comment on this calibration


 node name
Xenarthra     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations Benton et al. 2015
  node minimum age
47.6 Ma
Until recently, Itaboraí was regarded as upper Paleocene in age, but Woodburne et al. (2014) suggest that it is early Eocene, which would lead to a paleontological minimum estimate for crown Xenarthra corresponding to the the top of the Ypresian marine stage, 47.8 Ma ± 0.2 Myr = 47.6 Ma (Gradstein et al., 2012).
  node maximum age
164.6 Ma
The soft maximum date is based on the divergence of Eutheria from other mammals in the late Jurassic, represented by Juramaia (Luo et al., 2011). This taxon is represented in the Daxigou site of the Tiaojishan Formation, Liaoning Province, Northeastern China, and has been constrained by radiometric dates to derive from deposits of just over 160 Ma in age (Luo et al., 2011). The equivalent marine stage is the Oxfordian (Gradstein et al., 2012), with a lower boundary of 163.5 Ma ± 1.1 Myr, and thus 164.6 Ma is a soft maximum.
 primary fossil used to date this node 
MCN PV 1774
Riostegotherium yanei , Scillato-Yané 1976
Location relative to the calibrated node: Crown

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

  phylogenetic justification
Riostegotherium belongs to crown Xenarthra based on the diagnostically cingulate osteoderms (e.g., the type mentioned above). Other skeletal elements (e.g., astragali) with a close resemblance to cingulates are also known from Itaboraí (Bergqvist et al., 2004).
  phylogenetic reference(s)
Bergqvist, L. P., Abrantes, E. A. L. & Avilla, L. D. 2004. The Xenarthra (Mammalia) of Sao Jose de Itaborai Basin (upper Paleocene, Itaboraian), Rio de Janeiro, Brazil. Geodiversitas 26: 323-337.
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