When Ecco, Defender of the Future was first released as a preview at the 1999 E3 show, it received much publicity by gaming magazines and websites. The preview had elements that never made it into the final version of the game. The title screen featured fancy lettering on a plain white background with a small stamp at the bottom noting it was an "E3 Demo".
The life and air meter looked exactly like the meters from the original Genesis games. There are scenes in the game that show Ecco following another Dolphin with a second meter displayed for that character. The second meter could have been a life meter for that other character in which Ecco had to protect it from harm and ensure it got air. Another theory is that the meter was meant only for the development process ensuring the other character was taking a path where there was less danger and plenty of air.
Some preview screenshots have numbers in the upper right hand corner whose purpose is unknown. A first impression might seem like it was the amount of Vitalits gathered throughout the level, but a screenshot of Ecco following a clan dolphin disproves this theory.
Preview videos for Ecco, Defender of the Future had different music from the final release. A video for the level "Shrine of Controversy" used instruments and a musical style that was similar to the cinematic tracks by Atila Heger. If this mystery track is indeed Atila Hegers work it means Appaloosa scrapped his music for Tim Folins.
The level "Atlantis Lost" has whales and sharks swimming around that were probably removed to make the level simpler allowing the player more focus on the puzzles. "Master of Forgotten Skills" uses a different machine for lifting that's a lot more bulky then the machine in the final version. The text when communicating with other characters is in the Times Roman format that is a white transparent color. The final version has a cartoon styled font that's yellow in color.
The one element that makes the preview version of Ecco, Defender of the Future unique is the Foe Queen in the level "Chance of Reckoning". The body is the same as the final version but the head is shaped like a sharp double-edged pick. This is different from the final where the Queen's head is shaped much like a stingrays body and a mouth filled with extremely sharp teeth. Unfortunately there is no way to further analyze the preview since the only sources available are old screenshots and videos. If any new information becomes available this article will be expanded to feature the changes.