̽��ֱ�� of Cambridge - Martin Smith

“A load of old rot”: fossil of oldest known land-dweller identified

sc604 — Wed, 02 Mar 2016 08:38:45 +0000

A fossil dating from 440 million years ago is not only the oldest example of a fossilised fungus, but is also the oldest fossil of any land-dwelling organism yet found. ̽��ֱ��organism, and others like it, played a key role in laying the groundwork for more complex plants, and later animals, to exist on land by kick-starting the process of rot and soil formation, which is vital to all life on land.

This early pioneer, known as Tortotubus, displays a structure similar to one found in some modern fungi, which likely enabled it to store and transport nutrients through the process of decomposition. Although it cannot be said to be the first organism to have lived on land, it is the oldest fossil of a terrestrial organism yet found. ̽��ֱ��results are published in the Botanical Journal of the Linnean Society.

“During the period when this organism existed, life was almost entirely restricted to the oceans: nothing more complex than simple mossy and lichen-like plants had yet evolved on the land,” said the paper’s author Dr Martin Smith, who conducted the work while at the ̽��ֱ�� of Cambridge’s Department of Earth Sciences, and is now based at Durham ̽��ֱ��. “But before there could be flowering plants or trees, or the animals that depend on them, the processes of rot and soil formation needed to be established.”

Working with a range of tiny microfossils from Sweden and Scotland, each shorter than a human hair is wide, Smith attempted to reconstruct the method of growth for two different types of fossils that were first identified in the 1980s. These fossils had once been thought to represent parts of two different organisms, but by identifying other fossils with ‘in-between’ forms, Smith was able to show that the fossils actually represented parts of a single organism at different stages of growth. By reconstructing how the organism grew, he was able to show that the fossils represent mycelium – the root-like filaments that fungi use to extract nutrients from soil.

It’s difficult to pinpoint exactly when life first migrated from the seas to the land, since useful features in the fossil record that could help identify the earliest land colonisers are rare, but it is generally agreed that the transition started early in the Palaeozoic era, between 500 and 450 million years ago. But before any complex forms of life could live on land, there needed to be nutrients there to support them. Fungi played a key role in the move to land, since by kick-starting the rotting process, a layer of fertile soil could eventually be built up, enabling plants with root systems to establish themselves, which in turn could support animal life.

Fungi play a vital role in the nitrogen cycle, in which nitrates in the soil are taken up by plant roots and passed along food chain into animals. Decomposing fungi convert nitrogen-containing compounds in plant and animal waste and remains back into nitrates, which are incorporated into the soil and can again be taken up by plants. These early fungi started the process by getting nitrogen and oxygen into the soil.

Smith found that Tortotubus had a cord-like structure, similar to that of some modern fungi, in which the main filament sends out primary and secondary branches that stick back onto the main filament, eventually enveloping it. This cord-like structure is often seen in land-based organisms, allowing them to spread out and colonise surfaces. In modern fungi, the structure is associated with the decomposition of matter, allowing a fungus colony to move nutrients to where they are needed – a useful adaptation in an environment where nutrients are scarce and unevenly distributed.

In contrast with early plants, which lacked roots and therefore had limited interaction with activity beneath the surface, fungi played an important role in stabilising sediment, encouraging weathering and forming soils.

“What we see in this fossil is complex fungal ‘behaviour’ in some of the earliest terrestrial ecosystems – contributing to soil formation and kick-starting the process of rotting on land,” said Smith. A question, however, is what was there for Tortotubus to decompose. According to Smith, it’s likely that there were bacteria or algae on land during this period, but these organisms are rarely found as fossils.

Additionally, the pattern of growth in Tortotubus echoes that of the mushroom-forming fungi, although unambiguous evidence of mushrooms has yet to be found in the Palaeozoic fossil record. “This fossil provides a hint that mushroom-forming fungi may have colonised the land before the first animals left the oceans,” said Smith. “It fills an important gap in the evolution of life on land.”

̽��ֱ��research was supported by Clare College, Cambridge.

Reference:
Martin R. Smith. ‘Cord-forming Palaeozoic fungi in terrestrial assemblages.’ Botanical Journal of the Linnean Society 180 (2016). DOI: 10.1111/boj.12389

̽��ֱ��earliest example of an organism living on land – an early type of fungus – has been identified. ̽��ֱ��organism, from 440 million years ago, likely kick-started the process of rot and soil formation, which encouraged the later growth and diversification of life on land.

