title: Earth's oldest 'Bobbit worm' - gigantism in a Devonian eunicidan polychaete.
abstract: Whilst the fossil record of polychaete worms extends to the early Cambrian, much data on this group derive from microfossils known as scolecodonts. These are sclerotized jaw elements, which generally range from 0.1-2 mm in size, and which, in contrast to the soft-body anatomy, have good preservation potential and a continuous fossil record. Here we describe a new eunicidan polychaete, Websteroprion armstrongi gen. et sp. nov., based primarily on monospecific bedding plane assemblages from the Lower-Middle Devonian Kwataboahegan Formation of Ontario, Canada. The specimens are preserved mainly as three-dimensional moulds in the calcareous host rock, with only parts of the original sclerotized jaw walls occasionally present. This new taxon has a unique morphology and is characterized by an unexpected combination of features seen in several different Palaeozoic polychaete families. Websteroprion armstrongi was a raptorial feeder and possessed the largest jaws recorded in polychaetes from the fossil record, with maxillae reaching over one centimetre in length. Total body length of the species is estimated to have reached over one metre, which is comparable to that of extant 'giant eunicid' species colloquially referred to as 'Bobbit worms'. This demonstrates that polychaete gigantism was already a phenomenon in the Palaeozoic, some 400 million years ago.
authors.affiliation: Department of Geology, Lund University, Sölvegatan 12, SE-223 62 Lund, Sweden.
authors.forename: Mats E
authors.initials: ME
authors.lastname: Eriksson
authors.affiliation: Life Sciences Building, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TH, UK.|Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK.
authors.forename: Luke A
authors.initials: LA
authors.lastname: Parry
authors.affiliation: Department of Natural History, Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario, M5S 2C6, Canada.
authors.forename: David M
authors.initials: DM
authors.lastname: Rudkin
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005580:Fossils; D009864:Ontario; D011077:Polychaeta / Q000033:anatomy & histology* / Q000235:genetics