On one of the Polacanthus cards, a golden Eoraptor is seen. This indicates that Eoraptor was an altered dinosaur and in result, it's skin color changed.
While originaly classified as an early theropod, it may also have been a very primitive sauropodomorph, could have existed before these two separate groups as an early saurischian, existed before the two main dinosaur branches split, or it may not be a true dinosaur (these last two are the least likely). In any case, there is no certainty.
Eoraptor and Pawpawsaurus are the only Secret dinosaurs not to appear in the anime. However, Pawpawsaurus has appeared in the anime as a Move Card dinosaur.
Out of the three Triassic dinosaurs in the arcade (the other 2 being Gojirasaurus and Liliensternus), Eoraptor is the only one that is not a Wind Dinosaur.
In the DS Game, Eoraptor can be changed into another dinosaur by teaching it an elemental move; however it changes back after the turn.
In the arcade game, it changes at random.
Eoraptor's ability to evolve into any dinosaur might be seen as a parallel to Eevee from Pokemon, as the latter can evolve into a multitude of forms each representing a main type.
However, the fact that the transformed dinosaurs bear Eoraptor's pattern might be a reference to another Pokemon character, Ditto, which has no abilities except for the one to transform into any other Pokemon character.