Wyverns

A wyvern is a type of dragon. Instead of a dragon's four limbs (arms and legs) and a pair of wings, they have a pair of wings as their sole forelimbs and a pair of legs, very much like a bird or a bat.

In Dota: Dragon's Blood
Although dragons in the animated series are mostly classified by their elemental and fundamental power/identity, some dragon types resemble wyverns. Lirrak and her water dragons, including the rogue Auroth, have a wyvern's features. Uldorak and his earth dragons are vestigial wyverns, because they have shortened (hence, useless) wings on their arms. The Air Dragons and their sovereign Aethrak are wyverns too.

Heroes
Auroth the is the most notable example of a wyvern.

Characters
Although most of the Crimson Wyvern's appearance is shown on the equipment forged from its remains, it is hard to tell if it is actually a wyvern, since we don't see the rest of its body, especially the wings which is most important in determining if it's a wyvern. Only its name tells us that it was one.

Karaul Silverwing looks like a wyvern, but the locals call it a dragon or an icewyrm,  not to mention that the lore of her stage calls it an icewyrm.

Relationships
Aghanim loves wyverns very much and has had romantic relationships with them in the past, his first course of action upon meeting them being seduction.