̽��ֱ�� of Cambridge - Ediacaran

‘Missing’ sea sponges discovered

sc604 — Wed, 05 Jun 2024 12:56:30 +0000

At first glance, the simple, spikey sea sponge is no creature of mystery.

No brain. No gut. No problem dating them back 700 million years. Yet convincing sponge fossils only go back about 540 million years, leaving a 160-million-year gap in the fossil record.

In a paper released in the journal Nature, an international team including researchers from the ̽��ֱ�� of Cambridge, have reported a 550-million-year-old sea sponge from the “lost years” and proposed that the earliest sea sponges had not yet developed mineral skeletons, offering new parameters to the search for the missing fossils.

̽��ֱ��mystery of the missing sea sponges centred on a paradox.

Molecular clock estimates, which involve measuring the number of genetic mutations that accumulate within the Tree of Life over time, indicate that sponges must have evolved about 700 million years ago. And yet, there had been no convincing sponge fossils found in rocks that old.

For years, this conundrum was the subject of debate among zoologists and palaeontologists.

This latest discovery fills in the evolutionary family tree of one of the earliest animals, connecting the dots all the way back to Darwin’s questions about when the first animals evolved and explaining their apparent absence in older rocks.

Shuhai Xiao from Virginia Tech, who led the research, first laid eyes on the fossil five years ago when a collaborator texted him a picture of a specimen excavated along the Yangtze River in China. “I had never seen anything like it before,” he said. “Almost immediately, I realised that it was something new.”

̽��ֱ��researchers began ruling out possibilities one by one: not a sea squirt, not a sea anemone, not a coral. They wondered, could it be an elusive ancient sea sponge?

In an earlier study published in 2019, Xiao and his team suggested that early sponges left no fossils because they had not evolved the ability to generate the hard needle-like structures, known as spicules, that characterise sea sponges today.

̽��ֱ��team traced sponge evolution through the fossil record. As they went further back in time, sponge spicules were increasingly more organic in composition, and less mineralised.

“If you extrapolate back, then perhaps the first ones were soft-bodied creatures with entirely organic skeletons and no minerals at all,” said Xiao. “If this was true, they wouldn’t survive fossilisation except under very special circumstances where rapid fossilisation outcompeted degradation.”

Later in 2019, Xiao’s group found a sponge fossil preserved in just such a circumstance: a thin bed of marine carbonate rocks known to preserve abundant soft-bodied animals, including some of the earliest mobile animals. Most often this type of fossil would be lost to the fossil record. ̽��ֱ��new finding offers a window into early animals before they developed hard parts.

̽��ֱ��surface of the new sponge fossil is studded with an intricate array of regular boxes, each divided into smaller, identical boxes.

“This specific pattern suggests our fossilised sea sponge is most closely related to a certain species of glass sponges,” said first author Dr Xiaopeng Wang, from Cambridge’s Department of Earth Sciences and the Nanjing Institute of Geology and Palaeontology.

Another unexpected aspect of the new sponge fossil is its size.

“When searching for fossils of early sponges I had expected them to be very small,” said co-author Alex Liu from Cambridge’s Department of Earth Sciences. “ ̽��ֱ��new fossil can reach over 40 centimetres long, and has a relatively complex conical body plan, challenging many of our expectations for the appearance of early sponges”.

While the fossil fills in some of the missing years, it also provides researchers with important guidance about what they should look for, which will hopefully extend understanding of early animal evolution further back in time.

“ ̽��ֱ��discovery indicates that perhaps the first sponges were spongey but not glassy,” said Xiao. “We now know that we need to broaden our view when looking for early sponges.”

Reference:
Xiaopeng Wang et al. ‘A late-Ediacaran crown-group sponge animal.’ Nature (2024). DOI: 10.1038/s41586-024-07520-y

Adapted from a Virginia Tech press release.

̽��ֱ��discovery, published in Nature, opens a new window on early animal evolution.

