From warm tidal estuaries to cool off-shore continental shelves, during their nearly 300 million year trek through evolutionary time trilobites filled virtually every available oceanic niche. Today, some 250 million years after their demise, evidence of their incredible success—which produced over 25,000 recognized species—can be seen in geologic formations around the globe. Their fossilized remains are found in the rugged mountains of western Canada, the rolling plains of eastern Europe, the scorching deserts of northern Africa and the verdant hills of southern China. Indeed, trilobites can be discovered on every continent on earth where Paleozoic outcroppings exist.
Amid their worldwide presence in sedimentary rock ranging in age from Cambrian to Permian, there are a select number of trilobite locales that have gained renown from both scholars and collectors for the diversity, beauty, and scientific significance of their fauna. Whether it's the Silurian Wren's Nest in the English midlands or the Ordovician Walcott-Rust quarry in upstate New York, each of these sites presents a unique and fascinating window upon an ancient world. Here, we present comprehensive essays about these historic sites, along with photo galleries designed to highlight many of the magnificent trilobite specimens that hail from these diverse locations.
(All Trilobite Localities text copyright Andy Secher)
The map below denotes the present day location of the key trilobites sites discussed here.
North America
The Rochester Shale
The fossils of The Rochester Shale were originally excavated during the construction of the Erie Canal, between 1817 and 1825. Accordingly, some of the earliest scientific descriptions of these ancient animals were from this locality. The Rochester Shale has long been famous for its quality of preservation and abundance of invertebrate life, with more than 200 described species, including Corals, Bryozoans, Brachiopods, Bivalves, Gastropods, Cephalopods, Conularians, Graptolites, a Machaeridian worm, Crinoids, Cystoids, Brittle Stars, Starfish, Edrioasteriods, and of course, Trilobites.
Rust Formation, Trenton Group (Walcott Rust Locality)
The fine-grained limestone beds that comprise the Walcott-Rust quarry are renowned for their numerous exquisitely preserved trilobites and other invertebrates and have the distinction of yielding the first trilobites for which appendages were definitively described by Walcott in 1876-77. At least 18 species of trilobites have been documented, often associated with other fauna consisting of 11 described species of crinoids, one paracrinoid, brachiopods, bryozoans, one rhombiferan, two carpoids, two asteroids, one ophiuroid, and one edrioasteroid. Brett et al (1999) concluded that the "Walcott-Rust Quarry is the single richest and most varied source of trilobites in the New York Trenton Group limestones and perhaps in the entire suite of New York Paleozoic rocks."
Few trilobite sites in the world have continually stirred the souls of collectors more than the Silica Shale of Sylvania, Ohio. For over a century, this Devonian-age quarry has been noted for its fossil-rich fauna, which in addition to countless pyritized brachiopods and an array of coral calices and crinoid stems, features three trilobite species -- two types of phacopid (Eldredgeops milleri and Phacops rana crassituburculata) and one proetid (Dechenella lucasensis). But it is not the rather limited number of trilobite species found within the quarry's coarse mudstone matrix that excites collectors. Rather, it is thespectacular preservation of the trilobites found here—wonderfully three-dimensional examples covered in a thick, chocolate-brown or charcoal-grey calcite that seems to capture every nuance of trilobite dorsal morphology. Unquestionably the most alluring aspect of that morphology is each trilobite's huge compound eyes, magnificently preserved with every optic lens and geometric detail intact. With a little imagination, those eyes almost appear to be staring back at you, providing a dramatic link to life more than 400 million years in the past.
Located near the town of Clarita in the south-central region of Oklahoma, the fossil-rich Devonian sediments of the Haragan formation have, over the last three decades, produced a dizzying array of magnificent, three-dimensional trilobite specimens. A rich caramel color and often featuring spinous ornamentation (most notably on the species Dicranurus hamatus and Ceratonurus sp.),these 417 million year old trilobites rank as favorites of both museum curators and amateur collectors world-wide. Indeed, some 20 species are known from the Haragan and its sister formation, the Bois d'arc, making this mountainous, semi-arid region of Oklahoma one of the most prolific trilobite locations in North America. Virtually all of the Devonian trilobite material emerging from the area has been generated through the hard work of one man, Bob Carroll. Since the mid-'80s, Carroll has almost single-handedly operated the principal Haragan Formation quarry. During that time he has found and prepared thousands of the complete trilobite specimens which have come forth from the region's soft, yellow limestone, subsequently turning many of these ancient arthropods into true works of art.
