There are massive volumes of dung/scat/poop being dumped on the ground. Why has no large-ish animal evolved that makes this their primary diet? There are dung beetles (small), but why no dung badgers, dung snakes, or dungaroos?
Is animal dung too nutrient poor to be of value to a large animal with higher energy requirements?
Do I have to wait until the question is actually answered to make a joke about Gloria Allred?
[Moderating]
According to the GQ rules, yes. 
Colibri
General Questions Moderator
This is probably it. Dung has already had most of its nutrients removed. Animals that are much smaller than the original consumer can wring enough remaining nutrients out of it, but species comparable in size cannot.
This said, some rather large animals do regularly consume dung, such as pigs and vultures, though it is not their primary diet. And they will get more by consuming the dung of omnivores and carnivores than herbivores.
I think that rabbits eat their own dung, as it has to be re-consumed for them to get the all the nutrients they need…
The OP specifies evolved. Gloria Allred was created ex nihilo by God, who hates us all.
That’s more akin to chewing a cud. We don’t say that ruminants “eat their vomit”. The pellets that rabbits poop out on the first go-round are not really the same as feces.
There’s dungarees…
I was taught this in ag class a half century ago. I don’t recall seeing any reference to rabbits eating their [whatever] until today.
:: glares suspiciously at jayjay, worries that the spirit of hovind has taken over his or her body ::
You have that exactly backwards. From Wikipedia:
[QUOTE=some anonymous group of Wikipedia editors whom I would ordinarily refuse to take seriously, but, hey, they support my position, and Rhymers are hypocrites]
Rabbits are herbivores who feed by grazing on grass, forbs, and leafy weeds. In consequence, their diet contains large amounts of cellulose, which is hard to digest. Rabbits solve this problem by passing two distinct types of feces: hard droppings and soft black viscous pellets, the latter of which are immediately eaten.** Rabbits reingest their own droppings (rather than chewing the cud as do cows and many other herbivores) to digest their food further and extract sufficient nutrients.**[10]
Rabbits graze heavily and rapidly for roughly the first half hour of a grazing period (usually in the late afternoon), followed by about half an hour of more selective feeding. In this time, the rabbit will also excrete many hard fecal pellets, being waste pellets that will not be reingested. If the environment is relatively non-threatening, the rabbit will remain outdoors for many hours, grazing at intervals. While out of the burrow, the rabbit will occasionally reingest its soft, partially digested pellets; this is rarely observed, since the pellets are reingested as they are produced. Reingestion is most common within the burrow between 8 o’clock in the morning and 5 o’clock in the evening, being carried out intermittently within that period.
[/QUOTE]
Follow the link in the article for less inherently-chancy verification.
Now if youwill excuse me I have an exorcism to schedule.
And dogs!
Sorry I have no further contribution, but I felt compelled to post here. 
You might have to look underwater.
Barbels are not exactly large (a couple of feet long), but they do eat hippo dung (supplemented with bugs, dead skin and the like).
A lot of bottom feeders like catfish will eat just about anything, and that can include the waste of other fish. (I keep a plecostomus and some coryboras in my fish tank to keep the bottom clean). Tilapia are often used by fish farmers in rotation or combination with other fish because the tilapia will eat the waste (but waste includes more than feces).
So I think you’ll find a lot more critters that are opportunistic and eat just about anything, with only a very few dedicated dung-eating specialists.
Large animals require a lot of nutrients, and dung is a shitty food supply.
Plants are probably easier, move available and contain more nutrients for larger animals that can reach them.
I think jayjay’s meaning in “first go-round” was not “chronologically earlier in time” as you evidently took it based on your cite, but rather "Following the path of consumed matter relative to the rabbit’s digestive system, the softer partially digested pellets produced on the food’s first pass through the system.
Hippo dung, bugs and dead skin. Man, that sounds just delightful! I’ll have to try that at my next dinner party, although it might be difficult to do the wine pairings.
I thought a lot of herbivores left most of the food undigested. That would seem to leave room for another animal with a more efficient digestive system, regardless of size.
Same point again. If flesh is more easily digested than grass, then the opposite could be true.
What they leave undigested is indigestible to most organisms: cellulose in the cell walls of plant tissues. With a few exceptions, cellulose can only be broken down by microorganisms. Specialized herbivores have gut compartments where symbiotic microorganisms live and break down cellulose, allowing the nutrients to be absorbed by the herbivore. What passes through the digestive tract doesn’t have much in the way of accessible nutrients.
Except that most carnivores have fast passage times through the gut, and not very efficient digestive systems. Carnivore dung in general has more nutrient content than that of herbivores.
Yeah, that occurred to me later. Also I think jayjay was talking about eating animals eating the dung of organisms other than themselves.