Tag Archives: Ediacaran

Newly-discovered fossil worm shows early animals were more complex than we thought

The discovery of a new fossil worm shows that life developed symmetrical bodies and locomotion earlier than previously believed.

Image credits Dr. Zhe Chen / Nanjing Institute of Geology and Paleontology.

One of the geological periods in Earth’s history, the Cambrian, is famous for the rapid pace and huge scale of biological development it saw. In the so-called Cambrian explosion (of life), biology experimented with a stunning diversity of animal forms, setting some of the body plans still seen today.

The new fossil, which formed sometime between 551 million and 539 million years ago (in the Ediacaran period, just before the Cambrian), challenges the idea that the Cambrian explosion singlehandedly ushered in modern life.

Old tricks

Life in the Ediacaran was downright weird. Most animals living at the time don’t even use body parts and shapes that you would immediately recognize; most were also unable to move around, preferring to find a spot, bind to it, and make it home.

However, Cambrian life didn’t evolve from scratch — it evolved based on organisms living in the Ediacaran. Fossilized tracks were discovered from the Ediacaran, as well as one odd disk-like creature, but the two didn’t fit.

We now have a better idea of what was moving around in those primordial times. A new paper reports the discovery of Yilingia spiciformis, an Ediacaran worm that is pretty similar to other worms living today. Yilingia had a segmented body, was mobile, and it even appears to have been able to burrow into sediments.

A fossil of Yilingia spiciformis and the track it left as it moved.
Image credits Z. Chen et al., (2019), Nature.

The worm grew to less than 3 centimeters (1 inch) at its widest, but was up to 27 centimeters (nearly a foot) long. It was described based on specimens uncovered in Ediacaran deposits in the Hubei Province, China; the team explains they retrieved 33 samples (many of them partial), and left a 34th specimen in place at the site where it was discovered.

Yilingia’s body was composed of a series of segments. Each segment is divided between a central piece, flanked by two lobes that extend toward its tail. The segments don’t appear to be specialized, only differing in size. It is possible that some of these segments had arthropod-like appendages attached, but the evidence is pretty flimsy so the team reserves their judgment on that point.

The segments near the worm’s head and tail are slightly narrower compared to those in the middle of the body, but Yilingia seems to completely lack a head and tail. The authors describe the evidence for a specialized head as “weak, if not totally absent.”

In order to tell which end was the tail and which the head, the team looked at the tracks the worms left as they crawled on ancient sediments. The team found about a dozen traces in the sediments consistent with tracks being left by Yilingia and a 13th trace which ended at the body of one worm.

Some of the trackways ended at what appeared to be burrows, indicating that Yilingia was able to dig into sediments as well as traverse their surfaces.

Right now, the team is still trying to determine where on the tree of life should Yilingia be. An obvious assignment would be to put it in Annelida, a group that includes many segmented worms. If the limbs turn out to be real, it would probably group with the arthropods. However, arthropods are defined as having compound eyes, a brain, and other features that are absent from Yilingia. The team says it’s possible that the work may be closer to an arthropod ancestor, should the limb issue end up favoring this interpretation.

The main takeaways from this study is that bilaterally symmetric animals, body segmentation, and mobility predate the Cambrian explosion. In other words, these elements were present before the Cambrian and served to fuel the spectacular biological evolution of that period, rather than be created by it.

The paper “Death march of a segmented and trilobate bilaterian elucidates early animal evolution” has been published in the journal Nature.

Mistaken Point

Life went multi-cellular to spread kids around more easily, new research suggests

Life on Earth may have first grown to macroscopic sizes not to compete for food, but to spread their genes far and wide.

Mistaken Point

Ediacaran fossils at Mistaken Point, Newfoundland.
Image credits Emily Mitchell.

Complex life is all about making babies — and spreading them far, according to new research led by the University of Cambridge. In a newly-published paper, they report that the most successful complex species living in the ocean over half a billion years ago were the ones who could spread their offspring the farthest, thus colonizing more land.

