Transactions of the Royal Society of Edinburgh: Earth Sciences

Research Article

The phylogenetic position of the extinct arachnid order Phalangiotarbida Haase, 1890, with reference to the fauna from the Writhlington Geological Nature Reserve (Somerset, UK)

Jessica R. Pollitta1 p1, Simon J. Braddya2 and Jason A. Dunlopa3

a1 Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol, BS8 1RJ, UK.

a2 Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol, BS8 1RJ, UK. e-mail: s.j.braddy@bristol.ac.uk

a3 Institut für Systematische Zoologie, Museum f¨r Naturkunde der Humboldt-Universität zu Berlin, Invalidenstraße 43, D-10115, Berlin, Germany. e-mail: jason.dunlop@museum.hu-berlin.de

ABSTRACT

Study of abundant phalangiotarbid (Arachnida: Phalangiotarbida) material – provisionally assigned here to Bornatarbus mayasii (Haupt in Nindel 1955) – from the Upper Carboniferous of Writhlington, UK, has revealed new information about some previously equivocal characters. The present authors report a trifurcate apotele, possible spiracles on sternite 5, and confirm the presence of 10 opisthosomal tergites plus a dorsal anal operculum. The affinities of phalangiotarbids are obscure, with most authors favouring affinities with Opiliones (harvestmen) and/or Acari (mites and ticks). Phalangiotarbida is scored for characters used in previous studies of arachnid relationships. A cladistic analysis based on 63 characters using 13 terminal arachnid taxa (plus a hypothetical outgroup), resolves Phalangiotarbida as sister group to (Palpigradi + Tetrapulmonata): the taxon Megoperculata sensu Shultz (1990). Even under cladistic analysis, the position of the Phalangiotarbida remains hard to resolve, but a prosomal sternite with distinct sclerites potentially groups them with the Megoperculata.

(Received July 21 2003)

(Accepted January 07 2004)

KEY WORDS

  • Arthropod;
  • Chelicerata;
  • cladistics;
  • morphology;
  • Upper Carboniferous

Correspondence:

p1 Department of Biology and Biochemistry, University of Bath, Bath, BA2 7AY, UK. e-mail: bspjrp@bath.ac.uk