A timeline for terrestrialization: consequences for the carbon cycle in the Palaeozoic.
The geochemical carbon cycle is strongly influenced by life on land, principally through the effects of carbon sequestration and the weathering of calcium and magnesium silicates in surface rocks and soils. Knowing the time of origin of land plants and animals and also of key organ systems (e.g. plant vasculature, roots, wood) is crucial to understand the development of the carbon cycle and its effects on other Earth systems. Here, we compare evidence from fossils with calibrated molecular phylogenetic trees (timetrees) of living plants and arthropods. We show that different perspectives conflict in terms of the relative timing of events, the organisms involved and the pattern of diversification of various groups. Focusing on the fossil record, we highlight a number of key biases that underpin some of these conflicts, the most pervasive and far-reaching being the extent and nature of major facies changes in the rock record. These effects probably mask an earlier origin of life on land than is evident from certain classes of fossil data. If correct, this would have major implications in understanding the carbon cycle during the Early Palaeozoic.
Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK. p.kenrick@nhm.ac.uk
Paul
P
Kenrick
Charles H
CH
Wellman
Harald
H
Schneider
Gregory D
GD
Edgecombe
D000818:Animals; D059001:Aquatic Organisms / Q000737:chemistry / Q000145:classification / Q000502:physiology; D001181:Arthropods / Q000737:chemistry* / Q000145:classification / Q000235:genetics / Q000502:physiology; D057486:Carbon Cycle; D018744:DNA, Plant; D017753:Ecosystem; D019669:Embryophyta / Q000737:chemistry* / Q000145:classification / Q000235:genetics / Q000502:physiology; D019143:Evolution, Molecular; D005580:Fossils; D017344:Genes, Insect; D000069497:Origin of Life; D010802:Phylogeny; D012987:Soil / Q000737:chemistry; D013170:Spores / Q000737:chemistry / Q000502:physiology; D013997:Time Factors
D018744:DNA, Plant; D012987:Soil