthalminae are distributed from the Cape Peninsula of South Africa to Mount Kilimanjaro in Tanzania. The subfamily is absent from the tropical rainforests of the Congo basin and no records are known from north of the equator.

ECOLOGY: All species of Opistophthalminae are obligate burrowers, constructing burrows under stones or in open ground ( Purcell, 1899; Skaife, 1920; Lawrence, 1971, 1973; Newlands, 1972a, 1972b, 1978; Eastwood, 1978a, 1978b; Lamoral, 1978a, 1978 b, 1979). As most are highly cannibalistic, cohabitation of multiple individuals within a single burrow (except during courtship or parental care) and/or the communal construction of burrows are absent ( Eastwood, 1978a, 1978b). Burrows vary from shallow scrapes to elaborate, spiralling tunnels reaching depths of more than 1 m below the surface, depending on the species. Each species constructs burrows in substrata of specific hardness and composition, varying from unconsolidated sand dunes to compacted clayey soils, depending on the species ( Newlands, 1972a, 1972b, 1978; Lamoral, 1978 b, 1979). Several species have adapted to extremely rocky habitats (e.g., scree slopes) and virtually lost the ability to burrow, sheltering under stones instead ( Purcell, 1899; Hewitt, 1925; Eastwood, 1978b). The ability of different species to burrow in substrata of specific hardness correlates closely with their morphology, such that a gradation of ecomorphotypes can be recognised, from lithophilous, through pelophilous, to psammophilous ( Newlands, 1972a, 1972b, 1978; Eastwood, 1978b; Lamoral, 1979; Prendini, 2001d).

CONSERVATION STATUS: Habitat destruction through agriculture (ploughing), afforestation and urbanization poses the greatest threat to species of Opistophthalminae , most of which are ecologically specialized (thus only occurring in pristine habitat), and range-restricted. Several are critically endangered, particularly in the Western Cape Province of South Africa.

The international trade in exotic pets poses a small, but ever-increasing threat to the future survival of Opistophthalminae , given their increasing popularity as pets on the one hand, and their often extremely restricted distributional ranges, together with the continued destruction of their habitat, on the other. Two species, Opistophthalmus glabrifrons Peters, 1861 (the “Shiny burrowing scorpion”) and Opistophthalmus wahlbergii (Thorell, 1876) (“Wahlberg’s Tri-colored scorpion”), allegedly imported from Mozambique, are commonly available in Europe, the United States, and Japan ( Prendini et al., 2003). As the distribution of O. wahlbergii does not extend to Mozambique and the form offered occurs only in eastern Botswana and the Limpopo Province of South Africa, these scorpions are probably exported from one of the latter countries. A third species, Opistophthalmus boehmi (Kraepelin, 1896) , advertised as the “Tricoloured scorpion” in the United States and as the “Kilimanjaro mustard scorpion” in Japan, is regularly imported from Tanzania ( Dupré, 1992; Prendini et al., 2003).

REMARKS: Lawrence (1969) described Protophthalmus as a new genus with Protophthalmus holmi as type species. Newlands (1972a: 241) synonymized Protophthalmus with Opistophthalmus while Lamoral (1972) described a second species, Protophthalmus jenseni . Lamoral and Reynders (1975) retained P. holmi and P. jenseni in Protophthalmus based on evidence available at the time. However, a phylogenetic analysis of morphological characters by Lamoral (1978a, 1979: 501) subsequently confirmed that Protophthalmus is congeneric with Opistophthalmus :

In the distinctly tapered and fusiform distal crests of the distal lamina of their hemispermatophores, Opistophthalmus holmi and O. jenseni share a character state uniquely derived in this genus. It was felt at some stage that such uniqueness provided sufficient distinctness to retain holmi and jenseni within Lawrence’s (1969: 105) genus Protophthalmus . The existence of several synapomorphies between the holmi-jenseni sister species and other species within the wahlbergi group has, however, prompted me not to reinstate the genus Protophthalmus as anticipated previously ( Lamoral and Reynders, 1975: 569).

All subsequent phylogenetic analyses based on morphology and multilocus DNA sequences recovered the monophyly of Opistophthalmus and placed Opistophthalmus holmi ( Lawrence, 1969) in a distal position within it ( Prendini, 2000a; Prendini et al., 2003), reinforcing the opinion of Lamoral (1979: 719) “that Protophthalmus is congeneric with Opistophthalmus and that holmi and jenseni represent an extreme sister group separated from other species by a series of derived character states.”

Based solely on statements about “important characters,” and unsubstantiated by new evidence or analysis, Rossi (2016a: 18) revalidated Protophthalmus and erected two new tribes of Scorpioninae , in addition to the nominotypical tribe: Opistophthalmini was created to accommodate Opistophthalmus and Protophthalmini to accommodate Protophthalmus . Only three characters were offered to separate the putative tribes of Scorpioninae in Rossi’s (2016a: 26) key: total counts of pedipalp trichobothria (i.e., orthobothriotaxy vs. neobothriotaxy); counts of trichobothria on the ventral surface of the pedipalp chela manus; position of the median ocelli on the carapace.

