Tarantox

The Giant Space Spider is one of the bosses in Super Mario Galaxy. It is found wrapped up in a web inside the Sticky Planet and can be reached via the Front Route in the Super Mario Galaxy demo.

Mario gets to it by using a Wobble Launcher to break the shell off of the Sticky Planet, revealing its web and the spider in a hunk of ice. Mario then must use another Wobble Launcher to tear the web and free the spider, then battle it.

Combat
The spider first spits green goopy acid or poison at Mario, which stings him and drops his health by one point. Then, after the spider has been damaged, it shoots the acid out of four of its five red glowing bumps on its skin, which is harder to evade.

To defeat the spider, Mario must use Wobble Launchers and throw himself at the red glowing buttons to pop them, then the spider will fall upside down, revealing three more red bumps on its underbelly. If Mario pops all of them, the spider will come back onto its feet and attack faster. If Mario repeats the procedure one more time, the spider will fall through its web and go flying into space, revealing a Star.

Outlook
The Giant Space Spider is, obviously, giant.

It has three big oval eyes that are wide, wings, and a Snifit-like mouth. Though, every (known) boss in Super Mario Galaxy has a tubular Snifit mouth.

It has five big red glowing buttons/dots/bumps/poison bubbles on its back, one extremely huge and the others about Mario's size. On its belly underneath, it has three more that are essential to keep it alive. If these three are popped using Wobble Launchers, the spider will gets hurt. Hurt it twice to defeat it.

It Has Wings?
For some odd reason, as seen screenshots of Super Mario Galaxy, the Giant Space Spider has wings. Could it be a Spiderfly? Only Super Mario Galaxy's future release will tell why Miyamoto decided that this boss should have wings.