Iurida, Soleglad & Fet, 2003

Soleglad, Michael E. & Fet, Victor, 2003, High-level systematics and phylogeny of the extant scorpions (Scorpiones: Orthosterni), Euscorpius 2003 (11), pp. 1-175 : 18-27

Iurida

3.

medially oriented row of spinule clusters (irregular, concentrated clusters, or fused) – superfamily Iuroidea

4. paired lateral rows of rigid “spinoid” setae originating from large limbated sockets, with or without a median row of spinules – superfamily Scorpionoidea

5. paired lateral rows of small to medium setae with small sockets accompanied by a median row of spinules – superfamily Chactoidea

Pseudochactida : Pseudochactas , the sole member of this parvorder, conforms to configuration 1: two essentially parallel submedian rows of small spinules extending the entire length of the ventral aspect of the tarsus (Figs. 11–12). Each spinule exhibits subtle striations basally, extending to the midpoint or further ( Figs. 10 and 12). This form is unique in all Recent scorpions. However, its evolutionary polarity is not determinable, and therefore, this character is either autapomorphic to this monotypic genus or is inherited (i.e., plesiomorphic) from an ancestor. Jeram (1994a) illustrates similar dual rows of small spinules on the ventral aspect of the leg tibia and basitarsus (= protarsus) for Carboniferous fossil Compsoscorpius elegans (Text-Fig. 5, E & H); however the tarsus is unknown in this fossil family. In line with this simple configuration, we see that the basitarsus of Pseudochactas also has two ventral rows of spinules matching in size and position as those found on the tarsus (Gromov, 1998, Fig. 3.7). If this pattern of “matching spinule rows” across leg segments holds up for the palaeopisthacanthids, then it implies that this spinule configuration is plesiomorphic to the pseudochactids, again exhibiting another primitive character found on this Recent scorpion “relic”. In addition, the description of the dual spinule rows in fossil scorpion Palaeoburmesebuthus by Santiago-Blay et al. (in press) may imply that the dual rows exhibited in Pseudochactas are indeed primitive, however, the authors were not completely sure about the true identity of these tiny structures, i.e., spinules versus setae.

Buthida : The scorpions of this parvorder conform to configuration 2: two or more irregularly oriented rows of conspicuous socketed setae. In general, these setae are somewhat elongated and striated, originating from well-developed sockets ( Figs. 10 and 15–18). For Mesobuthus (Fig. 15) we see two irregular rows of fairly stout setae projecting from well-developed sockets. In genera Grosphus , Isometrus and Centruroides (Figs. 16–18), the number of irregular rows increase, the setae are longer, thinner, and the sockets are smaller. There is no evidence of any spinule development on the ventral aspect of the tarsus in buthoids.

Chaerilida : As the buthoids, the chaerilids conform to configuration 2: two irregular rows of stout heavy socketed setae ( Figs. 10, 13–14). In Figs. 10 and 14 we see the setal sockets are partially rimmed by minute blunt spinules and the setal shaft exhibits subtle striations. On the distal two-thirds of the ventral aspect of the tarsus, we see a median row of small blunt spinules (Fig. 13).

Iurida : The three superfamilies comprising parvorder Iurida present a wide variety of setal/spinule arrangements representing three fundamental configurations.

