This is an enemy I thought up today. As you can see the names of these creatures are Inhaling Carbod and Inhaling Nitrod. The latter is a boss. I'll explain the general creature first.
Gascalls is the name of their family. They have a thick shell which no Pikmin can break through. However, they can latch on and weigh the creature down. Yes, they fly/float. These creatures don't breathe oxygen either, instead a different gas found underground.
The Inhaling Carbod has a hole in the ground similar to the Hermit Crawmad, which is visibly leaking a lavender gas. When Pikmin come close, the creature will come out the hole and attempt to inhale Pikmin. The creature has 10 seconds out of the ground until it needs to start breathing again, and it will scurry back to its hole. Now, you can either destroy the hole or weigh it down to prevent it reaching the hole. For every second it is out the ground, it's health will deplete. This creature must be kept out the ground without its gas for 20 seconds.
This creature, obviously much larger, is found in an arena. The arena has a thick layer of the gas building up at the bottom and a large hole in the middle. When the player approaches, it's two huge arms will come out the ground and it will pull its body up. This creature has 20 seconds out of the ground before it needs to breathe its gas again. You can't destroy the hole this time around, so instead you must weigh it down as much as possible to prevent it returning to the hole. It inhales Pikmin much faster. The creature must be kept out the ground for 2 minutes to kill it.
After a quarter of its HP is gone, it will remove its previous hole and dig a new one somewhere else.
After two thirds of its HP are gone, it will start to grab Pikmin off its body and inhale them.