Traces of Ancient Life

illions of years ago, our planet was not as we know it today. The continents were arranged differently, and the climate, flora, and fauna were different. How do we know this? We have learned these things by finding and studying fossils, remains of past life-forms that are preserved in both geography and time. The Ediacara, in southern Australia, and the Burgess Shale, in Canada, are two regions with extensive fossil beds of soft-bodied invertebrates. Both areas have shed light on what is known as the Cambrian explosion. •

Burgess Shale

^^ Located in Canada, Burgess Shale is ^^ well known for its fossil bed of soft-bodied animals from the Cambrian Period. This bed gives a glimpse of what ocean life was like during the Cambrian Period, with specimens of the four main types of arthropods: trilobites, crustaceans, horseshoe crabs, and Uniramia (the group that includes insects).

million years

AGE OF THE FOSSILS FOUND IN THIS BED

EVOLUTION

Trilobites are the best-known fossilized animals to appear during the Cambrian explosion. The fossil record shows an extraordinary proliferation of life-forms during this stage of life on Earth. From this time on, no new structures of morphological organization appeared. Rather, existing forms evolved and diversified.

AYSHEAIA

Olenoides Xandarella Emeraldella Yohoia Sidneyia Burgessia

Ediacara

This group, called Ediacara fauna, is the oldest known group of multicelled organisms. Found in Precambrian rock, it predates the great Cambrian explosion. Its age is around 600 million years; it contains impressions, or molds, of diverse animal forms conserved in sedimentary rock, without a trace of hard parts. The first such bed was found in southern Australia, in the Ediacara Hills.

DICKINSONIA SPECIES

Believed to belong to the Cnidarian (coral, jellyfish, anemones) or Annelid (worms) phyla. The largest was 17 inches (43 cm) long.

million years

AGE OF THE FIRST SPECIMENS FOUND

AUSTRALIA

AUSTRALIA

The first specimens were found in the Ediacara Hills.

The first specimens were found in the Ediacara Hills.

JELLYFISH

Ediacaran

JELLYFISH

Ediacaran

AYSHEAIA

Olenoides Xandarella Emeraldella Yohoia Sidneyia Burgessia

DICKINSONIA SPECIES

Believed to belong to the Cnidarian (coral, jellyfish, anemones) or Annelid (worms) phyla. The largest was 17 inches (43 cm) long.

MARRELLA SPLENDENS

Less than one inch long, this creature is thought to live on the seafloor.

20 inches (50 cm)

One of the most widely found fossils of the Ediacaran Period. It is believed to have been related to certain cnidarian colonies.

MARRELLA SPLENDENS

Less than one inch long, this creature is thought to live on the seafloor.

OTTOIA

This priapulid worm could measure up to 3 inches (8 cm) long.

SIZES

The Burgess Shale invertebrates had a wide range of sizes, from microscopic to nearly 7 feet (2 m) long. (Dogs, on the other hand, have a narrower size range; the most common breeds range from 20 to 40 inches [50-100 cm] tall.).

20 inches (50 cm)

FOSSILS

Fossils yield clues about life in the past. By comparing fossilized organisms from different periods of the Earth's history with organisms of today, we can deduce how various life-forms have changed over time.

Photograph of amber that contains fossil remains from 38

million years ago. This piece is valued at nearly $35,000.

FOSSILIZED ARACHNID

This spider, perfectly conserved thanks to the protection of the amber, enables scientists to make reliable comparisons with genera and species of today.

Diverse Origins

■'TheCmelting point of amber

Value

Amber containing animals that lived millions of years ago is used to make jewelry. Its price depends on the type of organism it contains.

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