The Serpent Gyaos also known as Long-Tailed Gyaos was the game-exclusive monster in Gamera: 2000.
Gameplay shows this Gyaos Sub-Spece range from Jet Fighter Size to twice the size of Gamera. It seems to travel in packs and has two main attacks, a red Sonic Beam and purple Sonic Bombs.
This monster has no official name and has not made an appearance outside Gamera: 2000.