Wildest oats

Prior to what geologists refer to as the Ediacaran period (between 635 and 541 million years ago), life on Earth was content to stay microscopic. During the Ediacaran, however, we see the first complex (multicellular) organisms. Some of them, such as the rangeomorphs, could grow up to two meters tall.

We don’t know a whole lot about rangeomorphs. We don’t really know if they were plants or animals, for that matter. What we do know is that they look a lot like ferns and that they’re among the first complex life forms to evolve on the planet — although that’s hard to confirm. Like all other organisms hailing from the Ediacaran, they had no mouths, don’t seem to have had any organs, and lack any obvious means of locomotion — so they were likely filter-feeders, like modern-day clams for example.

One interesting pattern that emerges from the fossil record is that these Ediacaran organisms tended to become more diverse over time — and eventually developed stem-like structures to keep them upright. It was these stems that prompted the research. Plants today also sport stems, and most use height to outcompete their neighbors for resources such as light. But we don’t know if rangeomorph stems served as a means to one-up competitors — although previous research has suggested that their increase in size was driven by competition for nutrients at different water depths.

Ediacaran life.

Artist’s reconstruction of Ediacaran life.
Image credits Ryan Somma / Flikr.

“We wanted to know whether there were similar drivers for organisms during the Ediacaran period,” said Dr Emily Mitchell of Cambridge’s Department of Earth Sciences, the paper’s lead author. “Did life on Earth get big as a result of competition?”

“The oceans at the time were very rich in nutrients, so there wasn’t much competition for resources, and predators did not yet exist. So there must have been another reason why life forms got so big during this period.”

Mitchell and co-author Dr. Charlotte Kenchington, from Memorial University of Newfoundland in Canada, worked with fossils retrieved from Mistaken Point, in south-eastern Newfoundland. This area is one of the richest sites of Ediacaran fossils in the world.

Since Ediacaran organisms were immobile, they were preserved where they lived. As such, the team could analyze entire populations from the fossils. Using spatial analysis techniques, the duo found that there was no correlation between individual size and competition for food. In other words, the rangeomorphs did not tier — they didn’t occupy different parts of the water column to avoid competing for food with their peers.

“If they were competing for food, then we would expect to find that the organisms with stems were highly tiered,” said Kenchington. “But we found the opposite: the organisms without stems were actually more tiered than those with stems, so the stems probably served another function.”

The team believes that the stems were used to enable a greater dispersion of offspring — which rangeomorphs produced by expelling ‘propagules‘. The tallest organisms were surrounded by the largest clusters of offspring, the team found, suggesting that height helped individuals colonize a greater area with their offspring.

Still, about 540 million years ago, rangeomorphs and other Ediacaran organisms disappeared from the fossil record. It’s the Cambrian period now, and evolution is having a blast designing new and surreal creatures — including predators. Rangeomorphs, without the ability to move around, couldn’t do much to protect themselves against these predators.

The paper “The utility of height for the Ediacaran organisms of Mistaken Point” has been published in the journal Nature Ecology & Evolution.

Rangeomorphs.

The earliest large organisms on Earth were shapeshifters

A new paper published by researchers from the University of Cambridge and the Tokyo Institute of Technology could answer why life made the transition from the first really small things to the really large organisms we see today.

Rangeomorphs.

An artist’s impression of rangeomorphs.

Life started out with the tiny bits: proteins, viruses, bacteria, algae. Somewhere along the way, however, it also made the transition towards larger organisms — which is how us, dogs, whales, and so on, got to be here today. But why and when did life perform this transition?

A new study determined that one of the first large organisms we know of, rangeomorphs, were able to grow up to two meters in height at a time when most organisms were still going about on the cellular level. Even more impressively, they were able to change their body’s size and shape as they adapted to environmental conditions. The team’s results could help explain how life as we know it today, and how the giants of the past, could evolve from microscopic organisms.

One size fits all

Rangeomorphs were ocean-dwelling organisms that lived between 635 and 541 million years ago in a period known as the Ediacaran period. Their bodies consisted of branches, each with many smaller side branches, that similarly harbored many tiny branches, forming a fractal. It’s a bit like the shape a snowflake has under a microscope, but with many more sets of branching arms.

