version ISSN 0104-7930
J. Venom. Anim. Toxins vol.7 no.1 Botucatu 2001
ABSTRACT: A synoptic table is proposed for the families and genera of scorpions currently regarded as valid. Because there is considerable disagreement about the classification of scorpions, many changes are to be expected in the future. The classification proposed here is followed by considerations regarding the geographical distribution of each family.
KEY WORDS: scorpion, families, genera, check-list, classification, geographical distribution.
As already emphasized in previous papers (17,20), study of the familial classification of scorpions really began in the middle of the 19th century with a paper by Peters (24). This was followed by several other relevant publications, in particular those of Thorell (31), Karsch (5,6), Simon (27,28), Pocock (26), Kraepelin ( 7-9), and Birula (1,2). There was a more conservative period following these important contributions to our understanding of scorpion classification. During this period, only six or seven families were recognized, until the publications of Lamoral (11) and Lourenço (13,14), in which respectively 8 and 9 families were accepted.
In recent years, familial classification of scorpions has again become a major concern of arachnologists, in particular since Stockwell's Ph.D. thesis in 1989 (30). This promoted several subfamilies to familial rank, and the position of a number of genera within the different families was revised. After the presentation of this thesis (which was not published), several authors continued to recognize only the nine families defined by Lourenço (13,14), but for others, a division of these into several smaller groups appeared to be a real need. This new situation led to the recognition of 16 to 20 different families, according to different authors. This increase in the number of families was caused mainly by the promotion of sub-families to families (3,15,17,18,19).
The indecision of previous authors in relation to the division of certain large families into smaller groups seems to be associated with two major considerations:
A. Greater subdivisions of familial groups inevitably leads to the creation of very much smaller families containing fewer genera and species; and
B. In several cases, elements belonging to a given familial group may consist of relict species with disrupted geographical distributions. These appeared enigmatic not only to earlier authors but also some more recent ones.
The situation as summarized above in A and B can be better explained in the light of panbiogeographic concepts (25). It is important to realize that scorpions are a very ancient taxon, and the biogeographical patterns observed today constitute only fragments of their original distribution. The remainder of this incomplete «puzzle» is the consequence of various vicariant processes of delegation (16).
In his thesis, Stockwell (30) opened the door to some important decisions, such as the proposition of super-families. I certainly agree with Stockwell about the necessity for super-familial classification, but I do not entirely accept his proposed classification. I have retained here those suggestions of Stockwell (30) that appear valid to me. At the same time, I have proposed some alternatives to his super-familial classification.
The objective of this paper is not to enter into a discussion of the problems and difficulties related to the familial classification of scorpions, but rather to present a synthesis of the most recent familial classification, which may serve as a reference to non-specialists whose research embraces scorpions.
THE FAMILIAL CLASSIFICATION OF SCORPIONS PROPOSED IN THIS PAPER
The supra-familial classification proposed by Stockwell (30) is convenient in that it deals mainly with fossil forms. As there is a case for considerable speculation, I have retained the basis of his classification.
Class Scorpionida Latreille, 1802.
- Protoscorpiones Petrunkevich, 1949.
- Palaeoscorpiones Stockwell, 1989.
- Scorpiones C.L. Koch, 1837.
In the last of these orders, Stockwell included two sub-orders:
- Mesoscorpionina Stockwell, 1989.
- Neoscorpionina Thorell & Lindström, 1885.
The Neoscorpionina are divided into 2 infraorders:
- Palaeosterni Stockwell, 1989.
- Orthosterni Pocock, 1911.
The Orthosterni comprises extant scorpions*.
I Superfamily Bothriuroidea Simon, 1880 (with 1 family)
Bothriuridae Simon, 1880.
12 genera: Bothriurus Peters, 1861; Brachistosternus Pocock, 1893; Brazilobothriurus Lourenço & Monod, 2000; Centromachetes Lönnberg, 1897; Cercophonius Peters, 1861; Orobothriurus Maury, 1975; Phoniocercus Pocock, 1893; Tehuankea Cekalovic, 1973; Thestylus Simon, 1880; Timogenes Simon, 1880; Urophonius Pocock, 1893; and Vachonia Abalos, 1954.
Geographical distribution: South America, Australia, and India (Himalayas).
Note: Stockwell placed the Bothriuridae in the superfamily Scorpionoidea.
