Scientists in Northern Ireland have discovered that hammerhead sharks can reproduce asexually. In 2001, a female hammerhead shark that's been in captivity since it was a pup and didn't have any contact with a male for 3 years recently gave birth at a zoo on Nebraska. At first they thought mebbe she had incubated the sperm for 3 years or had mated with another species in the tank. When they tested the pup's DNA, it had no traces of paternal DNA. The DNA was only from the mother which also rules out mating with another species.

Dr Paulo Prodohl, of Queen's School of Biological Sciences, headed the university's research team and co-wrote the study said: "The findings were really surprising because as far as anyone knew, all sharks reproduced only sexually by a male and female mating.

"The discovery that sharks can reproduce asexually by parthenogenesis now changes this paradigm, leaving mammals as the only major vertebrate group where this form of reproduction has not been seen."

...
Co-author Dr Mahmood Shivji, who led the Guy Harvey Research Institute team, said: "It now appears that at least some female sharks can switch from a sexual to a non-sexual mode of reproduction in the absence of males."

The team established the most likely form of asexual reproduction that had occurred was a specific type called automictic parthenogenesis, which leads to less genetic diversity in the offspring compared to even the mother.

Aside:
In Jurassic Park, did the females start reproducing asexually, also?

i think some of the female dinosaurs turned into males so they could reproduce. It was based on them using a specific species of frog DNA to fill in the gaps of what they had from the mosquito blood.