The Early Evolution of Shelled Invertebrates

Project overview

Project period: 2017 - 2026

Participating departments from the museum: Palaeobiology

The Lophotrochozoa is one of the largest and most diverse branches in the tree of life, including, but not limited to group such as bivalves (Phylum Mollusca), earth worms (Phylum Annelida), moss animals (Phylum Bryozoa) and lamp shells (Phylum Brachiopoda). Genetic studies have revealed that these groups are closely related but their exact relationship to each other is not well understood. Fortunately, many lophotrochozoans have shells that can be and are frequently preserved as fossils. By utilizing this excellent fossil record, we can begin to untangle the earliest evolution of this key animal group.

During the early Cambrian animal life evolved explosively in the seas and many animal groups appeared for the first time. Among these groups were the first molluscs and brachiopods, together with a range of problematic fossils from animals that lack modern representatives. These extinct groups are the key to understanding the earliest evolution of modern animals as they represent early diverging branches of the animal groups that we are familiar with today. By studying these extinct groups and how their relationship to modern animals, we can begin to understand how the basic body plan of modern animal lineages evolved.

Project description

In this project, we focus on several different fossil groups, including the tommotiids who had an external skeleton composed of many small cone-shaped sclerites and the hyoliths who had a single tooth-like shell. We will investigate how the skeleton and internal anatomical structures in these groups evolved during the early Cambrian and how their characteristics changed over time. The internal structure of the shell as well as the environment where the animal lived is also significant. While we can show that some tommotiids are closely related to the Brachiopoda, the phylogenetic position of hyoliths and many other early Cambrian fossils is less clear, and whether they seem to be related to the Mollusca.

Funding

Vetenskapsrådet (2017-2021, 2021-2026)

Urval av publikationer

• Zhang, Z., Zhang, Z., Holmer, L.E., Topper, T.P., Pan, B. and Li, G., 2023. Diversity and evolutionary growth of biomineralized columns in early Cambrian phosphatic-shelled brachiopods. bioRxiv, pp.2023-06. https://doi.org/10.1101/2023.06.01.543202
• Liang, Y., Strotz, L.C., Topper, T.P., Holmer, L.E., Budd, G.E., Chen, Y., Fang, R., Hu, Y. and Zhang, Z., 2023. Evolutionary contingency in lingulid brachiopods across mass extinctions. Current Biology. https://doi.org/10.1016/j.cub.2023.02.038
• Li, L., Topper, T.P., Betts, M.J., Dorjnamjaa, D., Altanshagai, G., Enkhbaatar, B., Li, G. and Skovsted, C.B., 2023. Calcitic shells in the aragonite sea of the earliest Cambrian. Geology, 51(1), pp.8-12. https://doi.org/10.1130/G50533.1 External link.
• Li, L., Betts, M.J., Yun, H., Pan, B., Topper, T.P., Li, G., Zhang, X. and Skovsted, C.B., 2023. Fibrous or Prismatic? A Comparison of the Lamello-Fibrillar Nacre in Early Cambrian and Modern Lophotrochozoans. Biology, 12(1), p.113. https://doi.org/10.3390/biology12010113 External link.
• Li, L., Skovsted, C.B. and Topper, T.P., 2022. Deep origin of the crossed‐lamellar microstructure in early Cambrian molluscs. Palaeontology, 65(4), p.e12620. https://doi.org/10.1111/pala.12620
• Zhang, Z., Topper, T.P., Chen, Y., Strotz, L.C., Chen, F., Holmer, L.E., Brock, G.A. and Zhang, Z., 2021. Go large or go conical: allometric trajectory of an early Cambrian acrotretide brachiopod. Palaeontology 64, 727-741. https://doi.org/10.1111/pala.12568
• Liu, F., Skovsted, C.B., Topper, T.P. and Zhang, Z., 2022. Hyolithid-like hyoliths without helens from the early Cambrian of South China, and their implications for the evolution of hyoliths. BMC Ecology and Evolution, 22(1), pp.1-15. https://doi.org/10.1186/s12862-022-02022-9
• Pan, B., Skovsted, C.B., Brock, G.A., Topper, T.P., Holmer, L.E., Li, L.Y. and Li, G.X., 2020. Early Cambrian organophosphatic brachiopods from the Xinji Formation, at Shuiyu section, Shanxi Province, North China. Palaeoworld 29, 512-533. https://doi.org/10.1016/j.palwor.2019.07.001
• Li, L., Skovsted, C.B., Yun, H., Betts, M.J. & Zhang, X. 2020. New insight into the soft anatomy and shell microstructures of early Cambrian orthothecids (Hyolitha). Proceedings of the Royal Society B 287: 20201467 External link.
• Liu, F., Skovsted, C.B., Topper, T.P., & Zhang, Z.-F. 2020. Soft part preservation in hyolithids from the lower Cambrian (Stage 4) Guanshan Biota of South China and its implications. Palaeogeography, Palaeoclimatology, Palaeoecology. https://doi.org/10.1016/j.palaeo.2020.110079 External link.
• Liu, F., Skovsted, C.B., Topper, T.P., Zhang, Z. & Shu, D., 2019. Are hyoliths Palaeozoic lophophorates? National Science Review, 7, 453-469. https://doi.org/10.1093/nsr/nwz161 External link.
• Topper, T.P., Guo, J., Clausen, S., Skovsted, C.B. and Zhang, Z., 2019. A stem group echinoderm from the basal Cambrian of China and the origins of Ambulacraria. Nature communications, 10, 1366. https://doi.org/10.1038/s41467-019-09059-3