From beaches to rainforests and urban playgrounds, ants occupy nearly all of Earth¿s habitats. Indeed, these industrious creatures, of which there are nearly 10,000 described species, are arguably the most successful of the terrestrial animals. Because they figure so importantly in most environments, researchers have long been fascinated with the details of early ant evolution. Curiously, the fossil record suggested that ants did not begin their rise to power until about halfway through their evolutionary history. But according to a report published today in the Proceedings of the National Academy of Sciences, a fossil worker ant preserved in New Jersey amber from deposits dating back some 90 million years ago to the Cretaceous period suggests that ant diversification began earlier and proceeded more rapidly than previously thought.

The new fossil ant, described by David Grimaldi and Donat Agosti of the American Museum of Natural History in New York City, appears to represent a living subfamily of ants known as the Formicinae, members of which are characterized in part by their use of a defensive spray of formic acid. Dubbed Kyromyrma neffi, it and two other fossil ants that belong to the subfamily Ponerinae are the only Cretaceous representatives of modern ant subfamilies yet known. The modern lineages of ants, it appears, may have evolved their specialized body plans during the first third of their evolutionary history. Still, because such 90-million-year-old fossils are rare, it seems likely that the ants did not rise to "ecological dominance" until millions of years later.

Sorting out which ecological and historical factors might have led to these two stages of ant diversification will require solid paleoecological data and a well-supported ant family tree, Ted R. Schultz of the National Museum of Natural History remarks in a commentary accompanying the report. "We can only hope that this cycle of discovery and revision will continue or even accelerate so that our current, clouded picture of ant phylogeny will come increasingly into focus, in much the same way, perhaps, that the initially vague but evocative form of a Cretaceous ant becomes progressively clearer when a nugget of amber is painstakingly prepared and polished by [David] Grimaldi and colleagues."