From Terraria Wiki
Vertebrae is a crafting material dropped by Crimeras, Blood Crawlers, Face Monsters and the Floaty Gross. They are used much like Rotten Chunks for worlds that spawn with a Crimson biome instead of a Corruption.
 Used in
- 1.2.3: Can now be dropped by the Floaty Gross.
- 18.104.22.168: You can now craft battle potions with vertebrae.
- 1.2: Introduced.