Terrestrial isopods: progress in their fossil record

Currently, terrestrial isopods (Crustacea: Oniscidea) represent a large part of the mesofauna and primary decomposers in soil. For a long time, terrestrial isopods were believed to be a recent group, their fossil record being quite scarce and, until recently, restricted to the Cenozoic. However, several terrestrial isopods have been recently reported in Cretaceous ambers. The first to be formerly described – Myanmariscus deboiseae Broly, Maillet & Ross, 2015, is of late Early Cretaceous age (Albian) and is preserved in Burmese amber from Myanmar. This specimen belongs to the Synocheta Legrand, 1946 and its assignment to the family Styloniscidae Vandel, 1952 is discussed in regards to the biogeographical distribution of Recent species of Oniscidea. A second piece of Burmese amber, currently under study, contains a specimen probably belonging to the Tylidae Milne-Edwards, 1840 and to the genus Tylos Audouin, 1826, a genus currently composed of supralittoral endemic species. There is also a third Bumese amber specimen that was recently acquired by the National Museum of Scotland, and yet to be studied, that contains four individuals. These Burmese specimens, along with other, as yet undescribed, Cretaceous amber records from Western Europe (Charente Maritime, France; Álava, Spain) indicate that Oniscidea were already highly diversified by the Cretaceous. Furthermore, the progressive discovery of a rich Mesozoic fossil record considerably improves our knowledge of the evolutionary history of this remarkable group of terrestrial crustaceans.