Xiaopeng Wang

Heliocolocellus fossil

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

Half billion-year-old 'social network' observed in early animals

sc604 — Thu, 05 Mar 2020 09:11:01 +0000

Some of the first animals on Earth were connected by networks of thread-like filaments, the earliest evidence yet found of life being connected in this way.

Why life on Earth first got big

sc604 — Mon, 25 Jun 2018 14:52:12 +0000

̽��ֱ��research, led by the ̽��ֱ�� of Cambridge, found that the most successful organisms living in the oceans more than half a billion years ago were the ones that were able to ‘throw’ their offspring the farthest, thereby colonising their surroundings. ̽��ֱ��results are reported in the journal Nature Ecology and Evolution.

Prior to the Ediacaran period, between 635 and 541 million years ago, life forms were microscopic in size, but during the Ediacaran, large, complex organisms first appeared, some of which – such as a type of organism known as rangeomorphs – grew as tall as two metres. These organisms were some of the first complex organisms on Earth, and although they look like ferns, they may have been some of the first animals to exist – although it’s difficult for scientists to be entirely sure. Ediacaran organisms do not appear to have mouths, organs or means of moving, so they are thought to have absorbed nutrients from the water around them.

As Ediacaran organisms got taller, their body shapes diversified, and some developed stem-like structures to support their height.

In modern environments, such as forests, there is intense competition between organisms for resources such as light, so taller trees and plants have an obvious advantage over their shorter neighbours. “We wanted to know whether there were similar drivers for organisms during the Ediacaran period,” said Dr Emily Mitchell of Cambridge’s Department of Earth Sciences, the paper’s lead author. “Did life on Earth get big as a result of competition?”

Mitchell and her co-author Dr Charlotte Kenchington from Memorial ̽��ֱ�� of Newfoundland in Canada examined fossils from Mistaken Point in south-eastern Newfoundland, one of the richest sites of Ediacaran fossils in the world.

Earlier research hypothesised that increased size was driven by the competition for nutrients at different water depths. However, the current work shows that the Ediacaran oceans were more like an all-you-can-eat buffet.

“ ̽��ֱ��oceans at the time were very rich in nutrients, so there wasn’t much competition for resources, and predators did not yet exist,” said Mitchell, who is a Henslow Research Fellow at Murray Edwards College. “So there must have been another reason why life forms got so big during this period.”

Since Ediacaran organisms were not mobile and were preserved where they lived, it’s possible to analyse whole populations from the fossil record. Using spatial analysis techniques, Mitchell and Kenchington found that there was no correlation between height and competition for food. Different types of organisms did not occupy different parts of the water column to avoid competing for resources – a process known as tiering.

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

According to the researchers, one likely function of stems would be to enable the greater dispersion of offspring, which rangeomorphs produced by expelling small propagules. ̽��ֱ��tallest organisms were surrounded by the largest clusters of offspring, suggesting that the benefit of height was not more food, but a greater chance of colonising an area.

“While taller organisms would have been in faster-flowing water, the lack of tiering within these communities shows that their height didn’t give them any distinct advantages in terms of nutrient uptake,” said Mitchell. “Instead, reproduction appears to have been the main reason that life on Earth got big when it did.”

Despite their success, rangeomorphs and other Ediacaran organisms disappeared at the beginning of the Cambrian period about 540 million years ago, a period of rapid evolutionary development when most major animal groups first appear in the fossil record.

̽��ֱ��research was funded by the Natural Environment Research Council, the Cambridge Philosophical Society, Murray Edwards College and Newnham College, Cambridge.

Reference
Emily G. Mitchell and Charlotte G. Kenchington. ‘ ̽��ֱ��utility of height for the Ediacaran organisms of Mistaken Point.’ Nature Ecology and Evolution (2018). DOI: 10.1038/s41559-018-0591-6

Inset image:
A close-up view of the Mistaken Point ‘E’ surface community. Credit: Emily Mitchell.

