Either tense is possible, lingkky. I probably see the simple past used more often in talk about dinosaurs. However, the present is possible, particularly in remarks about features found in skeletons and other fossils.
I think that it would help everyone if we used the past tense here.
I know that there's an argument for the present in matters of eternal scientific truths, but let's not make life any more complicated than necessary. There are already fundamentalists who don't even recognise dinosaurs!