Why do we show an insect even though we have no fossils?

Painting of a katydid insect being eaten by the small mammal, Arundelconodon.

Katydid. Click to zoom.

We know from fossils preserved in other locations that many insects, including katydids, were widespread in the Cretaceous and would have played important roles in this ecosystem. The Early Cretaceous rocks of the Crato Formation in northwestern Brazil, which are about the same age as the Arundel deposits, contain well-preserved fossil katydids as well as many other insect fossils. Those fossils give us a good sense of what the local insects would have looked like.