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Biochronology is the dating of biological events using biostratigraphic or palaeontological methods.

Dating systems[edit]

A land-mammal age (LMA) is a time interval characterized by distinctive mammal fossil assemblages. The concept was introduced in 1941 by Wood et al[1] to classify the Tertiary period for western North America. By 1983, LVAs were introduced for Cenozoic era for most continents. For Mesozoic era, LVAs are assigned only to Late Cretaceous in western North America.[2]

A land-vertebrate age (LVA) is a concept similar to LMA, based on vertebrates, a wider class, which also includes turtles, dinosaurs, etc. [2]

Since in this context the term "age" may be misleading, since LVA and LMA are not stratigraphic ages, in 1993 Spencer G. Lucas siggested the term land-vertebrate faunachron. The author explains the choice of term by the fact that aggregations of mammal fossils within sedimentary strata have been commonly referred to as "local fauna" by vertebrate palaeontologists.[2]


  1. ^ Wood, H.E.II, Chaney, R. W., Clark, J., Colbert, E. H., Jepsen, G. L., Reeside, J. B., and Stock, C., "Nomenclature and correlation of the North American continental Tertiary", Geological Society of America Bulletin, January 1, 1941, v. 52, no. 1, p. 1-48
  2. ^ a b c Encyclopedia of Dynosaurs, "Land-Mammal Ages"

External links[edit]