Similar to an eel in that it was largely misunderstood and undiscovered until relatively recently?

My favorite, rarely discussed, fun fact about Freud is that he was originally a marine biologist trying to be the first person to find eel genitalia. After like 20 years of failing at that he gave up and moved on to the far simpler task of enumerating the human condition

For those out of the loop, scientists were puzzled for centuries about how eels reproduce because they couldnt find any with genitals. Obviously we know they must have them though. Within the last 5-10 years we finally discovered that eels dont grow their genitals until their final stage of life (after like 40-60 years), when they return to the Sargasso sea to breed and then die. They dont even eat in their final stage. Just 100% focused on fucking and dying. We first had to figure out that they breed exclusively in the Sargasso before we could finally understand how they work, and find eels that had their genitals