̽��ֱ�� of Cambridge - Alex Liu

‘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

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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.

‘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

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Fossilised dinosaur brain tissue identified for the first time

sc604 — Thu, 27 Oct 2016 16:13:33 +0000

An unassuming brown pebble, found more than a decade ago by a fossil hunter in Sussex, has been confirmed as the first example of fossilised brain tissue from a dinosaur.

̽��ֱ��fossil, most likely from a species closely related to Iguanodon, displays distinct similarities to the brains of modern-day crocodiles and birds. Meninges – the tough tissues surrounding the actual brain – as well as tiny capillaries and portions of adjacent cortical tissues have been preserved as mineralised ‘ghosts’.

̽��ֱ��results are reported in a Special Publication of the Geological Society of London, published in tribute to Professor Martin Brasier of the ̽��ֱ�� of Oxford, who died in 2014. Brasier and Dr David Norman from the ̽��ֱ�� of Cambridge co-ordinated the research into this particular fossil during the years prior to Brasier’s untimely death in a road traffic accident.

̽��ֱ��fossilised brain, found by fossil hunter Jamie Hiscocks near Bexhill in Sussex in 2004, is most likely from a species similar to Iguanodon: a large herbivorous dinosaur that lived during the Early Cretaceous Period, about 133 million years ago.

Finding fossilised soft tissue, especially brain tissue, is very rare, which makes understanding the evolutionary history of such tissue difficult. “ ̽��ֱ��chances of preserving brain tissue are incredibly small, so the discovery of this specimen is astonishing,” said co-author Dr Alex Liu of Cambridge’s Department of Earth Sciences, who was one of Brasier’s PhD students in Oxford at the time that studies of the fossil began.

According to the researchers, the reason this particular piece of brain tissue has been so well-preserved is that the dinosaur’s brain was essentially ‘pickled’ in a highly acidic and low-oxygen body of water – similar to a bog or swamp – shortly after its death. This allowed the soft tissues to become mineralised before they decayed away completely, so that they could be preserved.

“What we think happened is that this particular dinosaur died in or near a body of water, and its head ended up partially buried in the sediment at the bottom,” said Norman. “Since the water had little oxygen and was very acidic, the soft tissues of the brain were likely preserved and cast before the rest of its body was buried in the sediment.”

Working with colleagues from the ̽��ֱ�� of Western Australia, the researchers used scanning electron microscope (SEM) techniques in order to identify the tough membranes, or meninges, that surrounded the brain itself, as well as strands of collagen and blood vessels. Structures that could represent tissues from the brain cortex (its outer layer of neural tissue), interwoven with delicate capillaries, also appear to be present. ̽��ֱ��structure of the fossilised brain, and in particular that of the meninges, shows similarities with the brains of modern-day descendants of dinosaurs, namely birds and crocodiles.

In typical reptiles, the brain has the shape of a sausage, surrounded by a dense region of blood vessels and thin-walled vascular chambers (sinuses) that serve as a blood drainage system. ̽��ֱ��brain itself only takes up about half of the space within the cranial cavity.

In contrast, the tissue in the fossilised brain appears to have been pressed directly against the skull, raising the possibility that some dinosaurs had large brains which filled much more of the cranial cavity. However, the researchers caution against drawing any conclusions about the intelligence of dinosaurs from this particular fossil, and say that it is most likely that during death and burial the head of this dinosaur became overturned, so that as the brain decayed, gravity caused it to collapse and become pressed against the bony roof of the cavity.

“As we can’t see the lobes of the brain itself, we can’t say for sure how big this dinosaur’s brain was,” said Norman. “Of course, it’s entirely possible that dinosaurs had bigger brains than we give them credit for, but we can’t tell from this specimen alone. What’s truly remarkable is that conditions were just right in order to allow preservation of the brain tissue – hopefully this is the first of many such discoveries.”

“I have always believed I had something special. I noticed there was something odd about the preservation, and soft tissue preservation did go through my mind. Martin realised its potential significance right at the beginning, but it wasn’t until years later that its true significance came to be realised,” said paper co-author Jamie Hiscocks, the man who discovered the specimen. “In his initial email to me, Martin asked if I’d ever heard of dinosaur brain cells being preserved in the fossil record. I knew exactly what he was getting at. I was amazed to hear this coming from a world renowned expert like him.”

̽��ֱ��research was funded in part by the Natural Environment Research Council (NERC) and Christ’s College, Cambridge.

Reference:
Martin D. Brasier et al.’ Remarkable preservation of brain tissues in an Early Cretaceous iguanodontian dinosaur.’ Earth System Evolution and Early Life: a Celebration of the Work of Martin Brasier. Geological Society, London, Special Publications, 448. (2016). DOI: 10.1144/SP448.3

Researchers have identified the first known example of fossilised brain tissue in a dinosaur from Sussex. ̽��ֱ��tissues resemble those seen in modern crocodiles and birds.

̽��ֱ��chances of preserving brain tissue are incredibly small, so the discovery of this specimen is astonishing.

Alex Liu

Fossilised dinosaur brains

Jamie Hiscocks

Image of specimen

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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

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A snapshot of life 560 million years ago

amb206 — Mon, 10 Mar 2014 12:00:00 +0000

Casts of a group of fossils that have puzzled palaeontologists for at least 60 years will go on display at the Sedgwick Museum of Earth Sciences in Cambridge today. ̽��ֱ��temporary exhibition – ‘Ediacaran Enigmas: Resolving the Fossil Record of Early Animals’ – showcases current research into life on Earth between 560 and 580 million years ago.

