Paleoecotoxicology: Extending Environmental Toxicology and Chemistry to the Interpretation of the Fossil Record.

HERKOVITS, J

ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY

SETAC PRESS

Año: 2001 vol. 20 p. 1623 - 1624

0730-7268

Life appears to have developed in the Precambrian era, about 4,000 million years ago. Present day biodiversity is estimated to be more than 100 million species. The fossil record of nonmarine tetrapods from the Devonian era (approximately 400 million years ago) onward exhibits an average of about 50 families until the last quarter of the Cretaceous period, when the number of families increased to nearly 80, and the rise continued to the present 337 in several steps in the Tertiary [1]. A similar pattern of increase in the number of families was also found in the record of marine invertebrates [2]. Conversely, extinction throughout Earth´s history is generally estimated to include more than 90 to 99% of the species that ever lived. Thus, extinction is the rule rather than the exception, and the vast majority of these extinctions are considered to be normal or background extinctions since they have occurred regularly since life originated on Earth [1–3].