When climate change, volcanic eruptions and rising sea levels simultaneously hit the Earth approximately 250 million years ago, life on the planet took a hit. Marine life in particular got hit hard, with 96 percent of all species going extinct. Now, a study of a strange new marine reptile fossil sheds light on the evolution of marine species after this extinction and calls previous evolutionary theories into question.
The new study examines a new marine reptile - Sclerocormus parviceps - an ichthyosaur that conflicts with all of the current rules of these dinosaurs' characteristics and suggests that the evolution of marine life after the massive extinction was rapid instead of slow.
Ichthyosaurs were a group of marine reptiles that bore similarities to today's dolphins, with characteristic long-beak snouts, streamlined bodies and tail fins. However, the new species possessed a short snout and a long, whip-like tail lacking any fins at the end. Even stranger, it is toothless, and researchers believe that it used its snout to suck up food like a syringe.
"Sclerocormus tells us that ichthyosauriforms evolved and diversified rapidly at the end of the Lower Triassic period," said Olivier Rieppel of The Field Museum and co-author of the study. "We don't have many marine reptile fossils from this period, so this specimen is important because it suggests that there's diversity that hasn't been uncovered yet."
"Darwin's model of evolution consists of small, gradual changes over a long period of time, and that's not quite what we're seeing here," he added. "These ichthyosauriforms seem to have evolved very quickly, in short bursts of lots of change, in leaps and bounds."
In addition, the existence of animals such as Sclerocormus, who lived right after the extinction event, can help scientists determine and understand the response of life to massive environmental pressures.
"We're in a mass extinction right now, not one caused by volcanoes or meteorites, but by humans," Rieppel said. "So while the extinction 250 million years ago won't tell us how to solve what's going on today, it does bear on the evolutionary theory at work. How do we understand the recovery and rebuilding of a food chain, of an ecosystem? How does that get fixed, and what comes first?"
The findings were published May 23 in Scientific Reports.
