[This is a fascinating little excerpt I came across. This is clearly not a common thing, but even so, this is definitely strange. Jan]

In a story about Sharks, it had this interesting piece:

Some captive female sharks have been known to reproduce without the aid of a male, essentially cloning themselves, Shiffman said. In 2001, a female hammerhead shark gave birth in the Henry Doorly Zoo in Nebraska without mating with a male, taking researchers by surprise. It’s an example of parthenogenesis, wherein embryos can be created with external fertilization, and has been seen in all types of animals except for mammals.

Source: https://www.livescience.com/38701-8-weird-facts-about-sharks.html