Red Hill

Location: North-central Pennsylvania, USA, along the southern margin of the ancient continent, Euramerica.

Time Period: Late Devonian (specifically, the Famennian age, roughly 375-359 million years ago).


  • Early Tetrapods: Red Hill is famous for its fossils of some of the earliest limbed vertebrates, or tetrapods. Animals like Hynerpeton and Densignathus hunted in the shallow waters and would have ventured onto land for short periods.
  • Abundant Fish: Various species of fish, including lobe-finned fish (relatives of tetrapods) and armored placoderms, filled the waterways.
  • Invertebrates: The presence of trigonotarbids (arachnids) and myriapods (like millipedes) indicate a developing terrestrial arthropod ecosystem.

Dominant Vegetation:

  • Archaeopteris Forests: Giant, tree-like progymnosperms called Archaeopteris formed dense forests. These were among the world’s first true trees, reaching heights of up to 60 feet (18 meters).
  • Fern Glades: Rhacophyton, an extensive, shrubby fern, carpeted the forest floor and wetlands.
  • Lycopsid Wetlands: Scale-trees resembling giant club mosses added to the wetland diversity
  • Early Seed Plants: Patches of the earliest seed plants began to appear, taking advantage of disturbed areas such as those created by wildfires.


  • Floodplain environment: Red Hill was part of a vast river system and its floodplains. The landscape was dynamic, with changing river channels, swamps, and areas of occasional fire disturbance.
  • Lush vegetation: Despite periodic disruptions, the environment was predominantly green. Forests and wetlands thrived in this warm and humid climate.


Red Hill offers a remarkably vivid snapshot of a critical moment in Earth’s history:

  • The Rise of Forests: The Archaeopteris forests represented a major step in the evolution of terrestrial plants. These trees created new habitats and profoundly altered the landscape’s structure.
  • Terrestrialization: The fossils of early tetrapods and land-dwelling invertebrates highlight the ongoing transition of life from water to land.