A newly recognized fossil found out within the historic shale of South Africa, has surprised paleontologists with its uncommon preservation of inner comfortable tissues. The analysis, printed in Papers in Palaeontology on March 26, 2025, main points an bizarre 25-year learn about.
Sue, An Extraordinary Window Into Historical Arthropods
The fossil, affectionately nicknamed “Sue”, items a organic paradox: the exterior options — such because the carapace, legs, and head — in most cases preserved within the fossil report, are solely lacking.
As a substitute, the fossil gives an “inside-out” view of an early arthropod’s muscle mass, tendons, connective tissues, or even intestine buildings, astonishingly well-preserved in sediment just about part a thousand million years outdated.
This kind of preservation is nearly extraordinary. In trendy paleontology, comfortable tissue fossilization is outstandingly uncommon because of the fragility of natural subject. But on this case, the inner buildings continued whilst the in most cases extra resilient exoskeleton decayed — a reversal of herbal fossilization tendencies.
The Poisonous Grave That Preserved a Surprise
The fossil used to be unearthed within the Soom Shale, a sedimentary formation positioned kind of 250 miles north of Cape The city, South Africa. This marine basin shaped simply after a catastrophic glaciation match all over the Ordovician length, which ended in one of the vital 5 primary mass extinctions, wiping out 85% of Earth’s species.
This actual basin turns out to have served as a shelter for a novel neighborhood of marine organisms. Its extremely poisonous, anoxic (oxygen-deprived) and hydrogen sulfide-rich waters most probably enabled the fossil’s distinctive preservation. Scientists speculate that the chemistry of this atmosphere acted like a preservative vault, mineralizing inner tissues earlier than they may decay.
Such prerequisites will have induced a type of chemical fossilization hardly ever observed on Earth, a procedure nonetheless now not absolutely understood. Researchers describe it as a “abnormal chemical alchemy” — person who preserved Sue’s innards in beautiful element.
A Fossil With No Recognized Equivalent
Regardless of its detailed preservation, Keurbos susanae doesn’t well have compatibility into any recognized lineage. It’s obviously an early marine arthropod, however its exact evolutionary relationships stay a thriller.
Professor Gabbott refers to Sue as a “headless, legless surprise,” now not handiest as a result of the ones frame portions are lacking, but in addition for the reason that fossil refuses to be simply labeled. In a fossil report wealthy with arthropods, this specimen flips expectancies by way of retaining the least anticipated portions of the frame.
A Legacy Fossil and a Non-public Tribute
Professor Sarah Gabbott started learning this fossil 25 years in the past, firstly of her educational occupation. The verdict to call the fossil after her mom, Sue, provides a private size to the invention.
“I inform my mother in jest that I named the fossil Sue after her as a result of she is a well-preserved specimen,” Gabbott mentioned, “however in fact, I named her Sue as a result of my mother at all times mentioned I will have to practice a occupation that makes me satisfied — no matter that can be.”
The naming of Keurbos susanae is greater than a nod to maternal inspiration — it’s the end result of a long time of labor, patience, and keenness for historic existence.
The fossil Keurbos susanae, or Sue, within the rock. Credit score: College of Leicester
The Larger Image for Evolutionary Biology
Arthropods make up round 85% of all animal species, together with bugs, spiders, lobsters, and crabs. Their fossil historical past stretches again over 500 million years, however examples like Sue be offering one thing radically other — a peek underneath the exoskeleton into how those creatures functioned internally.
This sort of preservation provides scientists an extraordinary probability to review the myoanatomy (muscle association) and endoskeletal buildings of early marine arthropods. It is going to sooner or later assist researchers untangle portions of the arthropod evolutionary tree that stay difficult to understand, filling in gaps that extra typical fossils can’t deal with.