Skeletochronology is a technique used to determine the individual, chronological ages of vertebrates by counting lines of arrested, annual growth, also known as LAGs, within skeletal tissues.
[4] Amphibians and Reptiles are commonly aged determined, using this method, because they undergo discrete annual activity cycles such as winter dormancy or metamorphosis, however it cannot be used for all species of bony animals.
[5] The different environmental and biological factors that influence bone growth and development can become a barrier in determining age as a complete record may be rare.
[5] The analysis is frequently performed on dry bones with the additional application of alcohol or congelated preservation if needed, as the aim is to enhance the optical contrast which results from different physical properties to light.
[4] The continuous resorption and deposition leaves gaps in the record of growth and missing bone tissue is a case at any stage of a vertebrate's life cycle; 'complete specimens that allow precise identification are extremely rare'.
[1] 2) Retro calculating through arithmetic estimate which requires the sampling of several parts of other bone and making an estimate of the number of missing tissues[1] 3) Retro calculating by superimposition in an Ontogenic series which requires a complete growth record on one individual so that their histological cross sections can be overlaid and reconstructed on another individual.