Mites as fossils: forever small?

Abstract

ABSTRACTSmallness being in the essence of a mite, the question is whether it has always been so during the geological history of Acari. Here I assemble measurements of over 260 published mite fossils, distributed from the Early Devonian (410 mya) to the end of the Neogene (5 mya), and compare them to the data available for their extant relatives. A number of fossils are reconsidered: reports of the Ordovician Brachypylina and Permian Astigmata have to be excluded from the fossil record; Jurassic fossils of Trhypochthoniidae (Nothrina) are reconsidered as Neoliodidae (Brachypylina) and Desmonomata (Brachypylina or Nothrina).Based on these data, mites began small. From the oldest, Paleozoic, fossils through the Jurassic, Sarcoptiformes show a positive size trend, which then ceases. The smallest mites, are recovered from the Triassic amber. Cretaceous amber fossils show wide size range, which further increases through the Cenozoic. Fossils of mites tend to fall within size ranges of their extant relatives mostly on the smaller side of those ranges. Paleozoic fossils, however, tend to be on the larger side of their relatives’ size range. What can be called a “Jurassic anomaly” – a set of much larger-than-extant fossils currently attributed to Cymbaeremaeidae – calls for further study.