About 65 million years ago, a massive asteroid blasted to Earth from space, blew a hole into the planet’s crust, and triggered an environmental disaster that blotted out the sun for two years. It caused not only the extinction of most dinosaurs but the destruction of other creatures too, including an extinct group of avians called enantiornithines. Which is a shame, because these early birds were very tiny and very cute, revealed a study on an extremely rare fossil on Monday.

The enantiornithine clade were birds before the dinosaurs that survived the asteroid turned into the birds we know today — and the recent discovery of a nearly complete fossil of a baby enantiornithine, scientists write in a paper in Nature Communications, reveals insights into how these birds developed and were cared for by their parents.

“This new discovery, together with others from around the world, allows us to peek into the world of ancient birds that lived during the age of dinosaurs,” study co-author and the Los Angeles County Natural History Museum’s Dinosaur Institute Director Luis Chiappe, Ph.D., said in a statement on Monday. “It is amazing to realize how many of the features we see among living birds had already been developed more than 100 million years ago.”

Artist impression of Enantiornithes by artist Raúl Martín.
An artist's rendition of what an enantiornithe might have looked like with a photo of a bug to scale. It's pretty cute.

At just five centimeters long, the 127 million-year-old enantiornithine is smaller than a human pinky finger. When it was alive, it would have weighed approximately three ounces — only about three-fifths as heavy as a battery. It’s remarkable the delicate fossil lasted for so long, but it’s even more special because the little guy who owned it died shortly after it was born. This was bad news for the bird but good news for the scientists because it allowed them to study where it was in its bone development process.

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Phosphorous mapping image and photo of the bird fossil.

Chiappe and his team used synchrotron radiation and elemental mapping to analyze the fossilized bones, which were discovered in the Las Hoyas deposits of Spain. During synchrotron radiation, charged particles accelerators blast the fossil with very intense light, allowing them to look at the specimen in extreme detail. This new technique allows scientists to get an unprecedented look at the process of ontogeny — that is, where an organism’s life and development actually begins.

fossil, bird
A composite image of the elemental map of the fossil.

The researchers in this study determined that the bird’s breastplate bone was mostly just cartilage, meaning it hadn’t had the time to develop into solid bone before it died. This means that it wouldn’t have been able to fly and would have had to rely on its parents for survival, much like living altrical birds like hawks and owls. (Birds that are precocial, like chickens, can largely survive independently after they are born.) The bone formation process demonstrated here, known as ossification, suggests that their developmental strategies were “more diverse than previously thought.”

The scientists hope that further analysis of the ossification observed here will “address important questions about their comparative developmental biology” and “help understand their morphological evolution and ecological differentiation.”

While we know that living birds evolved from carnivorous theropod dinosaurs that existed in the Jurassic period, there are no descendants of enantiornithines alive today. Close relatives to modern birds, these ancient creatures had teeth, claws on their legs, and likely flew differently than modern birds. That doesn’t mean they were any scarier than, say, ravens, but they represent an early stage of avian evolution that scientists are still attempting to understand.


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