ScienceDaily (Mar. 18, 2010) — Scientists have unearthed the remains of one of the world's rarest fossils -- in downtown Ottawa, Canada. The 450-million-year-old fossil preserves the complete skeleton of a plumulitid machaeridian, one of only 8 such specimens known. Plumulitids were annelid worms -- the group including earthworms, bristleworms and leeches, today found everywhere from the deepest sea to the soil in your yard -- and although plumulitids were small they reveal important evidence of how this major group of organisms evolved.
The fossil specimen, with the trilobite towards the left, and the remains of the extremely rare plumulitid towards the right. Images below show a close up the plumulitid (actual size is 16 mm long), and a reconstruction of how it would have looked during life. (Credit: Fossil images by Jakob Vinther and David Rudkin, copyright Royal Ontario Museum / Reconstruction by Esben Horn, www.10tons.dk)
The fossil is described by Vinther and Dave Rudkin, of Toronto's Royal Ontario Museum, in the current issue of the journal Palaeontology.
It was Rudkin who first recognised its scientific significance: "This nifty little specimen first came to my notice when I received a letter from an amateur fossil collector in Nepean, Ontario. In prospecting for fossils in rock from a temporary building excavation he had turned up a small block containing a complete trilobite, but next to it was something else and he sent me a slightly fuzzy but very intriguing photo. The mystery fossil was clearly not another trilobite, and I although couldn't be certain, I thought it might be some sort of annelid worm with broad, flattened scales. James, the collector, generously agreed to lend me the specimen and I realised immediately it was a complete, fully articulated machaeridian! The first I had ever seen."
...
Read more here/Leia mais aqui: Science Daily
+++++
Volume 53 Issue 2, Pages 327 - 334
Published Online: 23 Feb 2010
© The Palaeontological Association, 2010
The first articulated specimen of Plumulites canadensis (Woodward, 1889) from the Upper Ordovician of Ontario, with a review of the anterior region of Plumulitidae (Annelida: Machaeridia)
by JAKOB VINTHER* and DAVID RUDKIN†
*Department of Geology and Geophysics, Yale University, 210 Whitney Avenue, PO Box 208109, New Haven, CT 06520, USA; emailjakob.vinther@yale.edu
†Department of Natural History (Paleontology), Royal Ontario Museum, 100 Queen's Park, Toronto, ON M5S 2C6, Canada; emaildavidru@rom.on.ca
KEYWORDS
machaeridians • plumulitids • segmentation • head region • exceptional preservation
ABSTRACT
Abstract. Articulated plumulitid machaeridians are rarely preserved intact. Here, we describe a complete specimen of Plumulites canadensis (Woodward, 1889) retaining much of the head region. The two anteriormost pairs of shell plates are quite distinct from the rest in outline, density of concentric rugae, and especially the radial ornamentation of the second pair. We demonstrate that the latter condition is present in other complete plumulitids and therefore widespread, which elucidates a larger diversity in morphology of plumulitids than realized previously.
Typescript received 10 December 2008; accepted in revised form 23 June 2009
DIGITAL OBJECT IDENTIFIER (DOI)10.1111/j.1475-4983.2010.00938.x
+++++
Professores, pesquisadores e alunos de universidades públicas e privadas com acesso ao site CAPES/Periódicos podem ler gratuitamente este artigo da Paleontology e de mais 22.440 publicações científicas.
