Enigmatic Allonia Burgess Shale Chancellorid

Description: This is an unusual and enigmatic animal known as a chancellorid of the genus Allonia. The order is named after Chancelloria, another genus of this strange group of animals. Their precise assignment as to phylum is still much in dispute. Chancelloria was believed by C.D. Walcott to be a heteractinellid sponge, a position acceded to by most researchers until some 30 years ago when it was noted that the supposed spicules were actually sclerites. As such they must have been secreted from the inside, rather than being tissue-covered. These sclerites appear to have function like chain mail armor, affording protection to the animal. Like sponges, however, they are thought to have been filter feeders. Typically, only individual sclerites are preserved; a complete specimen such as this is a rare occurrence. Since the location has been declared a World Heritage site, only specimens from old collections such as this are available.