Before there could be flowering plants or trees, or the animals that depend on them, the processes of rot and soil formation needed to be established.

Martin Smith

Martin R. Smith

Filaments of Tortotubus

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Newly-discovered ‘ring of teeth’ helps determine what common ancestor of moulting animals looked like

sc604 — Wed, 24 Jun 2015 17:00:29 +0000

A new study of an otherworldly creature from half a billion years ago – a worm-like animal with legs, spikes and a head difficult to distinguish from its tail – has definitively identified its head for the first time, and revealed a previously unknown ring of teeth and a pair of simple eyes. ̽��ֱ��results, published today in the journal Nature, have helped scientists reconstruct what the common ancestor of everything from tiny roundworms to huge lobsters might have looked like.

Researchers from the ̽��ֱ�� of Cambridge, the Royal Ontario Museum and the ̽��ֱ�� of Toronto have found that the creature, known as Hallucigenia due to its strange appearance, had a throat lined with needle-like teeth, a previously unidentified feature which could help connect the dots between it, modern velvet worms and arthropods – the group which contains modern insects, spiders and crustaceans.

Arthropods, velvet worms (onychophorans) and water bears (tardigrades) all belong to the massive group of animals that moult, known as ecdysozoans. Though Hallucigenia is not the common ancestor of all ecdysozoans, it is a precursor to velvet worms. Finding this mouth arrangement in Hallucigenia helped scientists determine that velvet worms originally had the same configuration – but it was eventually lost through evolution.

“ ̽��ֱ��early evolutionary history of this huge group is pretty much uncharted,” said Dr Martin Smith, a postdoctoral researcher in Cambridge’s Department of Earth Sciences, and the paper’s lead author. “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 ̽��ֱ�� of Toronto. “We previously thought that neither velvet worms nor their ancestors had teeth. But Hallucigenia tells us that actually, velvet worm ancestors had them, and living forms just lost their teeth over time.”

Hallucigenia was just one of the weird creatures that lived during the Cambrian Explosion, a period of rapid evolutionary development starting about half a billion years ago, when most major animal groups first emerge in the fossil record.

At first, Hallucigenia threw palaeontologists for a bit of a loop. When it was identified in the 1970s, it was reconstructed both backwards and upside down: the spines along its back were originally thought to be legs, its legs were thought to be tentacles along its back, and its head was mistaken for its tail.

Right side up and right way round, Hallucigenia still looks pretty strange: it had pairs of lengthy spines along its back, seven pairs of legs ending in claws, and three pairs of tentacles along its neck. ̽��ֱ��animals were between 10 and 50 millimetres in length and lived on the floor of the Cambrian oceans.

More significantly, Hallucigenia’s unearthly appearance has made it difficult to link it to modern animal groups and to find its home in the Tree of Life. In 2014, research from Cambridge partially solved this problem by studying the structure of Hallucigenia’s claws, which helped definitively link it to modern velvet worms.

In the new work, researchers used electron microscopy to examine fossils from the collections of the Royal Ontario Museum and the Smithsonian Institution, definitively sorting Hallucigenia’s front from back, and making some surprising observations.

“Prior to our study there was still some uncertainty as to which end of the animal represented the head, and which the tail,” said Smith. “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.”

Identifying this end as the tail led Caron to revisit the fossils and dig away the sediment that was covering the head: the animals died as they were buried in a mudslide, and their floppy head often ended up pointing down into the mud. “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!”

̽��ֱ��new images show an elongated head with a pair of simple eyes, which sat above a mouth with a ring of teeth. In addition, Hallucigenia’s throat was lined with needle-shaped teeth. ̽��ֱ��fossils originated in the Burgess Shale of Yoho National Park in western Canada, one of the world’s richest sources of fossils from the Cambrian period.

̽��ֱ��ring of teeth that surrounded Hallucigenia’s mouth probably helped to generate suction, flexing in and out, like a valve or a plunger, in order to suck its food into its throat. ̽��ֱ��researchers speculate that the teeth in the throat worked like a ratchet, keeping food from slipping out of the mouth each time it took another ‘suck’ at its food.

“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.”

̽��ֱ��material for this study was collected between 1992 and 2000 and represents more than 165 additional Hallucigenia specimens – including many rare orientations and well-preserved specimens.

