Tundra
Tundra is the cold, treeless region around the poles that has permafrost as one of its defining features. Even at the height of summer, the soil a few centimetres under the surface remains frozen. The tundra therefore lacks animals that dig deep burrows and plants that require deep root systems. The permafrost, plus the short summer and seasonal waterlogging, also explains why trees don't grow here.

DINOSAUR REPRODUCTION

DINOSAUR REPRODUCTION

Very little is known about dinosaur courtship, rivalry, pairing and mating.

EGGS
Dinosaurs hatched from eggs laid by females after sexual reproduction. The eggs were round or elongated and had hard, brittle shells. Internally, these eggs were similar to those of reptiles, birds and primitive mammals; they contained a membrane (called the amnion) that kept the embryo moist. Some dinosaurs cared for their eggs, others simply laid them and then abandoned them.
The first fossilized dinosaur eggs found (and the biggest yet to be found) were football-shaped Hypselosaurus eggs found in France in 1869. These eggs were 1 foot (30 cm) long, 10 inches (25 cm) wide, had a volume of about half a gallon (2 liters), and may have weighed up to 15.5 pounds (7 kg). The smallest dinosaur eggs are about 1 inch across; they are from Mussaurus.

Many fossilized dinosaur eggs have been found, at over 200 sites in the USA, France, Spain, Mongolia, China, Argentina, and India. Very rarely, the eggs have preserved parts of embryos in them, which can help to match an egg with a species of dinosaur. Without an embryo, it it difficult to match an egg to a dinosaur species. The embryo in an egg sheds light on dinosaur development.

FOSSIL OR ORIGINAL SHELL?
According to Dr. Kenneth Carpenter of the Denver Museum, most dinosaur eggshells still have the original shell, not a fossilized replica, "The slightest change in the calcite making up the shell destroys the very fine detail that can be seen with the scanning electron microscope. Amino acids have also been recovered that are very similar to those found in modern bird eggshell."

RECENT FINDS
About 10 large dinosaur eggs (plus 3 egg impressions) were found 1999 in southwestern France (near Albas, in the foothills of the Pyrenee Mountains). No bone fossils were found. The eggs had been buried in two layers in the sand. No one knows what type of dinosaur the eggs were.

Much larger egg sites have been found nearby, in northeastern Spain near Tremp, where hundreds of thousands of eggs (of both sauropods and theropods) have been found. Other huge dinosaur eggs sites have been found in Argentina and China.

NESTS

Fossils of dinosaurs' burrows and nests can reveal a lot about their behavior. Nests vary from simple pits dug into the earth or sand to more complicated nests constructed with mud rims. They may appear in large groups or all alone. The nests and the clutches of eggs reveal information about the dinosaur's nurturing behavior.

Woolly mammoth

Woolly mammoth
A great deal has been found out about woolly mammoths from analysis of carcasses frozen in the Siberian permafrost and from depictions in ancient art. They were built like elephants, but with adaptations to prevent heat loss - tiny ears, short tails and a thick coat of dark brown hair. On the underbelly, the hair grew up to a metre long and was probably shed in the summer. Their trunks ended with two 'fingers' that helped pluck grass. Humps of hair and fat behind the head made the shoulders seem higher than the pelvis. However, the front and back legs were actually about the same length.

Scientific name: Mammuthus primigenius
Rank: Species
Common names: Tundra mammoth