Tag Archives: cambrian explosion

The oldest animal life on Earth was discovered in Canada: 890 million years old

A Canadian paleontologist may have found the earliest evidence of life on Earth — and it’s much older than we thought.

a. and b. show the fossils that Turner believes show evidence of sponge life; compared with the spongin skeleton of a modern sponge, shown in c. Image credit: Turner, 2021, Nature CC by 4.0

Life as we know it took a pretty funky turn around 541 million years ago. That’s when a period called the Cambrian emerged, and with it, the so-called Cambrian explosion ushered in practically all major groups of animals. It lasted for about 25 million years and resulted in the divergence of life as we know it.

Before the Cambrian explosion, life on Earth was simple and small. It was composed either of individual cells, or of microscopic, multicellular organisms — or at least so we thought.

Scientists have found some evidence of animal life existing before the Cambrian. In particular, some sponges (immobile aquatic animals) seem to have emerged before the Cambrian. But how long before it?

According to a recent study, the first sponges emerged a whopping 350 million years before the Cambrian — or 890 million years ago.

“If I’m right, animals emerged long, long before the first appearance of traditional animal fossils,” study author Elizabeth Turner told Nature. “That would mean there’s a deep back history of animals that just didn’t get preserved very well.”

The fossils discovered by Turner, from a remote area of northwestern Canada accessible only by helicopter, resemble some modern sponges known as keratose demosponges. The researchers dated the layer of rocks in which the sponge fossils were found, a solid analysis tool that leaves little room for question regarding the fossils’ age. The identification as sponges also seems pretty clear.

“This organic skeleton is very characteristic [of sponge fossils],” explained geobiologist Joachim Reitner, who reviewed Turner’s study ahead of publication. “[T]here are not known comparable structures.”

But a finding that would force us to reconsider the evolution of life on Earth won’t happen easily, and Turner’s peers are rightfully raising all sorts of questions regarding the fossils. Some point out that the findings may not be fossils at all (but rather other structures), while others are focusing on another question: if life emerged a few hundred million years before the Cambrian, why haven’t we found any fossils of it until this?

Ultimately, if the finding is confirmed, it will help us understand the evolution of life on Earth.

“We are animals,” Turner said. “And we have a big brain, and we’re capable of wondering about stuff, and we wonder how we came to be. 

“What happened before, and what was it like? How did it begin?” she said. “This is really digging into that. I’m shaking up the apple cart.”  

The study has been published in Nature.

The world’s first animals also caused the first global warming event — but it took 100 million years

At first, life on Earth was pretty peaceful — bacteria and plants did their thing without any problems. But then, the pesky animals came along and started ruining things.

Cambrian rocks.

To be fair, life must have been pretty dull at first. But when the Cambrian came in 541 million years ago, things started to change, and they changed dramatically. The so-called Cambrian Explosion brought the evolution of diverse and bizarre ecosystems, the likes our planet had never seen before. Now, a new study found that as the first animals emerged on the ocean floor, they started breaking down the fallen organic matter, leading to more carbon dioxide and less oxygen in the atmosphere.

“Like worms in a garden, tiny creatures on the seabed disturb, mix and recycle dead organic material – a process known as bioturbation,” said Professor Tim Lenton, from the University of Exeter.

“Because the effect of animals burrowing is so big, you would expect to see big changes in the environment when the whole ocean floor changes from an undisturbed state to a bioturbated state.”

After carrying out computer models, researchers found that oxygen levels in the atmosphere did seem to decline about 520 million years ago, but the sediment was only a little disturbed. They actually found that the biggest changes happen at the lowest levels of animal activity — which indicates that the first Cambrian animals, which didn’t move around all that much, were largely responsible for the reduction in atmospheric oxygen and the subsequent global warming.

Dr. Benjamin Mills, also from the University of Leeds, who led this part of the research, said:

“When we ran our model, we were surprised by what we saw. The evolution of these small animals did indeed decrease the oxygen in the ocean and atmosphere, but also increased atmospheric carbon dioxide levels to such an extent that it caused a global warming event.”

“We knew that warming occurred at this point in Earth history, but did not realise it could be driven by animals.”

Ironically, the climate change these animals brought made living significantly more difficult, contributing to a number of important extinction events over the following 100 million years.

Also ironically, there’s a clear parallel to be drawn between what these creatures unwittingly did hundreds of millions of years ago, and what we are doing now.

“There is an interesting parallel between the earliest animals changing their world in a way that was bad for them, and what we human animals are doing to the planet now,” said Professor Lenton, director of Exeter’s new Global Systems Institute, which aims to develop transformative solutions to the challenges facing the world today.

“We are creating a hotter world with expanding ocean anoxia (oxygen deficiency) which is bad for us and a lot of other creatures we share the planet with.”

The paper “Early Palaeozoic ocean anoxia and global warming driven by the evolution of shallow burrowing” has been published in Nature Communications.

Scientists find ‘nude’ creature that lived half a billion years ago

Scientists have discovered the unusual creature in Cambrian rocks, and they’re not exactly sure where it fits in the tree of life.

The new species of fossil chancelloriid: an enigmatic animal from the Cambrian Period with a tube-like body, minotaur-horn spines, and doughnut-shaped scars. Image credits: Derek Siveter/Tom Harvey/Peiyun Cong.

