Sclerochronology
In zoology and paleontology, sclerochronology refers to various methods for analyzing the growth of biogenic hard parts such as exo- and endoskeletons , teeth and otoliths . With reference to the cortical bone tissue of vertebrates , one also speaks of skeletochronology . Similar to dendrochronology , the growth in thickness of a skeletal element is interpreted as a temporal sequence of individual increases (growth increments ), the analysis of which as a time series enables statements to be made about abiotic environmental factors and endogenous factors of growth.
Cyclical changes in the chemistry and in the microstructure of the skeletal substance, for example as a result of daily or seasonal fluctuations in environmental conditions, appear along the cross-section of a skeletal element as growth zones (analogous to tree rings ). Trace element and isotope examinations of a representative number of samples of the skeletal substance, which were taken from the hard part to be examined in the direction of growth, represent a further source of information in sclerochronology (independent of macroscopically or microscopically visible growth patterns).
Analysis of the growth rate
Long-term growth trends can be read from the annual growth rates, which can be separated by zones of stagnation. The comparison of the growth curves of skeletons of related species provides information on the evolutionary change in the timing of individual development ( heterochrony ).
Reaching sexual maturity can be accompanied by an abrupt slowdown in skeletal growth, resulting in the recent annual annuli of a cross-section of bone or shell being very small, i.e. H. the growth curve shows a kink.
Research history
The description of sclerochronology goes back to Leonardo da Vinci , who described the clearly distinguishable zones of annual growth in fossil shells and snails as early as the first decade of the 16th century. Based on these observations, he turned against the Neoplatonic interpretation of fossils as stones formed directly in the rock by forming forces. If these fossils were not the remains of living things, they would not need clearly defined growth zones.
However, sclerochronology did not establish itself as a scientific method until the second half of the 20th century.
See also
Dendrochronology , biogeochemistry
literature
- Bruce J. MacFadden (Ed.): Incremental Growth in Vertebrate Skeletal Tissues: Paleobiological and Paleoenvironmental Implications. In: Palaeogeography, Palaeoclimatology, Palaeoecology 206 (3-4), 2004, pp. 177-382, ISSN 0031-0182
- Bernd R. Schöne, Donna Surge (Ed.): Looking back over Skeletal Diaries - High-resolution Environmental Reconstructions from Accretionary Hardparts of Aquatic Organisms. In: Palaeogeography, Palaeoclimatology, Palaeoecology 228 (1-2), 2004, pp. 1-192, ISSN 0031-0182
- Douglas S. Jones, Stephen Jay Gould: Direct Measurement of Age in Fossil Gryphaea: The Solution to a Classic Problem in Heterochrony . Paleobiology, Vol. 25, No. 2, pp. 158-187, 1999