When we think of dinosaurs, the word "big" often comes to mind. From the 12-meter-long Tyrannosaurus rex to the 22-meter brontosaurus weighing 15 metric tons, few doubt that giants ruled the world. But there was also room for much smaller creatures, including a chick whose skeleton was found in the rock deposits of Las Hoyas. The specimen died shortly after hatching, never weighed more than nine grams, and is so small that official data compare it to a cockroach.
The enantiornithines (technically Enantiornithes) were the most abundant group of birds in the Mesozoic era, so much so that their remains have been found on every continent except Antarctica. In this case, that aspect equates to information (or rather, "potential" for information), and experts have never stopped searching for fossils that might help solve this ancient puzzle. A team of specialists led by Dr. Fabien Knoll from the University of Manchester presented a study in Nature Communications in the middle of last year (which was published yesterday) focusing on one of the most important findings to date: a baby enantiornithine fossil.
The data suggest that the chick died shortly after hatching, measured less than five centimeters (similar to a cockroach or a pinky finger), and weighed less than nine grams. One of the most striking discoveries is that the sternum was made of cartilage and had not yet developed enough to become solid bone at the time of death, meaning it also could not fly. This raises new questions for experts. Did the chick depend too heavily on its parents? The lack of bone development does not allow confirmation, and everything suggests that evolutionary strategies of birds were much more diverse and complex than previously thought.
In short, researchers have their hands full. Despite the original abundance of enantiornithines, fossils of chicks and embryos are very rare, so the search for additional specimens continues. This chick was found in Las Hoyas, a paleontological site located very close to the city of Cuenca in Spain. Maybe they will have more luck there? We will soon find out.
University of Manchester