Iuroidea – Scorpions of this superfamily conform to setal/spinule configuration 3: median row of spinule clusters. Although the iuroids are a small (albeit, widely dispersed) group of scorpions, the variety of spinule cluster forms exhibited is exceptional. No less than three distinct forms are present, and one of these can be divided further into two subforms: 1) an irregular median row of grouped setal clusters (two to four) found in juvenile to subadult Calchas ; 2) a median row of highly concentrated setal clusters, forming “setaceous tufts”, found in genera Iurus , Caraboctonus and Hadruroides ; and a median row of “fused” setal clusters, forming individual “spinule-looking” protuberances, found in genus Hadrurus . The configuration found in Calchas is quite interesting (Figs. 19 and 23). This genus exhibits a considerable number of irregularly positioned large socketed setae ( Fig. 10). In adults, the median row of clustered spinules is essentially obsolete except for the proximal aspect. In subadults and juveniles, the spinule clusters are quite apparent being surrounded by the larger and heavier setae (Fig. 23). The tarsus of adult Calchas specimens is very similar to that found in Chaerilus , both with a domination of socketed setae. As pointed out above, Chaerilus also exhibits a small partial median row of blunt spinules, but they are neither clustered nor elongated as seen in Calchas . In the Old World iurid genus Iurus and the New World caraboctonines, Caraboctonus and Hadruroides , the spinule clusters are highly concentrated forming distinct “tufts” of elongated spinules ( Figs. 10, 20–21). In both of these iuroid groups, the individual clusters are situated on low-profile bases or platforms, which form a subtle ring around the cluster ( Figs. 10). In Iurus , the spinules are truncated, presenting a squared-off look to the cluster terminus. In Caraboctonus and Hadruroides , the individual spinules are tapered and of various lengths, forming an overall pointed looking spinule cluster ( Fig. 10). For all three genera, the number of spinules per cluster and their lengths are reduced considerably on younger specimens. For very early instar specimens (see Fig. 24 for Hadruroides charcasus ), the spinules in a cluster are reduced to minimal numbers, approximating those seen in Calchas . On mature specimens the individual spinules may number as high as 100+. When viewing the ventral aspect of the tarsus in genus Hadrurus under regular magnification (10–30x), one sees a closely grouped median row of spinules, typical of that seen in most vaejovids or chactids (Fig. 22). However, under high magnification, we see a somewhat blunt “spinule” with conspicuous irregularly formed ridges originating at its base and continuing most of its length ( Figs. 10 and 25). It is clear that these ridges are not the typical symmetric semi-parallel striations found on many setae and some spinules. Under close examination of the base of these ridges, we see that they are three-dimensional, exhibiting a relief almost separate from the other ridges forming the base. We hypothesize here that these ridges are residual spinules fused into a solid structure, presumably originating from the highly concentrated spinule clusters found in Hadrurus ’s sister group, Caraboctoninae . Note that this very unique set of derivations of the iuroid tarsus briefly described here is being further analyzed in detail in an upcoming paper involving extensive SEM micrography (Fet et al., in progress). In this analysis, multiple species are investigated, each spanning different ontogenetic stages.

Scorpionoidea – This superfamily conforms to setal/spinule configuration 4: two parallel lateral rows of heavy spinoid setae emanating from well-developed limbated sockets ( Figs. 10, 27–30). A median spinule row is optional. The number and lengths of these setal pairs are highly variable dependent on the group within this superfamily; they are quite numerous in the scorpionines and diplocentrines, and less numerous in the bothriurids and hemiscorpiines. Of particular interest is the reduction of these spinoid setae to thinner, more bristle-like setae, originating from smaller sockets in certain scorpionoid genera such as Brachistosternus , Iomachus and Liocheles (Fig. 30). Close inspection of these setal bases show that they still exhibit a somewhat substantial socket, but smaller, lower-profile, due to the much thinner seta.

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Chaerilus . 14 & 13. ovchinnikovi Pseudochactas . 12 & 11. arrangements spinule / setal showing Chaerilus and Pseudochactas of view lateral-ventral, tarsus Leg: 14 - 11. Figures variegatus

21

Scorpions Extant the of Phylogeny: Fet & Soleglad

17. bistriatus Grosphus

. 16.

eupeus Mesobuthus

. 15.

arrangements

setal

socketed showing genera buthid representative

of.

view anchorellus lateral-ventral, tarsus Centruroides 18. Leg. -: 18 15 maculatus Figures Isometrus

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Caraboctonus . 21. dufoureius Iurus . 20. nordmanni Calchas . 19. arrangements cluster spinule and setal showing genera iuroid of views lateral-ventral hirsutus ., tarsus Leg: Hadrurus 22 -. 22 19. Figures keyserlingi

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Scorpions Extant the of Phylogeny: Fet & Soleglad

24. juvenile, nordmanni Calchas . 23. configurations cluster spinule of closeup showing genera donensis . superstitioniid and Superstitionia . iuroid. 26 view of obscurus lateral-ventral.. 25 2 Hadrurus , tarsus instar-,: 26 Leg charcasus - 23 Figures Hadruroides

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29. comondae Bioculus . 28. maurus Scorpio . 27. arrangements setal socketed showing genera scorpionoid representative of view. australasiae lateral-ventral Liocheles ,. tarsus. 30 Leg: pocockii - 30 Figures 27 Centromachetes

25

Scorpions Extant the of Phylogeny: Fet & Soleglad

allenii Nullibrotheas

.

