Tag Archives: cambrian

‘Penis worms’ invented the hermit lifestyle some 500 million years ago by moving into discarded shells

The “hermit” lifestyle best known from crabs today was first invented 500 million years ago by worms, new research reveals.

Illustration of a Cambrian penis worm inhabiting a hyolith shell. Image credits Zhang Xiguang.

Hermit crabs today are famous for seeking out and taking residence in discarded snail shells. This offers the animals protection against predators while allowing them to avoid the huge energy and nutrient costs associated with building such a shell from scratch. It’s quite an effective strategy for the crabs.

However, they’re not the ones to first think of it. Researchers at Durham University and Yunnan University report that penis worms (phylum Priapulida) were busy taking up residence in discarded shells during the Cambrian period some 500 million years ago. This is the oldest known evidence of the ‘hermit’ lifestyle that we’ve found so far, the team adds.

Renting a place

“Priapulan-like worms were very common in the Cambrian, sometimes forming shallow burrows but often moving along the surface of the sea bed,” said Dr. Martin R. Smith, an Associate Professor in Palaeontology at Durham University and a co-author of the paper, in an email for ZME Science. “Some had little defensive plates or built their own tubes for protection from predators; others even had little claw-like hooks on their underside to help them move about.”

“Today, priapulans are only found in hard-to-inhabit places, such as those with low oxygen, or miniaturized between sand grains — places where predators find it hard to make a living. We used to think that predators struggled a bit in the Cambrian too, but clearly — at least in the Guanshan [area, where these worm fossils vere recovered] — predators were enough of a threat to make priapulans reach for a more ‘modern’ style of defensive mechanism!”

Fossil deposits in the Guanshan, an urbanized area in southeastern Taiwan. The fossil deposits in this area are famous for often preserving soft tissue alongside harder material such as shells, which is quite rare for fossils. Four specimens of penis worms in the genus Eximipriapulus from this area were recovered inside the conical shells of hyoliths, another group of long-extinct animals.

“The worms are always sitting snugly within these same types of shells, in the same position and orientation. My first thought was ‘can I be sure that this isn’t a coincidence’, so we had to look hard at the fossils to be sure that the worms were in (rather than on or below) the shells, that the relationship was consistent, etc.,” explains Dr. Smith for ZME Science.

The findings cast new light on our understanding of the ecosystem relationships during the Cambrian. This was a geological period that was a hotbed of evolution, with many and exotic forms of life appearing all over the planet. The rapid evolutionary changes during this time have earned it the nickname of the “Cambrian explosion”. And some very peculiar lifeforms appeared during this time; in many ways, life on Earth during the Cambrian was quite alien-looking.

It was definitely a valuable time in history. The trial-and-error that happened during this time led to the emergence of what we’d call ‘the modern’ animal body.

But more to the point, the high rates of diversification during the Cambrian led to the emergence of predators in many environments where they were completely lacking before. This, in turn, led to an arms race between predator and prey that still continues to this day.

“The only explanation that made sense was that these shells were their homes – something that came as a real surprise,” Dr Smith adds in a press release. “Not long before these organisms existed, there was nothing alive more complex than seaweeds or jellyfish: so it’s mind-boggling that we start to see the complex and dangerous ecologies usually associated with much younger geological periods so soon after the first complex animals arrive on the scene.”

Hermit crabs today take permanent residence in the shells they find laying on the sea bottom, carrying them around on their backs. The team believes penis worms also carried hyolith shells around, that they “likely dragged the shells with them”, Dr. Smith told me.

“We believe that they dwelt in them permanently (except to up-size when they grew). It’d be lovely to see trace fossils showing the grooves made by dragging the shells, but as the fossils were transported to their resting place, we don’t have definitive evidence,” he told ZME Science.

Hermit crabs today eventually outgrow their shells. Groups of hermit crabs looking for an upgrade will often get together and line up from smallest to largest, then trade shells among themselves. It’s a pretty handy way to make sure that everybody has at least a shell, and that most crabs have a proper shell to live in (some, sadly, are left with shells that are a bit too tiny or defective in some way). I asked Dr. Smith whether there’s any sign that the worms engaged in similar social behavior to find shells to inhabit.

