This table contains atmospheric CO2-estimates based on stomata retrieved in the Messel fossil pit and published by Grein (2010) and Grein et al. (2011). The data is based on leaves retrieved from the Messel fossil pit (earliest Middle Eocene; 47.66 to 47.22 Ma). The leaves were microscopically analysed for their stomata density and which was then converted into atmospheric CO2 content (cf. Grein 2010, Grein et al., 2011 for details about the algorithm). The plant fossils were listed with their original outcrop depth which was marked down relative to marker beds. We projected the outcrop depth (m) onto the FB2001 drill core depth using the marker beds as reference horizons. The age (Ma) as well as mean, maximum and minimum of the CO2 estimates are reported as well as the respective plant species.