32.

tergestinus Euscorpius

.

31.

configurations spinule

and

setal showing genera chactid

and

euscorpiid

of

view. lateral-ventral, Anuroctonus sp tarsus.. 34: 34 Leg xambeui Figures - 31 Belisarius . 33

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37. reddelli Pseudouroctonus

. 36.

punctatus Vaejovis

. 35.

configurations spinule

and

setal showing genera vaejovid

of

view. grandis lateral-ventral, Smeringurus tarsus 38. . Leg: 38 gertschi

. - g

35 Figures Serradigitus

Chactoidea – This superfamily complies with setal/spinule configuration 5: moderate to well-developed lateral pairs of setae and a median row of spinules. The sockets of the setal pairs are of small to moderate development, never as large or significant as those seen in the spinoid setae of the scorpionoids or as that seen in most buthoids and chaerilids. The ventral median spinule row is present in all vaejovids and in a large majority of the euscorpiids and chactids as well. The dominance of setal pairs versus the median spinule row creates several sub-configurations within these two large assemblages of taxa (Figs. 31–39). The spinule median row is present in all vaejovids, the lateral setal pairs are of weak to moderate development. Within the vaejovids, the number of ventral distal spinule pairs is considered an important taxonomic character, separating some of the vaejovid genera and Vaejovis groups. Both one-pair and multiple-pair groups are illustrated in Figs. 35–38: Vaejovis punctatus and Pseudouroctonus reddelli (Figs. 35–36), and Serradigitus gertschi and Smeringurus grandis (Figs. 37–38), multiple-pair and one-pair, respectively. This character also proved to be important in the distinction of some euscorpiid genera (Soleglad & Sissom, 2001: 62–64). Williams & Savary (1991) defined the vaejovid genus Uroctonites based, in part, on the slightly heavier setal pairs found on the ventral aspect of the tarsus, in contrast to those found in other species of Pseudouroctonus . The chactid subfamilies Chactinae and Uroctoninae are similar to the vaejovids, all equipped with a median spinule row terminated by a single pair of distal spinules; the setal pairs are weakly developed in Uroctoninae (represented by Anuroctonus in Fig. 34) and well-developed on most Chactinae (represented by Nullibrotheas in Fig. 32). Subfamily Brotheinae has essentially lost the median spinule row showing a strong emphasis on the setal pair configuration: Brotheas and Belisarius (Fig. 33) with strongly developed setal pairs, and the other genera (e.g., Neochactas , Hadrurochactas ) with thinner but more numerous setal pairs (see Fig. 39 for the overall configurations of setal and spinule arrangements for family Chactidae ). In the superstitioniids we see three configurations. In subfamily Typhlochactinae (which includes Alacran ), the median spinule row is essentially absent (minor development is reported in T. mitchelli ( Sissom, 1988)) and the setal pairs are prevalent, but never as well-developed or numerous as those seen in the brotheines. In subfamily Superstitioniinae , which includes Superstitionia and Troglotayosicus , we see two patterns. In Superstitionia , we see a very unique, dense clustering of elongated spinules, which is similar, under normal magnification, to the spinules clusters seen in young Calchas specimens, although more dense and continuous but never forming concentrated clusters of setae as seen in some of the other iuroids ( Figs. 10 and 26). The Troglotayosicus tarsus has not been examined by us so our observations are based solely on the description and illustration provided by Lourenço (1981: 654, Fig. 43): although the figure shows socketed setae, the text uses the term “spinules (spiniformes)”; whether they are setae, spinules, or a mixture of both, they are in any case quite numerous, elongated, and irregularly positioned. If these “setae” turn out to be spinules, at least for the median area, then we can possibly see a taxonomic connection between this form and that exhibited by Superstitionia —both spinule sets would be exceptionally elongated and closely set, which is unprecedented in the chactoids.