Vestige: A trace of something that is disappearing, or no longer exists.

So, it might go something like this. "The trace, or vestige, of the dinosaur proved its existence." See, it's not as hard trying to come up with a sentence. Think of it as similar to a trail, or evidence left behind.

Another example:

"For if the darkness and corruption leave

A vestige of the thoughts that once I had,

Better by far you should forget and smile

Than that you should remember and be sad."

(Christina Rossetti, 'Remember')

After the flood, there was no vestige of the town left.

A vestige is a sign of something, usually after another intervening event.