Middle Cambrian

Burgess Shale, Stephens Formation

Field, British Columbia, Canada

Big 61mm Chancellorid on 141mm x 93mm slab (78)

Problematica, Burgess Shale.

Allonnia has been classified in the Family Chancelloriidae but the position of the family is uncertain.  Some paleontologists want to place it among the sponges but others have proposed that it has a separate ancestry.  The group died out by the end of the Cambrian.