title: A 425-million-year-old silurian pentastomid parasitic on ostracods.
abstract: Pentastomids (tongue worms) are worm-like arthropods known today from ∼140 species [1]. All but four are parasitic on vertebrates. Their life cycle typically involves larval development in an intermediate host followed by maturation in the respiratory tract of a definitive terrestrial host. Fossil pentastomids are exceedingly rare and are known only from isolated juveniles [2-6]. The identity of the possible hosts of fossil pentastomids and the origin of their lifestyle have generated much debate. A new, exceptionally preserved species, described based on adults from 425-million-year-old marine rocks, is the only known fossil pentastomid associated with a host, in this case a species of ostracod crustacean. The pentastomids are preserved near eggs within the ostracod and also, uniquely for any fossil or living pentastomid, are attached externally to the host. This discovery affirms the origin of pentastomids as ectoparasitic on marine invertebrates. The terrestrialization of pentastomids may have occurred in parallel with the vertebrate invasion of land.
authors.affiliation: Department of Geology, University of Leicester, Leicester LE1 7RH, UK. Electronic address: djs@le.ac.uk.
authors.forename: David J
authors.initials: DJ
authors.lastname: Siveter
authors.affiliation: Department of Geology & Geophysics and Yale Peabody Museum of Natural History, Yale University, PO Box 208109, New Haven, CT 06520-8109, USA.
authors.forename: Derek E G
authors.initials: DE
authors.lastname: Briggs
authors.affiliation: Earth Collections, Oxford University Museum of Natural History, Oxford OX1 3PW, UK; Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK.
authors.forename: Derek J
authors.initials: DJ
authors.lastname: Siveter
authors.affiliation: Department of Earth Sciences and Engineering, Imperial College London, London SW7 2BP, UK.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Sutton
mesh_terms: D000818:Animals; D003445:Crustacea / Q000033:anatomy & histology*; D005580:Fossils; D021621:Imaging, Three-Dimensional; D013997:Time Factors