ELECTROCHAERILUS (SCORPIONES: CHAERILIDAE): ANOTHER PIECE IN THE MESOZOIC SCORPION PUZZLE

Electrochaerilus buckleyi (Lower Cretaceous Burmese amber, Upper Albian; approximate age 98.9-112.2 Ma) has a trichobothrial pattern on the pedipalp chela and other morphological details that allow a definitive family placement in the Chaerilidae, so far represented by its sole extant genus, Chaerilus. This fossil is the most ancient known record for any of the four extant scorpion lineages ("trichobothrial Type B"; parvorder Chaerilida), and the first Mesozoic record of an extant scorpion family. What makes the discovery of Electrochaerilus even more fascinating is that its sister group, the extant genus Chaerilus, is still found in the same geographic region and same type of habitat. The Burmese locality now lies at 25.5°N, while its paleolatitude was 12°N, corresponding to a distinct tropical biota. Electrochaerilus is now the second species of scorpions known from the Cretaceous tropical ecosystem that produced Burmese amber (Burmite) the other being Palaeoburmesebuthus grimaldii Lourenço, of uncertain family placement. Finding representatives of several scorpion families in the same habitat is not unusual; modern tropical ecosystems, including those of Southeast Asia, are normally inhabited by representatives of three to four scorpion families. The Cretaceous fossils of Crato formation in Brazil, approximately of the same age as Burmite, contain representatives of at least two, maybe three families. Investigation of Mesozoic scorpions is crucial for our understanding of the evolution of this "essentially fossil group". Soleglad and Fet suggested that four extant lineages of orthostern scorpions should have been established during Permian to Triassic time. Further, through the Cretaceous, many animal taxa persisted as relicts while other perished during the global restructuring of ecosystems. Among the four extant scorpion lineages, two (parvorders Buthida and Iurida) experienced a Tertiary radiation, while two other lineages (Pseudochactida and Chaerilida) remain only as relicts in Asia, each represented by only one genus. Our current discovery of Electrochaerilus adds another piece to this relict puzzle.