Before the Cambrian, life on Earth was rather dull. Mostly microscopic, simple, and bland. But that all changed during the Cambrian Explosion — a period of intense evolutionary diversification, where most major animal phyla appeared in the fossil record. The Cambrian Explosion also made way for some incredibly bizarre creatures to emerge, like Hallucigenia — a worm-like tubular organism with seven or eight pairs of slender legs, each terminating in a pair of claws, and long spines on its body. Now, researchers have found yet another unusual Cambrian creature: a large-bodied ‘nude’ sea-creature belonging to the mysterious groups of animals known as the chancelloriids.

Classifying chancelloriids is a difficult task. Some paleontologists see them as sponges, based on their simple structure and immobile lifestyle. Others believe they were more advanced, or at least that they developed from advanced ancestors, a theory backed by the chancelloriids’ skins, which appear to be much more complex than those of any sponge we’ve seen. It’s also been suggested that chancelloriids were related to the “chain mail” armored slugs of the Cambrian. The new discovery by a team of scientists from the University of Leicester, the University of Oxford and Yunnan University, China, adds new evidence that could help solve the mystery.

Chancelloria eros, which is related to the newly-discovered fossil, looks very different. Image credits: James St. John.

The new species, named Allonnia nuda, was discovered in the Chengjiang deposits of Yunnan Province, China. It was surprisingly large compared to its relatives (measuring 50 cm or more), but had only a few tiny spines — hence the “naked” name. This unusual appearance suggests that other specimens might have been discovered before, but not properly identified, and might be hiding in plain sight in fossil collections.

The finding also shows that the group is more diverse than believed. Dr Tom Harvey, from the University of Leicester’s School of Geography, Geology and the Environment, explains:

“Fossil chancelloriids were first described around 100 years ago, but have resisted attempts to place them in the tree of life. We argue that their pattern of body growth supports a link to sponges, reinvigorating an old hypothesis. We’re not suggesting that it’s “case closed” for chancelloriids, but we hope our results will inspire new research into the nature of the earliest animals.”


Journal Reference: Cong, P.-Y., Harvey, T. H. P., Williams, M., Siveter, D. J., Siveter, D. J., Gabbott, S. E., Li, Y.-J., Wei, F., & Hou, X.-G. 2018 Naked chancelloriids from the lower Cambrian of China show evidence for sponge-type growth. Proceedings of the Royal Society B, 20180296. doi: 10.1098/rspb.2018.0296

Earth’s first giant predators produced killer babies

The “creepy crawly” animal group known as the Arthropoda, which includes spiders, insects, and crustaceans, has been responsible for producing many scary creatures. But few of them, if any, were as terrifying as the Radiodonta.

Estimates of how different Radiodonta species would have looked like. Image credits: Renato de Carvalho Ferreira.

The Radiodonta (literally meaning “radiating teeth”) are the earliest large predators ever discovered. They had no proper legs, their member being turned into fin-like lateral flaps, helping them chase and catch their prey. They were armed with large, spiny raptorial (or grasping) appendages at the front of the head, and the mouth was surrounded by a ring of radiating tooth plates, hence their name.

During the Cambrian period, 500 million years ago, these early predators were patrolling the seas, looking for any unfortunate creatures to hunt and kill. As if they weren’t scary enough on their own, their babies were also killing machines, a new study has shown.

Researchers working in China have identified an exceptionally-preserved juvenile of a species called Lyrarapax unguispinus from the early Cambrian (518 million-year-old). The specimen measures only 18 mm, is extraordinarily well developed, even featuring the spiny grasping appendages. Essentially, the juvenile looks like a miniature adult.

Since these appendages were used for only one purpose (hunting and killing), researchers believe that Lyrarapax was perfectly equipped for hunting, even from an early age.

As if adults weren’t scary enough, the babies were also killing machines. Image credits: Science China Press.

This is not an ancient or a unique feature: modern praying mantises, mantis shrimps, and arachnids also produce well-equipped offspring, suggesting that this feature emerged early in the evolutionary history of arthropods. The fossil also offers an important piece of evidence for understanding 500-million-year-old environments, as well as one of the most dramatic events in Earth’s biological history: the Cambrian Explosion.

This was possibly the most important evolutionary event in the history of life on Earth. It represents the period when most major animal phyla appeared in the fossil record, and also when the first true predators emerged. Predators changed the entire structure of ecosystems, as they introduced a previously inexistent requirement for creatures: the need to avoid being hunted.

It’s estimated that the emergence of these predators was a major driver of this evolutionary event: predators placed strong selective pressures on animal communities, forcing prey species to adapt and evolve or face extinction.

The fact that the juvenile radiodonts were seemingly fierce hunters from their earliest stages only increases these pressures, especially on smaller creatures.

Journal Reference: Liu, J. N., Lerosey-Aubril, R., Steiner, M., Dunlop, J. A., Shu, D. G. & Paterson, J. R. 2018.Origin of raptorial feeding in juvenile euarthropods revealed by a Cambrian radiodontan. National Science Reviewhttps://doi.org/10.1093/nsr/nwy057

Nope, octopuses probably didn’t come from outer space

This guy is probably not an alien.

