In a recent study published in the British journal Nature Ecology and Evolution, the Canadian and British teams reported fossils of a previously unknown species of lower-hole species, which are similar to modern giant lizards. The fossil sample, which is about 309 million years old and includes an adult and its children’s larvae, is the earliest known pro-parenting sample to date, indicating that pro-parenting occurred 40 million years earlier than previously thought.
Progeny is common in many vertebrates today, including birds, reptiles, mammals, fish and amphibians, but not in other groups. Past studies have shown that the earliest evidence of pro-breeding comes from a second-century fossil of the South African lizard Delongko (298 million – 251 million years ago). However, tracing the origin and evolution of parenting behavior is challenging, as fossil evidence of parenting and children is rarely found.
This time, scientists such as Hilary Martin of The University of Carlton in Canada described parts of the skeleton of the lizard-dalongs, known as “D. unamakiensis”, which is located behind the adult hind limbs and is circled by an adult tail. They come from the Charcoal Age and were found inside a tree stump in Nova Scotia, Canada. The hidden area inside the stumps may be their nests, the team said, and their pro-generation and children stay together for long periods of time to protect their children.
The location of lizards such as “D. unamakiensis” on the animal’s evolutionary tree remains a matter of debate. This group has traditionally been divided into lower-hole species – the ancestors of mammals. In another paper published in Nature Ecology and Evolution, David Ford and Roger Benson of the University of Oxford argue that lizards are not related to mammals, but rather part of perforated reptiles, which eventually form crocodiles, lizards, snakes, turtles and birds.