Diagonella Sponge Fossils from Pyritized Triarthrus Trilobite Site

Fossil Description: With only about a half dozen localities known, trilobites with soft tissue preservation are rare. A well-known site in the United States is Beecher’s Trilobite bed where examples of Triarthrus, Cryptolithus, and Cornuproetus are known. In 2005 a new location in Lewis County was discovered which will take its place in this select group as a site containing Triarthrus eatoni with preserved appendages. This is another, more uncommon member of the same location: a sponge known as Diagonella.Diagonella belongs to the family Protospongiidae, which was a group of early and primitive sponges of the Class Hexactinellida. Diagonella was attached to the sea floor by long spines at the base of the sponge. These spines are rarely preserved. The six-rayed spicules were not fused into a net, so were relatively fragile as a result. These sponges are very rare in the Burgess Shale of British Columbia,But are also found in slightly younger deposits in Urah. Sponges are relatively uncommon in the fossil record owing to their delicacy. These are from younger Ordovician deposits, and are the only pyritized examples I have come across.