Some of the earliest complex organisms on Earth – possibly some of the earliest animals to exist – got big not to compete for food, but to spread their offspring as far as possible.

Reproduction appears to have been the main reason that life on Earth got big when it did.

Emily Mitchell

CG Kenchington

Artist’s reconstruction of the community at Lower Mistaken Point

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

‘Mysterious’ ancient creature was definitely an animal, research confirms

sc604 — Fri, 15 Sep 2017 11:01:21 +0000

A new study by researchers at the universities of Cambridge, Oxford, Bristol, and the British Geological Survey provides strong proof that Dickinsonia was an animal, confirming recent findings suggesting that animals evolved millions of years before the so-called Cambrian Explosion of animal life. ̽��ֱ��study is published in the journal Proceedings of the Royal Society B.

Lead author on the paper is Dr Renee Hoekzema, a PhD candidate at Oxford who carried out this research while completing a previous PhD in Oxford’s Department of Earth Sciences. She said: ‘Dickinsonia belongs to the Ediacaran biota – a collection of mostly soft-bodied organisms that lived in the global oceans between roughly 580 and 540 million years ago. They are mysterious because despite there being around 200 different species, very few of them resemble any living or extinct organism, and therefore what they were, and how they relate to modern organisms, has been a long-standing palaeontological mystery.’

In 1947, Dickinsonia became one of the first described Ediacaran fossils and was initially thought to be an organism similar to a jellyfish. Since then, its strange body plan has been compared to that of a worm, a placozoan, a bilaterian and several non-animals including fungi, lichens and even entirely extinct groups.

Co-author Dr Alex Liu, from Cambridge's Department of Earth Sciences, said: ‘Discriminating between these different hypotheses has been difficult, as there are so few morphological features in Dickinsonia to compare to modern organisms. In this study we took the approach of looking at populations of this organism, including assumed juvenile and adult individuals, to assess how it grew and to try to work out how to classify it from a developmental perspective.’

̽��ֱ��research was carried out on the basis of a widely held assumption that growth and development are ‘conserved’ within lineages – in other words, the way a group of organisms grows today would not have changed significantly from the way its ancestors grew millions of years ago.

Dickinsonia is composed of multiple ‘units’ that run down the length of its body. ̽��ֱ��researchers counted the number of these units in multiple specimens, measured their lengths and plotted these against the relative ‘age’ of the unit, assuming growth from a particular end of the organism. This data produced a plot with a series of curves, each of which tracked how the organism changed in the size and number of units with age, enabling the researchers to produce a computer model to replicate growth in the organism and test previous hypotheses about where and how growth occurred.

Dr Hoekzema said: ‘We were able to confirm that Dickinsonia grows by both adding and inflating discrete units to its body along its central axis. But we also recognised that there is a switch in the rate of unit addition versus inflation at a certain point in its life cycle. All previous studies have assumed that it grew from the end where each “unit” is smallest, and was therefore considered to be youngest. We tested this assumption and interpreted our data with growth assumed from both ends, eventually coming to the conclusion that people have been interpreting Dickinsonia as having grown at the wrong end for the past 70 years.

‘When we combined this growth data with previously obtained information on how Dickinsonia moved, as well as some of its morphological features, we were able to reject all non-animal possibilities for its original biological affinity and show that it was an early animal, belonging to either the Placozoa or the Eumetazoa.

‘This is one of the first times that a member of the Ediacaran biota has been identified as an animal on the basis of positive evidence.’

Dr Liu added: ‘This finding demonstrates that animals were present among the Ediacaran biota and importantly confirms a number of recent findings that suggest animals had evolved several million years before the “Cambrian Explosion” that has been the focus of attention for studies into animal evolution for so long.

‘It also allows Dickinsonia to be considered in debates surrounding the evolution and development of key animal traits such as bilateral symmetry, segmentation and the development of body axes, which will ultimately improve our knowledge of how the earliest animals made the transition from simple forms to the diverse range of body plans we see today.’

