comment on this calibration


 node name
Charininae     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations Head, 2015
  node minimum age
18.7 Ma
The minimum age is derived from radiometric dating of the Eagle Crag Ash, which overlies the top of the Harrison Formation, to 19.2 ± 0.5 Ma (MacFadden and Hunt, 1998; Tedford et al., 2004). Tedford et al. (2004, figure 6.2) indicate the top of the Harrison Formation may be as old as 20 Ma.
  node maximum age
0 Ma
None specified.
 primary fossil used to date this node 
USNM 125562
Charina indet., NO REFERENCE
Location relative to the calibrated node: Stem

[show fossil details]
     Locality: Armstrong Ranch Quarry
     Stratum: Harrison Formation
     Geological age: Miocene, Neogene, Cenozoic

  phylogenetic justification
UNSM 125562 is referred to the total clade of Charina (all fossil taxa more closely related to extant Charina than extant Lichanura) on the basis of the following caudal vertebral characters: 1) caudal tailclub composed of more than six vertebrae; 2) laterally expanded, lobate distal neural spine; 3) Anteriorly directed pterapophyses (=“postzygapophyseal wing” of Szyndlar, 1994) present (Kluge, 1993; Szyndlar, 1994; Parham et al., 2012).
  phylogenetic reference(s)
Kluge, A.G. 1993. Aspidites and the phylogeny of pythonine snakes. Records of the Australian Museum Supplement , 19:1-77.
Szyndlar, Z. 1994. Oligocene snakes of southern Germany. Journal of Vertebrate Paleontology, 14:24-37.
Parham, J.F., Donoghue, P.C.J., Bell, C.J., Calway, T.D., Head, J.J., Holroyd, P.A., Inoue, J.G., Irmis, R.B., Joyce, W.G., Ksepka, D.T., Patańe, J.S.L.N., Smith, D., Tarver, J.E., van Tuinen, M., Yang, Z., Angielczyk, K.D., Greenwood, J., Hipsley, C.A., Jacobs, L.L., Makovicky, P.J., Müller, J., Smith, K.T., Theodor, J.M., Warnock, R.C.M., and Benton, M.J. 2012. Best practices for applying paleontological data to molecular divergence dating analyses. Systematic Biology, 61:346-359.
 tree image (click image for full size) 
tree image
Figure 1 from Head (2015).