comment on this calibration


 node name
Chondrichthyes     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations Benton et al. 2015
  node minimum age
333.56 Ma
umbie Quarry and the Glencartholm Fish Bed are lateral equivalents within the Glencartholm Volcanic Beds of Scotland (Finarelli and Coates, 2012, 2014). Foraminfera indicate that the Glencartholm Volcanic Beds span the boundary between the Holkerian and Absian regional stages (Cater et al., 1989; Purnell and Cossey, 2004). This is roughly equivalent to the boundary between the Livian and Warnantian in the Western European subdivision of the Carboniferous (Davydov et al., 2012, p. 606), and places the Glencartholm Volcanic Beds within the mid-Visean of the global timescale. The top of the Absian lies within the Gnathodus bilineatus Conodont Zone (Poty et al., 2014). Younger ash beds provide a minimum age for the top of this zone of 333.95 Ma ± 0.39 Myr (Davydov et al., 2012). From this, we derive a minimum age for crown Chondrichthyes of 333.56 Ma.
  node maximum age
422.4 Ma
Tillywhandland Quarry in Scotland (Trewin and Davidson, 1995), Wayne Herbert Quarry in England (Miles, 1973), and the Man on the Hill (‘MOTH’) site in Canada (Gagnier and Wilson, 1996) yield a diverse range of cladistically justified members of the chondrichthyan stem group (Brazeau, 2009; Davis et al., 2012; Zhu et al., 2013; Dupret et al., 2014; Brazeau and Friedman, 2014), but no crown chondrichthyans. These Lochkovian deposits predate the oldest body-fossil remains attributed to Chondrichthyes in an apomorphy-based sense (the Emsian Doliodus and Pucapampella; Maisey and Anderson, 2001; Miller et al., 2003). The base of the Lochkovian is dated as 419.2 Ma ± 3.2 Myr, from which we derive our soft maximum age for crown Chondrichthyes of 422.4 Ma.
 primary fossil used to date this node 
NMS 1998.35.1
Chondrenchelys problematicus, NO REFERENCE
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: Mumbie Quarry, Glencartholm, Scotland
     Stratum: Glencartholm Volcanic Group, Upper Border Group of
     Geological age: Carboniferous, Paleozoic

  phylogenetic justification
Chondrenchelys is recognized as a member of Holocephali based on the presence of numerous synapomorphies of that clade, including: complete fusion of the palatoquadrate with the braincase, absence of a precerebral fontanelle, an elongate ethmoid region, insertion of jaw adductor muscles anterior to the orbit, absence of persistent cranial fissures, a fused mandibular symphysis, a terminal posterior articulation of the mandible, a reduced number of tooth families, and tooth crowns reinforced with hypermineralized tissue (reviewed in Finarelli and Coates, 2014). Placement of Chondrenchelys within Holocephali is also supported by the formal cladistic analysis presented by Lund and Grogan (1997) and the manual solution given by Stahl (1999).
  phylogenetic reference(s)
Lund, R. and Grogan, E.D. 1997. Relationships of the Chimaeriformes and the basal radiation of the Chondrichthyes. Reviews in Fish Biology and Fisheries, 7:65-123.
Finarelli, J.A. and Coates, M.I. 2012. First tooth-set outside the jaws in a vertebrate. Proceedings of the Royal Society, Series B, 279:775-779.
Stahl, B.J. 1999. Chondrichthyes III: Holocephali, p. 1-164. In Schultze, H.-P. (ed.), Handbook of Paleoichthyology, Volume 4. Verlag Dr. Friedrich Pfeil, Munich.
 tree image (click image for full size) 
tree image
Figure 3 from Benton et al. (2014).