Fossils confirm that one of the first birds ate fruit

September 10 () –

In a new study published in the journal Current Biologyresearchers found fossilized seeds in the stomachs of some of the earliest birds.

This discovery shows that these birds ate fruit, despite the old hypothesis that this bird species fed on fish (and the more recent hypotheses that it ate insects). with their incredibly strong teeth.

Longipteryx chaoyangensis lived 120 million years ago in what is now northeastern China. It is one of the earliest known birds and one of the strangest.

“Longipteryx is one of my favorite bird fossils because it’s so strange: It has a long skull and teeth only at the tip of its beak,” says Jingmai O’Connor, associate curator of fossil reptiles at the Field Museum’s Neguanee Integrative Research Center and lead author of the study.

“Tooth enamel is the hardest substance in the body, and Longipteryx’s tooth enamel is 50 microns thick. That’s the same thickness of enamel on huge predatory dinosaurs like Allosaurus, which weighed 4,000 pounds, but Longipteryx is the size of a blue jay,” says Alex Clark, a PhD student at the Field Museum and the University of Chicago and co-author on the paper.

Longipteryx was discovered in 2000 and at the time, scientists suggested that its elongated kingfisher-like skull meant it also hunted fish. However, this hypothesis has been questioned by several scientists, including O’Connor.

“There are other fossil birds, like Yanornis, that ate fish, and we know this because specimens have been found with preserved stomach contents, and fish tend to preserve well. Also, these fish-eating birds had lots of teeth, all along the beak, unlike Longipteryx, which only has teeth at the tip of its beak,” says O’Connor. “It just didn’t add up.”

However, until now, no Longipteryx specimens had been found with fossilized food still in their stomachs. so that scientists could confirm what he was eating.

O’Connor visited the Shandong Tianyu Nature Museum in China, where he noticed two Longipteryx specimens that appeared to have something in their stomachs.

He consulted with his colleague, paleobotanist and associate curator of fossil plants at the Field Museum, Fabiany Herrera, who was able to determine that the tiny round structures in the birds’ stomachs were seeds from the fruits of an ancient tree. (Or, technically, seeds covered in pulp: “true fruits” are only found in flowering plants, which They were just beginning to flower 120 million years ago when Longipteryx lived.The trees that Longipteryx fed on were gymnosperms, relatives of today’s conifers and gingkos.

IF THERE WAS NO FRUIT, HE ATE INSECTS

Since Longipteryx lived in a temperate climate, it probably didn’t eat fruit year-round; O’Connor and his colleagues suspect it had a mixed diet that included things like insects when fruit wasn’t available.

Longipteryx is part of a larger group of prehistoric birds called enantiornithines, and this discovery marks the first time scientists have found stomach contents of an enantiornithine in the Jehol Biota of China. despite the thousands of fossils discovered.

“It’s always been strange that we didn’t know what they ate, but this study also points to a broader problem in paleontology: The physical characteristics of a fossil do not always tell the whole story about what the animal ate or how it lived.“, says O’Connor.

Since Longipteryx apparently didn’t hunt fish, that leaves one question: What did it use its long, pointed beak and incredibly strong teeth for? “The thick enamel is supercharged, it looks like it was using it as a weapon,” says Clark, who looked at modern birds to try to understand what Longipteryx did with its beak.

“One of the most common parts of the skeleton that birds use for aggressive displays is the face, the beak. Having a pickaxe as a weapon makes sense, because it moves the weapon away from the rest of the body to prevent injury.”

“There are no modern birds with teeth, but there are some really cool little hummingbirds that have keratinous projections near the tip of their rostrum that look like those seen on Longipteryx, and they use these as weapons to fight each other,” O’Connor says.

Hummingbird beaks that have been turned into weapons have evolved at least seven times, allowing them to compete for limited resources. Clark hypothesized that perhaps Longipteryx’s teeth and beak also served as weapons, perhaps evolving under social or sexual selection.