Protochactidae, Magnani & Stockar & Lourenço, 2022

Magnani, Fabio, Stockar, Rudolf & Lourenço, Wilson R., 2022, A new family, genus and species of fossil scorpion from the Meride Limestone (Middle Triassic) of Monte San Giorgio (Switzerland), Faunitaxys 10 (24), pp. 1-7 : 4

Protochactidae new family, Lourenço, Magnani & Stockar

ZooBank:http://zoobank.org/ 3824F219-DAC3-457C-A65C-E7AE2E6847C3

Unlike several amber Cretaceous fossils (e. g. Lourenço, 2001, 2003, 2015a,b, 2018), previously described Mesozoic scorpion fossils from Jurassic and Triassic have not been assigned to any extant superfamily ( Sissom, 1990). The first exception was the description of the family Protobuthidae ( Lourenço & Gall, 2004) . A careful analysis of several characters presented by the new fossil element described here led us to conclude that it can actually be placed in the superfamily Chactoidea sensu Lourenço (2000) . The new fossil family proposed, Protochactidae fam. nov. shows a number of affinities with the Cretaceous fossil family Palaeoeuscorpiidae Lourenço, 2003 , but equally with the extant families Euscorpiidae Laurie, 1896 and Chactidae Pocock 1893 . A number of characters are however divergent and the geological horizon totally distinct from present environments; consequently the new fossil scorpion rather suggests a possible proto-element (sedis mutabilis) for these two families.

Etymology. – Familial name is an association of Proto (from Greek, which means first, original) and the family name Chactidae .

Diagnosis for the new family

Scorpion of small size with 27.0 mm in total length. The holotype is most probably an adult or pre-adult. Body and appendages rather bulk. Carapace rather smooth with the anterior margin slightly convex; presence of some vestigial carinae and some shallow furrows; median ocular tubercle conspicuous and slightly anterior to the centre of the carapace;median eyes moderate in size and separated by less than one ocular diameter; two pairs of conspicuous lateral eyes. Mesosomal tergites rather smooth with one vestigial median carinae; some weak carinae present on tergites VI and VII. Metasomal segments with strongly marked dorsal and sub-dorsal carinae; ventral carinae apparently absent. Telson with a globular vesicle, almost rounded and flattened dorso-ventrally; aculeus shorter than the vesicle and weakly curved; subaculear tubercle absent. Ventral characters are not observable. Trichobothrial pattern extremely incomplete, and only a few bothria can be detected; these suggest the fundamental type C ( Vachon, 1974). The following trichobothria can be observed: 2-3 dorso-external on chela manus, namely Db, and two Eb; 2 dorsal and one internal on patella; 1 dorsal, 1 external and 1 internal on femur. Dentate margins of fixed finger probably composed of a single linear row of granules. Chelicera poorly observable, but 2-3 teeth on fixed finger and 3-4 on movable finger can be suggested ( Vachon, 1963). Legs: tibial spurs not observable.