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FOR IMMEDIATE RELEASE

SDSU Researcher Rewrites Fossil Record Book
Discovery Establishes Modern Group of Placental Mammals 90 Million Years Ago

SAN DIEGO, Monday, Nov. 5, 2001 - Figuring evolutionary history 90 million years back is tough business, but a top San Diego State University biology professor has done just that thanks to discoveries that prove modern placental mammals existed 25 million years earlier than previously thought.

In the Kyzylkum Desert of Uzbekistan, J. David Archibald and colleagues discovered the precedent-setting fossil remains of an animal called Kulbeckia, a member of an obscure group of mammals called zalambdalestids that are thought to be related to modern rabbits and rodents. At 85 million to 90 million years old they are the oldest of their kind ever found.

Archibald's article about the discovery appeared today in Nature, a premier international science journal.

"Previous to our discoveries it was believed that modern placental mammals -- those that utilize a specialized kind of placenta to nourish their developing fetuses -- didn't appear until the dinosaurs died out some 65 million years ago, but our work changes all that," Archibald said. "In 1996 we published a paper in Science showing that early relatives of hoofed mammals and whales existed some 85 million to 90 million years ago. Our newest discoveries just published in Nature show that another group including rabbits and rodents also pulls back the record of placental mammals by 25 million years."

Additionally, Archibald said, molecular scientists around the world are reaching the same conclusions about the beginning of some modern placental groups. "Every day we see a clearer picture of where these mammals, which include humans, came from," Archibald said.
Archibald heads expeditions back to the Uzbekistan site on a regular basis. In the last three years, with help from colleagues from Uzbekistan, Russia, Britain, America and Canada, Archibald has screen-washed almost 60 tons of sandy material to collect the fossils. "We call ourselves URBAC," he said. "Our work takes a lot of digging and a lot of sieving."

San Diego State University is the oldest and largest higher education institution in the San Diego region. Since it was founded in 1897, SDSU has grown to offer bachelor's degrees in 78 areas, master's degrees in 61 areas and doctorates in 13. SDSU's more than 33,000 students participate in academic curricula distinguished by direct contact with faculty and an increasing international emphasis that prepares them for a global future.

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