Arriving from planet what-the-hell at the Paris Motor Show on Thursday was the staggering Sesto Elemento concept car, which illustrates, says the Sant'Agata, Italy-based manufacturer, the future of materials science and lightweighting in extreme sports cars.

Built almost entirely of carbon-fiber and carbon-fiber reinforced plastic (CFRP), the Sesto has a reported curb weight of a mere 2,202 pounds, which is not a lot of mass compared to the 570-hp V10 Lambo purports to have installed in the thing. The company says the car...