Is there precedent in official material for small creatures to mount bipedal creatures 2 sizes larger than them?

Question

Rules for Mounted Combat

A willing creature that is at least one size larger than you and that has an appropriate anatomy can serve as a mount, using the following rules.

Once during your move, you can mount a creature that is within 5 feet of you or dismount. Doing so costs an amount of movement equal to half your speed. For example, if your speed is 30 feet, you must spend 15 feet of movement to mount a horse. Therefore, you can’t mount it if you don’t have 15 feet of movement left or if your speed is 0.

If an effect moves your mount against its will while you’re on it, you must succeed on a DC 10 Dexterity saving throw or fall off the mount, landing prone in a space within 5 feet of it. If you’re knocked prone while mounted, you must make the same saving throw.

If your mount is knocked prone, you can use your reaction to dismount it as it falls and land on your feet. Otherwise, you are dismounted and fall prone in a space within 5 feet it.

Now, "appropriate anatomy" is somewhat vague and largely encourages a DM to make their own rulings, which is fine, but I'm mostly curious if there's any precedent of small NPCs, Monsters, or other such creatures riding a bipedal creature 2 sizes larger than them, such as a Large creature. I'm specifically curious about bipedal creature mounts because I'd like to pitch an idea to one of my DMs that involves a goblin character of mine riding one of his large, bipedal summons (I'll respect whatever his rulings are, of course, and I'm pretty sure he'll let me regardless, but my curiosity burns).

In a lot of media, such as Lord of the Rings or pretty much any series with large size differences between characters, it can often be seen that especially small creatures and characters might ride on the shoulders or hang off the back of a significantly larger creature. Is there precedent for this in official publications?

Classical examples of this I've seen in mostly Lord of the Rings and a couple books include:

• Goblins riding on a chained Ogre's back
• Halflings riding in the branches of an Ent
• A Goblin riding on the shoulders of a Giant

Obviously these aren't things that're necessarily in DnD 5e's core books and WotC's adventures, but I'm wondering if any such precedent actually exists, beyond good-natured Barbarian PCs giving their smaller party members piggyback rides, of course!

Answer 1

Ogre Howdah

This trope isn't lost on D&D, even if its rules support is rather slim. In Mordenkainen’s Tome Of Foes/Mordenkainen Presents: Monsters of the Multiverse there's the Ogre Howdah which can carry up to 4 goblins (or other small folk) on the small fort on its back.

Answer 2

Sort of but the creatures are of the same size

Tomb of Annihilation campaign features tribes of Batiri Goblins that live in the jungle and they are explicitly described as capable of riding on each other's shoulders:

Battle Stacks. Batiri warriors sometimes ride on each other's shoulders in battle, in a formation known as a battle stack. These can be up to nine goblins tall. (…) Only the goblin at the top of the stack can attack, and only the goblin at the bottom can move (…)

The description goes on to point out that this is something they invented to be able to fight larger enemies and implies that it's a skill that requires at least some time to master but still, it's very much possible.

Extrapolating from this, it should be possible and even much easier for a creature to ride on the shoulders of a larger one but it's up to the DM to rule whether it's something a pair of creatures not explicitly trained to fight in this way will be able to pull of in the middle of a fight.

Answer 3

Yes

Tomb of Annhilation features dinosaur racing. The text says:

Most competitors in the two-legged race are hadrosauruses and deinonychuses (again with Small riders).

While deinochuses are medium-sized, the Hadrosaurus is a Large beast, and they are bipedal.

In Icewind Dale: Rime of the Frostmaiden, Auril is a Medium monstrosity in her normal form, and is riding a Gargantuan Roc, a creature that is even more than two size categories larger than her (and bipedal, even if that is not its normal mode of travel).

Answer 4

Wyvern Mounts

Wyverns, although cousins of dragons, are bipedal with their rear legs for walking and perching and their front limbs as a pair of wings. They are size Large.

Someone mounted on a wyvern would likely need to mount its shoulders in the manner envisioned by OP; an aerial harness or saddle might work in flight, but when it was landed, being mounted on its back would result in one facing the sky rather than facing forward. Its posture is described as:

If forced into a confrontation on the ground, a wyvern crouches low, keeping its stinger poised above its head as it hisses and growls.

The lore description of wyverns says that:

A wyvern can be tamed for use as a mount, but doing so presents a difficult and deadly challenge.

Unofficially, Christopher Perkins responded to a tweet seeking more information about Wyvern mounts.

Owlbears?

Owlbears are both size Large and officially used as mounts:

Savage Companions. Although they are more intelligent than most animals, owlbears are difficult to tame. However, with enough time, food, and luck, an intelligent creature can train an owlbear to recognize it as a master, making it an unflinching guard or a fast and hardy mount.

What is not clear, however, is whether it is bipedal and how one would mount it. The canonical illustration in the Monster Manual shows it on all fours, but makes no textural reference to how it moves or fights. The fact that it has two claw attacks presumably means it rears up to attack, but it could be as capable as an owl at walking bipedally and only occasionally drop to all fours like a bear. The 5e MM illustration does not show us its tail; both the 1e version and the plastic toy on which it was based had a long, heavy tail which may have helped it be primarily bipedal.

A note about Perytons
Perytons are bipedal, size Medium creatures - yet they are one of the possibilities for mounts when using the spell Find Greater Steed. It is not clear whether the mounts summoned by the spell are re-sized to match the caster, or whether specific over general the spell permits you to break the rule that a mount must be one size larger than its rider. In any event, OP's size Small character could use a 'wild' one, not summoned by the spell.