280 million-year-old fossil reveals origins of chimaeroid fishes
High-definition CT scans of the fossilized skull of a 280 million-year-old fish reveal the origin of chimaeras, a group of cartilaginous fish related to sharks. Analysis of the brain case of Dwykaselachus oosthuizeni, a shark-like fossil from South Africa, shows telltale structures of the brain, major cranial nerves, nostrils and inner ear belonging to modern-day chimaeras.
This discovery, published early online in Nature on Jan. 4, allows scientists to firmly anchor chimaeroids — the last major surviving vertebrate group to be properly situated on the tree of life — in evolutionary history, and sheds light on the early development of these fish as they diverged from their deep, shared ancestry with sharks.
“Chimaeroids belong somewhere close to the sharks and rays, but there’s always been uncertainty when you search deeper in time for their evolutionary branching point,” said Michael Coates, PhD, professor of organismal biology and anatomy at the University of Chicago, who led the study.
“Chimaeras are unusual throughout the long span of their fossil record,” Coates said. “Because of this, it’s been difficult to understand how they got to be the way they are in the first place. This discovery sheds new light not only on the early evolution of shark-like fishes, but also on jawed vertebrates as a whole.”
Chimaeras include about 50 living species, known in various parts of the world as ratfish, rabbit fish, ghost sharks, St. Joseph sharks or elephant sharks. They represent one of four fundamental divisions of modern vertebrate biodiversity. With large eyes and tooth plates adapted for grinding prey, these deep-water dwelling fish are far from the bloodthirsty killer sharks of Hollywood.
For more than 100 years, they have fascinated biologists. “There are few of the marine animals that on account of structure and relationships to other forms living and extinct have as great interest for zoologists and palaeontologists as the Chimaeroids,” wrote Harvard naturalist Samuel Garman in 1904. More than a century later, the relationship between chimaeras, the earliest sharks, and other early jawed fishes in the fossil record continues to puzzle paleontologists.
Chimaeras — named for their similarities to a mythical creature described by Homer as “lion-fronted and snake behind, a goat in the middle” — are unusual. Their anatomy comprises features reminiscent of sharks, ray-finned fishes and tetrapods, and their form is shaped by hardened bits of cartilage rather than bone. Because they are found in deep water, they were long considered rare. But as scientists gained the technology to explore more of the ocean, they are now known to be widespread, but their numbers remain uncertain.
After a 2014 study detailing their extremely slow-evolving genomes was published in Nature, interest in chimaeras blossomed. Of all living vertebrates with jaws, chimaeras seemed to offer the best promise of finding an archive of information about conditions close to the last common ancestor of humans and a Great White.
Like sharks, also reliant on cartilage, chimaeras rarely fossilize. The few known early chimaera fossils closely resemble their living descendants. Until now, the chimaeroid evolutionary record consisted mostly of isolated specimens of their characteristic hyper-mineralized tooth plates.
The Dwykaselachus fossil resolves this issue. It was originally discovered by amateur paleontologist and farmer Roy Oosthuizen when he split open a nodule of rock on his farm in South Africa in the 1980s. An initial description named it based on material visible at the broken surface of the nodule. It was carefully archived in the South African Museum in Cape Town, where its splendor awaited technology able to unwrap its long-shrouded secrets.
In 2013, when the University of the Witwatersrand Evolutionary Studies Institute obtained a micro CT scanner, Dr. Robert Gess, a South African Centre of Excellence in Palaeosciences partner and co-author of this study, began scanning Devonian shark fossils while he was based at the Rhodes University Geology Department. Coates encouraged him to investigate Dwykaselachus.
At the surface, Dwykaselachus appeared to be a symmoriid shark, a bizarre group of 300+ million-year-old sharks, known for their unusual dorsal fin spines, some resembling boom-like prongs and others surreal ironing boards.
CT scans showed that the Dwykaselachus skull was remarkably intact, one of a very few that had not been crushed during fossilization. The scans also provide an unprecedented view of the interior of the brain case.
“When I saw it for the first time, I was stunned,” Coates said. “The specimen is remarkable.”
The images, one reviewer commented, are “almost dripping with data.”
