Researchers discover way to determine sex of ancient bird species

January 22, 2013

Researchers discover way to determine sex of ancient bird species

Sex of ancient birds suggest dinosaur reproductive style.

Researchers have discovered a way to determine the sex of ancient bird species, according to the Natural History Museum of Los Angeles County.

Dr. Luis Chiappe, Director of the Natural History Museum of Los Angeles County’s Dinosaur Institute, says that Confuciusornis sanctus, a 125-million-year-old Mesozoic bird, had noticeable dissimilarities in plumage – some had ornamental tail feathers, others had none. Not until recently, however, have researchers proven that male Confuciusornis birds had ornamental plumage and females did not. Chiappe and his colleagues looked at hundreds of Confuciusornis fossils dug up from rocks deposited at the bottom of ancient lakes in northeastern China and discovered certain evidence of the gender difference: Medullary bone.

Chiappe says that their finding offers the first case of sex identification in an ancient bird. This is a major discovery because the ancient bird is closely related dinosaurs, such as the Velociraptor. People often want to know if dinosaur skeletons are male or female, says Chiappe, but only the “sex of a few” has been identified.

According to Anusuya Chinsamy of the Department of Biological Sciences, University of Cape Town, South Africa, female Confuciusornis birds placed the medullary bone inside their long bones, and then utilized it to generate the calcium-rich eggshells. Locating such tissue in a specimen that was void of long feathers suggested that those birds without ornamental plumage are females.

This finding allows scientists to examine gender differences in this ancient bird species, according to Chinsamy.

Researchers say that this finding also highlights a key difference between early and modern female bird species, as far as sexual maturity and reproduction are concerned.

“In human terms, knowing the sex of these specimens sheds light on when these early birds begin puberty,” says Chiappe, “Now we know that early birds began reproducing way before they were full grown, a pattern that contrasts with what we know of living birds, which typically begin reproducing after they reach full body size.”

Dinosaurs also began to reproduce before they were fully grown, according to researchers.

Scientists think that this finding will help them improve their understanding of the early evolution of birds.

The study’s findings are discussed in detail in the journal Nature Communications.

Photo credit: Stephanie Abramowicz, NHM Dinosaur Institute.


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