About Hexanchus griseus
Like its cousin the Notorynchus, the Hexanchus has a different body build like most extant sharks. To begin with, they have six long gills on each side, a big broad head, a dorsal that is situated near the tail. They can reach almost five meters in lenght and weight just over a 500kg. The eat: sharks, seals, crustaceans, bony fish, cephalopods and carrion. (Almost anything they find). They have been observed not being very active during the day but at night they rise from the sea bottom to hunt. They have green fluorescent eyes.
The teeth also look similar to those of a seven gilled shark, those are combed-shaped but more evenly distributed in shape. (they look soemthign you could comb your hair with)
Age and Distribution
This Hexanchus griseus fossil tooth is from the Pliocene of Belgium. This shark lived approximately 33-2,6 million years ago. We know that this shark species is wide spread over the world and today is found in temperate and tropical waters.
H. griseus co-inhabited the sea with other sharks like the monster shark Megalodon: (Otodus megalodon), Megamouth shark (Megachasma cf pelagios), Sleeper shark aka Greenland shark: (Somniosus microcephalus), Basking shark: (Cetorhinus maximus) and many more sharks. Besides sharks other animals swam in these waters like: bony fish, rays, birds and marine mammals like toothed whales, dolphins and seals.
About the Hexanchiformes Hexanchus griseus
Hexanchus griseus (better said the hexanchiformes) can trace their history back to the Jurassic period, where the first fossils of the sixgilled sharks have been found.
H. griseus belongs to the Hexanchidae which is a subclass of the Hexanchiformes. They’re more commonly known as Cow Sharks. Another member of the Hexanchiformes from this time period is: Notorynchus cepedianus the broadnose sevengill Shark.