comment on this calibration

Muroidea + Ctenohystrica

 node name
Muroidea + Ctenohystrica     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations Benton et al. 2015
  node minimum age
47.6 Ma
The Kuldana Formation of Pakistan has been dated as early–middle Eocene, and ages may differ in different regions of northern India, and mammals occur in different horizons. Birbalomys is noted as occurring at 51 Ma by Marivaux et al. (2004, p. 132), thus well within the Ypresian. Hence, we assign a minimum constraint for rodents excluding the squirrel-like clade at the top of the Ypresian marine stage, hence 47.8 Ma ± 0.2 Myr = 47.6 Ma (Gradstein et al., 2012).
  node maximum age
59.2 Ma
The soft maximum constraint might be taken as equivalent to the age of the ischyromyids and other entirely extinct rodent groups from the late Paleocene (base of the Thanetian) of North America and Europe, 59.2 Ma ± 0.0 Myr = 59.2 Ma.
 primary fossil used to date this node 
H-GSP 92161
Birbalomys, NO REFERENCE
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: Ganda Kas
     Stratum: Kuldana Formation
     Geological age: Eocene, Paleogene, Cenozoic

  phylogenetic justification
Phylogenetic analysis by Marivaux et al. (2004) placed Eocene chapattimyids within the Ctenohystrica, close to hystricognaths and to the exclusion of diatomyids. They are therefore nested within the unnamed crown clade comprising Muroidea and Ctenohystrica.
  phylogenetic reference(s)
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)