Wednesday, October 29, 2008

Chasing Dinosaurs: Where To Look For Fossils

By Amy Nutt

Dinosaurs have long been a source of fascination and the inspiration for many stories and scientific explorations. Fossilized dinosaur bones have been discovered in different parts of the world for centuries, with the first scientifically recorded specimen called Megalosaurus unearthed near Oxford in 1824 by William Buckland.

Since then paleontologists and dinosaur experts have been coordinating digs worldwide with many stunning skeletons now on display in national museum collections.

Where Are Most Dinosaur Fossils Found?

North America is the number one place to look when it comes to these prehistoric creatures. China and Mongolia come in second with 'dragon' bones (as the locals called them), having been uncovered for thousands of years.

In the US more kinds of dinosaurs have been found than anywhere else in the world and Dinosaur Provincial Park in Alberta, Canada has yielded the highest numbers of species found, with 37 different kinds unearthed.

Everything from the Tyrannosaurus to the Brachiosaurus has been carefully removed piece by piece from the North American landscape and then painstakingly put back together.

Recent discoveries include the bizarre Therizinosaurid dinosaur in Utah (which has a combination of bird-like features and large claws) and a four-ton mummified Hardrosaur nicknamed Dakota. Dakota was unearthed in North Dakota and is an extremely well preserved, rare find that has paleontologists around the world excited.

Why Is North America So Conducive To Finding Dinosaur Bones?

For animals to become fossilized certain conditions must be present at the time of death. The body has to be in a place where it can be buried right away so that decomposition and disintegration of the bones can't take place. Along with this entombment certain minerals need to infiltrate the bones to make them resistant to crushing, a process called permineralization (this is an extremely slow process that is integral to the formation of fossils and petrified remains). Usually floodplains, river systems or the complete opposite, dry, arid deserts allow for this to happen.

In the fluvial settings (places where flowing water is present) dinosaurs were immediately buried in the river channels or covered up by sediment from floodwaters. During this process the scavengers and bacteria had no time to destroy the carcass and the mineral rich water could permeate the bones making them almost like stone. Entombed and preserved in this sediment they become fossilized.

Dinosaurs dying in the desert were also preserved due to a lack of organisms present in the arid environment that could break down the body. Scavengers were less attracted to the desiccated carcasses and so the sand buried the intact remains. During wet seasons rainfall infused the bones with minerals and fossilization took place.

These fluvial and desert environments were present across North America during the time of the dinosaurs and allowed the bones to be preserved, waiting for discovery.

Discovery

For dinosaur bones to be discovered certain conditions must also be present in the current environment. Long buried fossils become exposed when geologic uplifting (the process that forces land upwards) brings the old sedimentary layers close to the earth's surface. Erosion then exposes these sedimentary layers and consequently any fossilized creations. Through careful excavation and specialized tools we can then finish the job nature started.

Prime regions for finding dinosaur bones are deserts with bluffs, buttes and cliffs, canyons, riverbanks and flood plains, mountainous zones and eroded hillsides. These places also need to be open and unpopulated areas where the bare earth is available for paleontologists to dig for remains.

This is why, geographically, North America has the perfect environment for digging up the past. - 15437

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