Reference:
Renee S. Hoekzema et al. ‘Quantitative study of developmental biology confirms Dickinsonia as a metazoan’. Proceedings of the Royal Society B (2017). DOI: 10.1098/rspb.2017.1348

Adapted from a ̽��ֱ�� of Oxford press release.

It lived well over 550 million years ago, is known only through fossils and has variously been described as looking a bit like a jellyfish, a worm, a fungus and lichen. But was the ‘mysterious’ Dickinsonia an animal, or was it something else?

Recent findings suggest animals had evolved several million years before the 'Cambrian Explosion' that has been the focus of attention for studies into animal evolution for so long.

Alex Liu

̽��ֱ��Ediacaran fossil Dickinsonia costata, specimen P40135 from the collections of the South Australia Museum, Adelaide

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Big, shape-shifting animals from the dawn of time

sc604 — Mon, 10 Jul 2017 14:48:33 +0000

Why did life on Earth change from small to large when it did? Researchers from the ̽��ֱ�� of Cambridge and the Tokyo Institute of Technology have determined how some of the first large organisms, known as rangeomorphs, were able to grow up to two metres in height, by changing their body size and shape as they extracted nutrients from their surrounding environment.

̽��ֱ��results, reported in the journal Nature Ecology and Evolution, could also help explain how life on Earth, which once consisted only of microscopic organisms, changed so that huge organisms like dinosaurs and blue whales could ultimately evolve.

Rangeomorphs were some of the earliest large organisms on Earth, existing during a time when most other forms of life were microscopic in size. Some rangeomorphs were only a few centimetres in height, while others were up to two metres tall.

These organisms were ocean dwellers that lived during the Ediacaran period, between 635 and 541 million years ago. Their soft bodies were made up of branches, each with many smaller side branches, forming a geometric shape known as a fractal, which can be seen today in things like lungs, ferns and snowflakes.

Since rangeomorphs don’t resemble any modern organism, it’s difficult to understand how they fed, grew or reproduced, let alone how they might link with any modern group. However, although they look somewhat like plants, scientists believe that they may have been some of the earliest animals to live on Earth.

“What we wanted to know is why these large organisms appeared at this particular point in Earth’s history,” said Dr Jennifer Hoyal Cuthill of Cambridge’s Department of Earth Sciences and Tokyo Tech’s Earth-Life Science Institute, the paper’s first author. “They show up in the fossil record with a bang, at very large size. We wondered, was this simply a coincidence or a direct result of changes in ocean chemistry?”

̽��ֱ��researchers used micro-CT scanning, photographic measurements and mathematical and computer models to examine rangeomorph fossils from south-eastern Newfoundland, Canada, the UK and Australia.

Their analysis shows the earliest evidence for nutrient-dependent growth in the fossil record. All organisms need nutrients to survive and grow, but nutrients can also dictate body size and shape. This is known as ‘ecophenotypic plasticity.’ Hoyal Cuthill and her co-author Professor Simon Conway Morris suggest that rangeomorphs not only show a strong degree of ecophenotypic plasticity, but that this provided a crucial advantage in a dramatically changing world. For example, rangeomorphs could rapidly “shape-shift”, growing into a long, tapered shape if the seawater above them happened to have elevated levels of oxygen.

“During the Ediacaran, there seem to have been major changes in the Earth’s oceans, which may have triggered growth, so that life on Earth suddenly starts getting much bigger,” said Hoyal Cuthill. “It’s probably too early to conclude exactly which geochemical changes in the Ediacaran oceans were responsible for the shift to large body sizes, but there are strong contenders, especially increased oxygen, which animals need for respiration.”

This change in ocean chemistry followed a large-scale ice age known as the Gaskiers glaciation. When nutrient levels in the ocean were low, they appear to have kept body sizes small. But with a geologically sudden increase in oxygen or other nutrients, much larger body sizes become possible, even in organisms with the same genetic makeup. This means that the sudden appearance of rangeomorphs at large size could have been a direct result of major changes in climate and ocean chemistry.

