The new species—dubbed Cronopio dentiacutus for its narrow snout and long fangs—was about 8 to 9 inches (20 to 23 centimeters) long and likely used its pointy teeth to hunt and eat insects.

The second oldest mammal skull ever recovered from South America, C. dentiacutus existed when dinosaurs still roamed Earth—providing a tantalizing glimpse into the history of early mammals, experts say.

(See "Odd Saber-Toothed Beast Discovered—Preyed on ... Plants?")

Paleontologists found the mostly complete skull in 2002 outside a rural village in northern Argentina. At the time, however, the skull was mostly hidden in rock, and its identity remained a mystery.

So in 2005 the scientists sent the skull to a technician, who spent three years removing