comment on this calibration


 node name
Rodentia     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations Benton et al. 2015
  node minimum age
56 Ma
An index taxon for the Clarkforkian (Rose, 1981; Anemone and Dirks, 2009), Paramys is known from late Paleocene localities in North America and as such correlates with the Thanetian stage, the minimum bound of which is 56 Ma ± 0.0 Myr = 56 Ma (Gradstein et al., 2012).
  node maximum age
66 Ma
Taxa such as Heomys and Mimotona are Glires, but do not belong within crown Rodentia or Lagomorpha (Meng et al., 2003; Asher et al., 2005). Therefore, a reasonable soft maximum constraint on the base of crown Rodentia could be set by these stem rodents at the base of the Paleocene, at 66.04 Ma ± 0.4 Myr = 66 Ma.
 primary fossil used to date this node 
YPM PU 14200
Paramys atavus, Jepsen, 1937
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: Carbon County, Montana
     Stratum: Fort Union Formation
     Geological age: Cambrian, Paleozoic

More information in Fossilworks   PaleoBioDB

  phylogenetic justification
Phylogenetic analyses place Paramys in Sciuromorpha, the squirrel-related clade, based on characters of the ear region (Korth, 1984; McKenna and Bell, 1997; Marivaux et al., 2004). Paramys is then nested well within crown Rodentia.
  phylogenetic reference(s)
Korth, W.W. 1984. Earliest Tertiary evolution and radiation of rodents in North America. Bulletin of Carnegie Museum of Natural History, 24:1-71.
Marivaux, L., Vianey-Liaud, M., and Jaeger, J.J. 2004. High-level phylogeny of early Tertiary rodents: dental evidence. Zoological Journal of the Linnean Society, 142:105-134.
 tree image (click image for full size) 
tree image
Figure 11 of Benton et al. (2014)