comment on this calibration


 node name
Marsupialia     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations Benton et al. 2015
  node minimum age
47.6 Ma
The early Eocene locality of Murgon, source of Djarthia, correlate with the Ypresian marine stage (Beck, 2012), the top of which is 47.8 Ma ± 0.2 Myr = 47.6 Ma (Gradstein et al., 2012), which we use as the paleontological minimum constraint for Marsupialia.
  node maximum age
131.3 Ma
Numerous metatherian remains are known from the Cretaceous of both North America (Kokopellia; Cifelli, 1993, 1998) and Mongolia (Asiatherium; Szalay and Trofimov, 1996), with the Early Cretaceous Sinodelphys szalayi being the oldest undisputed metatherian (Luo et al., 2003). Hence, we place the soft maximum constraint for Marsupialia at the Liaoning beds that produced Sinodelphys, correlating to the Barremian (Zhou et al., 2003) with a lower bound of 130.8 Ma ± 0.5 Myr = 131.3 Ma.
 primary fossil used to date this node 
QM F52748
Djarthia murgonensis, Godthelp et al. 1999
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: Murgon
     Geological age: Eocene, Paleogene, Cenozoic

More information in Fossilworks   PaleoBioDB

  phylogenetic justification
The oldest marsupials from Australia include taxa from the early Eocene locality of Murgon. The Murgon taxon Djarthia possesses a continuous lower ankle joint, a synapomorphy shared with the marsupial clade Australidelphia (Beck, 2012). The status of Djarthia as a crown marsupial is stronger than that for Khasia (Beck et al., 2008; Beck, 2012), and thus serves as a more definitive record of the latest point by which crown marsupials evolved.
  phylogenetic reference(s)
Beck, R.M. 2012. An 'ameridelphian' marsupial from the early Eocene of Australia supports a complex model of Southern Hemisphere marsupial biogeography. Naturwissenschaften, 99:715-729.