Palaeontologists thought they had figured out why the odd-looking bird had such sharp, rock-solid teeth, until they found something odd in its stomach…
Back in 2000, palaeontologists discovered the fossils of an ancient kingfisher-like bird in north-west China: Longipteryx chaoyangensis. It’s believed to be among the earliest known birds. It’s also one of the oddest.
It was about the size of a bluejay, had a long skull, and incredibly hard teeth on the end of its beak. At the time, scientists thought they knew why the prehistoric bird had these unusual features.
But in a new study published in the journal Current Biology, researchers reveal that the recent discovery of two Longipteryx specimens on a museum shelf – and more specifically what was found inside their stomachs – provides irrefutable proof that this original hypothesis is wrong.
When Longipteryx was discovered more than 20 years ago, scientists thought that its long skull and hard teeth meant that it hunted fish, much like kingfishers do today.
However, other scientists, including Jingmai O’Connor, associate curator of fossil reptiles in the Field Museum’s Neguanee Integrative Rehowever, thought otherwise.
“There are other fossil birds, like Yanornis, that ate fish, and we know because specimens have been found with preserved stomach contents, and fish tend to preserve well. Plus, these fish-eating birds had lots of teeth, all the way along their beaks, unlike how Longipteryx only has teeth at the very tip of its beak,” explains O’Connor. “It just didn’t add up.”
However, no specimens of Longipteryx had been found with fossilised food still in their stomachs for scientists to confirm what it ate, until recently when O’Connor visited the Shandong Tianyu Museum of Nature in China, where she noticed two specimens that appeared to have something in their stomachs.
Intrigued to find out if her suspicions were correct, O’Connor consulted with her colleague Fabiany Herrera, Field Museum associate curator of fossil plants, who was able to confirm that the tiny, round structures in the birds’ stomachs were seeds from the fruits of an ancient tree – a relative of today’s conifers and gingkos.
The researchers suspect that while seeds made up a large proportion of Longipteryx‘s diet, it also ate things such as insects when fruit wasn’t available.
“It’s always been weird that we didn’t know what they were eating, but this study also hints at a bigger picture problem in palaeontology, that physical characteristics of a fossil don’t always tell the whole story about what animal ate or how it lived,” says O’Connor.
“Longipteryx is one of my favourite fossil birds, because it’s just so weird,” says O’Connor, associate curator of fossil reptiles in the Field Museum’s Neguanee Integrative Research Center and the study’s lead author.
So, if Longipteryx wasn’t hunting for fish, then what was it using its long, pointy beak and strong teeth for?
“The thick enamel is overpowered, it seems to be weaponised,” says Alex Clark, a PhD student at the Field Museum and the University of Chicago and a co-author of the paper.
“Tooth enamel is the hardest substance in the body, and Longipteryx’s tooth enamel is 50 microns thick. That’s the same thickness of the enamel on enormous predatory dinosaurs like Allosaurus that weighed 4,000 pounds, but Longipteryx is the size of a bluejay,” Clark explains.
To try to understand how exactly Longipteryx was using its beak, Clark analysed a number of modern bird specimens. “One of the most common parts of the skeleton that birds use for aggressive displays is the rostrum, the beak. Having a weaponised beak makes sense, because it moves the weapon further away from the rest of the body, to prevent injury.”
“There are no modern birds with teeth, but there are these really cool little hummingbirds that have keratinous projections near the tip of the rostrum that resemble what you see in Longipteryx, and they use them as weapons to fight each other,” O’Connor adds.
The researchers are keen to find out more about the life of this weird prehistoric bird.
“We’re trying to open up a new area of research for these early birds and get palaeontologists to look at these structures, like the beak, and think about the complexity of the behaviours that these animals might have engaged in beyond just what they were eating,” concludes O’Connor.
“There are many factors that could be shaping the structures that we see.”
Main image: skull of Longipteryx, showing its teeth. Credit: Xiaoli Wang
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