Even though Camaro, Cuda, Challenger, Mustang has been considered muscle cars they fall into the Pony Car classification. The term Pony Car was started back in the mid 60's when ford introduced the Mustang. True Muscle cars are usually large bodied two door hardtop with large cubic inch engines. The reason Camaros, Cudas, Challengers, and Mustangs are called muscle cars is infact because of the large cubic size engine that are in them. So I have to recant my original posting, pony cars are considerd muscle cars but not under the true definitions. Here is a good link below with a chart and classification.
Muscle Car definition - A muscle car, by the strictest definition, is an intermediate sized, performance oriented model, powered by a large V8 engine, at an affordable price. Most of these models were based on "regular" production vehicles. These vehicles are generally not considered muscle cars, even when equipped with large V8s. If there was a high performance version available, it gets the credit, and not the vehicle that it was based on.
Pony Car definition - In addition to fullsize and intermediate muscle cars, a number of smaller vehicles started appearing on the automotive performance scene. These new "pony cars" and compact cars are generally considered muscle cars only if they have the top of the line performance engines and options.
http://www.musclecarclub.com/musclecars ... tion.shtml