Trilobites are extinct marine arthropods that belong to the class Trilobita. They were among the first arthropods to appear in the fossil record and were very successful, living in oceans for about 270 million years. Over 22,000 species of trilobites have been discovered. Trilobites had a wide variety of body shapes and a hard, calcite-based exoskeleton that made them easy to fossilize. This has left behind a large number of fossils, which have helped scientists study areas such as biostratigraphy, paleontology, evolutionary biology, and plate tectonics. Trilobites are part of the clade Artiopoda, which includes many similar organisms that are mostly not mineralized. Scientists are still unsure how Artiopoda relates to other arthropods.
Trilobites lived in many different environments. Some crawled along the ocean floor as predators, scavengers, or filter feeders, while others swam and ate plankton. Some trilobites even moved onto land. Most behaviors seen in modern marine arthropods were also present in trilobites, except for parasitism, which is still debated by scientists. Some trilobites, like those in the Olenidae family, may have formed a relationship with sulfur-eating bacteria, using them for food. The largest trilobites were over 70 centimeters long and could weigh up to 4.5 kilograms.
The first trilobites appeared in the fossil record around 521 million years ago, marking the start of the Atdabanian/Cambrian Stage 3 period in the Early Cambrian. Soon after their appearance, trilobites were widespread and diverse. Their diversity peaked during the late Cambrian and Ordovician periods and remained high during the Silurian and early Devonian. However, their diversity declined during the mid- to late Devonian due to several extinction events, including the Taghanic event, the Late Devonian mass extinction (Kellwasser event), and the Hangenberg/end-Devonian mass extinction. These events nearly wiped out all trilobites, leaving only the Proetida order. Their diversity slightly increased during the Early Carboniferous but dropped again during the late Carboniferous and Permian periods. Trilobites remained common until the end-Permian mass extinction, which occurred about 251.9 million years ago. By this time, only a few species remained.
Evolution
Trilobites belong to the Artiopoda, a group of extinct arthropods that look similar to trilobites. However, only trilobites had heavily mineralized exoskeletons. Other artiopodans are usually found only in deposits that are exceptionally well preserved, mostly from the Cambrian period.
The exact relationships of artiopods to other arthropods are not fully understood. Some scientists believe they are closely related to chelicerates (which include horseshoe crabs, sea spiders, and arachnids) as part of a group called Arachnomorpha. Others think they are more closely related to Mandibulata (which includes insects, crustaceans, and myriapods) as part of a group called Antennulata.
Cladogram of Artiopoda including trilobites after Berks et al. 2023.
The earliest trilobites found in the fossil record are redlichiids and ptychopariid bigotinids, dated to about 520 million years ago. Possible candidates for the earliest trilobites include Profallotaspis jakutensis (Siberia), Fritzaspis spp. (western US), Hupetina antiqua (Morocco), and Serrania gordaensis (Spain). Trilobites appeared around the same time in Laurentia, Siberia, and West Gondwana.
All Olenellina lack facial sutures (see below), and this is thought to be the original state. The earliest sutured trilobite found so far, Lemdadella, appears almost at the same time as the earliest Olenellina, suggesting trilobites originated before the start of the Atdabanian, but without leaving fossils. Other groups show facial sutures that were lost later, such as all Agnostina and some Phacopina. Another common feature of the Olenellina suggests this suborder is the ancestral trilobite stock: early protaspid stages have not been found, likely because these were not calcified, and this is thought to represent the original state. Earlier trilobites may be found and could provide more information about their origins.
Three specimens of a trilobite from Morocco, Megistaspis hammondi, dated 478 million years old, contain fossilized soft parts. In 2024, researchers discovered soft tissues and other structures, including the labrum, in well-preserved trilobite specimens from Cambrian Stage 4 of Morocco. This discovery provided new information about the external and internal anatomy of trilobites. The extraordinary preservation is likely due to the trilobites dying rapidly after an underwater pyroclastic flow.
Trilobites diversified greatly over time. As a long-lasting group, their evolutionary history includes many extinction events where some groups disappeared, and surviving groups diversified to fill ecological niches with unique or similar adaptations. Trilobites remained diverse throughout the Cambrian and Ordovician periods but began a slow decline in the Devonian, ending with the extinction of the last few survivors at the end of the Permian period.
