It's been more than 300 millions of years vertebrates protected their young, at least according to a fossil discovered in Canada, find published Monday.
The fossilized scene shows an adult vertebrate that wraps with its tail a calf, in a gesture to protect her, which is the oldest example of parental care in vertebrates.
Both animals of a previously unknown species of "varanopidae" resembling today's lizards, belong to the extinct family of synapsids, terrestrial vertebrates from which mammals descend.
Fossils, of some 309 millions of years, were partially preserved on the cliffs of Nova Scotia, in Canada: one corresponds to an adult, of 20 to 30 centimetres long, and the other to a calf of some 8 Cm, placed behind the hind limb and surrounded by the tail, describes the journal Nature Ecology & Evolution.
The study suggests that the adult protected his calf by surrounding it with its tail, creating a kind of family cocoon, behavior suggesting that these animals provided "parental care" to their offspring, "helping them survive", said PAF Hillary Maddin, vertebrate paleontology researcher at Carleton University in Ottawa.
"Maybe they were hiding from predators. It seems that they were buried very quickly and died for it", explains the researcher.
It is the oldest known example of postnatal parental care (also called extended parental care) vertebrates, 40 millions of years before the previous discovery, in South Africa.
Parental care defines any parental behavior, males or females, aimed at improving the conditions and life expectancy of their offspring after birth.
These strategies are now widely used by most vertebrates (Birds, Reptiles, Mammals, fishes).
"Our discovery suggests that this behavior appeared very early in the lineage that led to mammals", said the researcher.
It also allows to "better understand the evolution" of the first vertebrates, that makes some 320 millions of years, separated into two branches, in one of them were the synapsidas (like these fossils) from which mammals descend and in the other reptiles, including birds.