comment on this calibration


 node name
Chordata     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations Benton et al. 2015
  node minimum age
514 Ma
The Chengjiang Biota occurs within the Yu’anshan Member of the Heilinpu Formation, which is assigned to the Eoredlichia-Wutingaspis Biozone (Hou et al., 2004), and occurs above the first appearance of trilobites. While the dating of the Eoredlichia-Wutingaspis Biozone is problematic because the fauna is endemic, the first stratigraphic appearance of trilobites is the proposed definition of the base of Cambrian Series 2 (Peng et al., 2012), the lower part of which (proposed Cambrian Age 3 (Peng et al., 2012)) is equivalent to the Nangaoan of South China (Peng, 2003) and encompasses fully the Chengjiang Biota (Peng et al., 2012). This allows us to establish the maximum age of the Chengjiang Biota on the base of the Nangoan which is given as 521 Ma in GTS 2012 (Peng et al., 2012). The minimum age is more problematic in that a more precise constraint relies on the assumption that the Eoredlichia-Wutingaspis Biozone of the Qiongzhusian Stage is equivalent to the Atdabanian (Hou et al., 2004), which has been substantiated well. Alternatively, we use the age of the Nangaoan-Duyunian Boundary, which is dated at 514 Ma in GTS 2012 (Peng et al., 2012), which relies on a geochronological date from close to this boundary, within the Nangaoan, in Shropshire (Harvey et al., 2011).
  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), provide 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 
YGSK HZ-f-12-127
Haikouichthys ercaicunensis , Luo, Hu, and Shu, 1999
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: Haiku
     Stratum: u’anshan Member of the Heilinpu Formation
     Geological age: Cambrian, Paleozoic
     [View locality in Paleobiology Database]

More information in Fossilworks   PaleoBioDB

  phylogenetic justification
While the crown-vertebrate affinity of Haikouichthys ercaicunensis is contested within the context of cyclostome monophyly, its crown-chordate affinity is not, on the basis of phylogenetic analysis by R. S. Sansom et al. (2010).
  phylogenetic reference(s)
Sansom, R.S., Freedman, K., Gabbott, S.E., Aldridge, R.J., and Purnell, M.A. 2010. Taphonomy and affinity of an enigmatic Silurian vertebrate, Jamoytius kerwoodi White. Palaeontology, 53:1393-1409.
 tree image (click image for full size) 
tree image
Figure 2 from Benton et al. (2014).