Las Hoyas fossil study
Las Hoyas, Spain is known for spectacular fossils preserved in 126 million-year-old rocks deposited in a lake environment /HKU HKU MOOC / HKU Vertebrate Palaeontology Laboratory.

The ancient hatchling of birds like chickens and ducks came out of the egg running, according to 125 million-year-old Early Cretaceous fossil beds of Los Hoyas, Spain.

The fossil findings have long been known for producing thousands of petrified fish and reptiles but one special fossil -- a nearly complete skeleton of a hatchling bird -- stands unique and is one of the rarest of fossils, said researchers.

Michael Pittman from the University of Hong Kong and Thomas G. Kaye from the Foundation for Scientific Advancement in the USA found the lifestyle of this ~3cm long hatchling bird by studying the previously unknown feathering preserved in the fossil specimen.

Las Hoyas fossil study
HKU MOOC / HKU Vertebrate Palaeontology Laboratory.

Chickens and ducks are up and about within hours of hatching, they are "precocial" unlike pigeons and eagles which are "altricial". When precocial birds hatch they have developed down feathers and partly developed large feathers and can keep warm and get around without mum's help.

"Previous studies searched for but failed to find any hints of feathers on the Los Hoyas hatchling. This meant that its original lifestyle was a mystery," says Dr Pittman.

Michael Pittman and Thomas Kaye used a high power laser to study very small chemical differences in the fossils in different colours, revealing previously unseen anatomical details. The new results on the hatchling bird revealed that they had feathers at birth and was thus precocial and out of the egg running. Previous attempts using UV lights failed to detect the feathers and the latest laser technology demonstrates that some early birds adopted a precocial breeding strategy just like modern birds, said researchers.

Las Hoyas fossil study
HKU MOOC / HKU Vertebrate Palaeontology Laboratory.

Thus, even during the time of dinosaurs, some enantiornithine bird babies had the means to avoid the dangers of Mesozoic life by following their parents or moving around themselves. "One of the feathers discovered was of a substantial size and preserves features seen in other hatchlings. It indicates that our hatchling had reasonably well-developed flight feathers at the time of birth", says Jesús Marugán-Lobón, another author of the study from the Universidad Autónoma of Madrid, Spain.

Las Hoyas fossil study
HKU MOOC / HKU Vertebrate Palaeontology Laboratory.