Cambrian hemichordate Burgess Shale fossil, new research

Gyaltsenglossus senis

From the Royal Ontario Museum in Canada:

Early Cambrian fossil: Bizarre half-billion-year-old worm with tentacles solves evolutionary mystery

August 27, 2020

New research undertaken by scientists at the Smithsonian National Museum of Natural History, Royal Ontario Museum (ROM) and University of Montreal, has uncovered fossils of a new species of marine animal, Gyaltsenglossus senis, (pronounced Gen-zay-gloss-us senis) that provides new evidence in the historical debate among zoologists: how the anatomies of the two main types of an animal group called the hemichordates are related. The fossils are over half-a-billion years old and were discovered at a Burgess Shale site in the Canadian Rockies. This discovery was published August 27, 2020, in the science journal Current Biology.

With the early evolution of hemichordates being contentious among researchers the discovery of Gyaltsenglossus senis is significant. It provides direct fossil evidence connecting the two major groups of hemichordates: the enteropneusta and pterobranchia.

Although enteropneusts and pterobranchs appear to be quite different types of animals they are closely related. This close relationship is supported by DNA analysis of present-day species. More broadly, the role of Gyaltsenglossus in understanding hemichordate evolution helps us understand the origins of a larger group of animals called deuterostomes (which includes humans) by clarifying what characteristics they may have shared with hemichordates early in their history.

The enteropneusta are a group of animals known commonly as acorn worms, which are long, mostly mud-burrowing animals, that can be found today in oceans around the world from the tropics to Antarctic. The other main group of animals within hemichordates are pterobranchs, which are microscopic animals that live in colonies, each protected by tubes they construct and which feed on plankton using a crown of tentacled arms.

“Acorn worms and pterobranchs look so different from each other that understanding the origins of their evolutionary relationship has been a major historical question in zoology,” said Dr. Karma Nanglu, Peter Buck Deep Time post-doctoral fellow at the Smithsonian National Museum of Natural History and lead author on this paper. “Answering this question has been made much harder by the extreme lack of fossils of these soft-bodied hemichordates. Throughout the half-billion-year-long history of hemichordates you can count on one hand the number of exceptional preserved fossil species.”

Despite being just two centimeters in length, the remarkably preserved soft tissues of the Gyaltsenglossus fossils reveal incredibly detailed anatomical structures. These details include the oval-shaped proboscis of acorn worms and a basket of feeding tentacles similar to those of pterobranchs. The age of these fossils, combined with the unique morphological combination of the two major hemichordate groups, makes this discovery a critical find for understanding early hemichordate evolution.

“An ancient animal with an intermediary anatomy between acorn worms and pterobranchs had been hypothesized before but this new animal is the clearest view of what the ancestral hemichordate may have looked like,” says Dr. Christopher Cameron, Associate Professor at the University of Montreal and a co-author on this study. “It’s exciting to have so many new anatomical details to help drive new hypotheses about hemichordate evolution.”

In the case of Gyaltsenglossus, the exceptional preservation of these fine details can be attributed to the unique environmental conditions of the Burgess Shale, which rapidly entombed ancient animals in underwater mudslides. Through a combination of factors, including slowing the rate of bacteria decaying the entombed animals’ bodies, the fossils of the Burgess Shale are preserved with far greater fidelity than typical fossil sites.

“The Burgess Shale has been pivotal in understanding early animal evolution since its discovery over 100 years ago,” says co-author Dr. Jean-Bernard Caron, Richard M. Ivey Curator of Invertebrate Palaeontology at the ROM and Associate Professor at the University of Toronto. Dr. Caron led the field expedition in 2010 which collected the 33 fossils of Gyaltsenglossus.

“In most localities, you would be lucky to have the hardest parts of animals, like bones and teeth, preserved, but at the Burgess Shale even the softest body parts can be fossilized in exquisite detail,” says Dr. Caron. “This new species underscores the importance of making new fossil discoveries to shine light on the most stubborn evolutionary mysteries.”

In this particular case, Gyaltsenglossus suggests that the ancestral hemichordate may have been able to use the feeding strategies of both of the modern groups. Like acorn worms, the long proboscis may have been used to feed on nutrient-filled marine mud, while at the same time, and like the pterobranchs, the array of six feeding arms was probably used to grab suspended food particles directly from the water above where it was crawling.

Hemichordates belong to a major division of animal life called Deuterostomia, which includes chordates like fish and mammals, and not the division of animal life called Protostomia, that includes arthropods such as insects and annelids such as earthworms. Dr. Nanglu explains, when looking at Gyaltsenglossus, we’re actually looking at a very, very distant relative of our own branch of vertebrate and human evolution.

