Triarthrus eatoni Tribolite with Legs and Eggs

Triarthrus eatoni generally a rare trilobite to come by, but this specimen has its legs and antennae preserved and naturally impregnated with iron pyrite--along with its eggs! 

Triarthrus is a Late Ordovician ptychopariida trilobite that can be found in several states including New York, Ohio, Indiana and Kentucky as well as in Scandinavia, China, and northern provinces in Canada. Triarthrus eatoni was a common trilobite found within deeper waters 440 million years ago. 

Triarthrus could grow up to 2-inches in length, making it an average-sized trilobite. Its cephalon (head section) is semicircular with a raised glabella (midsection) and a relatively small pygidium (tail-end). The antennas were most likely flexible and are double the length of the cephalon. Triarthrus eatoni started as an egg that was less than a millimeter long and within a few months it was several millimeters long, living off of the ocean floor filtering food particles for nourishment. 

There are only a handful of sites in the world that are known to have soft bodied preservation of trilobites, and fewer so with pyrite. The Whetstone Gulf Formation in Lewis County, New York and Beecher’s Trilobite Bed in Oneida County, New York are exceptional localities that have exquisitely preserved Ordovician-aged trilobites with soft tissue replaced by pyrite. Because the trilobites within these formations were quickly buried in a mudslide 450 million years ago, oxygen was eliminated from the environment, replacing the oftentimes unseen soft appendages with the glimmering fool’s gold.

This Triarthrus eatoni specimen measures 1 x .5 inches (including the legs and antennae). When looking closely enough, minuscule specks are seen on and around the trilobite, which are its eggs. It is extremely rare to come across a trilobite specimen with soft tissues like legs and antennae preserved, let alone preserved eggs. 




Triarthrus eatoni Trilobite with Legs and Eggs
Late Ordovician
Whetstone Gulf Formation
Lewis County, New York