However, while rangeomorphs were highly suited to their Ediacaran environment, conditions in the oceans continued to change and from about 541 million years ago the ‘Cambrian Explosion’ began – a period of rapid evolutionary development when most major animal groups first appeared in the fossil record. When the conditions changed, the rangeomorphs were doomed and nothing quite like them has been seen since.

Reference
Jennifer F. Hoyal Cuthill and Simon Conway Morris. ‘Nutrient-dependent growth underpinned the Ediacaran transition to large body size.’ Nature Ecology and Evolution (2017). DOI: 10.1038/s41559-017-0222-7.

Major changes in the chemical composition of the world’s oceans enabled the first large organisms – possibly some of the earliest animals – to exist and thrive more than half a billion years ago, marking the point when conditions on Earth changed and animals began to take over the world.

We wanted to know why these large organisms appeared at this particular point in Earth’s history.

Jennifer Hoyal Cuthill

Artist's impression of rangeomorphs

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Earliest evidence of reproduction in a complex organism

sc604 — Mon, 03 Aug 2015 15:00:00 +0000

Researchers led by the ̽��ֱ�� of Cambridge have found the earliest example of reproduction in a complex organism. Their new study has found that some organisms known as rangeomorphs, which lived 565 million years ago, reproduced by taking a joint approach: they first sent out an ‘advance party’ to settle in a new area, followed by rapid colonisation of the new neighbourhood. ̽��ֱ��results, reported today in the journal Nature, could aid in revealing the origins of our modern marine environment.

Using statistical techniques to assess the distribution of populations of a type of rangeomorph called Fractofusus, the researchers observed that larger ‘grandparent’ rangeomorphs were randomly distributed in their environment, and were surrounded by distinct patterns of smaller ‘parents’ and ‘children’. These patterns strongly resemble the biological clustering observed in modern plants, and suggest a dual mode of reproduction: the ‘grandparents’ being the product of ejected waterborne propagules, while the ‘parents’ and ‘children’ grew from ‘runners’ sent out by the older generation, like strawberry plants.

Rangeomorphs were some of the earliest complex organisms on Earth, and have been considered to be some of the first animals – although it’s difficult for scientists to be entirely sure. They thrived in the oceans during the late Ediacaran period, between 580 and 541 million years ago, and could reach up to two metres in length, although most were around ten centimetres. Looking like trees or ferns, they did not appear to have mouths, organs, or means of moving, and probably absorbed nutrients from the water around them.

Like many of the life forms during the Ediacaran, rangeomorphs mysteriously disappeared at the start of the Cambrian period, which began about 540 million years ago, so it has been difficult to link rangeomorphs to any modern organisms, or to figure out how they lived, what they ate and how they reproduced.

“Rangeomorphs don’t look like anything else in the fossil record, which is why they’re such a mystery,” said Dr Emily Mitchell, a postdoctoral researcher in Cambridge’s Department of Earth Sciences, and the paper’s lead author. “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 used high-resolution GPS, spatial statistics and modelling to examine fossils of Fractofusus, in order to determine how they reproduced. ̽��ֱ��fossils are from south-eastern Newfoundland in Canada, which is one of the world’s richest sources of fossils from the Ediacaran period. Since rangeomorphs were immobile, it is possible to find entire ecosystems preserved exactly where they lived, making them extremely suitable for study via spatial techniques.

̽��ֱ��‘generational’ clustering patterns the researchers observed fit closely to a model known as a nested double Thomas cluster model, of the type seen in modern plants. These patterns suggest rapid, asexual reproduction through the use of stolons or runners. At the same time, the random distribution of larger ‘grandparent’ Fractofusus specimens suggests that they were the result of waterborne propagules, which could have been either sexual or asexual in nature.

