1. The nautilus is a cephalopod, related to the octopus, squid, and cuttlefish, but it's different in that it has a shell. Another ancient cephalopod, the ammonite, also had a shell, and that's the extinct creature I was confusing it with.

2. In American English, it's guh-VOORTS-truh-MEE-ner. (Wikipedia)

3. It means the comic, and what the comic stands for. It's a vowell-less unpronounceable word that presumably didn't exist before the comic (and, one suspects, this resulted in a very short, easily registerable domain name). It is not an acronym, nor any other kind of initialism. (Wikipedia)

4. It's called a "club". (Wikipedia) The inventor of the sandwich had to buy a special double-sliced bun to put the sandwich on, because otherwise the sauce made it too sloppy. (Pittsburgh Post-Gazette) Presumably, the sandwich is made today by double-slicing an extra-tall sesame seed bun.