Reptiles:
Bearded Dragon Humans- Need high temperatures, cannot regulate own body temperature (this applies to all reptile-humans and amphibian-humans). Eats a diet of giant insects and plant matter. Look up bearded dragon physical characteristics and apply some to character, all will have scales they can shed. Heights can range from 7-9 feet tall at adulthood. Need rocky desert environments.
Gargoyle Gecko Humans- Needs mid-range temperatures, cannot regulate own body temperature. Softer scales than a BD-Human, and shorter too, height ranging from 3-5 feet in adulthood. Will have scales they can shed. Eats a diet of largely fruit and the occasional insect. Look up gargoyle gecko characteristics and apply as needed. Rainforest environment
Plains Hognose Snake Humans: Long necks and hognose-snakelike faces, bottom half of body is just snake tail. They're like if centaurworld had snake-taurs. Do they? I haven't watched enough of the show to know. Eat a diet of giant rodents, toads, and frogs. Heights in the normal human range of 4-6 feet tall. Burrowers that do well in mid-range tho warm environments like the grasslands of North America. Females are larger than males.
Arachnids:
Brazlian Whiteknee Tarantula Humans- Rainforest tarantulas, need a rainforest environment. Females are larger than males, eat mainly insects, 6-8 feet tall. Can molt off exoskeleton and grow new one. Powerful venom for their size, compared to their wild counterparts whose venom is weaker. Look up appearance and other such things to get a feel for this species, I admit I know less about it than the others.
Mammals:
Cow Humans- Just. Do I have to explain this one? Y'all know about cows. Just give the appropriate physical and environmental characteristics and we'll be fine, do NOT ask me about udders. That shit is up to you.
Lion Humans- live in grasslands, savannas, and shrublands according to wikipedia. Otherwise, I leave the rest up to you, lions are carnivores and are utterly terrifying up close. 8-10 feet tall, the tallest here.
Guinea Pig Humans- eat a diet of purely greens and hay/grass, herbivores. Live in "moist savannas to thorn forest and scrub desert" in areas of South America. Height- 2-4 feet tall, the shortest.
Birds:
Merlin Humans- Merlin are a small species of falcon, that primarily take down smaller birds. Thus, the human version takes down the giant versions of these small birds. They have a decent wingspan, enough to keep them in flight for a while as well as be quite agile. 5-7 feet tall. Carnivores, will eat mostly smaller birds but also sometimes bats and insects etc. Idk I just like Merlins, look them up they're pretty birds. Here's a link if you need more info on their species: https://www.allaboutbirds.org/guide/Merlin/lifehistory
Crow Humans- y'all know about crows. Omnivores that eat literally everything, from carrots to carrion. 4-6 feet tall.
Cockatiel Humans- Parrots hailing from Australia, and live primarily in that environment. They are herbivores, will eat seeds, nuts, fruit and vegetables, grains, etc. C-Humans are around 3-5 feet tall and can stay in the air with their wings for a while. Look up cockatiels for more info because I'm getting too tired to type at this point as executive dysfunction is indeed a bitch.
The reason I'm not including fish, amphibians, or insects is because I'm tired and would rather leave it up to y'all to create critters for those. Thus, I'll leave the categories open below to add as you wish, just ask me first.
Fish:
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Amphibians:
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Insects:
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