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Index fossils must have a short vertical range, wide geographic distribution and rapid evolutionary trends. Another term, "zone fossil", is used when the fossil has all the characters stated above except wide geographical distribution; thus, they correlate the surrounding rock to a biozone rather than a specific time period.
In biology, an identification key, taxonomic key, or frequently just key, is a printed or computer-aided device that aids in the identification of biological organisms. Historically, the most common type of identification key is the dichotomous key , a type of single-access key which offers a fixed sequence of identification steps, each with ...
Illustrates the fossil range of a taxon, the geological range of a stratigraphic unit, or other ranges on a geological timescale. Intended for use in {{taxobox}}es, {{Infobox rockunit}} s, and other infoboxes. For pre-Phanerozoic ages, see {{Long fossil range}}. You can give a numeric range, or specify the periods involved.
However, if the fossil species recorded are similar, the two sediments are likely to have been laid down around the same time. Ideally these fossils are used to help identify biozones, as they make up the basic biostratigraphy units, and define geological time periods based upon the fossil species found within each section.
After 1.5 million years ago (extinction of Paranthropus), all fossils shown are human (genus Homo). After 11,500 years ago (11.5 ka, beginning of the Holocene), all fossils shown are Homo sapiens (anatomically modern humans), illustrating recent divergence in the formation of modern human sub-populations.
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In the stratigraphy sub-discipline of geology, a Global Standard Stratigraphic Age, abbreviated GSSA, is a chronological reference point and criterion in the geologic record used to define the boundaries (an internationally sanctioned benchmark point) between different geological periods, epochs or ages on the overall geologic time scale in a chronostratigraphically useful rock layer.
Most of the generic names in this list come from Jack Sepkoski's 2002 compendium of marine fossil genera, which can be corroborated by other sources such as Part L, Ammonoidea, in the Treatise on Invertebrate Paleontology. Additional generic names included come from the Treatise or various peer review scientific journals.