to the coastal margins, which created new terrestrial habitats, including the first forests. The decomposition of these newly diversified plants would have increased nutrient concentrations in the surrounding water, creating intense algae growth, which would cause eutrophic and anoxic conditions in the water. Ventastega and other early tetrapods would have been able to gulp air, giving them a significant fitness advantage by allowing them to explore the banks of the anoxic rivers and lakes where they were found. Stem and Crown Tetrapods have been found in both freshwater environments along with estuarine and lagoonal environments of varying salinity. However, the sedimentology of the Ketleri Formation, including sands interbedded with siltstones and clays, indicates that Ventastega was deposited in a low-tidal, near-shore environment in saline water. Geographic and Stratigraphic Range The Ketleri Formation or Ketleri Outcrop () is located in southwestern Latvia and northwestern Lithuania. Per Erik Ahlberg, Ervīns Lukševičs, and Oleg Lebedev collected Ventastega material both from the Ketleri locality where the original material was found, but also from another locality in the Ketleri formation, the Pavāri locality (. The Ketleri locality is at the Venta river near the former Ketleri hamlet, while the Pavāri locality is across the Ciecere river from the former Pavāri hamlet. The formation itself is composed of sand, sandstone, clay, and dolomitic marls, with the formation being 45m thick in Lithuania and 41-56m thick in Latvia. The formation is composed of three members, the lowermost Nīgrange member which has thick clayey carbonate deposits, the Pavāri member which consists of sand and sandstone with high levels of quartz, feldspar, and mica, and the upper Varkaļi member which is composed of fine feldspar-quartz sands and sandstones with high quantities of mica. The Pavāri member had a shallow erosional channel filled with well sorted sands indicating the presence of a stream in the Devonian that flowed in the channel from NNE to SSW, which is the characteristic direction of flow across the whole Ketleri formation. Sand particles filled in the erosional channel, and then were followed by slow, calm intertidal streams depositing poorly sorted silts and clays. See also Acanthostega Ichthyostega Devonian period Latvia Sarcopterygians Tetrapodamorpha Tetrapods References Stegocephalians Ichthyostegalia Prehistoric lobe-finned fish genera Late Devonian animals Devonian bony fish Devonian fish of Europe Transitional fossils Fossil taxa described in 1994 Natural history of Latvia Famennian genera