Winsor McCay was animation's first true innovator. His shorts, How a Mosquito Operates and Gertie The Dinosaur helped innovate many animation techniques. His highly detailed style combined with his heart and passion was passed down to future animation legends such as Tex Avery, Walt Disney, and Otto Messmer.
In 1947, a collection of unfinished/unreleased works by McCay were found to be in the possession of long time collaborator Irving Mendelsohn, who was given them years earlier by McCay's son Robert. Unfortunately, the films had not been stored well, and were somewhat deteriorated by the time they were rediscovered (with several portions of the reels having decomposed completely, accounting for the remaining lost scenes/productions). Amongst this bounty of unreleased (and partially destroyed) materials was a small amount of footage from McCay's (now well-known) production, The Centaurs, in the form of a 90-second fragment of animated centaurs wandering through a live-action-filmed forest. The fragment's animation was gorgeous, but made little sense in terms of story. For decades, historians were baffled as to what production the footage had been created for; then, in the mid-2000s, a small set of production notes of an unfinished Winsor McCay film titled The Centaurs surfaced. Given the animation style and title, the fragment has since been attributed to that production.
It is unclear as to why exactly the film was never completed. It was probably due to cost or its minor nudity (which was a big deal to audiences at the time). The production notes say the finished footage amounted to over 3 minutes, of which only the aforementioned 90 seconds survive. The film continues to intrigue audiences worldwide, keeping them wondering what might have been.