If you ever played Ecco the Dolphin through you'll notice at the end credits the graphics artist, Balogh Zsolt refers to himself as "the talent". It can't be argued he is not talented; he did the graphics for both Ecco the Dolphin, Ecco 2 as well as the models for Ecco, Defender of the Future. It can be argued some of his artwork is referenced, if not copied from other artists.
Zdenek Burian is a legendary artist who reconstructed prehistory with the help of Josef Augusta, a paleontologist. He's done over tens of thousands of drawings and paintings, which are featured in hundreds of books. He is one of the first few to do artwork based on extinct creatures and is a pioneer in his work. Many of the most recognized pictures of dinosaurs we've seen in books are likely to have been done by him. His artwork helped mold modern culture's interest in prehistory. Without his influence, paleontology would just be viewed as fossils and bones.
In the prehistory levels of Ecco the Dolphin you'll notice Zsolt referenced or even copied Burian's artwork. An example is the Pteranadon from Jurassic Beach, which appears to be taken right out of Burian's painting and transferred to the game data. Zsolt referenced surface plants, undersea plants and Orthocones from Burian's artwork matching the color down to the last detail.
What can be gathered from this evidence is Zsolt used references when designing the graphics. He also copied his reference artwork and used it for the games graphics.
The ultimate question is: why copy a reference without at least masking that it was copied? Was it because he was rushed to finish the graphics and figured no one would notice? Or did he do it as a tribute to Burian, a pioneer artist of creatures from prehistory? We don't have an answer to this, but it may have been both.
I would like to give a big thanks to Hauke of Caverns of Hope for his research that helped lay the groundwork for this article.
Sources: Prehistoric Debate - Caverns of Hope