Earth Science Club of Northern Illinois (ESCONI)

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Mazon Monday #277: Sphenophyllales from the Mazon Creek flora (Upper Moscovian: Illinois, USA)

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This is Mazon Monday post #277.  What’s your favorite Mazon Creek fossil?  Tell us at email:esconi.info@gmail.com.

Figure 1. Hexaphyllostrobus negauneeana holotype. FM PP54628. A, B, Part and counterpart of cone showing overall dimensions and morphology. C, Distal region of the cone showing two orthostichies of sporophylls in surface view, and one orthostichy in lateral view. D, Central region of the cone showing details of the undulatory distal margin of the sporophyll lamina (arrow). Figure modified from Herrera et al. 2023. Scale: A, B = 1 cm; C, D = 5 mm.

Here’s a new paper “Sphenophyllales from the Mazon Creek flora (Upper Moscovian: Illinois, USA)” by some of our friends at the Field Museum, Yale, and the Smithsonian. It was published in the Biological Journal of the Linnean Society in June 2025. The paper describes a new species of Sphenophyllales cone, Hexaphyllostrobus negauneeana.  Sphenophyllales are related to modern day horsetails and were part of the ground cover during the late Carboniferous.

Abstract: Sphenophyllales is an extinct clade related to horsetails whose members were important ground-cover and understory components of the vast tropical Carboniferous peat swamps of Euramerica. These plants exhibited extreme anisophylly and heterophylly, complicating the development of whole-plant concepts within the group. Here, we describe a new species of a small sphenophyll cone—Hexaphyllostrobus negauneeana sp. nov.—using computed tomography of three remarkably well-preserved cones from the Pennsylvanian Mazon Creek flora of Illinois, USA. We also briefly review the broader diversity of sphenophylls present in the Mazon Creek flora as a step towards developing new whole-plant concepts within Sphenophyllales.

Authors: Michael P. D’Antonio, Peter R. Crane, Carol L. Hotton, Jack Wittry, and Fabiany Herrera

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.

 

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