comment on this calibration


 node name
Charinidae     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations Head, 2015
  node minimum age
35.2 Ma
Minimum age is based on faunal correlation of Medicine Pole Hills fossil localities (Bowman County, North Dakota) with Flagstaff Rim localities (Natrona County, Wyoming), which are overlain by an ash layer (Ash B) that is 40Ar/39Ar dated at 35.41 ± 0.14 Ma (Obradovich et al., 1995). Smith (2011) recalculated the minimum estimate for the Medicine Pole Hills local fauna at 35.2 Ma.
  node maximum age
0 Ma
None specified.
 primary fossil used to date this node 
PTRM 19607
Calamagras weigeli, Holman, 1972
Location relative to the calibrated node: Stem

[show fossil details]
     Locality: Medicine Pole Hills
     Geological age: Eocene, Paleogene, Cenozoic

More information in Fossilworks   PaleoBioDB

  phylogenetic justification
This fossil preserves apomorphies including caudal vertebrae lacking paired haemapophyses, with haemal keels present. This morphology is only present in Ungaliophis and Exiliboa among extant taxa (Smith, 2013).
  phylogenetic reference(s)
Smith, K.T. 2013. New constraints on the evolution of the snake clades Ungaliophiinae, Loxocemidae and Colubridae (Serpentes), with comments on the fossil history of Erycine boids in North America. Zoologischer Anzeiger, 252:157-182.
 tree image (click image for full size) 
tree image
Figure 1 from Head (2015).