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Research suggests how Jurassic ichthyosaurs adapted to low oxygen levels

Research suggests how Jurassic ichthyosaurs adapted to low oxygen levels

Image: Artwork of Jurassic Ichthyosaur. Image credit: Curtin University.

The presence of well-preserved biological material found in an Early Jurassic ichthyosaur vertebra suggests that fossils preserved through carbonate concretion could play a major role in understanding the biology of extinct species, as well as evolution, according to Curtin University research.

An interdisciplinary research team led by organic geochemist John Curtin Distinguished Professor Kliti Grice, as part of an Australian Research Council (ARC) Discovery Outstanding Research Award Fellowship, analysed a 182.7 million year old vertebra from an ichthyosaur—a large, prehistoric lung-breathing marine reptile, resembling the modern-day dolphin.

Professor Grice explained that the sample, which was collected from a cement quarry in Germany, was fossilised in a way that preserved cholesterol, red blood cells and collagen fibres. “A carbonate concretion encapsulated the Early Jurassic period vertebra, forming a tight seal that helped protect its tissue and cellular remains from full decomposition,” Professor Grice said. Carbonate concretions are most commonly associated with organic matter-rich mudstones, such as black shales, and are formed under highly anoxic (low oxygen) conditions.

Professor Grice and Chloe Plet, a PhD researcher at Curtin University, assessed the trabecular and cortical bones of the vertebra, where they discovered the presence of fossilised soft tissue. During our analyses of the sample, we discovered red blood cell structures that were up to five times smaller than those reported in most modern organisms,” Professor Grice said.

This discovery led the researchers to propose the small size of these blood cell structures was related to the ichthyosaur’s evolutionary adaptation to environmental conditions. “Ichthyosaurs evolved during a time when atmospheric oxygen levels were continuously low over a period of 70 million years,” Ms Plet said. “We propose that small red blood cells were favourably produced by the species to provide efficient oxygen transport and diffusion. For example, modern-day mammals living at elevated altitudes with lower oxygen levels make small and abundant red blood cells.”

Media issued by Curtin University.

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