Captive fish don't typically digest their tankmates. So long as they're provided with ample food, things tend to stay copesetic in large enclosures, even when predators are in the mix. But staff at Seuol's COEX Aquarium just found out the hard way that it can happen. A large ragged-tooth shark (also known as a grey nurse or sand tiger shark) was caught in the act of swallowing a 1.2-metre (3.9ft) banded hound shark.

Forget turducken, sharksharkin is all the rage. 

Staff suspect the raggie won't keep the meal down for long, as its size could make it hard to digest, but that may not be the case. Ragged-tooth sharks typically feed on small fish, crustaceans and squid, but they have been known to eat small sharks in the wild. 

How the species got its common name is no mystery. Those needle-like teeth aren't great for chewing, but in combination, the many rows allow the shark to grab firmly onto its prey, which is swallowed whole. 

As a tooth breaks off, its replacement is never far behind. One raggie can replace up to 30,000 teeth in its lifetime. Though this super-set of chompers is ferocious in appearance, these are generally passive sharks and pose little threat to divers.

This incident is yet another great example of how the "apex predator" trope doesn't fit all shark species. In fact, most sit a bit lower in the food web than you might expect. Last year alone brought us footage of sea lions eating thresher and leopard sharks, blue sharks eating leopard sharks and even a squid with a taste for catshark!