Parks Canada, which holds jurisdiction over the Burgess Shale sites located in Yoho and Kootenay national parks, is thrilled by this discovery and eager to share this exciting new piece of the ever-unfolding Burgess Shale story with their visitors.

̽��ֱ��research was funded by Clare College, Cambridge, the Natural Sciences and Engineering Research Council of Canada, and the Royal Ontario Museum.

A new analysis of one of the most bizarre-looking fossils ever discovered has definitively sorted its head from its tail, and turned up a previously unknown ring of teeth, which could help answer some of the questions around the early development of moulting animals.

̽��ֱ��early evolutionary history of this huge group is pretty much uncharted

Martin Smith

Left: Jean-Bernard Caron Right: Danielle Dufault

Left: Hallucigenia sparsa from the Burgess Shale (Royal Ontario Museum 61513) ̽��ֱ��fossil is 15 mm long. Right: Colour reconstruction of Hallucigenia sparsa.

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

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Compiling a ‘dentist’s handbook’ for penis worms

sc604 — Wed, 06 May 2015 04:00:00 +0000

It sounds like something out of a horror movie: a penis-shaped worm which was able to turn its mouth inside out and drag itself around by its tooth-lined throat, which resembled a cheese grater. But a new study of the rather unfortunately-named penis worm has found that their bizarre dental structure may help in the identification of previously unrecognised fossil specimens from the time on Earth when animals were first coming into their own.

Reconstructing the teeth of penis worms, or priapulids, in fine detail has enabled researchers from the ̽��ֱ�� of Cambridge to compile a ‘dentist’s handbook’ which has aided in the identification of fossilised teeth from a number of previously-unrecognised penis worm species from all over the world. ̽��ֱ��results are published today (6 May) in the journal Palaeontology.

̽��ֱ��researchers used electron microscopy to examine the internal structure of the teeth of these creatures, which first emerged during the ‘Cambrian explosion’, a period of rapid evolutionary development about half a billion years ago, when most major animal groups first appear in the fossil record.

̽��ֱ��teeth of these Cambrian priapulids had different shapes according to their function: some were shaped like a cone fringed with tiny prickles and hairs, some were shaped like a bear claw, and some like a city skyline.

During the Cambrian, most animals were soft-bodied, like worms and sponges. Therefore, outside of the few very special places where conditions are just right to enable preservation of soft-bodied creatures, it is difficult to know for certain how far certain species were distributed across the Earth at the time.

“As teeth are the most hardy and resilient parts of animals, they are much more common as fossils than whole soft-bodied specimens,” said Dr Martin Smith, a postdoctoral researcher in Cambridge’s Department of Earth Sciences and the paper’s lead author. “But when these teeth – which are only about a millimetre long – are found, they are easily misidentified as algal spores, rather than as parts of animals. Now that we understand the structure of these tiny fossils, we are much better placed to a wide suite of enigmatic fossils.”

Both modern and Cambrian penis worms have spent their lives burrowing into the sediment beneath the ocean since they first appeared 500 million years ago.

During the Cambrian, penis worms were voracious predators, gobbling up anything that crossed their path, including worms, shrimp and other marine creatures. They were able to turn their mouths inside out to reveal a tooth-lined throat that looked like a prehistoric cheese grater.

These teeth were not just used for eating food, however. By turning their mouths inside out, penis worms could also use their teeth like miniature grappling hooks, using them to grip a surface and then pull the rest of their bodies along behind.

“Modern penis worms have been pushed to the margins of life, generally living in extreme underwater environments,” said Smith. “But during the Cambrian, they were fearsome beasts, and extremely successful ones at that.”

For this study, the researchers examined fossils of Ottoia, a type of penis worm, about the length of a finger, which lived during the Cambrian. ̽��ֱ��fossils originated from the Burgess Shale in Western Canada, the world’s richest source of fossils from the period, full of weird and wacky-looking creatures that have helped scientists understand how animal life on Earth developed.

Using high resolution electron and optical microscopy, they were able to expose the curious structure of Ottoia’s teeth for the first time. By reconstructing the structure of these teeth in detail, the researchers were then able to identify fossilised teeth of a number of previously-unrecognised penis worm species from all over the world.

“Teeth hold all sorts of clues, both in modern animals and in fossils,” said Smith. “It’s entirely possible that unrecognised species await discovery in existing fossil collections, just because we haven’t been looking closely enough at their teeth, or in the right way.”