“The close relationship between hemichordates and our own evolutionary group, the chordates, is one of the first things that made me excited to research them,” Nanglu explains. “Understanding the ancient connections that join animals like fish and even humans to their distant cousins like sea urchins and acorn worms is such an interesting area on the evolutionary tree and Gyaltsenglossus helps bring that link into focus a little bit more clearly.”

The original 1909 discovery and research about the Burgess Shale was made by Charles Walcott, who was Secretary of the Smithsonian Institution at the time. The Burgess Shale fossil sites are located within Yoho and Kootenay National Parks and are managed by Parks Canada.

Ocean wildlife, 540 million years ago

This video says about itself:

The Cambrian Explosion – First Life With David Attenborough

Travel back 3.5 Billion years to the dawn of life as we know it, then forward to 600 million years ago to the first animals and the dawning of the Cambrian explosion, all narrated by the legend Sir David Attenborough.

From the University of Saskatchewan in Canada:

Traces of ancient life tell story of early diversity in marine ecosystems

August 14, 2020

If you could dive down to the ocean floor nearly 540 million years ago just past the point where waves begin to break, you would find an explosion of life — scores of worm-like animals and other sea creatures tunneling complex holes and structures in the mud and sand — where before the environment had been mostly barren.

Thanks to research published today in Science Advances by a University of Saskatchewan (USask)-led international research team, this rapid increase in biodiversity — one of two such major events across a 100-million-year timespan 560 to 443 million years ago — is part of a clearer picture emerging of Earth’s ancient oceans and life in them.

“We can see from the trace fossils — tracks, trails, borings, and burrows animals left behind — that this particular environment of the ocean floor, the offshore, served as a ‘crucible’ for life,” said USask paleobiologist Luis Buatois, lead author of the article. “Over the next millions of years, life expanded from this area outwards into deeper waters and inwards into shallower waters.”

The research is the culmination of over 20 years of work from Buatois and the team which examined hundreds of rock formations in locations across every continent.

“Until now, these two events — the Cambrian Explosion and the Great Ordovician Biodiversification Event — have been understood mostly through the study of body fossils — the shells, carapaces and the bones of ancient sea creatures,” said Buatois. “Now we can confidently say that these events are also reflected in the trace fossil record which reveals the work of those soft-bodied creatures whose fleshy tissues rot very quickly and so are only very rarely preserved.”

For the first time, the team has shown evidence of animals actively “engineering” their ecosystem — through the construction of abundant and diverse burrows on the seafloor of the world’s oceans in this ancient time.

“Never underestimate what animals are capable of doing,” said USask paleobiologist Gabriela Mángano, co-author of the paper. “They can modify their physical and chemical environment, excluding other animals or allowing them to flourish by creating new resources. And they were definitely doing all these things in these ancient seas.”

The trace fossil-producing animals’ engineering efforts may have laid the foundation for greater diversity in marine life. The researchers identified a 20-million-year time lag during the Cambrian Explosion (the time when most of the major groups of animals first appear in the fossil record) between diversification in trace fossils and in animal body fossils, suggesting the later animals exploited changes which enabled them to diversify even more.

The research also helps resolve a big question from the geochemical record, which indicated much of the ancient ocean was depleted of oxygen and unsuitable for life. Like oceans today, the Cambrian ocean had certain areas that were full of life, while others lacked the necessary conditions to support it.

“The fact that trace fossil distribution shows that there were spots where life flourished adjacent to others devoid of animal activity all through the early Cambrian period is a strong argument in favor of the idea that zones with enough oxygen to sustain a diversity of animals co-existed with oxygen-depleted waters in deeper areas,” said Mángano. “It’s a situation similar to what happens in modern oceans with oxygen minimum zones in the outer part of the continental shelf and the upper part of the continental slope, but oxygenated ones in shallower water.”

The research could provide new insights from an evolutionary perspective into the importance of extensive rock formations of a similar vintage found in Canada and elsewhere, and help society to prepare for coming challenges.

“Understanding changes that took place early in the history of our planet may help us to face present challenges in modern oceans, particularly with respect to oxygen changes,” said Buatois.

Other members of the team are: USask PhD student Kai Zhou, University of Portsmouth researcher Nic Minter, Senckenberg am Meer institute (Hamburg) researcher Max Wisshak, College of Wooster (Ohio) paleontologist Mark Wilson, and statistician Ricardo Olea of the United States Geological Survey.

The research was funded by grants from Canada’s Natural Sciences and Engineering Research Council awarded to Buatois and Mángano.

How trilobites grew, new research

This 2017 video from the USA is called Elrathia kingi – Trilobite Fossil.

