189-16 PROTISTAN BROMOLITES, COPROLITES, AND COLOLITES: CELLULAR ASPECTS AND POTENTIAL MICROPALEONTOLOGICAL SIGNIFICANCE

Session: Paleontology, Paleoecology/Taphonomy (Posters)

Presenting Author:

Authors:

Abstract:

Rhizarian protists, including all members of the genus Gromia as well as a wide range of Foraminifera, contain micrometer-scale, oblate aggregates of undigested waste (primarily clay particles and refractory organics) called stercomata. These structures can be found in vacuoles at the terminal stages of digestion (residual bodies), which are then defecated (via exocytosis) from the cell. In some cases, stercomata accumulate within shells (tests) of gromiids and foraminiferans, apparently as a means of increasing cell size without the need to synthesize additional energy- and oxygen or (nitrate)-dependent cytoplasm; this process also reduces the nutritional value of the protists to predators. We previously reported that stercomata resist disaggregation by bacterial decay and experimental chemical treatments, indicating their potential to fossilize. Indeed, stercomata-like structures have been found filling the tests of Ordovician Bathysiphon, mirroring their extant counterparts. As such, they are the unicellular analogs of metazoan cololites. In certain modern foraminifera, excreted stercomata are used as structural components of agglutinated tests. When fossilized, these stercomata are the cellular equivalents of coprolites. Stercomata may, therefore, be useful in identifying putative rhizarian protists in sedimentary deposits, or as rhizarian ichnofossils in fine-grained, siliciclastic sedimentary rocks. We propose using the terms cytocoprolite and cytocololite as the protistan versions of their metazoan counterparts, and cytobromolite as the general term for these fossil protistan waste products.

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

doi: 10.1130/abs/2025AM-9989

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