Rangeomorphs represent some of the earliest large organisms to evolve on Earth, and could grow from a few centimeters up to two meters in height. But they’re also very strange, as far as life goes. In fact, they’re so strange that there isn’t anything living today that resembles them — so we don’t really know how they fed or grew or made more of themselves, or how they fit into the tree of life. And although they look suspiciously plant-like, researchers believe that rangeomorphs were actually animals.

“What we wanted to know is why these large organisms appeared at this particular point in Earth’s history,” said Dr Jennifer Hoyal Cuthill of Cambridge’s Department of Earth Sciences and Tokyo Tech’s Earth-Life Science Institute, the paper’s first author.

“They show up in the fossil record with a bang, at very large size. We wondered, was this simply a coincidence or a direct result of changes in ocean chemistry?”

To find out, the team used micro-CT imaging and took photographic measurements of rangeomorph fossils uncovered in south-eastern Newfoundland, Canada, the UK, and Australia. They then fed this data into computer models to help them better understand the animals’ physiology.

They report that rangeomorphs show the earliest known evidence of nutrient-dependent growth in the fossil record. Obviously, all organisms depend on nutrients to survive and grow but certain species can actually change body size and shape depending on nutrient availability (ecophenotypic plasticity).

Ediacaran sea life.

Reproduction of what an Ediacaran sea looked like.
Image credits Ryan Somma / Flickr.

Rangeomorphs show a very strong degree of ecophenotypic plasticity, which the team believes gave them a very powerful adaptive advantage. The Earth was going through very dramatic changes in the Ediacaran, and rangeomorphs could rapidly “shape-shift” to adapt to environmental pressures — for example, they could grow to a tall, tapered edge if the seawater above had higher levels of oxygen.

“During the Ediacaran, there seem to have been major changes in the Earth’s oceans, which may have triggered growth, so that life on Earth suddenly starts getting much bigger,” Hoyal Cuthill added.

“It’s probably too early to conclude exactly which geochemical changes in the Ediacaran oceans were responsible for the shift to large body sizes, but there are strong contenders, especially increased oxygen, which animals need for respiration.”

This shifting chemical background came in the wake of a large-scale ice age known as the Gaskiers glaciation. The cold climate kept nutrient levels low, which in turn kept mean organism body sizes low. But a sudden (geologically speaking) increase in free oxygen and nutrients during the Ediacaran period, ecosystems could support much larger organisms, meaning large rangeomorphs could have been a direct result of major changes in climate and ocean chemistry.

But environmental changes would eventually spell their undoing, too. While rangeomorphs were very well adapted to their Ediacaran lifestyle, oceanic conditions continued to change, leading to the ‘Cambrian Explosion‘ — an unprecedented evolutionary development, which saw an immense explosion of biodiversity and to which most major animal groups in the fossil record can trace their ancestry. Between shifting environmental conditions and strong competition and predation, rangeomorphs went extinct.

The paper “Nutrient-dependent growth underpinned the Ediacaran transition to large body size” has been published in the journal Nature Ecology and Evolution.

Scientists find evidence of complex reproduction before the Cambrian

Before the Cambrian, more than 541 million years ago, intriguing creatures named rangeomorphs that grew up to 2 meters dwelt in marine environments. They were unable to move, had no apparent reproductive organs and there is no evidence of them having a gut or a mouth. But a new study has found that their reproductive techniques were surprisingly complex – and surprisingly familiar.

Rangeomorphs are creatures from the enigmatic Ediacaran biota.

To a casual observer, rangeomorphs would look more like plants than animals. They have at times been aligned to a range of modern animal and protist groups, but none of these classifications has stood the test of time – they are an extinct stem group to either the animals or fungi. They’re also a part of the spectacular Ediacaran fauna, the mysterious tubular and frond-shaped, mostly sessile organisms that lived during the Ediacaran Period (ca. 635–542 Ma).

