Editor's Summary
10 January 2008
Like shelling worms
Machaeridians are small shell-like fossils, abundant in marine seafloor settings from the early Ordovician to the Carboniferous. Since the fossils were first reported 150 years ago, they have been variously assigned to arthropods, echinoderms, annelids and molluscs. A new find in Morocco resolves these problematic affinities, because the animal's soft parts are well preserved. The 'shells' are in fact calcareous plates, carried as armour on the back of a hitherto unknown form of segmented annelid worm.
News and Views: Palaeontology: Ancient worms in armour
It requires a quirk of fossilization for the soft parts of an animal to be preserved. Study of such a specimen of the mysterious machaeridians provides these organisms with a well defined evolutionary home.
Jean-Bernard Caron
doi:10.1038/451133a
Letter: Machaeridians are Palaeozoic armoured annelids
Jakob Vinther, Peter Van Roy & Derek E. G. Briggs
doi:10.1038/nature06474
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