From the American Museum of Natural History:

Growth rate of common trilobites

July 15, 2020

If you’ve ever held a trilobite fossil, seen one in a classroom, or walked by one in a store, chances are it was Elrathia kingii, one of the most common and well-recognized trilobites, and collected by the hundreds of thousands in western Utah. But despite the popularity of this species, scientists had not determined how it grew — from hatchling to juvenile to adult — until now. New work from the American Museum of Natural History published today in the journal Papers in Palaeontology describes the development and growth rate of Elrathia kingii — only the second such dataset to be compiled for a trilobite — allowing for the first comparison among trilobite species.

“There’s quite a big size range among trilobites. Some never got bigger than about a centimeter, while the largest on record is 72 centimeters (28 inches),” said Melanie Hopkins, an associate curator in the Museum’s Division of Paleontology and the study’s author. “Growth-rate studies like this one can help us tackle some of the big-picture questions: How did some trilobites get so big? What was the environmental context for that? And how did body size evolve over the evolutionary history of the clade?”

Trilobites are a group of extinct marine arthropods — distantly related to the horseshoe crab — that lived for almost 300 million years. They were incredibly diverse, with more than 20,000 described species. Their fossilized exoskeletons are preserved in sites all over the world, from the United States to China. Like insects, they molted throughout their lifetimes, leaving clues to how they changed during development. But to calculate the species’ growth rate, scientists need fossils representing all stages of the animal’s life — and lots of them.

“There are tons of specimens of Elrathia kingii out there but most of them are adults, and data from exactly where they were collected is inconsistent,” Hopkins said. “I needed material that I could collect from as small a section as possible that included a lot of juveniles.”

So in May 2018, Hopkins spent five days in Utah with a crew consisting of Museum staff and volunteers at a new fossil site said to preserve bucketloads of Elrathia kingii. By the end of the trip, they had collected about 500 specimens — many of them juveniles, which can be as small as half a millimeter long — from a section of outcrop just 1.5 meters (about 5 feet) long.

Hopkins estimated the growth rate and compared it to previously published data on a different trilobite, Aulacopleura konincki — the first time two trilobite species have been compared in this way. The two species look very similar and Hopkins found that they also grow in similar ways: for example, the growth of the trunk — the area immediately below the trilobite’s head made up of segments that increase with age — was controlled by a growth gradient, with those that were younger and closer to the back of the body undergoing faster growth. But while Elrathia kingii was smaller in early development and went through fewer molts before adulthood, it had faster growth rates, ultimately reaching sizes on par with Aulacopleura konincki, the largest of which are about 4 centimeters long.

In future studies, Hopkins is planning to add growth-rate data on different, more diverse-looking trilobite species to her models.

Cambrian fossil spider relative discovery

This 2013 video says about itself:

The Maotianshan Shales

This video goes into depth about one of the largest fossil deposits of the Cambrian, with early fish, trilobites, and much more.

From Harvard University, Department of Organismic and Evolutionary Biology in the USA:

MicroCT reveals detailed head morphology of arthropod, Leanchoilia illecebrosa

June 25, 2020

Summary: Researchers used microCT to study and re-study arthropod fossils from the early Cambrian in the Chengjiang biota in the Yunnan Province of China. Their latest study shows with unprecedented clarity the head morphology of the species Leanchoilia illecebrosa and demonstrates the presence of a labrum thus supporting the hypothesis that megacheirans are distant relatives of modern chelicerates (e.g. horseshoe crabs, scorpions and spiders).

The Chengjiang biota in the Yunnan Province of China contains one of the most species-rich and well-preserved fossiliferous deposits for the early Cambrian (ca. 518 million years old), including numerous arthropod species. However, several Chengjiang arthropods have an unfamiliar morphology, are extremely rare, or are incompletely preserved, which often leads to many of these species being problematic, poorly known, or often both, thus hindering their contribution towards reconstructing the evolution of this major animal group.

Javier Ortega-Hernández, Assistant Professor in the Department of Organismic and Evolutionary Biology and Curator of Invertebrate Paleontology in the Museum of Comparative Zoology at Harvard University, and Yu Liu, Professor of Paleobiology, Yunnan University, China have collaborated for years in the study of Chengjiang arthropods and their evolutionary significance. Their latest paper in Current Biology shows with unprecedented clarity the head morphology of the species Leanchoilia illecebrosa — a member of Megacheira, a major extinct group characterized by distinctively raptorial great appendages. Ortega-Hernández’s and Liu’s reexamination of Leanchoilia demonstrates the presence of a labrum — a flap-like structure overlying the mouth opening in most modern arthropods — and offers renewed support to the hypothesis that megacheirans are distant relatives of modern chelicerates (e.g. horseshoe crabs, scorpions and spiders).

Ortega-Hernández and Liu used microCT, a technique that uses X-rays to visualize features that are not easily observable on the surface of the fossils, to study the organization of the head in small juveniles of Leanchoilia illecebrosa. With microCT, they were able to understand the head in greater detail than ever before, and discover features that refute previously believed hypotheses.

