Trilobites are hard-shelled, segmented creatures that lived hundreds of millions of years ago in the Earth’s ancient seas. They are considered to be one of our planet’s earliest complex life-forms and are one of the key signature creatures of the Paleozoic Era. Trilobites went extinct before dinosaurs even existed.
Next to dinosaur fossils, trilobites command a dedicated and passionate following amongst both scientists and fossil collectors, alike. In a relatively short time-frame (scientifically speaking, of course), we have the emergence and subsequent extinction of these fascinating creatures. Still most baffling is the incredible diversity of sizes and features that made up the trilobite group. Many bizarre species co-existed with highly specialized body parts that defy the theories of evolution in their “sudden” emergence and diversity during the Early Cambrian Period in what is known as the ‘Cambrian Explosion’.
Trilobites were among the world’s first arthropods, a phylum of hard-shelled creatures with multiple body segments and jointed legs (although the legs, antennae and other finer structures of trilobites only very rarely are preserved). They constitute an extinct class of arthropods, Trilobita, that is comprised of over 15,000 known species.
It has been reported that every year, four to five new species are discovered in the Atlas and Anti-Atlas Mountain regions in Morocco, alone! This desolate northern fringe of the Sahara Desert was once covered by a prehistoric ocean and its fossil deposits can be considered the world’s richest and most diverse source of these ancient sea creatures.
Trilobites are the single most diverse group of extinct organisms that ever existed, period! The smallest known trilobite is just three millimeters long, while the largest type grew to a length of 70 centimeters (over two feet long!). The most common fossil of trilobites is the mineralized dorsal exoskeleton of the creature. This is found in partial form from molting (shedding the shell as it grows) or in complete form when the animal was buried and died intact. The soft parts of the underside are rarely preserved. The name ‘TRILOBITE’ means ‘three lobed” and is derived from the fact these animals had bodies featuring three longitudinal lobes, not lateral (head, body, tail) as is often thought. The lateral division of three parts is shared by many arthropods, not just trilobites.
Considerable study has been done on trilobites as a whole organism. Even more fascinating though, is the research done on a microscopic level with regards to trilobite morphology. Radiographs have captured incredible detail of complete and fully articulated antennae and underparts like legs and gills, preserved in the host rock of some fossilized specimens. Perhaps the most impressive and classic feature of trilobites that comes to mind is the eyes. Microscopic studies of trilobite eye structures have also revealed marvelous adaptation and very high degrees of specialization in vision.
It seems that the more we learn about trilobites, the unfolding of their mystery is stranger than fiction. Certainly we gain a greater appreciation with each new discovery of these strange and highly advanced but now extinct ‘butterflies of the ancient seas’.
Source: Paleo Direct