She used the buoyant cube as a head shield.

The mouth is interesting because as the lower jaw moved down the head shield moved allowing for a large opening.

If the latter is the case, then aptychi may have had a function similar to the head shield of modern nautiluses.

In most species, there are two eyes at the front side of the head shield, often merged into a single eye lobe.

The rest of body was covered by long, strap-like scales behind the head shield.

There were also a pair of large extensions at the front of the head shield.

The head shield has two pairs of long rearward spikes.

The head shield had a series of grooves over the whole surface forming an extensive lateral line organ.

No internal skeleton is known outside of the head shield.

The head shield provided some lift though, and would have made the cephalaspidomorphi better swimmers than most of their contemporaries.