As the title of this post states, rhinoceroses have no knees. They are also an odd-toed ungulate, which means they have hooves that have an odd number of toes.
Rhinos are know for their large size, weighing up to a ton. But for being as big as they are, they have a relatively small brain. Rhinos are also characterized by their horns (depending on the species they have one or two horns). Unfortunately, their horns, which can be sold for medicinal purposes or as hunting trophies on the black market, make them a prime target for poaches. Three of the five species of rhinos are now endangered.