Perhaps nowhere else on the North American continent are trilobites more prevalent than in the majestic state of Utah. Ranging from the 510 million year old Middle Cambrian-age Wheeler shale through the 440 million year old Ordovician-age Fillmore formation, this western outpost brims with some of the most renowned and studied Paleozoic outcrops ever discovered. The region's Cambrian trilobites include such familiar species as Olenoides nevadensis, Modocia typicalis,Hemirhodon amplipyge, as well as the World's Most Common Trilobite—the pervasive Elrathia kingii. Ordovician species include Pseudeocyble lemurei, Presbynileus ibexensis, Ptyocephalus yersini, and Isotelodes flexus. Yet for all the paleontological work that has been done in Utah over the last 150 years, hidden amid the countless canyons and valleys that cut through the Drum, House, and Wellsville mountain ranges are still virgin fossil-bearing locations—along with a corresponding array of new trilobite species—that are being discovered on a regular basis.
The 518 million year old Latham Shale, located near the heart of the imposing Mojave Desert in San Bernardino County, California, represents one of the finest Lower Cambrian outcrops in North America. Found within its rust-colored limestone layers are a variety of rare trilobite species, including an intriguing assortment of Olenellid types. Taken together with the other assembled fauna, these trilobites provide an unparalleled view of what a typical reef-filled offshore environment may have been like at this early stage of life's development on earth. Housed within the often inhospitable Marble Mountains, the Latham Shale's rich deposits have so-far produced evidence of 12 different trilobite species, such as Bristolia bristolensis and Olenellus fremonti, which when preserved as complete examples can range between two and five inches in length.
One of the most prolific Silurian trilobite zones in North America can be found beneath the rugged yet picturesque landscape of remote Anticosti Island, Quebec. Surrounded by the surging waters of the Gulf of St. Lawrence, it takes a hearty soul to reach this densely forested, decidedly out-of-the-way locale. But such a venture is apparently well worth the effort for those with a true Paleozoic passion. Not only are the 6,000 foot thick sedimentary layers of Anticosti bursting with fossils—in some spots they're quite literally falling out of the cliff-sides—but many of the trilobite specimens so-far discovered, including Diacalymene schucherti, Failleana magnifica and Arctinurus anticostiensis, provide solid evidence that back some 430 million years ago this was a mega-fauna, one filled with trilobites of unusual size and spectacular preservation. After a major 2004 scientific revision, 52 species have now been recognized from Anticosti's rich Silurian layers, comprising an impressive 30 genera. And while material from such formations as the Jupiter and Ellis Bay may not be as well known to either scientists or collectors as trilobites from more renowned North American locales, as more academic and commercial expeditions head to this craggy outpost, Anticosti Island's status as a trilobite haven seems destined to steadily increase.
Burgess Shale, Stephen Formation, British Columbia
No other invertebrate locale on the planet enjoys either the mystique or mainstream media focus of the Burgess Shale. There, high up in the Canadian Rockies stands the Stephen formation, its shale filled not only with trilobites, but also with an amazing array of soft bodied creatures which together provide a special look at a Middle Cambrian world that existed over half a billion years ago. This remote site in British Columbia was first discovered in 1886, and subsequently worked by the legendary Charles Walcott in the early years of the 20th Century. Since then, the Burgess Shale has been the subject of intense (and ongoing) scientific research as well as serving as the springboard for dozens of books, internet reports and TV specials dedicated to trying to decipher the riddles of life on earth soon after the Cambrian Explosion began. In 1981, UNESCO recognized the importance of the Burgess Shale locale, declaring it a World Heritage Site, protecting this amazing fauna for future generations.
Since the mid-19th Century, a unique group of trilobites have been recognized from a small number of Devonian formations that ring the outskirts of La Paz, Bolivia. Almost always found in hard limestone concretions, these 370 million year-old fossils have long been a favorite of trilobite collectors around the globe as well as the subject of intense scientific study. Dozens of species have been identified from these zones, with various calmonids, lichids, and homalonotids among them. The formations that produce these specimens are located at a height of 12,000 feet above sea level, in the Bolivian altiplano, making them among the most inaccessible and intriguing trilobites in the world.
