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Trilobites were among the first of the
arthropods,
a phylum of hard-shelled creatures with multiple body segments and
jointed legs (although the legs, antennae and other finer structures of
trilobites are rarely preserved). They constitute an extinct class
of arthropods, the Trilobita, made up of
eight orders, over 150 families, about 5000 genera, and over 15,000
described species. New species of trilobites are unearthed and described
every year. This makes trilobites the single most
diverse group of extinct organisms, and within the generalized body plan of trilobites
there was great deal of diversity of size and
form. The smallest known trilobite species is |
just under a millimeter
long, while the largest include species from one to two feet in length.. With such a diversity of species and
sizes, speculations on the ecological role
of trilobites includes planktonic, swimming, and crawling forms, and we
can presume they filled a varied set of trophic (feeding) niches,
although perhaps mostly as detritivores, predators, or scavengers.
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phacopida |
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agnostida |
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