ScienceDaily (Mar. 31, 2010) — A geologist from the University of Leicester is part of a team that has uncovered an ancient water flea-like creature from 425 million years ago -- only the third of its kind ever to be discovered in ancient rocks.
The fossil, illustrated without the shell and showing the soft-parts, including limbs and eyes. (Credit: David J. Siveter, Derek E. G. Briggs, Derek J. Siveter and Mark D. Sutton)
The specimen, which was found in rocks in Herefordshire, represents a new species of ostracod, and has been named Nasunaris flata. Like water-fleas and shrimps, ostracods belong to the group of animals calledCrustacea. The find is important because the fossil has been found with its soft parts preserved inside the shell.
Today its descendents are common, and inhabit ponds, rivers and lakes and many parts of the seas and oceans, having first appeared on Earth about 500 million years ago.
Geologists find ostracods useful in order to help recreate past environments- the type of ostracod found in a rock sample would, for example, help to determine a picture of ancient conditions like water depth and salinity.
The study is published in the Proceedings of the Royal Society B. and in Planet Earth, the online journal of the Natural Environment Research Council.
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Proceedings of the Royal Society B
David J. Siveter1,*, Derek E. G. Briggs2,3, Derek J. Siveter4,5 and Mark D. Sutton6
+Author Affiliations
1Department of Geology, University of Leicester, Leicester LE1 7RH, UK
2Department of Geology & Geophysics, Yale University, PO Box 208109, New Haven, CT 06520-8109, USA
3Peabody Museum of Natural History, Yale University, PO Box 208118, New Haven, CT 06520-8118, USA
4Geological Collections, University Museum of Natural History, Oxford OX1 3PW, UK
5Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR, UK
6Department of Earth Sciences and Engineering, Imperial College London, London SW7 2BP, UK
*Author for correspondence (djs@leicester.ac.uk).
Abstract
An exceptionally preserved new ostracod crustacean from the Silurian of Herefordshire, UK, represents only the third fully documented Palaeozoic ostracod with soft-part preservation. Appendages, gills, gut system, lateral compound eyes and even a medial eye with a Bellonci organ are preserved, allowing assignment of the fossil to a new genus and species of cylindroleberidid myodocope (Myodocopida, Cylindroleberididae). The Bellonci organ is recorded for the first time in fossil ostracods. The find also represents a rare occurrence of gills in fossil ostracods and confirms the earliest direct evidence of a respiratory-cum-circulatory system in the group. The species demonstrates remarkably conserved morphology within myodocopes over a period of 425 Myr. Its shell morphology more closely resembles several families of myodocopes other than the Cylindroleberididae, especially the Cypridinidae and Sarsiellidae, thus questioning the utility of the carapace alone in establishing the affinity of fossil ostracods.
cylindroleberidid exceptional preservation Herefordshire Lagerstätte Myodocopa Ostracoda Silurian
Footnotes
Received November 20, 2009.
Accepted January 6, 2010.
© 2010 The Royal Society
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