Rare discovery sheds new light on the history and lifestyle of ancient parasite Team recreate fossil using 3D computer modelling Today, some 140 species of the parasite infect animals - including humans An international team of scientists led by the University of Leicester has discovered a new species of fossil in England - and identified it as an ancient parasitic intruder.

The fossil species found in 425-million year old rocks in Herefordshire, in the Welsh borderland, is described as 'exceptionally well preserved.' The specimens range from about 1 to 4 millimeters long.

The fossil species - a 'tongue worm', which has a worm-like body and a head and two pairs of limbs - is actually a parasite whose representatives today live internally in the respiratory system of a host, which it enters when it is eaten.

The new fossil, which was originally entirely soft-bodied, is the first fossil tongue worm species to be found associated with its host, which in this case is a species of ostracod - a group of micro-arthropods (crabs, spiders and insects are also arthropods) with two shells that are joined at a hinge.

Professor David Siveter, of the Department of Geology at the University of Leicester made the discovery working alongside researchers from the Universities of Oxford, Imperial College London and Yale, USA. Their research is published in the journal Current Biology and was supported by The Natural Environmental Research Council, together with the Leverhulme Trust, the John Fell Oxford University Press (OUP) Research Fund and Yale Peabody Museum of Natural History.