comment on this calibration

Synthliboramphus craveri - S. hypoleucus

 node name
Synthliboramphus craveri - S. hypoleucus     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations Smith, 2015
  node minimum age
1.5 Ma
The age of the San Diego Formation sediments from which the holotype specimen of Synthliboramphus rineyi was recovered was reviewed by Wagner et al. (2001). Based on microfaunal analysis and correlation with mammalian and molluskan assemblages of known age, the age of San Diego Formation is estimated to range from 3.6-1.5 Ma (i.e., Middle Pliocene to Early Pleistocene; Piacenzian-Calabrian; Wagner et al., 2001). The San Diego Formation was divided into 7 stratigraphic sub-units by Wagner et al. (2001). Paleomagnetic analysis indicates that sub-unit two can be correlated with Gilbert Chron C2Ar and Gauss Chron C2An.3n boundary, which has been assigned an age of 3.6 Ma (Wagner et al., 2001). However, the provenance of the holotype specimen within the San Diego Formation (i.e., what sub-unit it was collected from) is uncertain. Therefore the more conservative date of 1.5 Ma is recommended with respect to the age assignment of this specimen for divergence time analyses.
  node maximum age
0 Ma
none specified.
 primary fossil used to date this node 
UCMP 61590
Synthliboramphus rineyi , Chandler, 1990
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: San Diego Formation
     Stratum: San Diego Formation
     Geological age: Calabrian, Pleistocene, Quaternary, Cenozoic

  phylogenetic justification
Synthliboramphus rineyi was recovered in a clade with Synthliboramphus hypoleucus and Synthliboramphus craveri in the results of a combined phylogenetic analysis of morphological and molecular sequence data (Smith, 2011a). The referral of Synthliboramphus rineyi to Synthliboramphus has not been questioned.
  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 2 from Smith (2015).