China is known for being a treasure trove of incredibly well-preserved fossils. Do some digging in the right site, and you might find dinosaurs (including birds!) with fossilised feathers or preserved skin and scales. Now, a team of researchers from the Institute of Vertebrate Paleontology and Paleoanthropology has made a discovery that is particularly amazing ... and a little bit gross: fossilised bird vomit!
Many of us might remember sitting in science class and being presented with an unappetising hunk of compacted fur and bones: an owl pellet. Carnivorous birds have a habit of swallowing prey whole, but they can't digest everything. Fur, bones, claws, teeth and other stomach-clogging materials get collected into a pellet, and tossed back out the way they came in:
During the Cretaceous Period, there lived an archaic group of birds called the enantiornithes. They weren't quite like modern birds – most had teeth, for example – but thanks to this newly discovered fossil, we now have proof that they produced pellets, too. In fact, at 120 million years old, this find may be the oldest gastric pellet in the fossil record.
In the same way that modern biologists study birds' pellets to learn about their diet, palaeontologist Min Wang explained how this prehistoric pellet – which was packed with fish bones – sheds light on the ancient birds' digestive habits. "It's just so lucky to find a pellet preserved along with the bird," Wang told me.
The discovery reveals that ancient enantiornithine birds, though they still boasted teeth, had already evolved similar eating habits to modern birds. Not only did they swallow their fishy food in one gulp, but their gizzard was also equipped to create a pellet. On top of that, their throats were effective at antiperistalsis, which is a fancy science term for throwing up.
"In birds, the two sections [of the stomach] are distinctly separate from each other, and you can see the gizzard is very muscular," Wang said. The gizzard's job is to collect and compact indigestible material into a pellet. "We [humans] like to tear meat from the bone," he told me as he pantomimed using a knife and fork. "But birds don't do that." Instead, they rely on their digestive system to separate out the hard stuff.
While presenting the discovery at this year's meeting of the Society of Vertebrate Paleontology, Wang pointed out that distinguishing pellet from poop can be a tricky task. "To be honest, it's very difficult to tell the difference unless you have good evidence," he said. In this case, the pellet contained a number of fairly big chunks of bone, pieces that almost certainly would have been too big to make it through the tight spaces at the end of the bird's digestive system.
Discovering that this ancient enantiornithean produced pellets has Wang and his colleagues wondering if the feature evolved even earlier, in the birds' meat-eating dinosaur ancestors. Evidence from fossils indicates dinosaurs had gizzards that they filled with rocks to help grind food, much like crocodiles do today. Wang is hopeful that future research will show that even before birds evolved, small dinosaurs had developed a strong, pellet-producing gizzard. Puking Velociraptors? We'll have to stay tuned to find out.
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Top header image: Min Wang
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