“No evidence, and there seems to have been no shortage of shells in this environment, so it probably didn’t happen in Guanshan – but we don’t have evidence to say either way,” he explaned for ZME Science. “I’d be surprised if they did, as this ‘feels’ like a sophisticated behaviour for this group, and for the Cambrian period  – but then I would have said that about hermiting at all before I saw these fossils!”

Despite their hermiting lifestyle, penis worms were not helpless beasts in their ecosystems. Dr. Smith tells me that shells from brachiopods (lamp shells), trilobites, and hyoliths have been found in the guts of penis worms related to the ones the team investigated here.

“Worth mentioning that ecologically, priapulans were both predators and prey; many fed on organic material within mud, but others scavenged and some may have been active predators themselves,” he told ZME Science.

The findings are valuable as they represent the earliest known case of an animal engaging in a hermit lifestyle. It gives us context to better understand the ecosystem dynamics of the Cambrian period, and of the emergence of wide-scale predation on Earth.

The paper “A ‘hermit’ shell-dwelling lifestyle in a Cambrian priapulan worm” has been published in the journal Current Biology.

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.

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.

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.

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

Complete specimen of Chengjiangocaris kunmingensis from the early Cambrian Xiaoshiba biota of South China. Bottom: Magnification of ventral nerve cord of Chengjiangocaris kunmingensis. Credit: Top: Jie Yang, Bottom: Yu Liu

Half billion-year-old nervous system is most detailed fossil of its kind ever

Unearthed in southern China, this ancient fossil bears the most detailed and well preserved nervous system ever found. The preservation was so pristine that scientists were able to trace and count individual nerves, which help them describe an unique structure that is otherwise unknown in living organisms. Remarkably, the fossil is 520 million years old.

Complete specimen of Chengjiangocaris kunmingensis from the early Cambrian Xiaoshiba biota of South China. Bottom: Magnification of ventral nerve cord of Chengjiangocaris kunmingensis.  Credit: Top: Jie Yang, Bottom: Yu Liu

Complete specimen of Chengjiangocaris kunmingensis from the early Cambrian Xiaoshiba biota of South China. Bottom: Magnification of ventral nerve cord of Chengjiangocaris kunmingensis.
Credit: Top: Jie Yang, Bottom: Yu Liu

Chengjiangocaris kunmingensis belongs to a group called fuxianhuiids, which are the forerunners of anthropods — a diverse modern group that includes insects, spiders and crustaceans. The crustacean-like C. kunmingensis sported a broad, almost heart-shaped head shield, and a long body with pairs of legs of varying sizes. It lived in a period called the Cambrian explosion — a brief evolutionary event during which most major animal phyla appeared. Before life exploded in the Cambrian 542 million years ago, Earth’s inhabitants were generally single-celled simple organisms. This was also a time of intense experimentation on nature’s part, and some of the weirdest creatures ever appeared during this time.

Generally, most fossils are bones or hard bodies and tissue is rarely found. Though rare, excavations sometimes reveal partially-fossilised nervous systems. Most such findings, however, are fossilized brains and even then scientists can only trace the profile with very limited information available about the nervous system’s structure.

C. kunmingensis did not have a brain. Instead, the animal had a nerve cord (similar to a spinal chord in vertebrates) running throughout its body which consists of a chain-like series of interconnected masses of nervous tissue called ganglia. Each gaglia controlled a single pair of walking legs.

Using fluorescence microscopy, researchers at University of Cambridge found the gaglia were made of  dozens of spindly fibres, each measuring about five thousandths of a millimetre in length. These became fossilized as carbon films.

The nervous system seems very similar to that of the priapulids (penis worms) and onychophorans (velvet worms), with regularly-spaced nerves coming out from the ventral nerve cord. The spindly fibres seem to have been lost independently in the tardigrades (water bears) and modern arthropods.

