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Grey, M., Finkel, Z.V., Pufahl, P.K. & Reid, L.M. 2012: Evolutionary mode of the ostracod, Velatomorpha altilis, at the Joggins Fossil Cliffs UNESCO World Heritage Site. Lethaia, Vol. 45, pp. 615-623. The estuarine ostracod Velatomorpha altilis was analysed for size and shape changes over a 2-3 million-year interval within a portion of the Joggins Fossil Cliffs World Heritage Site. This represents one of a very few number of studies focused on evolutionary trends within marginal environments and contributes to a growing body of research that attempts to link evolutionary patterns with processes. We measured nearly 400 ostracod specimens and used a quantitative model-based test to assess mode of evolution. Samples of ostracods were also analysed for their stable oxygen and carbon isotopic compositions in an attempt to supplement paleoenvironmental interpretations. Stasis was the strongly supported model for mode of evolution in both size and shape metrics, lending support to previous hypotheses that organisms from fluctuating, and therefore stressed, environments, should exhibit stasis because they are genetically well adapted to environmental change over geological time-scales. Stable isotopic compositions indicate samples were diagenetically altered and thus do not preserve a primary signature of paleoenvironmental conditions. Future work should look to other marginal organisms to test whether stasis is indeed a trend in these types of environments. □ Carboniferous, estuarine ostracod, environment, evolutionary mode. [ABSTRACT FROM AUTHOR]

The Joggins Fossil Cliffs UNESCO World Heritage Site contains a wealth of terrestrial and aquatic fossils from the late Carboniferous (Pennsylvanian) Period. Fossils from the aquatic realm have historically been under-studied at Joggins, and the brackish ecosystem they represent is poorly understood globally. We used coprolites, which are abundant in the limestones of the Joggins Formation, to broaden our knowledge of the aquatic ecosystem and help reconstruct the food web. Coprolites were studied in hand sample and with standard transmitted-light microscopy to determine morphology and contents. Cathodoluminescence was used to examine coprolite microfabrics to interpret the degree of post-depositional alteration. Specimens range in size from 1 to 10 cm in length and were divided into six broad groups based on size and shape (in order of most to least abundant): small/equant; cylindrical; heteropolar macrospiral; large; irregular; and amphipolar spiral. Where possible, specimens were identified to ichnospecies. The host rock (limestone) and large quantities indicate that at least most, perhaps all, coprolites originated from fish, with some potentially originating from amphibious tetrapods. Bone fragments and/or coated grains were found in the majority of samples, however their relative abundance differs between morphotypes: small/equant coprolites contained the most coated grains and fewest bones and heteropolar macrospiral coprolites contained the most bones and almost no coated grains. Specific species identification of bones was not possible. The mineralogy of the coprolites is phosphatic, specifically carbonate fluorapatite, suggesting that the fish producing these coprolites were carnivorous and that there was a lack of coprolites generated by herbivores. Based on our findings of coprolite morphology and contents and what is currently known about the biotic environment, we introduce a hypothetical trophic pyramid, with rhizodonts at the apex producing the largest coprolites, and smaller fish species responsible for the small/equant-shaped coprolites at the secondary consumer level. This research provides a foundation for further studies on coprolites and other bromalites for a deeper understanding of brackish ecosystems where fish diversified further into fresh water during the Palaeozoic. • Coprolites from the Joggins Formation provide information on species interactions in a globally understudied environment. • Petrographic analyses were the most useful methods for investigating coprolites. • Evidence indicates that fish were the tracemakers and many ichnospecies were identified. • Coprolite morphology and content, and body fossils, indicate three trophic levels are represented in the aquatic food web. [ABSTRACT FROM AUTHOR]