They show a series of telltale anatomical structures that mark the specimen as an early chimaera, not a shark. The braincase preserves details about the brain shape, the paths of major cranial nerves and the anatomy of the inner ear. All of which indicate that Dwyka belongs to modern-day chimaeras. The scans reveal clues about how these fish began to diverge from their common ancestry with sharks.
A large extinction of vertebrates at the end of the Devonian period, about 360 million years ago, gave rise to an explosion of cartilaginous fishes. Instead of what became modern-day sharks, Coates said, revelations from this study indicate that “much of this new biodiversity was, instead, early chimaeras.”
“We can now say that the first radiation of cartilaginous fishes after the end Devonian extinction was chimaeras, in abundance.” Coates said. “It’s the inverse of what we’ve got today, where sharks are far more common.”
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Mass strandings of marine mammals blamed on toxic algae: Clues unearthed in ancient whale graveyard
Mass strandings of whales have puzzled people since Aristotle. Modern-day strandings can be investigated and their causes, often human-related, identified. Events that happened millions of years ago, however, are far harder to analyze — frequently leaving their cause a mystery. A team of Smithsonian and Chilean scientists examined a large fossil site of ancient marine mammal skeletons in the Atacama Desert of Northern Chile — the first definitive example of repeated mass strandings of marine mammals in the fossil record. The site reflected four distinct strandings over time, indicating a repeated and similar cause: toxic algae. The team’s findings will be published Feb. 26 in the Proceedings of the Royal Society B.
The site was first discovered during an expansion project of the Pan-American Highway in 2010. The following year, paleontologists from the Smithsonian and Chile examined the fossils, dating 6-9 million years ago, and recorded what remained before the site was paved over.
The team documented the remains of 10 kinds of marine vertebrates from the site, named Cerro Ballena — Spanish for “whale hill.” In addition to the skeletons of the more than 40 large baleen whales that dominated the site, the team documented the remains of a species of sperm whale and a walrus-like whale, both of which are now extinct. They also found skeletons of billfishes, seals and aquatic sloths.
What intrigued the team most, however, was how the skeletons were arranged. The skeletons were preserved in four separate levels, pointing to a repeated and similar underlying cause. The skeletons’ orientation and condition indicated that the animals died at sea, prior to burial on a tidal flat.
Effects of Toxic Algae
Today, toxins from harmful algal blooms, such as red tides, are one of the prevalent causes for repeated mass strandings that include a wide variety of large marine animals.
“There are a few compelling modern examples that provide excellent analogs for the patterns we observed at Cerro Ballena — in particular, one case from the late 1980s when more than a dozen humpback whales washed ashore near Cape Cod, with no signs of trauma, but sickened by mackerel loaded with toxins from red tides,” said Nicholas Pyenson, paleontologist at the Smithsonian’s National Museum of Natural History and lead author of the research. “Harmful algal blooms in the modern world can strike a variety of marine mammals and large predatory fish. The key for us was its repetitive nature at Cerro Ballena: no other plausible explanation in the modern world would be recurring, except for toxic algae, which can recur if the conditions are right.”
Harmful algal blooms are common along the coasts of continents; they are enhanced by vital nutrients, such as iron, released during erosion and carried by rivers flowing into the ocean. Because the Andes of South America are iron-rich, the runoff that has occurred along the west coast of South America for more than 20 million years has long provided the ideal conditions for harmful algal blooms to form.
From their research, the scientists conclude that toxins generated by harmful algal blooms most likely poisoned many ocean-going vertebrates near Cerro Ballena in the late Miocene (5-11 million years ago) through ingestion of contaminated prey or inhalation, causing relatively rapid death at sea. Their carcasses then floated toward the coast, where they were washed into a tidal flat by waves. Once stranded on the tidal flat, the dead or dying animals were protected from marine scavengers, and there were no large-land scavengers in South America at this time. Eventually, the carcasses were buried by sand. Because there are four layers at Cerro Ballena, this pathway from sea to land occurred four different times during a period of 10,000 to 16,000 years in the same area.
“Cerro Ballena is the densest site for individual fossil whales and other extinct marine mammals in entire world, putting it on par with the La Brea Tar Pits or Dinosaur National Monument in the U.S.,” Pyenson said. “The site preserves marine predators that are familiar to modern eyes, like large whales and seals. However, it also preserves extinct and bizarre marine mammals, including walrus-like whales and aquatic sloths. In this way, the site is an amazing and rare snapshot of ancient marine ecosystems along the coast of South America.”
