A recent study, published in The Science of Nature and conducted by several researchers of the Council and a colleague of the University of Texas, described for the first time a group of modern birds that survived the Creaceous Palogene mass extinction that occurred 65 millions of years ago and led to the disappearance of the dinosaurs.
The modern birds (Neomithes), a group that includes all the current species of this type, are different from most primitive birds because the beak has no teeth, there is a reduction of the hand bones (without claws) and a short tail formed by a small pygostyle that supports the tail feathers.
The new bird family was baptized Vegaviidae. “These species, which are distant relatives of the current duck, inhabited the continents of the southern hemisphere. They were divers in marine environments and had compact bones with thick periostium, as in the case of the penguins, which allowed them to submerge easily”, Federico Agnolin, who is the first author of the research, states. He is a CONICET’s postdoctoral fellow at the Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” (MACN-CONICET).
It is worth mentioning that the fossil record of modern southern birds that inhabited the Earth during the Mesozoic Era (which started 251 millions of years ago and finished 65 millions of years back), time in which the dinosaurs lived, is scarce now. There is a group that is better represented: the primitive birds known as Enantiornithes which have repitilian features such as claws and sharp teeth in the jaw, for instance.
Nevertheless, despite the lack of fossil records, some modern southern birds that inhabit the planet at the time of the dinosaurs could be analyzed and compared thanks to the work of different paleontologists.
Species that belong to the Cretaceous period (which began 65 millions of years ago and finished with the Mesozoic Era, 66 millions of years back) such as the Vegavis iaai and Polarornis gregorii were found in Antarctica, a region that used to be covered by thick forest, like the ones that can be found in the south of Argentina which are inhabited by various species of dinosaurs and aquatic birds.
Another bird fossil is Neogaeornis wetzeli, a species known from the isolated remains of Chile, and the recent discovery of fossil records in New Zeland that belonged to a bird that inhabited the planet in the stage right after the extinction of the dinosaurs, baptized Australornis lovei.
“In 2016, there was one study published in Nature which showed the almost complete and greatly preserved skeleton of the Vegavis iaai. That publication allowed the scientists to know in detail the anatomy of the modern bird of the Cretaceous. And all that enabled them to conduct a study in which they resorted to anatomical comparisons and recognized that all those species that had been described belonged to one same family called Vegaviidae” Fernando Novas states. He’s a CONICET’s principal researcher at the MACN who also participated in the study.
The researchers formed a hypothesis on the reason why the modern birds managed to survive the extinction of the Cretaceous-Paleogene period, in which most of the dinosaurs and different primitive birds disappeared.
“Just as the living birds, the Vegaviidae grew quickly and reached adulthood in less than a year, as it was shown in the paleohistological analysis of the bones of Vegavis and Polarornis. This surely allowed them to overcome the difficulties of living in one environment as cold as Antarctic and probably influenced the survival of the group in the great extinction at the end of the Cretaceous”, Federico Brissón Egli, researcher at the MACN and author of the study, concluded.
By Miguel Faigón
About the study:
Federico L. Agnolín. Posdoctoral fellow. MACN and Universidad Maimónides
Federico Brissón Egli. MACN.
Sankar Chatterjee. Museum of Texas Tech University.