189-17 Spiral Coprolites from the Smokey Hill Chalk Member of the Niobrara Formation

Session: Paleontology, Paleoecology/Taphonomy (Posters)

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Abstract:

Spiral and scroll coprolites are among some of the more conspicuous forms of fossil feces morphologies, characterized by ribbon-like coils and mostly recognized in Paleozoic deposits. Within the Niobrara Formation (Late Coniacian to Early Santonian), among the abundant vertebrae and macroinvertebrate remains, is a plethora of coprolite trace fossils of variable morphology including a distinct group of spiral forms. The goals of this research project were twofold: 1) document and compare coiled forms from this assemblage, and 2) determine the 3D ultrastructure of these specimens to garner information about the organisms that produced them. Coprolites were imaged using high-definition macrophotography to collect general dimensions (length, width, height, etc.) and more specific measurements of the spiral coils themselves. Samples were CT-scanned at the Microanalysis Lab at the University of Missouri-Columbia, and CT slices were imported into Dragonfly Comet 3D analysis software, where they were segmented and visualized.

Seven spiral specimens were investigated representing three morphotypes, including heteropolar (n=5), amphipolar (n=1), and scroll forms (n=1). Specimens varied from 49.8–93.8 mm in length, 36.4–53.1 mm in height, and 17.8–33.7 mm in width, with the average being 72.2 mm, 40.6 mm, and 29.2 mm respectively. The heteropolar specimens exhibited between 3-5 coils, with diameters ranging from 1.8–33.7 mm (average=13.3 mm). The amphipolar specimen exhibited 5 coils, ranging from 3.0–22.7 mm in diameter (average=10.4 mm). The scroll specimen exhibited 3 obvious external coils ranging from 2.7–15.0 mm in diameter (average=10.4 mm). Examination of coprolite exterior surfaces revealed minimal obvious skeletal inclusions, a finding corroborated by preliminary CT-data revealing predominantly a chalky to phosphatic matrix. Internally, the arrangement of the coils differs markedly between forms, with each displaying more complex ribbon-like arrangements with overlapping coils than what can be determined from the exterior surfaces alone. Despite the limited sample size, variation in gross morphology and coil structure suggest that these coprolites were attributed to multiple producers. Ongoing analysis with additional samples and further 3D segmentation of internal coil arrangements may enable attribution of specific morphotypes to Chondrichthyan taxa documented within the fossil assemblage.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10348

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