comment on this calibration


 node name
Peracarida     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations
Wolfe et al. 2016
  node minimum age
306.9 Ma
Specimens are derived from the Francis Creek Shale Member of the Carbondale Formation, Mazon Creek, Illinois, of Westphalian D age (Baird et al., 1985; Shabica and Hay, 1997). The Westphalian D is equivalent to the latest Moscovian stage of the Pennsylvanian (Richards,2013). As the upper boundary of the Moscovian is 307.0 Ma± 0.1 Myr, this provides a minimum age of 306.9 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 
FMNH PE 16527
Hesslerella shermani, Schram, 1970
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: Mazon Creek
     Stratum: Francis Creek Shale Member of the Carbondale Forma
     Geological age: Carboniferous, Paleozoic

More information in Fossilworks   PaleoBioDB

  phylogenetic justification
H. shermani was included in a morphological cladistic analysis by Wilson (2012). It occurred at the base of Phreatoicidea (Wilson, 2012), a position within the crown group of Isopoda and thus, crown Peracarida. Note that the assignment of our calibration fossil to crown Isopoda means that exclusion of Mysida from Peracarida (Jenner et al., 2009; Meland and Willassen, 2007; Spears et al., 2005) will not change the date assessed for Peracarida.
  phylogenetic reference(s)
The linked fossil has no phylogentic references.
 tree image (click image for full size) 
tree image
Figure 13 from Wolfe et al. (2016).