If you’ve been following the science news, you’re probably aware of the new study claiming octopuses come from outer space. “Octopuses are from space, scientists say” was one of the catchy headlines published in Australia, while The Express wrote that “Octopuses came to Earth from space as frozen eggs millions of years ago”. These aren’t two cherry-picked instances, the internet was abuzz with variations on the same theme. Unfortunately, however, this is almost certainly not the case. Let’s see what really happened.

What the study says

The new study, penned by over 30 researchers, essentially rehashes the theory of panspermia — the idea that life on Earth emerged in outer space, hitching a ride on meteorites or other objects that crashed into Earth at one point, something often referred to as the Hoyle-Wickramasinghe (H-W) thesis of cosmic biology.

The research starts from the Cambrian Explosion an event approximately 541 million years ago, during an age called the Cambrian period. The Cambrian Explosion was an age of extreme diversification of life, during which most major animal phyla started to emerge. The study’s authors question whether that happened naturally, with just the elements existing on Earth.

“One particular focus are the recent studies which date the emergence of the complex retroviruses of vertebrate lines at or just before the Cambrian Explosion of ∼500 Ma. Such viruses are known to be plausibly associated with major evolutionary genomic processes. We believe this coincidence is not fortuitous but is consistent with a key prediction of H-W theory whereby major extinction-diversification evolutionary boundaries coincide with virus-bearing cometary-bolide bombardment events,” the study reads.

Cartoonish depiction of life in the Cambrian. Alien-like? Sure! Alien? Probably not. Image credits: Rice University.

In other words, what they’re saying is that life didn’t just emerge on its own, it was “seeded” from life-bearing comets that pummeled our planet at various times throughout history. These comets could have brought a myriad of novel life-forms from other planets, including viruses. This is one of the main assumptions of the H-W thesis — that small bodies such as asteroids and comets can protect the “seeds of life”, including DNA and RNA. So far, so good; this is a plausible idea, that has been investigated since the 1970s and continues to be analyzed by various groups. There’s not much evidence to say that it did happen, but with what we know so far, it might have happened.

Then, the authors make a big leap: if you’re not convinced by the panspermia theory, you need not look farther than the octopus. Octopuses have very complex nervous systems and big, specialized eyes — two unprecedented features.

“A second focus is the remarkable evolution of intelligent complexity (Cephalopods) culminating in the emergence of the Octopus,” the study continues.

This is where it starts to get thorny. Cephalopods, the group in which octopuses belong, did emerge in the Cambrian — the fossil records clearly suggest so. But the early cephalopods were Nautiloids, a very diverse group of creatures which exist to this day. But Nautiloids look completely different to octopuses, and they don’t share many of their impressive features. In fact, octopuses didn’t emerge until the Devonian, 323 million years ago. This means that there’s a window of over 200 million years from the Cambrian explosion to when the first true octopuses emerged, which is plenty of time to selectively develop specialized features (there are studies which say octopuses developed a bit earlier, but not significantly in this context).

Artistic depiction of Orthoceras — an early nautiloid. Image credits: Nobu Tamura.

Furthermore, when the octopus genome was mapped in 2015, it was shown that the nervous system genes split from the squid’s only around 135 million years ago — again, long after the Cambrian explosion. In all practicality, the evolution of the octopus was never really regarded as a mystery requiring additional explanation. This is an ancient group with some remarkable features, but these features didn’t appear in the earliest creatures, developing gradually over the course of hundreds of millions of years.

Occam’s Razor

Instead, what the new study suggests is that fertilized octopus eggs hitcher a ride aboard an icy comet and crashed into the sea at the onset of the Cambrian explosion. Alternatively, researchers write, an extraterrestrial virus infected a population of early squid, causing them to evolve in this unusual way. The genes responsible for the octopus evolution, they say, don’t appear to have come from their ancestors.

“The transformative genes leading from the consensus ancestral nautilus to the common cuttlefish to squid to the common octopus are not easily to be found in any pre-existing life form,” the study, published in Progress in Biophysics and Molecular Biology, claims.

“It is plausible then to suggest they seem to be borrowed from a far distant ‘future’ in terms of terrestrial evolution, or more realistically from the cosmos at large.”

Again, this is technically possible. It might have happened. But that doesn’t mean it did. Occam’s razor suggests that the simpler explanation is usually the better, and this is probably the case here — there’s no reason to go and speculate about extraterrestrial origins.

It’s noteworthy that in his review of the paper, medical researcher Keith Baverstock from the University of Eastern Finland, concedes that there’s a lot of evidence that plausibly aligns with the H-W thesis, such as the curious timeline of the appearance of viruses — and yet, herein lies the problem: plausibility does not mean probability. Basically, just because something can happen doesn’t mean it did. The new paper goes to great lengths to prove that it could happen, and to open some interesting discussions. Make no mistake, this is not an amateurish study published in a predatory journal. However, the scope of the paper is oversold, and as Ken Stedman, a virologist and professor of biology at Portland State University, told Live Science, the authors didn’t carefully review existing literature, and they make extremely speculative claims.

Of course, mainstream media was all over this. The idea that life on Earth came from outer space is terribly appealing — particularly when we’re talking bizarre creatures like octopuses, and everyone gasped at the idea of an alien octopus. Unfortunately, that’s probably not the case. Octopuses are fascinating creatures, and I hope we can cherish them even if they’re not aliens.

