comment on this calibration


 node name
Multicrustacea     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations
Wolfe et al. 2016
  node minimum age
487 Ma
A. inflata is found in the Elk Mound Group (holotype) and in the Lodi Member of the St. Lawrence Formation, both in Wisconsin (Collette and Hagadorn, 2010a). Although the Elk Mound Group is the older of these,no biostratigraphically useful fossils co-occur with A. inflata, limiting the ability to determine the formation to which they belong (Collette and Hagadorn, 2010a). The St. Lawrence Formation is younger, containing Saukia Zone trilobites, which mark it as late Sunwaptan within the Furongian (Collette and Hagadorn, 2010a; Raasch, 1951). The Sunwaptan is the second latest stage of the Furongian, postdated by the Skullrockian (which extends into the Early Ordovician; Peng et al.,2012a). The Sunwaptan-Skullrockian boundary is determined by the appearance of conodonts in the Hirsutodontus hirsutus Subzone of the Cordylodus proavus Zone (Peng et al., 2012a). Based on the correlationd iagram of Peng et al. (2012a), the Sunwaptan-Skullrockian boundary is approximately 487 Ma, providing a minimum age estimate.
  node maximum age
636.1 Ma
A soft maximum constraint is based on that used by Benton et al.(2015), the maximum age interpretation of the Lantian Biota (Yuan et al., 2011). This, together with the Doushantuo Biota (Yuan et al.,2002), provides a series of Konservat-Lagerstätten preserving the biota in Orsten- and Burgess Shale-like modes of fossilization. None of these Lagerstätten, least of all the Lantian, preserves anything that could possibly be interpreted as even a total group eumetazoan and on this basis we define our soft maximum constraint at 635.5 Ma ±0.6 Myr (Condon et al., 2005) and, thus, 636.1 Ma.
 primary fossil used to date this node 
UWGM 745
Arenosicaris inflata, Collette and Hagadorn, 2010a
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: Lodi Member
     Stratum: St. Lawrence Formation
     Geological age: Cambrian, Paleozoic

  phylogenetic justification
A. inflata was identified within the Archaeostraca, the likely fossil sister group to extant Leptostraca (together comprising ‘Phyllocarida’) and included in the morphological cladistic analysis of Collette and Hagadorn (2010b). In that analysis, the exceptionally preserved fossils Nahecaris stuertzi Jaeckel, 1921 and Cinerocaris magnifica Briggs et al.,2004 were also included within Archaeostraca (Collette and Hagadorn,2010b). A separate extensive combined molecular and morphological analysis placed C. magnifica within crown Malacostraca (as is traditionally assumed for members of Archaeostraca), while N. stuertzi was equivocally stem Leptostraca or stem Malacostraca (Oakley et al.,2013), suggesting non-monophyly of Archaeostraca. C. magnifica was also crown Malacostraca in another morphological analysis that omitted N. stuertzi (Legg et al., 2013). A. inflata is within the same archaeostracan clade as N. stuertzi (Pephricaridina + Rhinocaridina) while C. magnificais in a separate archaeostracan group (Echinocaridina; Collette and Hagadorn, 2010b). Given the uncertainty of crown affinities and potential monophyly of Archaeostraca, we conservatively assign A. inflata to crown-group Multicrustacea, but not Malacostraca.
  phylogenetic reference(s)
Legg, D.A., Sutton, M.D., Edgecombe, G.D. 2013. Arthropod fossil data increase congruence of morphological and molecular phylogenies. Nature Communications 4, 2485.
Oakley, T.H.,Wolfe, J.M., Lindgren, A.R., and Zaharoff, A.K. 2013. Phylotranscriptomics to bring the understudied into the Fold: Monophyletic Ostracoda, fossil placement, and Pancrustacean phylogeny. Mol. Biol. Evol. 30, 215–233.
Collette, J.H., Hagadorn, J.W., 2010b. Early evolution of phyllocarid arthropods: phylogeny and systematics of Cambrian-Devonian archaeostracans. J. Paleontol. 84, 795–820.
 tree image (click image for full size) 
tree image
Figure 12 from Wolfe et al. (2016).