The scientists did not see much wear, tear and breakage, so they suspect Helicoprion primarily sliced into squid or other ancient relatively soft and somewhat chewy sea life. Aside from squid and their early relatives, armored and cartilaginous fish lived in Helicoprion’s ecosystem, along with brachiopods, bivalves and snails. "Cartilaginous” refers to fish made up of cartilage, a firm yet flexible connective tissue.
While Helicoprion looked and acted like a shark, the researchers determined that it’s at the base of the family tree that today includes chimaera (aka "ghost sharks”) and ratfish. Ghost sharks are not technically sharks, but they look and act a lot like them.
Tapanila explained that cartilaginous fish are divided into two main categories: sharks and rays on one side, ratfish and chimaera on the other. They are all marine predators.
No living land or sea animal directly resembles Helicoprion -- especially it’s buzz-saw tooth whorl.
"It was really an improbable animal, and maybe one of the best examples of a successful ‘Hopeful Monster,’” Tapanila said, explaining that this refers to evolutionary processes that can result in very unusual body types, with most doomed to failure.
While Helicoprion eventually went extinct, it used to have a nearly global distribution and existed over a period of 10 million years or more, proving that even some eccentric body designs can be successful if they meet the particular needs influenced by the animal’s environment, food sources and more.
John Long, a professor of paleontology at Flinders University, told Discovery News that he fully supports the new findings about Helicoprion and its kin.
"This study ends a century old mystery about this iconic fossil (species) and highlights the unexpected diverse body form that holocephalans occupied,” Long said.
Tapanila and his team would love to find a fossilized prey animal in the mouth of such a prehistoric shark-like animal, to better determine which exact species they were hunting and eating. Given that they lived even before the dinosaurs, Tapanila isn’t "holding his breath” for such a rare find.