more precise timescale of Earth history
Above the palaeozoics was a sequence of rocks that contained a combination of shells, fish, and land-living saurians (or ‘crawlers’, which today would include amphibians and reptiles); these rocks were designated broadly as ‘Secondary’ (nowadays Mesozoic, ‘middle life’). Above the mesozoics were found rocks that contain creatures more similar to those living today, notably because they include mammals and birds; these were named ‘Tertiary’ (now also called Cenozoic, ‘recent life’). Animatronic Dinosaur And finally, there was the ‘Quaternary’ (or Recent) that charted the appearance of recognizably modern plants and animals and the influence of the great ice ages.
This general pattern has stood the test of time remarkably well.
All modem geological timescales continue to recognize these relatively crude, but fundamental, subdivisions: Paleozoic, Mesozoic, Dinosaur Costume Cenozoic, Recent. However, refinements in the way the fossil record can be examined for example, through the use of high-resolution microscopy, the identification of chemical signatures associated with life, and the more accurate dating of rocks enabled by radioactive isotope techniques have led to a more precise timescale of Earth history.