23-2 Fossil Roommates: Possible Symbiosis of Bryozoans and Cornulitids from the Cincinnati Region of Ohio, USA

Session: Paleontology of North America (Posters)

Presenting Author:

Authors:

Abstract:

Ordovician so-called “gumdrop” trepostome bryozoans were collected from Trammel Fossil Park in Sharonville, Ohio. Specimens were collected as float from the same stratigraphic level, just below the Fairview Formation. Several of the bryozoans have circular tube-like structures that are filled with sediment. These circular structures are slightly elevated from the bryozoan growth surface. On a specimen that is broken, the circular structures are not elevated and show zooid growth around them. These tubes have been identified as Cornulitidae, an extinct encrusting tentaculitoid tubeworm (Middle Ordovician to Middle Jurassic). The intergrowth and lack of malformation in the bryozoan zooids indicates that the relationship with the tube-like structures is likely symbiotic. 

One specimen of bryozoan had what presented as “spikes” covering its growth surface. Under the microscope, those “spikes” could be identified as juvenile cornulitids encrusting the surface instead of growing within the bryozoan. Specimens were therefore separated into three main groups based on the cornulitids: absent, present, and present but juvenile. 

Individual bryozoan colonies in each group can appear vastly different on the outer growth surface and in overall shape of the colony. However, it is possible that the bryozoan has the same internal growth pattern. Acetate peels and thin sections were made to further examine the possibility of a symbiotic relationship between the bryozoans and cornulitids. The specimens that contain the cornulitids have been whitened and photographed. Preliminary analysis shows that ~70% of the “gumdrop” trepostome bryozoans contain cornulitids. Measurements of the individual colonies and the cornulitid apertures have been recorded as well as the number of cornulitids present on each colony. This study will illuminate the enigmatic cornulitids and their relationship with trepostome “gumdrop” bryozoans.   

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

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