II Superfamily Buthoidea C. L. Koch, 1837 (with 2 families)
Buthidae C. L. Koch, 1837
About 80 genera (some of which are not clearly defined):
Afghanorthochirus Lourenço & Vachon, 1997; Afroisometrus Kovarik, 1997: Akentrobuthus Lamoral, 1976; Alayotityus Armas, 1973; Ananteris Thorell, 1891; Androctonus Ehrenberg, 1828; Anomalobuthus Kraepelin, 1900; Apistobuthus Finnegan, 1932; Australobuthus Locket, 1990; Babycurus Karsch, 1886; Baloorthochirus Kovarik, 1996; Birulatus Vachon, 1974; Buthacus Birula, 1908; Butheoloides Hirst, 1925; Butheolus Simon, 1882; Buthiscus Birula, 1905; Buthoscorpio Werner, 1936; Buthus Leach, 1815; Caribetityus Lourenço, 1999; Centruroides Marx, 1890; Charmus Karsch, 1879; Cicileus Vachon, 1948; Compsobuthus Vachon, 1949; Congobuthus Lourenço, 1999; Darchenia Vachon, 1977; Egyptobuthus Lourenço, 1999; Grosphus Simon, 1880; Hemibuthus Pocock, 1900; Himalayotityobuthus Lourenço, 1997; Hemilychas Hirst, 1911; Hottentotta Birula, 1908; Iranobuthus Kovarik, 1997; Isometroides Keyserling, 1885; Isometrus Ehrenberg, 1828; Karasbergia Hewitt, 1913; Kraepelinia Vachon, 1974; Leiurus Ehrenberg, 1828; Liobuthus Birula, 1898; Lissothus Vachon, 1948; Lychas C. L.Koch, 1845; Lychasioides Vachon, 1974; Mesobuthus Vachon, 1950; Mesotityus González-Sponga, 1981; Microbuthus Kraepelin, 1898; Microtityus Kjellesvig-Waering, 1966; Nanobuthus Pocock, 1895; Neobuthus Hirst, 1911; Neogrosphus Lourenço, 1995; Odontobuthus Vachon, 1950; Odonturus Karsch, 1879; Olivierus Farzanpay, 1987; Orthochirus Karsch, 1891; Orthochiroides Kovarik, 1998; Pakistanorthochirus Lourenço, 1997; Palaeolychas Lourenço & Weitschat, 1996; Palaeogrosphus Lourenço, 2000; Parabuthus Pocock, 1890; Paraorthochirus Lourenço & Vachon, 1997; Pectinibuthus Fet, 1984; Plesiobuthus Pocock, 1900; Protoneobuthus Lourenço, 2000; Psammobuthus Birula, 1911; Pseudolychas Kraepelin, 1911; Pseudouroplectes Lourenço, 1995; Pseudolissothus Lourenço, 2001; Razianus Farzanpay, 1987; Rhopalurus Thorell, 1876; Sassanidothus Farzanpay, 1987; Simonoides Farzanpay, 1987; Somalibuthus Kovarik, 1998; Somalicharmus Kovarik, 1998; Thaicharmus Kovarík, 1995; Tityobuthus Pocock, 1893; Tityopsis Armas, 1974; Tityus C. L. Koch, 1836; Troglotityobuthus Lourenço, 2000; Uroplectes Peters, 1861; Uroplectoides Lourenço, 1998; Vachoniolus Levy, Amitai & Shulov, 1973; Vachonus Tikader & Bastawade, 1983; and Zabius Thorell, 1894.
Geographical distribution: All continents except Antarctica, in tropical, sub-tropical, and to some extent temperate regions.
Microcharmidae Lourenço, 1996.
2 genera: Microcharmus Lourenço, 1995; Protoneobuthus Lourenço, 2000.
Geographical distribution: Madagascar.
Note: The genus Akentrobuthus Lamoral has been returned to the family Buthidae. More precise definitions have been given in Lourenço (21).
III Superfamily Chaeriloidea Pocock, 1893 (with 2 families)
Chaerilidae Pocock, 1893.
1 genus: Chaerilus Simon, 1877
Geographical distribution - Asia: Bangladesh, India, Indonesia, Malaya, Nepal, Singapore, Sri Lanka, and Vietnam.
Note: Stockwell placed the family Chaerilidae in the superfamily Buthoidea. I propose here its own superfamily.
Pseudochactidae Gromov, 1998.
1 genus: Pseudochactas Gromov, 1998.
Geographical distribution: Southern Central Asia.
