Incertae Sedis

Soleglad, Michael E. & Fet, Victor, 2003, High-level systematics and phylogeny of the extant scorpions (Scorpiones: Orthosterni), Euscorpius 2003 (11), pp. 1-175 : 119-121

Family Incertae Sedis (fossil taxa).

Genus Corniops Jeram, 1994 . – Extinct.

Geological occurrence. Carboniferous of North America.

Taxonomic history. This monotypic genus has not been placed in any family. It was listed by Fet et al. (2000) under “ Orthosternina Incertae Sedis ”.

Diagnosis. See Jeram (1994a) for details on the diagnosis of this genus.

Genus Palaeoburmesebuthus Lourenço, 2002 . – Extinct.

Geological occurrence. Cretaceous of Burma ( Myanmar) (Burmite amber, 112–98 Ma).

Taxonomic history. This monotypic genus was described (Lourenço, 2002a) as a fragment of metasoma without a family placement; however, Lourenço (2002a: 100) stated that it “is unquestionably a member of the Buthoidea ”. This statement, however, was based on shape and sculpture of metasomal segments only. Santiago-Blay et al. (in press) analyzed another fragmentary specimen of Palaeoburmesebuthus , with important but partial trichobothrial set on pedipalp chela. Judging from trichobothrial pattern and circular stigmata, this genus could belong to Archaeobuthidae , but the diagnostic characters are not sufficient to make a definite family placement (Santiago-Blay et al., in press). There is no current data which confirms placement of Palaeoburmesebuthus either in Buthoidea , or in parvorder Buthida , as defined here.

Diagnosis. See Lourenço (2002a) and Santiago-Blay et al. (in press) for details on the diagnosis of this genus.

Genus Sinoscorpius Hong, 1983 . – Extinct.

Geological occurrence. Miocene of China.

Taxonomic history. Fet et al. (2000) listed this monotypic genus under family Scorpionidae , as placed by the original author. From the brief original description, is impossible to establish a definite family placement.

Diagnosis. Hong (1983, available in Chinese only) can be consulted for details on the diagnosis of this genus.

Genus Uintascorpio Perry, 1985 . – Extinct.

Geological occurrence. Eocene of USA (Colorado).

Taxonomic history. Fet et al. (2000) listed this monotypic genus under “ Orthosternina Incertae Sedis ”. From the original description, it is impossible to establish a definite family placement.

Diagnosis. See Perry (1985) for details on the diagnosis of this genus.

Discussion. Uintascorpio shares some features with the parvorder Buthida ; Kovařík (1998) even suggested its synonymy with the extant buthid genus Rhopalurus . It is the oldest North American scorpion fossil since Carboniferous.

Scorpion Evolution geography

and Historical Bio-

Lamoral (1980) briefly outlined biogeographic hypotheses for family-level scorpion taxa, following his proposed phylogeny. The only recent comprehensive treatment of scorpion biogeography has been published by Nenilin & Fet (1992) in Russian. This work was based on scorpion systematics of the mid-1980s, and many important changes and interpretations have taken place since that time. Lourenço (1996b, 1998a, 2000a) and Lourenço & Sissom (2000) further commented on general historical and ecological issues, which contributed to the modern distributional patterns of the order, including disjunction and endemism. Table 11 lists present day distribution of families, subfamilies and tribes of Recent scorpions.

Although extinct scorpions are a rather diverse group (Kjellesvig-Waering, 1986), the fossils belonging to the infraorder Orthosterni are not common. The first orthostern scorpions, Palaeopisthacanthidae , are known from the Upper Carboniferous (Pennsylvanian) of the USA and England, ca. 300 Ma old (Jeram, 1994a, 1994b). Unfortunately, no orthostern fossils are known from the following 175 Ma. Several described genera of Permian, Triassic, and Jurassic fossil scorpions (Kjellesvig-Waering, 1986) do not belong to the Orthosterni . The next earliest orthostern fossil is known only from the Cretaceous (Barremian–Aptian, ca. 125 Mya), the genus Archaeobuthus from the Lebanese amber, not assigned to any of the existing parvorders. From later in the Cretaceous (ca. 110–100 Mya), fossils exist of the genera Palaeoburmesebuthus and Araripescorpius (not assigned to any of the existing parvorders), Palaeoeuscorpius (assigned to parvorder Iurida but not to any of the existing superfamilies), and Protoischnurus (parvor- der Iurida , superfamily Scorpionoidea ). It is clear therefore even from this meager handful of fossils that the extant parvorders and superfamilies were already well established by the Cretaceous. Indeed, all major nodes in our phylogeny ( Fig. 114) at parvorder and superfamily level have to precede, well in advance, the Cretaceous family Protoischnuridae .

