Judging by this odd-looking Z4 Coupe mule, Hans Lehmann, Our Man In The Trees, believes that BMW is readying a glass-roofed edition of its voluptuous little two-door.

We’re not sure what the deal with the rushed-looking high wing is, but judging by its roof covering, BMW could be working on a panoramic glass roof option as a cut-rate alternative to Porsche’s 911 Targa. That odd disc-shaped apparatus on the mule's lid could be some sort of antenna or assessment tool used in evaluating prototypes, but its function remains something of a mystery.

The fixed-head Z4 has been on sale for less than a year, so a second model (or option package) is certainly plausible.

+ Click here to read WINDING ROAD's full road test of the Z4 M Coupe on the roads of Portugal!