IV Superfamily Chactoidea Pocock, 1893 (with 5 families)
Chactidae Pocock, 1893.
9 genera: Brotheas C. L. Koch, 1837; Broteochactas Pocock, 1893; Cayooca Gonzalez-Sponga, 1996; Chactas Gervais, 1844; Chactopsis Kraepelin, 1912; Nullibrotheas Williams, 1974; Guyanochactas Lourenço, 1998; Teuthraustes Simon, 1878; and Vachoniochactas González-Sponga, 1978.
Geographical distribution: South and Central America and Mexico (Baja California).
Euscorpiidae Laurie, 1896
4 genera: Euscorpius Thorell, 1876; Megacormus Karsch, 1881; Plesiochatas Pocock, 1900; and Troglocormus Francke, 1982.
Geographical distribution: North Africa, Southern Europe, Middle East, Southern Central Asia, Mexico, and Guatemala.
Troglotayosicidae Lourenço, 1998
2 genera: Belisarius Simon, 1879; and Troglotayosicus Lourenço, 1981.
Geographical distribution - Oriental Pyrenees: France/Spain, and Ecuadorian Amazon.Scorpiopidae Kraepelin, 1905.
6 genera: Dasyscorpiops Vachon, 1973; Parascorpiops Banks, 1928; Scorpiops Peters, 1861; Alloscorpiops Vachon, 1980; Euscorpiops Vachon, 1980; and Neoscorpiops Vachon, 1980.
Geographical distribution: Afghanistan, South-East Asia, India, Pakistan, Indonesia, and Malaya.
Superstitioniidae Stahnke, 1940.
4 genera: Alacran Francke, 1982; Sotanochactas Francke, 1986; Superstitionia Stahnke, 1940; and Typhlochactas Mitchell, 1968.
Geographical distribution: Mexico and The Southwestern United States.
V Superfamily Vaejovoidea Thorell, 1876 (with 2 families)
Vaejovidae Thorell, 1876.
10 genera: Syntropis Kraepelin, 1900; Vejovoidus Stahnke, 1974; Paravaejovis Williams, 1980; Paruroctonus Werner, 1934; Pseudouroctonus Stahnke, 1974; Serradigitus Stahnke, 1974; Smeringurus Haradon, 1983; Uroctonus Thorell, 1876; Uroctonites Williams & Savary, 1991; and Vaejovis C.L. Koch, 1836.
Geographical distribution: Mexico and The South/Southwestern United States.
Iuridae Thorell, 1876.
6 genera: Anuroctonus Pocock, 1893; Caraboctonus Pocock, 1893; Hadruroides Pocock, 1893; Hadrurus Thorell, 1876; Calchas Birula, 1899; and Iurus Thorell, 1876.
Geographical distribution: South America, North America, Asia (Turkey), and Europe (Greece).
Note: Anuroctonus remains incertae sedis. According to Fet (person. comm.), a new family Anuroctonidae, close to the Vaejovidae, will soon be created for this particular genus.
VI Superfamily Scorpionoidea Latreille, 1802 (with 8 families)
Scorpionidae Latreille, 1802.
5 genera: Heterometrus Ehrenberg, 1828; Mioscorpio Kjellesvig-Waering, 1986; Opistophthalmus C. L. Koch, 1837; Pandinus Thorell, 1876; and Scorpio Linnaeus, 1758.
Geographical distribution: Africa, South and South-East Asia, Indonesia, and Middle East.
Diplocentridae Peters, 1861.
8 genera: Bioculus Stahnke, 1968; Cazierius Francke, 1978; Didymocentrus Kraepelin, 1905; Diplocentrus Peters, 1861; Heteronebo Pocock, 1899; Oieclus Simon, 1880; Tarsoporosus Francke, 1978; and Nebo Simon, 1878.
Geographical distribution: North and Central America, Northern South America, the Caribbean, and Middle East.
Ischnuridae Simon, 1879.
8 genera: Cheloctonus Pocock, 1892; Chiromachetes Pocock, 1899; Chiromachus Pocock, 1893; Hormiops Fage, 1933; Iomachus Pocock, 1893; Liocheles Sundevall, 1833; Opisthacanthus Peters, 1861; and Palaeocheloctonus Lourenço, 1996.
Geographical distribution: Australia, Africa, Central and South America, the Caribbean, India, South-East Asia, the Pacific Islands, and Madagascar.
Urodacidae Pocock, 1893.
1 genus: Urodacus Peters, 1861.
