What would an animal with a movable upper jaw look like?

[soy_king]

I've recently realized that for every single alien species we've ever come up with, not one has had a movable upper jaw and a stationary lower jaw. This is very likely because no creature that has a mandible and maxilla has such an anatomy, but what would an animal (or sentient being) with a movable upper jaw and stationary lower jaw look like? Would the rest of its face also be positioned below the jaw? How would it break down food?

 

[Racist Trash]

A Canadian.

 

[Exigent Circumcisions]

Your mom.

 

[Larkin N Likin]

 

[Bell Peppers and Beef]

The OP.

 

[A Welsh Cake]

I imagine that it’s lower jaw would act like whale baleen whilst the top jaw scoops stuff in,
So imagine a crocodile that opens its mouth like a snake.

 

[soy_king]

Nice try, but that's just the dog's whole head moving up while it's jaw moves downward, giving off the appearance that the maxilla is moving.

 

[soy_king]

I imagine that it’s lower jaw would act like whale baleen whilst the top jaw scoops stuff in,
So imagine a crocodile that opens its mouth like a snake.

That... sort of works. I thought something similar, but I'm wondering where the upper jaw would connect to the rest of the skull where it doesn't interfere with the function of the eyes or nose.

 

[Jewthulhu]

I've never been big on zoology or animal taxonomy, but from what I can find some animals have the ability to move the upper jaw relative to the braincase. The best example is probably the snake.

 

[User names must be unique]

Pretty sure birds can move their upper "jaws", Why are aliens always bilaterally symmetrical, what would an alien look like with quadrilateral symmetry look like?

 

[soy_king]

Pretty sure birds can move their upper "jaws", Why are aliens always bilaterally symmetrical, what would an alien look like with quadrilateral symmetry look like?

As @Jewthulhu's source points out, some reptiles, fish, and birds have limited movement of their upper jaw in addition to a fully mobile lower jaw. I feel like an akinetic lower jaw with a fully movable upper jaw is something either so rare or evolutionarily disadvantageous that it's difficult for us to conceive of.

Couldn't some form of starfish have quadrilateral symmetry?

 

[Creep3r]

I think Dixon's After Man had some creatures with movable upper jaws.

 

[Bland Crumbs]

The Predator?

 

[soy_king]

The Predator?

If you look at it closely, the Predator essentially has two sets of jaws: the outer ones are kinetic, but move to the side like an insect, while the inner ones look like a regular human, with a fixed upper jaw and a kinetic lower jaw.

 

[Overly Serious]

I'm stuck on why an animal would have a moveable upper jaw in the first place. Whether you consider the upper jaw or the lower jaw to be the movable part is really just a question of which half of the mouth has the greater mass attached.

So to get what you want we're either looking at an animal that has the greater mass attached to the lower half of its face, i.e. brain case, eyes, etc are all at the bottom and the mouth is at the top of its head - perhaps it evolved in an evironment where it easts from exclusively above itself either an acquatic creature that eats from the water surface or something that eats from trees? Or alternately its mouth isn't attached to a head with a brain at all. Like an octopus with mouths at the end of its tentacles or something.

Either way, separating the upper jaw from a big brain case seems the most likely way for this to come about.

 

[soy_king]

I'm stuck on why an animal would have a moveable upper jaw in the first place. Whether you consider the upper jaw or the lower jaw to be the movable part is really just a question of which half of the mouth has the greater mass attached.

So to get what you want we're either looking at an animal that has the greater mass attached to the lower half of its face, i.e. brain case, eyes, etc are all at the bottom and the mouth is at the top of its head - perhaps it evolved in an evironment where it easts from exclusively above itself either an acquatic creature that eats from the water surface or something that eats from trees? Or alternately its mouth isn't attached to a head with a brain at all. Like an octopus with mouths at the end of its tentacles or something.

Either way, separating the upper jaw from a big brain case seems the most likely way for this to come about.

 

[L50LasPak]

Enjoy your next swim in the ocean.
(Creature is a goblin shark)

 

[soy_king]

I'm stuck on why an animal would have a moveable upper jaw in the first place. Whether you consider the upper jaw or the lower jaw to be the movable part is really just a question of which half of the mouth has the greater mass attached.

So to get what you want we're either looking at an animal that has the greater mass attached to the lower half of its face, i.e. brain case, eyes, etc are all at the bottom and the mouth is at the top of its head - perhaps it evolved in an evironment where it easts from exclusively above itself either an acquatic creature that eats from the water surface or something that eats from trees? Or alternately its mouth isn't attached to a head with a brain at all. Like an octopus with mouths at the end of its tentacles or something.

Either way, separating the upper jaw from a big brain case seems the most likely way for this to come about.

I think that's the big thing. It would probably have to be a creature that would eat in areas above itself, or have a squidlike beak with both jaws moving. Alternatively, I could think of a creature with a wide, shallow skull cavity with eyes on the side of its head, but it would probably still require to eat something above itself.

 

[Overly Serious]

 

[Gar For Archer]

Pretty sure birds can move their upper "jaws", Why are aliens always bilaterally symmetrical, what would an alien look like with quadrilateral symmetry look like?

The only real reference we have for radially-symmetric complex life would be starfish and their relatives, so that could be a starting point for the imagination.