Ancient “strange wonders” may be a leftover from the Cambrian Explosion

Researchers unearthed two fossils belonging to ancient, flapping, separate arthropod relatives from what is now a sheep field near Llandrindod Wells in Wales.

At just 13 and 3 millimeters (about 0.5 and 0.1 inch) long, these tiny Ordovician fossils might not seem like much to look at, but their knowledge has kept paleontologists awake at night.

The fossils look like opabiniids–extinct soft-bodied animals with snouts–yet they are dated 40 million years after any known opabiniid fossil.

“Even the sheep know we’re going for something special here, and they usually come to see it,” says Lucy Muir, a paleontologist at the National Museum of Wales.

Dinocaridida, which include opabiniids and radiodonta, were abundant after the Cambrian explosion. These creatures set off across a planet dominated by the ocean about 500 million years ago.

They looked somewhat like trilobites, but all wore a skirt of water-flaps around their bodies; Some had legs and others had strange head appendages. Opabinia has earned the nickname “Strange Wonder” with its awkward and unworldly appearance thanks to its five eyes and strange clawed torso.

Dinocaridida is thought to have descended from the same common “parent” group of animals to the deuteropods, ancient arthropods that gave rise to taxa including spiders, insects, and crustaceans.

While the new finds shared many features with the opabiniids, they had some striking differences as well.

University of Cambridge paleontologist Stephen Bates and colleagues named the largest of the newly described animals Meriden Poniabut they still have to classify the younger type because they are not sure if it is a different type or a younger form of the other type.

“The smaller sample size is comparable to some modern arthropod larvae—we had to factor that possibility into our analyses,” explains Harvard geneticist Joanna Wolff.

The smallest specimens shared a propeller-shaped tail with blades similar to the Opabiniids, and all had similar legs, but the new finds also had snouts—proboscis—with features seen in radiodonta.

Genetic analysis found that with current information, M. bonnieae A friend can be more closely related to either group. If they were part of the opabiniids, these fossils extend the known existence of this group on Earth by 40 million years.

However, “the best supported position of our Welsh specimens, whether considered as one or two species, was more closely related to modern arthropods than to opapinids,” says Bates.

In this case, the proboscis may have resulted from a fusion of the first two head ends which in later related animals were reduced to eventually become the mouth flaps of insects, while x-ray machines found a different use for these ends, making them separate.

The fate of the first two cephalopods is of particular interest because they provided these scaly life forms with the ability to fill many different roles on Earth, from filter feeders to predators. So the researchers take credit for the unparalleled success of arthropods on Earth.

Either scenario would shed light on the evolution of arthropods, which currently account for more than 85 percent of all known animal species on our planet. But we’ll need to discover more “weird wonders” to elucidate this mysterious branch on the tree of life.

This research has been published in Nature Communications.