Madeline Green (PhD student) is the lead author on a study showing that litters of shark pups can have many fathers. The study compared litters from Scalloped Hammerhead and Grey Reef sharks and found it was more common with Hammerheads. Read more here or look it up
Green, M. E., Appleyard, S. A., White, W. T., Tracey, S. R. & Ovenden, J. R. (2017). Variability in multiple paternity rates for grey reef sharks (Carcharhinus amblyrhynchos) and scalloped hammerheads (Sphyrna lewini). 7, 1528.