3-D Technology at Cerro Ballena
Because the site was soon to be covered by the Pan-American Highway, time was very limited for the researchers. A major solution came in the form of 3-D technology. Pyenson brought a team of Smithsonian 3-D imaging experts to Chile, who spent a week scanning the entire dig site.
Although all the fossils found from 2010 to 2013 have been moved to museums in the Chilean cities of Caldera and Santiago, the Smithsonian has archived the digital data, including the 3-D scans, from the site at cerroballena.si.edu. There, anyone can download or interact with 3-D models of the fossil whale skeletons, scan Google Earth maps of the excavation quarries, look at a vast collection of high-resolution field photos and videos or take 360-degree tours of the site.
The enormous wealth of fossils that the team examined represents only a fraction of the potential at Cerro Ballena, which remains unexcavated. The scientists conservatively estimate that the entire area preserves several hundred fossil marine mammal skeletons, awaiting discovery. Pyenson’s colleagues at the Universidad de Chile in Santiago are actively working to create a research station near the fossils of Cerro Ballena so that those that have been collected and those still covered by sediments can be protected for posterity.
Revision to rules for color in dinosaurs suggests connection between color and physiology
New research that revises the rules allowing scientists to decipher color in dinosaurs may also provide a tool for understanding the evolutionary emergence of flight and changes in dinosaur physiology prior to its origin.
In a survey comparing the hair, skin, fuzz and feathers of living terrestrial vertebrates and fossil specimens, a research team from The University of Texas at Austin, the University of Akron, the China University of Geosciences and four other Chinese institutions found evidence for evolutionary shifts in the rules that govern the relationship between color and the shape of pigment-containing organelles known as melanosomes, as reported in the Feb. 13 edition of Nature.
At the same time, the team unexpectedly discovered that ancient maniraptoran dinosaurs, paravians, and living mammals and birds uniquely shared the evolutionary development of diverse melanosome shapes and sizes. (Diversity in the shape and size of melanosomes allows scientists to decipher color.) The evolution of diverse melanosomes in these organisms raises the possibility that melanosome shape and size could yield insights into dinosaur physiology.
Melanosomes have been at the center of recent research that has led scientists to suggest the colors of ancient fossil specimens covered in fuzz or feathers.
Melanosomes contain melanin, the most common light-absorbing pigment found in animals. Examining the shape of melanosomes from fossil specimens, scientists have recently suggested the color of several ancient species, including the fuzzy first-discovered feathered dinosaur Sinosauropteryx, and feathered species like Microraptor and Anchiornis.
According to the new research, color-decoding works well for some species, but the color of others may be trickier than thought to reconstruct.
Comparing melanosomes of 181 extant specimens, 13 fossil specimens and all previously published data on melanosome diversity, the researchers found that living turtles, lizards and crocodiles, which are ectothermic (commonly known as cold-blooded), show much less diversity in the shape of melanosomes than birds and mammals, which are endothermic (warm-blooded, with higher metabolic rates).
The limited diversity in melanosome shape among living ectotherms shows little correlation to color. The same holds true for fossil archosaur specimens with fuzzy coverings scientists have described as “protofeathers” or “pycnofibers.” In these specimens, melanosome shape is restricted to spherical forms like those in modern reptiles, throwing doubt on the ability to decipher the color of these specimens from fossil melanosomes.
In contrast, in the dinosaur lineage leading to birds, the researchers found an explosion in the diversity of melanosome shape and size that appears to correlate to an explosion of color within these groups. The shift in diversity took place abruptly, near the origin of pinnate feathers in maniraptoran dinosaurs.
“This points to a profound change at a pretty discrete point,” says author Julia Clarke of The University of Texas at Austin’s Jackson School of Geosciences. “We’re seeing an explosion of melanosome diversity right before the origin of flight associated with the origin of feathers.”
What surprised the researchers was a similarity in the pattern of melanosome diversity among ancient maniraptoran dinosaurs, paravians, and living mammals and birds.
“Only in living, warm-blooded vertebrates that independently evolved higher metabolic rates do we see the melanosome diversity we also see in feathered dinosaurs,” said co-author Matthew Shawkey of The University of Akron.
