comment on this calibration


 node name
Mammalia     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations Benton et al. 2015
  node minimum age
164.9 Ma
At present it cannot be said which of the Bathonian eutriconodonts and dryolestoids (Boneham and Wyatt, 1993) and australosphenidans (Flynn et al., 1999) is oldest, but we select Ambondro as most likely. It comes from the upper part of the Isalo “Group” (middle Jurassic, Bathonian) of Madagascar (Flynn et al., 1999), dated as generally Bathonian, so we select the top of the Bathonian as the hard minimum calibration date, 166.1 Ma ± 1.2 Myr = 164.9 Ma (Gradstein, 2012).
  node maximum age
201.5 Ma
The closest relatives of crown mammals are Hadrocodium and Docodonta (Luo et al., 2002; Meng et al., 2011). Hadrocodium was originally reported to be early Jurassic of Yunnan Province, China (Sinemurian; Luo et al., 2001), and the oldest docodonts are from the Bathonian of Europe, with a possible earlier form from the Kota Formation of India. Further outgroups, Morganucodontidae, Sinoconodon, and Adelobasileus, are known from the late Triassic and early Jurassic. Deposits of Late Triassic and Early Jurassic age have yielded fossil mammaliaforms, but nothing assignable to the Australosphenida or Theriimorpha. We therefore suggest the Triassic-Jurassic boundary at 201.3 Ma ± 0.2 Myr = 201.5 Ma as a soft maximum constraint.
 primary fossil used to date this node 
UA 10602
Ambondro mahabo, Flynn et al., 1999
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: Ambondromahabo
     Stratum: Isalo “Group"
     Geological age: Jurassic, Mesozoic

More information in Fossilworks   PaleoBioDB

  phylogenetic justification
Ambondro mahabo from Madagascar (Flynn et al., 1999) is placed within the monotreme clade Australosphenida, according to the most widely accepted cladistic analysis of crown Mammalia (Luo et al., 2007; Meng et al., 2011).
  phylogenetic reference(s)
Flynn, J.J., Parrish, J.M., Rakotosamimanana, B., Simpson, W.F., and Wyss, A.R. 1999. A Middle Jurassic mammal from Madagascar. Nature, 401:57-60.
Luo, Z-X., Chen, P., Li, G., and Chen, M. 2007. A new eutriconodont mammal and evolutionary development in early mammals. Nature, 446:288-293.
Meng, J., Wang, Y., and Li., C. 2011. Transitional mammalian middle ear from a new Cretaceous Jehol eutriconodont. Nature 472, 81-185.
 tree image (click image for full size) 
tree image