The thresher shark was known to humans as far back as 300 BC, and was mentioned by the Greek philosopher Aristotle. At the time it was believed that threshers could bite through fishing lines and swallow their young to hide them from predators. While these tales are untrue, these “clever” behaviors gave rise to the shark’s nickname – the fox shark. Even the common thresher’s species name references this – “vulpinus” means fox.
While the bigeye thresher was determined to be separate from the common thresher as far back as 1840, the pelagic thresher’s status as a separate species would not be suggested until almost a hundred years later. Even then, there were doubts from scientists, until further scientific analysis in the 1990s showed that its closest relative is actually the bigeye thresher, and not the common thresher.
This analysis also suggested that there may be a fourth thresher shark species living off the Mexican coast of the Baja California peninsula. However, not much is known about this species, except that it seems to visually resemble the bigeye thresher.