Journal Reference: Steele et al. “Cause of Cambrian Explosion – Terrestrial or Cosmic?”, Progress in Biophysics and Molecular Biology. https://doi.org/10.1016/j.pbiomolbio.2018.03.004

Credit: Pixabay.

How algae prepared the ground for complex life 650 million years ago

Credit: Pixabay.

Credit: Pixabay.

Algae look boring and smell awful, but really, life on Earth would never be the same without them. Rich in iodine and several other important minerals, algae provide an essential food source whose nutrients migrate from the very bottom to the top of the food chain. Never were algae more important than 650 million years ago, though. Oddly enough, these simple life forms were some of the most complex at the time, surrounded by an ocean of single-celled bacteria. In a new paper, scientists argue that around that time algae population jumped a hundred to even a thousand fold. Ultimately, this planetary algae bloom set the stage for the most critical turning point in life’s history: the Cambrian explosion.

Food for thought

Life on Earth was pretty dull until the Cambrian explosion, but it was never dull after it. As Andrei eloquently put 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.

This remarkable turn of events, however, couldn’t have come out of nowhere. Every explosion has a fuse, Jochen Brocks, a researcher at the Australian National University, has a hunch algae had a eukaryotic hand in all of this.

Mushy algae, of course, leave no fossil traces but what Brocks and colleagues found where molecular remnants of their cell walls, which are closely related to the cholesterol found in our blood. This makes them very stable and when ancient algae decomposed, these fat molecules were absorbed by sediments where they remained trapped for eons.

The rise of the algae

About 700 million years ago, runaways glaciers covered the entire planet in ice. Credit: NASA.

About 700 million years ago, runaways glaciers covered the entire planet in ice. Credit: NASA.

By painstakingly analyzing the molecular signal and separating fossil fuel contaminants, the team found algae populations rose dramatically around 650 million years ago. In a geological timeframe, this bloom happened right after the ‘Snowball Earth’ — a time when the planet became almost entirely engulfed in ice and snow. The equator, one of the hottest latitudes today, had average temperatures of around -20°C (-10°F), roughly similar to present Antarctica.

This white hell ended after about 50 million years when volcanic CO2 build-up heated the atmosphere enough to bring temperatures back into sensible limits, as far as life is concerned. Brocks believes that this massive shift grounded rocks, causing them to release phosphate — an essential nutrient and common fertilizer used in agriculture. This was the food that would explain the planetary algae bloom and the algae, in turn, would provide the food for the first animals, simple sponges.

Of course, this is quasi-speculating — it’s still the best explanation we have for why life took so long to make the big step from dull unicellular organisms to a more complex and diverse biosphere which would ultimately lead to humanity’s evolution. Consider algae had been around for more than a billion years before this ‘great boom’. The rebound after the Snowball Earth seems like the kick in the hide that life needed.

“We could not have made our discovery in any more exciting period,” Brocks wrote. “The close temporal connection between the melting of the Snowball, rising nutrient levels in the oceans, the rise of algae and the evolution of animals immediately suggest that these events must be linked.”

Findings appeared in the journal Nature.

Illustration of Capinatator praetermissus. (Drawing by Marianne Collins. Copyright Royal Ontario Museum.)

Newly identifed 500-million-year old ancient worm had 50 spines bulging from its head

Illustration of Capinatator praetermissus. (Drawing by Marianne Collins. Copyright Royal Ontario Museum.)

Illustration of Capinatator praetermissus. (Drawing by Marianne Collins. Copyright Royal Ontario Museum.)

Some half a billion years ago, life on Earth underwent one of its biggest turning point in history. This was the Cambrian explosion, a sudden appearance in the fossil record of complex animals with mineralized skeletal remains. It was during this time that the first arthropods with legs and compound eyes appeared, but also worms with feathery gills and swift predators that could crush prey in tooth-rimmed jaws. One such creature, Capinatator praetermissus, a four-inch long marine predator, was recently identified by Yale University and the Royal Ontario Museum as reported in Cell Biology.

An experimental being

This is the most significant fossil discovery of this group of animals yet made,” said Derek Briggs, a Professor at Yale and curator at the Yale Peabody Museum of Natural History.

Researchers had previously collected about 50 fossil specimens of Capinatator p. from the fossil-rich Burgess Shale in British Columbia, but it was only recently that they fitted all the puzzle pieces together. What they ended up with was a predatory worm called a chaetognath, and this specimen is the biggest chaetognath we’ve found so far, living or fossil.

Even so, it was pretty tiny by today’s standards. Scientists believe Capinatator was the forerunner of today’s smaller chaetognaths which can be found in great abundance throughout the world’s oceans. These creatures make up a significant fraction of the ocean’s plankton and thus represent an important component of the food chain.

Credit: .B. Caron/Royal Ontario Museum

Credit: .B. Caron/Royal Ontario Museum

A hallmark of Capinatator is a crown of spikes, as many as 50, which adorned its head and served to push prey through the mouth. That’s nearly double the maximum number of spines in today’s chaetognaths.

