"Evolution of Life on Earth"(3)

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Paleozoic Era (1)

Cambrian, Ordovician / Silurian / Devonian

Cambrian, Ordovician Periods
Cambrian, 570-505 million years ago, is the oldest period in the Paleozoic Era. The emergence of marine invertebrate fossils bearing hard skeletons, such as trilobites and archaeocyathids, characterizes the Cambrian Period. This event is called "Cambrian explosion", which marks a remarkable episode in the evolutional history of life on the planet Earth.
Ordovician is the second oldest period in the Paleozoic, spanning some 67 million years, and many invertebrates first appeared in the Cambrian continued to flourish in shallow seas.

Anomalocaris canadensis
British Columbia, Canada
Middle Cambrian
(5.7cm long)

Archaeocyatha
Flinders Ranges, Australia
Cambrian

(12cm wide)

Acadoparadoxides sp. (Trilobite)
Morocco; Middle Cambrian

(36.5cm long)

Silurian Period
Silurian Period, 438-408 million years ago, in the third oldest time unit in the Paleozoic Era. Strata of Silurian age are subdivided into four stages by index fossil species of graptolites. The Silurian is characterized by worldwide distribution of biogenic carbonates of the kind deposited by fossil reefs which were built by stromatoporoids and corals. Land plants appeared for the first time at the end of the Silurian. Silurian sequences are found in limited areas in the Japanese Islands.

Graptolites
Thuringen, Germany

(10cm wide)

Acervularia ananas (Tetracoral)
Gotland, Sweden

(6.5cm wide)

Catenipora sp. (Tabulata)
Gotland, Sweden

(11cm wide)

Devonian Period
Devonian Period, 408-360 million years ago, is the fourth oldest time unit in the Paleozoic Era. In Devonian time, continents were assembled into two large masses, Laurasia in the north and Gondwana in the south. Desert environments appeared in parts of Laurasia and sediment deposited in such arid areas are called "the Old Red Sandstone". Diverse fern species began to build forests on land. Devonian is also called the "Age of Fish" since varied species of primitive fishes such as coelacanths and lungfish flourished in the sea. The first amphibian, Ichthyostega, appeared late in the Devonian and became the first vertebrate living on land. In warm shallow tropical seas, stromatoporoids, rugose and tabulate corals, and bryozoans built extensive reefs. The reefs were in turn inhabited by other marine animals such as brachiopods and crinoids.

Phacops megalomanicus (Trilobite)
Morocco
Middle Devonian

(13cm long)

Ophiuroids
Furcaster palaeozoicus (front), Bundenbachia beneckei (back), Eospondylus primigenius (right)
Bundenbach, Germany

(9-13cm long)

Eusthenopteron foorodi (Pisces)
Canada

(16.5cm long)

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