Although the two cars will share most of their platform components, Alfa and Mazda assert that the two models will have unique styling, and each will have a powertrain from its own manufacturers' stable. The Mazda version, which will probably continue to be called MX-5, should use one of the company's new SkyActiv engine and transmission pairings.

The Alfa Romeo model will most likely be called the Spider, harking back to the lightweight Italian roadster first launched in the 1960s (pictured). Ironically, the original Mazda MX-5 was inspired by lightweight European sports cars like the Alfa Spider. The new Alfa Romeo will almost certainly be sold in the U.S.; the brand is expected to return to our market next year with the 4C sports coupe, and the Spider would be another key brand-building entry.

Alfa Romeo was once planning for its new Spider model to compete head-on with the Mazda MX-5. Co-developing the models will probably prevent any real sales contest, although it remains to be seen how much the cars' styling and engines differ.

The deal is a boon for Mazda, as it will help the company amortize the development cost of its low-volume MX-5 roadster with extra sales from the Alfa Romeo version. Mazda has been losing money for several years, and likely needs all the support it can get. Fiat, on the other hand, will have access to one of the world's most iconic roadster platforms for its next sports car. Better yet, working with Mazda - which will almost certainly sell its version stateside - means it should be fairly simple to federalize Alfa's model for U.S. consumption.

"By partnering with Mazda, we will be co-operating with the recognized leader in compact rear-drive vehicle architectures in order to deliver an exciting and stylish roadster in the Alfa Romeo tradition," Fiat CEO Sergio Marchionne said in a prepared statement.

The new roadsters are expected to go into production at Mazda's factory in Hiroshima, Japan, in 2015. Fiat and Mazda hope to finalize their cooperation by the end of this year, and say they are open to further partnerships on vehicles for Europe.

Source: Mazda