Many of the genes involved in the melanin color system are also involved in other core processes such as food intake, the stress axis, and reproductive behaviors. Because of this, note the researchers, it is possible that the evolution of diverse melanosome shapes is linked to larger changes in energetics and physiology.
Melanosome shape could end up offering a new tool for studying endothermy in fossil specimens, a notoriously challenging subject for paleontologists.
Because the explosion of diversity in melanosomes appears to have taken place right at the origin of pinnate feathers, the change may indicate that a key shift in dinosaurian physiology occurred prior to the origin of flight.
“We are far from understanding the exact nature of the shift that may have occurred,” says Clarke. “But if changes in genes involved in both coloration and other aspects of physiology explain the pattern we see, these precede flight and arise close to the origin of feathers.”
It is possible, notes Clarke, that a diversity in melanosome shape (and correlated color changes) resulted from an increased evolutionary role for signaling and sexual selection that had a carryover effect on physiology, or that a change in physiology closely preceded changes in color patterning. At this point, she stresses, both ideas are speculative.
“What is interesting is that trying to get at color in extinct animals may have just started to give us some insights into changes in the physiology of dinosaurs.”
X-Rays Reveal New Picture of ‘Dinobird’ Plumage Patterns
June 11, 2013 — The first complete chemical analysis of feathers from Archaeopteryx, a famous fossil linking dinosaurs and birds, reveals that the feathers of this early bird were patterned – light in colour, with a dark edge and tip to the feather - rather than all black, as previously thought.
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The findings came from X-ray experiments undertaken by a team from the University of Manchester, working with colleagues at the US Department of Energy’s (DOE) SLAC National Accelerator Laboratory. The scientists were able to find chemical traces of the original ‘dinobird’ and dilute traces of plumage pigments in the 150 million-year-old fossil.
“This is a big leap forward in our understanding of the evolution of plumage and also the preservation of feathers,” said Dr Phil Manning, a palaeontologist at The University of Manchester and lead author of the report in the June 13 issue of the Journal of Analytical Atomic Spectrometry (Royal Society of Chemistry).
Only 11 specimens of Archaeopteryx have been found, the first one consisting of a single feather. Until a few years ago, researchers thought minerals would have replaced all the bones and tissues of the original animal during fossilisation, leaving no chemical traces behind, but two recently developed methods have turned up more information about the dinobird and its plumage.
The first is the discovery of melanosomes – microscopic ‘biological paint pot’ structures in which pigment was once made, but are still visible in some rare fossil feathers. A team led by researchers at Brown University announced last year that an analysis of melanosomes in the single Archaeopteryx feather indicated it was black. They identified the feather as a covert – a type of feather that covers the primary and secondary wing feathers – and said its heavy pigmentation may have strengthened it against the wear and tear of flight, as it does in modern birds.
However, that study examined melanosomes from just a few locations in the fossilised feather, explained SLAC’s Dr Uwe Bergmann: “It’s actually quite a beautiful paper,” he said, “but they took just tiny samples of the feather, not the whole thing.”
The second is a method that Drs Bergmann, Manning and Roy Wogelius have developed for rapidly scanning entire fossils and analysing their chemistry with an X-ray beam at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) in the USA.
Over the past three years, the team used this method to discover chemical traces locked in the dinobird’s bones, feathers and in the surrounding rock, as well as pigments from the fossilised feathers of two specimens of another species of early bird. This allowed the team to recreate the plumage pattern of an extinct bird for the very first time.
In the latest study, the team scanned the entire fossil of the first Archaeopteryx feather with the SSRL X-ray beam. They found trace-metals that have been shown to be associated with pigment and organic sulphur compounds that could only have come from the animal’s original feathers.
“The fact that these compounds have been preserved in-place for 150 million years is extraordinary,” said Dr Manning said. “Together, these chemical traces show that the feather was light in colour with areas of darker pigment along one edge and on the tip.
“Scans of a second fossilised Archaeopteryx, known as the Berlin counterpart, also show that the trace-metal inventory supported the same plumage pigmentation pattern.”
