Introduction to Trilobites main content.

Introduction to Trilobites

Whether you revel in their myriad Paleozoic permutations, or merely view them as bizarre remnants of an incredibly distant time, there seems to be no denying that trilobites are fascinating creatures. Indeed, these fossilized arthropods hold the distinction of being the first dominant form of complex life on earth, appearing at a time when the world was just emerging from its "Frozen Planet" state and the seas were ripe for the blossoming of biodiversity. By the time the Cambrian period began producing an amazing array of strange and previously unseen fauna some 521 million years ago, trilobites were already advanced organisms possessing both hard exoskeletons and well-developed eyes.

Though their true origins remain shrouded in Precambrian mystery, there can be little doubt that the root stock of the trilobite lineage stretches well back into that poorly understood period of our planet's early history. Yet as soon as their remains started filling the fossil record at the dawn of the hallowed Cambrian Explosion, trilobites were already the unquestioned kings of the Earth's primordial seas. These strangely beautiful creatures - named not for their distinctive cephalon, thorax and pygidium (head, body, tail), but rather for the three lobes that divide their lateral symmetry - would eventually evolve into more than 20,000 scientifically recognized species and dominate the world's oceans for the next quarter of a billion years.

While complete fossil specimens stand as relatively rare discoveries, the fact is that trilobite remains are nothing short of pervasive; throughout the globe, entire strata and biozones have been named for their prolific remains. In fact, it is hard to find a place on Planet Earth where their exoskeletons are not found preserved in various slates, shale or sandstones. Trilobites have been uncovered everywhere from near the top of the Himalayan Mountains to the areas surrounding California's Death Valley, as well as in locales as diverse as the desolate Russian steppes and sites near major North American cities. Much like some modern arthropods, trilobites apparently molted a number of times each year, with most of the resulting fossils being not of the deceased animal itself, but rather of the often disarticulated pieces of its cast-aside external shell.

Of course, back in the Paleozoic - the roughly 300 million year age that ran from the Cambrian through the Permian, and which has become known in scientific circles as the Age of Trilobites - our planet looked far different than it does today. The continents we now instantly recognize by their shape and global alignment were yet to be transported to their present positions via plate tectonics. They were located clumped together in radically obtuse hemispheric positions, with one or at times two major land masses dominating what was otherwise a water-world.

Much of what we now know as the continents of North America, Asia, Africa and Europe were partially under sea level, allowing trilobites to become fossilized in locations presently situated hundreds of miles from the nearest prominent body of water. It is an on-going debate as to whether or not trilobites inhabited both fresh and salt water environs, though contemporary scientific opinion overwhelmingly favors the latter. From Canada to England, from Australia to China, from Russia to Bolivia, "bugs", as they are fondly known by those who both collect and study trilobites, filled virtually every aquatic environment of their world. And while over the last decade, trilobites from previously unknown deposits in Africa and Asia have most attracted the attention of the world's enthusiasts, there are many North American dig sites that remain among the most important bug-bearing formations in the world. The United States, in particular, has become renowned for its diverse trilobite deposits, ranging from the Cambrian-age layers of California and Pennsylvania, the Ordovician deposits of Iowa and Utah, the Silurian layers of New York and Indiana, the Devonian outcrops of Ohio and Nevada and the Permian rocks of Texas and New Mexico.

While some of these legendary locales have long-since been lost to human development ("tear down paradise... put up a parking lot"), as world-wide interest in trilobites continues to grow - spurred on, to a great extent, by a technological revolution, which in recent years, has taken the preparation and display of fossils to previously unimagined dimensions - new digging sites seem to be emerging on an annual basis. From private quarries, to inaccessible mountain tops and highway road cuts, industrious collectors and savvy scientists have begun busying themselves looking for previously unknown fossil beds or undescribed trilobite species. Even historically old sites, like the Rust/Walcott quarry in New York State, have recently been reopened by private groups, often with startling and unexpectedly rich results.

Trilobites stand among the most successful creatures in the history of our planet. Indeed, their success has had an enormous scientific impact, providing evidence for the theories of Continental Drift and Plate Tectonics. Their amazing diversity has made them the stratigraphic marker of the Cambrian Period, as well as allowing them to play a key role in estimating the rate of speciation during the Cambrian explosion. Trilobite studies have resulted in formulating and testing Punctuated Equilibrium as an evolutionary mechanism.

Yet for all the growing attention that currently surrounds them, and despite the vital role they've played in the development of life on our planet, the simple fact is that the average person either understands the lure of trilobites, or they don't. Either the observer sees the inherent majesty of these ancient "Butterflies of the Sea" or they dismiss them as little more than primordial ocean slugs. Occasionally those not particularly attuned to the off-beat "beauty" of these primitive creatures will respond with a marked lack of enthusiasm when a prized specimen is thrust under their noses by some slightly overzealous collector. For the trilobite enthusiast, however, the possibility of acquiring a new specimen - whether through hand-blistering field work, internet purchase or hard-bargained trade - is one of life's true pleasures.