Even among these strange animals, rangeomorphs stand out.

“Rangeomorphs don’t look like anything else in the fossil record, which is why they’re such a mystery,” lead study author Emily Mitchell, a postdoctoral researcher in Cambridge’s Department of Earth Sciences, said in a statement. “But we’ve developed a whole new way of looking at them, which has helped us understand them a lot better — most interestingly, how they reproduced.”

Mitchell and her colleagues looked at rangeomorph fossils in Newfoundland, Canada, and analyzed where the fossils were found one in relationship to another. Because they were immobile, well preserved fossils can show how entire ecosystems lived. They then used a combination of statistical techniques, high-resolution GPS and computer modeling and found an intriguing pattern in population distributions.

According to that analysis, Fractofusus, a type of rangeomorphs, would eject “grandparents” (think of them as seeds or spores) into the water to colonize new areas. They would then produce  “parents” and “children” using stolons, or runners — cloned organisms connected to each other, much like strawberries grow today. The distribution of grandparents was random, while smaller parent and children populations were scattered around them.

The “generational” clustering suggests that Fractofusus reproduced asexually but it’s still unclear if the waterborne seeds or spores were sexual or asexual in nature.

“Reproduction in this way made rangeomorphs highly successful, since they could both colonize new areas and rapidly spread once they got there,” said Mitchell. “The capacity of these organisms to switch between two distinct modes of reproduction shows just how sophisticated their underlying biology was, which is remarkable at a point in time when most other forms of life were incredibly simple.”

This illustration shows a Fractofusus reproduction pattern. Image credits: C. G. Kenchington

This is not the first time a clustering reproduction was reported in pre-Cambrian. A 565-million-year-old tubular invertebrate named Funisia dorothea also reproduced in clusters, according to a 2008 study published in the journal Science. Furthermore, this technique is still used today by corals and sponges.

Rangeomorphs disappeared from the fossil record 540 million years ago as more complex and mobile creatures evolved, making them sitting ducks; it’s difficult to link them to any modern animals, but their technique still survives to this day, a remarkable relic from an inconceivably old period.

Deep Sea ‘mushroom’ is a new branch of life, defying classification in the tree of life

Olesen et al, 2014.

A team of scietists from the University of Copenhagen have found a mushroom shaped animal which they believe doesn’t fit in any known subdivision of the animal kingdom. Such a situation has happened only a few times in the past 100 years.

Researchers aren’t exactly sure where to fit it, but they have a pretty good idea. It’s a multicellular organism, probably related to the jellyfish. What’s even more interesting about them is that they are very similar to strange and poorly understood organisms which inhabited the Earth between 635 and 540 million years ago – in what is called the Ediacaran period. The Ediacaran fauna has is also highly debated and not yet fitted into a clear category of life.

Measuring only a few millimetres in size, the animals consist of a flattened disc and a stalk with a mouth on the end.

The samples were obtained in 1986, over 20 years ago. It’s not uncommon for samples to reach this old age before being thoroughly analyzed, and it’s one of the reasons why the organisms are so hard to classify. If someone were to take newer samples, those would almost certainly prove easier to classify. The samples were preserved in alcohol, which destroys DNA and makes DNA testing somewhere between very difficult and impossible.

“Finding something like this is extremely rare, it’s maybe only happened about four times in the last 100 years,” said co-author Jorgen Olesen from the University of Copenhagen. “We think it belongs in the animal kingdom somewhere; the question is where.”

“What we can say about these organisms is that they do not belong with the bilateria,” said Dr Olesen.

Bilateria are animals with bilateral symmetry, i.e. they have a front and a back end, as well as an upside and downside, and therefore a left and a right. In contrast, radially symmetrical animals like jellyfish have a topside and downside, but no front and back. These new animals could easily be a new branch in the tree of life or an intermediate between two different animal phyla.

Olesen et al, 2014.

Researchers are asking others to look through their collections and see if they have any other samples, which would perhaps be suitable for DNA analysis.

“We published this paper in part as a cry for help,” said Dr Olesen. “There might be somebody out there who can help place it.”