An additional “upper bracket” might come from the distribution of modern-day families, some of which bear a clear trace of Gondwanaland breakup at the level below family. There is first of all family Bothriuridae (Scorpionoidea) , with its modern genera in South Africa, Australia, Asia and, especially, South America ( Prendini, 2000, 2003a, 2003b). The Gondwanaland breakup happened roughly in Jurassic–Cretaceous (170 to 130 Mya); by the beginning of Cretaceous (145 Mya) most continents were already separated. If we interpret Bothriuridae as a family which originated in Gondwanaland and was never present in Laurasia, then the common ancestor of this family should have existed before Cretaceous. At the same time, Bothriuridae is a sister group of Liochelidae and Scorpionidae , but the latter families also have Gondwanaland signature taxa, first of all isolated subfamilies Heteroscorpioninae on Madagascar, and Urodacinae in Australia; possibly the disjunct subfamily Diplocentrinae ; and maybe even the genus Opisthacanthus ( Liochelidae ), distributed in Africa and South America. It is then conceivable that all the families of Scorpionoidea were established by the end of Jurassic (146 Mya). Presence of Protoischnuridae fossils at 110 Mya does not contradict this assumption.

The superfamilies Buthoidea , Iuroidea , and Chactoidea , on the other hand, had to be established before the supercontinent Pangea started breaking apart in early Jurassic (Sinemurian), i.e. about 200 Mya (Brown & Lomolino, 1998; Scotese, 2002). This follows from their modern distribution, which is worldwide in Buthoidea (for which Pangean origin was first recognized by Birula (1917a, 1917b)), and worldwide but patchy in Iuroidea and Chactoidea (notably excluding Australia). None of the latter two superfamilies or any of their included families exhibits specifically “Gondwanaland” patterns: among Iuroidea , Caraboctonidae are found in the Americas, and Iuridae , in the Mediterranean; Chactidae is predominantly South American but with an important relict, Belisarius , in the Mediterranean; Euscorpiidae are disjunct among South America, Mexico, Southeast Asia, and the Mediterranean. Superstitioniidae are found in both South and North America, and Vaejovidae are endemic to North America. If any traces of Gondwanaland isolation could be found in non-scorpionoid superfamilies, these are expressed at the level of genera and groups of genera (such as Ananteris in Buthidae ; see also Fet et al., 2003). Therefore, early history of modern superfamilies has to be Pangean. Lourenço (1996b: 441) stated that “the main event responsible for determining the biogeographic patterns of scorpions on a palaeogeographic scale, has been the fragmentation of Pangea and subsequent continental drift”. We would caution, however, that not all vicariant ranges in modern scorpions (at the level of family and below) are interpretable by continental drift, and can be also explained by differential extinction and survival of relict taxa (Eskov, 1984, 1992, 2002; Nenilin & Fet, 1992).

The supercontinent Pangea was already forming at the Upper Carboniferous, from where we have the “lower bracket” fossils of Orthosterni . Therefore, the following 100 Ma of scorpion evolution took place within Pangea, before it started breaking apart. These 100 Ma embrace roughly the Permian period (290 to 251 Mya) and the Triassic period (251 to 206 Mya). Jeram (2001) indicated that the diversification of orthostern scorpions which followed in Permian/Triassic “can be attributed to their adoption of nocturnal habits, smaller adult body sizes, and burrowing behavior” as well as to ever-growing predation pressure from terrestrial tetrapods. It is reasonable therefore to place origin of four extant orthostern parvorders to Pangean times as well, provided that Palaeopisthacanthidae are the outgroup to all extant parvorders. The fate of these four extant parvorders was different. Two of them ( Buthida and Iurida ) still enjoy the world domination, albeit in Iurida with significant disjunctions possibly due to extinctions ( Iuroidea , Chactoidea ). Conversely, two other parvorders ( Pseudochactida and Chaerilida ) currently survive only in Asia as relict monotypic genera, Pseudochactas and Chaerilus . We cannot speculate where exactly the four orthostern parvorders originated within Pangea, but it is reasonable to assume that they should have been established during the Permian to Triassic time. It is important to note that this was also the time of evolutionary diversification of “reptiles” (Futuyma, 1998), who likely were (and still are) the competitors and, especially, predators of the terrestrial orthostern scorpions (Jeram, 2001). Further through Cretaceous, many animal taxa persisted as relicts while other perished during the global restructuring of ecosystems ( Zherikhin, 1978). It is possible that the primitive orthostern groups survived in such a relict condition. While Pseudochactida and Chaerilida remain only as relicts, Iurida and especially Buthida experienced a tertiary boost of radiation, notably due to the aridization in the Old World deserts ( Nenilin & Fet, 1992).