How was this translucent alien head material made?

Hey,
I’m trying to understand how this material was made in the game Alien: Isolation

The alien has this translucent outer skull, and you can clearly see inner details like bone ridges or sockets underneath - but it’s not glassy. It feels organic, semi-soft, almost like resin.

The inside looks like it has depth or volume

There’s some sort of subsurface or fake volumetric layering

Any idea how this was done? Was this just translucent with subsurface scattering? A layered mesh trick? Or something custom?

Would love to recreate this look in Unreal Engine 5. Thanks!

Inside

Underneath