Enigmatic Chancelloria Fossils from Utah

Description: Presented is a playful and elegant association of three Chancelloria pentacta. I fell in love with this fossil when I saw it. The sponges are a bit ethereal, almost floating on the plate. One of the characteristics of this most aesthetic fossil is the star-shaped scierites.

Chancelloria is a genus of early animal known from the Middle Cambrian Burgess Shale and Wheeler Shale and elsewhere. It was first described in 1920 by Charles Doolittle Walcott, who regarded them as one of the most primitive groups of sponges. This appears unlikely, and it is currently placed in the enigmatic group Coeloscleritophora.

Classifying the chancelloriids is difficult. Some paleontologists classify them as sponges, an idea which chancelloriids' sessile lifestyle and simple structure make plausible. Other proposals suggest that they were more advanced, or at least originated from more advanced ancestors; for example chancelloriids' skins appear to be much more complex than those of any sponge. It has been suggested that chancelloriids were related to the "chain mail" armored slug-like halkieriids, which are important in analyses of the Cambrian explosion. The chancelloriids had bag-like bodies with an orifice at the top, and show no evidence of internal organs.