In 1847, a French biologist described a second species of South America’s huge (3m) airapaima, the continent’s largest freshwater fish. But this species, Airapaima agassizii, was synonymized with the established species A. gigas and forgotten. Until, that is, Dr. Donald Stewart, professor at the SUNY College of Environmental Science and Forestry (ESF), got interested in the old literature about airapaimas. In the 1829 monograph that was the foundation of the 1947 description, he found drawings of a fish with visible differences in the teeth, eyes, and fins from the main species. We don’t have the skeleton, originally collected by a German scientist in 1819, used by the great Louis Agassiz to name this species: it was apparently destroyed in a bombing raid on Germany in WWII. Stewart considers that this passed unnoticed because very few specimens are collected by scientists: the fish, called pirarucu in Brazil, is everywhere endangered and is caught only by local fishermen, who consign it to market or table. You might say Stewart has gone all in on the pirarucu: not only has he re-described A. agassizii, but he’s resurrected another discounted species and is describing yet a fifth. He thinks there might be others: there are huge areas of the Amazon basin where no scientists has ever collected a specimen.
Do we still think no large species are awaiting discovery? One could argue these are cryptic, not cryptid, species: animals that look so much like each other they've not been properly discriminated. Either way, though, Dr. Stewart has one heck of a fish story to tell.