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Extinct Animals News
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Bone cancer found in Triassic turtle ancestor's fossilised femur
ABC Science By science reporter Belinda Smith Posted yesterday at 13:40  *This image is copyright of its original author Artist's impression of turtle ancestor Pappochelys rosinae, living at the edge of a lake 240 million years ago. (Supplied: Brian Engh) A 240-million-year-old ancestor of today's turtles also has the unfortunate honour of being one of the oldest known cancer cases ever found. Key points:
Researchers in Germany took detailed X-rays of one of the Triassic creature's leg bones and diagnosed it with a type of malignant bone cancer called osteosarcoma, which humans get today. The scans and diagnosis were reported in the Journal of the American Medical Association Oncology. The ancient growth is thought to be the oldest-known cancer so far found in the evolutionary branch that comprises birds, reptiles and mammals, said study author Yara Haridy, who is completing a PhD at Berlin's Natural History Museum. "Ancient cancer tells us that cancer is not a modern disease, but in fact it is a vulnerability within our DNA, and goes back at least to the Triassic," she said. "Cancer overall [in the fossil record] is very rare, making this an exceptional find." How to diagnose an extinct animal The cancerous bone belonged to Pappochelys rosinae, a four-legged animal that looked a bit like a turtle, but without a shell. Only one Pappochelys fossil has been found so far, discovered in a quarry in southwest Germany. It was unveiled in 2015 and filled a gap in the modern turtle's evolutionary timeline.  *This image is copyright of its original author The Pappochelys rosinae fossil, found in a Germany quarry, is 240 million years old. (Wikimedia Commons: Rainer Schoch) But one of its discoverers, German palaeontologist Rainer Schoch, noticed a rough patch on the fossil's left femur — the long bone running from hip to knee. "He found this interesting and brought it to our attention for further diagnostics," Ms Haridy said.
The Pappochelys femur is only around 4 centimetres long, but the uneven growth covered nearly the entire top half of one side of the bone. Using micro-CT to take X-ray slices through the bone, Ms Haridy and her colleagues were able to "see" fine details inside. This allowed them to analyse the growth's size, shape and appearance, all of which pointed to a malignant tumour, or osteosarcoma. Teghan Lucas, a forensic anthropologist at the University of New South Wales who was not involved in the new research, agreed with the diagnosis. "It has what we call a 'sunburst' appearance, where the bone looks rigid and spiky," Dr Lucas said. "That's very typical of osteosarcoma."  *This image is copyright of its original author An ancient bone, found with what appears to be a cancerous growth, was a femur of a turtle ancestor called Pappochelys rosinae. (Supplied: Brian Engh) In humans, osteosarcomas are the most common cancer that starts in bone cells. Some arise when genes that keep dividing cells in check, called tumour suppressor genes, malfunction. Unhampered by tumour suppressor genes, cells can divide out of control and lead to cancer. Unfortunately, we won't know if the genes that went awry in the ancient turtle were the same as those found in human bone cancers because we don't have any ancient DNA, nor could the German team tell if the osteosarcoma proved fatal. Diseases in the fossil record Finding cancer in the fossil record is rare, but Pappochelys isn't alone. For instance, it joins a 245-million-year-old amphibian, which had signs of a type of cancer called a neoplasm on its skull. When it comes to human fossils, the oldest is a 1.7-million-year-old human ancestor, which was discovered in South Africa with osteosarcoma. People who study ancient diseases — palaeopathologists — also examine remains of modern humans to gauge how disease rates changed over time. The overall incidence of cancer in remains from a few hundred years ago might be lower than cancer rates today, Dr Lucas said, but that's because people died younger back then. And while finding signs of cancer in skeletal remains might be few and far between, loads of other conditions leave tell-tale signs in bones. "You've got tuberculosis, leprosy, dwarfism, gigantism, syphilis — lots of diseases show up on bones," Dr Lucas said. I've attached the paper here. The full sized artistic renditions are on the website linked in the title. |
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