Although fossil plants are well documented from the Silurian Period of Earth history, spores from land plants are known from the preceding Ordovician and Cambrian Periods. However, it is not until the Mid-Devonian that fossil forests appear in the fossil record. The Gilboa Forest from New York State was first described in the 1920s and it became known as the earliest fossil forest. It has the same status today. Only one plant was known from this forest – the Eospermatopteris, or “ancient seed fern” – thought to grow up to 10 metres above the ground. They were not woody, but they had characters that that suggest affinities with tree ferns. The original analysis reinforced the evolutionary assumption that the earliest terrestrial systems were essentially simple. Recent research has changed all this.
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