It's been a while since I've seen a fic like this, and I must admit that all these animals are highly amusing to see. However, I must point out the lack of scientific reasoning behind all this. Ignoring you're alternate dimension idea, the damage we humans have caused to our ecosystems would still leave animals such as wolves, polar bears, and even elephants in decline simply because they already were. But, ignoring that fact, some these animals just aren't plausible.

Otter Cat - The ancestor is a little strange, but given the climate and habitat, this is a very plausible animal, especially when one takes into consideration the already existing Fishing Cat of Asia.

Tree Banshees - Crocodiles with wings? As terrifying and cool as that would be, it's just not possible. What might be more plausible is that crocodiles evolved to have their legs directly under them and took the niche of lions and other apex predators that may or may not be extinct, similar to how their ancestors the archosaurs (if I remember correctly) were before their extinction or even become more aquatic like mosasaurs and other marine reptiles. After all, evolution brings the occasional repeat into the mix. But having them glide from trees with their current size? They're just too big, not to mention it was never even in their genes to develop membranes/wings in the first place.

Mangrove Darter - One of the more plausible animals on this list, especially when one considers the existence of pudús, the world's smallest deer, and klipspringers, the world's smallest antelope. Either way, well done on this one.

Crimson Shrimp Eaters - This one presents some problems, mostly because a lack of flight often means a lack of predators and a design for specialization often requires an isolated pocket of the world to live where there is no competition from other species for such a niche. The ostrich, despite having predators such as lions and cheetahs, still lost its flight and yet evolved powerful legs to run away at high speeds; in other words, this creature is utterly defenseless as a dodo and the only thing going for it is its high breeding speed (which is actually quite realistic. Well done on that).

Short-trunk Swamp Hog - Ignoring the fact that elephants might very well be extinct at this place in time (how far into the future are the Serengeti Swamps anyway? 100 million years or so?), this one is well done as well. A lack of space and competition for food would definitely allow animals that were once the biggest land mammals on earth to be no bigger than a horse. Not to mention it's happened in more primitive version of elephants leading up to their modern day relatives.

Rainbow Serpent - The coloring is a bit unusual, but the ability to blend into ones surroundings and sneak up on prey is invaluable. Not to mention the fact that monstrous snakes, such as the Titanboa, were more than capable of swallowing crocodiles whole (and those crocodiles dwarfed a man) back around the Eocene and Pliocene era.

Coastal Zebra - Sadly, this one just seems a tad ridiculous than anything else, but I can't argue with how plausible it is. Assuming that zebras survived into the future, they might assume various forms that feed off of different types of vegetation and occupy different habitats like the two species of Rattlebacks in the North American Desert and the Amazon Grasslands.

Serengeti Reef Dolphin - First off, if this species is descended from orcas, that usually means their ancestors are extinct or very close to it. Either way, this is definitely plausible in the scientific sense should Cetaceans survive into the future time era.

Great Mangrove Turtle - This is perhaps the most realistic animal on this list. Not only are modern day turtles and tortoises famous for living for decades and growing to enormous sizes, but we have the mighty Toratons, the largest animals to ever walk the earth, some 100 million years in the future (or now, when this chapter takes place. In which, sadly, a great deal of these animals wouldn't exist considering the fact that all mammals but the Poggle are extinct. But I'm ignoring this fact!), so this old geezer is more than capable of becoming a reality; plus, turtles survived the extinction of the dinosaurs when the dinosaurs didn't, so what's a couple more million years?

Beach Racer - I see these things as something close to those sand pipers and other seabirds. And while the ancestor is somewhat odd, the evolution certainly isn't; with all these animals competing for space, food, and resources, size really does matter and getting small does have its advantages. More places to hide, less need for food, and small animals are usually more agile and quick than, say, animals the size of gazelles or cheetahs.

Grove Horn Cattle - This one definitely fits the book. Seeing as how live stock, especially cattle, are one of the main problems to African wildlife, its not that big of a surprise to see that cattle make their way into the future and push out the rest of the competition, such as wildebeest, zebras, and antelope (in their previous forms). And considering how successful cattle are thanks to humans, they have the potential to run riot and assume various forms and niches, growing bigger or taller, faster or smaller, and even have the potential to fill the niches of some of Africa's most iconic animals.

