Okay so. Time to explain the head of an #Ethorus (and other info)

Despite seaming like a simple skull for a head it's a lot more complicated then that. The outer skull is not the Ethorus' actual head, it's more like a super dense protective shell. There actual head resides inside the secondary skull.
The reason for this is that and Ethorus' head is extremely delicate and is just (as seen in the pic) exposed mussels and tissue. It in not covered in any skin what-so-ever. There are some cases of an Ethorus being born without this protective outer shell, but most have died due to the lack of protection.

Young Ethorus are born with a soft outer skull, which when paired with their roundness can lead to some unfortunate deformity which can be harmfully for them later in life.

An Ethorus will often avoid too much damage to their protective shell, for if too much dose occur it can be extremely deadly for them.

Ethorus are also predatory creatures and will not hesitate to hunt anything bigger or smaller then them for food. They are also omnivores and can eat just about anything. Since they cannot chew their food they must either swallow it whole or only eat small chunks/pieces at a time.
They are very hardy and resourceful creatures.
They also have a very wide field of view which makes sneaking up on them quite difficult.

The teeth on the outer skull are much tougher and sharper then normal which allows them to crush bones (and sometimes stones/rocks) quite easily.