title: The impact of taphonomic data on phylogenetic resolution: Helenodora inopinata (Carboniferous, Mazon Creek Lagerstätte) and the onychophoran stem lineage.
abstract: BACKGROUND
  The origin of the body plan of modern velvet worms (Onychophora) lies in the extinct lobopodians of the Palaeozoic. Helenodora inopinata, from the Mazon Creek Lagerstätte of Illinois (Francis Creek Shale, Carbondale Formation, Middle Pennsylvanian), has been proposed as an intermediate between the "weird wonders" of the Cambrian seas and modern terrestrial predatory onychophorans. The type material of H. inopinata, however, leaves much of the crucial anatomy unknown.
  
  
  RESULTS
  Here we present a redescription of this taxon based on more complete material, including new details of the head and posterior portion of the trunk, informed by the results of experimental decay of extant onychophorans. H. inopinata is indeed best resolved as a stem-onychophoran, but lacks several key features of modern velvet worms including, crucially, those that would suggest a terrestrial mode of life.
  
  
  CONCLUSIONS
  The presence of H. inopinata in the Carboniferous demonstrates the survival of a Cambrian marine morphotype, and a likely post-Carboniferous origin of crown-Onychophora. Our analysis also demonstrates that taphonomically informed tests of character interpretations have the potential to improve phylogenetic resolution.
authors.affiliation: Department of Geology, University of Leicester, University Road, Leicester, LE1 7RH, UK. duncan.murdock@le.ac.uk.
authors.forename: Duncan J E
authors.initials: DJ
authors.lastname: Murdock
authors.affiliation: Department of Geology, University of Leicester, University Road, Leicester, LE1 7RH, UK. sg21@le.ac.uk.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Gabbott
authors.affiliation: Department of Geology, University of Leicester, University Road, Leicester, LE1 7RH, UK. mark.purnell@le.ac.uk.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Purnell
mesh_terms: D005075:Biological Evolution; D056890:Eukaryota / Q000145:classification*; D005580:Fossils; D010802:Phylogeny; D018515:Plant Leaves