comment on this calibration


 node name
Verunipeltata     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations
Wolfe et al. 2016
  node minimum age
79.01 Ma
The holotype of U. yehoachi was collected from a chert bank in the Chert Member of the Mishash Formation, near the city of Arad, Israel (Hof, 1998). The chert banks are within the Hoplitoplacenticeras marroti ammonite biiozone (Reiss et al., 1986). H. marroti co-occurs with Baculites sp. (smooth) (Lehmann and Murphy, 2001), which is dated to the uppermost early Campanian. Based on a spline-fit of interbedded bentonites, the base of the Tethyan Baculites sp. (smooth) Zone is dated to 79.64 Ma, with a duration of 0.63 Myr (Ogg et al., 2012a), thus the minimum age of U. yehoachi is 79.01 Ma.
  node maximum age
521 Ma
A soft maximum age is obtained from the oldest mandibulate,Y. dianensis, which was recovered from the Yu'anshan Formation at Xiaotan section, Yongshan, Yunnan Province, attributed to the Eoredlichia–Wutingaspis Biozone (Zhang et al., 2007). Chinese Cambrianstratigraphy has been revised substantially and the Eoredlichia –Wutingaspis Biozone is no longer recognized (Peng, 2003, 2009).However, Eoredlichia is known to co-occur with Hupeidiscus, which is diagnostic of the Hupeidiscus-Sinodiscus Biozone, which is formally recognized 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., 2012a).Thus, a soft maximum constraint can be established on the age of the lower boundary of the Nangaoan, which has been dated to 521 Ma (Peng et al., 2012a; Peng and Babcock, 2008).
 primary fossil used to date this node 
SMNS 67703
Ursquilla yehoachi, Remy and Avnimelech, 1955
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: Arad
     Stratum: Chert Member of the Mishash Formation,
     Geological age: Cretaceous, Mesozoic

  phylogenetic justification
The uropod morphology of U. yehoachi indicates its membership in the crown group of Verunipeltata. The uropodal exopod of U. yehoachi specimen SMNS 67703 is bipartite, a synapomorphy of Verunipeltata (Haug et al., 2013). Furthermore, U. yehoachi shares several characters with Squillidae (Squilloidea), such as prelateral lobes, submedian teeth with fixed apices and a subquadrate telson (Haug et al., 2013). As U. yehoachi has not been included in a phylogenetic analysis, it is uncertain whether it falls within crown Squilloidea (Haug et al., 2013) or on its stem; either position would remain within the crown group of Verunipeltata.
  phylogenetic reference(s)
Haug, C., Kutschera, V., Ahyong, S.T., Vega, F.J., Maas, A., Waloszek, D., and Haug, J.T. 2013. Reevaluation of the Mesozoic mantis shrimp Ursquilla yehoachi based on new material and the virtual peel technique. Palaeontologia Electronica 16: 1–14.
 tree image (click image for full size) 
tree image
Figure 13 from Wolfe et al. (2016).