What it is
A living fish with no jaws and no bones. Its skeleton is cartilage, like a shark's. An adult sea lamprey fastens onto another fish with a round sucking mouth ringed with teeth, and feeds on it. A single sea lamprey can kill up to 40 pounds of fish.
An old family
Lampreys were around long before the dinosaurs. In 2006, scientists described a lamprey from South Africa about 360 million years old. It already had the round sucking mouth, and it looks a lot like the ones alive today.
An invader
Sea lampreys come from the Atlantic Ocean. Shipping canals let them into the Great Lakes, where they nearly wiped out the lake trout. Since 1954, the United States and Canada have fought them together, and they have cut their numbers by about 90 percent.
Why it matters
In 2016 a team said the Tully monster was a jawless fish, a cousin of the lamprey. They read a pale stripe along its body as the rod every backbone is built around. The next year another team took that apart. Wrong place, they said, and wrong shape.