comment on this calibration


 node name
Scorpiones     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations
Wolfe et al. 2016
  node minimum age
112.6 Ma
This fossil was recovered from the Nova Olinda Member of the Crato Formation in the Araripe Basin, northeastern Brazil. This unit is generally agreed to be around the Aptian/Albian border (Martill et al., 2007). Batten (2007) suggests that if assemblages in the upper layers are consistent across the lower layers, a late Aptian date should be considered.The Crato formation has been dated using palynomorphs (Pons et al.,1990) to the Aptian, though an accurate date for the Nova Olinda Memberis not available. The upper boundary of the Aptian, at 113.0 Ma ±0.4 Myr, gives a minimum date of 112.6 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 
MN 7601-1
Protoischnurus axelrodurum, Carvalho and Lourenço, 2001
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: Araripe Basin
     Stratum: Nova Olinda Member of the Crato Formation
     Geological age: Cretaceous, Mesozoic

  phylogenetic justification
Menon (2007) placed P. axelrodurum in the extant family Hemiscorpiidae, based on, among other characters, an inverse Y-shaped sulcus on the cephalic shield, the placement of Esttrichobothria on the pedipalp chela, and the placement of carinae V2 and V3 in the pedipalp chela, all of which are diagnostic of the hemiscorpidid subfamily Hormurinae (Soleglad et al., 2005). Hemiscorpiidae is classified within Iurida (Sharma et al., 2015), and is thus crown group Scorpiones.
  phylogenetic reference(s)
Menon, F., 2007. Higher systematics of scorpions from the Crato Formation, Lower Cretaceous of Brazil. Palaeontology 50, 185–195.
 tree image (click image for full size) 
tree image
Figure 4 from Wolfe et al. (2016).