Pygmy Branch Baboon - We already have tarsiers and pygmy marmosets, so this one doesn't have much of an issue.

River Mamba - An herbivorous snake . . . sure, given enough time, it's more than likely to happen, especially with the way you created it!

All in all, the majority of these animals and creatures you've created are absolutely phenomenal and I commend you for getting the scientific accuracy quite close, especially with how off kilter it seems (in my opinion, which shouldn't matter to you).

If I may submit a potential future creature? This little guy evolved from the piranha fish of South America, having been forced to move into more brackish and salty water due to rising sea levels; once accustomed to their new ocean homes, they quickly spiraled out of control and evolved into top predators that even put sharks (which are still existing in their current form. They haven't changed in 100 million years, and they certainly aren't going to do it now), turning into Xiphactinus-like ocean predators that feast upon anything they can get their mouths around and cough up anything their strong stomachs can't digest, such as shells, allowing them to spread throughout all the oceans.

I give you the fearsome, predatory Vicejaw.

Hey are you going to make this into a story

To Dadog:
Thanks for explaining everything up for me! Now I know that the Short Trunk Swamp Hog superficially resembled extinct gomphotheres and as for the Grove Horn Cattle, it possible they can evolved prehensile tongue like the giraffes in order to pick off berries of their 'mobile gardens'.

To Avian-
Otter Cats: They don't really need defenses. They're extremely fast in reeves, where they live. The only predators they have are rainbow serpents.
Tree Banshees: yes, they do indeed glide.
Short Trunked Swamp Hog: they look more like the Phiomia from ARK:Survival Evolved.
Rainbow serpent: I guess I lied. Rainbow Serpents cane actually go on land but prefer to stay in the water, where their more versatile.
Beach Racers: they actually have the most predators of all the creatures in the swamp since they're relatively easy to catch, always staying on the beach instead of winding through the mangrove roots like the antelope, zebras, and monkeys.
Grove Horns: even if there were berries growing on the horns of the cattle, how old they reach them? Also, don't bet against a Rainbow Serpent. They can kill pretty much anything in the swamp the want.
River Mamba: The self-defensive venom actually only works on tree banshees. Rainbow serpents have developed an immunity and other predators don't really bother with them.

Is this story still ongoing? Please say yes! If it is, I hope you will be glad to accept my first ideas of future animals:
Predactoor-From Australia. This is the first ever carnivorous and predatory parrot and cockatoo. They were descended from Kea which they migrated from New Zealand to Australia due to both landmass collided with each other. They had evolved into raptor like by having sharp claws and beaks, bigger wings and prey on kangaroos and koalas which were still exist.
Name origin: Predator cockatoo

Wow, you really defined the pure creativity completely and I truly loving it! Nice job for creating all these amazing animals from the future. I love how you defined all their descriptions of their biology in boundless bizarre way and also sound realistic at the same time. Also, good job for making the biological census of the species populations of the Serengeti Swamp but I think it will be more appropriate for the invertebrates species to be more than millions in number. Okay time for me to tell what I think about them!

Otter cat-I personally think this will be my top favorite of the future animals in the Serengeti Swamp. I mean who wouldn't love graceful cat that love to swim? Aquatic feline were especially my favorite idea of future animals that might evolved someday. Good job for incorporating the social behavior which is reminiscent of the African lions once rule the former Seregenti. I love how they there were descended from Serval which is very cool to look at! Hope they will quickly evolved to develop better defences against predators of this menacing swamp.

Tree Banshee-arboreal crocodiles that had developed wing membranes is definitely creepy but cool! Not to mentioned with their intelligence defintiely add up the danger level. While I'm a bit confused here while I can see they can still swim in ray-like manner with their 'wings' but they do glide in the air right? If they do, I would never ventured into that swamp ever and this might had been total living nightmare among the residents here. Simple to say, this is one freaking cool predator!

Mangrove Darter-these diminutive antelopes were especially interesting animals as well. They must had lot of hard time striving in this lush swamp full of dangers lurking to strike their life in any seconds. Having them evolved from Black Wildebeest are good choice indeed!

