Utah Trilobites - America's Paleozoic Palace
Trilobites can be found just about anywhere. Though they generally remain rather elusive remnants of Earth's long-forgotten past, the fact is that these ancient arthropods are nothing less than pervasive. Look closely through the strata exposed by the next road cut you pass, or dig deep into the sedimentary outcrop near that local stream, and the possibility exists of finding evidence of these fossilized treasures literally in your own backyard.
No, we're certainly not saying that making such a discovery is either easy or common. But in the U.S. alone, Paleozoic deposits range from Lower Cambrian to Upper Permian, with many containing trilobites of various sizes, shapes and species. Trilobites can be found from New York to California, with a majority of the states in between chiming in with either an abundance of material or perhaps only an occasional find or two. And while a number of these states can lay claim to being the most bountiful trilobite locale in the country, without question, nowhere across the face of North America are trilobites more prevalent than in the rugged state of Utah. Ranging from the 510 million year old Middle Cambrian Wheeler shale through the 440 million year old Ordovician-age Fillmore formation, this mountainous western outpost brims with some of the most renowned and studied Paleozoic outcrops in the world.
The fact is that trilobite collecting in Utah enjoys a long and storied history. Indeed, going back to the 18th Century -- and perhaps even earlier -- the native Ute tribes would find strange “animals of stone” (actually Elarathia kingii trilobites) lying on the ground, drill holes in their pygidia and wear these half-billion year old fossils around their necks as good luck talisman. And while the Utes may have been the first to recognize the state's trilobites as something extraordinary, they certainly weren't the last.
Among the prominent names that subsequently searched for these primordial relics throughout Utah's majestic landscape was the seemingly ubiquitous Charles Walcott, who also played an essential role in the discovery and exploration of both British Columbia's famed Middle Cambrian Burgess Shale and New York's State's renowned Ordovician-age Walcott-Rust quarry. He frequently visited Utah between the years of 1885 and 1906, and it was Walcott who first named both the Wheeler and Marjum formations, noting the “alternating bands of thin-bedded limestone and calcareous shale” that characterized these fossil-rich outcrops.
Despite Walcott's initial efforts, however, it wasn't until the pioneering work of local resident Lloyd Gunther and his family in the 1930s that the state's Middle Cambrian trilobite bonanza began to be fully explored and recognized. The Gunthers' efforts first helped discover and identify such species as Hemirhodon amplipyge, which can grow up to 13 centimeters in length, and Bolaspadella housensis, a diminutive trilo-type that rarely exceeds a centimeter in size. Indeed, the work of the Gunther clan has continued on unabated for more than 80 years, with new generations of the family still working these central Utah layers (and others throughout the state) on a regular basis. In fact, Lloyd Gunther's son, Val, recently served as co-author of the well-received 2015 volume, Exceptional Cambrian Fossils From Utah.
However, the Gunthers are far from alone in their appreciation and pursuit of Utah's amazing array of trilobites. Among the most notable of these new-breed enthusiasts is Terry Abbott, a full-time commercial fossil collector based in the small town of Delta, who considers himself “blessed” to be living in the midst of some of the most famous and abundant trilobite outcrops on earth. Indeed, Abbott revels not only in the history of the state's trilobites, but also in the geologic history of the state itself. He is well aware that back in the Middle Cambrian, this now mostly arid inland region was part of a great ocean shelf located off of Laurentia, the supercontinent which then lay near earth's equator. In those warm tropical seas, early life proliferated amid the shallow-water reefs.
At that long-distant time in earth history, Utah's now-mountainous terrain was actually the floor of a shallow sea where these early denizens of the deep existed in what was ostensibly an offshore estuary. Trilobites of all imaginable (and unimaginable) types swam through these waters, along with an array of soft-bodied arthropods, which recent discoveries indicate rivaled those found in any other Cambrian location on the planet in terms of their abundance and diversity. Nearly two hundred trilobite species have so-far been identified from the state's Cambrian layers alone, along with a variety of worms, lobopods and other athropods, including Anomolocaris sp. and Beckwithia typa. All of these creatures eventually ended up as part of the ecosystem at the bottom of this rich oceanic environment. There, following their demise, they were covered with sediment, which over the ensuing eons formed thick limestone and mudstone layers that half a billion years later would yield some of the most prolific Paleozoic fossil sites ever discovered.
Over the last three decades, Abbott has explored many of Utah's renowned trilobite localities, especially those of the Middle Cambrian House Range, which includes both the Marjum Formation (home of such rare collector's favorites as Olenoides nevadensis and Glossopleura gigantea) and the slightly more recent Wheeler shale where specimens of the abundant trilobites Elrathia kingii and Asaphiscus wheeleri have become staples in every beginner's fossil collection.
