An early development mule for the new range-topping Audi Q8 crossover has been spied during testing in Spain.

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As we can see in this photo set, the Q8 will feature a wider track than the Q7, with which it will share its platform.

According to AutoExpress, the Q7 and Q8 will have almost identical wheelbases, but the Q8 will only be able to seat a maximum of five people thanks to its shorter rear overhang.

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While the Q8's roof will sit around 70mm closer to the ground, it will reportedly miss out on a heavily raked "coupe-like" tailgate. These altered dimensions hint that the Q8 will have a more sporting focus than its platform mate.

In addition to an all new body with sportier proportions, the Q8 is said to feature an octagonal version of Audi's single-frame grille, as well as some styling elements from the next-generation A8 sedan.

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Under the bonnet, the Q8 will likely use some of the drivetrains featured in the current Q7 range, including the SQ7's 320kW/900Nm 4.0-litre V8 diesel with two turbos and an electric compressor.

Also expected to feature in the Q8's lineup is the new Porsche-developed 4.0-litre twin-turbo V8. The engine, which made its debut along with the second-generation Panamera, generates 404kW of power at 5750rpm, and 770Nm of torque between 1960 and 4500rpm.

The Q8 is expected to make its debut in late 2017, with sales beginning globally some time in 2018.