Arizona Folks.... What is THIS!!!!

Had this Duster brought up from Az about 4 years ago. Replacing a brake caliper once I came across a "shell" of a tiny scorpion. Now doing the other side UCA bushings, I came across this huge "sack" of something. It's soft but tough. It's probably a little bigger than a golf ball.

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Can’t see it, but there were scorpion like creatures under water hundreds of millions of years ago. I found a rock with a sea shell petrified in it in Kansas once. The center of the continental United States (& the Sahara desert of all things-whale bones) used to be a shallow sea.