Co-author Dr Roy Wogelius, also based in Manchester’s School of Earth, Atmospheric and Environmental Sciences, said: “This work refines our understanding of pigment patterning in perhaps the most important known fossil. Our technique shows that complex patterns were present even at the very earliest steps in the evolution of birds.”
The team’s results show that the chemical analysis provided by synchrotron X-ray sources, such as SSRL, is crucial when studying the fossil remains of such pivotal species. The plumage patterns can begin to help scientists review their possible role in the courtship, reproduction and evolution of birds and possibly shed new light on their health, eating habits and environment.
Dr Manning added: “It is remarkable that x-rays brighter than a million suns can shed new light on our understanding of the processes that have locked elements in place for such vast periods of time. Ultimately, this research might help inform scientists on the mechanisms acting during long-term burial, from animal remains to hazardous waste. The fossil record has potential to provide the experimental hindsight required in such studies.”
The research team included scientists from The University of Manchester (UK); SLAC (USA); the Black Hills Institute of Geological Research in South Dakota (USA); and the Museum für Naturkunde in Berlin (Germany), which provided the stunning Archaeopteryx fossils for analysis.
Dinosaur Egg Study Supports Evolutionary Link Between Birds and Dinosaurs: How Troodon Likely Hatched Its Young
A small, bird-like North American dinosaur incubated its eggs in a similar way to brooding birds — bolstering the evolutionary link between birds and dinosaurs, researchers at the University of Calgary and Montana State University study have found.
Among the many mysteries paleontologists have tried to uncover is how dinosaurs hatched their young. Was it in eggs completely buried in nest materials, like crocodiles? Or was it in eggs in open or non-covered nests, like brooding birds?
Using egg clutches found in Alberta and Montana, researchers Darla Zelenitsky at the University of Calgary and David Varricchio at Montana State University closely examined the shells of fossil eggs from a small meat-eating dinosaur called Troodon.
In a finding published in the spring issue of Paleobiology, they concluded that this specific dinosaur species, which was known to lay its eggs almost vertically, would have only buried the egg bottoms in mud.
“Based on our calculations, the eggshells of Troodon were very similar to those of brooding birds, which tells us that this dinosaur did not completely bury its eggs in nesting materials like crocodiles do,” says study co-author Zelenitsky, assistant professor of geoscience.
“Both the eggs and the surrounding sediments indicate only partial burial; thus an adult would have directly contacted the exposed parts of the eggs during incubation,” says lead author Varricchio, associate professor of paleontology.
Varricchio says while the nesting style for Troodon is unusual, “there are similarities with a peculiar nester among birds called the Egyptian Plover that broods its eggs while they’re partially buried in sandy substrate of the nest.”
Paleontologists have always struggled to answer the question of how dinosaurs incubated their eggs, because of the scarcity of evidence for incubation behaviours.
As dinosaurs’ closest living relatives, crocodiles and birds offer some insights.
Scientists know that crocodiles and birds that completely bury their eggs for hatching have eggs with many pores or holes in the eggshell, to allow for respiration.
This is unlike brooding birds which don’t bury their eggs; consequently, their eggs have far fewer pores.
The researchers counted and measured the pores in the shells of Troodon eggs to assess how water vapour would have been conducted through the shell compared with eggs from contemporary crocodiles, mound-nesting birds and brooding birds.
They are optimistic their methods can be applied to other dinosaur species’ fossil eggs to show how they may have been incubated.
“For now, this particular study helps substantiate that some bird-like nesting behaviors evolved in meat-eating dinosaurs prior to the origin of birds. It also adds to the growing body of evidence that shows a close evolutionary relationship between birds and dinosaurs,” Zelenitsky says.
New Evidence Dinosaurs Were Strong Swimmers
Apr. 8, 2013 — A University of Alberta researcher has identified some of the strongest evidence ever found that dinosaurs could paddle long distances.
Working together with an international research team, U of A graduate student Scott Persons examined unusual claw marks left on a river bottom in China that is known to have been a major travel-way for dinosaurs.
Alongside easily identified fossilized footprints of many Cretaceous era animals including giant long neck dinosaur’s researchers found a series of claw marks that Persons says indicates a coordinated, left-right, left-right progression.
“What we have are scratches left by the tips of a two-legged dinosaur’s feet,” said Persons. “The dinosaur’s claw marks show it was swimming along in this river and just its tippy toes were touching bottom.”
