Crinoids!
These are fossilized crinoids found in Western Australia by Tom Kapitany. Crinoids are animals and belong to the phylum Eichinodermata which includes starfish and sea urchins (and they all have “pentameral symmetry”). This is all well and good but these things, in their fossilized state, look like so much like the sentinels from The Matrix I wonder if there was any inspiration here.
Here are a few more fossils
Source: Fossil Huntress
And their basic anatomy
