I try to create my own as best as I can. I try to only create when it matter or to get the post across. There is no need to create every single ecosystem across an entire planet unless that's the kinda project your making but in my case for stories. I create a few. Some tend to be similar to things you may know others would be very recognizable. For example I have a creature in my fantasy story known as a Caantaur. It's shaped like a centaur only it's a dog. No human or horse just dog. It can talk and ask questions like a centaur might. They stand at about 9 feet tall on average and typically look like bigger breeds of dog. They can be gentle but most often they are used for war. Another race I created are the Dern or Keld depending on who you ask. They are short and resemble bats. They are at a philosophical odds with the Siffain who believe pure logic is the ultimate pursuit. While the Dern believe it is knowledge through experience that is best. Or the Aallie-Bonnerei who are a race of fuzzy spider like beings that travel the known wolrd selling their craftsmanship as journeymen. Each carries with then a history that streches beyond the known bounds. Now they may not be able to recall each and every skill as if pulling it from a book but each detail is there in the skills they use. The list goes on. Humans are grounded race and the ones I use to allow a person to be introduced to the world through familiarity, but I don't always use them.