The claw marks cover a distance of 15 meters which the researchers say is evidence of a dinosaur’s ability to swim with coordinated leg movements. The tracks were made by carnivorous theropod dinosaur that is estimated to have stood roughly 1 meter at the hip.
Fossilized rippling and evidence of mud cracks indicate that over 100 million years ago the river, in what is now China’s Szechuan Province, went through dry and wet cycles. The river bed, which Persons describes as a “dinosaur super-highway” has yielded plenty of full foot prints of other theropods and gigantic four-legged sauropods.
With just claw scratches on the river bottom to go with, Persons says the exact identity of the paddling dinosaur can’t be determined, but he suspects it could have been an early tyrannosaur or a Sinocalliopteryx. Both species of predators were known to have been in that area of China.
Persons is a U of A, PhD candidate and co-author of the research. It was published April 8 in the journal Chinese Science Bulletin.
Light Shed on Ancient Origin of Life
Mar. 6, 2013 — University of Georgia researchers discovered important genetic clues about the history of microorganisms called archaea and the origins of life itself in the first ever study of its kind. Results of their study shed light on one of Earth’s oldest life forms.
“Archaea are an ancient form of microorganisms, so everything we can learn about them could help us to answer questions about the origin of life,” said William Whitman, a microbiology professor in the Franklin College of Arts and Sciences and co-author on the paper.
Felipe Sarmiento, lead author and doctoral student in the microbiology department, surveyed 1,779 genes found in the genome of Methanococcus maripaludis, aquatic archaea commonly found in sea marshes, to determine if they were essential or not and learn more about their functions. He found that roughly 30 percent, or 526 genes, were essential. We now know which genes are driving the most important functions of the cell. The results of the study were published March 4 in the PNAS Early Edition and were performed with Jan Mrázek, an associate professor in the department of microbiology and the UGA Institute of Bioinformatics.
Although archaea are relatively simple organisms, the genetic systems they use to build cellular life are similar to those of more complicated eukaryotic cells found in complex organisms including animals and plants. For this reason, many scientists believe that eukaryotes evolved from ancient archaea.
These genetic systems are what allow information coded on DNA to build life.
“DNA by itself is a rock,” Whitman said. “You need all these other systems to make the DNA become a living cell.”
Because DNA is so fundamental to the modern cell, DNA synthesis has long been thought to be one of the most conserved processes in living organisms.
“It was a surprise when this study found that the system for making DNA was unique to the archaea,” Whitman said. “Learning that it can change in the archaea suggest that ability to make DNA formed late in the evolution of life. Possibly, there may be unrecognized differences in DNA biosynthesis the eukaryotes or bacteria as well.”
Other essential genes in these archaea are necessary for methane production. Methanogensis, or the process of making methane gas, is how these microorganisms make energy for life.
“Humans burn glucose and reduce oxygen to water, these guys burn hydrogen gas and reduce CO2 to methane,” Whitman explained.
Methanogenesis requires six vitamins not commonly found in other organisms. Understanding how these vitamins are made and how they are involved in the process of changing carbon dioxide to methane sheds light on developing new and better processes for methane production for fuel.
“This was a general investigation, but there are many questions it can answer, like possibly making methane better or more efficiently,” Whitman said.
The study yielded many other important results.
“We found 121 proteins that are essential for this organism that we know nothing about,” Sarmiento said. “This finding asks questions about their functions and the specific roles that they are playing.”
“We are starting to get some insights about how this organism was actually formed,” Sarmiento said. “There is a lot of information and it is interesting because it gives insights into a complete domain of life.”
Ancient Fossilized Sea Creatures Yield Oldest Biomolecules Isolated Directly from a Fossil
Feb. 18, 2013 — Though scientists have long believed that complex organic molecules couldn’t survive fossilization, some 350-million-year-old remains of aquatic sea creatures uncovered in Ohio, Indiana, and Iowa have challenged that assumption.
The spindly animals with feathery arms — called crinoids, but better known today by the plant-like name “sea lily” — appear to have been buried alive in storms during the Carboniferous Period, when North America was covered with vast inland seas. Buried quickly and isolated from the water above by layers of fine-grained sediment, their porous skeletons gradually filled with minerals, but some of the pores containing organic molecules were sealed intact.
