Did you know that most sharks have got five gill slits on each side, but there are few with six gill slits, too? One of them is the bigeyed sixgill shark.

Hexanchus nakamurai JNC2615 head.JPG
By Jean-Lou JustineOwn work, CC BY-SA 3.0

The bigeyed sixgill shark belongs to the family Hexanchidae or Cow sharks. They all have more than 5 gill slit pairs and are assumed to be the most primitive of all sharks, since they resemble many extinct forms.

Bigeyed sixgill sharks are primarily deepwater sharks and feed mostly as scavengers. They like warm temperate and tropical seas worldwide.

Bigeyed sixgills mature with, on average, 1,50 m (5 ft) length and reach up to 1,80 m (6 ft). They are ovoviviparous (that means the eggs remain inside the female’s body until hatching) with 13–26 pups per litter, measuring up to 45 cm (17 in) at birth.

Their eyes are quite beautiful: fluorescent green and really big – hence their name.

Sources: here and here