**Sharks: A Misunderstood Family Tree**
The concept of sharks as a natural biological group has been challenged by recent findings in genomic studies. The study, published last month on the bioRxiv preprint server, suggests that sharks might not be a single evolutionary lineage after all. Instead, some species of sharks may be more closely related to rays and skates than to other sharks.
The research analyzed genomes of 48 shark, ray, and other animal species representing all major lineages of Chondrichthyes, which is the group that includes sharks, rays, and skates. The study found that when looking at ultra-conserved regions of the genome, a peculiar family of sharks called Hexanchiformes may be part of an evolutionary lineage distinct from the group that includes all other sharks, as well as skates and rays.
This finding implies that most animals we call sharks are more closely related to rays and skates than to hexanchiform shark species. This is similar to what was found in some species called “fish” by evolutionary biologist Stephen Jay Gould many years ago.
The study also suggests that flat-bodied animals, including manta rays, evolved from shark-like ancestors. This means that rays and skates are just another type of shark, and the shark body plan came first.
The implications of this finding are significant for understanding the evolution of key traits in these ancient creatures. “Having an accurate phylogeny is a way forward for understanding the processes that have shaped life,” says Gavin Naylor, an evolutionary biologist at the Florida Museum of Natural History.
While more research is needed to determine which tree is correct, this study highlights the importance of accurately charting the evolution of key traits in ancient creatures like sharks.