“This is a unique glimpse into what the ancestral nervous system looked like,” said study co-author Dr Javier Ortega-Hernández, of the University of Cambridge’s Department of Zoology. “It’s the most complete example of a central nervous system from the Cambrian period.”

“The more of these fossils we find, the more we will be able to understand how the nervous system – and how early animals – evolved,” said Ortega-Hernández.

Jie Yang et. al. ‘The fuxianhuiid ventral nerve cord and early nervous system evolution in Panarthropoda.’ PNAS (2016). DOI: 10.1073/pnas.1522434113

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.

 

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.

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.”

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.”

 

The first animal to curl into a ball

This defensive strategy has been used for a very long time, but if you were to take a guess, how long would do you think that time was? A thousand years, ten thousand years, one million years? According to a new fossil unearthed by paleontologists, the answer is at least 510 million years!

Trilobites and balls

Specimen of the trilobite Mummaspis muralensis

Trilobites are a well known fossil group which inhabited the planet up until approximately 250 million years ago; no larger than a finger tip, this fossil is the earliest creature known to curl up in a ball, thus pioneering one of the most successful defensive strategies on the planet.

The animal, which is one of the oldest trilobites ever discovered, was found with tail tucked to head in a lump of rock, after it was buried by a sudden mudslide more than half a billion years ago; judging by the fossil, the trilobite hasn’t really perfected this technique, as it left small spaces between the spines in the tail that left parts of the head exposed to danger – but it did a remarkably good job judging by the flexibility of its body. Javier Ortega-Hernández, a paleobiologist at Cambridge University discovered the first fossil, and it didn’t take him a lot to discover the second one.

The Cambrian environment

The Cambrian is the first geological period of the Paleozoic Era, and it marked one of the most profound changes on Earth; previously, organisms were simple, and often unicellular. During the Cambrian, life simply exploded: multicellular life became common, environmental niches were filled, and the fight between predators and prey became much more fierce.

510 million years ago, emerging trilobites were faced with predators and other environmental dangers, and they started to experiment with various defensive techniques. To curl up in a ball proved highly successful, and it evolved to be used even in recent time,s by the ancestors of woodlice, armadillos, hedgehogs and pangolins.

“If you can roll up and protect your vulnerable legs its obviously going to be an evolutionary advantage and the trilobites were the first group of animals to solve this problem,” said Richard Fortey, the British paleontologist at the Natural History Museum in London. “It’s pretty obvious from this paper it was a trick they learned very quickly. They were already doing it by the early Cambrian. Running away is good, but standing your ground and protecting yourself is equally good. It’s been imitated in the animal kingdom many times,” he said.

Actor Johnny Depp gets 505 million years old fossil named after him

Usually, species are named after defining trait, or sometimes, more rarely, after somebody famous in the field, but every once in a while, they get some rather cooky names – like is the case with Kooteninchela deppi.

Cambrian and scrissors

fossil johnny depp

Pronounced Koo-ten-ee-che-la depp-eye, the 505-million-year-old fossil is a distant relative of lobsters and scorpions, and it got this name due to its debatable resemblance of Edward Scissorhands, a character famously played by Johnny Depp.

“When I first saw the pair of isolated claws in the fossil records of this species I could not help but think of Edward Scissorhands. Even the genus name, Kootenichela, includes the reference to this film as ‘chela’ is Latin for claws or scissors. In truth, I am also a bit of a Depp fan and so what better way to honour the man than to immortalise him as an ancient creature that once roamed the sea?”

But it’s not just fun and games. Kooteninchela deppi is helping researchers fill in the puzzle of the Cambrian life puzzle, when life absolutely exploded and most modern species started emerging. The Cambrian is the first geological period of the Paleozoic Era, lasting from 541.0 ± 1.0 to 485.4 ± 1.9 million years ago. The vast majority of animals in the Cambrian period were aquatic, with trilobites as the dominant life form. The biosphere changes that occurred in this period were immense, and towards the end of this period, burrowing animals had destroyed the mats through bioturbation, and gradually turned the seabeds into what they are today; however, as a consequence, very many species depending on these mats went extinct.