This new species was well adapted to capturing prey with the numerous, claw-like spines surrounding its mouth,” said Jean-Bernard Caron, senior curator of invertebrate palaeontology at the Royal Ontario Museum. “Darting from the water depths, the spines would have been a terrifying sight to many of the smallest marine creatures that lived during that time.”

For a glimpse of how Capinatator likely fed, Yale produced the following video.

These ancient chaetognath predators were an important component of some of the earliest marine ecosystems. Because their bodies were squishy, it can be very difficult to find reliable fossils but the team made it happen. Now, more than half a billion after since Capinatator roamed the world’s oceans teeming with primitive life, we are fortunate enough to peer inside the Cambrian explosion. With each new specimen, we move closer to finding out how it all begun.

The world’s first animal was probably a simple sponge

Before life exploded in the Cambrian 542 million years ago, Earth’s inhabitants were generally single-celled simple organisms. But a new study from MIT found that multi-cellular organisms may have evolved before the Cambrian Explosion; according to their research, the first animal was a simple sea sponge over 640 million years old.

Sponges in Antarctica. Photo by Steve Rupp, National Science Foundation.

The new genetic analysis suggests that a sea sponge was the source for an unusual molecule found in rocks that are 640 million years old. These rocks significantly predate the Cambrian explosion, the relatively short event during which most of major animal phyla appeared, indicating that the sponge emerged much before this event.

“We brought together paleontological and genetic evidence to make a pretty strong case that this really is a molecular fossil of sponges,” says David Gold, a postdoc in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “This is some of the oldest evidence for animal life.”

Before things got wild

The fossil record abounds with examples from the Cambrian Explosion. Paleontologists believe they have a fairly good idea about what happened then, even though it was over 500 million years ago. However, fossils from before that time are much rarer, making it difficult to understand how the evolutionary tree developed. Summons’ lab has been looking for the answer in molecular fossils – large amounts of unusual molecules conserved in the fossil record.

“There’s a feeling that animals should be much older than the Cambrian, because a lot of animals are showing up at the same time, but fossil evidence for animals before that has been contentious,” Gold says. “So people are interested in the idea that some of these biomarkers and chemicals, molecules left behind, might help resolve these debates.”

The molecule they focused on is 24-isopropylcholestane, or 24-ipc for short — a modified version of cholesterol. In 1994, Summons was part of a team that found large quantities of 24-ipc in Cambrian and slightly older rocks. They speculated that sponges or their ancestors might be the source, but had no confirmation. In 2009, a team led by University of California at Riverside Professor Gordon Love, then a postdoc in Summons’ lab,  continued the study and confirmed the presence of 24-ipc in 640-million-year-old rock samples, indicating the oldest evidence for animal life. It’s a fine example of a line of research that connects MIT researchers over 20 years.

“This research topic has a 20-plus-year history intimately connected to MIT scientists,” Summons notes. “Now, in 2016 David Gold has been able to apply his skills and the new tools of the genomic era, to add a further layer of evidence supporting the ‘sponge biomarker hypothesis.’”

However, the problem with looking at molecular fossils instead of “proper” fossils is that we don’t know anything about how these animals looked like – because we can’t actually see them. Were they anything like today’s sponges? How and why did they emerge 100 million years before the big Cambrian explosion? Those are still questions to be answered.

“This brings up all these new questions: What did these organisms look like? What was the environment like? And why is there this big gap in the fossil record?” Gold says. “This goes to show how much we still don’t know about early animal life, how many discoveries there are left, and how useful, when done properly, these molecular fossils can be to help fill in those gaps.”


Paleontologists find a ridiculously armored Cambrian worm

It basically looks like a weapon: the fossil of a worm-like animal from the Cambrian period has been presented by scientists, and it’s as armored as it gets.

Credit: An artist’s reconstruction of Eokinorhynchus rarus, a 535-million-year-old fossil from China that is closely related to the ancestor of modern animal phylum Kinorhyncha, which is a member of moulting animals that also include the arthropods and nematods. Eokinorhynchus rarus is only a few millimetre in length. It is the first fossil kinorhynch unearthed from the rock record. Credit: Dinghua Yang at Nanjing Institute of Geology and Palaeontology

Credit: An artist’s reconstruction of Eokinorhynchus rarus, a 535-million-year-old fossil from China that is closely related to the ancestor of modern animal phylum Kinorhyncha, which is a member of moulting animals that also include the arthropods and nematods. Eokinorhynchus rarus is only a few millimetre in length. It is the first fossil kinorhynch unearthed from the rock record.
Credit: Dinghua Yang at Nanjing Institute of Geology and Palaeontology

The Cambrian was definitely one of the strangest geological and biological stages in Earth’s history; it’s not only that it was 500 million years ago, but the Cambrian explosion was firing at all cylinders. The Cambrian explosion was a (relatively) short evolutionary event during which most major animal phyla appeared. Basically, life was trying to fill out all the available ecosystem niches, and many extremely strange creatures emerged. Such is the case with Eokinorhynchis rarus.

Eokinorhynchis rarus has five pairs of large bilaterally placed spines on its trunk and may be related to a group of creatures called kinorhynchs. Kinorhynchs (also called mud dragons for some reason) are a phylum of small (1 mm or less) marine invertebrates that are widespread in mud or sand at all depths (except extreme ones). However, unlike these creatures, our Eokinorhynchis is heavily armored and has larger spines – but it may be an ancestor of the mud dragons.

