Lineage (NCBI): root » Eukaryota » Opisthokonta » Metazoa » Eumetazoa » Bilateria » Coelomata » Protostomia » Lophotrochozoa
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http://palaeo-electronica.org/content/fc-1 Benton et al. 2015
node minimum age |
Rusophycus occurs well below the first animal body fossils in Cambrian sections around the world (Crimes and Jiang, 1986; Crimes, 1987; Goldring and Jensen, 1996; Macnaughton and Narbonne, 1999; Weber and Zhu, 2003). In many of these regions, records of Rusophycus begin with proximity to the base of the Cambrian. However, their ages are only well constrained in sections in Newfoundland, Canada and Yunnan, China. Of these, records of Rusophycus begin low in Member 2 of the Chapel Island Formation of the southwestern Burin Peninsula of southeastern Newfoundland, defining the base of the Rusophycus avalonensis Biozone (Narbonne et al., 1987). The Biozone is itself dated through correlations to a section in New Brunswick where are younger ash bed has been dated by U-Pb series to 530.02 Ma ± 1.2 Myr (Isachsen et al., 1994; Peng et al., 2012), thus providing for a minimum constraint of 528.82 Ma.
node maximum age |
A soft maximum constraint is based on the maximum age interpretation of the Lantian Biota (Yuan et al., 2011). This, together with the Doushantuo Biota (Yuan et al., 2002), provides a series of Lagerstätten preserving the biota in Orsten- and Burgess Shale-like modes of fossilization. None of these Lagerstätten, least of all the Lantian, preserves anything that could possibly be interpreted as even a total group eumetazoan and on this basis we define out soft maximum constraint at 635.5 Ma ± 0.6 Myr (Condon et al., 2005) and, thus, 636.1 Ma.
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Rusophycus trace fossils are widely accepted to have been produced by arthropod-grade organisms, showing bilateral symmetry and evidence of segmented limbs used in their construction, an apomorphy of Arthropoda (Budd and Jensen, 2000).
Budd, G.E., and Jensen, S. 2000. A critical reappraisal of the fossil record of bilaterian phyla. Biological Reviews, 74:253-295.
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