Major evolutionary trends from early trilobite forms, such as Eoredlichia, include the development of new eye types, improved enrollment and articulation mechanisms, increased pygidium size (from micropygy to isopygy), and extreme spinosity in some groups. Changes also involved narrowing of the thorax and varying numbers of thoracic segments. Specific changes to the cephalon include variations in glabella size and shape, eye position, facial sutures, and hypostome specialization. Some features, such as eye reduction or miniaturization, appeared independently in different major trilobite groups.
Effacement, the loss of surface detail in the cephalon, pygidium, or thoracic furrows, is a common evolutionary trend. Examples include the orders Agnostida and Asaphida, and the suborder Illaenina of the Corynexochida. Effacement is thought to indicate a burrowing or pelagic lifestyle. This loss of detail makes it difficult for scientists to determine evolutionary relationships.
Although trilobites were once thought to have originated during the Precambrian, this is no longer supported. Instead, trilobites likely originated shortly before appearing in the fossil record. After their first appearance in the lower Cambrian, they quickly diversified into major orders, such as Redlichiida, Ptychopariida, Agnostida, and Corynexochida. The first major crisis in the trilobite fossil record occurred in the Middle Cambrian, when surviving orders developed isopygius or macropygius bodies and thicker cuticles for better predator defense. The Late Cambrian marked the peak of trilobite diversity. The end-Cambrian mass extinction event drastically changed trilobite populations, with most Redlichiida (including Olenelloidea) and many Late Cambrian groups becoming extinct. A decrease in Laurentian continental shelf area during this time suggests major environmental changes.
Notable trilobite genera from the Cambrian include:
The Early Ordovician is marked by the rapid expansion of articulate brachiopods, bryozoans, bivalves, echinoderms, and graptolites, many of which first appear in the fossil record. While trilobite diversity within species peaked during the Cambrian, they remained active participants in the Ordovician radiation, with a new fauna replacing the old Cambrian one. Phacopida and Trinucleioidea are characteristic forms, highly differentiated and diverse, with uncertain ancestors. Phacopida and other "new" groups likely had Cambrian ancestors, but their rapid development suggests new morphologies were emerging quickly. Changes in trilobite groups during the Ordovician foreshadowed the mass extinction at the end of the period, allowing many families to survive into the Silurian with little disruption. Ordovician trilobites successfully adapted to new environments, such as reefs. The Ordovician mass extinction affected trilobites, with some successful groups, like Telephinidae and Agnostida, becoming extinct. The Ordovician marks the last major diversification of trilobites, as few entirely new organizational patterns emerged after this period. By the end of the Ordovician, trilobite radiation had slowed, and a gradual decline began. The Ordovician
Fossil distribution
Trilobites were mainly ocean-dwelling creatures, as their fossils are always found in rocks that also contain fossils of other saltwater animals, such as brachiopods, crinoids, and corals. Some evidence suggests trilobites may have briefly moved onto land. In the ocean, trilobites lived in many environments, from very shallow water to extremely deep water. Like brachiopods, crinoids, and corals, trilobites are found on all modern continents and lived in every ancient ocean where Paleozoic fossils have been discovered. Fossils of trilobites can include their full bodies, parts of their exoskeletons (which they shed during molting), or the tracks they left on the seafloor, which are preserved as trace fossils.
Three main types of trace fossils are linked to trilobites: Rusophycus, Cruziana, and Diplichnites. These fossils show the activities of trilobites on the seafloor. Rusophycus are marks left when trilobites rested, hid, or hunted with little movement. Cruziana are furrows in sediment made by trilobites as they moved while feeding. Diplichnites are tracks left by trilobites walking on the sediment. Care must be taken, as similar fossils found in freshwater or later geological periods may not be from trilobites.
Trilobite fossils are found worldwide, with thousands of species identified. They appeared quickly in Earth’s history and molted like other arthropods, making them useful as index fossils. Geologists use trilobites to determine the age of rocks. They were among the first fossils studied widely, and new species are still being found today.
In the United States, a famous public trilobite collection is in Hamburg, New York. The site, called Penn Dixie, was a quarry that stopped operating in the 1960s. Trilobites were discovered there in the 1970s by Dan Cooper, a rock collector who raised interest in the location. The fossils are about 387 to 382 million years old, from a time when western New York was near the equator and covered by water. The town of Hamburg purchased the land to protect it from development. In 1994, the site became Penn Dixie Fossil Park & Nature Reserve, open to visitors and fossil collectors. The most common trilobites found there are Eldredgeops rana and Greenops.