Key segments of Portugal's 450 million year-old Valongo Formation represent a megafauna that has produced some of the largest trilobite specimens ever found, many up to 15 inches in length. Since the late 19th Century, both commercial workmen and local residents near the town of Arouca have quarried the area's Ordovician-age slate blocks primarily for use as roofing and paving tiles. On occasion, however, the quarrying operation has hit upon layers that have yielded trilobites of prodigious size… and often in prodigious numbers. Appearing as ghostly white images that contrast dramatically against the jet black shale, nearly 100 trilobite species have so-far been described from the Valongo Formation, and many of these have become world renowned for their beauty, size and scientific importance.
The fossil-rich Silurian exposures of the English midlands have been yielding amazing trilobite specimens for centuries, with those coming from the Wenlock limestone formations near the town of Dudley rating among the most beautiful and renowned in the world. In fact, one particular species, Calymene blumenbachi, has become so synonymous with the area that Dudley's town crest proudly boasts an illustrated version of the fossilized local “locust”. Over 80 trilobite species have been discovered and described from the area's most famous collecting locale, Wren's Nest, where the 420 million year-old strata has produced hundreds of magnificently preserved complete specimens. Now designated as a Site of Special Scientific Interest (where digging for fossils is prohibited), Wren's Nest remains one of the most studied and storied of European fossil locales.
Perhaps no trilobite location on Planet Earth possesses more Paleozoic panache than the Czech Republic's legendary Jince Formation—a series of predominantly Middle Cambrian outcrops that cover roughly two hundred square miles in the heart of what was once known as Bohemia. Much of the formation's notoriety stems from the groundbreaking efforts performed in that area nearly two centuries ago by French naturalist Joachim Barrande. During nearly 40 years of work, Barrande discovered and described dozens of trilobite species—including Paradoxudes gracilis, Conocoryphe cirina, and Ellipsocephalus hoffi. Many of these discoveries served as the centerpiece for his historic work, Systeme Silurien du Centre de la Boheme, a volume that would come to influence many… including Charles Darwin.
Soon after the fall of communism in the late-'80s, a veritable onslaught of trilobite specimens began emanating out of the Volkhov River region near St. Petersburg, Russia, and onto world stage. The preponderance of this material was being drawn from a 70-foot thick geological layer known as the Aseri Horizon, which had formed 450 million years ago when this area of Europe was still covered by a warm inland sea. These Ordovician-age trilobites were noteworthy for their thick, caramel-colored calcite shells as well as their exceptionally three-dimensional preservation. Some specimens featured exotic shapes and sizes while others presented carapaces covered by an array of pointed spines. Equally as impressive, many of the over 100 trilobite species that have so far been discovered and described from this horizon had previously been unseen by the scientific community…. at least at this level of completeness. By the mid-'90s, these magnificent arthropods were being marketed at fossil shows and exhibited in museums, with one in particular—Neoasaphus kowalewski—drawing particular attention due to the fact that it featured eyes sitting atop stalks over two inches long.
Carboniferous / Permian Trilobites, New Mexico & Kazakhstan
Trilobites were among the most successful creatures ever to exist on earth. Their march through evolutionary time began back in the Lower Cambrian, some 521 million years ago, and lasted for nearly 270 million years, until the end of the Permian, 252 million years ago. During this unfathomable length of time (which ostensibly bookends the entire Paleozoic Era), these highly adaptable arthropods filled virtually every available aquatic niche while producing over 25,000 scientifically recognized species. Certain localities around the world—including key Carboniferous (Mississippian & Pennsylvanian) and Permian outcrops in New Mexico, Kazakhstan, Belgium, and China—have produced fossilized examples of the diminutive proetida order, usually an inch or less in size, that represent the last members of the noble trilobite dynasty. And while these end-of-the-line trilobites apparently filled a wide variety of oceanic habitats—ranging from deep open water to shallow continental shelves—their versatility wasn't enough to save them from their eventual fate. As life on our ever-changing planet has continually proven, nothing lasts forever, and for reasons that continue to both confound and fascinate scientists, the end of the Permian also signaled the end of trilobites…along with 90 percent of life around the globe, an event which represents the greatest mass extinction in the history of Planet Earth.
