23-7 A New Sea Cucumber (Holothuroidea) Fauna from the Upper Mississippian Pella Formation of Iowa

Session: Paleontology of North America (Posters)

Presenting Author:

Authors:

Abstract:

The upper Mississippian (uppermost Chesterian/ latest Visean) Pella Formation, was deposited in a shallow, open marine environment with a muddy bottom, and is well know for fossil echinoderms including crinoids, blastoids, echinoids and edrioasteroids.  However, to date holothuroids and ophiuroids have yet to be documented, even though they are common in the microfossil fraction of the formation. These microfossils can help to fill gaps in the fossil record and to clarify the timing of diversification and evolution. Here we will specifically explore the record of sea cucumbers. Eight samples were collected from the Russell Wildlife Area in Mahaska County, Iowa. Microfossils were washed from poorly indurated marls and specimens were removed by hand from the resulting fossil residues. For this preliminary study, specimens of holothuroids were collected from one of these eight samples.  Approximately 50 calcareous ring elements were recovered from the coarser fraction (0.25-1 mm), and wheel and hook elements were recovered from the 0.063-0.125 mm fraction.

Sea cucumbers (Holothuroidea) are represented by at least 4 taxa, based on well preserved calcareous ring elements and corresponding body-wall ossicles. All of the calcareous ring elements appear to belong to the apodid holothurians (Paractinopoda). A new taxon comprises the majority of the material with hook-shaped body-wall ossicles (‘Achistrum’ sp.), as does a second, as of yet unnamed taxon that corresponds to specimens bearing wheel-shaped ossicles (‘Thalattocanthus’ consonus). With the small initial sample size, very few calcareous ring elements (unspecific interradialia) could be provisionally assigned to a group. In addition, ossicles of elasipodids (Actinopoda: ‘Microantyx’ botoni) occur in the material, but the corresponding calcareous ring elements for this group have not been identified.

This new investigation shows that, particularly when describing and interpreting fossil sea cucumber fauna, both diagnostic body-wall ossicles and the very specific calcareous ring elements should be used as much as possible.

Geological Society of America Abstracts with Programs. Vol. 58, No. 1, 2026

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