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Vertebrata-Craniata

Lineage (NCBI): root » Eukaryota » Opisthokonta » Metazoa » Coelomata
 node name
Vertebrata-Craniata     Look for this name in NCBI   Wikipedia   Animal Diversity Web
 
  recommended citations
http://palaeo-electronica.org/content/fc-1 Benton et al. 2015
 
  node minimum age
457.5 Ma
The holotype of Arandaspis prionotolepis was recovered from the Stairway Sandstone Formation of Mt Watt, Amadeus Basin, Northern Territory, Australia (Ritchie and Gilbert-Tomlinson, 1977). The age of the formation is constrained by the occurrence of the conodont Lenodus sp. cf. L. variabilis in the middle part of the Stairway Sandstone which Davies et al. (2011) interpret as evidence for an early Darriwilian age. This is based on the assumption that Lenodus sp. cf. L. variabilis falls within the taxonomic range of Lenodus variabilis and L. antivariabilis which have a stratigraphic range limited to the upper Baltoniodus norrlandicus Zone to the Eoplacognathus variabilis and Yangtzeplacognathus crassus zones (Löfgren and Zhang, 2003). The most secure geochronological date appropriate to constrain the minimum age of the holotype of Arandaspis prionotolepis is the Darriwillian-Sandbian boundary, which is dated at 458.4 Ma ± 0.9 Myr, thus 457.5 Ma.
 
  node maximum age
636.1 Ma
The soft maximum constraint encompasses the possibility that putative Cambrian vertebrates, such as Haikouichthys, Myllokunmingia (Shu et al., 1999), Zhongjianichthys (Shu, 2003), are stem-cyclostomes. Thus, our soft maximum is based on the maximum age interpretation of the Lantian Biota (Yuan et al., 2011). This, together with the Doushantuo Biota (Yuan et al., 2002), provide a series of 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 credibly be interpreted as even a total group eumetazoan and on this basis we define out 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 
 
CPC 13202
Arandaspis prionotolepis , Ritchie and Gilbert-Tomlinson, 1977
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: Mt Watt, Amadeus Basin, Northern Territory
     Stratum: Stairway Sandstone Formation
     Geological age: Ordovician, Paleozoic


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  phylogenetic justification
Arandaspis prionotolepis is unequivocally a member of the gnathostome total group, based on a number of phylogenetic analyses (Janvier, 1996a, 1996b; Donoghue et al., 2000; Donoghue and Smith, 2001). It exhibits a number of unequivocal characters exclusive to total-group gnathostomes, most obviously including a mineralized dermal skeleton.
 
  phylogenetic reference(s)
Janvier, P. 1996. The dawn of the vertebrates: characters versus common ascent in the rise of current vertebrate phylogenies. Palaeontology, 39:259-287.
 
 tree image (click image for full size) 
tree image
Figure 2 from Benton et al. (2014).
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