And your link to possible correcting evolution re CaCO3 led to a link to guess what - Pelican spiders and their cousins the Trap-jaw spiders..wow!
Now my preying instincts tell me that it may just be good for this community to lure the Smithsonian lass (one Hannah M Wood), who is pertinently involved in researching above species into this web..
And seeing that I am not suitably qualified, maybe one of you guys - @mountainwashere, @holothewise, or @branbello could lay down the bait...?
This Hannah M. Wood?
Looks like her - the 'pelican spiders' link above also features her stating i.a. "At the Smithsonian's National Museum of Natural History, curator of arachnids and myriapods Hannah Wood has...", with more detail elsewhere on the page.