An illustration of a group of Woolly Mammoths feeding on wild grass in an ice age grassland during an autumn feast.

The woolly mammoth (Mammuthus primigenius) was a species of mammoth, the common name for the extinct elephant genus Mammuthus. The woolly mammoth was one of the last in a line of mammoth species, beginning with Mammuthus subplanifrons in the early Pliocene. M. primigenius diverged from the steppe mammoth, M. trogontherii, about 200,000 years ago in eastern Asia. Its closest extant relative is the Asian elephant.

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Just as other prehistoric lifeforms such as insects or cyanobacteria (blue-green algae), the dinosaur lineage are still with us today. Evolutionary adaptation seems to keep pace with the changes in the environment of the Earth. While some lifeforms such as cyanobacteria and insects seem to be nearly perfectly adapted without a need for radical morphological change for any of the Earth's periods, others such as dinosaurs needed to change quite significantly. The larger theropod (T-rex) and sauropod (Brontosaurs) dinosaur varieties were not well adapted to change and subsequently had a glorious run then mostly disappeared for a variety of reasons. The small theropod dinosaurs such as Ornitholestes (illustrated above) on the other hand had a future, but would still need adaptations along the way to adjust to the ever-changing environments in which they continued to evolve. That form would be what we now refer to as birds.  

While the small dinosaur Ornitholestes is long since extinct, her basic biology was solid enough in her close genetic cousins, for instance, to adapt to flight or even lose their teeth completely in favor of a beak. It it is not difficult to imagine, when looking at a modern Cassowary for example, to really get an idea of just how these small theropods looked or even moved around and behaved during the Jurassic Period. Feathers as a flock of fur (a type of scale actually) would have come around first to provide warmth and dryness....and would then further be adapted for flight. Close examination of fossil evidence now confirms that virtually ALL theropod dinosaurs were covered in some form of insulating feather/fur. The Triassic, Jurassic and Cretaceous Periods were a large chunk of the Earth's history and had plenty of cold and wet climates, feathers would have been nearly tantamount to long term survival. 

Having chicken for dinner tonight? Well, you're eating a dinosaur.

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An illustration of a Devonian Period (419 to 358 million years ago) lake scene depicting a cycle of life. The Eurypterids (Sea Scorpions) feed on the smaller Trilobites dwelling on the lake bottom while the enormous placoderm fish Dunkleosteus, in turn, feeds on them.

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An illustration of the dinosaur Brontosaurus excelsus (formerly known as Apatosaurus excelsus) depicted alongside an average height human. Brontosaurus was an extinct genus of sauropod dinosaur that lived in North America during the Late Jurassic period. It had an average length of 22.8 m (75 ft) and a mass of at least 16.4 metric tons.

An illustration of trilobites moving about on the bottom of a warm Paleozoic sea. 

Trilobites are a well-known fossil group of extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period (521 million years ago), and they flourished throughout the lower Paleozoic era before beginning a drawn-out decline to extinction when, during the Devonian, all trilobite orders except Proetida died out. Trilobites finally disappeared in the mass extinction at the end of the Permian about 250 million years ago. The trilobites were among the most successful of all early animals, roaming the oceans for over 270 million years

Trilobites range in length from 1 millimetre (0.04 in) to 72 centimetres (28 in), with a typical size range of 3–10 cm (1.2–3.9 in). The world's largest trilobite, Isotelus rex, was found in 1998 by Canadian scientists in Ordovician rocks on the shores of Hudson Bay.
(definition Source: Wikipedia)

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A herd of Woolly Mammoths march through an ice age forest 60,000 years ago.

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A 3-D computer illustration of colonies of the tiny extinct marine animals known as Diplograptus (Graptolites) of the Ordovician period (which occurred from 505 to 438 million years ago). Diplograptus is characterized by a caplike float from which featherlike assemblages of graptolite organisms were suspended. Though purely an artistic interpretation, the structure of the animal is inferred through scientific notation of what the species may have looked like within the environment in which they existed.


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An illustration of the extinct giant ground sloth Megalonyx searching a tree for food in an Ice Age Ohio forest. Megalonyx jeffersonii was a large, heavily built animal about 9.8 feet (3 m) long existing from the Miocene through the Pleistocene.