Primitive Cambrian Chancelloria pentacta (a Putative Sponge) with Carpoids

While originally described as a sponge, some scientists have proposed a new Class Coeloscleritophora for Chancelloria. This Class includes Wiwaxiidae and other Cambrian sclerite-bearing animals.

This is a very unusual specimen in that it has two carpoids attached to it. The Chacelloria is small for the species, but is still a very interesting piece. The Chancelloria from Utah were identified as Chancelloria pentacta, but are essentially identical to Chancelloria eros, like those found in the Burgess Shale.

Rigby, J.K. 1978 Porifera of the Middle Cambrian Wheeler Shale, from the Wheeler Amphitheater, House Range, in western Utah. Journal of Paleontology 52, 1325-1345.

About sponges: When people think of fossils, they normally think first of dinosaurs, of trilobites, of ammonites - but usually not sponges, yet they should. The humble sponge during modern times is represented by some 9000 species spread across the globe and occupying essentially all aquatic environments. Despite their ubiquitous dispersion, they are of truly ancient origin. Indeed, sponges may well be the "Lucy" of all of the Kingdom Animalia, since they were likely to have been the first animals on Earth with cooperative cells. More accurately, based on phylogenetic data from sponges and other creatures of ancient origin, we can conjecture that sponges occupy the oldest and lowest branch on the animal family tree. Because the higher branches have introduced additional innovations that account for animals' rich diversity, the common ancestor of all animals likely resembled modern sponges much more closely than any other living animals. Sponges' ability to grow different cell types performing different and cooperative functions was an innovation that underlies virtually all subsequent advances in the animal kingdom. While their cell signally pathways are simplistic compared to most modern animals, it obviously was robust enough for them to survive the numerous mass extinctions on Earth since the origin of sponges in Precambrian time.

Also See: Utah Cambrian Explosion Fossils