65 million years ago, the fall of a meteorite on the Yucatán Peninsula dealt the decisive blow to the Earth’s climate, triggering an “impact winter” that led to the extinction of 75% of living species, including dinosaurs.
All but a small group, the Neornites, who we know as modern birds: how did they survive an event that wiped out all their near and distant relatives? We may have found the answer in the most unlikely place: a piece of dinosaur poo, in which were preserved a set of feathers that in turn hold the secret to the birds’ success. The discovery is reported in a study published on Current Biology.
Treasures in the poop
The technical term for fossilized dinosaur poop is “coprolite”; the one protagonist of this study was discovered almost by chance. Ten years ago, in fact, one of the authors of the study was collecting fossil fish in a deposit in Montana, in the Hell Creek Formation, which despite its anything but auspicious name is one of the most important fossiliferous sites in the United States, rich in finds ranging from the Cretaceous to the Paleocene, covering the period between the extinction of the dinosaurs.
Among the fish, Dr. David DeMar Jr. also found a reddish rock, the size of a golf ball, and took it to the laboratory for analysis, intrigued.
The ball turned out to be a coprolite, probably poop T. rex or of Nanotyrannus: it contained fish scales and above all bird bones and feathers. In particular, the “host” of the coprolite was a hesperornithiform, an extinct aquatic bird: a relative of the aforementioned Neornites, which unlike them did not survive the extinction of the dinosaurs. The shape of its feathers, and the comparison with those of other fossil birds, allowed the team to formulate a hypothesis relating to the “miracle” of the Neornites.
The importance of pens
The secret of their success (or at least their non-extinction), according to the authors of the study, is precisely in their feathers. Those of the bird devoured by the dinosaur were a mix between the feathers of modern aquatic birds, which are waterproof, and the more primitive ones of extinct birds and dinosaurs, which were instead smaller and “hairier”.
The modern feathers, which are those found in all Neornites, helped the birds during the post-meteorite winter, because they conserve heat and insulate them from the external environment. Birds that still had primitive feathers, or a mix of the two, were unable to adapt to the new climate.
In short, it’s all a question of efficiency: faced with the sudden arrival of the cold from the meteorite, only the Neornites survived, because they were covered by waterproof and insulating structures. The other dinosaurs, including extinct birds, were not equipped, and went the way of three-quarters of living species.
