Replica of Trilobite Triarthrus eatoni
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Drawings of the top (left) and bottom (right) of Beecher's molds.
Beecher based his reconstruction on this fossil of Triarthrus eatoni (YPM 201) he collected in July 1893.

Systematics: Arthropoda, Trilobita, Ptychopariida, Olenacea, Olenidae, Triarthrus eatoni

Size: About 1.5 inches long (3.5 cm)

Catalog no.: YPM 38277 (dorsal sculpture), YPM 38278 (ventral sculpture)

Age: Upper Ordovician

Locality: “Beecher’s Trilobite Bed,” near Rome, New York, USA

Sculptor: Charles E. Beecher

Trilobites, an extinct group of arthropods related to horseshoe crabs, lobsters, spiders and insects, crawled across the muddy booms of Paleozoic seas for 350 million years. About 570 million years ago, at the beginning of the Paleozoic Era during a period in the evolution of life known as the Cambrian Explosion, trilobites were one of the first groups of animals to appear in the fossil record. At the close of the Paleozoic, 250 million years ago, the last of the trilobites died out and the stage was set for the Mesozoic Era and the reign of other animals and plants.

In their heyday trilobites were one of the dominant marine life forms. Scientists have identified several thousand different species. These bottom dwellers ranged in size from less than an inch to 2 feet in length. Trilobites get their name from the three-lobed sections that run lengthwise down their bodies. As invertebrates, trilobites do not have an internal skeleton. Instead a mineralized external skeleton, or exoskeleton, protected them from predators.

In September 1893 Charles E. Beecher of Yale University’s Peabody Museum of Natural History purchased a $25, 10-year lease to collect fossils at an obscure site near Rome, New York. This site was a fossil hunter’s dream, a large concentration of well-preserved trilobites and other animals in a thin layer of Upper Ordovician rocks. This rare occurrence of well-preserved fossils, called a “lagerstätten,” or fossil bonanza, would later become known as “Beecher’s Trilobite Bed.”

William Valiant of Rome, New York, discovered these beds in 1892 after eight years of prospecting. Valiant’s find of a perfectly preserved specimen of Triarthrus eatoni, complete with antennae, stirred little interest among leading fossil collectors until Yale’s Professor Othniel C. Marsh passed several specimens on to his junior colleague, Charles Beecher. An experienced collector and preparator, Beecher immediately leased the site and published a description of these fossils by the end of 1893. He worked the site until 1896 when he declared it “worked out.”

Beecher, a superb preparator, made a careful reconstruction of Triarthrus eatoni with details never before known about the anatomy of trilobites. His 1897 brass molds of his reconstruction are 2.5 times actual size and show the fine detail of the dorsal (top) and ventral (bottom) sides of Triarthrus eatoni. While not 100% accurate, Beecher’s reconstruction set the standard for many years. The casts available from The Museum Store are derived from Beecher’s original 19th century molds. All the detail of the originals has been preserved. The original brass molds are in the Division of Invertebrate Paleontology of the Yale Peabody Museum of Natural History.

Scientific advisor: Tim White, Assistant Director for Collections and Operations, Peabody Museum of Natural History, Yale University