The Gnashjaw

Order: Eucinetophiformes

Family: Pulverognathidae

Genus: Pulverognathus

Things with tough shells, such as crawlers and skiddlecrabs typically can trust on their defences in order to avoid predation. Something with a shell so strong naturally gets harder to crack open. But the nutritious, soft flesh underneath he shell of such creatures is quite an appealing prospect to certain species, which inevitably leads into some species evolving methods in order to crack open the tough shells of these creatures. And one species takes it to the extreme.

Enter the gnashjaw, an eucinetophiform pelagys, a massive 3 metre long eel-like durophage with a powerful set of intimidating jaws, allowing it to crack open even the toughest of skiddlecrab shells, the very hardest of bones and other similarly tough and hard shelled organisms, breaking through their defences as if they were nothing.

This specialised durophage boasts an impressive pair of jaws, which are extremely large and robust, with large, broad teeth inside which it uses to crush up skiddlecrabs and other similar organisms. Powerful muscles form the backbone of the crushing jaws, and are extremely powerful, taking up significant space in the skull, powering these stout jaws, allowing them to crack open pretty much any hard shell, making them surprisingly effective predators, allowing them to trade speed and agility for a more bulkier, slower form. Their prey isn't particularly fast, anyway.

Despite their powerful crushing jaws, they cannot crack open skiddlecrabs with just this. They have specialised teeth reinforced with iron. Specialised peg-like teeth at the front of the jaw allows them to pick up their prey, and crushing batteries of flat molars at the end of the mouth allows them to crush and masticate. To prevent excessive wear and tear, their teeth are stained orange by iron, which protects them from damage and mechanical stress, so that they can constantly use them.

In order to hunt for prey, the gnashjaw typically uses its vision or olfactory senses in order to detect prey. Say, a large skiddlecrab. The gnashjaw would approach it from above, as it can't directly use its claws to pinch prey overhead; it assumes a defensive position. Grasping it deftly using its peg-like front teeth, it then pushes its prey back into its mouth and then puts it in the perfect position between all the molars, and then closing its jaws rapidly to masticate and crush up its prey, and then promptly swallowing it, shell and all. The undigestible bits get shot back out and regurgitated.

While this predator typically feeds on skiddlecrabs and crawlers, mostly the large species. which have evolved alongside it in an evolutionary arms-race, the gnashjaw is a habitual bone-eater, with its powerful iron teeth allowing it to crack open tough bones to access delicious marrow inside, and even eating small bones as its massive, robust jaws are not very precise, eating all the bone and marrow to gain the most out of this nutritional bounty.

This strange eucinetophiform is the only one in its family (Pulverognathidae) and has no close living relatives, presumably due to competition with the skiparees, which feed on small skiddlecrabs much more effectively than these ancient, eel-like pelagys due to their powerful pharyngeal jaws and much more precise and smaller jaws, which led to most of the smaller to medium-sized species  to go extinct. Much of its living relatives also have specialised for different niches, but the gnashjaw sticks to being a durophage, specialising on only the very largest of skiddlecrabs, whose massive and robust shells protect them from the majority of predators, all except for this one.