“Reproduction in this way made rangeomorphs highly successful, since they could both colonise new areas and rapidly spread once they got there,” said Mitchell. “ ̽��ֱ��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.”

̽��ֱ��use of this type of spatial analysis to reconstruct Ediacaran organism biology is only in its infancy, and the researchers intend to extend their approach to further understand how these strange organisms interacted with each other and their environment.

̽��ֱ��research was funded by the Natural Environment Research Council.

Reference:
Mitchell, E. et al., Reconstructing the reproductive mode of an Ediacaran macro-organism, Nature (2015), DOI: 10.1038/nature14646

Inset image: A group of Fractofusus specimens from the ‘E’ surface, Mistaken Point Ecological Reserve, Newfoundland, Canada Credit: AG Liu

A new study of 565 million-year-old fossils has identified how some of the first complex organisms on Earth – possibly some of the first animals to exist – reproduced, revealing the origins of our modern marine environment.

Rangeomorphs don’t look like anything else in the fossil record, which is why they’re such a mystery

Emily Mitchell

C. G. Kenchington

Artist's reconstruction of the Fractofusus community on the H14 surface at Bonavista Peninsula

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Animals first flex their muscles

sc604 — Wed, 27 Aug 2014 07:15:00 +0000

An unusual new fossil discovery of one of the earliest animals on earth may also provide the oldest evidence of muscle tissue – the bundles of cells that make movement in animals possible.

̽��ֱ��fossil, dating from 560 million years ago, was discovered in Newfoundland, Canada. On the basis of its four-fold symmetry, morphological characteristics, and what appear to be some of the earliest impressions of muscular tissue, researchers from the ̽��ֱ�� of Cambridge, in collaboration with the ̽��ֱ�� of Oxford and the Memorial ̽��ֱ�� of Newfoundland, have interpreted it as a cnidarian: the group which contains modern animals such as corals, sea anemones and jellyfish. ̽��ֱ��results are published today (27 August) in the journal Proceedings of the Royal Society B.

Historically, the origin, evolution and spread of animals has been viewed as having begun during the Cambrian Explosion, a period of rapid evolutionary development starting 541 million years ago when most major animal groups first appear in the fossil record.

“However, in recent decades, discoveries of preserved trackways and chemical evidence in older rocks, as well as molecular comparisons, have indirectly suggested that animals may have a much earlier origin than previously thought,” said Dr Alex Liu of Cambridge’s Department of Earth Sciences, lead author of the paper.

“ ̽��ֱ��problem is that although animals are now widely expected to have been present before the Cambrian Explosion, very few of the fossils found in older rocks possess features that can be used to convincingly identify them as animals,” said Liu. “Instead, we study aspects of their ecology, feeding or reproduction, in order to understand what they might have been.”

̽��ֱ��new fossil, named Haootia quadriformis, dates from the Ediacaran Period, an interval spanning 635 to 541 million years ago. It differs from any previously described Ediacaran fossil, as it comprises of bundles of fibres in a broadly four-fold symmetrical arrangement: a body plan that is similar to that seen in modern cnidarians.

̽��ֱ��researchers determined that the similarities between Haootia quadriformis and both living and fossil cnidarians suggest that the organism was probably a cnidarian, and that the bundles represent muscular tissue. This would make it not only a rare example of an Ediacaran animal, but also one of the oldest fossils to show evidence of muscle anywhere in the world.

“ ̽��ֱ��evolution of muscular animals, in possession of muscle tissues that enabled them to precisely control their movements, paved the way for the exploration of a vast range of feeding strategies, environments, and ecological niches, allowing animals to become the dominant force in global ecosystems,” said Liu.

̽��ֱ��research was funded by the Natural Environment Research Council, the Natural Sciences and Engineering Research Council of Canada, the Burdett Coutts Fund of the ̽��ֱ�� of Oxford, and the National Geographic Global Exploration Fund Northern Europe.

Inset image: Artist reconstruction of Haootia quadriformis. Credit: Martin Brasier

A new fossil discovery identifies the earliest evidence for animals with muscles.

