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 13 June 2019 video says 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.”

Comb jellies, jellyfish relatives after all?


This 21 August 2016 video says about itself:

Comb jellies look like creatures from another planet. Despite their name and physical appearance, these sea creatures are different from jellyfish. They’re also about as far from us on the tree of life as a species can get and still be considered an animal. But based on new research findings, we may have something very basic to our lives in common with them.

That was three years ago. Now, new research …

From the University of Bristol in England:

Half-a-billion-year-old fossil reveals the origins of comb jellies

March 21, 2019

One of the ocean’s little known carnivores has been allocated a new place in the evolutionary tree of life after scientists discovered its unmistakable resemblance with other sea-floor dwelling creatures.

Comb jellies occupy a pivotal place in the history of animal evolution with some arguing that they were among the first animals to evolve. Now an international team of palaeontologists have found fossil evidence that proves comb jellies are related to ancestors that sat on the sea floor with polyp-like tentacles.

As reported today in Current Biology, researchers from the University of Bristol, Yunnan University in China and London’s Natural History Museum, compared a 520 million-year-old fossil with fossils of a similar skeletal structure and found that all evolved from the same ancestors.

The fossil, set in a yellow and olive coloured mudstone and resembling a flower, was found in outcrops south of Kunming in the Yunnan Province, South China by Professor Hou Xianguang, co-author of the study.

Several amazingly preserved fossils have been unearthed from outcrops scattered among rice fields and farmlands in this part of tropical China in the last three decades.

It has been named Daihua after the Dai tribe in Yunnan and the Mandarin word for flower ‘Hua’, a cup-shaped organism with 18 tentacles surrounding its mouth. On the tentacles are fine feather-like branches with rows of large ciliary hairs preserved.

“When I first saw the fossil, I immediately noticed some features I had seen in comb jellies”, said Dr Jakob Vinther, a molecular palaeobiologist from the University of Bristol. “You could see these repeated dark stains along each tentacle that resembles how comb jelly combs fossilise. The fossil also preserves rows of cilia, which can be seen because they are huge. Across the Tree of Life, such large ciliary structures are only found in comb jellies.”

In today’s oceans, comb jellies are swimming carnivores. Some of them have become invasive pests. They swim using bands of iridescent, rainbow coloured comb rows along their body composed of densely packed cellular protrusions, known as cilia. Their hair-like structures are the largest seen anywhere in the tree of life.

The researchers noticed that Daihua resembled another fossil, a famous weird wonder from the Burgess Shale (508 million years old) called Dinomischus. This stalked creature also had 18 tentacles and an organic skeleton and was previously assigned to a group called entoprocts.

“We also realised that a fossil, Xianguangia, that we always thought was a sea anemone is actually part of the comb jelly branch”, said co-author Prof Cong Peiyun.

This emerging pattern led researchers to see a perfect transition from their fossils all the way up to comb jellies.

“It was probably one of the most exhilarating moments of my life,” said Dr Vinther. “We pulled out a zoology textbook and tried to wrap our head around the various differences and similarities, and then, bam! — here is another fossil that fills this gap.”

The study shows how comb jellies evolved from ancestors with an organic skeleton, which some still possessed and swam with during the Cambrian. Their combs evolved from tentacles in polyp-like ancestors that were attached to the seafloor. Their mouths then expanded into balloon-like spheres while their original body reduced in size so that the tentacles that used to surround the mouth now emerges from the back-end of the animal.

“With such body transformations, I think we have some of the answers to understand why comb jellies are so hard to figure out. It explains why they have lost so many genes and possess a morphology that we see in other animals,” added co-author Dr Luke Parry.

Until around 150 years ago, zoologists had considered comb jellies and cnidarians to be related. This theory was challenged more recently by new genetic information suggesting comb jellies could be a distant relative to all living animals below the very simple looking sponges.

The authors of this new study believe their findings make a strong case for repositioning the comb jelly back alongside corals, sea anemones and jellyfish.

Many Cambrian fossil animals discovered in China


This 21 March 2019 video is called Spectacular New Fossil Bonanza Captures Explosion Of Early Life.

One of the newly discovered animals, photo Science

From Science, 22 March 2019:

The Qingjiang biota—A Burgess Shale–type fossil Lagerstätte from the early Cambrian of South China

A treasure trove of Cambrian secrets

Animal life exploded in diversity and form during the Cambrian period about 500 million years ago. Fu et al. describe an early Cambrian fossil site in China that contains a variety of specimens, more than half of which are previously undescribed (see the Perspective by Daley). The site rivals previously described Cambrian sites, such as the Burgess Shale, and should help to elucidate biological innovation and diversification during this period.

