Rare's canceled game Dinosaur Planet, which would eventually be overhauled and released as Star Fox Adventures for GameCube, has leaked in its original state online. The game was planned for the Nintendo 64, and much of its DNA still exists in Star Fox Adventures--hence that game's major differences from the rest of the series.

Shared by the Nintendo historian Forest of Illusion on Twitter and spotted by VGC, Dinosaur Planet is fully playable via this leaked version, though the account said it won't run perfectly on emulators. The build appears to be from after Nintendo had already decided to mix in elements of Star Fox, as you can see Fox McCloud himself in one of the screenshots. The game was still called Dinosaur Planet at this point, however.

It's peculiar to see how Fox had been seemingly shoehorned into the game at this point, wearing his usual outfit but with a sword on his back. He ended up using a staff as his main weapon in Star Fox Adventures but went back to his blaster and other sci-fi technology for Star Fox Assault a few years later.