comment on this calibration


 node name
Zygentoma     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations
Wolfe et al. 2016
  node minimum age
98.17 Ma
This fossil is sourced from amber mines in the Hukawng Valley of Kachin State, northern Myanmar (formerly Burma). The depositional age of Burmese amber was estimated from U-Pb dating of zircons from the volcaniclastic matrix surrounding the amber (Shi et al.,2012). Shi et al. (2012) argue the amber is not older than its associated sediments, as burial and preservation would have to be rapid for survival of organic material, so the amber was probably formed at, but not earlier than the U-Pb date: at 98.79 Ma±0.62 Myr. Therefore, a minimum age for any fossil from Burmese amber deposits is 98.17 Ma.
  node maximum age
521 Ma
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 
Poinar B-TH-1
Burmalepisma cretacicum, Mendes and Poinar, 2008
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: Hukawng Valley
     Geological age: Cretaceous, Mesozoic

More information in Fossilworks   PaleoBioDB

  phylogenetic justification
Although it has not been included in a phylogenetic analysis, B. cretacicum bears several morphological similarities to the extant family Lepismatidae. These include the presence of compound eyes, absence of ocelli, coxal, femur, and tarsalmorphology, absence of a pronotal setal collar, and presence of only smooth macrochaetae (Mendes and Poinar, 2008). A phylogenetic position either on the stem or within the crown of Lepismatidae is within the crown group of Zygentoma.
  phylogenetic reference(s)
Mendes L.F., Poinar G.O. 2008. A new fossil silverfish (Zygentoma: Insecta) in Mesozoic Burmese amber. Eur. J. Soil Biol. 44, 491–494.
 tree image (click image for full size) 
tree image
Figure 17 from Wolfe et al. (2016).