A little while ago on this site I mentioned Flavorwire's slideshow of modern and contemporary bicycle art (http://flavorwire.com/161998/the-unofficial-flavorwire-art-bike-survey), and noted a few omissions. However, I neglected one of the most significant contributions to the field: Picasso's "Bull's Head," from 1942, a blunt yet playful work with a powerful presence, consisting of a bicycle seat juxtaposed with handlebars to evoke the work's titular image (an impassive bull's head).
The first time I saw this work was several years ago in Paris, and Duchamp wasn't on my mind. (Picasso's work seems very much its own thing, even if made from found materials; furthermore the Spanish artist has a mythic reputation as a relentless original). But a recent review in the Wall Street Journal quite plausibly draws attention to the way in which the piece could be a reference to (and a riff on) the readymade...particularly the famous bicycle wheel mounted on a stool. Specifically, culture writer Eric Gibson claims that "Bull's Head" in fact not only comments on but transcends Duchamp's signature gesture.
This claim relies on Gibson's idea that "Duchamp's combinations are deliberately disjunctive. His bicycle wheel and stool are joined together precisely because they have nothing in common and, together, suggest nothing beyond themselves." Picasso, on the other hand, he argues, maintains a perfect balance on the edge between illusionism and reflexive materialism (i.e. while definitively inhabiting Duchampian territory, Picasso's "ready-made" nonetheless maintains a distinctly Picasso-like commitment to portraiture; the "Bull's Head" never dissolves totally into abstraction.)
This is a fine observation, but I also think Gibson is slightly underselling Duchamp: it's too much (or not quite enough) to say that "Bicycle Wheel" is "radically disjunctive." If you want radically disjunctive, take the Comte de Lautreamont's poetic image of the "chance meeting on a dissecting-table of a sewing-machine and an umbrella."
By contrast, there actually seems to me to be a strange affinity between the stool and the bicycle wheel, which Duchamp either discovered or, perhaps, created. A dissecting-table and sewing machine can only be combined meaningfully in language. Physically, however, by joining the bicycle wheel to the stool in the real world, Duchamp devised a non-functional assemblage, which is actually one thing, not two. It becomes its own icon, its own concept, and its own formal object, which can be reproduced with variations (and has been).
However, it is true that the Bicycle Wheel, unlike "the Bull's Head," is not representational. If Gibson had slightly amended his sentence to read "together, [the bicycle wheel and the stool] suggest nothing but itself," he would have been on the mark. But then he would have been alluding to the true ambiguity and slipperiness of Duchamp's creation, and might not have chosen to argue for Picasso's final supremacy in the realm of "found art."