Unique Marine Fossil Discovered in South Africa: Exceptional Preservation Reveals Rare Insights [Analysis]

A fossilized organism discovered at a South African roadcut quarry two decades ago has finally been granted an official designation. This tiny, jointed, shrimp-like animal, estimated to be around 444 million years old, is now formally recognized as Keurbos susanae. As part of the arthropod family, which encompasses approximately 84% of all currently documented species—including insects, spiders, and crabs—it holds significant importance within this extensive class of creatures.

Paleontologist Sarah Gabbott discusses what makes her work distinctive. discovery , which she designated during the scientific description process.

Can you provide information about this organism and the habitat where it thrived?

The fossil measures approximately 50 cm in length and consists of 46 nearly identical segments. Extending from each segment is a fragile, gill-like feature. It likely appeared somewhat similar to a horseshoe crab and the gills would have been for absorbing oxygen from the water it lived in. Its insides are exquisitely well-preserved, which is very unusual for fossils - normally only the hard, more decay-resistant external features would be preserved. You can see bundles of muscle fibres that would have powered the limbs, tendons and an internal scaffold structure that gave the animal rigidity.

It likely spent the majority of its time residing on, or perhaps slightly above, the ocean floor, possibly moving through an undulating (wave-like) gait.

It existed right after the end Ordovician extinction event Over 440 million years ago, an event triggered by widespread glaciation (expansion of frozen conditions) affected large parts of the globe. This mass extinction eliminated approximately 85% of Earth's species. The marine environment where Keurbos susanae lived was likely extremely frigid and occasionally blanketed with sea ice.

The setting was also rather unfriendly from various perspectives. Our examination of the chemical composition revealed shales The sediments on the ocean floor where this creature and others resided, which have since transformed into stone, indicate deposition under anoxic circumstances (meaning there was no unrestricted circulation of oxygen in the water). Additionally, at certain points, free hydrogen sulfide was present within the sediment. porewaters (The water trapped in small gaps between sediment particles and also above the seabed.) Few organisms could survive under such circumstances, which was crucial for the exceptional preservation of this fossil.

It meant the carcass was not scavenged by other animals after it died. Also, the chemistry was important in the process whereby the soft tissues, which should usually rot away rapidly, became mineralised quickly after death. This turned the animal's anatomy to mineral which survived for hundreds of millions of years until it was discovered.

It is kept "inside out."

Keurbos susanae represents a newly discovered genus and species of early arthropod whose classification remains under investigation. Its internal structures are more intact compared to its external features, making comparisons with other fossils, typically well-preserved externally but not internally, quite challenging.

What led to your discovery of the fossil, and have any other findings come up in that region?

The location is situated in the Cedarberg Mountains, located north of Cape Town. If you wish to gather fossils in this region, you must obtain a permit issued by the authorities. Council for Geoscience . Fossil-bearing rocks are protected by law due to their background and scientific importance.

Searching for fossils in these rock formations demands considerable effort and perseverance, involving the careful use of hammers and chisels to break apart the shale layers. These shale deposits originated as layers of sediment that settled at the bottom of ancient seas. Fossils within this area are extremely uncommon; one could spend numerous days excavating and dividing the shale without unearthing even a solitary fossil. However, previous findings assure us that such treasures do indeed lie hidden within.

I discovered two samples. The initial one is intact, whereas the second sample retains only the central section of its body.

In the same rocks we have found some of the earliest vertebrate fossils with mineralised teeth, called conodonts They had an eel-like appearance and were predatorious. eurypterids (thalattoscorpio), these arthropods possessed strong swimming limbs, allowing them to navigate through the icy seas. Additionally, orthocones - a kind of chambered cephalopod similar to the fossilized mollusks known as ammonites , which have been discovered in abundance, but feature a straight shell rather than a coiled one.

What explains the delay of 25 years in describing Keurbos susanae from a scientific perspective?

Two reasons really.

First, because of the nature of preservation, where all the insides are perfectly preserved but the outside (the carapace or body covering) is absent, it is just difficult to interpret and compare to other fossils. And secondly because the specimen's head and legs are missing and these are key characteristics that palaeontologists would use to help them to understand the evolutionary relationships of such fossils.

If more specimens were to be found, with their heads and legs, we could be more certain about where this fossil fitted in the scheme of life. But the site where I found it has been covered in a lot of rock from quarrying activity. So we decided to describe what we had in the meantime, and not wait for more examples.

The fossils' name, Keurbos susanae, is derived from both the location where they were discovered and as a tribute to my mother, Sue, whose encouragement led me to pursue a career path that brought me joy, regardless of what form it took.

Sarah Gabbott , Professor of Paleontology at the University of Leicester

Provided by Syndigate Media Inc. ( Syndigate.info ).

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