Functional changes in coloration are much "easier" (read: more likely) to develop through random mutation than functional changes to complex mechanical structures like bone structure or musculature. Given their predecessors were already under selective pressure by predation for millions of years prior, it's reasonable to assume they'd developed countershading (light bottom, dark top). Plus current agnathans are usually pretty dull.

Edit: oh geez, I misunderstood your message. It totally could have been a rainbow party blimp. That mostly depends on what their habitat was like.

Thanks for editing not deleting because TIL!

The eyes would suggest it's a predator.

Horror already without filters. I'm going to see that thing in my nightmares, fuckin hell.

Of course! I'm a biologist, I try to use my powers for good.

Not well. That's why most of its ancestors have fins nowadays

Prototype fish

This fish foresaw that evolution would lead to celebrity news, Return To Office mandates, and oversized utes, and decided it was happy precisely where it was.

That's what I thought! I'm too stupid to make anything more of it here for this community though

Don't you mean its descendants?

She call me Mr. Boombastic

Sacabambaspis

Or just that it needs to focus on from of itself like filter crabs, or that it needs to see through things like kelp forests or hole enterances.

Given it's size and the extreme binocular vision, it's unlikely to have any ambush predators.

I looked it up, it has bony plates all over it's body and likely a lateral line, so seeing predators directly may have been less necessary. It was also a suction feeder, so likely an active predator of much smaller things. It may have needed good forward vision because it's maneuverability was poor.

It is cute, isn't it?