44 Paleontology, Paleoecology/Taphonomy, Phylogenic Morphological Patterns (Posters)

Tuesday, 24 March 2026
8:00 AM - 12:00 PM
CCC, Ballroom C

An Unusual Occurrence of Helminthopsis in the Silurian (Wenlock) of the Cincinnati Arch Region

Paper number: 44-9
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

The pascichnial burrow Helminthopsis is reported from the middle Silurian (Wenlock: Sheinwoodian) Massie Formation of southeastern Indiana, USA, where it occurs within the muddy infill of damaged nautiloid cephalopod phragmocones. Shells of the orthoceratid Dawsonoceras annulatum had settled, post mortem, on the soft, fine-grained sediment of the seafloor with the upward-facing lateral surfaces exposed to biostratinomic damage at the sediment-water inface. Removal of the unburied portion of the cephalopod shells exposed the cylindrical interiors, which was embedded in the sediment. These trench-like features on the seafloor became infilled with fine mud that may have been more organic-rich than surrounding sediment. The meandering burrows are constrained by the lateral shell walls on either side, reflecting systematic mining of the infilling mud. Such an association is rare and unusual, being hitherto unreported from the well-studied Massie Formation; pascichnial burrows are otherwise known only from the margins of microbioherms occurring lower in the formation. This study contributes to the poorly documented softground ichnofauna of a paleontologically important North American Silurian unit and, more broadly, demonstrates the role that cephalopod shells played in generating localized conditions in Paleozoic muddy softground settings.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411228

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