“The biggest surprise came when studying structures close to the mouth,” said Ortega-Hernández. “Until now, the very existence of a labrum in megacheirans, and its position relative to the mouth, have been the source of heated debate. In living arthropods, the labrum is considered an important feature of the head because of its precise origin during embryonic development. The 3D data on Leanchoilia allowed us to show for the first time and with great clarity that this animal indeed had a labrum. This is a useful discovery because researchers have argued with each other whether a labrum was present or not in this and other closely related species, which has prompted very different interpretations about their evolution and affinities.”

The paper is the fifth in a series of publications that represent an ongoing collaboration between the research groups led by Ortega-Hernández and Liu. This study along with others in Current Biology (v29:1, 2019), BMC Evolutionary Biology (v19, 2019, and v20, 2020), and Geological Magazine (March 27, 2020) consists of the study, and often restudy, of exceptional arthropod fossils from the early Cambrian (ca. 518 million years ago) using microCT to reveal exceptional details of the preserved anatomy that are completely inaccessible through conventional preparation tools.

“With microCT, we can discern between the iron-rich fossils and the iron-depleted rock matrix to produce highly detailed and informative virtual models in 3D that reveal their affinities, ecology and evolutionary significance,” said Ortega-Hernández. “Although each publication is a bit different and tells a distinct story for the early evolution of arthropods, they all follow the same overall goal and structure, and use similar techniques and methodology.”

“We have several ongoing projects as part of this collaboration, including many new and exciting species, as well as re-descriptions of some old favorites,” said Ortega-Hernández. “There are certainly a few pleasant surprises, and we expect that this collaboration will continue yielding high-quality morphological information for several years, as we have only started to scratch the surface.” The ongoing project is partially funded by the Harvard China Fund.

Oldest parasitic animals discovered?

This 2016 video is called Top 10 Unique Species of the Cambrian Explosion.

By Jonathan Lambert today:

These tube-shaped creatures may be the earliest known parasites

Animals that lived over 500 million years ago may have stolen food from their hosts’ mouths

Tube-dwelling creatures that spent their lives cemented to the shells of clamlike brachiopods over 500 million years ago may be the earliest known parasites.

“Parasitism is an integral part of life on Earth, but it’s been hard to determine when it emerged,” says Tommy Leung, a parasitologist at the University of New England in Armidale, Australia. But, he says, it likely arose early, in part because today “practically every living thing has some kind of parasitic thing living on or in them, even down to parasites themselves.”

Sometimes, scientists get lucky and find parasites preserved with their hosts in amber (SN: 12/10/19). But usually, parasites don’t fossilize well because their bodies are often small and soft, Leung says. And even if two organisms happen to be entombed in the same fossil, it can be difficult to discern whether their relationship was parasitic, mutualistic or somewhere in between. Fossils of tongue worms from 425 million years ago represent a clear early example of parasitism, but previously found older fossils from the Cambrian only hint at possibly parasitic relationships.

Now, a 512-million-year-old bed of tube-encrusted brachiopods in Yunnan, China offers compelling evidence of a parasite-host relationship, Zhifei Zhang, a paleontologist at Northwest University in Xi’an, China and his colleagues report June 2 in Nature Communications.

In a tan-colored outcropping in southern China, researchers discovered thousands of brachiopods clustered together. Hundreds of them had numerous tubelike, tapered structures affixed to the exterior of the shells. Those structures were arrayed like the spines of a fan with the mouthlike parts positioned along the open edge of a shell. The tubes appeared only on brachiopods, never alone or associated with other fossils, suggesting that the organism couldn’t survive on its own.

The brachiopods were likely filter feeders, catching whatever food happened to drift into their open shells. Zhang and his colleagues hypothesized that these tubes might have snatched food from the edge of the shell before the brachiopod could eat it, making them kleptoparasites.

If that were true, tube-covered brachiopods should be lighter than their tube-free brethren, since they’re getting less food. The researchers estimated the mass of brachiopods with and without tubes, finding that the tube-free brachiopods were almost always heavier than their tube-laden brethren, though the number of tubes didn’t have any effect

The study “demonstrates these organisms had an intimate association,” says Leung, who wasn’t involved in the study. But he isn’t so sure that the relationship was antagonistic. If the relationship were truly parasitic, brachiopods with more tubes should be worse off, he says, but that wasn’t the case. While brachiopods with tubes were smaller, Leung says this might not reflect a cost of parasitism. Instead, the tube creatures might just prefer to affix to smaller shells.

Whether a relationship is parasitic or not can depend on the ecological context. Tube-laden clams might become stressed by tubes only if food becomes scarce. Or, perhaps tubes catch food too small for the brachiopods anyway. “With these kinds of relationships, the answer isn’t always that this is good or bad,” Leung says. “Interactions are usually more complicated than that.”

