[MrB]

I find that hard to fathom. Over 80 MM years, it’s environment didn’t change enough to apply any adaptive pressure.

[Bigg Red]

I find that hard to fathom.

***
Pun?

[UCANSEE2]

I find that hard to fathom.

(very subtle : ) )

Well, they say Sharks haven't 'evolved' for millions(tens/hundreds/ of?) years. Which isn't really true, but is as true as the idea this fish hasn't evolved.

I imagine it used to grow much larger. As far as 'adaptive pressure', the pressure only comes if something threatens the viability of a species. What would these things have to fear at that depth ?