Life during the Middle Cambrian (approx. 500 million years ago) Based on fossils from the Burgess Shale – Walcott quarry. On the seafloor beneath the underwater cliffs (Cathedral escarpment), there are various types of sponges and some algae growing. In the foreground is a lobopodian worm, Hallucegenia sparsi, feeding on a sponge. An arthropod, Sidneyia inexpectans, crawls on the seafloor, while an Anomalocaris canadensis swims menacingly nearby.