In 2004, Jennifer McElwain proposed a method for calculating paleoaltimetry using fossil cuticles and their record of stomatal density as a proxy for CO2 partial pressure (pCO2). This technique utilises the inverse correlation between stomatal density and pCO2 to calculate paleo-elevation to within an average error range of ±300m, compared to ±400m in the comparable basaltic lava method. The technique is not universally applicable, however, as there are many types of plants that are not CO2 sensitive and are thus incompatible with the pCO2 paleoaltimeter.
