Leaves? Leaves?! I know these are small, but I don't think there are any leaves even close to looking like a female Fourmaw Sauceback. Antarctic fur seals do try to mate with king penguins, and repeatedly, but at least they're warm-blooded and moving.
Now, Fuzzpile leaves might be fuzzy, but I doubt they're a similar shape.

I wonder how long it will take until a flora creates leaves that tricks them into mating with it, like bees and bee orchids.

I recommend not using "shrewbacks", even though they are more like shrews than most "shrews", simply because "shrewback" suggests an association with Sagan 4's "shrews".

"ectotherm (hiberation)" looks odd in its uncapitalized form.

Their ancestor would attempt to mate with literally anything. The purpose of useless mating in this species is to make them not keep trying to fight other males when they already lost or there's no females available, though they're probably not aware that that's what they're doing.

Everyone has been calling descendants of the shrew sauceback "shrewbacks", so it's the common name for the group now.

Approval Checklist:
Art:
Art Present?: Y
Art clear?: Y
Gen number?: Y
All limbs shown?: Y
Reasonably Comparable to Ancestor?: Y
Realistic additions?: Y

Name: Fourmaw Sauceback
Binomial Taxonomic Name?: (Quattuorgnathus megagingivus)
Creator?: Disgustedorite

Ancestor: Logworm Sauceback
Listed?: Y
What changes?:
  • External?: Gum-prongs with teeth, slightly bigger, proportions are modified
  • Internal?: Longer life as an adult, capable of eating, EATS A HELL OF A LOT MORE THINGS THAN ITS ANCESTOR
  • Behavioral/Mental?: More complex mating rituals compared to its ancestor.
Are Changes Realistic?: Y
New Genus Needed?: (If yes, list why) Already taken care of

Habitat: Barlowe Temperate Woodland, Barlowe Temperate Rainforest
Type?: 1/3
Flavor?: 2/3
Connected?: Y
Wildcard?: NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO

Size: 4 cm
Same as Ancestor?: No, but only bigger by one measly centimeter so it's within range
Within range?: See above
Exception?:

Support: Endoskeleton (Chitin)
Same as Ancestor?: Y
Reasonable changes (if any)?:
Other?:

Diet: Adult: Omnivore (Logworm Sauceback larvae, Teacup Sauceback larvae, Vermees, occasional cannibal of larvae); Juvenile: Detritivore (Wood, chitin)
Same as Ancestor?: Not exactly
Transition Rule?: Y
Reasonable changes (if any)?: Normally, I'd object the surprising leap in dietary requirements, but the fact that it's only one generation recent means the leap doesn't really matter.

Respiration: Active (Microlungs)
Same as Ancestor?: Y
Does It Fit Habitat?: Y
Reasonable changes (if any)?: N/A
Other?:

Thermoregulation: Adult: Endotherm (Feathers), Ectotherm (Hibernation) over winter; Larvae: Ectotherm
Same as Ancestor?: Mostly
Does It Fit Habitat?: Y
Reasonable changes (if any)?:
Other?: Wouldn't that make the adults mesothermic, or is that really what happens with hibernating mammals?

Reproduction: Sexual (Male and Female, Eggs and Larvae)
Same as Ancestor?: Y
Does It Fit Habitat?: Y
Reasonable changes (if any)?:
Other?:

Description:
Length?: Reasonably sufficient!
Capitalized correctly?: Y
Replace/Split from ancestor?: Split
Other?:

Status: Approved

That's what happens when animals hibernate yes

Altered to full green.