Journal Reference: Jean Just, Reinhardt Møbjerg Kristensen, Jørgen Olesen. Dendrogramma, New Genus, with Two New Non-Bilaterian Species from the Marine Bathyal of Southeastern Australia (Animalia, Metazoa incertae sedis) – with Similarities to Some Medusoids from the Precambrian Ediacara. DOI: 10.1371/journal.pone.0102976

Hallucigenia revealed: the most surreal creature from the Cambrian

Artistic representation of Hallucigenia. Image via The Independent.

It looks like a painting from Salvador Dali – but Hallucigenia was very much real. Truly one of the most surreal creatures to ever walk the face of the planet, it was finally deciphered and understood (at least partially) by paleontologists, after 4 decades of study. The process discovered not only its position in the tree of life, but also its only surviving descendants.

Life on Earth was pretty dull until the Cambrian explosion, but it was never dull after it. The Cambrian is the time when most of the major groups of animals first appear in the fossil record. This event is sometimes called the “Cambrian Explosion,” because of the relatively short time over which this diversity of forms appears. It was a period of evolutionary experimentation; animals with complex body plans evolved walking, swimming, crawling and burrowing. Numerous diverse creatures appeared, including Anomalocaris (a 1 meter predator with moving lobes on the side of its body and 2 arm-like features next to its mouth), Diania (spiny animals with 10 pairs of legs) and the more famous trilobites. But even with this explosion of life, with this diversification to fill out every single niche out there, Hallucigenia still seems surreal. Believe it or not, paleontologists now believe that it is related to a small group of worm-like creatures with short legs that inhabit the underground of some tropical forests.

Anomalocaris. Image Source: The Cambrian Explosion: The Construction of Animal Biodiversity

Martin Smith and Javier Ortega-Hernandez of Cambridge University have detected key physical similarities between Hallucigenia and the so-called velvet worms, known more formally as the onychophorans – organisms with tiny eyes, antennae, multiple pairs of legs and slime glands. Their study, which was published in Nature, shows five key characteristics that link the species to the velvet worms.

A Hallucigenia fossil found in the Burgess shale. Image credits: Smithsonian.

In order to reach this conclusion they had to create high-magnification images of the fossils of Hallucigenia, which grew no longer than 3.5 cm. The first thing they found was the way the claws at the end of its limbs are arranged. Under an electron microscope, each claw has two or three successive layers of cuticle nestled one within the other, like the layered skins of an onion. Dr Smith said:

“We think this enabled them to grow a new set of claws before they shed their skins, which they had to do to grow. A very similar feature is found in the claws and jaws of the velvet worms, and no other animal shares this particular characteristic. It means that the animals do not have to wait for a new claw to form after shedding their skin to grow – they already have one ready formed,” he explained.

In fact, paleontologists have never been sure what is Hallucigenia’s front and what is its back – but this study clears that out too: the front has two or three pairs of appendages and the back has a rounded end where the gut probably terminates. They also showed that the fearsome spikes on Hallucigenia’s back were wrongly confused for legs, and were in fact a defense mechanism against the growing number of Cambrian predators.

For biologists and paleontologists, the Cambrian is probably the most interesting period of all geological history. It’s the period where life as we know it started to shape up. At one time in history, it was thought that life originated in the Cambrian, but now we know that in order to evolve, it has to evolve form something – and geologists have since found numerous evidence of pre-Cambrian life, most notably the Ediacaran fauna and the 3.5 billion years old stromatolites.

Dickinsonia costata, an iconic Ediacaran organism, displays the characteristic quilted appearance of Ediacaran enigmata. Image via Wiki Commons.

“It’s often thought that modern animal groups arose fully formed during the Cambrian explosion. But evolution is a gradual process,” said Martin Smith of Cambridge. “Today’s complex anatomies emerged step by step, one feature at a time. By deciphering ‘in-between’ fossils like Hallucigenia, we can determine how different animal groups built up their modern body plans,” he said.

