Spiders can only grow so large (on Earth) due to the pressure of gravity on their exoskeletons, right? Which is presumably why we don't have giant spiders running around terrorizing the countryside. But is it biologically possible for an ENDOskeletal "spider" to exist here? A creature with eight muscular legs -- maybe one that uses a sticky natural filament to make traps in caves and stuff? Feasible or no?
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