1 of 2 | A watercolor by geologist Henry De la Beche, from 1830, features a Triassic marine ecosystem dominated by large marine reptiles. The painting was inspired by fossils unearthed by paleontologist Mary Anning. Photo by Henry De la Beche/University of Bristol
BRISTOL, England, May 20 (UPI) -- New research suggests the arrival of marine reptiles like ichthyosaurs and plesiosaurs on the fossil timeline was sudden, and their ascent to the top of the food chain rapid.
"We show that when marine reptiles first entered the oceans in the Triassic period, they rapidly became very diverse and had many morphological adaptations related to feeding on varied prey," researcher Tom Stubbs, a palaeobiologist from the University of Bristol, said in a news release.
Stubbs is the lead author of a new paper on the rise of these so-called sea dragons, published this week in the journal Paleobiology.
"Within a relatively short space of time, marine reptiles began feeding on hard-shelled invertebrates, fast-moving fish and other large marine reptiles," Stubbs explained. "The range of feeding-related morphological adaptations seen in Triassic marine reptiles was never exceeded later in the Mesozoic."
Instead of estimating changing levels of biodiversity by counting species, researchers analyzed the morphological diversity of the predators' jaws and teeth. In the wake of a massive extinction event, which killed some 95 percent of life on Earth, ichthyosaurs and plesiosaurs quickly filled the ecological voids.
"What was unusual was that they were inventing entirely new modes of life that had not existed before the end-Permian mass extinction," said study co-author Michael Benton, also a professor at Bristol. "Our work shows they expanded into nearly every mode of life, indicated by their feeding habits and range of body sizes, really much faster than might have been imagined."
While the Permian-Triassic extinction event opened the door for the ascent of marine reptiles, a series of smaller extinction events during the Triassic also slowly pared away their biodiversity. In the 30 million years after their "evolutionary burst," several groups of ichthyosaurs and plesiosaurs were wiped out -- their specialized niches and morphological adaptations gone with them.
