Hazelia, A Desmosponge Fossil from Chengjiang China

This is a specimen of a member of the Desmospongia, the most diverse of modern-day sponges. Greater than 90% of the extant 5,000 known species of sponges are desmosponges. Such a representation in the fossil record is not maintained where less than half the known genera are of this type, a consequence of the fact that the skeletons do not fossilize readily. Desmosponge skeletons are composed of spongin fibers and/or siliceous spicules. Sponges are known from the late Precambrian, with few localities contributing to the fossil record over time. The Chengjiang Biota is one such fossil lagerstatte, with sponges as the second-most represented metazoans after the arthropods. The Chengjiang sponges were suspension feeders who are thought to have engaged in tiering much like the later crinoids. By feeding from slightly different heights of the water column, various members were able to live peaceably within the same general location feeding upon different sized nutrients.