So where does Kooteninchela fit in?

fossil johnny depp 2

Our scissory species was approximately 4 cm long, and it lived in very shallow seas, similar to modern coastal environments. However, the sea temperature back then was much hotter than it is today, and even though coral reefs weren’t established yet, it lived in a similar environment consisting of sponges.

It was either a hunter or a scavenger, using its elongated spines to capture prey or search for prey hiding in the sediment, scuttling on the seafloor with its millipede-like legs and going for the occasional swim. It also had large eyes composed of many lenses like the compound eyes of a fly. David Legg adds:

“Just imagine it: the prawns covered in mayonnaise in your sandwich, the spider climbing up your wall and even the fly that has been banging into your window and annoyingly flying into your face are all descendants of Kooteninchela deppi. Current estimates indicate that there are more than one million known insects and potentially 10 million more yet to be categorised, which potentially means that Kooteninchela Deppi has a huge family tree.”

Stunning 500 million year fossil unearthed [GeoPicture of the week]

Just one of the many reasons why I love geology – paleontologists have unearthed extraordinarily preserved fossils of a 520-million-year-old sea creature, one of the oldest animal fossils ever found.

fossil

The animal in case is an arthropod called a fuxhianhuiid – you may remember him from this post, in which I described a lovely book on the Cambrian or from this one – where researchers believed him to be a missing link in insect evolution. The primitive creature had limbs under its head, and those limbs are very interesting for researchers.

“Since biologists rely heavily on organization of head appendages to classify arthropod groups, such as insects and spiders, our study provides a crucial reference point for reconstructing the evolutionary history and relationships of the most diverse and abundant animals on Earth,” said study co-author Javier Ortega-Hernández, an earth scientist at the University of Cambridge, in a statement. “This is as early as we can currently see into arthropod limb development.”

The findings were published in Nature.

The fuxhianhuiid lived in the lower Cambrian, and measured about 3 cm. They probably spent most of their day crawling on the sea bed and maybe swimming short distances. While other specimens have been found (most notably in China), previous fossils were found head-down, this being the first example in which the internal organs aren’t obscured. This is not only a spectacularly preserved fossil, but paleontologists hope it will provide new insight into how animals evolved.

A book on the Cambrian – with some mind blowing illustrations

opabinia

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-small

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

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

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

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.

odontogripus

Odontogriptus had a circular mouth rigged with teeth.

herpetogaster

Herpetogaster may be related to living starfish and acorn worms

banffia

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

hurdia

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

pikaia

Pikaia

All pictures copyrighted, Quade Paul

Inspired by Carl Zimmer.

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.

Fossilized burrows thought to be left by Paleodictyon nodosum [souce: scitechdaily.com]

A primitive form of parenting possibly found in 540 million years old paleodictyon patterns

Paleodictyon is a mysterious fossil pattern found mainly in marine sediments thought to be specific of a certain paleo-depth range; it is a relatively widespread trace fossil – called this way because it is mainly accepted that it is created by a burrowing creature. Although it has been discovered since the dawn of geology and fossil hunting, no one was able to find sediments where you can also see the “architect” of such a symmetric creation – given that underwater honeybees are excluded.

Among his many other passions, Leonardo da Vinci collected and described fossils, including it seems, what later came to be known as Paleodictyon [from BIBLIOTECA LEONARDIANA, via Nature]

Among his many other passions, Leonardo da Vinci collected and described fossils, including it seems, what later came to be known as Paleodictyon [from BIBLIOTECA LEONARDIANA, via Nature]

A new study finds a special type of paleodictyon fossils in the limestone of Nevada and Mexico – one where clues to the elusive pattern may appear to be present. At least that is what the lead author proposes, Mark McMenamin, a paleontologist at Mount Holyoke College in South Hadley, Massachusetts.

