Smithsonian National Museum of Natural History Geologic Time The Story of a Changing Earth
Presented by the Department of Paleobiology.
The Silurian
Contents
Overview
Silurian Marine Life
The Invasion of Land
Geology and Climate
Evidence
Model of Cooksonia
learn more
sample
Tabulate coral
Eurypterid
Silurian diorama
references and links
Foundational Concepts
Dating Methods
Earth Processes
Life Processes
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The Invasion of Land
Early vascular plants, collectively known as rhyniophytes, first appeared in the late Early Silurian and diversified considerably through the Late Silurian. These plants had evolved an internal system of tubular cells through which water traveled up the body of the plant, allowing them to maintain cell functions higher above the land surface than would otherwise have been possible. Simple, small plants such as Cooksonia lacked leaves, roots, seeds and the capability to grow in diameter, but they were the dominant early terrestrial plants.

By the Middle Silurian, very early terrestrial communities had developed around the tiny, vertically growing plants that acted as primary producers. True herbivores were absent from these early land ecosystems. Dead plants were recycled by fungi and bacteria. Early arthropods—possibly related to millipedes—also fed on dead and decaying plant matter rather than on living plant tissues. These arthropod detritivores may also have digested the bacteria and fungi that lived in the soil. Other arthropods, possibly related to centipedes, preyed upon the detritivores. The Mid–Late Silurian terrestrial biota was probably confined to relatively wet areas.

The brackish and freshwater habitats near land were invaded by a variety of animal species, including eurypterids, xiphosurids, scorpions, and jawless fishes. This increase is probably linked to the expansion of vascular plants into aquatic and terrestrial habitats, which would have increased the amount of food available. Most aquatic animals were relatively small (less than 20 centimeters), but some eurypterids exceeded a meter in length and are, in fact, the largest known arthropods. Feeding dynamics in Late Silurian estuaries appear to have been relatively simple. Most animals probably fed on benthic (bottom) detritus and/or algae. Eurypterids and aquatic scorpions were the dominant large predators.




Overview | Silurian Marine Life | The Invasion of Land
Geology and Climate



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