Triarthrus Trilobite with Preserved Eggs

Description: With only about a half dozen localities known, trilobites with soft tissue preservation are rare. A well-known site in the United States is Beecher’s Trilobite bed where examples of Triarthrus, Cryptolithus, and Cornuproetus are known. In 2005 a new location in Lewis County was discovered which will take its place in this select group as a site containing Triarthrus eatoni with preserved appendages. These trilobites were buried rapidly, resulting in an anoxic environment which allowed for infilling with fine-grained pyretic deposits that preserved the details seen here. The rich gold color is a striking contrast to the deep black matrix, making for a dramatic specimen available in very limited quantities. This fine example is preserved in ventral aspect with limbs preserved. These trilobites are prepared using a very fine 50 nanometer powder in order to preserve the pyrite. At the Tucson Fossil Show this year the discoverer of this site and preparator of this exceptional specimen had something new to offer: trilobites with preserved eggs. This is the first known instance of preserved eggs of the species, and most likely represents an early stage in the development of the eggs which were formed in the head and subsequently released into the environment. See my other offerings tomorrow for another even more spectacular Triarthrus specimen.

Reference: Geology, 45(3), 2017, pp 199-202.