comment on this calibration


 node name
Eunectes     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations Head, 2015
  node minimum age
12.375 Ma
The type specimen of E. stirtoni was recovered from the Fish Bed of the Baraya member of the lower Villavieja Formation in the upper Magdalena River valley in central Colombia (Hoffstetter and Rage, 1977). 40Ar/39Ar dating of pumices from the underlying Monkey Beds and overlying San Francisco St. Beds of the Cerro Colorado Member of the Villavieja Formation constrains the ages of the Fish Bed to between 12.649 ± 0.258 and 12.111 ± 0.259 Ma (Flynn et al., 1997). The Fish Bed directly overlies the Monkey Beds, and the minimum age estimate for the Monkey Beds, 12.486 ± 0.111 Ma (Flynn et al., 1997), is used here as the minimum estimate for the Eunectes - Epicrates divergence.
  node maximum age
0 Ma
None specified.
 primary fossil used to date this node 
Eunectes stirtoni, Hoffstetter and Rage, 1977
Location relative to the calibrated node: Stem

[show fossil details]
     Locality: upper Magdalena River valley
     Stratum: Fish Bed of the Baraya member of the lower Villavi
     Geological age: Miocene, Neogene, Cenozoic

  phylogenetic justification
Eunectes stirtoni was erected and united with Eunectes within Boinae on the basis of diagnostic morphology including a shortened posterior margin behind the posterior trigeminal nerve foramen; an incomplete anterior trigeminal nerve foramen, a prominent, long “prootic process” (Tchernov et al., 2000) that forms the lateral edge of a narrow, well defined canal for the Vidian nerve (Hoffstetter and Rage, 1977).
  phylogenetic reference(s)
Tchernov, E., Rieppel, O., Zaher, H., Polcyn, M.J., and Jacobs, L.L. 2000. A fossil snake with limbs. Science, 287:2010-2012.
 tree image (click image for full size) 
tree image
Figure 1 from Head (2015).