That’s the conclusion of Ohio State University geologists, who extracted the molecules directly from individual crinoid fossils in the laboratory, and determined that different species of crinoid contained different molecules. The results will appear in the March issue of the journal Geology.
William Ausich, professor in the School of Earth Sciences at Ohio State and co-author of the paper, explained why the organic molecules are special.
“There are lots of fragmented biological molecules — we call them biomarkers — scattered in the rock everywhere. They’re the remains of ancient plant and animal life, all broken up and mixed together,” he said. “But this is the oldest example where anyone has found biomarkers inside a particular complete fossil. We can say with confidence that these organic molecules came from the individual animals whose remains we tested.”
The molecules appear to be aromatic compounds called quinones, which are found in modern crinoids and other animals. Quinones sometimes function as pigments or as toxins to discourage predators.
Lead author Christina O’Malley, who completed this work to earn her doctoral degree, first began the study when she noticed something strange about some crinoids that had perished side by side and become preserved in the same piece of rock: the different species were preserved in different colors.
In one rock sample used in the study, one crinoid species appears a light bluish-gray, while another appears dark gray and yet another more of a creamy white. All stand out from the color of the rock they were buried in. The researchers have since found similar fossil deposits from around the Midwest.
“People noticed the color differences 100 years ago, but no one ever investigated it,” O’Malley said. “The analytical tools were not available to do this kind of work as they are today.”
O’Malley isolated the molecules by grinding up small bits of fossil and dissolving them into a solution. Then she injected a tiny sample of the solution into a machine called a gas chromatograph mass spectrometer. The machine vaporized the solution so that a magnet could separate individual molecules based on electric charge and mass. Computer software identified the molecules as similar to quinones.
Then, with study co-author and Ohio State geochemist Yu-Ping Chin, she compared the organic molecules from the fossils with the molecules that are common in living crinoids today. Just as the researchers suspected, quinone-like molecules occur in both living crinoids and their fossilized ancestors.
Though different colored fossils contained different quinones, the researchers cautioned that there’s no way to tell whether the quinones functioned as pigments, or that the preserved colors as they appear today were similar to the colors that the crinoids had in life.
Part of why the crinoids were so well preserved has to do with the structure of their skeletons, the researchers said. Like sand dollars, crinoids have skin on top of a hard calcite shell. In the case of crinoids, their long bodies are made up of thousands of stacked calcite rings, and each ring is a single large calcite crystal that contains pores filled with living tissue. When a crinoid dies, the tissue will start to decay, but calcite will precipitate into the pores, and calcite is stable over geologic time. Thus, organic matter may become sealed whole within the rock.
“We think that rock fills in the skeleton according to how the crystals are oriented. So it’s possible to find large crystals filled in such a way that they have organic matter still trapped inside,” Ausich said.
The location of the fossils was also key to their preservation. In the flat American Midwest, the rocks weren’t pushed up into mountain chains or heated by volcanism, so from the Ohio State geologists’ perspective, they are pristine.
Their next challenge is to identify the exact type of quinone molecules they found, and determine how much information about individual species can be gleaned from them.
“These molecules are not DNA, and they’ll never be as good as DNA as a means to define evolutionary relationships, but they could still be useful,” Ausich said. “We suspect that there’s some kind of biological signal there — we just need to figure out how specific it is before we can use it as a means to track different species.”
This research was sponsored by the National Science Foundation and the Geological Society of America.
Ancient Insects Shed Light On Biodiversity
Simon Fraser University evolutionary biologists Bruce Archibald and Rolf Mathewes, and Brandon University biologist David Greenwood, have discovered that modern tropical mountains’ diversity patterns extended up into Canada about 50 million years ago.
Their findings confirm an influential theory about change in modern species diversity across mountains, and provide evidence that global biodiversity was greater in ancient times than now. The scientific journal Palaeogeography, Palaeoclimatology, Palaeoecology has published their research.
About 45 years ago, an evolutionary biologist at the University of Pennsylvania theorized that change in species from site to site across mountain ranges in the tropics should be greater than in temperate latitudes.
Daniel Janzen reasoned that the great difference between summer and winter in temperate latitudes (high seasonality) offers a wide window to migrate across mountainous regions. The small difference in the tropics (low seasonality) allows a very narrow opportunity, annually. Consequently, communities across tropical mountains should have fewer of the same species. Many studies examining modern communities support this theory.
