Well, I'd just like to say that after seeing the program, I wanted to make sure that these were possible. I looked up several books about natural history and evolution, that's when I realized that the creators expected to see a pattern, repeating evolutionary ages, the end of the program is the beginning of the second invertabrate age. Now there are plenty of analogies in the show ex. squibbon is to early primate as (??squid-human??) is to human, but regardless, here are the possibility factors for each creature on a scale from one to ten; ten being a slight possibility it won't evolve, one being a slight possibility it will, I've done my homework

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Shagrat: 7
Snowstalker: 6 (the teeth probably won't be that long)
Gannet Whale: 5 (if it comes on land it won't be as big)
Cryptile: 5 (how an Autrailian frilled lizard evolves in the Mediterranean doesn't fit)
Scrofa: 8 (it's just an elongated boar)
Gryken: 9 (it's a pine marten turned rock badger)
Babookari: 8 (it'll take a while for it to get the fish basket thing down)
Carakiller: 7 (the head plumage is far-fetched, and it's arms won't shrink if it uses that claw at all)
Grassland Rattleback: 7 (the porcupine-like spikes won't develop on a future paca in armodillo mode)
Desert Rattleback: 7 (if the first rattleback can occur, it would probably also adapt to desert life)
Spink: 6 (it isn't going to dig those tunnels unless it has better digging tools than spades)
Deathgleaner: 8 (if the top predator position isn't filled, bats will get big enough to fill it)
Reef Glider: 8 (some sea slugs can already swim, so given 100 million years, it could become a pretty good swimmer)
Ocean Phantom: 9 (a Man-of-War colony could do that and much more in 100 million years time)
Spindletroopers:9 (it won't be hard for sea spiders to develop harder mouthparts)
Lurkfish: 8 (an electric catfish could don on camouflage and increase it's electricity faster than 100 million years)
Swampus: 8 (I need to see how the oxygen reserves work with it first, but from what I know so far, it works)
Toraton: 8 (if these "conditions" that encouraged an increase in size are the same as with other animals that have grown large in the past, then it could get pretty big)
Roachcutter: 8 (It's almost like several birds of today, but evolved from Antarctic shore birds)
False Spitfire Bird: 8 (it is as possible as the spitfire bird, just like the king snake to the coral snake)
Spitfire Bird: 8 (I really need to find out more about the chemicals the bird takes from the flower)
Falconfly:6 (an 18-inch wasp?)
Spitfire Beetle:8 (the larvae of existing beetles mimic other creatures already)
Great Blue Windrunner: 9 (beleive it or not, it could develop a good manuverability system just from canards and feathered legs)
Silver Spider: 7 (although it's unlikely, if spiders developed a caste system, it would be really effective)
Poggle: 9 (a small rodent that steals from other animals? It's absurd!

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Terabyte:8 (termites could improve their workings painlessly and easily)
Garden Worms: 7 (convoluta worms already are symbiotic with algae)
Gloomworms: ? (I have to learn more about it)
Slickribbon: 7 (a worm would be able to become top predator, but three feet long is a little stretch as far as respiration goes)
Silverswimmers: 8 (if crustaceans developed neoteny, they could do just about anything)
Ocean Flish: 7
Rainbow Squid: 7 (if the squid could escape the two-year life cycle, it could get bigger, faster, stronger, and smarter)
Sharkopath: 8 (becoming a pack animal could be a real benefit)
Bumblebeetle: 7 (it really makes adulthood pointless)
Desert Hopper: 4 (if a snail could live being sucked up by a hypercane and thrown into the desert, it could become a hopping snail)
Death Bottle: 7 (a bog-dwelling carnivorous plant could colonize the desert)
Forest Flish: 8 (smaller body easier to carry)
Megasquid: 8 (why it lost it's beak is beyond me)
Slithersucker: 10 (a slime mold could easily become carnivorous)
Squibbon: 8 (a feeling of compassion could make cephalopods cease to be solitary)