From the Super Mario Wiki
Spiky Piranha Plants are a sub-species of Super Piranha Plant that appear in the game Super Mario Galaxy 2, acting as Prickly Piranha Plants. There is only one in the entire game, encountered in the Sky Station Galaxy during the "Storming the Sky Fleet" mission.
This enemy holds a key to the locked up Power Star nearby. It attacks in the same way as its purple variant: slamming its head onto the ground. The player cannot jump on it due to its spikes and must use the nearby Stretch Plant to defeat it by hitting its head when it is down on the ground. Once the enemy is beaten, Mario can collect the key and obtain the Star.
Names in other languages
||Rovo Piranha iracondo
||Iracund Bramble Piranha