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Ancient Flying Reptiles Likely Had Sex As Youths

John Roach
for National Geographic News
March 12, 2008
 
Pterosaurs, like their dinosaur relatives, didn't wait until they were fully grown to have sex, a new study suggests.

Researchers examined microscopic tree ring-like growth markings in hundreds of bones from a species of the extinct flying reptiles discovered in central Argentina in the 1990s.

The Pterodaustro guiñazui bones came from multiple individuals, including an embryo inside an egg and adults with wingspans between 1 to 8 feet (0.3 to 2.5 meters).

P. guiñazui lived during the mid-Cretaceous, about a hundred million years ago.

"It is quite amazing that even after millions of years, the microscopic structure of the bone is still intact," study author Anusuya Chinsamy-Turan, a paleobiologist at the University of Cape Town in South Africa, said by email.

Rapid Growth

The team found that the pterosaur attained about 53 percent of its adult body size in just two years.

At that point, the flying reptile was likely sexually mature. Its growth continued slowly for three or four more years.

(Related news: "Dinosaurs Had Sex As Teens, Study Says" [July 20, 2007].)

"Then they stopped growing and maybe they didn't live much longer," said paleontologist and study co-author Luis Chiappe, director of the Dinosaur Institute at the Natural History Museum in Los Angeles, California.

The finding shows that the flying reptiles, like dinosaurs, did not grow throughout their entire lives—as do modern turtles and crocodiles, Chiappe said.

Chiappe, Chinsamy-Turan, and Laura Cordornú from the National University of San Luis in Argentina described the growth patterns of the pterosaur last month in the journal Biology Letters.

(The research was funded in part by a grant from the National Geographic Society. National Geographic News is owned by the National Geographic Society.)

Similar to Dinosaurs

Kristi Curry-Rogers, a paleontologist at Macalester College in St. Paul, Minnesota, studies growth patterns in dinosaurs.

She said the pterosaur growth pattern is similar to what she and other scientists have found in a variety of dinosaurs.

"All of them grow faster than modern reptiles, and none of them grow as fast as modern birds," she said. "That's something that's consistent across analyses."

Modern birds reach their full adult size within about a year but often delay reproduction for several years. Eagles, for example, begin to mate at about age four.

The addition of pterosaurs to this data set pushes the evolution of faster growth rates back along the lineage of animals that split from modern reptiles and gave rise to birds, Curry-Rogers noted.

"We're seeing some really interesting biological changes that I can't imagine didn't contribute to their long success on Earth," she added.

Grow Fast, Die Young?

Their faster growth rates were beneficial because they likely allowed early sexual maturity, Chiappe said.

Other scientists have speculated that such a growth strategy helped dinosaurs pass on their genes before the harsh, and often deadly, realities of older age set in.

(Related: "For Tyrannosaurs, Teen Years Were Murder" [July 13, 2006].)

Since the tree ring-like growth marks end once a pterosaur has reached adult size, Chiappe said he and colleagues are uncertain how long P. guiñazui lived.

However, he noted that only a few individuals in their sample of hundreds of pterosaurs appeared to be more than six or seven years old.

"It's likely that these animals did not live very long," he said.

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