comment on this calibration


 node name
Arthropoda     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations Benton et al. 2015
  node minimum age
514 Ma
Yicaris dianensis was recovered from the Yu’anshan Formation at Xiaotan section, Yongshan, Yunnan Province, attributed to the Eoredlichia–Wutingaspis Biozone (Zhang et al., 2007). Chinese Cambrian stratigraphy has been revised substantially and the Eoredlichia – Wutingaspis Biozone is no longer recognized (Peng, 2003; Peng, 2009). However, Eoredlichia is known to co-occur with Hupeidiscus which is diagnostic of the Hupeidiscus-Sinodiscus Biozone which is formally recognised as the second biozone of the Nangaoan Stage of the Qiandongian Series of the Cambrian of China (Peng and Babcock, 2008). The Nangaoan is the proposed third stage of the Cambrian System for the International Geologic Timescale (Peng et al., 2012). Thus, a minimum constraint can be established on the age of the top of the Nangaoan, which has been dated to 514 Ma (Peng and Babcock, 2008; Peng et al., 2012).
  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 
YKLP 10840
Yicaris dianensis, Zhang et al. 2007
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: Yongshan, Yunnan Province
     Stratum: Yu’anshan Formation
     Geological age: Cambrian, Paleozoic

  phylogenetic justification
Yicaris dianensis is an unequivocal member of crown-Crustacea based on the possession of a number of limb-based characters demonstrating not merely eucrustacean, but entomostracan and malacostracan affinity (Zhang et al., 2007).
  phylogenetic reference(s)
Zhang, X.G., Siveter, D.J., Waloszek, D., and Maas, A. 2007. An epipodite-bearing crown-group crustacean from the Lower Cambrian. Nature, 449:595-598.
 tree image (click image for full size) 
tree image
Figure 1 from Benton et al. (2014).