Ancient Cambrian worm, new genus discovery

Utahscolex, photo Anna Whitaker

From the University of Kansas in the USA:

Mysterious ancient sea-worm pegged as new genus after half-century in ‘wastebasket’

March 17, 2020

Summary: Fifty years ago, researchers placed a mystery worm in a ‘wastebasket‘ genus and interest in the lowly critter waned — until now.

When a partial fossil specimen of a primordial marine worm was unearthed in Utah in 1969, scientists had a tough go identifying it. Usually, such worms are recognized and categorized by the arrangement of little knobs on their plates. But in this case, the worm’s plates were oddly smooth, and important bits of the worm were missing altogether.

Discouraged, researchers placed the mystery worm in a “wastebasket” genus called Palaeoscolex, and interest in the lowly critter waned for the next 50 years.

That all changed recently when Paul Jamison, a teacher from Logan, Utah, and private collector, and his student Riley Smith were hunting fossils in the Spence Shale in Utah, a 506-million-year-old geologic unit housing a plethora of exceptionally preserved soft-bodied and biomineralized fossils. (Paleontologists call such a mother lode of fossils a “Lagerstätte.”) There, Smith discovered a second, more thoroughly preserved example of the worm.

Eventually, thanks to Jamison’s donation, the new fossil specimen arrived at the University of Kansas Biodiversity Institute, where Anna Whitaker, a graduate student in museum studies, researched and analyzed the worm with scanning electron microscopes, energy-dispersive X-ray spectrometry and optical microscopy.

At last, Whitaker determined the worm represented a new genus of Cambrian sea worm heretofore unknown to science. She’s the lead author of a description of the worm just published in the peer-reviewed paleontological journal PalZ.

“Before the new species that we acquired there was only one specimen known from the Spence Shale”, she said. “But with our new specimen we discovered it had characteristics that the original specimen didn’t have. So, we were able to update that description, and based on these new characteristics — we decided it didn’t fit in its old genus. So, we moved it to a new one.”

Whitaker and her colleagues — Jamison, James Schiffbauer of the University of Missouri and Julien Kimmig of KU’s Biodiversity Institute — named the new genus Utahscolex.

“We think they’re closely related to priapulid worms that exist today — you can find them in the oceans, and they are very similar to priapulids based on their mouthparts,” Whitaker said. “What’s characteristic about these guys is that they have a proboscis that can evert, so it can turn itself inside out and it’s covered with spines — that’s how it grabs food and sucks it in. So, it behaved very similarly to modern priapulid worms.”

While today, Utah is not a place you’d look for marine life, the case was different 506 million years ago, when creatures preserved in the Spence Shale were fossilized.

“The Spence Shale was a shelf system, and it’s really interesting because it preserves a lot of environments — nearshore to even deeper offshore, which is kind of unusual for a Lagerstätte, and especially during the Cambrian. These animals were living in kind of a muddy substrate. This worm was a carnivore, so it was preying on other critters. But there would have been whole diversity of animals — sponges, and trilobites scuttling along. We have very large, for the time, bivalve arthropods that would be predators. The Spence has a very large diversity of arthropods. It would have looked completely alien to us today.”

Whitaker hopes to complete her master’s degree this spring, then to attend the University of Toronto to earn her doctorate. The description of Utahscolex is Whitaker’s first academic publication, but she hopes it won’t be her last. She said the opportunity to perform such research is a chief reason for attending KU.

“I came for the museum studies program,” she said. “It’s one of the best in the country, and the program’s flexibility has allowed me to focus on natural history collections, which is what I hopefully will have a career in, and also gain work experience in the collections and do research — so it’s kind of everything I was looking for in the program.”

While ancient sea worms could strike many as a meaninglessly obscure subject for such intense interest and research, Whitaker said filling in gaps in the fossil record leads to a broader understanding of evolutionary processes and offers more granular details about the tree of life.

“I know some people might say, ‘Why should we care about these?'” she said. “But the taxonomy of naming all these species is really an old practice that started in the 1700s. It underpins all the science that we do today. Looking at biodiversity through time, we have to know the species diversity; we have to know as correctly as we can how many species there were and how they were related to each other. This supports our understanding of — as we move into bigger and bigger, broader picture — how we can interpret this fossil record correctly, or as best we can.”

Cambrian arthropod predator discovery

With a spaceship-shaped carapace, rakelike claws and a round tooth-filled mouth, Cambroraster falcatus (shown in an artist’s rendition) hunted for food along the seafloor. Lars Fields © Royal Ontario Museum

By Carolyn Gramling, 7:01pm, July 30, 2019:

This newfound predator may have terrorized the Cambrian seafloor

With rakelike claws and a toothy mouth, it could snag prey even under the sand

A fierce predator, with spiny claws and a round, rasping mouth, terrorized the Cambrian seafloor 508 million years ago as it raked through the sand in search of food.

