After a farmer in northeastern China picked a fossilized flying lizard out of the ground last year and sold it to a museum, paleontologists quickly noticed a broken wing - and an egg nestled next to the animal's tail. The scientists dubbed the spectacular specimen "Mrs. T" - a contraction of "Mrs. Pterodactyl" - and are announcing her as the first prehistoric flier to be assigned a sex.

She provides vital clues to the mating habits of the creatures that ruled the skies for 150 million years before birds appeared.

David Unwin, a paleobiologist at the University of Leicester in England who studied the spectacularly preserved fossil, called it a "once-in-10 lifetimes" discovery. Unwin and colleagues published the finding Friday in the journal Science.

The scientists who studied Mrs. T surmised that 160 million years ago, an accident snapped her wing and dumped her into a lake or stream, where she drowned with a wrinkly, leathery egg at the ready. The egg slipped into the mud that encased her.

The pterosaur - the newer nomenclature for her class of creatures - offered us an egg, but it's what she's missing that's most informative. Her long, narrow beak lacks any adornment, although other pterosaur fossils found nearby sport tall crests atop their heads. In fact, about 40 percent of the 133 known pterosaur species have such crests, the tallest measuring five times higher than the head.

Junchang Lu, who studied the fossil at the Chinese Academy of Geological Sciences in Beijing, said the lack of a crest on Mrs. T proves that only males grew them.

Like a peacock shaking his tailfeathers, a male pterosaur displayed his crest to win the female, said Chris Bennett, a paleontologist at Fort Hays State University in Kansas. In 1993, Bennett first proposed the theory of crest-as-mating-lure among the pterosaurs. But there has been no direct evidence until now.

The males of many species of birds also display impressive crests, which females judge based on size and brightness. In the late 19th century, Charles Darwin proposed that such ornaments, when found only in males, must serve a sexual purpose. For instance, the size and showiness of bird crests often became exaggerated through the generations as males competed for mating rights.

And so it is that Mrs. T belongs to a felicitously named species, Darwinopterus, meaning Darwin's wing.

Mark Witton, who studies and reconstructs pterosaurs at the University of Portsmouth, said other pterosaur fossils show that crests tend to sprout at the beginning of adulthood, which supports the theory that they were used to attract mates. "It gives us this idea of competition between the males. They're saying, 'My crest is bigger than your crest.' "