comment on this calibration


 node name
Cyclostomata     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations Benton et al. 2015
  node minimum age
358.5 Ma
The holotype of Priscomyzon riniensis was recovered from the Fammenian Witpoort Formation (Witteberg Group) at Waterloo Farm, Grahamstown, South Africa. Thus, we established the minimum constraint on the top of the Fammenian, the Devonian-Carboniferous Boundary, which is dated at 358.9 Ma ± 0.4 Myr (Becker et al., 2012).
  node maximum age
636.1 Ma
The soft maximum constraint encompasses the possibility that putative Cambrian vertebrates, such as Haikouichthys, Myllokunmingia (Shu et al., 1999), Zhongjianichthys (Shu, 2003), are crown-cyclostomes. Thus, our soft maximum 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 credibly 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 
AM 5750
Priscomyzon riniensis, Gess et al. 2006
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: Waterloo Farm, Grahamstown
     Stratum: Witpoort Formation
     Geological age: Famennian, Late Devonian, Devonian, Paleozoic

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  phylogenetic justification
Priscomyzon riniensis is unequivocally a member of total-group Petromyzontida, based on morphological phylogenetic analysis (Gess et al., 2006), including the presence of an oral hood, annular cartilages and circumoral teeth.
  phylogenetic reference(s)
Gess, R.W., Coates, M.I., and Rubidge, B.S. 2006. A lamprey from the Devonian period of South Africa. Nature, 443:981-984.
 tree image (click image for full size) 
tree image
Figure 2 from Benton et al. (2014).