Protochactidae Magnani, Stockar & Lourenço, 2022, new family
Creators: name: Magnani, Fabio
name: Stockar, Rudolf
name: Lourenço, Wilson R.
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Scorpiones
Protochactidae

description: 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.
description: Published as part of 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), pp. 1-7 in Faunitaxys 10 (24) on page 4, DOI: 10.57800/faunitaxys-10(24), http://zenodo.org/record/15352441