The body is divided into three sections: a head, a neck and a trunk. These are some of the earliest creatures found with segmented bodies, so they could provide clues on how body segmentation emerged. Shuhai Xiao and colleagues at the describe several fossils, including E. rarus from the early Cambrian period and offer their expertise in Nature.


500 million year old worm had impressive spiky armor

Paleontologists working in China have discovered fossils of an impressively armored worm that lived during the Cambrian, 500 million years ago. Called  Hairy Collins’ Monster, this is one of the first creatures to develop a spiky armor.

Collinsium ciliosum. Image credit: Jie Yang.

Today, the 180 species of velvet worms are pretty similar – they have tiny eyes, antennae, multiple pairs of legs, and slime glands. They live in dark, moist environments and usually use their saliva to immobilize their prey; all in all, you could say that they look like… worms. But their ancestors were much more hardcore than this – they were hairy, thorny, and dangerous.

“Modern velvet worms are all pretty similar in terms of their general body organization and not that exciting in terms of their lifestyle. But during the Cambrian, the distant relatives of velvet worms were stunningly diverse and came in a surprising variety of bizarre shapes and sizes,” said Dr Javier Ortega-Hernández from the University of Cambridge, UK, a co-author of the paper published today in the journal PNAS.


The 8.5-centimeter-long worm had 15 segments and lived on the bottom of the seafloor in shallow waters. The first 6 segments had hair-like structures, while the 9 ones from behind had claws. Because the claws would have not been useful at all on the seafloor, paleontologists believed it clung to rocks or other hard surfaces and simply filtered current water for nutrients.

Image via Sci News.

Given this sedentary lifestyle, Collinsium ciliosum would have been a sitting duck for predators, so it did what any responsible creature in the Cambrian did: it developed a strong defense: its body built the protective claws and spikes.

The species resembles Hallucigenia, another otherworldly creature that lived during the Cambrian. During the Cambrian, there was a biodiversity explosion, with incredibly diverse and strange creatures filling up every environmental niche. However many of them didn’t have any evolutionary success.

“Animals during the Cambrian were incredibly diverse, with lots of interesting behaviors and modes of living,” Dr Ortega-Hernández said. Collinsium ciliosum was one of these evolutionary experiments – one which ultimately failed as they have no living direct ancestors – but it’s amazing to see how specialized many animals were hundreds of millions of years ago.”



Artist illustration of Hallucigenia sparsa based on recent electron scan microscope images. Credit: Danielle Dufault

Hallucigenia: the half-billion years old freaky ancestor of molting animals

When the freakish Hallucigenia was first discovered in the 1970s, paleontologists found it nearly impossible to distinguish head from tail. Now, the bizarre creature – an ancestor to molding animals like crabs, worms or krill – had its features identified with unprecedented precision, but that doesn’t mean it’s less freakish looking: worm-like with a mouth adorned with a ring of teeth, bearing seven pairs of legs ending in claws, and three pairs of tentacles along its neck. To finish it off, its back was covered with enormous spikes. Yes, it looks weird, but so were most animals that lived 500 million years ago during the so-called Cambrian explosion – a period of massive bloom in terms of diversity of life and evolution. Most creatures of those times were somewhat primitive, but remarkably, Hallucigenia was quite advanced for its age.

Artist illustration of Hallucigenia sparsa based on recent electron scan microscope images.  Credit: Danielle Dufault

Artist illustration of Hallucigenia sparsa based on recent electron scan microscope images. Credit: Danielle Dufault

The fossil remains first discovered in Canada’s Burgess Shale are highly difficult to interpret. Basically, if you look at it in 2D it all looks like a worm with legs or spikes – hard to tell which is which. It’s no wonder that scientists initially described the creature totally upside down: the spines on the back were thought to be legs and vice-versa, and the head was mistaken for a tail. Using electron scan microscopy, researchers at University of Cambridge, the Royal Ontario Museum and the University of Toronto imaged the ancient Hallucigenia with unprecedented precision, casting aside ambiguities.

“Prior to our study there was still some uncertainty as to which end of the animal represented the head, and which the tail,” saidDr Martin Smith, a postdoctoral researcher in Cambridge’s Department of Earth Sciences, and the paper’s lead author. “A large balloon-like orb at one end of the specimen was originally thought to be the head, but we can now demonstrate that this actually wasn’t part of the body at all, but a dark stain representing decay fluids or gut contents that oozed out as the animal was flattened during burial.”

After they realized which end is which, Smith was prompted to revisit the fossils and dig up the sediments around the head of the fossilized creature. This revealed some interesting clues related to its last moments alive. Apparently, this particular specimen was buried in a mudslide.

“This let us get the new images of the head,” said Caron. “When we put the fossils in the electron microscope, we were initially hoping that we might find eyes, and were astonished when we also found the teeth smiling back at us!”

Fossiled remains of Hallucigenia. Image: Jean-Bernard Caron

Fossiled remains of Hallucigenia. Image: Jean-Bernard Caron

Adorable and nightmarish-looking at the same time, Hallucigenia measured between 10 and 50 millimetres long and its head bore a simple pair of eyes and a row of needle-like teeth. The right of teeth likely helped the animal generate suction, flexing in and out, like a valve or a plunger, in order to suck its food into its throat, as reported in Nature.

