comment on this calibration


 node name
Ecdysozoa     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations Benton et al. 2015
  node minimum age
528.82 Ma
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
636.1 Ma
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.
 primary fossil used to date this node 
GSC 85983
Rusophycus, Hall 1852
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: Burin Peninsula
     Stratum: Member 2, Chapel Island Formation
     Geological age: Cambrian, Paleozoic

More information in Fossilworks   PaleoBioDB

  phylogenetic justification
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).
  phylogenetic reference(s)
Budd, G.E., and Jensen, S. 2000. A critical reappraisal of the fossil record of bilaterian phyla. Biological Reviews, 74:253-295.
 tree image (click image for full size) 
tree image
Figure 1 from Benton et al. (2014).