Animals may have a much earlier origin than previously thought

Alex Liu

Alex Liu/Jack Matthews

Fossil of Haootia quadriformis

̽��ֱ��text in this work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page. For image rights, please see the credits associated with each individual image.

Yes

How some of the first animals lived - and died

sc604 — Mon, 11 Aug 2014 19:00:00 +0000

A bizarre group of uniquely-shaped organisms known as rangeomorphs may have been some of the earliest animals to appear on Earth, uniquely suited to ocean conditions 575 million years ago.

A new model devised by researchers at the ̽��ֱ�� of Cambridge has resolved many of the mysteries around the structure, evolution and extinction of these ‘proto animals’. ̽��ֱ��findings are reported today (11 August) in the journal Proceedings of the National Academy of Sciences of the United States of America.

Rangeomorphs were some of the earliest large organisms on Earth, existing during a time when most other forms of life were microscopic in size. Most rangeomorphs were about 10 centimetres high, although some were up to two metres in height.

These creatures were ocean dwellers which lived during the Ediacaran period, between 635 and 541 million years ago. Their bodies were made up of soft branches, each with many smaller side branches, forming a geometric shape known as a fractal, which can be seen in many familiar branching shapes such as fern leaves and even river networks.

Rangeomorphs were unlike any modern organism, which has made it difficult to determine how they fed, grew or reproduced, and therefore difficult to link them to any particular modern group. However, despite the fact that they looked like plants, evidence points to the fact that rangeomorphs were actually some of the earliest animals.

“We know that rangeomorphs lived too deep in the ocean for them to get their energy through photosynthesis as plants do,” said Dr Jennifer Hoyal Cuthill of Cambridge’s Department of Earth Sciences, who led the research. “It’s more likely that they absorbed nutrients directly from the sea water through the surface of their body. It would be difficult in the modern world for such large animals to survive only on dissolved nutrients.”

“ ̽��ֱ��oceans during the Ediacaran period were more like a weak soup – full of nutrients such as organic carbon, whereas today suspended food particles are swiftly harvested by a myriad of animals,” said co-author Professor Simon Conway Morris.

Starting 541 million years ago, the conditions in the oceans changed quickly with the start of the Cambrian Explosion – a period of rapid evolution when most major animal groups first emerge in the fossil record and competition for nutrients increased dramatically.

Rangeomorphs have often been considered a ‘failed experiment’ of evolution as they died out so quickly once the Cambrian Explosion began in earnest, but this new analysis shows just how successful they once were.

Rangeomorphs almost completely filled the space surrounding them, with a massive total surface area. This made them very efficient feeders that were able to extract the maximum amount of nutrients from the ocean water.

“These creatures were remarkably well-adapted to their environment, as the oceans at the time were high in nutrients and low in competition,” said Dr Hoyal Cuthill. “Mathematically speaking, they filled their space in a nearly perfect way.”

Dr Hoyal Cuthill examined rangeomorph fossils from a number of locations worldwide, and used them to make the first computer reconstructions of the development and three-dimensional structure of these organisms, showing just how well-suited they were to their Ediacaran environment.

As the Cambrian Explosion began however, the rangeomorphs became ‘sitting ducks’, as they had no known means of defence from predators which were starting to evolve, and the changing chemical composition of the ocean meant that they could no longer get the nutrients they required to feed.

“As the Cambrian began, these Ediacaran specialists could no longer survive, and nothing quite like them has been seen again,” said Dr Hoyal Cuthill.

New three-dimensional reconstructions show how some of the earliest animals on Earth developed, and provide some answers as to why they went extinct.

As the Cambrian began, these specialists could no longer survive, and nothing quite like them has been seen again

Jennifer Hoyal Cuthill

Palaeontological reconstruction of rangeomorph fronds from the Ediacaran Period (635-541 million years ago) built using computer models of rangeomorph growth and development.

Yes