A putative fossil sejid mite (Parasitiformes: Mesostigmata) in Baltic amber re-identified as an anystine (Acariformes: Prostigmata)

The Acari (mites) is currently interpreted to consist of two superorders. In contrast to the relatively rich history of the mite superorder Acariformes, fossils of the Parasitiformes are extremely rare. This is especially true of the most diverse order, Mesostigmata, with only nine families recorded, including four named species, having been described so far. As part of a wider effort to clarify the diversity of Baltic amber Mesostigmata the historically oldest fossil, Sejus bdelloides Koch and Berendt, 1854, is re-examined. While clearly a mite, it is not a mesostigmatan, but a member of the Prostigmata (Acariformes), referable to the Anystina. Thus of the three main mesostigmatan lineages currently recognised both Sejida and Trigynaspida lack a fossil record. Monogynaspida can be traced with confidence back to the Eocene (ca. 44 - 49 Ma).