 Journal Reference: Martin R. Smith, Javier Ortega-Hernández. Hallucigenia’s onychophoran-like claws and the case for Tactopoda. Nature, 2014; DOI: 10.1038/nature13576

One of the fossils in question - Dickinsonia. Currently, scientists are positive this was a sea-dwelling invertebrate, but recent findings suggest it may actually have been a land-dwelling lichen. (c) Greg Retallack

Controversial study challenges tree of life and claims complex life first originated on land

Professor Gregory Retallack of  University of Oregon has launched a highly controversial claim that stirred the scientific community recently, implying that ancient fossils found in South Australia from Ediacaran period, a geological time that preceded the great Cambrian explosion, were actually living being living on land, not water as “common sense” dictates.

One of the fossils in question - Dickinsonia. Currently, scientists are positive this was a sea-dwelling invertebrate, but recent findings suggest it may actually have been a  land-dwelling lichen. (c) Greg Retallack

One of the fossils in question – Dickinsonia. Currently, scientists are positive this was a sea-dwelling invertebrate, but recent findings suggest it may actually have been a land-dwelling lichen. (c) Greg Retallack

The Ediacaran period ended some 540 million years ago, and during these geological times life on Earth was highly primitive, comprised of individual cells organized in colonies at best.  Ediacaran fossils have been thought of as fossil jellyfish, worms and sea pens, however Retallack argues that he has found evidence that these invertebrates actually originated on land – a claim that has severe implications for our understanding of how life evolved on our planet.

“This discovery has implications for the tree of life, because it removes Ediacaran fossils from the ancestry of animals,” says Retallack, who is originally from Australia.

“These fossils have been a first-class scientific mystery,” he posited. “They are the oldest large multicellular fossils. They lived immediately before the Cambrian evolutionary explosion that gave rise to familiar modern groups of animals.”

Using an assortment of high-tech chemical and microscopic technique, including electron microprobe and scanning electron microscope, Retallack claims he has found soils with fossils that are distinguished by a surface called ‘old elephant skin,’ which is best preserved under covering sandstone beds.

“They show variation in chemistry, variation in grain size, and variation in clay minerals that is quite comparable with a modern desert soil,” he says.

“The key evidence for this new view is that the beds immediately below the cover sandstones in which they are preserved were fossil soils,” Mr. Retallack said. “In other words the fossils were covered by sand in life position at the top of the soils in which they grew. In addition, frost features and chemical composition of the fossil soils are evidence that they grew in cold dry soils, like lichens in tundra today, rather than in tropical marine lagoons.”

Bold claims

Moreover, the geologist claims that many  Ediacaran fossils exhibit features that he believes resemble today’s lichens, than marine invertebrates as the current scientific consensus,  and he also says there is evidence the land they were growing on was sometimes frozen.

This means the Ediacaran fossils represent “an independent evolutionary radiation of life on land that preceded by at least 20 million years the Cambrian evolutionary explosion of animals in the sea.”

Mr. Retallack says that elevated chemical weathering by organisms on land may have been necessary to propel the demand of nutrient elements by Cambrian animals, and based on other fossils from the Cambrian period similar to those studied by him from the Ediacaran, the geologists goes as far to say life on land may have been more complex than life in the sea during the Cambrian explosion. If this is true, then Ediacaran fossils represent an independent branch on the tree of life.

Of course, such a controversial theory was followed by a wave of protest, as scientists called for more substantial evidence to back up the claims.

“I’m sorry, I’m not a creationist. I do not believe that the Cambrian animals popped into existence out of the blue at the beginning of the Cambrian,” Dr Jim Gehling of the South Australian Museum comments on the paper, referring to the fact that if the Ediacaran fossils are  not of marine origin, than the whole boom of life from the Cambrian simply came from “nothing”.

“It’s the right of every scientist to put up controversial hypotheses but you really have to have good evidence if you want to set up a new paradigm,” he says.

