"Jawed vertebrates have had at least two genome duplications, and Dr. Pascual-Anaya and his colleagues were curious whether the hagfish showed evidence of them too. They discovered that one of these duplications must have happened before the two groups of vertebrates split — the hagfish genome has signs of it — but the other was most likely after the fork in the evolutionary road. What’s more, they confirmed a suspicion other scientists had raised, that an ancestor of both the hagfish and the lamprey, another jawless wonder, at some point tripled its genome."

https://www.nytimes.com/2024/01/16/science/hagfish-slime-eel-genome.html