The Wikipedia article is incorrect, Monero still uses ring signatures. Bulletproofs are used as efficient range proofs in RingCT to hide the amount in transactions.
Honestly, comments like this are why I stick with hacker news.
Thank you! There's a lot of difficult-to-google info locked up in comments like this, and I truly appreciate the effort spent replying to randos like me :)
https://www.getmonero.org/2017/12/07/Monero-Compatible-Bulle...