Lecture 4: Dinosaurs in Context III - Time and Geology

Vocabulary flashcards defining key concepts, eras, dating methods, and organism groupings from Lecture 4.

Deep Time

The geological term for prehistory, referring to time scales derived from fundamental physical constants and radiometric decay rates.

Stratigraphy

The study of rock layers, originating in the 1600s with fossil seashell collectors, which accelerated the Industrial Revolution by aiding coal discovery.

Relative Dating

A geological dating method used since the 1600s in which the age of a rock unit is inferred from its position relative to surrounding rock units.

Absolute Dating

A dating technique introduced in the 1930s that calculates a numerical age based on direct measurements, such as radioactive isotope half-lives.

Phanerozoic Eon

The eon meaning 'visible animals' covering approximately the last $11.9\%$ of Earth's history, comprised of the Paleozoic, Mesozoic, and Cenozoic eras.

Paleozoic Era

The geological era meaning 'ancient animals' that preceded the dinosaurs, marked by early plant evolution, marine fish, and the transition of vertebrates to land.

Mesozoic Era

The geological era meaning 'middle animals' spanning from $251\,\text{MYA}$ to $66\,\text{MYA}$, commonly referred to as the 'Age of Dinosaurs'.

Cenozoic Era

The geological era meaning 'new animals' extending from $66\,\text{MYA}$ to the present, commonly called the 'Age of Mammals'.

Anapsids

Primitive reptile-like animals characterized by solid skulls containing only openings for the eyes and nostrils.

Synapsids

Stem-mammals characterized by a skull featuring a single temporal fenestra (hole) behind the eye socket above the cheek bone.

Diapsids

A clade of animals characterized by skulls with two temporal fenestrae behind the eyes, including dinosaurs, crocodilians, lizards, and snakes.

Temporal Fenestra

An anatomical opening in the skull behind the eye orbit that allowed for the attachment and expansion of more powerful jaw muscles.

Permian Period

The final period of the Paleozoic Era during which tetrapods became fully terrestrial, Pangea formed, and synapsids dominated land ecosystems.

Therapsids

Highly active Late Permian synapsids exhibiting advanced mammal-like features such as elevated metabolisms, probable fur, and limited parental care.

Permo-Triassic Extinction

Also known as 'The Great Dying,' a massive mass extinction event at the end of the Permian Period that wiped out over $90\%$ of all life on Earth.

Archosaurs

A group of diapsids that diversified in the Middle Triassic on land at the expense of larger stem-mammals, eventually giving rise to crocodilians and dinosaurs.

Dimetrodon

A basal, semi-terrestrial stem-mammal (synapsid) from the Paleozoic that lived in swampy environments and is frequently misidentified as a dinosaur.