Dubbed Cambroraster falcatus, the predator was about 30 centimeters long — which, to the tiny prey of the time, likely seemed monstrous enough. But C. falcatus also had a pair of jointed limbs that ended in rakelike claws, a round mouth lined with sharp, serrated plates and a broad, shield-shaped carapace that covered its head and most of its back, giving it a distinct resemblance to a horseshoe crab, or perhaps a spaceship.

Researchers, who describe C. falcatus for the first time July 31 in the Proceedings of the Royal Society B, have now found hundreds of fossils of the ancient arthropod — including one showing the critter’s entire body, both front and back — in Canada’s Burgess Shale (SN: 4/27/19, p. 32).

The creature’s round, tooth-filled mouth “is a type of mouth that doesn’t exist anymore,” and is characteristic of an extinct group of arthropods called radiodonts, says Jean-Bernard Caron, a paleontologist at the Royal Ontario Museum in Toronto. Radiodonts, in general, are rare in the fossil record, Caron says.

So it was all the more remarkable to find so many specimens of C. falcatus in one location, where the animals may have gathered thanks to abundant food. A mass molting event may also have occurred at the site, the researchers speculate, which would help explain the clusters of appendages and carapaces.

The team spotted what turned out to be the first specimen of C. falcatus in 2012. “But we didn’t know what we were looking at” because the specimens were mostly just bits and pieces, Caron says. Then, in 2016, Caron and paleontologist Joseph Moysiuk of the University of Toronto found the key to the puzzle: a nearly complete fossil of the creature.

Cambroraster refers both to the Cambrian Period when this critter reigned and to the rakelike shape of its front claws, and falcatus to the sickle shape of the carapace. C. falcatus may have used its long, spiky claws to rake through the sand and form a kind of basket in which it trapped animals such as worms, small arthropods and even small fish. It may also have plowed through sediment with its spaceship-shaped head.

“What’s striking about this animal is that it opens a new window into predation during the Cambrian,” Caron says. Previous fossil finds sketched a relatively simple ecosystem structure, he says: Shrimplike predator Anomalocaris was at the top, and some smaller specialized arthropods like trilobites scuttled along the seafloor.

But C. falcatus was something else, he says: a remarkable and fierce predator that occupied its own niche, with adaptations “that really allowed it to feed on anything living in the mud.”

The researchers were surprised to find that many of today’s carnivorous species trace this diet back all the way to the base of the animal evolutionary tree, more than 800 million years, predating the oldest known fossils that paleontologists have been able to assign to animal origins with certainty. … So if the first animal was a carnivore, what did it prey on?The authors suggest the answer might lie with protists, including choanoflagellates: tiny, single-celled organisms considered to be the closest living relatives of the animals. Living as plankton in marine and freshwater, choanoflagellates are vaguely reminiscent of miniature versions of the shuttlecock batted back and forth during a game of badminton. A funnel-shaped collar of “hairs” surrounds a whip-like appendage called a flagellum whose rhythmic beating sucks a steady stream of water through the collar, filtering out bacteria and detritus that is then absorbed and digested. It is possible that the common ancestor of today’s animals was a creature very similar to a choanoflagellate: here.

“The ancient creature that is most closely related to all animals living today might have eaten bacteria and other protists rather than plants,” Wiens said.

Cambrian life explosion, because of volcanoes?

This 2016 video says about itself:

Right at the beginning of the Paleozoic, there was a huge explosion of more complex life. And that’s when things started to get really interesting.

From the University of Exeter in England:

Plate tectonics may have driven ‘Cambrian Explosion’

June 19, 2019

The quest to discover what drove one of the most important evolutionary events in the history of life on Earth has taken a new, fascinating twist.

A team of scientists have given a fresh insight into what may have driven the “Cambrian Explosion” — a period of rapid expansion of different forms of animal life that occurred over 500 million years ago.

While a number of theories have been put forward to explain this landmark period, the most credible is that it was fuelled by a significant rise in oxygen levels which allowed a wide variety of animals to thrive.

The new study suggests that such a rise in oxygen levels was the result of extraordinary changes in global plate tectonics.

During the formation of the supercontinent ‘Gondwana’, there was a major increase in continental arc volcanism — chains of volcanoes often thousands of miles long formed where continental and oceanic tectonic plates collided. This in turn led to increased ‘degassing’ of CO2 from ancient, subducted sedimentary rocks.

This, the team calculated, led to an increase in atmospheric CO2 and warming of the planet, which in turn amplified the weathering of continental rocks, which supplied the nutrient phosphorus to the ocean to drive photosynthesis and oxygen production.

