HUBBARDIINAE COOK, 1899

Magnussen, Ilian De Francesco, Müller, Sandro P., Hammel, Jörg U., Kotthoff, Ulrich & Harms, Danilo, 2022, Diversity of schizomids (Arachnida: Schizomida) revealed by new fossil genera and species from mid-Cretaceous Burmese amber with implications for a Gondwanan origin of the Burma Terrane, Zoological Journal of the Linnean Society 196, pp. 792-844 : 795

SUBFAMILY HUBBARDIINAE COOK, 1899

Remarks

There are three schizomid families: Protoschizomidae , Hubbardiidae and the extinct Calcitronidae . The status of Calcitronidae as a valid family is still contradictory because the tarsomere formula of 7:5:4:4 (Pierce, 1951) deviates from the general pattern of 7:3:3:3 shared by Protoschizomidae , Hubbardiidae and Thelyphonida ( Cokendolpher & Reddell, 1992). The presence of six tarsomeres on legI is a rare occurrence in Old and New World schizomids alike and has been interpreted as a randomly occurring malformation caused by regeneration of a limb after loss or damage ( Rowland, 1973). The two Recent families for schizomids can be distinguished by 29 morphological characters ( Cokendolpher & Reddell, 1992; Monjaraz-Ruedas et al., 2017). Out of these characters, only the symmetry of the tarsal spurs (symmetrical in Protoschizomidae , asymmetrical in Hubbardiidae ), body size (usually between 6 and 9 mm in Protoschizomidae and ~ 3–6 mm in Hubbardiidae ), male and female flagellum morphology and the setation of the base of the anterior process (present in Protoschizomidae , absent in Hubbardiidae ) can be assessed in the amber fossils owing to fossil preservation, but all of the described fossil specimens align well with the diagnosis for Hubbardiidae .

Within this family, the Megaschizominae (endemic to southern Africa) have a body size of ~ 8 mm, a row of eight or nine setae along the frontal margin of the propeltidium, and their tergites II–VII on the opisthosoma have two submarginal rows of setae, whereas Hubbardiinae are smaller and have only one row. All fossil species align with Hubbardiinae rather than with Megaschizominae. The key provides basic diagnoses for all fossil genera described from Burmese amber. As the fossil schizomids are often altered and deformed by taphonomical processes, a schizomid body plan with labelling of body parts is given in Figure 2 for a better understanding of the morphology.

Figures

Figure 2. Basic male schizomid body plan in dorsal (A) and in ventral (B) view. See Material and methods for explanation of abbreviations. Abbreviation: I-XII, tergites I-XII.