If we start to list animal species close to humans, it would surely take us a while to conclude that the shark once shared the same common ancestor with us. Now, it is the first time that evidence of this ancestor has been found.
A team of researchers from the University of Chicago, University College Dublin and the University of Cambridge have found evidence suggesting that humans and sharks shared a common ancestor approximately 440 million years ago.
The find has been produced from the study of a 385 million-year-old shark fossil.
When this fossil was found in 2001, it was first believed that the shark lacked teeth, and for that reason, scientists gave it the name Gladbachus adentatus.
But now, years later and after a new effort, the researchers carried out a much more exhaustive study of the remains, and in doing so, they discovered that, in fact, it represented a kind of transition between Acanthodians and Chondrichthyes . A short piece of evidence that provided a better picture of a time period for which there are few fossil records.
The evidence suggests a new estimate of the time during which humans and sharks shared a common ancestor, roughly 440 million years ago.
The specimen is the only one of its kind found: that of a shark that lived approximately 385 million years ago, during a period known as Devonian, which lasted from 416 million to 358 million years.
The first vertebrate being with a jaw
As it is the first living vertebrate with a jaw, it constitutes the first ancestor, not only of all fish, but also of mammals and, therefore, of humans.
Reconstruction of the skull of Gladbachus adentatus./ Doi: 10.1098 / rspb.2017.2418
The remains consisted of three sections, all flat compressed in resin. The resin shell retained much of the endoskeleton, allowing the team to collect tissue samples. The teeth, skull, cartilage and gill details were also preserved.
The researchers note that the body of the specimen looked like a sheet of scales and that the bones in its head were very coarse.
The researchers also note that even though the study has clarified some of the evolutionary history of sharks, it has also complicated understanding of their lineage: They found evidence to suggest that shark evolution has many branches , several of which appear to converge. leading to features found in modern sharks, such as the long throat and multiple gill slits.
Their study also confirmed that Gladbachus adentatus actually had a large number of teeth, both small and large.
References :
Michael I. Coates et al. An early chondrichthyan and the evolutionary assembly of a shark body plan, Proceedings of the Royal Society B: Biological Sciences (2018). DOI: 10.1098 / rspb.2017.2418
