comment on this calibration


 node name
Odonata     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations
Wolfe et al. 2016
  node minimum age
228 Ma
T. mendozensis was discovered in dark grey siltstone of the Potrerillos Formation, at Quebrada del Durazno, Mendoza Province, Argentina (Martins-Neto et al., 2008). The insect-bearing beds are from the upper part of the Potrerillos Formation. U-Pb SHRIMP dates have been measured for zircons from tuff layers in the middle section of the Potrerillos Formation. The uppermost tuff layer estimated an age of 230.3 Ma ± 2.3 Myr (Spalletti et al., 2009), corresponding to the Carnian, late Triassic. Thus a minimum age of T. mendozensis is 228.0 Ma.
  node maximum age
521 Ma
Because the monophyly of Palaeoptera is under debate (Simon et al., 2009, 2012), we assign a soft maximum age that allows its constituent extant orders to be older than the Rhynie Chert. A soft maximum age is obtained from the oldest mandibulate, Y. dianensis, which was recovered from the Yu'anshan Formation at Xiaotan section, Yongshan, Yunnan Province, attributed to the Eoredlichia–Wutingaspis Biozone (Zhang et al., 2007). Chinese Cambrian stratigraphy has been revised substantially and the Eoredlichia –Wutingaspis Biozone is no longer recognized (Peng, 2003, 2009). However, Eoredlichia is known to co-occur with Hupeidiscus, which is diagnostic of the Hupeidiscus-Sinodiscus Biozone, which is formally recognized as the second biozone of the Nangaoan Stage of the Qiandongian Series of the Cambrian of China (Peng and Babcock,2008). The Nangaoan is the proposed third stage of the Cambrian System for the International Geologic Timescale (Peng et al., 2012a).Thus, a soft maximum constraint can be established on the age of the lower boundary of the Nangaoan, which has been dated to 521 Ma (Peng et al., 2012a; Peng and Babcock, 2008).
 primary fossil used to date this node 
MACN 18040
Triassothemis mendozensis, Carpenter, 1960
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: Quebrada del Durazno
     Stratum: Potrerillos Formation
     Geological age: Triassic, Mesozoic

  phylogenetic justification
T. mendozensis is the oldest known member of the fossil family Triassolestidae (Nel et al., 2002; Nicholson et al., 2015). A family-level supertree, incorporating molecular and morphological input trees, found Triassolestidae within crown group Epiprocta (Davis et al. 2011, largest tree in their Fig. 1). This fossil is therefore also a member of crown group Odonata. Of all the fossil families included in the supertree analysis and placed within crown Odonata (Davis et al., 2011), Triassolestidae (represented by T. mendozensis) has the oldest member. Furthermore, this family (and its approximate date) was used to calibrate Odonata in multiple recent divergence time analyses (Rota-Stabelli et al., 2013a; Thomas et al., 2013).
  phylogenetic reference(s)
Davis, R.B., Nicholson, D.B., Saunders, E.L., Mayhew, P.J., 2011. Fossil gaps inferred from phylogenies alter the apparent nature of diversification in dragonflies and their relatives. BMC Evol. Biol. 11, 252.
 tree image (click image for full size) 
tree image
Figure 17 from Wolfe et al. (2016).