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.
original colored Eoraptor seen on the bottom right