The “Palaeocast” podcast has a new episode.  The subject is “Insects”.  Insects are arthropods, the most diverse phylum in the animal kingdom.  Discussed is their fossil record – when and where they first appear.  There are fossil insects as far back as the Devonian, but they are very sparse.  However, by the late Carboniferous and the Permian periods, the fossil record contains a fair bit of variety.  A good example is the diversity in the Mazon Creek biota.