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Three-eyed extinct creature named Kylinxia reveals details of early animal evolution

Scientists have discovered an extinct animal, which they have named Kylinxia, that has revealed important insights into how animals were evolving over 500 million years ago.

A multidisciplinary team of experts from the University of Leicester, Yunnan Key Laboratory for Palaeobiology, the Institute of Palaeontology at Yunnan University, Chengjiang Fossil Museum, and the Natural History Museum in London, have redefined our understanding of a pivotal moment in the evolutionary timeline of arthropods.

The narrative they’ve unveiled reshapes the story of a class of creatures that eventually gave rise to the myriad forms of arthropods we see today, from lobsters and crabs to spiders and insects.

The protagonist of this evolutionary tale is Kylinxia, an ancient animal whose fossil has been encased in rocks nearly 520 million years old. What’s particularly exciting about Kylinxia is not just its antiquity, but the startling features it possessed.

Imaged with a CT scanner, revealing the soft anatomy buried deep within the rock, it bore an uncanny resemblance in size to a large shrimp. But the similarities largely end there; this creature had three eyes mounted on its head and boasted a pair of formidable limbs, presumably serving as weapons to snatch unsuspecting prey.

How scientists discovered Kylinxia

Published this week in the esteemed journal, Current Biology, this discovery is a testament to the rich tapestry of life in a bygone era. Around half a billion years ago, our planet’s oceans teemed with a burgeoning community of marine creatures.

The Chengjiang region in southern China stands as a veritable treasure trove for these fossilized relics. It hosts over 250 species of immaculately preserved organisms from the Cambrian Chengjiang biota. This find from Yunnan Province enriches the ever-evolving understanding of arthropod evolution.

While arthropods – creatures with segmented bodies and jointed limbs – are not strangers to the fossil record, much of our knowledge stems from specimens like trilobites which primarily preserved their hard exoskeletons. The revelation of Kylinxia, however, goes far beyond skeletal remains.

This nearly complete specimen enabled scientists to discern the animal’s head. It revealed a six-segment configuration: a frontal segment adorned with eyes, a second segment armed with large, grasping limbs, followed by four segments each flaunting a pair of jointed appendages.

Scientists are left awestruck by discovery

The primary author, Robert O’Flynn, is a PhD student from the University of Leicester’s School of Geography, Geology and the Environment. He couldn’t contain his awe, saying, “The preservation of the fossil animal is amazing. After CT-scanning we can digitally turn it around and literally stare into the face of something that was alive over 500 million years ago. As we spun the animal around, we could see that its head possesses six segments, just as in many living arthropods.”

Reflecting on the significance of Kylinxia, Professor Mark Williams, Robert’s primary supervisor, shared, “Kylinxia, and the Chengjiang biota whence it came, are instrumental to building our understanding of early euarthropod evolution. I like to think that similar discoveries will continue to be made by Robert.”

While examining the micro-CT data, Professor Yu Liu from the Yunnan Key Laboratory for Palaeobiology revealed, “Robert and I were hoping to refine and correct previous interpretations of head structures in this genus, Kylinxia. Amazingly, we found that its head is composed of six segments, similar to insects.”

Adding to this Dr Greg Edgecombe from the Natural History Museum remarked, “Most of our theories on how the head of arthropods evolved were based on these early-branching species having fewer segments than living species. The discovery of two previously undetected pairs of legs in Kylinxia suggests that living arthropods inherited a six-segmented head from an ancestor at least 518 million years ago.”

In decoding the mysteries of Kylinxia, science has once again shown that the past holds the key to understanding the intricate web of life that surrounds us today.

More about arthropods

Arthropods, a vast group of invertebrates, dominate the animal kingdom with over a million described species. They possess jointed limbs, a segmented body, and an exoskeleton made of chitin.

Insects, like bees and butterflies, represent the largest arthropod class. They generally have three body parts — head, thorax, and abdomen — and primarily inhabit terrestrial environments. Butterflies, with their vividly colored wings, undergo metamorphosis, transforming from larvae to adults.

Arachnids, another class, include spiders, scorpions, and mites. They have two main body parts and eight legs. Spiders, known predators, trap prey using intricate webs.

Crustaceans encompass crabs, lobsters, and shrimp. Found mainly in aquatic habitats, they boast hard exoskeletons that they must shed to grow — a process called molting.

Myriapods include centipedes and millipedes. They reside on land and possess numerous legs, with centipedes being carnivorous and millipedes mainly herbivorous.

Arthropods play vital ecological roles. Bees, for instance, pollinate plants, ensuring fruit and seed production. Meanwhile, spiders help control insect populations. In summary, arthropods, with their diversity and adaptability, remain a pivotal group in the animal kingdom, influencing ecosystems worldwide.

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