Sharks were already evolved beings when they lived with dinosaurs

New fossils of a shark similar to a ray show that these animals were already highly evolved in the Upper Jurassic, between 163.5 million and 145 million years ago.

Cartilaginous fish, such as sharks and rays, are an evolutionarily very old group of animals that lived on Earth before the dinosaurs, more than 400 million years ago, and survived all five mass extinctions. Its fossil remains can be found in large numbers all over the world, although normally only the teeth survive, while the cartilaginous skeleton decomposes and does not fossilize.

However, in the Solnhofen Archipelago, in Bavaria, Germany, skeletal remains and even skin and muscle of Upper Jurassic vertebrates were preserved under special conservation conditions. An international team of researchers took advantage of this circumstance to analyze the hitherto unclear role of the now extinct Protospinax annectan in the evolution of sharks and rays, with the help of modern genetic evidence.

Protospinax lived about 150 million years ago and was a cartilaginous fish about 1.5 meters long, flattened, with expanded pectoral fins and a prominent spine in front of each dorsal fin. Although known from well-preserved fossils, the phylogenetic position of Protospinax has intrigued researchers since it was first described in 1918.

According to the author of the study, cited by “Europa Press”, paleobiologist Patrick L. Jambura, it was “of particular interest” to know “whether Protospinax represents a transition between sharks and rays as a missing link”. It has also been speculated that Protospinax may have been a very primitive shark, an ancestor of rays and sharks, or an ancestor of a particular group of sharks, the Galeomorphii, which includes today’s great white shark.

With the most recent fossil discoveries, Jambura and the team reconstructed the family tree of today’s sharks and rays using genetic data and fossil groups integrated with morphological data. The results of the analysis were surprising: Protospinax is neither a “missing link”, nor a ray, nor a primitive shark, but a highly evolved shark. The findings were published in the scientific journal “Diversity”.

“We tend to think of evolution as a hierarchical, ladder-like system in which the oldest groups are at the bottom while humans, as a very young species in Earth’s history, are at the top. , evolution has never stopped even for these primitive representatives, they continue to evolve day after day through changes in their DNA, just as we do. This is the only way they managed to adapt to constantly changing environments and survive until the today”, concluded Jambuca.