Fast Facts about Elrathia Trilobites
Name:
Elrathia kingii. The genus name Elrathia comes from Elrath, Alabama, where related trilobites were first described. The species name is properly spelled kingii, not kingi.
Taxonomy:
Phylum Arthropoda; Class Trilobita; Order Ptychopariida; Family Alokistocaridae; Genus Elrathia.
Species:
Commonly referenced species include Elrathia kingii and Elrathia marjumi.
Age:
Cambrian Period.
Distribution:
North America. Elrathia kingii is especially abundant in the Cambrian Wheeler Shale of Utah and Nevada.
Body Size:
Most specimens are about 1 inch long. Small individuals can be only a few millimeters, while larger examples may approach 2 inches, or about 50 mm.
Diet:
Likely a particle feeder and scavenger that moved along the Cambrian seafloor.
Appearance:
Elrathia has a broad thorax, short genal spines on the cephalon, and a generally plain, streamlined body shape.
Fun Fact:
Elrathia kingii lived in low-oxygen environments. These conditions helped preserve large numbers of fossils, which is one reason it is among the most commonly collected trilobites in North America.
Megalodon Unearthed:
Dr. Jay M. Lipoff , 2026
New Megalodon Book: Expert insight and vivid fossil photography strip away myths to reveal the true science of history's most fearsome shark.
Elrathia Trilobite Facts and Information
Elrathia kingii is one of the most familiar Cambrian trilobites because it occurs in huge numbers in parts of the Wheeler Shale of Utah. In some layers, these fossils are so abundant that commercial quarries have long collected and sold them as classic examples of trilobite fossils from the American West. For many people, Elrathia kingii is the first real trilobite fossil they ever see, buy, or collect.
This trilobite lived during the Middle Cambrian, when Utah was covered by a shallow inland sea. The Wheeler Shale preserves a rich marine ecosystem that included trilobites, agnostids, brachiopods, sponges, worms, and other soft-bodied organisms. Elrathia kingii was especially successful in this environment and is often found alongside other Cambrian trilobites such as Asaphiscus wheeleri and tiny agnostid trilobites like Peronopsis.
Elrathia kingii has a broad thorax, short genal spines, and a relatively simple body form. Most specimens are about an inch long, though tiny juveniles and larger adults are also found. The simple outline makes Elrathia easy to recognize, especially when preserved as a dark fossil against gray shale. Many specimens are found without the free cheeks attached, which is common in trilobites because those parts separated during molting or after death.
Its body shape and mouthparts suggest that Elrathia was probably a particle feeder or scavenger living on the Cambrian seafloor. It likely moved across the bottom, feeding on organic particles and small bits of decaying material in the sediment. These trilobites are often associated with low-oxygen, or exaerobic, seafloor conditions. Those environments were stressful for many animals, but they also favored fossil preservation by slowing decay and limiting scavenging.
This combination of abundance, easy identification, and excellent preservation is why Elrathia kingii has become one of the most collected trilobites in North America. It is not the most ornate trilobite, but it is one of the best examples of Cambrian marine life and an important fossil for understanding the ancient Wheeler Shale ecosystem of Utah.
Where to Find Elrathia Trilobite Fossils
Elrathia kingii trilobites are mainly found in the Cambrian Wheeler Shale of Utah and Nevada. The House Range near Delta, Utah, is especially famous for these fossils, and many collectors know Elrathia as the classic trilobite from U-Dig Fossils.
To find your own Elrathia kingii, the U-Dig Fossils quarry near Delta, Utah, is one of the most accessible collecting sites. Visitors split slabs of Wheeler Shale and look for dark trilobite fossils preserved on the bedding planes.
You can also read about my trilobite fossil collecting trip in the Wheeler Shale near Delta, Utah.
Recommended Trilobite and Fossil Hunting Books:
The Trilobite Collector's Guide
Andy Secher, 2024
This book by Andy Secher, a leading trilobite collector, offers a captivating journey into the world of these ancient arthropods. With over 400 stunning photos, entertaining top-ten lists, invaluable collecting tips, and ways to spot a fake trilobite, it's a must-have for fossil enthusiasts!
Trilobites: Common Trilobites of North America (A NatureGuide Book)
Jasper Burns, 2000
An excellent guide for identifying North American trilobites, featuring meticulous line drawings and concise information on classification, geologic range, and distribution. Ideal for enthusiasts seeking detailed insights and accurate identification of these ancient arthropods.
101 American Fossil Sites You've Gotta See
Albert B Dickas, 2018
This is a great updated fossil sites book with at least one fossil site in each state. Each site is broken into 2 pages. One has detailed information, such as directions, GPS coordinates, formation information, etc...
The other is dedicated to images of the site and the fossils found there. It also gives information on fossil 'viewing' sites such as dinosaur trackways, museums, and active excavations.
Plus, my fossil photos are peppered throughout this book!
