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Trilobite
Ecology and Ancient Environments
This page
last revised 02 April 2008 by S. M. Gon III
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courtesy of the PaleoMap Project developed by Christopher R. Scotese. |
Half a billion years
ago, the Earth's marine environment was certainly not the same as
it is today. It is likely that the ocean's chemistry,
including salinity, was different, and the configuration of the ocean basins
and continents was entirely unlike our modern globe, because of continental
drift.
Biotic environments (the living community of plants and animals) were also different. While there were many species of marine plants and animals, many groups prominent today were missing, or poorly represented. For example, in the Cambrian and Ordovician, there were no jawed fishes, and Crustaceans (crabs, shrimps, etc.) which dominate the arthropod fauna of today's oceans, were present, but not prominent. |
Trilobite tracks (Cruziana) courtesy of The Paleo Project It is thought that the majority of trilobites were bottom-dwellers, crawling on the sea floor, or within complex reefs, acting as roving predators on smaller invertebrates or as slow scavengers on organic debris. |
A Bumastoid trilobite crawling on the benthos. from the Virtual Silurian Reef. They were able to dig into the bottom sediments in search of food
and to conceal themselves from predators. Perhaps some were herbivores
on beds of algae (seaweed), or browsers on corals,
sponges, or bryozoans. Some may have been filter
feeders, orienting with the current and extracting plankton and organic
debris. Trilobite Feeding Habits |
This image of oncocerid nautiloids from the Virtual Silurian Reef Nautiloids were probably important predators of trilobites. Trilobites certainly were important prey for larger creatures. At first these were large invertebrates, such as predatory worms, nautiloids, sea scorpions (eurypterids), crustaceans, and perhaps Anomalocaridids. When fishes developed and flourished in the Devonian, we can be sure that trilobites were hard pressed by these new predators. A hard exoskeleton and the ability to enroll protected trilobites from predators and sudden unfavorable environmental changes. |
 Opipeuter
pelagic
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There is certainly a very wide range of body forms associated with trilobites. There are extremely spiny species, and ones entirely smooth and devoid of spines. There are species (such as the telephinid Opipeuterella shown at left) with huge eyes and narrow bodies that seem adapted to swimming in the pelagic (open ocean) water column. Other species (such as the trinucleid Cryptolithus, shown at right) were eyeless, with wide bodies and supporting structures such as long genal spines, that seem adapted for a dark benthic (ocean bottom) habitat. Some of the speculations on lifestyle and function of body shapes and features may never be clearly confirmed, but what we do know is that trilobites were extremely successful, found in a very wide variety of ocean habitats, and probably occupied many, if not all of the ecological niches that crustaceans do today. That being the case, we know of planktonic, free-swimming, benthic (bottom-dwellers), burrowing, reef-dwelling, and even parasitic crustaceans, and all of these forms have been attributed to trilobites as well. | 
Cryptolithus benthic |
