189-23 Invertebrate Fauna of the Oligocene Sooke Formation Sheds Light on the Paleoenvironment of Behemotops proteus (Mammalia, Desmostylia)

Session: Paleontology, Paleoecology/Taphonomy (Posters)

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Abstract:

Desmostylians are enigmatic marine mammals known from the Oligo-Miocene of the Northern Pacific Ocean. Among the many things that remain unknown about desmostylians are their locomotion and habitat, with reconstructions ranging from bear-like coastal paddlers to sea lion-like open water swimmers. One species, Behemotops proteus, is known from a partially complete skeleton found at Sombrio River Mouth on Vancouver Island. The specimen was preserved within a layer of siltstone from the Oligocene Sooke Formation. The lithology of the layer it was found in suggests that it lived in either deeper water offshore or a closed lagoon. Our goal was to determine what marine zone this species of desmostylian lived in based on the invertebrate fauna at Sombrio River Mouth. In July of 2025, we collected fossil invertebrates from the same locality and siltstone layer that the B. proteus specimen originally came from. We collected nine marine invertebrate specimens and took photos of fossils we were unable to excavate. Preliminary identification of these specimens suggests the presence of the bivalves Acila, Macoma, and Ensis, the gastropods Polinices and Levifusus, and the scaphopod Dentalium. These genera are more commonly found at depths of 30 to 200 meters suggesting that this site was a deeper water environment as opposed to a shallow lagoon. Taphonomic evidence suggests that there was minimal transport of the B. proteus specimen between death and burial. The bones showed no abrasion, scattering, evidence of scavenging, or invertebrate attachment. This suggests that B. proteus lived in a deeper water environment and was a more fully marine mammal. We will continue testing this hypothesis by completing identification of invertebrates from the site and through morphometric analysis of B. proteus and other desmostylians.  

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

doi: 10.1130/abs/2025AM-7955

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