It is difficult for even the true trilobite enthusiast to explain the almost mystical appeal that these amazingly diverse organisms hold over them. Perhaps it is the fact that so many still-unknown species are lurking out there somewhere, hiding behind this hill or under that stone pile, and just waiting for some determined and clever collector to free them from their eons-old rock prisons. Perhaps it is the incredible age of these strange-looking creatures that represent one of the Earth's first successful "experiments" with life. Perhaps it is the knowledge that trilobites have been discovered nearly everywhere that sedimentary outcrops exist. Perhaps it is the incredible range in shape and appearance that they can attain. Ranging in size from diminutive agnostids that rarely exceeded a centimeter in length to Isotelus rex, that attained proportions of more than 70 cm, few organisms have ever displayed as much diversity and inherent, albeit quirky appeal as these singularly distinctive examples of ancestral life.

While trilobites have been around - either as living creatures or fossilized remains - for more than 500 million years, the collecting of these unique life forms stands as a relatively recent occurrence. Most geological history books will make reference to European scientists being aware of these "frozen locusts", as they were then called, as far back as the 17th Century. Other tomes may state that certain Native American tribes treated trilobite specimens with the reverence of religious artifacts. It is also believed that President Thomas Jefferson possessed a trilobite as part of his famed "cabinet of curiosities" natural history collection. It is even rumored that trilobites have been discovered among the personal possessions of Ice Age humans found in European burial sites dating back over 50,000 years ago.

For these reasons, and many more, trilobites have begun to exert an ever-growing grip on the hearts and minds of thousands. For many fossil collectors, they rank as the most intriguing of ancient life forms, usurping even the hallowed dinosaur. From their rise at the beginning of the Cambrian, to their demise at the end of the Permian Period some 300 million years later, trilobites, in all of their multi-segmented glory, represent one of early life's most intriguing - and successful efforts. Our quest here is to try to explain why these creatures hold so much appeal, by hopefully providing an interesting, insightful and at times entertaining look at trilobites around the globe. We'll also provide numerous photos of some of the most incredible trilobite specimens ever found, hopefully inspiring a few new trilo "converts" along the way.

Every Trilobite Tells A Story

There are those among us who can gaze upon the fossilized remains of a trilobite and see little more than the vestige of a long-gone creature that has been strikingly preserved in rock. Such a vision is certainly accurate from a purely aesthetic perspective - after all, trilobite fossils are both inherently beautiful and fascinating, invaluable relics drawn from an incredibly distant time. But from a strictly scientific point-of-view, that image of a trilobite embedded in sedimentary stone serves as only the beginning chapter of a long and increasingly complex story.

The fact is that if you look closely, every trilobite fossil tells a unique and often compelling tale. Whether it's a 500 million year old Hemirhodon amplipyge bearing a potentially fatal bite mark, or a 450 million year old Primaspis crosotus appearing forever frozen amid a fossilized field of crinoid stems, each example of these primeval life forms possesses the capacity to provide a captured-in-time glimpse of a long-gone undersea kingdom. With a trilobite in hand, and a healthy imagination at play, each of us can partake in a private sojourn back to a time when trilobites first filled the planet's oceans. 

Indeed, as modern preparation techniques become increasingly efficient and extravagant, ever-more explicit details of trilobite anatomy and corresponding lifestyle have come to the fore, with each discovery adding immeasurably to the stories every trilobite fossil can reveal. Morphological features such as inch-long cephalic spines and wrap-around compound eyes provide bold evidence of trilobite defensive postures and unprecedented evolutionary advances. Recently-detected signs of fossilized eggs, crawling appendages and gut tracks have afforded both scientists and collectors with previously unavailable and unimagined views into the long-gone world inhabited by these primitive arthropods.

Undeniably, on occasion a carefully prepared trilobite may too closely resemble a piece of contemporary sculpture, especially those specimens that sit pristinely perched upon a perfectly manicured pedestal of matrix. Such over-the-top examples of the prep process can even run the risk of completely removing that trilobite from its paleontological context and obliterating much of the fossil's intrinsic story. Indeed, totally isolating a specimen from any accompanying fauna, flora or sedimentary striation can often make that trilobite appear like a fish (or arthropod) out of water. 

Many of the recent trilobite examples emerging from Morocco and Russia have been subjected to this brand of drastic display, being presented as beautiful yet strangely disconnected creatures… works of art rather than scientifically significant specimens. But in stark contrast, some fossils - especially those showing multiple trilobites on a single slab, or those depicting these ancient animals interacting with starfish, bryozoans or crinoids within their undersea realm- present the story of prolific, active and sociable creatures, each fully integrated into their timeless aquatic environment.

So it seems safe to say that when taken collectively, each of the 25,000 species that arose during the trilobites' 270 million year swim through the Paleozoic possesses the capacity to reveal an amazing and unique story. Every trilobite fossil, from the most common Elrathia to the most exotic Probolichas, serves as a vital cog in the complex “machine” of evolution, and each tale they tell sheds new light on the darkest depths of deep time… the time when trilobites ruled the seas.