All members of the animal kingdom have some basic things in common: They’re eukaryotic, multicellular, heterotrophic, and motile (at some stage). However, some animals have the distinction of being the only animal of their kind to exhibit a certain characteristic. Here are some examples!
Pangolins are the only fully-scaled mammal. 
Ostriches are the only two-legged animals with four kneecaps (two per leg). 
Humans are the only animal with a chin. 
Swamp wallabies are the only animal that is (almost) always pregnant, thanks to its two uteruses. 
Henneguya salminicola, a salmon parasite, is the only animal that doesn’t need oxygen to survive. 
While it is NOT true that elephants are the only mammal that can’t jump (sloths, hippos, and rhinos can’t either), they ARE the only animals that can’t have all four feet off the ground at the same time (and hence can’t really “run” in the traditional sense). 
Kangaroos are the only mammal that can’t walk (well, hop) backwards. 
Wombats are the only animal to produce cube-shaped scat.
There are probably more, but, not surprisingly, the Internet is full of myths and misinformation on this topic, and I got tired of researching things like, “Are hummingbirds the only bird that can’t walk?” and “Do bullfrogs sleep?” But feel free to share unique animals facts of your own, and do not attempt to poop cubes just to show up the wombat.
Have a great day, Avocados!
