Parental care of offspring after birth, also known as extended parental care, is common among many vertebrates today, including birds, reptiles, mammals, fish, and amphibians. Fossils of a new species of creature known as a varanopid, seen here in an illustration, showcase what appears to be the oldest known evidence of this complex behavior in a vertebrate ancestor.
Today, most of the remaining trees on Cape Breton Island, off the coast of Nova Scotia, are typical of a boreal forest. But during the Carboniferous period, which stretched from about 360 to 300 million years ago, the region was a subtropical swamp dominated by lycopids, giant relatives of today’s club mosses that could grow over a hundred feet tall.
The petrified, hollowed-out stumps and roots that remain today have been found to contain the fossilized bodies of many animals that populated the area at the time. Some of them are completely jumbled, while others are seemingly frozen in the position they were in when a flash flood covered them in sediment.
Now, the island’s fossil-rich cliffs have not only yielded a new Carboniferous creature, they have also revealed that complex parental care may have much more ancient roots than we thought.
Described today in the journal Nature Ecology & Evolution, the 309-million-year-old fossil includes the remains of an adult varanopid, a lizard-like animal from an extinct group that is traditionally considered to be an early part of the lineage leading to mammals. Behind its hindleg and encircled by its tail, the fossil also holds the diminutive skull of what looks like a juvenile of the same species.
“We believe it may show the oldest example of parental care ever documented for this group,” says study coauthor Hillary Maddin, a paleontologist at Carleton University in Ottawa, Canada.
Inferring such behavior from a fossil might sound like a bit of a...