“These teeth resemble those we see in many early moulting animals, suggesting that a tooth-lined throat was present in a common ancestor,” said Caron. “So where previously there was little reason to think that arthropod mouths had much in common with the mouths of animals such as penis worms, Hallucigenia tells us that arthropods and velvet worms did ancestrally have round-the-mouth plates and down-the-throat teeth – they just lost or simplified them later.”

Hallucigenia belongs to a group called ecdysozoans, which includes velvet worms (onychophorans) and water bears (tardigrades). While Hallucigenia isn’t the ancestor to all ecdysozoans, it is definitely high up the evolutionary tree and direct precursor to velvet worms. In fact, the findings helped the researchers assert that velvet worms initially had the same configuration, but lost it in time due to evolutionary mechanisms. Smith and Javier Ortega-Hernandez published a paper last year  that reported five key characteristics that link the species to the velvet worms.

“The early evolutionary history of this huge group is pretty much uncharted,” said Smith. “While we know that the animals in this group are united by the fact that they moult, we haven’t been able to find many physical characteristics that unite them.”

“It turns out that the ancestors of moulting animals were much more anatomically advanced than we ever could have imagined: ring-like, plate-bearing worms with an armoured throat and a mouth surrounded by spines,” said Dr Jean-Bernard Caron, Curator of Invertebrate Palaeontology at the Royal Ontario Museum and Associate Professor in the Departments of Earth Sciences and Ecology & Evolutionary Biology at the University of Toronto. “We previously thought that neither velvet worms nor their ancestors had teeth. But Hallucigenia tells us that actually, velvet worm ancestors had them, and living forms just lost their teeth over time.”

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

Animals built reefs 550 million years ago

These reefs were built by Cloudina ~548 million years ago, from the Nama Group, Namibia. Credit: Fred Bowyer

Corals have been around for hundreds of millions of years, but even before them, 550 million years ago, animals were building reefs. A new study has found that Cloudina, the first animals to have hard shells built reefs too. Cloudina lived towards the end of the Ediacaran period – the last geological period of the Proterozoic Eon, immediately preceding the Cambrian Period. They covered a wide geographical range and fossils are abundant in some areas of the world. During that time, life was already starting to boom, and more and more environmental niches were starting to be covered. Creatures were diversifying, and nature was “experimenting” new things.However, finding good samples of this age is extremely difficult – even when you’re dealing with hard shell marine animals.

The study reveals the fact that Cloudina attached themselves to fixed surfaces — and to each other — by producing natural cement composed of calcium carbonate, to form rigid structures. They were the first creatures to build reefs (non-living reefs). Fossil records indicate that all creatures had a soft body until them – they were the real road openers. These findings support the idea that environmental pressures caused species to develop new features and behaviors in order to survive – developing a hard shell turned out to be a great thing, as even today, 550 million years later, there are a myriad of hard shelled animals. It is believed that this feature initially develoed in order to protect animals from predators, but a reef provided safe access to nutrient-rich waters riddled with currents. Professor Rachel Wood, Professor of Carbonate GeoScience at the University of Edinburgh, who led the study, said:

“Modern reefs are major centres of biodiversity with sophisticated ecosystems. Animals like corals build reefs to defend against predators and competitors. We have found that animals were building reefs even before the evolution of complex animal life, suggesting that there must have been selective pressures in the Precambrian Period that we have yet to understand.”

Following the Ediacaran period came the Cambrian – where life really started to diversify. The rapid diversification of lifeforms in the Cambrian, known as the Cambrian explosion, produced the first representatives of all modern animal phyla.

Journal Reference: A. M. Penny, R. Wood, A. Curtis, F. Bowyer, R. Tostevin, K.- H. Hoffman. Ediacaran metazoan reefs from the Nama Group, Namibia. Science, 2014; 344 (6191): 1504 DOI: 10.1126/science.1253393

Prehistoric shrimps traded claws for nets, filtering food like modern whales

Cambrian fossil is earliest example of large swimming filter-feeder.

An evolutionary explosion

Half a billion years ago, the world was extremely different. We’re in the Cambrian, the first geological period of the Paleozoic Era, which lasted from about 541 to 485 million years ago. Life is diversifying at an incredibly fast rate, into what we call today the “Cambrian explosion“. Basically, nature and evolution started experimenting with a myriad of life forms which were developing to fill in the empty biological niches. Until the Cambrian most organisms were simple, composed of individual cells occasionally organized into colonies, but during the period, they started diversifying at an incredibly fast rate. This is why Cambrian fossils are often remarkable and unique.  Such is the case with Tamisiocaris borealis.

During the Cambrian, giant, fierce shrimp-like predators patrolled the world’s oceans, using sharp claws to snare their prey – it was a dog-eat-dog kind of world. However, Tamisiocaris was more of a gentle giant – using wispy, comb-like frontal appendages roughly 12 centimetres long to sweep up plankton as small as 0.5 millimetres. A new study conducted by University of Bristol researchers documents how it used these specialized appendages to filter out plankton, in a way much like whales to today.