̽��ֱ��study was funded by Clare College, Cambridge, the Palaeontological Association, and the Natural Environment Research Council.

A new study of teeth belonging to a particularly phallic-looking creature has led to the compilation of a prehistoric ‘dentist’s handbook’ which may aid in the identification of previously unrecognised specimens from the Cambrian period, 500 million years ago.

Penis worms were fearsome beasts, and extremely successful ones at that

Martin Smith

Left: Smokeybjb via Wikimedia Commons. Right: Martin Smith.

Left: Illustration of Ottoia, a prehistoric priapulid, burrowing. Right: Ottoia worm.

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

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Misunderstood worm-like fossil finds its place in the Tree of Life

sc604 — Sun, 17 Aug 2014 17:00:00 +0000

̽��ֱ��animal, known as Hallucigenia due to its otherworldly appearance, had been considered an ‘evolutionary misfit’ as it was not clear how it related to modern animal groups. Researchers from the ̽��ֱ�� of Cambridge have discovered an important link with modern velvet worms, also known as onychophorans, a relatively small group of worm-like animals that live in tropical forests. ̽��ֱ��results are published in the advance online edition of the journal Nature.

̽��ֱ��affinity of Hallucigenia and other contemporary ‘legged worms’, collectively known as lobopodians, has been very controversial, as a lack of clear characteristics linking them to each other or to modern animals has made it difficult to determine their evolutionary home.

What is more, early interpretations of Hallucigenia, which was first identified in the 1970s, placed it both backwards and upside-down. ̽��ֱ��spines along the creature’s back were originally thought to be legs, its legs were thought to be tentacles along its back, and its head was mistaken for its tail.

Hallucigenia lived approximately 505 million years ago during the Cambrian Explosion, a period of rapid evolution when most major animal groups first appear in the fossil record. These particular fossils come from the Burgess Shale in Canada’s Rocky Mountains, one of the richest Cambrian fossil deposits in the world.

Looking like something from science fiction, Hallucigenia had a row of rigid spines along its back, and seven or eight pairs of legs ending in claws. ̽��ֱ��animals were between five and 35 millimetres in length, and lived on the floor of the Cambrian oceans.

A new study of the creature’s claws revealed an organisation very close to those of modern velvet worms, where layers of cuticle (a hard substance similar to fingernails) are stacked one inside the other, like Russian nesting dolls. ̽��ֱ��same nesting structure can also be seen in the jaws of velvet worms, which are no more than legs modified for chewing.

“It’s often thought that modern animal groups arose fully formed during the Cambrian Explosion,” said Dr Martin Smith of the ̽��ֱ��’s Department of Earth Sciences, the paper’s lead author. “But evolution is a gradual process: today’s complex anatomies emerged step by step, one feature at a time. By deciphering ‘in-between’ fossils like Hallucigenia, we can determine how different animal groups built up their modern body plans.”

While Hallucigenia had been suspected to be an ancestor of velvet worms, definitive characteristics linking them together had been hard to come by, and their claws had never been studied in detail. Through analysing both the prehistoric and living creatures, the researchers found that claws were the connection joining them together. Cambrian fossils continue to produce new information on origins of complex animals, and the use of high-end imaging techniques and data on living organisms further allows researchers to untangle the enigmatic evolution of earliest creatures.

“An exciting outcome of this study is that it turns our current understanding of the evolutionary tree of arthropods – the group including spiders, insects and crustaceans – upside down,” said Dr Javier Ortega-Hernandez, the paper’s co-author. “Most gene-based studies suggest that arthropods and velvet worms are closely related to each other; however, our results indicate that arthropods are actually closer to water bears, or tardigrades, a group of hardy microscopic animals best known for being able to survive the vacuum of space and sub-zero temperatures – leaving velvet worms as distant cousins.”

“ ̽��ֱ��peculiar claws of Hallucigenia are a smoking gun that solve a long and heated debate in evolutionary biology, and may even help to decipher other problematic Cambrian critters,” said Dr Smith.

One of the most bizarre-looking fossils ever found - a worm-like creature with legs, spikes and a head difficult to distinguish from its tail – has found its place in the evolutionary Tree of Life, definitively linking it with a group of modern animals for the first time.

̽��ֱ��spines along its back were thought to be legs, its legs thought to be tentacles along its back, and its head was mistaken for its tail.

M. R. Smith / Smithsonian Institute

Fossil Hallucigenia sparsa from the Burgess Shale

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