JAIME CHIRINOS / SCIENCE PHOTO LIBRARY JAIME CHIRINOS / SCIENCE PHOTO LIBRARY
Helicoprion bessonovi prehistoric shark, artwork. This species of shark existed from the late Carboniferous period (280 million years ago), until the early Triassic period (225 million years ago). This shark is known only from fossilised sets of teeth that form circular coils. It is thought that the tooth-whorl formed on the lower jaw and developed as newer teeth grew and pushed the older teeth to form the coil. It is not known how the shark used the coil to feed.
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