Today, oaks (Quercus) are widespread in Europe, Asia, North and Central America, the Caribbean and North Africa with around 400 species. With Colombia, they also just reach South America. This makes them one of the most important genera of trees in the northern hemisphere. In Germany, oaks are the most common deciduous trees after European beeches and are depicted as a national symbol on coins. In Germany, there are only three native species: the pedunculate oak Q. robur, the sessile oak Q. petraea and the downy oak Q. pubescens. The latter occurs in Central Europe in a few isolated locations that are characterized by warm temperatures, such as the Middle Rhine Valley, the Kaiserstuhl or the Saale Valley in Thuringia. It is mainly found in the northern Mediterranean region. Sessile oak and pedunculate oak, on the other hand, are widespread throughout Germany. The sessile oak just reaches Lithuania with the Memelland, while the pedunculate oak still reaches the European part of Kazakhstan in the east. In Central Europe, many oaks were found in the Eocene at Lake Messel: ten different taxa are known. There they grew together with plants such as tea family plants and mangoes in a paratropical rainforest. In the Eocene, oaks were also found in redwood forests at the ice-free North Pole due to the warmer climate.