Cambrian Trilobites, Lena & Anabar Rivers, Siberia
Cutting for nearly 600 miles on a south-to-north path through the heart of the Sakha Republic in distant Siberia are the Lena and Anabar Rivers. On their own merit, these closely aligned bodies of water would most likely retain their relative anonymity upon the global stage. However, the fact that some of the world's oldest trilobites have been discovered in the 520 million year-old sedimentary outcrops carved out by these waterways makes them of particular interest to both paleontologists and trilobite enthusiasts around the globe. With trilobites in these formations ranging in size from the diminutive Delgadella lenaica, which rarely exceeded 1 cm, to the large Jakutus primigenius which often attained lengths of 12 cm, or more, it is clear that these were diverse and advanced faunas, especially considering how early they appear in the trilobite record. Indeed, perhaps the first trilobite in the entire fossil lineage, Profallotaspis jakutensis, has been documented in adjacent Siberian mudstone layers, marking this remote outpost as one of unique paleontological significance.
Over the last two decades, Morocco has emerged as the somewhat unlikely epicenter of world-wide trilobite discoveries. From Lower Cambrian Fallotaspids (the first recognized trilobites, over 520 million years old) through an incredible array of unusual Devonian species—many featuring outlandish spines and multi-faceted eyes—the sedimentary strata of North Africa has provided a veritable bonanza of bizarre trilobite types. Dozens of previously unknown species have emerged from the rich Paleozoic formations of Morocco, many requiring the delicate work of preparation artisans to free the specimens from their eons-old rock encasements. And while a dearth of scientific research has been done on the preponderance of material so-far found, there are a growing number of paleontologists around the globe who have recently begun to tackle this daunting, yet fascinating task.
In 1984, a thousand years after these layers were first noted, Chinese scientists formally described an amazing 515 million year old Lower Cambrian fauna located within the Maotianshan Shales of Chengjiang County in China's southern province of Yunnan. There, mixed amid a variety of primitive trilobite species including Eoredlichia intermedia, Yunnanocephalus yunnanensis, Wutingaspis tingi and Kauyangi pustulosa, were an astounding assortmentof soft-bodied creatures, many of which resembled those found in the legendary—though 5 million years more recent—Burgess Shale of British Columbia, Canada. Material from the Chinese site (which along with a number of other similarly-aged local layers, including the Chiungchussu and Qionzhusi Formations, have become collectively recognized as the Chengjiang Biota) had been known as early as the 10th Century. It wasn't until scientific expeditions began exploring the area in late 1970s, however, that research began to unravel the myriad scientific mysteries that lay within these 50-meter thick hard mudstone layers. So far, 185 different species (with over half being arthropods) have revealed themselves in the Chengjiang Biota, with the possibility that even more are still hidden within these ancient rocks, waiting to be discovered.
The Emu Bay Shale of Kangaroo Island, South Australia, ranks among the world's most significant Lower Cambrian deposits. With an age and fauna older than that of the renowned Burgess Shale of British Columbia, Canada, these 510 million year-old layers are filled with a variety of Burgess-like soft-bodied creatures as well as such stratigraphically important trilobite species as Estangia bilobata, Redlichia takooensis and Balcoracania dailyi. The Emu Bay Shale is believed to have once been part of a semi-tropical, shallow sea environment, which contrasts it to the cool, deep-water environs proposed for both Burgess and China's similarly ancient Chengjaing formation. Aided by its unusual and rather isolated geographical location back in the Cambrian, a number of the Emu Bay's trilobite species developed remarkable morphological features—with the fossilized remains of Balcoracania dailyi in particular, displaying more than 60 distinct body segments, the most of any known trilobite.
From the snow-covered peaks of western Canada to the dry desert outposts of Morocco, great trilobite specimens can be found just about everywhere across the face of Planet Earth. We've already presented detailed reports on many of the world's most significant Paleozoic sites, but here are brief overviews of a dozen additional important trilobite-bearing locations, listed in order of their geological age. If nothing else, their mere mention provides us with an excuse to show you a few more interesting photos of the world's favorite fossil arthropod.
