Sergeant Major Bonecrack is an antagonist in the third book of the Astrosaurs Academy series, Terror Underground. He was a raptor soldier who fought in Raptor War Ten, and was on a secret mission to locate and destroy Captain Liress's work on Astro Prime. He came to the continent of Isissia with his pilot, another raptor named Komo. Unfortunately for him, his ship, a mark two Doom-Bringer equipped with an assault shuttle, was trapped in a web made by Liress's giant spiders. The spiders took the pair to her science ship, and she was about to report their capture to the DSS when an avalanche struck, burying all three of them in snow.
Sixty years later, Colonel Erick thawed out the astrosaur ship, accidentally freeing Bonecrack and Komo, who captured Damona and Netta in a lab on Level One at ray-gunpoint. The raptors marched them to the ship's control room and threatened Teggs and Dutch. Suddenly, the frozen form of Captain Liress sprang to life and helped the cadets defeat the raptors. Their minds had fogged up from their years entrapped in ice, and they didn't remember where their ship was until they fled a giant spider and fell right onto it. Bonecrack managed to get into his ship while Komo cleaned the web away from the assault shuttle. Bonecrack planned to complete his mission and destroy Astro Prime once he escaped the caves and entered orbit. However, his breakout was delayed because the Doom-Bringer's power cells needed to recharge. Teggs, Blink, and Dutch fell onto the raptor craft, too, and the stegosaurus landed on Komo, stunning him. However, all three Daring Dinos were captured by the giant spiders and the raptors continued to prepare for takeoff.
When Teggs's and Damona's teams reunited, the Daring Dinos decided to catch Bonecrack while Damona's Darlings went to get help. The Daring Dinos arrived on the scene just as Bonecrack had prepared the assault shuttle and decided to drop an avalanche on his ship to stall him. The plan didn't work, though, because Bonecrack's shields melted the snow. While this was going on, the giant spiders were preparing a web to catch his ship again. The Doom-Bringer took off, ramming into the web. However, Bonecrack wasn't fazed and tried to blast through anyway- but he wasn't counting on hordes of spiders blocking his path with their bodies. Bonecrack's engines finally gave out and he was stuck in the web. The spiders caught the raptors just as Commander Gruff arrived to take both Bonecrack and Komo to jail.
- Bonecrack and Komo provide the first illustration of raptor battle armour: a blood-red chest plate held on with straps and a red helmet with a spike on top.
- Bonecrack belongs to a type of raptor without black stripes, unlike General Loki's raptor warriors.