comment on this calibration

Uria - Alle

 node name
Uria - Alle     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations Smith, 2015
  node minimum age
15.97 Ma
The paratype specimen of Miocepphus bohaski was recovered from the lower Calvert Formation (Popes Creek Sand Member) in Hanover County, Virginia, which has been assigned an age of Lower Miocene (Burdigalian; 20.43-15.97 Ma) based on biostratigraphic correlation (de Verteuil and Norris, 1996). The timing of deposition of the Popes Creek Sand Member has been interpreted as being temporally close to the Burdigalian-Aquitanian boundary, and as a result, the age of Miocepphus bohaski was hypothesized to be closer to 20.0 Ma by Wijnker and Olson (2009). However, because age determinations for Miocepphus bohaski are based on biostratigraphic correlation rather than radiometrically derived dates, a more conservative approach is taken herein, and the minimum age provided is that of the Burdigalian-Langhian boundary (i.e., 15.97 Ma). The holotype specimen of Miocepphus bohaski (partial postcranial skeleton; USNM 237270) was recovered from the St. Leonard Member of the Choptank Formation, the age of which has been interpreted as late Middle Miocene (13.82-11.61 Ma; Serravalian) on the basis of biostratigraphic correlation (de Verteuil and Norris, 1996).
  node maximum age
0 Ma
none specified.
 primary fossil used to date this node 
USNM 237142
Miocepphus bohaski, Wijnker and Olson, 2009
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: Popes Creek Sand Member
     Stratum: Calvert Formation
     Geological age: Burdigalian, Miocene, Neogene, Cenozoic

  phylogenetic justification
Miocepphus bohaski was recovered as part of a clade including other species of Miocepphus and the extant species Alle alle in a combined analysis of morphological and molecular sequence data, and the Miocepphus + Alle clade was supported as the nearest outgroup to Uria (Smith, 2011a; Smith and Clarke, 2011). The sister taxon relationship between Uria and Alle is also supported by the results of previous analyses of molecular sequence data (Thomas et al., 2004; Pereira and Baker, 2008).
  phylogenetic reference(s)
Smith, N. A. 2011a. Systematics and evolution of extinct and extant Pan-Alcidae (Aves, Charadriiformes): combined phylogenetic analyses, divergence estimation, and paleoclimatic interactions. PhD Dissertation. The University of Texas at Austin. 748pp
Smith, N. A. and J. A. Clarke. 2011. An alphataxonomic revision of extinct and extant razorbills (Aves, Alcidae): a combined morphometric and phylogenetic approach. Ornithological Monographs 72:1-61.
 tree image (click image for full size) 
tree image
Figure 2 from Smith (2015).