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The revelation of a digestive system in a 320-million-year-old animal sheds light on the early evolutionary history of starfish and related animals, according to a new study co-authored by a UT researcher.

Reconstruction of the fossil with the gut shown in blue. The fossil is less than 3 mm in height. Image credit: I. Rahman

Colin Sumrall, assistant professor in paleobiology, and colleagues from three other institutions analyzed the unique fossil specimen using high-energy x-rays at the Swiss Light Source in Switzerland. The microscopy examined the inner workings of the tiny fossil, which revealed evidence of the digestive system for the first time.

The fossil under study is a primitive relative of modern sea urchins and starfish and is part of a major group of marine invertebrates called echinoderms. Until now, a digestive system like the one discovered has never been seen in fossils belonging to this group.

“The results have highlighted a number of previously unknown differences between the fossil and its living relatives,” said Sumrall, who is based in UT’s Department of Earth and Planetary Sciences. “This has forced us to rethink our ideas about how the digestive system evolved in echinoderms.”

The findings were published today in the journal Biology Letters.

Sumrall worked with researchers from the University of Bristol, Appalachian State University, and the Paul Scherrer Institut.

The results of x-ray imaging prove that the fossil represents an early developmental stage of an extinct group known as blastoids, according to the researchers. It can therefore shed light on the early evolutionary history of echinoderms.

Lead author Imran Rahman, a paleontologist in the University of Bristol’s School of Earth Sciences, noted that the team used a particle accelerator called a synchrotron to image the fossil in 3-D. This allowed them to create a digital reconstruction of its internal anatomy.

Co-authors were Johnny Waters, professor in invertebrate paleontology at Appalachian State University, and Alberto Astolfo, of the Paul Scherrer Institut in Switzerland.

The work was supported by funds from the UK’s Royal Commission for the Exhibition of 1851 and the National Science Foundation in the United States.

View the 3-D reconstruction video.




Lola Alapo (865-974-3993,

Colin Sumrall (865-974-0400,