Thursday, December 13, 2012

Paleozoic Soft Tissue Preservation in Ostracods

A Silurian myodocope with preserved soft-parts: cautioning the interpretation of the shell-based ostracod record. Siviter, D.J., et al. Proc. R Soc. B 280 (1752), Feb., 2013.

Ventral view of the fossil Pauline avibella. Credit: D.J. Siveter, D. E. G. Briggs, D. J. Siveter, M. D. Sutton & S. C. Joomun.
Abstract: Ostracod crustaceans are the most abundant fossil arthropods. The Silurian Pauline avibella gen. et sp. nov., from the Herefordshire Lagerst├Ątte, UK, is an extremely rare Palaeozoic example with soft-part preservation. Based on its soft-part morphology, especially the exceptionally preserved limbs and presence of lateral eyes, it is assigned to the myodocopid myodocopes. The ostracod is very large, with an epipod on the fifth limb pair, as well as gills implying the presence of a heart and an integrated respiratory–circulatory system as in living cylindroleberidid myodocopids. Features of its shell morphology, however, recall halocyprid myodocopes and palaeocopes, encouraging caution in classifying ostracods based on the carapace alone and querying the interpretation of their shell-based fossil record, especially for the Palaeozoic, where some 500 genera are presently assigned to the Palaeocopida.