title: Microtomography of the Baltic amber tick Ixodes succineus reveals affinities with the modern Asian disease vector Ixodes ovatus.
abstract: Fossil ticks are extremely rare and Ixodes succineus Weidner, 1964 from Eocene (ca. 44-49 Ma) Baltic amber is one of the oldest examples of a living hard tick genus (Ixodida: Ixodidae). Previous work suggested it was most closely related to the modern and widespread European sheep tick Ixodes ricinus (Linneaus, 1758).
  
  
  
  Restudy using phase contrast synchrotron x-ray tomography yielded images of exceptional quality. These confirm the fossil's referral to Ixodes Latreille, 1795, but the characters resolved here suggest instead affinities with the Asian subgenus Partipalpiger Hoogstraal et al., 1973 and its single living (and medically significant) species Ixodes ovatus Neumann, 1899. We redescribe the amber fossil here as Ixodes (Partipalpiger) succineus.
  
  
  
  Our data suggest that Ixodes ricinus is unlikely to be directly derived from Weidner's amber species, but instead reveals that the Partipalpiger lineage was originally more widely distributed across the northern hemisphere. The closeness of Ixodes (P.) succineus to a living vector of a wide range of pathogens offers the potential to correlate its spatial and temporal position (northern Europe, nearly 50 million years ago) with the estimated origination dates of various tick-borne diseases.
authors.affiliation: Museum für Naturkunde, Leibniz Institute for Research on Evolution and Biodiversity, Invalidenstrasse 43, D-10115, Berlin, Germany. jason.dunlop@mfn-berlin.de.
authors.forename: Jason A
authors.initials: JA
authors.lastname: Dunlop
authors.affiliation: United States National Tick Collection, The James H. Oliver, Jr. Institute for Coastal Plain Science, Georgia Southern University, Statesboro, GA, 30460-8056, USA.
authors.forename: Dmitry A
authors.initials: DA
authors.lastname: Apanaskevich
authors.affiliation: Faculty of Geosciences, University of Bremen, D-28357, Bremen, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Lehmann
authors.affiliation: Department of Earth Sciences, Ruhr-Universität Bochum, Institute of Geology, Mineralogy, and Geophysics, D-44801, Bochum, Germany.
authors.forename: René
authors.initials: R
authors.lastname: Hoffmann
authors.affiliation: School of Geosciences, The University of Edinburgh, Grant Institute, King's Buildings, West Mains Road, Edinburgh, EH9 3JW, UK.
authors.forename: Florian
authors.initials: F
authors.lastname: Fusseis
authors.affiliation: Medical Planning Group, Zuse Institute Berlin, Department Visualization and Data Analysis, D-14195, Berlin, Germany.
authors.forename: Moritz
authors.initials: M
authors.lastname: Ehlke
authors.affiliation: Medical Planning Group, Zuse Institute Berlin, Department Visualization and Data Analysis, D-14195, Berlin, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Zachow
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave, Lemont, IL, 60439, USA.
authors.forename: Xianghui
authors.initials: X
authors.lastname: Xiao
mesh_terms: D018647:Amber; D000818:Animals; D004199:Disease Vectors / Q000145:classification; D005060:Europe; D005260:Female; D005580:Fossils / Q000033:anatomy & histology*; D018884:Ixodes / Q000033:anatomy & histology* / Q000145:classification* / Q000235:genetics; D008297:Male; D014054:Tomography / Q000379:methods
chemical_list: D018647:Amber
keywords: Arachnida; Baltic amber; Eocene; Ixodida; Parasite; Parasitiformes; Vector