A new McLaren prototype has been spotted testing in Southern Europe, likely to be the convertible version first reported on back in 2009 and which will eventually go head-to head with the formidable Ferrari 458 Spider.

On initial glance this black McLaren prototype looks like just another MP4-12C, but delve a little closer and you’ll quickly notice some peculiarities.

First and foremost is the makeshift cover over the rear window and engine bay, which almost certainly is hiding the new convertible roof. McLaren is expected to adopt an automated folding hard-top just like Ferrari did with the 458 Spider. However, where Ferrari relied on aluminum for its roof mechanism, McLaren may go with carbon fiber.

Another key difference are the side windows, which on the prototype in these latest spy shots appear to end where the doors end instead of tapering off towards the rear of the car like on the hard-top.

Otherwise, the McLaren convertible, which will most likely be called the MP4-12C Spider, will be virtually identical to its hard-top sibling, though there could be some slight engine and suspension changes to ensure maximum performance when the top is down.

Peak output from the car’s twin-turbocharged 3.8-liter V-8 engine should remain at 600 horsepower and 440 pound-feet of torque, however, and drive will still go to the rear wheels via a seven-speed dual clutch gearbox.

Look out for a reveal of the McLaren MP4-12C Spider late next year, with first sales to start just prior to the summer of 2013.

To check out the differences between this latest prototype and the MP4-12C hard-top that starts U.S. delivery in January, click here.