More recently, however, Abbott's travels have carried him to exciting new Utah locales. There he has begun uncovering an amazing array of complete Cambrian and Ordovician age trilobites. Many of these had been known previously only through bits and pieces collected over the years by university scientists during brief surface explorations. Of particular interest have been a variety of trilobite species found in the Lower Ordovician Fillmore Formation, a fossil-rich limestone where the molted shells of larger specimens (which judging by the fragmentary evidence, apparently could have attained sizes of 12 inches, or more) were apparently torn apart by near-constant sub-surface storms, leaving only smaller complete examples, usually two inches or less, to be uncovered.
Abbott is quick to downplay either the scientific significance or the potential commercial windfall of his finds, preferring to focus more on the pure excitement of discovery. But even after spending most of his adult life in pursuit of these often elusive fossil finds -- which often carries him to way-off-the-map locales deep in the heart of Utah's often dizzying array of canyons and arroyos -- he has been pleasantly surprised by the positive response his work has received from both collectors and cooperative members of the scientific community.
"Professor Dick Robison from the University of Kansas has been out digging with me a number of times," Abbott said. "In fact, he's about the only person, other than my wife, who I've allowed into my latest site. I always let him keep the first complete specimens we find, and I hope they prove to be significant to his future studies. I believe the scientists and the collectors have got to work together whenever possible."
Abbott's good-natured attitude towards collecting has played a major role in yielding a bumper crop of trilobite "trophies" both for himself and his scientific comrades. Among the finds that he has made over the last few years are complete examples of such unusual Ordovician species as Kanoshia kenoshensis, Hintzia aemula, Pseudeocyble lemurei, Presbynelius ibexensis Ptycephalus yersini and Isotelodies flexus -- all species previously known to science, but rarely, if ever, as articulated specimens. His Cambrian discoveries have included Utaspis marjumensis, Tricrepicephalus coria, Olenoides superbus (highlighted by spines running down it's axial lobe) and a new species of Modociafeaturing strange, bulbous nodes emanating off of each thoracic segment.
Of course, not every specimen Abbott uncovers is rare or perfect. He admits to finding examples of incomplete or more common species at approximately a 100 to 1 ratio to his more exotic discoveries. Apparently, patience and persistence are two virtues a good trilobite collector must have in abundance during their field excursions. In fact, Abbott reveals that a good day's work under the hot Utah summer sun may yield only one or perhaps two complete specimens, while he can recall too many occasions when he made the three-to-six hour drive home with nary a “keeper” to show for his back-breaking efforts. But, somewhat surprisingly, this is one adventurer who seems to derive almost as much pleasure from uncovering a relatively well-known species (as long as it's in good condition) as he does from unearthing a one-of-a-kind "treasure".
"If your only goal is to find unique specimens, or previously unknown species, you're gonna be disappointed most of the time," Abbott explained. "I'm not saying I don't love finding special trilobites. But I really do get almost as much of a thrill from each trilobite I find."
At the moment, Abbott has yet to find an adequate number of the rarest trilobite species to make them commercially available to collectors. He has, however, marketed approximately two dozen examples of the encrinurid Pseudocyble lemurei, to enthusiasts around the globe. Abbott, however, would much rather spend his time in the field uncovering new trilobite locations then “wasting time” in the marketing of his finds, something he views as little more than an economic necessity.
In light of some of the recent actions taken by the federal government, Abbott is very aware of where he can, and where he can't dig. The passing of the 2009 Omnibus Land Management Bill has further refined his collecting options, now ostensibly making the digging of any fossil on federal land a potential crime. Though he has managed to procure a number of land leases from the government over the years, some of his favorite trilobite locations now fall on federal land, strictly controlled by the Bureau of Land Management (BLM). While admitting his frustration at what he perceives as increased government intervention, Abbott has reacted in kind by redirecting his collecting focus upon either state-controlled land (where the collecting of limited numbers of invertebrate fossils is still legal) or his own leased quarries.
“I don't let too many things get in my way,” he said with a sly smile. “All I want to do is what I love, which is digging for trilobites… while obeying the law.”
Each morning when the bright Utah sun reaches over the nearby Drum Mountains and begins to shed its light on the surrounding hillsides, Abbott's thoughts immediately turn towards hopping into his all-terrain vehicle and getting his hands dirty out in the field. He knows that each day could be the day; the one when he finds the trilobite mother lode -- the place where a collector's dreams are made. And whether he uncovers a single trilobite that day, or fifty, he knows that his thirst to find these special remnants of earth's long-forgotten past will never be fully quenched. Terry Abbott knows that there will always be a bigger, better, rarer specimen waiting for him just under that next layer of rock.
Val Gunther (front, white hat) enjoys a trilobite dig in Utah's House Range.