How whales eat

You’d think that something as big as a whale eats something big, right? Well, you couldn’t be further from the truth! Many whales eat small organisms caught by straining seawater through a comblike structure found in the mouth called baleen. This is also the case of the blue whale – the largest creature to have ever existed on Earth. Curious that the largest thing on our planet would eat some of the smallest things on our planet, but that’s just evolution for you.

For Tamisiocaris, this strategy had a very clear and efficient purpose: while the competition for marine resources was extremely fierce, by changing its feeding strategy, it no longer needed to compete with the fiercest animals in the ocean for its food supply, says study co-author Jakob Vinther, a palaeobiologist at the University of Bristol, UK. This way, the animals “aren’t really a threat to anyone, and they don’t feel threatened either”, he says. This basically made it unique in the food chain – it had no natural enemies, and no real competitors for its food.

Not the best, but the first

One of the fossil feeding appendages of Tamisiocaris.
Credit: Dr Jakob Vinther, University of Bristol

This type of evolutionary response has happened several times throughout Earth’s geological history, especially when there was an abundance of nutrients in the marine environment – like clearly there was in the Cambrian. But this is the first recorded case. Dr Vinther said:

“These primitive arthropods were, ecologically speaking, the sharks and whales of the Cambrian era. In both sharks and whales, some species evolved into suspension feeders and became gigantic, slow-moving animals that in turn fed on the smallest animals in the water.”

In order to better understand exactly how it fed, researchers developed

a 3D computer animation of the feeding appendage to explore the range of movements it could have made.

Tamisiocaris would have been a sweep net feeder, collecting particles in the fine mesh formed when it curled its appendage up against its mouth,” said Dr Martin Stein of the University of Copenhagen, who created the computer animation. “This is a rare instance when you can actually say something concrete about the feeding ecology of these types of ancient creatures with some confidence.”

This discovery changed what researchers thought about them by 180 degrees – they believed Tamisiocaris to be nothing more than a failed evolutionary experiment – but the primitive arthropod was a pioneer, much ahead of its time:

“We once thought that anomalocarids were a weird, failed experiment,” said co-author Dr Nicholas Longrich at the University of Bath. “Now we’re finding that they pulled off a major evolutionary explosion, doing everything from acting as top predators to feeding on tiny plankton.”


A book on the Cambrian – with some mind blowing illustrations


Opabinia is an extinct stem-arthropod genus, measuring approximately 4cm head to tail. It had five eyes and a single appendage extending from its head.

Paleontologists have found evidence of animal life dating back at least 635 million years. Those animals acted much like today’s sponges, stuck in the sea floor, filtering water particles for useful nutrients in the sea. But just over 100 million years later, during the Cambrian explosion, life really started to pump its engines. All sorts of creatures were filling all sorts of environmental niches (as some put it, it was mother nature’s experimentation period), and some of the creatures living then are so weird that an attempt at reconstruction seems really bizarre, and more like sci-fi than reality.


Myllokunmingia may be the oldest known vertebrate, with a skull made of cartilage and other hallmarks of vertebrates.

The first book that really documented the Cambrian life explosion was written by Steven Jay Gould in 1989, called A Wonderful Life. I have to be honest and say that even though I’ve read several works on the Cambrian, this particular book has slipped me so far. But I’ve heard so many good things about it, it’s definitely on my to do list. But in the almost quarter century that passed since then, we have learned a lot, greatly expanding our knowledge about that ancient period. Doug Erwin of the Smithsonian Institution and James Valentine of Berkeley have collaborated on a new book, The Cambrian Explosion: The Construction of Animal Biodiversity – in which they sinthesize both old and new data, and feature some fabulous illustrations by Quade Paul.


Diania measured 6 centimetres (2.4 in) long and had a long, thin body. At the front end is a proboscis, presumably used in feeding. These animals have ten pairs of legs, and compared to the body these are quite robust and spiny.

The Cambrian is the first first geological period of the Paleozoic Era. We know very little, both geologically and paleontologically about our planet from the PreCambrian. The Cambrian Period marked a profound change in life on Earth marking the transition from mostly simple, unicellular life, to some remarkably complex life forms. Life thrived in the oceans at that time, continents being most likely barren due to a lack of vegetation. The seas were relatively warm, and polar ice was absent for almost all of the period.


Anomalocaris measured over 1 meter.

The Cambrian explosion had many fuses working together, most likely. A burst of oxygen flooded the seas, as the temperatures were pretty high – the stage was set for the first real predators to show up, and as they showed up, the prey became more and more prepared, with spikes and shields, which made the predators evolve even more. Some animals started to change their environment, piercing the seafloor with tunnels.


Fuxianhuia is a close relative of living arthropods such as insects.

But the diversity of the Cambrian life had yet another source: the DNA of the animals themselves. Animals developed genetic programs for turning a single egg into a complex body, and these programs turned out to be extremely adaptable, with relatively minor changes giving birth to a myriad of life forms.


Odontogriptus had a circular mouth rigged with teeth.


Herpetogaster may be related to living starfish and acorn worms


Banffia… is really weird. It’s still not clear what its closest relatives are.


Hurdia, if you ask me, is the cutest animal on this list.

mao cte

Maotianoascus and Ctenorhabdotus were eerie early relatives of today’s jellyfish



All pictures copyrighted, Quade Paul

Inspired by Carl Zimmer.