In the United Kingdom, a famous trilobite site is Wren’s Nest in Dudley, West Midlands, where Calymene blumenbachii is found in Silurian rocks. This trilobite is on the town’s coat of arms and was once called the Dudley Bug by workers in old limestone quarries. Another site is Llandrindod Wells, Powys, Wales, where Elrathia kingi is found in Cambrian rocks in Utah, United States.
Well-preserved trilobite fossils, including soft body parts like legs and antennae, are found in places like British Columbia, Canada (Cambrian Burgess Shale), New York, USA (Ordovician Walcott–Rust quarry and Beecher’s Trilobite Bed), China (Lower Cambrian Maotianshan Shales), Germany (Devonian Hunsrück Slates), and Utah, USA (Wheeler Shale).
In Morocco, trilobites are often found perfectly preserved in mudslides, buried alive. This has led to an industry for recovering and restoring these fossils, which has caused debates about restoration methods. These fossils show a wide variety of eye shapes and body structures, similar to how bodies were preserved in Pompeii, Italy.
The French paleontologist Joachim Barrande studied trilobites in the Cambrian, Ordovician, and Silurian periods in Bohemia. He published the first volume of Système silurien du centre de la Bohême in 1852.
Importance
Niles Eldredge's research on Paleozoic trilobites near the Welsh-English border was important for developing and testing punctuated equilibrium as a way evolution happens.
Finding 'Atlantic' and 'Pacific' trilobite groups in North America and Europe suggested the Iapetus Ocean closed, forming the Iapetus suture. This helped support the theory of continental drift.
Trilobites are key to understanding how quickly new species appeared during the Cambrian explosion because they are the most varied group of animals found in early Cambrian fossils.
Trilobites are very useful for identifying Cambrian rock layers. Researchers who find trilobites with specific features, such as alimentary prosopon and micropygium, have identified Early Cambrian strata. Most Cambrian rock layer studies rely on trilobite fossils.
Trilobites are the state fossils of Ohio (Isotelus), Wisconsin (Calymene celebra), and Pennsylvania (Phacops rana).
Taxonomy
The 10 most commonly recognized trilobite orders are Agnostida, Redlichiida, Corynexochida, Lichida, Odontopleurida, Phacopida, Proetida, Asaphida, Harpetida, and Ptychopariida. In 2020, an 11th order, Trinucleida, was suggested to be moved up from the asaphid superfamily Trinucleioidea. Sometimes the Nektaspida are considered trilobites, but these lack a hard outer shell and eyes. Some scientists believe the order Agnostida may not be a single group with a shared ancestor, with the suborder Agnostina representing non-trilobite arthropods unrelated to the suborder Eodiscina. Under this idea, Eodiscina would be reclassified as a new order, Eodiscida.
Over 22,000 trilobite species have been identified.
Although trilobites have a large fossil record with thousands of genera found worldwide, their classification and evolutionary relationships remain uncertain. Except for the orders Phacopida and Lichida (which first appear in the early Ordovician), nine of the 11 trilobite orders existed before the end of the Cambrian period. Most scientists think the order Redlichiida, specifically its suborder Redlichiina, contains the common ancestor of all other orders, except possibly Agnostina. Many studies suggest the suborder Redlichiina gave rise to the orders Corynexochida and Ptychopariida during the Lower Cambrian, and the Lichida descended from either Redlichiida or Corynexochida in the Middle Cambrian. The order Ptychopariida is the most difficult to classify. In the 1959 Treatise on Invertebrate Paleontology, what are now members of Ptychopariida, Asaphida, Proetida, and Harpetida were grouped as Ptychopariida. In 1990, a subclass called Librostoma was created to include these orders, based on their shared trait of a natant (unattached) hypostome. The most recently recognized of the nine trilobite orders, Harpetida, was established in 2002. The origin of the order Phacopida is not clearly understood.
Morphology
When trilobite fossils are found, only their hard outer covering (called the exoskeleton) is usually preserved, and it is often incomplete. However, in a few special locations called Lagerstätten, scientists can also see soft body parts like legs, gills, muscles, and the digestive system. These sites also show details of other structures, such as the fine parts of the eyes. Out of the 20,000 known trilobite species, only 38 have fossils that show their appendages clearly.
Trilobites varied in size from very small, less than 1 millimeter (0.039 inch), to very large, over 70 centimeters (28 inches). The smallest known species is Acanthopleurella stipulae, which measured up to 1.5 millimeters (0.059 inch). The largest known trilobite, Isotelus rex, was 72 centimeters (28 inches) long. It was discovered in 1998 by scientists in Canada near Hudson Bay in rocks from the Ordovician period. Another trilobite, Hungioides bohemicus, found in Portugal in 2009, may have been as long as 86.5 centimeters (34.1 inches) when complete.