The study was led by Josh Williams, who began the research as an MSc student at the University of Exeter and is now studying for a PhD at the University of Edinburgh.

During his MSc project he used a sophisticated biogeochemical model to make the first quantification of changes in atmospheric oxygen levels just prior to this explosion of life.

Co-author and project supervisor Professor Tim Lenton, from the University of Exeter’s Global Systems Institute said: “One of the great dilemmas originally recognised by Darwin is why complex life, in the form of fossil animals, appeared so abruptly in what is now known as the Cambrian explosion.

“Many studies have suggested this was linked to a rise in oxygen levels — but without a clear cause for such a rise, or any attempt to quantify it.”

Not only did the model predict a marked rise in oxygen levels due to changes in plate tectonic activity, but that rise in oxygen — to about a quarter of the level in today’s atmosphere — crossed the critical levels estimated to be needed by the animals seen in the Cambrian explosion.

Williams added: “What is particularly compelling about this research is that not only does the model predict a rise in oxygen to levels estimated to be necessary to support the large, mobile, predatory animal life of the Cambrian, but the model predictions also show strong agreement with existing geochemical evidence.”

“It is remarkable to think that our oldest animal ancestors — and therefore all of us — may owe our existence, in part, to an unusual episode of plate tectonics over half a billion years ago” said Professor Lenton.

Giant trilobite discovery in Australia

This April 2020 video us called

A 13 June 2019 video used to say about itself:

Fossils of giant new species of sea creature found on South Australia’s Kangaroo Island

The fossils of a giant new species of sea creature have been found on Kangaroo Island, with experts saying it was likely the “terror” of other creatures on the seafloor.

Researchers said the discovery of a group of sea creatures called trilobites added insights to knowledge of the Cambrian explosion, the greatest diversification event in the history of life on Earth.

The fossils, called Redlichia rex, were the largest Cambrian trilobite to be discovered in Australia. Trilobites, which had hard, calcified, armour-like skeletons over their bodies, were related to modern crustaceans and insects. They were one of the most successful fossil animal groups, surviving for about 270 million years.

The new species was discovered at Emu Bay on Kangaroo Island, where more than 100 other species were discovered, including some with soft parts intact.

From the University of Adelaide in Australia:

New ‘king’ of fossils discovered in Australia

T. rex‘ of trilobites had formidable legs with spines for crushing, shredding

June 13, 2019

Fossils of a giant new species from the long-extinct group of sea creatures called trilobites have been found on Kangaroo Island, South Australia.

The finding is adding important insights to our knowledge of the Cambrian ‘explosion’, the greatest diversification event in the history of life on Earth, when almost all animal groups suddenly appeared over half-a-billion years ago.

Trilobites, which had hard, calcified, armour-like skeletons over their bodies, are related to modern crustaceans and insects. They are one of the most successful fossil animal groups, surviving for about 270 million years (521 to 252 million years ago). Because of their abundance in the fossil record, they are considered a model group for understanding this evolutionary period.

“We decided to name this new species of trilobite Redlichia rex (similar to Tyrannosaurus rex) because of its giant size, as well as its formidable legs with spines used for crushing and shredding food — which may have been other trilobites,” says James Holmes, PhD student with the University of Adelaide’s School of Biological Sciences, who led the research.

The preservation of trilobite ‘soft parts’ such as the antennae and legs is extremely rare. The new species was discovered at the Emu Bay Shale on Kangaroo Island, a world-renowned deposit famous for this type of preservation. The findings have been published in the Journal of Systematic Palaeontology by a team of scientists from the University of Adelaide, South Australian Museum and the University of New England.

The new species is about 500 million years old, and is the largest Cambrian trilobite discovered in Australia. It grew to around 30 cm in length, which is almost twice the size of other Australian trilobites of similar age.

“Interestingly, trilobite specimens from the Emu Bay Shale — including Redlichia rex — exhibit injuries that were caused by shell-crushing predators,” says senior study author Associate Professor Diego García-Bellido, from the University of Adelaide and the South Australian Museum.

“There are also large specimens of fossilised poo (or coprolites) containing trilobite fragments in this fossil deposit. The large size of injured Redlichia rex specimens and the associated coprolites suggests that either much bigger predators were targeting Redlichia rex, such as Anomalocaris — an even larger shrimp-like creature — or that the new species had cannibalistic tendencies.”

One of the major drivers of the Cambrian explosion was likely an evolutionary “arms race” between predators and prey, with each developing more effective measures of defence (such as the evolution of shells) and attack.

“The overall size and crushing legs of Redlichia rex are a likely consequence of the arms race that occurred at this time” says James Holmes. “This giant trilobite was likely the terror of smaller creatures on the Cambrian seafloor.”

Specimens of Redlichia rex and other Emu Bay Shale fossils are currently on display in the South Australian Museum.

