14-1 Taphonomic Controls on the Vertebrate Fossil Record from a High-Latitude, Early Triassic Terrestrial Assemblage (Fremouw Formation, Antarctica)

Session: Interdisciplinary Paleontology: New approaches to solving complex paleontological problems (Part II)

Presenting Author:

Authors:

Abstract:

The Fremouw Formation hosts the oldest record of tetrapod vertebrate fossils from Antarctica and figures prominently in paleontologists’ understanding of vertebrate assemblages at high paleolatitudes during Early Triassic times. Comparative work between the Fremouw and coeval assemblages at lower latitudes could uncover spatial heterogeneity in the tempo of recovery from the End-Permian Mass Extinction (EPME) across southern Pangea. However, to better understand the contribution of the Antarctic fossil record during the recovery of terrestrial ecosystems after the EMPE, we must first characterize and quantify the geologic, taphonomic and sampling filters that affect our ability to reconstruct ancient biodiversity and environments. In this study, we use over 600 specimens housed at the University of Washington Burke Museum of Natural History & Culture and the American Museum of Natural History to assess taphonomic controls on the completeness and quality of anatomical information preserved in the Fremouw vertebrate assemblage. We use a novel, generalized metric to quantify each specimen’s skeletal completeness, regardless of taxonomy and specific morphology. We then compare skeletal completeness with: 1) matrix lithology, 2) depositional setting, 3) taxonomic affinity, and 4) specimen locality. We find that, on average, more complete fossils are found in finer-grained sediments representing mostly lower-energy fluvial depositional environments interpreted as primarily crevasse splays on floodplains. Additionally, although dicynodont therapsids and temnospondyl amphibians are the most numerous fossils in these collections, on average the most skeletally complete groups are archosauromorph reptiles, as well as therocephalian and cynodont therapsids. These results suggest specific depositional settings and body size play prominent roles in filtering skeletal information in the Fremouw fossil record, and could inform future basin-level comparisons across southern Pangaea.

Geological Society of America Abstracts with Programs. Vol. 58, No. 4, 2026

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