the Bone Wurm is the demonic version of the alien sand worms it spits out lost souls to murder a bro brutally and it also vomits fireballs like acid from the terrorkrawler. This boss is only in the later hell missions.
Trivia
After your kill a Bone Wurm it'll show the Acid Crawler parts due to a glitch.
When in vomits fireballs it is like the Terrorkrawler.