To establish the age of a rock or a fossil, researchers use some type of clock to determine the date it was formed. Geologists commonly use radiometric dating methods, based on the natural radioactive decay of certain elements such as potassium and carbon, as reliable clocks to date ancient events.

Sedimentary rocks may have radioactive elements in them, but they have been re-worked from other rocks, so essentially, there radiometric clock has not been re-set back to zero. However, sedimentary rocks can be age dated if a volcanic ash horizon or a diabase sill or dyke can be found within the sequence.

Relative age dating tells us which fossils are older and which fossils are younger. The fossil species below the ash must be slightly older than 507 million years, and the species above the ash must be slightly younger. If rocks in different places contain the same fossil species, they must be similar in age.

Relative dating is used to determine a fossils approximate age by comparing it to similar rocks and fossils of known ages. Absolute dating is used to determine a precise age of a fossil by using radiometric dating to measure the decay of isotopes, either within the fossil or more often the rocks associated with it.

A T. rex grew from a tiny hatchling to a 9-ton predator in about 18 to 20 years, gaining an unbelievable 1,700 pounds per year. A full-grown Tyrannosaurus rex weighed about 6 to 9 tons. It stood about 12 to 13 feet tall at the hip and was about 40 to 43 feet long.

Scientists discovered what they thought were 3.5 billion-year-old fossils in western Australia almost 40 years ago. A new study reveals that these rocks did indeed contain organic life — making them the oldest fossils ever found. The finding confirms that Earth was home to microbial organisms 3.5 billions years ago.

While the art market is organised around brand-name artists, dinosaur sales are all about celebrity species, with a tyrannosaurus rex skeleton fetching up to $10m, although the velociraptor is the most prized. The price tag for a triceratops’s skull is $170,000 to $400,000, and a diplodocus is $570,000 to $1.1m.

Elaphrosaur: Rare dinosaur identified in Australia

• A fossil unearthed in Australia by a volunteer digger has been identified as a rare, toothless dinosaur that roamed the country 110 million years ago.
• The elaphrosaur, whose name means “light-footed lizard”, was related to the Tyrannosaurus Rex and Velociraptor.

Tyrannosaurus rex

A nearly complete skeleton of a Tyrannosaurus rex, standing 13 feet high, 40 feet long and comprised of 188 bones, sold at auction for a whopping $31.8 million Tuesday night, breaking the record for the highest price paid for dinosaur fossils.