comment on this calibration


 node name
Mollusca     Look for this name in NCBI   Wikipedia   Animal Diversity Web
  recommended citations Benton et al. 2015
  node minimum age
532 Ma
Aldanella yanjiahensis has been found to be associated with Watsonella crosbyi and Oelandiella korobkovi in the Dahai member in the middle Meishucunian of China (Steiner et al., 2007). It has been suggested that this assemblage serves as a biozone. Chemostratigraphic correlations place this unit in the Nemakit Daldynian within the interval 534-532 Ma (Maloof et al., 2010).
  node maximum age
549 Ma
We established a soft maximum constraint on the approximate maximum age of the Nama Group (549 Ma; Narbonne et al., 2012; Grotzinger et al., 1995) which preserves an open marine community including the earliest animal skeletal remains, viz. Cloudina, Namacalathus and Namapoika (Wood, 2011), but does not preserve the skeletal remains of molluscs, nor does any of the very widespread strata that preserve Cloudina. Since a biomineralized skeleton with distinctly molluscan microstructure (e.g., crossed lamellar tissue is a synapomorphy of crown molluscs), the absence of such remains in a suite of deposits ecologically compatible with molluscs and capable of preserving their remains, suggests their absence in the prior interval of Earth history.
 primary fossil used to date this node 
TU YXII02-02
Aldanella yanjiahensis, Chen 1984
Location relative to the calibrated node: Crown

[show fossil details]
     Locality: Dahai member in the middle Meishucunian
     Geological age: Cambrian, Paleozoic

More information in Fossilworks   PaleoBioDB

  phylogenetic justification
Aldanella is a dextrally coiled mollusc assigned to the Pelagiellida. The distinct assymetries and the preservation of muscle scars (Runnegar, 1981) suggest that it is a partially coiled stem-group gastropod.
  phylogenetic reference(s)
Runnegar, B. 1981. Muscle scars, shell form and torsion in Cambrian and Ordovician univalved molluscs. Lethaia 14:311-322.
 tree image (click image for full size) 
tree image
Figure 1 from Benton et al. (2014).