Jan. 8, 2013 at 2:47 PM ET
By Jennifer Viegas
Paleontologists have identified one of the world's oldest known "super predators," meaning carnivores that can feed on prey that's as large, or larger, than themselves.
The toothy beast, described in the latest issue of the Journal of Systematic Paleontology, was a marine crocodile that looked part shark and part sinister dolphin. Its scientific name is Tyrannoneustes lythrodectikos, or "Tyrant Swimmer."
"Tyrannoneustes lythrodectikosis the oldest known metriorhynchid macrophage — an animal that was adapted to feeding on large-bodied prey," lead author Mark Young of the University of Edinburgh's School of Biological Sciences told Discovery News.
He explained that the term "metriorhynchid" refers to a group of marine crocodiles that were superficially similar to living dolphins.
"They lacked bony armor, had flipper-like forelimbs and had a tail fluke," he said.
This animal evolved from related species "that were opportunistic predators of small, fast moving prey." These marine hunters had narrow snouts and multiple teeth, but the teeth weren't serrated like those of Tyrant Swimmer, which also could open its mouth very wide.
Young and his colleagues studied the remains of Tyrant Swimmer, found in the Oxford Clay Formation. This is a Jurassic marine sedimentary rock formation underlying much of southeast England. The remains have been in storage for some time at the Hunterian Museum in Glasgow.
The super predator made the rounds outside of what is now the U.K. too.
"Tyrannoneustes is known from shallow marine deposits across Europe (England, France and Poland)," Young, who also works at the University of Southhampton's National Oceanography Center, explained. "During the Middle Callovian 165 million years ago, much of Europe was covered by a shallow sea, creating a chain of large to small islands. Tyrannoneustes lived in this shallow sea, along with numerous other marine reptiles."
These reptiles included pliosaurs, plesiosaurs and ichthyosaurs. Giant pliosaurs were even larger than the Tyrant Swimmer, so they might have feasted on the formidable species. As its name suggests, however, Tyrant Swimmer would have been swift in the water, so it likely could have out-swam possible predators and used the swimming prowess to capture its own prey.
As of now, no stomach contents for the Tyrant Swimmer have been located, so what it precisely ate remains a mystery.
The Middle Jurassic gave rise to other huge predators in both the sea and on land. One of the most bloodthirsty dinosaurs of the time was Allosaurus, known for its massive toothy skull on a short neck. Some dinosaurs of this genus could grow up to 28 feet long.
As for ecosystems today, the presence of such big hunters usually indicates a healthy food chain, with many animals down the line for predators to prey upon. When keystone species begin to decline, usually the entire ecosystem is in trouble.
"It is great to see old collections (specimens collected in the 1800s) being re-examined, and it demonstrates the scientific value of museum collections," Lorna Steel, a curator in the Department of Paleontology at the Natural History Museum in London, told Discovery News.
In terms of what happened to Tyrant Swimmer, Young indicated it evolved into an even more stealthy group of marine predators with very large and numerous teeth and mouths that could open extremely wide.