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The Devonian Period
345 million to 395 million years ago
Mass extinction: corals, ammonoids, trilobites, fish greatly reduced.
Land plants with seeds, molluscs, sponges, corals, brachiopods abundant. First ammonoids, sharks, bony fish
and amphibians
Life in the seas during Devonian times may have been more varied than at any other time in the Palaeozoic Era. On land, plants began to develop and the first amphibians appeared.
Corals remained major reef builders, and
trilobites continued to decline in numbers, although some grew to over 70 centimetres in length. During the Devonian Period the brachiopods evolved to become very diverse and abundant. The most numerous of
this period were the spiriferids.
Molluscs developed in freshwater as well as
in marine sites. Gastropods evolved to be able to cope with a land environment, as did arthropods, producing both millipedes and scorpions. Primitive spiders also evolved. The Devonian Period was the time when fish became abundant in the seas, including species that reached 9 metres long.
This was also the time when the sharks and the bony fish were first found in the seas.
During the Devonian Period, seed plants evolved, so that land plants no longer depended on germination in water.
At the end of this abundant period, there was another mass extinction, with about a quarter of
all families dying out. Ammonoids suffered particularly, as did fish
and amphibians, and corals and trilobites lost half of their families.
(Above) Devonian trilobite: Phacops.
(Below) Silurian trilobite: Calymene.
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(Below) Devonian spiriferid brachiopod: Spirifer bollandensis.