This is the “Fossil Friday” post #331. Expect this to be a regular feature of the website. We will post fossil pictures you send in to esconi.info@gmail.com. Please include a short description or story. Check the #FossilFriday Bluesky/Twitter hash tag for contributions from around the world!

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Jerry Zhu posted this stunning example of Peachocaris strongi to the “Illinois, Mazon Creek, and Carboniferous Fossils of the World” group on Facebook a few weeks ago. Jerry collected the concretion from Pit 11 and it opened recently via freeze/thaw.

Nice photos and thanks for sharing, Jerry!

P. strongi was initially described in 1962 by Harold Kelly Brooks, who is the namesake for Kellibrooksia macrogaster). He originally placed it in the genus  Anthracophausia. In 1974, Frederick Schram renamed the genus to Peachocaris.

Peachocaris is named for British paleontologist Ben Peach, who made significant contributions to the early study of  Carboniferous Malacostraca. While the species name comes from Samuel S. Strong, an early Mazon River collector. Strong collected the holotype YPM 18821, which resides in the Yale Peabody Museum.

The following description is from Jack Wittry’s book “The Mazon Creek Fossil Fauna”… For more about Peachocaris strongi, see Mazon Monday #82.

Peachocaris strongi is of moderate size. The carapace is one third the length of the animal, somewhat rectangular in outline, and has a short, sharp rostrum. A prominent optic notch protects the large eyes, which are often easily seen elevated on a stalk above the carapace. The rounded segments of the pleon decrease in size posteriorly. The prominent tail fan contains a tapered telson and uropods. All eight pairs of thoracic appendages are modified for swimming and appear blurred due to a coating of fine hairs. The pleopods are flap-like paddles. P. strongi has the body structure of a filter-feeder and often shows its last feeding in a well-preserved gut-line. This animal is usually found ghost-like and lying on its side.