The first stamp, the well-known penny black, was issued in 1840. Not quite in prehistoric times, but a long time ago for sure.
The first commemmorative stamps were issued late in the 19-th century. Thus, thematic philately has been possible for over a century.
In comparison, the history of prehistoric life in philately is rather short. Just over 50 years, in fact. At that, the vast majority of relevant stamps has been issued during the past 20 years or so.
In this section, I have presented a number of milestones in the philatelic history of prehistoric life. Deliberately, I have left out the year of issue and the countries in my list at left, so that you can test your knowledge. Do you know 1) The year?, 2) The country?, and 3) The issue?
And who knows what is still to come? Self-adhesive, shaped stamps have already been issued by a number of countries, but so far not in the shape of dinosaurs. Holograms have also been popular.