Only the top (dorsal) part of the exoskeleton is made of minerals like calcite and calcium phosphate, which form a lattice of chitin. This part curves around the bottom edge to create a small fringe called the "doublure." The appendages and soft underside were not made of minerals. The body is divided into three sections: the cephalon (head), thorax (body), and pygidium (tail).
Trilobites are a large group with about 5,000 genera, and their body shapes can be complex. Despite this, they have features that set them apart from other arthropods. These include a hard, chitinous exoskeleton shaped like an oval, divided into three longitudinal lobes (which gives them their name). They also have a large head shield (cephalon) that connects to the thorax, which is made of segments. The last segments of the thorax are often fused to form the tail shield (pygidium). When comparing trilobite species, scientists often look at the size and shape of the head's features.
During molting, the exoskeleton usually splits between the head and thorax, which is why many trilobite fossils are missing one or the other. On the head, lines called facial sutures helped the trilobite shed its old exoskeleton. Like lobsters and crabs, trilobites grew between molting and when their new exoskeleton hardened.
The head section (cephalon) of trilobites varies greatly in shape. A dome-like structure called the glabella sits beneath the head, where the stomach was located. The exoskeleton on the underside has few features, but the head often shows marks where muscles attached. A small, rigid plate called the hypostome is sometimes found on the underside of the head. This plate supported the mouth and stomach, which were toothless and faced backward.
The hypostome has different forms. Sometimes it is supported by a soft membrane, sometimes it is fused to the front edge of the doublure, and sometimes it has a shape different from the glabella. Changes in the size of the glabella, the shape of the head's edges, and the hypostome are linked to different lifestyles, diets, and environments.
In some trilobites, the front and sides of the head are greatly expanded, while in others, a bulge near the glabella suggests a brood pouch. Complex compound eyes are another notable feature of the head.
Facial sutures are the natural lines on the head that helped trilobites shed their old exoskeleton during molting. All trilobites in the suborder Olenellina, which went extinct at the end of the Early Cambrian period, did not have facial sutures. These trilobites are considered the earliest ancestors of later trilobites. Some later trilobites also lost facial sutures, and the type of sutures found in different species is used to classify and study their evolutionary relationships.
The top of the head (cephalon) can be divided into two parts: the cranidium (central part) and the librigena (free cheeks). The cranidium includes the glabella (central lobe) and the fixigena (fixed cheeks). Facial sutures are located along the front edge, where the cranidium and librigena meet.
On the top of the head, facial sutures can be grouped into five main types based on where they end relative to the genal angle (the point where the side and back of the head meet). The most basic type is proparian. Opisthoparian sutures evolved multiple times independently, and proparian sutures never developed in groups with opisthoparian ancestry. Some trilobites with opisthoparian sutures as adults had proparian sutures as juveniles. Hypoparian sutures also evolved independently in several groups.
The path of facial sutures varies greatly, but the lack of a clear reference point like the genal angle makes it hard to classify them. In some trilobites, such as the Asaphida, the sutures meet in front of the glabella and split along the middle of the head. In others, like Triarthrus and the Phacopidae, the sutures meet completely, forming yoked free cheeks. In the Phacopidae, however, these sutures are not functional because the free cheeks are not separated from the cranidium.
There are two types of sutures connected to the compound eyes of trilobites. These include:
- Dorsal facial sutures that extend downward to the underside of the head, where they become connective sutures that divide the doublure.
- Ventral sutures that are further classified into types based on their position and structure.
The rostrum (or rostral plate) is a part of the doublure at the front of the head. It is separated from the rest of the doublure by the rostral suture. During molting in trilobites like Paradoxides, the rostrum helps anchor the front part of the trilobite as the cranidium separates from the librigena. The opening created by the body's movement allows the trilobite to escape the old exoskeleton. The rostrum is absent in some trilobites, such as Lachnostoma.
The hypostome is a hard structure near the mouth on the
Soft body parts
Only about 21 species of trilobites have soft body parts preserved, so some details, such as the tail-like structures found only in Olenoides serratus, are hard to study in other trilobites.
