Overview 2: Terms associated with the subject

K-T Extinction -- Cretaceous and Tertiary periods when the extinction occurred

K-T Boundary -- a "geological signature", usually a thin band. The boundary marks the end of the Mesozoic era and the beginning of the Cenozoic era, and is associated with the extinction event.



Mesozoic era -- 250-65 million years ago, known as the Age of Dinosaurs because of its association with non-avian (bird) dinosaurs. Lasted for roughly 180 million years. Can be separated into the Triassic, Jurassic, and Cretaceous periods.



Triassic -- 250 to 200 million years ago. During this period, both marine and continental life show an adaptive radiation. The first flying vertebrates, the pterosaurs, evolved in this period.


Coelophysis, one of the first dinosaurs, appeared in this period

Pterosaurs -- flying reptiles, e.g. pterodactylus.






Adaptive Radiation -- the evolution of an animal or plant group into a wide variety of types adapted to specialized modes of life.



Jurassic -- about 200 to 145 million years ago. The middle of the Mesozoic era, also knows as the Age of Reptiles.


Stegosaurus, this period saw the emergence of large herbivore dinosaurs

Cretaceous period -- 145 to 65 million years ago. This period lasted for 80 million years. This period ended with the extinction of many species, including non-avian dinosaurs, pterosaurs and large marine reptiles.


The Tyrannosaurs lived during this period


Cenozoic era -- the current era beginning approximately 65 million years ago. It is marked by the extinction event that saw the demise of the last non-avian dinosaurs and the end of the Mesozoic era. The Cenozoic era is ongoing. Divided into three periods: the Paleogene, Neogene, and Quaternary. Also known as the Age of Mammals.


The Mammoth, along with other animals such as the saber-toothed cat, emerged in this period



Paleogene -- the first part of the Cenozoic era, beginning 65.5 million years ago and ending 23.03 million years ago. Lasting 42 million years, this period is notable for being the time when mammals evolved following the extinction event. Some of these mammals evolved into larger forms that dominated the land, while others became capable of living in marine, specialized terrestrial and even airborne environments. Birds also changed into roughly modern forms.


Among other amnials, this period saw the beginning of the earliest whales.


Neogene -- second part of the Cenozoic era, beginning 23.03 million years ago and ending 2.588 million years ago.


Three-toed horses and other strange animals lived in this time

Quaternary -- the most recent of the Cenozoic era, beginning 2.588 million years ago to the present day


Arctodus 


Tertiary period -- 65 to 2.6 million years ago. This period began with the extinction and spanned to the beginning of the most recent Ice Age.