Watsonella instance of taxon
Watsonella is a genus of 'mollusc' known from early (Terreneuvian) Cambrian strata.
The genus is closely related to Anabarella, with which it bears many morphological similarities, including a laminar internal shell microstructure said to connect it with the early bivalves Fordilla and Pojetaia.Biostratigraphic significance
Watsonella has been proposed as an index fossil of the Cambrian, defining a W. crosbyi zone.  Notwithstanding the weakness of a first appearance datum as a definition for the base of a period, the species has been proposed as a marker for the base of the presently unratified second stage of the Terreneuvian (i.e. Cambrian Stage 2).   However, the species has now been found late in the FOrtunian, drawing back its first occurrence. But that said its occurrence in Australia seems to begin rather near the base of Stage 2.
type of example of manifestation of representation of