Springtails from the Early Cretaceous Amber of Spain (Collembola: Entomobryomorpha), with an Annotated Checklist of Fossil Collembola

Entomobryomorphan springtails (Hexapoda: Entognatha: Collembola) of the family Isotomidae are the most numerous group of Collembola in Spanish amber, a pattern typical in other studied Cretaceous amber deposits. Here we provide a revision of the Spanish amber springtail fauna, Early Cretaceous (Late Albian) in age, based on 93 specimens sufficiently well preserved to permit specific identification. Three new species are erected within the Isotomidae: Anurophorinae. These are: Burmisotoma spinulifera, new species, Protoisotoma autrigoniensis, new species, and Proisotoma communis, new species. The two former are respectively placed in the Cretaceous genera Burmisotoma Christiansen and Nascimbene (previously known from Cenomanian Burmese amber) and Protoisotoma Christiansen and Pike (in both Burmese and Canadian ambers), while the last species is indistinguishable from the extant, cosmopolitan genus Proisotoma Borner (also recorded in Burmese amber). Low morphological intraspecific variability is described for P. communis. Taxa are discussed in relation to other fossil entomobryomorphan lineages as well as their modern counterparts. A catalog of the known fossil springtails is appended. Isotomidae are diverse springtails, putatively basal among Entomobryomorpha and extending back into the Early Devonian. Indeed, taxa described herein are overall remarkably similar to their extant relatives, emphasizing the antiquity and morphological stasis of the group as a whole.