Besides the fact that this new fossil may hint towards an explanation of a centuries’ old mystery, what is also interesting is the fossil’s age: about 540 million years – placing it in the early Cambrian – a period when modern multicellular life seemed to have emerged and diversified in a relatively brief period of geological time.

When examining the fossil, McMenamin noticed that some of the burrow swarms seemed to cut through organic pellets 250 to 500 micrometers in diameter — making the pellets too large to have been created by the creature that made the burrows.

“I noticed that the smaller micro-burrows tended to cluster in the center of the swarms,”says McMenamin.

Fossilized burrows thought to be left by Paleodictyon nodosum [souce: scitechdaily.com]

Fossilized burrows thought to be left by Paleodictyon nodosum [souce: scitechdaily.com]

The paleontologist hypothesizes that some sort of adult animal laid down the organic pellets to form a nest around its eggs – and if these eggs were mostly made of soft material, which is the case for many animals – they failed to fossilize.  “The hatchlings then fed on organic matter in the pellets that had been broken down by bacteria,”he says. As they “ate their nest”, the hatchlings would have left that hexagonal burrowing pattern that we see fossilized today.

Although it all seems amazing, it is hard to irrevocably link such parenting behavior to this type of fossil. Gabriela Mangano, who studies Cambrian burrows at the University of Saskatchewan in Saskatoon, Canada says the idea certainly is spectacular, but for it to be true, it needs to rely on a more detailed morphological analysis.

Duncan McIlroy, a burrow specialist at the Memorial University of Newfoundland in St John’s says that in order to bring further evidence, one idea would be to create a 3D model of the rock containing the fossil, perhaps by making a section passing through its regions of interest: “I would look for a discrete structure as part of a large semi-permanent burrow system created by the adult,” he says.

Could Paleodictyon also be nests? “Sure they could be,” says McIlroy. “But it would be very difficult indeed to prove without finding one with associated eggs and juveniles.”
A few cases in which paleodictyon would not be related to this type of parenting would be, for example that the creatures making burrows would actually be preying on the hypothesized eggs. Or perhaps the small creatures would have nothing to do with the whole idea of nests and eggs, and it just came and drew it’s mysterious pattern in the sediment, years after such organic pellets existed. After all, what are a few years or even a decade when compared to the vast eons of geologic time ?
[Via Nature]

A Paleodictyon fossil from Austria [source: wiki]

A Paleodictyon fossil from Austria [source: wiki]

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

 

Fossil of Cambrian sea predator discovered – with video

Anomalocaridids were extremely weird animals, by today’s standards; but by the standards of the Cambrian, they were the hot guys. They had a long spiny head, powerful limbs which were probably used to snag prey and a series of blade-like filaments in segments across the animal’s back, which could have functioned as gills.

During the Cambrian period, there was a major “explosion” of life, facilitating the appearance of numerous species, some of which are nothing short of amazing. Anomalocaridids were the biggest among them, some 500-540 million years ago; but don’t think about dinosaurs – fossils suggest they were 2, maybe 3 feet long. Until now, paleontologists believed that these animals died out at the end of the Cambrian, during the great extinction.

Now, a team led by former Yale researcher Peter Van Roy (now at Ghent University in Belgium) and Derek Briggs, director of the Yale Peabody Museum of Natural History, has discovered a giant fossilized anomalocaridid that measures one meter (more than three feet) in length. In addition, the creature dates back to the Ordovician period – the geological period that followed the Cambrian.

“The anomalocaridids are one of the most iconic groups of Cambrian animals,” Briggs said. “These giant invertebrate predators and scavengers have come to symbolize the unfamiliar morphologies displayed by organisms that branched off early from lineages leading to modern marine animals, and then went extinct. Now we know that they died out much more recently than we thought.”

Of course, the result is not only that the species itself lived, but that it also influenced numerous other specimens from a variety of ecosystems.

“The new discoveries in Morocco indicate that animals characteristic of the Cambrian, such as the anomalocaridids, continued to have a considerable impact on the biodiversity and ecology of marine communities many millions of years later,” Van Roy said.