title: Geochemistry. Gasping for air in Permian hard times.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Kerr
mesh_terms: D000531:Altitude; D000818:Animals; D001272:Atmosphere; D044822:Biodiversity; D005075:Biological Evolution; D003441:Crowding; D004777:Environment; D005580:Fossils; D010100:Oxygen / Q000032:analysis; D011156:Population Density; D012119:Respiration; D013995:Time; D014714:Vertebrates / Q000502:physiology*
chemical_list: D010100:Oxygen