Whereas total counts of the pedipalp trichobothria were correctly applied for the separation of Scorpio from the other scorpionid taxa, it was erroneously suggested that Opistophthalmus usually possess more than three trichobothria on the ventral surface of patella. The high counts of trichobothria on the ventral surface of the pedipalp chela manus, cited as diagnostic for Protophthalmus , are autapomorphic and therefore phylogenetically uninformative ( Prendini, 2000a; Prendini et al., 2003). Additionally, as noted by Lamoral (1979: 519, 658) and Prendini (2016: 52), it is inadvisable to use neobothriotaxic patterns as diagnostic characters for genera and species, in the absence of other characters, especially when trichobothrial counts are high, due to the greater instability of the patterns. With specific reference to neobothriotaxy in O. holmi, Lamoral (1979: 519) noted:

The frequency of…variations is higher in cases of marked (+) neobothriotaxies reaching levels where the trichobothriotaxies of certain segmental surfaces cease to be of interspecific value, e.g., the external trichobothria of the tibia [patella] in Opisthophthalmus holmi and the ventral trichobothria of the tibia in species of Hadogenes .… While trichobothria have proved to be of diagnostic value in many taxa, trichobothriotaxy must be used with caution. Its value varies from group to group and both intra- and interspecific variation needs to be studied.

Finally, it was erroneously suggested that the position of the median ocelli is usually closer to the posterior border in Opistophthalmus . On the contrary, the position of the median ocelli varies tremendously among the species of Opistophthalmus and was disregarded as a diagnostic character for Protophthalmus by previous authors for that very reason ( Newlands, 1972a; Lamoral, 1979, 1980; Prendini, 2000a, 2001a; Prendini et al., 2003).

The inclusion of Opistophthalmus and Protophthalmus in Scorpioninae by Rossi (2016a) implies that these taxa form a monophyletic group with Scorpio , a relationship confirmed in only one phylogenetic analysis to date ( Prendini, 2000a). However, that analysis formed part of a larger analysis of relationships within superfamily Scorpionoidea , based on exemplar species, and did not include molecular data. Analyses based on multilocus DNA sequence data and morphology, including more extensive sampling of scorpionid exemplars, failed to recover a monophyletic group comprising the type species of Opistophthalmus , Protophthalmus , and Scorpio ( Prendini et al., 2003) . The evidence overwhelmingly suggests that Scorpioninae , as defined by Rossi (2016a), is paraphyletic, justifying the removal of Opistophthalmini and its elevation to the rank of subfamily, i.e., Opistophthalminae Rossi, 2016 , stat. nov. Furthermore, pending evidence to the contrary, both Opistophthalmus and Opistophthalminae are rendered paraphyletic by Protophthalmus and Protophthalmini , justifying their synonymy as follows: Protophthalmus Lawrence, 1969 = Opistophthalmus C.L. Koch, 1837 , syn. nov.; Protophthalmini Rossi, 2016 = Opistophthalminae Rossi, 2016 , syn. nov.

Opistophthalminae is the largest and most morphologically diverse subfamily of Scorpionidae ( Prendini et al., 2003). Compared with the other scorpionid subfamilies, Opistophthalminae are characterised by numerous morphological apomorphies, many of which are also unique among scorpions. For example, most species of Opistophthalminae possess organs for chemoreception and stridulation on the chelicerae that are absent in other scorpions ( Pocock, 1896b; Purcell, 1899; Hewitt, 1915, 1918, 1925, 1931; Pavlovsky, 1924b; Skaife, 1920; Lawrence, 1928, 1971, 1973; Werner, 1934; Millot and Vachon, 1949; Alexan- der and Ewer, 1957; Alexander, 1958, 1959; Vachon et al., 1958, 1960; Dumortier, 1964; Sissom, 1990; Prendini, 2000a). A unique proximal displacement of the median ocelli on the carapace ( Hewitt, 1925; Lawrence, 1969; Newlands, 1972a, 1978), from which the genus derives its Latin name ( Skaife, 1920, 1954), is exhibited by many species of Opistophthalminae . Most species also display peculiar, segmentally variable surface macrosculpture of the mesosomal sternites and ventral side of the first four metasomal segments, often associated with loss or reduction of the ventrosubmedian and ventrolateral metasomal carinae ( Hewitt, 1918, 1925; Prendini, 2000b).

Among other characters, some species of Opistophthalminae display exceptionally high pedipalp trichobothrial counts among scorpions, whereas others display exceptionally low pectinal tooth counts. The subfamily is further characterized by marked extremes in adult size, varying from among the largest known scorpion species such as Opistophthalmus gigas Purcell, 1898 , which commonly reaches 160 mm in length, to dwarves (including the smallest scorpionid species) such as Opistophthalmus pygmaeus Lamoral, 1979 , a mere 40 mm in length. Finally, many species in the subfamily display exaggerated sexual dimorphism in the shape of the pedipalp chelae ( Purcell, 1899; Hewitt, 1918, 1925; Newlands, 1972a; Eastwood, 1978b; Prendini, 2000b), surface macrosculpture of the pedipalps, mesosoma, and metasoma, and the pectinal tooth counts ( Hewitt, 1925; Lawrence, 1969; Newlands, 1972a; Lamoral, 1979).

Given the tremendous morphological diversity within Opistophthalminae , attempts to parti- tion the variation into subunits without the application of modern analytical methods and genomic sources of data (work that is actively underway) are even less likely to be successful than past attempts to do so among the taxa presently accommodated within Heterometrinae and Pandininae .