Crimson Shrimp Eaters-as for these future flamingos, wow, I never thought of imagining a flock of purple flamingos despite their names. So, these feathered friends had somehow end up becoming like Kori Bustard having hard time flying thanks to their now devolved wings. Nevertheless, they must be pretty bird to look at.

Short Trunk Swamp Hog-Yeah you're right, I initially assumed it must be some sort of elephant descendant and I was right. I envisioned them to be a mixture of Deinotherium and Stegodon if I pictured it correctly.

Rainbow Serpent-alongside Otter Cat, this is my second top favorite Serengeti Swamp animals! I love how you choose the legend of mythical snake of the same name from Australian Aborigine. Definitely terrifyingly awesome as ever! This is also maybe one of the most beautiful snake I'll ever imagine with their rainbow colour but beneath it lies deadly demeanor. No doubt this brainy monster snake deserved to be the king of the sea and swamp alike. I'm glad this mighty serpent can't go on land!

Coastal Zebra-another cool and interesting species. I love how they still retained their speedy abilites in order to outrun potential predators in the swamp. Also nice colouration you paint them but I would like it better if they were black with white stripes. I hope the Tree Banshees will think twice before recieving nasty gash on their gut from their hooves!

Serengeti Reef Dolphin-I totally love these adorable cetaceans! :) Who know these dolphin were once descended from vicious Killer Whales? Nature are always full of mysteries! And yeah too bad they always gang up to harass poor little kitty in the sea. I hope the snake will teach them a lesson.

Giant Mangrove Turtle-it appear that the Archelon or Prostoega make a comeback. Yep, growing super huge as ever. Interesting to see these magnificent gigantic turtles always come to sunbath at the shoreline unlike any other sea turtles which only come to lay eggs. I felt bad for the otter cat as well and hopefully they will take frequent swimming lessons before take a catnap on its shell. I'm glad its ancestor, green sea turtle still exist and common as well.

Beach Racer-the 'Beep Beep' of this swamp and I wouldn't surprise if they were evolved from the Ostriches. With abundant food and unimaginable speed, this bird have nothing to worry about every day in this hostile swamp.

Grove Horn Cattle-this is one extraordinary cattle indeed and the idea of having vegetations growing on its horn were definitely interesting concept! With their magnificent yet deadly horn, I doubt very much the Rainbow Serpent can gobble it up. I always imagined future animals such as deer and cattle having garden growing of their horn! The mating ritual were also interesting as well and seriously the male fight with the females!? The ladies must be seriously hard to get. You should also add more like for example the vine growing berries that provide extra food to the cattles.

Pygmy Branch Baboon-when yo mentioned grazing monkeys, I first thought they will be some sort like a baboons on a hooves XD Just kidding, I certainly love these cute little primates. Yep, safety in number if first thing in mind when it come to face to face with merciless king of the swamp.

River Mamba-last but not least, this is arguably the most unlikeliest snake and animal that will somehow evolved in the future. Vegetarian snake!? Definitely the most friendliest snake I would love to have at home if it weren't for their venom. Funny to think how ironic that they were actually descended from terrifying venomous black mamba.

Forget when I said I'm busy with my assignments, I think stealing a quarter of time wouldn't hurt. As for this future habitat that used to be vast Serengeti now end up flooded to become a huge swamp was very interesting indeed. It seem to based on Bengal Swamp from the original series I suppose.
Nice choice for turning one in Africa! I'm especially glad some African animals like lion, giraffe, hyena and rhinoceros didn't end up wiped out to extinction and hopefully they will evolve into something even cooler. Speaking of evolved species, time for me to tell what's my opinion about the future residents here.

So...this is your latest story, eh? Hmmm...what should I say about this? Absolutely fantastical! Wow, you truly bring me back to when I used to love watch Future Is Wild series. I'm sure you can unleashes all your amazing creativity to create brand new world full of bizarre and uncanny creatures that we never think they would exist ;) About the new habitats and species you made, I'm afraid my assignment still confine me but I promise I will give you my thought about all of them. Keep up the good work!