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A recently discovered species of fossil dating back 444 million years has been endearingly dubbed ‘Sue’ in honor of its discoverer’s mother.
This groundbreaking research, a culmination of 25 years of work by a palaeontologist at the University of Leicester, is documented in the journal Palaeontology. The new multisegmented fossil species has been officially named Keurbos susanae.
Professor Sarah Gabbott, the lead researcher from the School of Geography, Geology and the Environment, described ‘Sue’ as an extraordinary specimen: “She is an inside-out, legless, headless marvel. The fossil showcases an astonishingly detailed mineralized record of her insides, including muscles, tendons, and even digestive organs. Unfortunately, her exterior features, such as the carapace and limbs, have decayed over the millennia.”
According to Professor Gabbott, it is confirmed that ‘Sue’ was a primitive marine arthropod, although her exact evolutionary connections remain somewhat ambiguous.
Arthropods comprise approximately 85% of Earth’s current animal population, encompassing species like shrimp, lobsters, spiders, and centipedes. Although the fossil record for arthropods extends over 500 million years, most fossils reveal their external traits. In contrast, ‘Sue’ is remarkable for its internal preservation.
The fossil was unearthed from the Soom Shale, a formation of silicates and clay located 250 miles north of Cape Town, South Africa. These sediments were deposited on the ocean floor during a period characterized by a significant glaciation event that led to the extinction of nearly 85% of Earth’s species, marking one of the five great mass extinctions. Interestingly, it appears that the marine environment where ‘Sue’ thrived somehow sheltered its inhabitants from the harsh cold, allowing a vibrant community of species to survive.
The sedimentary conditions that preserved ‘Sue’ were notably extreme, lacking oxygen and infused with toxic hydrogen sulfide, which helped preserve the fossil in an unusual manner. Researchers propose that a unique set of chemical processes contributed to this exceptional preservation style.
However, this unique state of preservation presents challenges for scientific comparison with other fossils from the same era, resulting in a difficulty understanding ‘Sue’s’ position on the evolutionary tree.
The small quarry where Professor Gabbott discovered the initial fossils has largely vanished, diminishing the chance of finding additional specimens. The complexity of interpreting this fossil has been significant, and despite her hopes of discovering another with more intact features, the passage of time raises concerns about their rarity.
Professor Gabbott remarked, “This research journey has been akin to an ultramarathon. The remarkable preservation of this fossil presents layers of intricate anatomy that require detailed analysis. Initially, I had hoped to locate new specimens, but after 25 years, it seems ‘Sue’ is exceptionally rare. Especially since my mother jokingly urged me to name the fossil after her before she, too, becomes fossilized.”
“In jest, I tell my mom that I chose the name because she is a well-preserved specimen! However, the real reason is her unwavering encouragement for me to pursue a career that brings me joy—regardless of the path. For me, that path is rooted in studying rocks, discovering fossils, and uncovering the stories they tell about the ancient world and the evolution of life on Earth.”
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