comment on this calibration


Lineage (NCBI): This node has no ancestors.
 node name
Coracioidea     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations Ksepka and Clarke, 2015
  node minimum age
51.57 Ma
USNM 336484 was collected from the Middle unit of the Fossil Butte Member of the Green River Formation in Wyoming, USA. The minimum date of 51.57 Ma incorporates the error associated with an 40Ar/39Ardate of 51.66 ± 0.09Ma obtained from a potassium-feldspar (K-spar) tuff above the fossiliferous horizon containing USNM 336484 (Smith et al., 2008). Because the tuff was deposited several meters above the fossil horizon, this date can be appropriately treated as a hard minimum. There is no evidence of a substantial temporal gap between the fossil horizon and the tuff (Grande and Buchheim, 1994), and so we conservatively consider time elapsed between the deposition of the fossil and the tuff negligible for the purposes of defining a minimum age.
  node maximum age
0 Ma
None specified.
 primary fossil used to date this node 
USNM 336484
Primobucco mcgrewi, Brodkorb, 1970
Location relative to the calibrated node: Stem

[show fossil details]
     Locality: Green River Formation
     Stratum: Fossil Butte Member
     Geological age: Ypresian, Eocene, Paleogene, Cenozoic

More information in Fossilworks   PaleoBioDB

  phylogenetic justification
Phylogenetic analysis of morphological data (Mayr et al. 2004) and combined morphological and molecular data (Clarke et al. 2009) supports placement of Primobucco mcgrewi as a stem roller.
  phylogenetic reference(s)
Mayr, G., Mourer-Chauviré, C., and Weidig, I. 2004. Osteology and systematic position of the Eocene Primobucconidae (Aves, Coraciiformes sensu stricto), with first records from Europe. Journal of Systematic Palaeontology, 2: 1-12.
Clarke, J.A., Ksepka, D.T., Smith, N.A., and Norell, M.A. 2009. Combined phylogenetic analysis of a new North American fossil species confirms widespread Eocene distribution for stem rollers (Aves, Coracii). Zoological Journal of the Linnean Society, 157: 586-611.
 tree image (click image for full size) 
tree image
Figure 5 of Ksepka and Clarke (2014): Phylogenetic tree showing position of Primobucco mcgrewi, illustrating the divergence calibrated by USNM 336484.