Cambrian age sea star ancestor discovery

This June 2018 video is called The Evolution of Echinoderms.

From Ohio State University in the USA:

Scientists discover evolutionary link to modern-day sea echinoderms

Research team solves fossil mystery, identifies new species

May 2, 2019

Scientists at The Ohio State University have discovered a new species that lived more than 500 million years ago — a form of ancient echinoderm that was ancestral to modern-day groups such as sea cucumbers, sea urchins, sea stars, brittle stars and crinoids. The fossil shows a crucial evolutionary step by echinoderms that parallels the most important ecological change to have taken place in marine sediments.

The discovery, nearly 30 years in the making, was published recently in the Bulletin of Geosciences and provides a clue as to how creatures were able to make the evolutionary leap from living stuck to marine sediment grains — which were held together by gooey algae-like colonies, the original way that echinoderms lived — to living attached to hard, shelly surfaces, which is the way their modern-day descendants live now on the bottom of the ocean.

“It throws light on a critical time, not just in the evolution of organisms, but also in the evolution of marine ecosystems,” said Loren Babcock, co-author of the study and professor of earth sciences at Ohio State. “This represents a creature that clearly was making the leap from the old style of marine ecosystems in which sediments were stabilized by cyanobacterial mats, to what ultimately became the present system, with more fluidized sediment surfaces.”

The creature, a species of edrioasteroid echinoderm that Babcock and his researchers named Totiglobus spencensis, lived in the Cambrian Period — about 507 million years ago. (The Earth, for the record, is about 4.5 billion years old.) A family of fossil hunters discovered the fossil in shale of Spence Gulch, in the eastern part of Idaho, in 1992, and donated it to Richard Robison, a researcher at the University of Kansas and Babcock’s doctoral adviser. That part of the country is rich with fossils from the Cambrian period, Babcock said.

For years, the fossil puzzled both Babcock and Robison. But the mystery was solved a few years ago, when Robison’s fossil collection passed to Babcock after Robison’s retirement.

Once Babcock had the fossil in his lab, he and a visiting doctoral student, Rongqin Wen, removed layers of rock, exposing a small, rust-colored circle with numerous tiny plates and distinct arm-like structures, called ambulcra. Further study showed them that the animal attached itself to a small, conical shell of a mysterious, now-extinct animal called a hyolith using a basal disk — a short, funnel-like structure composed of numerous small calcite plates.

The discovery was a type of scientific poetry — years earlier, Babcock and Robison discovered the type of shell that this animal appeared to be attached to, and named it Haplophrentis reesei.

The edrioasteroid that Babcock and Wen discovered apparently lived attached to the upper side of the elongate-triangular hyolith shell, even as the hyolith was alive. They think a sudden storm buried the animals in a thick layer of mud, preserving them in their original ecological condition.

Echinoderms and hyoliths first appeared during the Cambrian Period, a time in Earth’s history when life exploded and the world became more biodiverse than it had ever been before. The earliest echinoderms, including the earliest edrioasteroids, lived by sticking to cyanobacterial mats — thick, algae-like substances that covered the Earth’s waters. And until the time of Totiglobus spencensis, echinoderms had not yet figured out how to attach to a hard surface.

“In all of Earth’s history, the Cambrian is probably the most important in the evolution of both animals and marine ecosystems, because this was a time when a more modern style of ecosystem was first starting to take hold,” Babcock said. “This genus of the species we discovered shows the evolutionary transition from being a ‘mat-sticker’ to the more advanced condition of attaching to a shelly substrate, which became a successful model for later species, including some that live today.”

In the early part of the Cambrian Period — which started about 538 million years ago — echinoderms likely lived on that algae-like substance in shallow seas that covered many areas of the planet. The algae, Babcock said, probably was not unlike the cyanobacterial mats that appear in certain lakes, including Lake Erie, each summer. But at some point, those algae-like substances became appealing food for other creatures, including prehistoric snails. During the Cambrian, as the population of snails and other herbivores exploded, the algae-like cyanobacterial mats began to disappear from shallow seas, and sediments became too physically unstable to support the animals — including echinoderms — that had come to rely on them.

Once their algae-like homes became food for other animals, Babcock said, echinoderms either had to find new places to live or perish.

Paleontologists knew that the creatures had somehow managed to survive, but until the Ohio State researchers’ discovery, they hadn’t seen much evidence that an echinoderm that lived this long ago had made the move from living stuck to cyanobacterial-covered sediment to living attached to hard surfaces.

“This evolutionary choice — to move from mat-sticker to hard shelly substrate — ultimately is responsible for giving rise to attached animals such as crinoids,” Babcock said. “This new species represents the link between the old lifestyle and the new lifestyle that became successful for this echinoderm lineage.”