Earth Science Club of Northern Illinois (ESCONI)

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Fossil Friday #340: Hexaphyllostrobus negauneeana from Pit 3

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This is the “Fossil Friday” post #340. 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!

Marty Houdek brought some very nice fossils for his display at the Mazon Creek Fossil Day event. One of his best was a very rare Hexaphyllostrobus negauneeana from the area of Pit 3 in Braidwood. H. negauneeana was described in July of 2025 by some of our friends at the Field Museum (see Mazon Monday #277).

Figure 8. Paleoartistic reconstruction of Hexaphyllostrobus species from Mazon Creek showing the entire cone (left) and details of the sporophylls at one node (right). Red dashed lines indicate where the sporophyll was digitally removed to show attachment of the pedicel to the axis. Bottom right: differences between Hexaphyllostrobus kostorhysii (left) and H. negauneeana (right) include sporangiophore attachment, number of sporangia per sporangiophore, sporangia size, and morphology of the sporophyll distal lamina. Art by Sofia Herrera.

H. negauneeana was a cone of one of the horsetail plants that lived during the Carboniferous Period. Horsetails belong to Sphenophyllales, a group of plants that provided important ground-cover and understory in the vast tropical Carboniferous peat swamps of Euramerica.

Here’s Marty with Ralph Jewell and I at Braceville in the Spring of 2026. Marty is one of the fossil contributors that generously provides fossils for our “Fossil Pour” at Braceville.

This is a breathtaking fossil, Marty! Thanks for sharing!

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