Archibald, Mathewes and Greenwood realized that fossil beds across a thousand kilometres of the ancient mountains of British Columbia and Washington provided a unique lens through which to deepen evaluation of this theory.
Fifty million years ago, when these fossil beds were laid down, the world had low seasonality outside of the tropics, right to the poles. Because of this, if Janzen’s theory is right, the pattern of biodiversity that he described in modern tropical mountains should have extended well into higher latitudes.
“We found that insect species changed greatly across British Columbia’s and Washington State’s ancient mountain ranges, like in the modern tropics,” Archibald says, “exactly as Janzen’s seasonality hypothesis predicted.
This implies that it’s the particular seasonality now found in the modern tropics, not where that climate is situated globally, that affects this biodiversity pattern.” He adds: “Sometimes it helps to look to the ancient past to better understand how things work today.”
The findings also bolster the idea that ancient Earth was a much more diverse world than now with many more species.
America’s Ancient Hurricane Belt and the U.S.-Canada Equator
ScienceDaily (Nov. 15, 2012) — The recent storms that have battered settlements on the east coast of America may have been much more frequent in the region 450 million years ago, according to scientists.
New research pinpointing the positions of the Equator and the landmasses of the USA, Canada and Greenland, during the Ordovician Period 450 million years ago, indicates that the equator ran down the western side of North America with a hurricane belt to the east.
The hurricane belt would have affected an area covering modern day New York State, New Jersey and most of the eastern seaboard of the USA.
An international research team led by Durham University used the distribution of fossils and sediments to map the line of the Ordovician Equator down to southern California.
The study, published in the journal Geology,is the first to accurately locate and map the ancient Equator and adjacent tropical zones. Previous studies had fuelled controversy about the precise location of the ancient equator. The researchers say the new results show how fossils and sediments can accurately track equatorial change and continental shifts over time.
Co-lead author Professor David Harper, Department of Earth Sciences, said: “The equator, equatorial zones and hurricane belts were in quite different places in the Ordovician. It is likely that the weather forecast would have featured frequent hurricane-force storms in New York and other eastern states, and warmer, more tropical weather from Seattle to California.”
Since Polar Regions existed 450 million years ago, the scientists believe that there would have been similar climate belts to those of today.
The research team from Durham University and universities in Canada, Denmark and the USA, discovered a belt of undisturbed fossils and sediments -deposits of shellfish- more than 6000 km long stretching from the south-western United States to North Greenland. The belt also lacks typical storm-related sedimentary features where the deposits are disturbed by bad weather. The researchers say that this shows that the Late Ordovician equatorial zone, like the equatorial zone today, had few hurricane-grade storms.
In contrast, sedimentary deposits recorded on either side of the belt provide evidence of disturbance by severe storms. Hurricanes tend to form in the areas immediately outside of equatorial zones where temperatures of at least 260C combine with Earth’s rotation to create storms. The researchers believe that hurricane belts would probably have existed on either side of the ancient equator, within the tropics.
The position of the equatorial belt, defined by undisturbed fossil accumulations and sediments, is coincident with the Late Ordovician equator interpreted from magnetic records (taken from rocks of a similar age from the region). This provides both a precise equatorial location and confirms that Earth’s magnetic field operated much in the same way as it does today.
The scientists pieced together the giant jigsaw map using the evidence of the disturbed and undisturbed sedimentary belts together with burrows and shells. Using the findings from these multiple sites, they were able to see that North America sat on either side of the Equator.
Co-author Christian Rasmussen, University of Copenhagen, said: “The layers of the earth build up over time and are commonly exposed by plate tectonics. We are able to use these ancient rocks and their fossils as evidence of the past to create an accurate map of the Ordovician globe.”
Professor Harper added: “The findings show that we had the same climate belts of today and we can see where North America was located 450 million years ago, essentially on the Equator.”
“While the Equator has remained in approximately the same place over time, the landmasses have shifted dramatically over time through tectonic movements. The undisturbed fossil belt helps to locate the exact position of the ancient Laurentian landmass, now known as North America.”
The study is funded by the Danish Council for Independent Research.