What adaptations of the mouth or digestive tract would help a creature to collect and consume mucosae (mucus membranes) that grow over the ground? The membranes have normal proportions and properties, but are about 10cm thick, and are sturdy enough to be walked on by most animals. These mucosae and creatures live on Mars, which, in addition to being covered in mucosae and bearing life, also has a thicker atmosphere than reality (though still thinner than Earth), with a similar proportion of oxygen to Earth. It also has a stronger magnetic field to deflect solar winds. The creature is similar in size to a cow, and is mammalian. It also should not eat anything besides the ground-mucosae
Behold the shovel-tusk gomphotheres!
The gomps are on top. I did not crop out the rhinos because they are my totem animals.
Gomphotheres were ancient mammals related to elephants. Your mucosa feeders are built similarly. The sharp forward facing mandibular shovel tusks cut through the mat, and the large size and traction of the gomphothere allows them to push along, cutting the mucosa and plowing a strip directly into their mouths. Groups of these feeding would leave long denuded parallel lines in the mucosa mat. If any of Dutch's snail things are in the way they will eat those too, and chuckle.
Snails feed on leaves, algae and the like. Leaves apart their food grows on hard substrate, and they have a mouth adapted to feed while they are literally moving on it:
In the pic above you see the snail from below while moving on a glass.
Your creatures can do the same: while moving on the mucosae, their mouth is in close contact with it and chews it away.
Nothing special, really.
What you're describing is essentially a static prey animal made of something that resembles gum tissue: its a mucous membrane, and it's pretty tough.
Your predator is pretty large in comparison to the mucoid creatures. All it really needs is the right combination of standard mammalian predatory tool kit of flesh rending anatomy.
I'd suggest ordinary claws for gripping.
Dentition, I think will be a hybrid of what we'd consider "grazing" and "hunting" teeth types. In specific, I suspect that, unlike Earth predators, Mars predators will have larger & stronger incisors along with shorter though still powerful canines & perhaps even carnassials.
Lastly, I'd suggest a spiny feline tongue, which is pretty good at rasping and tearing at flesh.
Really all they have to do is scrape the gum tissue off of its substrate and enjoy an easy meal!
Other sequellae of this model that would strongly differentiate it from its terrestrial cousins might include a relatively weak & dumb predator. It doesn't really have to move very fast to catch its stationary prey. It doesn't really have to outthink anything.