Using calcium isotopes to determine palaeodiet and palaeotrophic levels in the Elliot Formation

Diets of extinct animals are challenging to reconstruct. Past studies of ancient food webs infer palaeodiets using proxies such as dental morphology. These proxies can be limited due to factors like poor preservation. The Elliot Formation of the Karoo Supergroup (South Africa) has an abundant and diverse nature of fossils. What if there was a way to characterise rich Karoo sequences and get an insight into the diverse nature of the different ancient ecosystems to further understand population dynamics and dietary behaviour? Could we use isotopic tools to better understand palaeoecology of ancient ecosystems deeper in time?


Small bites

  • Calcium is a bio-essential element found in plants, animals and humans. It is a major component in tooth enamel and is influenced by the food and water consumed.
  • This study aims to gain an insight into the different trophic divisions and palaeodiets, such as carnivores and herbivores, of vertebrates found in the Elliot Formation, Karoo Supergroup (South Africa).
  • Isotopic tools, like non-traditional Ca isotopes, can assist in further understanding ancient ecosystems.

A palaeoecological study using calcium isotopes of ancient ecosystems

Diets of extinct animals are challenging to reconstruct. The best hypotheses for ancient food webs rely on the use of multiple proxies such as dental morphology. Factors like poor preservation of evidence, which would generally be linked to diet, limit the use of these proxies and leaves many fundamental palaeodiet and palaeotrophic level questions unanswered. Traditional stable isotopes such as carbon and oxygen have also been used in the past to assess palaeodiets and palaeotrophic levels in modern and ancient ecosystems. Unfortunately, these isotope systems have limitations as they can easily be rested or influenced by diagenesis as bone is quite porous and easily altered.

Geochemical markers on preserved tooth enamel may indicate varying diets such as herbivore or carnivore as well as the different niches these ancient animals may have filled. These markers can overcome the challenges of poor preservation. Calcium (Ca) is a bio-essential element and displays isotopic fractionation in plants and animals. It is a major component in tooth enamel and is not easily altered. The non-traditional Ca (δ44/42Ca) isotope system can be used to assess a broader range of questions, including dietary range and trophic level.

The Elliot Formation of the Karoo Supergroup (South Africa) preserves fossils from the latest Triassic to the earliest Jurassic interval (214 to 190 Ma) with an abundant and diverse range of vertebrates’ lineages and body sizes. This makes it an ideal natural laboratory for understanding palaeodietary dynamics. The main aim of my research is to assess the trophic divisions of the Elliot Formation vertebrates that co-existed in the same period using Ca δ44/42Ca isotopic analyses. Being able to test these important ecological principles in temporally constrained formations will allow us to understand the historical nature of biodiversity changes and the different laws that govern biological life forms on Earth. This study illustrates how isotopic proxies like δ44/42Ca can be used to better understand dietary dynamics, and ultimately palaeoecology, within past ecosystems.

Priyanka Davechand, a GENUS grantee, is an emerging scientist. She is currently completing her PhD at the School of Geosciences at the University of the Witwatersrand.

Priyanka Davechand pipetting MilliQ water onto a tooth prior to sampling (Photo Credit: Priyanka Davechand)

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