̽��ֱ��casts have been taken from impressions of fossils from the Ediacaran, a geological period formally ratified by the world’s scientists only ten years ago. ̽��ֱ��fossils – which some researchers suggest could be some of the earliest examples of animals – predate those from the Cambrian by around 40 million years.

̽��ֱ��15 examples of Ediacaran fossils on display in the exhibition date from a period when scientists believe that multicellular life on Earth was in the process of diverging into the major groups, or Kingdoms (such as fungi and animals) that we are familiar with today. Many of the fossils have not been shown in the UK before, and the display is the first research-based exhibition of Ediacaran material to be staged in the UK.

Twelve of the casts on display are of fossils found in the dramatic cliffs of Mistaken Point on the east coast of Newfoundland. “ ̽��ֱ��fossils seen on bedding planes [sheets of rock] at Mistaken Point are quite literally a snapshot of an ancient community – they capture a wide range of life-forms as they appeared at a particular moment in geological time,” said palaeontologist Dr Alex Liu, who has coordinated the exhibition with colleagues at the Department of Earth Sciences.

̽��ֱ��remaining three casts on show are of fossils from Charnwood in Leicestershire, including a cast of the iconic Ediacaran organism Charnia masoni, found by a schoolboy in 1957. Strange impressions had been recognised in Charnwood as long ago as 1848, but it was only with the 1957 discovery that their importance as true Precambrian fossils was realised. Similar fossils have since been found in Russia, Namibia and Australia, revealing that these organisms were widespread on the planet during Ediacaran time.

“When David Attenborough released a television documentary called ‘First Life’ about the Ediacaran biota in 2010, it sparked huge public interest in this time period,” said Liu. “We’re now working to find more, better-preserved material and to use the latest analytical techniques to discover new insights about the environments and organisms living during this fascinating interval.”

Mistaken Point, which may soon become a World Heritage Site, was first discovered by scientists in 1967. Liu has visited the site (so called because ships often foundered there having mistaken it for Cape Race to the east) each year since 2007. Jutting out into the Atlantic and often swathed in fog, its cliffs are rich in fossils – so rich that some planes contain as many as 4,000 specimens.

“These fossils can be interpreted as a single community, enabling researchers to look at aspects of their lifestyles including competition, feeding and reproduction. We can identify at least 22 different species of organism, many of which were anchored to the sediment with their fronds elevated into the water column,” said Liu.

With permission from the Parks and Natural Areas Division, Government of Newfoundland and Labrador, Liu took ‘peels’ (silicon rubber impressions) of the fossils in situ. To reach the site means a two-hour drive from the city of St John’s, a 40-minute journey along bumpy tracks, and then a 45-minute trek on foot across rough terrain.

Back in Cambridge, the peels are used by Liu and colleagues to make solid casts which, once painted, closely resemble the original rocky material. These casts are essentially replicas of impressions left in the rocks by organisms whose shapes resemble the fronds of modern ferns. ̽��ֱ��largest cast on display is of an organism almost 60 cm in diameter. ̽��ֱ��smallest is a 20 mm-long fossil of a Charnia.

̽��ֱ��bedding planes from which these fossils originate offer precious clues about early life forms. Canadian palaeontologists working on the material from Mistaken Point favour the argument that they are examples of early stem group animals, from which the major groups of modern animals – such as molluscs, cnidarians and sponges – evolved. Others suggest that they are a “failed evolutionary experiment” in multicellular life that has subsequently gone extinct.

Liu said: “ ̽��ֱ��big question is whether we can find convincing evidence for the presence of features in these fossils that can conclusively determine their biological relationships. In the past, study of their overall structure has not revealed many useful features, so by applying modern techniques, and considering evidence for how they might have been behaving – in terms of feeding, movement, or reproduction – we are hoping that we can determine exactly what these organisms were.”

He and his colleagues hope that the display will raise awareness of the fascinating research going on to establish more about these fossils and others from the same period. A slideshow accompanying the exhibition shows some of the field sites, the techniques used to study the fossils, and a virtual reconstruction of these ancient ecosystems.

“ ̽��ֱ��casts enable us to look in detail at the fossils, and to determine their fine morphological structure,” said Liu. “Many of the impressions in the rock are low relief, which means that they are hard to spot except when the sun is low in the sky. In the laboratory we can control the lighting so that we can see them in all their glory. ̽��ֱ��way we have lit them in the display cases should show how important this is.”

̽��ֱ��exhibition, ‘Ediacaran Enigmas: Resolving the Fossil Record of Early Animals’, runs until December 2014. ̽��ֱ��Sedgwick Museum of Earth Sciences is open to the public Monday to Saturday. For opening hours and all other information go to http://www.sedgwickmuseum.org/

For more information about this story contact Alexandra Buxton, Communications Office, ̽��ֱ�� of Cambridge, amb206@admin.cam.ac.uk 01223 761673.

Inset images top and bottom: Mistaken Point, Newfoundland (Jack Matthews). Images centre: fossils from the famous fossil-bearing surfaces (Alex Liu)

A new display at the Sedgwick Museum focuses on the latest research into a group of fossils that might be the earliest examples of animals ever found. Palaeontologist Dr Alex Liu hopes that the exhibition will raise awareness of the unique organisms that lived in the Ediacaran period.

These fossils can be interpreted as a single community, enabling researchers to look at aspects of their lifestyles including competition, feeding and reproduction.

Alex Liu, Department of Earth Sciences

Alex Liu

Casts of fossils such as this beautiful Fractofusus specimen from Newfoundland are on display

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