comment on this calibration


 node name
Amblypygi     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations
Wolfe et al. 2016
  node minimum age
313.7 Ma
The genus Graeophonus was originally described from the Sydney Basin, Cape Breton Carboniferous Coal Measures, Nova Scotia, Canada,which corresponds to Westphalian in age (Dunlop et al., 2007; Gileset al., 2002; Scudder, 1890a). Further studies are needed on the Canadian material, so the minimum age was taken from the oldest European specimen (which is roughly the same age as the Cape Breton specimen)from the British Middle Coal Measures (Coseley, Stafffordshire), which is Westphalian B (or Duckmantian) at the youngest (Waters et al.,1994; Waters and Davies, 2006). U-Pb dating of zircons constrains the upper boundary of the Duckmantian to 313.78 Ma ± 0.08 Myr (Pointon et al., 2012), so a minimum age for G. anglicus is 313.70 Ma.
  node maximum age
514 Ma
A soft maximum constraint comes from the oldest chelicerate W. barbarahardyae from the Emu Bay Shale on Kangaroo Island, SouthAustralia, which has been correlated based on trilobite biostratigraphy to the upper part of the P. janeae Zone in mainland South Australia (Jell in Bengtson et al., 1990; Fig. 2 in Jago et al., 2012). As this is equivalent to the Canglangpuan Stage in South China and the late Botoman inSiberia (Gehling et al., 2011, Fig. 9), the Emu Bay Shale can be dated to Cambrian Series 2, Stage 4, providing a maximum age of ~514 Ma.
 primary fossil used to date this node 
NHMUK In. 31233
Graeophonus anglicus, Pocock, 1911
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: Cape Breton Carboniferous Coal Measures
     Geological age: Carboniferous, Paleozoic

More information in Fossilworks   PaleoBioDB

  phylogenetic justification
G. anglicus was redescribed by Dunlop et al. (2007) as a member of the Amblypygi crown group. This was based on several morphological character comparisons to living members, such as the pedipalp femur with dorsal spination similar to Paracharon (the monotypic extant species of the family Paracharontidae). G. anglicus, unlike Paracharon, has a pear-shaped ocular tubercle, suggesting it was not blind. G. anglicus is inferred to be on the stem lineage of Paracharontidae, and thus, crown group Amblypygi (Dunlop et al., 2007).
  phylogenetic reference(s)
Dunlop, J.A., Zhou, G.R.S., Braddy, S.J., 2007. The affinities of the Carboniferous whip spider Graeophonus anglicus Pocock, 1911 (Arachnida: Amblypygi). Earth Environ. Sci. Trans. R. Soc. Edinb. 98, 165–178.
 tree image (click image for full size) 
tree image
Figure 6 from Wolfe et al. (2016).