Fossil Pediculochelidae mites from Cretaceous and Eocene amber

Source image stacks of type specimens, dataset for the paper
First fossil evidence of pediculochelid mites: Two new species from Middle Cretaceous and Late Eocene amber revealing morphological stasis over at least 99 million years
Vasiliy B. Kolesnikov, Dmitry D. Vorontsov, Roy A. Norton, Pavel B. Klimov
We present the first fossil evidence of pediculochelid mites, describing two new species: Paralycus ekaterinae sp. nov. (Eocene amber) and P. primus sp. nov. (Cretaceous amber). The exceptional preservation of the amber fossils, coupled with our newly developed methodological approach for examining minute arthropods in amber, has facilitated a detailed comparative morphological assessment at a resolution comparable to that of contemporary species, providing significant insights into their anatomical features. The observed morphological continuity between fossil and modern pediculochelid mites indicates the evolutionary stability of this lineage in the genus Paralycus spanning at least 99 million years. These findings not only advance our knowledge of the evolutionary history of Pediculochelidae but also offer a broader perspective on the persistence of morphological traits over extensive geological timescales. We also address the phenomenon of phoresy within Paralycus and explore its potential implications for dispersal mechanisms. Furthermore, we evaluate the relationship between the dimensions of the amber imprints and the original size of the mites, contributing to our understanding of the mechanisms of microarthropod preservation in amber.
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Compound microscopes Nikon E-800 with water (40x and 60x) and oil (100x) immersion optics and Zeiss AxioImager A2 with dry (40x, 63x) and oil immersion optics (100x) were used, with brightfield, polarized, differential interference contrast and incident illumination. Stacks of images, comprising multiple focal planes, were obtained with Olympus OM-D E-M10-II digital camera. Images were treated for color, digital noise and sharpness with Adobe Lightroom.
Fluorescence imaging was performed using a Zeiss LSM-880 confocal laser scanning microscope (CLSM) equipped with an Airyscan super-resolution detector.