Trilobites had one pair of antennae before their mouth and limbs that were not clearly divided into parts. These limbs included four pairs on the head, one pair on each segment of the body, and some on the tail. Each walking leg had six or seven sections, similar to those of other early arthropods. These legs were attached to a part of the body called the coxa, which also had a feather-like gill used for breathing and, in some species, swimming. A 2021 study showed that the upper part of the trilobite’s limb acted like a well-developed gill, helping to move oxygen into their blood, much like the gills of modern horseshoe crabs. In Olenoides, the way the leg connected to the body was different from the gills of spiders or crabs. The inside of the coxa had spines, likely used to handle food. The last part of the gill often had claws or spines. Many trilobite legs had tiny hairs, suggesting they helped with feeding or sensing movement.
Trilobites had a toothless mouth located at the back of a structure called the hypostome, just in front of the legs on their head. The mouth connected to a short tube leading to the stomach, which was below the central part of the head. From there, food moved backward to the tail. Limbs on the head may have helped push food into the mouth, possibly cutting it with the hypostome or spines on the coxa. A recent study using advanced imaging of Bohemolichas incola showed many pieces of shells from a small, extinct species called Conchoprimitia osekensis in its digestive system. These shell fragments suggest B. incola crushed hard shells to eat them. Since the shells were not identified by species but by their strength and size, B. incola likely ate whatever was available, like scavengers. These findings support the idea that early trilobites may have had glands that released enzymes to help digest food.
While scientists have evidence about the mouth, stomach, and digestive system, there is little direct proof of a heart, brain, or liver, though many drawings include these organs.
Although rare, long muscles ran from the head to the middle of the tail, helping the trilobite curl up for protection. Other muscles on the legs helped move them out of the way during this process.
Sensory organs
Many trilobites had complex eyes and a pair of antennae. Some trilobites were blind, likely because they lived in deep ocean areas where no light could reach. These trilobites became blind over time through a process called secondary blindness. Other trilobites, such as Phacops rana and Erbenochile erbeni, had large eyes that helped them see in bright, dangerous waters filled with predators.
The antennae found in most trilobites (and preserved in some fossils) were flexible, allowing them to be pulled back when the trilobite curled into a ball for protection. One species, Olenoides serratus, had antenna-like structures called cerci that extended from the back of its body.
Even the earliest trilobites had compound eyes made of calcite, a type of mineral. This shows that eyes in arthropods and possibly other animals may have developed before the Cambrian period. Better eyesight for both predators and prey is thought to have pushed the rapid evolution of many life forms during the Cambrian explosion.
Trilobite eyes were usually compound, with each lens shaped like a long prism. The number of lenses varied: some trilobites had only one lens, while others had thousands in a single eye. In compound eyes, lenses were often arranged in a hexagonal pattern. Fossil records of trilobite eyes are detailed enough to study their evolution over time, which helps scientists understand how these eyes changed, even though soft body parts rarely preserve.
The lenses in trilobite eyes were made of calcite (calcium carbonate, CaCO₃). Some trilobites used clear, precisely aligned calcite crystals to form each lens. These rigid lenses could not adjust focus like the soft lenses in human eyes. However, some trilobites had a special double-layered calcite structure that improved vision, as discovered by scientists René Descartes and Christiaan Huygens in the 17th century. A modern animal with similar lenses is the brittle star Ophiocoma wendtii.
In other trilobites, lenses lacked the Huygens interface, so scientists suggest they used a gradient-index lens, where the lens’s refractive power changed toward the center.
Some phacopid trilobites had sensory structures under their eyes. These structures included groups of sensory cells around a rhadomeric shape, similar to those found in modern arthropods like horseshoe crabs (Limulus).
Secondary blindness was common in long-lived trilobite groups, such as Agnostida and Trinucleioidea. In groups like Proetida and Phacopina from western Europe, and especially in Tropidocoryphinae from France, studies show that closely related species gradually lost their eyes over time, eventually becoming blind.
Other trilobite features, such as "macula" (thin areas on the underside of their hypostome), may have acted as simple "ventral eyes" to detect light or help them navigate while swimming upside down.
Some structures on trilobites, like the prosopon, are thought to have sensed chemicals or vibrations. For example, the large pitted fringes on the heads of Harpetida and Trinucleoidea may have functioned as "compound ears," especially since these species often had small or no eyes.
Development
Trilobites grew through stages called instars, which occurred after they shed their old shells. During the anamorphic phase, existing body parts grew larger, and new trunk segments formed in a specific area. This was followed by the epimorphic phase, where the trilobite continued to grow and molt, but no new trunk segments appeared. Together, these two growth methods form a pattern called hemianamorphic development, which is common in many living arthropods.
Trilobites had a unique way of forming joints between body segments. These changes in joint development helped scientists identify three main stages in the trilobite life cycle, which are different from those of other arthropods. Growth and changes in shape happened when trilobites were soft-bodied, right after molting and before their new shell hardened.
