Pyritized Cryptolithus Trilobite Fossil Association

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. This is another location that was found which in addition to Triarthrus has Cryptolithus as well. These trilobites were buried rapidly, resulting in an anxonic environment which allowed for infilling with fine-grained pyritic deposits that preserved the details seen here. The degree of pyritization is less pronounced than that in the Triarthrus. This is a recently-discovered site that is only some 2 meters square, and has Cryptolithus far larger than others seen before. This fine example is preserved in dorsal aspect. These trilobites are prepared using a very fine 50 nanometer powder in order to preserve the pyrite. Note the fine pitting to the cephalic rim (fenestrae) which are thought by some to have been used in filter feeding of fine particulates from the sediment. There are several other cephalons and cranidia present, some belonging to other examples of C. bellulus while others are Triarthrus eatoni. There are also 2 types of crinoid stem as well, with the blockier stems attributed to Pentacrinites, and the round ones belonging to Glyptocrinus, making for a fine association piece.