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The arachnosaur is a large spider-like creature native to the planet LV-117 and presumably introduced to LV-118. It dwells in the more arid regions of the planet, and buries itself in the sand in order to ambush its prey, spinning a web that serves as a tripwire. Springing out of the sand, it is a fearsome sight, with its eight massive legs and giant fangs, but if it is met with resistance it will flee.

Fiction

2005 IDW continuity

Wheelie was ambushed by an arachnosaur in the deserts of LV-117. The beast inadvertently bit into his energon convertor, shocking it with a jolt of energon. The arachnosaur fled without devouring Wheelie, but he was forced to make repairs to his convertor. Spotlight: Wheelie Wheelie intended to bring an arachnosaur and a Chaosteros off-world with him when LV-117 was nearing destruction, but both creatures were killed when he had them attack Monstructor. Syndromica (2)

Presumably Wheelie was able to find additional arachnosaurs, as one was seen skulking around on his next home, LV-118, when Garnak and Codder pulled Rodimus back to their ship. The Stars My Destination

Games

Transformers Roleplaying Game

The arachnosaur was one of the many predators native to LV-117. Decepticon Directive