Trilobite larvae are known from the Cambrian period to the Carboniferous period and exist in all sub-orders. Instars from closely related species look more similar than those from unrelated species, which helps scientists study how trilobites are related to one another.
Although no fossils show direct evidence, trilobites are believed to have reproduced sexually and laid eggs. Some species may have carried their eggs or larvae in a special pouch near the front of their body, especially in difficult environments. The size and shape of the first hardened shell stage vary between trilobite groups, suggesting some species developed more inside the egg than others. Early stages before the shell hardened may have existed, but this is not certain.
The earliest known post-embryonic growth stage of trilobites is called the "protaspid" stage. This stage begins with a head and tail that look the same and ends when a line separates them. New segments form at the back of the tail, but all segments stay joined together.
The "meraspid" stage is marked by the development of a joint between the head and the fused body segments. Before this stage, the trilobite had a head and a fused body plate. During the meraspid stage, new segments form at the back of the body, and joints develop at the front, allowing segments to move freely in the thorax. One segment usually forms per molt, though sometimes two or one every other molt. Growth during this stage was significant, increasing size by up to 30%–40%.
The "holaspid" stage begins when the trilobite has a stable number of thoracic segments. Moulting continued during this stage, but no new segments formed. Some trilobites may have kept growing throughout their lives, though more slowly after reaching maturity.
Some trilobites showed a major change in body shape during one instar, called "trilobite metamorphosis." This change involved losing or gaining features that helped them adapt to new lifestyles. Changes in lifestyle during development could affect how well trilobites survived and spread. For example, trilobites that lived as plankton only during their early stages and later became bottom-dwellers did not survive the Ordovician extinctions, while those that only lived as plankton briefly survived.
There is no evidence that trilobites reabsorbed their old shells during molting. Some scientists believe that trilobites did not reabsorb their hardened shells, which made it harder and slower to build new shells. This may have made them more vulnerable to predators compared to modern arthropods that do reabsorb their old shells.
History of usage and research
In 1698, Rev. Edward Lhwyd wrote about his findings in 1698 in a scientific journal called The Philosophical Transactions of the Royal Society, the oldest scientific journal in English. His letter, titled "Concerning Several Regularly Figured Stones Lately Found by Him," included a page of etchings showing fossils. One etching depicted a trilobite he discovered near Llandeilo, likely on the grounds of Lord Dynefor’s castle. He described it as "the skeleton of some flat Fish."
In 1749, Charles Lyttleton discovered a fossil later named Calymene blumenbachii (the Dudley locust), which is considered the start of trilobite research. In 1750, Lyttleton sent a letter to the Royal Society of London about a "petrified insect" he found in "limestone pits at Dudley." In 1754, Manuel Mendez da Costa stated that the Dudley locust was not an insect but part of the "crustaceous tribe of animals." He named it Pediculus marinus major trilobos (large trilobed marine louse), a name used until the 19th century. Johann Walch, a German naturalist, studied trilobites thoroughly and suggested the name "trilobite," based on their three-lobed shape and two side lobes.
Written descriptions of trilobites may date back to the third century BC, but definite records begin in the fourth century AD. Spanish geologists Eladio Liñán and Rodolfo Gozalo suggest that some fossils called "scorpion stone," "beetle stone," and "ant stone" in ancient Greek and Latin texts refer to trilobites. Chinese sources provide clearer references, as fossils from the Kushan formation in northeastern China were used as inkstones and decorations.
In the 1860s, American fossil hunters found many Elrathia kingi fossils in western Utah. Until the early 1900s, the Ute Native Americans of Utah wore these trilobites, which they called pachavee (little water bug), as amulets. A hole was drilled in the fossil, and it was worn on a string. The Ute believed these necklaces protected against bullets and diseases like diphtheria. In 1931, Frank Beckwith found evidence of this practice. He photographed petroglyphs that likely show trilobites and examined a burial site with a drilled trilobite fossil in the chest of the buried person. Since then, trilobite amulets have been found in the Great Basin, British Columbia, and Australia.
In the 1880s, archaeologists found a drilled trilobite fossil in the Grotte du Trilobite (Caves of Arcy-sur-Cure, Yonne, France). The fossil was heavily handled, suggesting it was worn as a pendant. The layer of soil where it was found is about 15,000 years old. Because the trilobite was not native to the area, it may have been traded from elsewhere, showing its value to ancient people.