BUFFALO, N.Y. -- Tiny sea creatures called rhabdopleurids reside on the ocean floor, building homes of collagen on the shells of dead clams. Rhabdopleurid colonies are small, and the critters are by no means the dominant animals in their ecosystem.
But they have lived this way -- and survived -- for more than 500 million years. And in doing so, they have outlasted more elaborate species that also descended from a common ancestor, according to a new study in the journal Lethaia.
Though rhabdopleurids' age and modern existence are well-documented, the paper breaks new ground by identifying them as a predecessor to ancient zooplankton -- known as pelagic graptolites -- that went extinct about 350 million years ago.
The lesson, according to lead author Charles Mitchell: Newer isn't always better.
"We think that change is always going to lead us to a better place, that evolution is always going to lead to something better," said Mitchell, a University at Buffalo geology professor. "But all this progress in making all these wonderful pelagic graptolites didn't lead them to take over the world. They didn't survive, but these simple dudes, these bottom-dwelling creatures, did."
Mitchell's partners on the research included Michael J. Melchin from St. Francis Xavier University in Nova Scotia, Canada; Chris B. Cameron of the Universit de Montral; and Jrg Maletz from the Frei Universitt Berlin.
The paper, which appeared online on Aug. 2, used rhabdopleurids' structure and form to determine that they were some of the most primitive graptolites that ever existed.
While their zooplankton relatives evolved rapidly, splitting into many new species and evolving many new traits, rhabdopleurids pretty much stayed the same over the course of history.
As the zooplankton developed ways to live closer to the ocean's surface, the rhabdopleurids continued dwelling on the ocean floor. The zooplankton became important players in their new ecosystem
|Contact: Charlotte Hsu|
University at Buffalo