Geographical distribution: Australia.Heteroscorpionidae Kraepelin, 1905.
1 genus: Heteroscorpion Birula, 1903.
Geographical distribution: Madagascar.
Hemiscorpiidae Pocock, 1893.
2 genera: Habibiella Vachon, 1974; and Hemiscorpius Peters, 1861.
Geographical distribution: Middle East.
Hadogenidae Lourenço, 1999§.
1 genus: Hadogenes Kraepelin, 1894.
Geographical distribution: Southern Africa.
Lisposomidae Lawrence, 1928**.
1 genus: Lisposoma Lawrence 1928.
Geographical distribution: South-East Africa.
DISCUSSION AND CONCLUSIONS
As explained at the beginning of this paper, the familial classification of scorpions has changed significantly over the last ten years. Specialists now recognize more than double the number of families they accepted until 1990.
Naturally, not all taxonomists agree on any single or unique classification, and different sub-divisions may therefore be suggested for the same familial group. These differences can be explained as being based on the personal view of each specialist. Certain authors prefer to reduce the number of families, while others have a tendency to subdivide them. These personal views do not explain all the differences of opinion. Some may be the result of the different approaches used in various taxonomic and phylogenetic studies.
Certain authors base their studies exclusively on morphological characters, which are usually exclusively external. Even with an appropriate use of cladistics, it is not always easy to precisely define apomorphic or plesiomorphic characters to achieve the necessary synapomorphies. One reason for this is the limited information that can be obtained from fossil scorpions. Sedimentary fossils are often too badly preserved to be really useful, and scorpions preserved in amber are still rare.
There is optimism today regarding new techniques, especially those based on molecular studies and particular on DNA analysis. This type of approach could undoubtedly contribute to a better definition of natural lineages. Unfortunately, in the case of scorpions, one particular problem still exists: the rarity of specimens. Some populations are very numerous, while others occur at very low densities. Several species are known only from a single specimen. Some genera and even some families have been defined based on very few specimens. For instance, the genus Microcharmus (Microcharmidae) contains 6 species, but only 9 specimens are known. In the case of Pseudouroplectes with two species, three specimens have been found. An exceptional case is exemplified by the genus Troglotayosicus (Troglotayosicidae) with only a single known specimen. This situation is not rare and may persist for several decades. Under such conditions, studies based on molecular biology are not easy.
Finally, taxonomy should not remain isolated from other fields of research. Data from biology, in particular embryology, can certainly help in the clarification of natural lineages. Some preliminary results obtained by Lourenço et al (22,23, unpublished) demonstrate that a precise knowledge of embryonic processes and their variations can provide useful information for a better definition of the familial lineages of scorpions. These biological approaches naturally require a considerable amount of time and work, but when this information is available, it should not be neglected in phylogenetic studies.
|Figure 1. World distribution of scorpions.|
|Figure 2. Bothriurus araguayae Vellard (Bothriuridae), Brazil.|
|Figure 3. Bothriurus rochai Mello-Leitão (Bothriuridae), Brazil.|
|Figure 4. Buthus occitanus (Amoreux) (Buthidae), Morocco.|
|Figure 5. Centruroides gracilis (Latreille) (Buthidae), Mexico.|
|Figure 6. Same species under ultra-violet light.|
|Figure 7. Microcharmus hauseri Lourenço (Microcharmidae), Madagascar.|
|Figure 8. Brotheas granulatus Simon (Chactidae), French Guyana.|
|Figure 9. Scorpiops longimanus (Scorpiopidae), Thailand.|
|Figure 10. Belisarius xambeui Simon (Troglotayosicidae), France.|
|Figure 11. Hadrurus concolorous Stahnke (Iuridae), Mexico.|
|Figure 12. Palaeocheloctonus pauliani Lourenço (Ischnuridae), Madagascar.|
* The authors of families considered here are those defined in the Catalogue of the Scorpions of the World (3). They may, therefore, differ from those indicated in Sissom (29)
Position proposed by Stockwell (30) and accepted by me in 1996(15).§ The characteristics that define the Hadogeninae are outlined in my paper of 1999(19).
** The characteristics that define this family have already been proposed by Lawrence (1928) (12) in his description of it as a sub-family, and redefined by Lamoral (10). After the transfer of this sub-family to the Bothriuridae by Francke (4), Sissom (29) listed it as incertae sedis.
I am very grateful to Prof. John L. Cloudsley-Thompson, London, for reviewing the manuscript.