Werewolves

Background
Real Werewolves are mentioned in the final chapters of Breaking Dawn as Caius shows a great fear of the La Push 'Werewolves' as he believes them to be real Werewolves. However, near the end of the confrontation between the Cullens and their allies and the Volturi, Aro reveals that the La Push 'werewolves' are in fact shape-shifters, and that the fact they took the forms of wolves was mere co-incidence. Due to his extreme hatred/fear of Werewolves, Caius has had them hunted to near-extinction.

Appearance
Because the Volturi (especially Caius) originally thought the La Push Shape-Shifters were Werewolves, it is assumed that real Werewolves are very similar, if not the same in appearance to the La push Shape-Shifters.

Abilities
Because Werewolves are very similar to the La Push Shape-Shifters, it is assumed that they possess the same super-strength, super-speed and possibly regenration abilities of the Shape-Shifters. However, because they are not in control of themselves when they are in their Werewolf form and because they rarely form packs, if at all, they probably cannot communicate with one another through telepathy. Also their version of phasing, is when they transform at full moon.

Trivia

 * Caius' extreme hatred/fear of Werewolves stems from when he almost lost a fight against one hundreds of years ago.
 * Real Werewolves are also known as Children of the Night.
 * James and Victoria hunted a Werewolf in Europe as it is mentioned by Edward when he reads Victoria's thoughts after she sees Seth Clearwater before they fight in the final chapters of Eclipse.
 * Silver bullets do not harm them as it was a myth created by humans so they could believe they had a fighting chance.