comment on this calibration


 node name
Alcidae     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations Smith, 2015
  node minimum age
34.2 Ma
The oldest fossil pan-alcid is from Late Eocene deposits of the Hardie Mine located in Gordon, Georgia USA (Chandler and Parmley, 2002). Fossils of sharks, rays, bony fishes, snakes, and the auk specimen (GCVP 5690) have been recovered from an approximately one meter thick, in situ bed of the Late Eocene Clinchfield Formation, a basal unit of the Barnwell Group (Huddelstun and Hetrick, 1986; Westgate, 2001). The Hardie Mine exposures of the Clinchfield Formation are a discrete fossiliferous unit with no evidence of mixing with older or younger bounding units (Parmley and Holman, 2003). Evidence from shark, mammalian, mollusk, and dinocyst assemblages support a Late Eocene age for the Clinchfield Formation sediments exposed at Hardie Mine (Parmley and Holman, 2003). The dinocyst assemblage is correlated with assemblages from other localities in Georgia and South Carolina that are placed in calcareous nannofossil zone NP 19/20, and have been assigned an age of 36.0-34.2 Ma. Congruent with the criteria proposed by Parham et al. (2012), the youngest possible date (34.2 Ma) is suggested here as a hard minimum bound on the age of divergence between crown Alcidae and Stercorariidae.
  node maximum age
0 Ma
none specified.
 primary fossil used to date this node 
GCVP 5690
Pan-Alcidae incertae sedis , NO REFERENCE
Location relative to the calibrated node: Stem

[show fossil details]
     Locality: rdie Mine, Gordon, Georgia USA
     Stratum: Clinchfield Formation
     Geological age: Priabonian, Eocene, Paleogene, Cenozoic

  phylogenetic justification
GCVP 5690 was included in a combined analysis of morphological and molecular sequence data by Smith (2011a). The results of that analysis were inconclusive regarding the position of the taxon represented by GCVP 5690, hence the designation Pan-Alcidae incertae sedis. No alternative hypothesis has been proposed linking this specimen to any clade other than Pan-Alcidae. The sister taxon relationship between Pan-Alcidae and Stercorariidae is supported by analyses of morphological and molecular sequence data (Baker et al., 2007; Pereira and Baker, 2008; Smith, 2011a,b).
  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
 tree image (click image for full size) 
tree image
Figure 1 from Smith (2015).