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TF0905 - Irregular Echinoid
Stratigraphic Range
Upper Cretaceous
Taxonomy
Phylum: Echinodermata
Class: Echinodea
Subclass: Irregularia
Order: Holasteroida
Class: Echinodea
Subclass: Irregularia
Order: Holasteroida
Distinctive Features
Bilateral symmetry
Mouth and anus out of line
Five radial ambulacra
Interambulacra with plates
Mouth and anus out of line
Five radial ambulacra
Interambulacra with plates
Preservation
Sediment infill
Mineral replacement of shell
Mineral replacement of shell
Advanced notes
Set 1: Anus and mouth appear to have been drilled to emphasise their positions.
Set 2: Fracturing of shell around the anus which obscures it. This would be a weak part of the shell which diagenetic processes have crushed.
Set 2: Fracturing of shell around the anus which obscures it. This would be a weak part of the shell which diagenetic processes have crushed.