Biostratigraphic dating

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earlier than the other species, most probably Pristerognathus Assemblage Zone) Synonyms: Pachyrhinos kaiseri (Broili & Schroeder, 1934) The holotype of the type species, Gorgonops torvus, was in 1876 one of the first therapsids described, by Richard Owen, who also coined the name "Dinosauria" on the basis of the first known dinosaur fossils.

It was also used as the type for which Richard Lydekker described the family in 1890.

In addition, like any good scientific measurement, every dated boundary has an uncertainty associated with it, expressed as " /- X millions of years".

These can not be included in the diagram for practical reasons, but can be found in Harland et al., 1990, along with a detailed description of the history of earlier-proposed time scales and the terminology, methodology and data involved in constructing this geological time scale.

It is important to realize that with new information about subdivision or correlation of relative time, or new measurements of absolute time, the dates applied to the time scale can and do change. ISBN 0-521-38765-5 [One of the more recent compilations of the entire geologic time scale.] Holmes, A., 1937.

Revisions to the relative time scale have occurred since the late 1700s.

This was a medium-sized therapsid, with a skull about 22 cm in length.

Absolute time measurements can be used to calibrate the relative time scale, producing an integrated geologic or "geochronologic" time scale. [One of the earlier attempts at an integrated geochronologic time scale.] Obradovich, J.

Geological Association of Canada, Special Paper 39, p.379-396.

Gorgonops (from Greek Γοργών -Gorgon- and ὤψ -eye, face-, literally "Gorgon' eye" or "Gorgon' face") is an extinct genus of therapsid which lived about 260-254 million years ago, during the Late Permian.

The time scale is depicted in its traditional form with oldest at the bottom and youngest at the top -- the present day is at the zero mark. This is a good starting point to get the basic principles.] Grotzinger, J.

Geologic time is finely subdivided through most of the Phanerozoic (see Harland et al., 1990 for details), but most of the finer subdivisions (e.g., epochs) are commonly referred to by non-specialists only in the Tertiary.

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