In the very first room of the fossil part of the museum there is a squid like fossil. I would love to have one in my house, but none of the placards tell me what it is, so I can be on the look out for it. Thanks!
I think it's just a random thing Blathers puts there to spice up the display. The big 'theme' of the fossil room in NH's museum is evolution and how various fossil species are related to one another and to currently living species. The squid in particular goes up when you donate an Ammonite to demonstrate that cephalopods continued to exist even after ammonites went extinct.