This large, deepwater shark is an example of significantly more primitive species found only as fossils. It has a broad, flat head, large green eyes and a small, single dorsal fin far along its back. Average length is 15 to 16 feet long, and it is grey to olive to brown in colour. It feeds nocturnally and ambushes its prey, but because it lives at depths, little is known about it and it is not considered a threat to humans unless it is provoked.