The first fossil of the pseudoscorpion family Ideoroncidae (Arachnida: Pseudoscorpiones): A new taxon from the mid-Cretaceous of northern Myanmar

Abstract

Pseudoscorpions have a sparse fossil record although they are among the oldest terrestrial lineages with origins that go back to the Devonian (ca. 385 Ma). Amongst the 25 extant families of pseudoscorpions, only 14 are known from fossils, most of which are preserved in European ambers from the Eocene. Burmese amber from the Cenomanian (mid-Cretaceous) of northern Myanmar is an important source of Mesozoic pseudoscorpion fossils but only six species have been described from this amber to date. In this paper, we establish the first fossil record for the pseudoscorpion family Ideoroncidae Chamberlin, 1930, which is coequally the oldest record of the pseudoscorpion superfamily Neobisioidea. The new genus Proalbiorix is established for the two species P. gracilis sp. nov. and P. compactus sp. nov. which already show all diagnostic features of members belonging to this family to date. Interestingly, Proalbiorix shows morphological features that align the fossils with present-day fauna from the Americas and Africa rather than Asia, which has biogeographical implications. Overall, the description provides another example of relative morphological stasis of pseudoscorpions compared to other arachnid lineages such as spiders, and that all major clades of pseudoscorpions were established long before the Cretaceous.