SHORT COMMUNICATION An opilioacarid mite in Cretaceous Burmese amber Jason A. Dunlop & Leopoldo Ferreira de Oliveira Bernardi Received: 4 April 2014 /Revised: 1 July 2014 /Accepted: 4 July 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract A fossil opilioacarid mite (Parasitiformes: Opilioacarida) in Burmese amber is described as ?Opilioacarus groehni sp. nov. This ca. 99 Ma record (Upper Cretaceous: Cenomanian) represents only the third fossil exam- ple of this putatively basal mite lineage, the others originating from Eocene Baltic amber (ca. 44–49 Ma). Our new record is not only the oldest record of Opilioacarida, but it is also one of the oldest examples of the entire Parasitiformes clade. The presence of Opilioacarida—potentially Opiloacarus—in the Cretaceous of SE Asia suggests that some modern genus groups were formerly more widely distributed across the northern hemisphere, raising questions about previously suggested Gondwanan origins for these mites. Keywords Fossil . Cenomanian . Myanmar . Acari . Opilioacarida . Biogeography Introduction Opilioacarids (Arachnida: Parasitiformes: Opilioacarida) are rare mites, largely restricted to tropical and subtropical regions plus a few records from southern Europe. A single family, Opilioacaridae, encompasses 12 genera, 39 extant species and 1 subspecies (see Supplementary Material for a full list and supporting references). Opilioacarids have been widely perceived as ‘primitive’ mites, expressing features consistent with the general arachnid ground pattern. These include a fairly large body size of a few millimetres, external opisthosomal segmentation and retention of two or three pairs of lateral eyes; see van der Hammen (1976) for terminology. Mites (Acari) are conventionally divided into two major lineages (Krantz and Walter 2009 ): Acariformes (or Actinotrichida) and Parasitiformes (or Anactinotrichida). Phylogenetic analyses typically resolved opilioacarids at the base of the parasitiform branch or, more controversially, as part of a ‘large bodied’ group consisting of opilioacarids, ticks and holothyrid mites, to the exclusion of predatory mites (e.g. Klompen 2010). Despite their supposedly ‘primitive’ status, opilioacarid mites have a very sparse—and comparatively young—fossil record. Acariform mites go back to the early Devonian (ca. 410 Ma; Dunlop et al. 2014), but only two fossil opilioacarids have been described. Both come from Eocene (ca. 44–49 Ma) Baltic amber (Dunlop et al. 2004, 2010) and were assignable (in one case tentatively) to the living genera Opilioacarus With, 1902 and Paracarus Chamberlin & Mulaik, 1942. Here, we describe the first opilioacarid from Cretaceous Burmese amber (Figs. 1 and 2a). At ca. 99 Ma, it doubles the stratigraphic range of the group and is also significant as one of the oldest records of any parasitiform mite. The other examples are two contemporary (99 Ma) tick species (Ixodida), also recovered from Burmese amber. Materials and methods The holotype from the private collection of Carsten Gröhn (Glinde, Germany) will be deposited in the Geological– Palaeontological Institute of the University of Hamburg (GPIH, no. 4549). It was photographed using a Leica Z16 microscope running Leica Application Suite to generate image stacks, combined using Helicon Focus. Drawings were prepared under a Leica MZ12.5 stereomicroscope. Measurements are in Communicated by: Sven Thatje Electronic supplementary material The online version of this article (doi:10.1007/s00114-014-1212-0) contains supplementary material, which is available to authorized users. J. A. Dunlop (*) Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Invalidenstrasse 43, 10115 Berlin, Germany e-mail: Jason.Dunlop@mfn-berlin.de L. F. de Oliveira Bernardi Setor de Ecologia/Departamento de Biologia, Universidade Federal de Lavras, Campus Universitário, Lavras, Minas Gerais, Brazil Naturwissenschaften DOI 10.1007/s00114-014-1212-0 Author's personal copy