From DISCOVER blogger Ed Yong:

Around 520 million years ago, a walking cactus roamed the Earth. Its body had nine segments, each bearing a pair of armour-plated legs, covered in thorns. It was an animal, but one that looked more like the concoction of a bad fantasy artist. Jianni Liu from Northwest University in Xi’an discovered this bundle of spines and named it Diania cactiformis – the “walking cactus from Yunnan”. And she thinks that it sits at the roots of the most successful group of animals on the planet.

If Liu is right, Diania is one of the earliest relatives of the arthropods – the group that includes insects, spiders, crabs, and more. These species all share a segmented body, a hard external skeleton and jointed legs. They are life’s winners, the most diverse of all animal groups.

For plenty more about this weird ancient armored creature, check out the rest of Ed’s post at Not Exactly Rocket Science.

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80beats: Ancient Invertebrates May Have Formed Chains for Strength in Numbers

Image: Nature

Sponges are just about the simplest animals on the Earth. And they might be the oldest ones we know, too.

Adam Maloof and colleagues published a study in Nature Geoscience this week about their find that could push back the oldest known animal life by 70 million years. In Australia, Maloof says, the team found remains of ancient sponges dating to about 650 million years ago.

The prior oldest known hard-bodied animals were reef-dwelling organisms called Namacalathus, which date to approximately 550 million years ago. Disputed remains for other possible soft-bodied animals date to between 577 and 542 million years ago [Discovery News].

At 650 million years old, the sponges would predate the Cambrian Explosion—a huge blossoming of diversity in animal life—by 100 million years. These organisms would also predate an intense moment in our planet’s history known as “Snowball Earth,” according to paleobiologist Martin Brasier. It’s even possible that they helped cause it.

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In the Cambrian Period, one of the mightiest predators cruising the primeval oceans was a critter about the size of a lobster, researchers say, and it wouldn’t win any beauty contests: “The animal is very strange looking” [New Scientist], says Allison Daley, coauthor of a new study. But even though it measured only about one and a half feet in length, it had enough natural weaponry to dominate the marine food chain about 505 million years ago. “This mouth is kind of nasty. I always use the analogy of a pencil sharpener,” said [study coauthor] Jean-Bernard Caron…. “You put anything into this and you get the prey completely cut and broken into pieces” [Toronto Star].

It took researchers several years of combing through fossils to piece together the bizarre jigsaw puzzle that is Hurdia victoria – an ancestor of arthropods such as insects, spiders and crustaceans…. The first fossilised scraps of Hurdia were discovered in 1912. These were followed by further body parts that were so varied and unusual that they were incorrectly classified as either jellyfish, sea cucumbers or shrimp-like crustaceans [The Independent]. The breakthrough came when paleontologists rediscovered a nearly complete fossil that had been found in the Canadian Rockies almost one hundred years ago, and realized the earlier fragments were all parts of the same species.

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On the seafloor near the Bahamas, researchers have discovered a single-celled organism about the size of a grape, and they say the unusual organism raises interesting questions about the evolution of complex, multicellular animals. The oversized protists were found at the end of long, linear tracks that appear to have been made by the slowly rolling amoebas; lead researcher Mikhail Matz says the tracks resemble fossilized impressions from over 1 billion years ago, which scientists had assumed were made by multicellular worms. “We were looking for pretty animals that have eyes, are coloured, or glow in the dark; instead, the most interesting find was the organism that was blind, brainless, and completely covered in mud,” he said [BBC News].

The origin of multicellular life has been shrouded in mystery, because few animals fossils have been found that predate the beginning of the Cambrian Period around 542 million years ago. Some researchers point to rare Precambrian “trace fossils” – such as slither prints left in ancient sea bottoms – as evidence for complex animal life predating the Cambrian. The oldest of these trace fossils yet found are 1.8 billion years old, about three times older than any animal in the fossil record [The Scientist]. However, the new tracks raise another possibility: that the ancient traces were created by large single-celled organisms.

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A new fossil discovery shows that tiny, shrimp-like invertebrates living 525 million years ago linked up into formations that resemble daisy chains, and researchers say this could be the earliest example yet of animals engaging in group behavior. The fossilized creatures were found in closely interlocked chains of up to 20 individuals, with the tail of one animal inserted into the carapace of the next.

The ancient arthropods, a category of animals that includes insects, crustaceans and spiders, lived in open water rather than remaining on the sea bed. When they died, possibly as a result of moving into water loaded with toxins or short of oxygen, they sank to the seabed, where they were covered in sediment [The Times]. Researchers can’t be certain why the arthropods joined together into chains, but their best guess is that the animals were in the middle of a migration when they perished.

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