An MSU paleontologist has discovered a new explanation for the extinction of trilobites - the small hard-shelled creatures that existed about 250 million years ago.
Danita Brandt, a faculty member in the Department of Geological Sciences, said the extinction can be attributed to inconsistent molting, or shedding, of the trilobites' outer skeleton and their inefficient behavior.
Her findings were published in the September issue of the Australian paleontology journal Alcheringa.
"They would shed their old exoskeleton any way they could," Brandt said. "It raises questions on why such a successful creature didn't survive."
She said its climate changes, sea-level fluctuation, effects of meteorite impact and an increase of predators were possible reasons for their extinction. Fossil records show trilobites started to decrease when aquatic animals such as fish and squid increased.
Brandt said modern arthropods shed their skin the same each time, causing her to believe it impacted their extinction.
Michael Velbel, chairperson of the Department of Geological Sciences, said it's the second big discovery he has read about in the past two weeks. He said there are 18 faculty members in the department that are working to publish work in major journals.
"It's terrific stuff," Velbel said. "This is a new perspective on a problem that a lot of people have worked on over the years and still are working on. I'm glad to see it out there with all the other ideas."
Brandt said trilobites, which lived in the bottoms of the Earth's ancient seas for more than 300 million years, are one of the key signature creatures of the Paleozoic Era. She said they are extinct relatives of lobsters and crabs from the arthropod family that lived long before dinosaurs.
"Dinosaurs get all the press, but trilobites are really popular with collectors because they're so neat and cute," she said. "They dwindled away way before the dinosaurs."
Brandt said trilobites that had fewer body segments lived longer since fewer body segments was a lower risk molting-related accidents.
"Modern arthropods shed their skin quicker minimizing the period they are venerable to predators," she said.
Brandt said today's arthropods use their shed exoskeleton to get their energy back and absorb some of the minerals, which trilobites do not do.
When they shed their skin, it leaves them weak and vulnerable to predators, she said. "New predators appearing and inefficient molting style - it was a formula for destruction," Brandt said.
She said that after 12 years working in the field, the finding was her crowning achievement.
"Extinction is a complicated jigsaw puzzle and this is my contribution. Now I'm ready to leave the field," she joked.
Robert Anstey, professor of geological sciences, said he has worked with Brandt on projects and even helped critique her work.
"It will raise some new questions in the field," he said. "It will influence new thinking."
Brian Charlton can be reached at charlt10@msu.edu.