Tree of life revamp

Many scientists have no doubts concerning the marine ancestry of the Ediacaran fossils, pointing to wave ripples and other features only formed in marine environments.  Retallack tackles back these comments stating these ripple features could have very well come from subsequent  floods or lakes. Regarding Retallack’s chemical analysis that revealed evidence of fossils soils, Gehling believes these are mere contaminants from more recent weathering events of the ancient rock outcrops that the fossils are found in. Present scientific consensus has that animals only crawled onto land 100 million years after the Ediacaran.

“I find Retallack’s observations dubious, and his arguments poor. That this was published by Nature is beyond my understanding,” wrote Martin Brasier, a paleobiologist at the University of Oxford.

Retallack doesn’t seem bothered at all by the fact that his hypothesis warrants a whole revamp of the current life evolution cycle we call tree of life. On his part, life on land before the Cambrian evolution makes perfect sense as it would have changed the soil chemistry, he says, allowing the release of mineral ions into the soil water.

“Some of this soil water runs off into streams end eventually the ocean,” says Retallack. “That is going to be the engine that drives the Cambrian explosion.”

“What we’re looking at here is the early stages of the ramping up of that process to create the nutrients needed for animal life in the sea.”

Retallack’s findings were published in the journal Nature.

Artist impression of the Coronacollina, the earliest animal with a skeleton. (c) Daniel Garson for Droser lab, UC Riverside.

Earliest animal with a skeleton discovered, pre-Cambrian

The Cambrian era marked a profound change on life on Earth, sparking the rapid development of complex organisms and a diversification of the ecosystem, thus the term “Cambrian explosion“. Prior to this period, animals were simple and small, as well as soft bodied, with no hard parts to display. A team of paleontologists at University of California, Riverside, however, made a monumental discovery recently, namely they found fossil evidence for an organism with individual skeletal body parts dating from before the Cambrian. This makes it the earliest animal with a skeleton.

Artist impression of the Coronacollina, the earliest animal with a skeleton. (c) Daniel Garson for Droser lab, UC Riverside.

Artist impression of the Coronacollina, the earliest animal with a skeleton. (c) Daniel Garson for Droser lab, UC Riverside.

Dubbed Coronacollina acula, the animal is between 560 million and 550 million years old, placing it in the Ediacaran period, the first period of the Paleozoic Era and of the Phanerozoic Eon. The fossil was found in Australia, and after an exhaustive study, it was found to present a depression measuring a few millimeters to 2 centimeters deep – the Coronacollina acula. Since rocks compact over time, however, researchers believe it was actually somewhere 3 to 5 centimeters tall, featuring a thimble-shaped body. Attached to its body, at least four 20 to 40 cm long needle-like “spicules” were present, which the animal most likely used to keep itself atop, despite being considered incapable of locomotion. It lived on the seafloor.

“We now have an organism with individual skeletal body parts that appears before the Cambrian. It is therefore the oldest animal with hard parts, and it has a number of them – they would have been structural supports – essentially holding it up. This is a major innovation for animals,” said lead scientist Mary Droser.

Indeed this is terribly exciting news, one which most likely will go on to provide scientists with important insights. For instance, the creature’s structure resembles the manner in which Cambrian sponges were constructed, hence possibly providing a link between the two periods.

“We’re calling it the ‘harbinger of Cambrian constructional morphology,’ which is to say it’s a precursor of organisms seen in the Cambrian. This is tremendously exciting because it is the first appearance of one of the major novelties of animal evolution,” Droser says.

This link is of extremely important consequence, impacting current theories on the Cambrian explosion. For years, scientists believed that skeletons only appeared once with the Cambrian, and this latest remarkable find serves as evidence that Ediacaran animals are part of the evolutionary lineage of animals as we know them.

“The fate of the earliest Ediacaran animals has been a subject of debate, with many suggesting that they all went extinct just before the Cambrian,” Droser said. “Our discovery shows that they did not.”

“We often associate skeletons with predation since skeletons greatly assist animals in their fight against predators,” Droser said. “But Coronacollina acula used its skeleton only for support, there being no predators in the Ediacaran.”

The findings were published in the journal Geology.

University of California, Riverside press release via Scienceagogo