SMALL BUT BITEY: MINIATURE SCOLECODONTS OBSERVED DURING THE LATE DEVONIAN LOWER KELLWASSER EXTINCTION EVENT

Scolecodonts are fossilized components of polychaete annelid jaw apparatuses, and are commonly found preserved organically in siliciclastics beginning in the Lower Paleozoic. We observe outstandingly small scolecodonts in black shale samples collected in the Appalachian Basin during and near the Kellwasser Events of the Late Devonian Biodiversity Crisis, ca. 365 Ma, as compared to fossils measured from older strata. Smaller body size could be selective due to nutrient insufficiency, oxygen stress, or niche partitioning.

The Middle and Late Devonian were intervals of protracted environmental stress, including intermittent anoxia and frequent dysoxia. Although smaller body sizes are commonly observed after the Permian-Triassic Mass Extinction (the Lilliput Effect), this has not been previously described in the Devonian. By studying this miniature fauna, we will gain a better understanding of the biotic crisis in the Late Devonian, and may also be able to identify the mechanism(s) by which smaller body size was selected for. Characterizing evolutionary responses to climate change in deep time is critical to informing conservation efforts in response to modern climate change.