Abstract

Burgess Shale–type fossil Lagerstätten provide the best evidence for deciphering the biotic patterns and magnitude of the Cambrian explosion. Here, we report a Lagerstätte from South China, the Qingjiang biota (~518 million years old), which is dominated by soft-bodied taxa from a distal shelf setting. The Qingjiang biota is distinguished by pristine carbonaceous preservation of labile organic features, a very high proportion of new taxa (~53%), and preliminary taxonomic diversity that suggests it could rival the Chengjiang and Burgess Shale biotas. Defining aspects of the Qingjiang biota include a high abundance of cnidarians, including both medusoid and polypoid forms; new taxa resembling extant kinorhynchs; and abundant larval or juvenile forms. This distinctive composition holds promise for providing insights into the evolution of Cambrian ecosystems across environmental gradients.

Reconstruction of seafloor life in China, 518 million years ago, by Science

So far, nearly 4500 animals of over 100 species have been found. Including small trilobites, early chordates and sponges. And the oldest kinorhynchs animals known so far.

See beautiful fossils from top Cambrian sites around the world: here.

Worms lived on Cambrian seafloor


This 2012 video from Canada says about itself:

Associate Curator Jean-Bernard Caron presents an overview of the fossil collection from the Burgess Shale, B.C., highlighting a number of specimens.

From the University of Saskatchewan in Canada:

500-million-year old worm ‘superhighway’ discovered in Canada

February 28, 2019\

Prehistoric worms populated the sea bed 500 million years ago — evidence that life was active in an environment thought uninhabitable until now, research by the University of Saskatchewan (USask) shows.

The sea bed in the deep ocean during the Cambrian period was thought to have been inhospitable to animal life because it lacked enough oxygen to sustain it.

But research published in the scientific journal Geology reveals the existence of fossilized worm tunnels dating back to the Cambrian period — 270 million years before the evolution of dinosaurs.

The discovery, by USask professor Brian Pratt, suggests that animal life in the sediment at that time was more widespread than previously thought.

The worm tunnels — borrows where worms lived and munched through the sediment — are invisible to the naked eye. But Pratt “had a hunch” and sliced the rocks and scanned them to see whether they revealed signs of ancient life.

The rocks came from an area in the remote Mackenzie Mountains of the Northwest Territories in Canada which Pratt found 35 years ago.

Pratt then digitally enhanced images of the rock surfaces so he could examine them more closely. Only then did the hidden ‘superhighway’ of burrows made by several different sizes and types of prehistoric worm emerge in the rock.

Some were barely a millimetre in size and others as large as a finger. The smaller ones were probably made by simple polychaetes — or bristle worms — but one of the large forms was a predator that attacked unsuspecting arthropods and surface-dwelling worms.

Pratt said he was “surprised” by the unexpected discovery.

“For the first time, we saw evidence of large populations of worms living in the sediment — which was thought to be barren,” he said. “There were cryptic worm tunnels — burrows — in the mud on the continental shelf 500 million years ago, and more animals reworking, or bioturbating, the sea bed than anyone ever thought.”

Pratt, a geologist and paleontologist and Fellow of the Geological Society of America, found the tunnels in sedimentary rocks that are similar to the Burgess Shale, a famous fossil-bearing deposit in the Canadian Rockies.

The discovery may prompt a rethink of the level of oxygenation in ancient oceans and continental shelves.

The Cambrian period saw an explosion of life on Earth in the oceans and the development of multi-cellular organisms including prehistoric worms, clams, snails and ancestors of crabs and lobsters. Previously the seas had been inhabited by simple, single-celled microbes and algae.

It has always been assumed that the creatures in the Burgess Shale — known for the richness of its fossils — had been preserved so immaculately because the lack of oxygen at the bottom of the sea stopped decay, and because no animals lived in the mud to eat the carcasses.

Pratt’s discovery, with co-author Julien Kimmig, now of the University of Kansas, shows there was enough oxygen to sustain various kinds of worms in the sea bed.

“Serendipity is a common aspect to my kind of research,” Pratt said. “I found these unusual rocks quite by accident all those years ago. On a hunch I prepared a bunch of samples and when I enhanced the images I was genuinely surprised by what I found,” he said.

“This has a lot of implications which will now need to be investigated, not just in Cambrian shales but in younger rocks as well. People should try the same technique to see if it reveals signs of life in their samples.”

The research was funded by the Natural Sciences and Engineering Research Council of Canada.