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.
First discovery of dinosaur fossils in Malaysia
A team of palaeontology researchers from the Department of Geology, Faculty of Science, University of Malaya and Japanese universities (Waseda University and Kumamoto University) has found dinosaur fossil teeth in the rural interiors of Pahang — the first known discovery of dinosaur remains in Malaysia.
“Acting as a team leader, and one of the collaborators, Professor Ren Hirayama from Waseda University (Tokyo), a specialist in reptile palaeontology, identified that one of the teeth, Sample UM10575, belongs to a spinosaurid dinosaur (known as a carnivorous “fish-eating” dinosaur),” he added.
UM10575 is about 23mm long and 10mm wide. It develops fairly distinct carinae (front and rear edges) with serrations, typical to a tooth of a theropod (carnivorous dinosaur). Well-marked coarse ridges are developed on the surface of the tooth, and the surface bears micro-ornament (very fine sculptures); these characterise a spinosaurid tooth.
The new fossils were found from sedimentary rock strata of late Mesozoic age, most likely Cretaceous (ca. 145-75 million years ago). In the interior of Peninsular Malaysia, Jurassic¬-Cretaceous sediments are known to be widely distributed, so that the team researchers have targeted a potential dinosaur deposit there since.
It is expected that large deposits of dinosaur fossils still remain in Malaysia. We currently continue further research and hope to conduct more extensive field investigations that may disclose more significant finds.
Alongside making the public announcement of this discovery, it is urgent to take measures for the protection and conservation of the present fossil site (and to make it accessible only to the qualified researchers). Since the site is in the open area, it is concerned that, once the public is aware, some destruction due to lawless excavations by private fossil collectors and/or robbers may happen, as has happened, for example, in Thailand, Laos, and Mongolia.
It is also hoped that the current discovery can lead to development of palaeontology study in the country and to eventually establish a Malaysian dinosaur museum in a near future.
Chronology of geological events prior to the great extinction 66 million years ago
Research at the Faculty of Science and Technology of the University of the Basque Country (UPV/EHU), entitled ‘Detailed Correlation and Orbital Control of succession during the Upper Maastrichtian in the Basque-Cantabrian Basin’ and focusing on the last 3 million years of the Cretaceous period, managed to detail exactly the chronology of the climatic, magnetic and biological events prior to the great extinction of 66 million years ago (Ma.), which includes the disappearance of almost all dinosaurs (except birds).
The traditional method for establishing absolute chronological and geological events has been using radiometric dating methods, based on the decomposition of radioactive isotopes. This method, however, is only applicable with the intervals such isotopes have, so the ages of certain zones can only be estimated through interpolation.
As the title of the research suggests, the method applied by this research team was based on a different principle, concretely on what is known as orbital control, which analyses gravitational interactions between the Earth, the Moon, the Sun and the planets of the Solar System (principally Jupiter). These interactions produce periodic variations of the terrestrial orbit, known as Milankovitch cycles, in honour of the Serbian astrophysicist who discovered them. It is thus known that the terrestrial orbit varies with intervals of one hundred thousand and four hundred thousand years; the inclination or obliquity of Earth’s axis every forty thousand years; and the orientation of this axis in relation to the sun approximately every twenty thousand years.
“It has been shown that such orbital variations influence, to a greater or lesser degree, the Earth’s climate, due mainly to differences in solar radiation received by the planet. The variations of the terrestrial orbit, for example, also controlled the duration of the glacial periods during the Quaternary (from 2.6 Ma until today),” explained Victoriano Pujalte, Professor of Geology of the Faculty of Science and Technology at the UPV/EHU and co-author of the research.
Sopelana, Zumaia and Hendaia
The research focused on locating the effects that these astronomical cycles have had on the layers analysed, a Flysch-type succession (rock sequences of a sedimentary origin made up of alternating layers of hard calcareous rock with other, softer loams) accumulated on a deep-lying sea basin — the Basque Basin — between 69 and 66 Ma, and which today is exposed to the naked eye in cliffs at Sopelana (Bizkaia province), Zumaia (province of Gipuzkoa) and Hendaia (Lapurdi). Using the “Fourier analysis” (a mathematical tool to analyse periodic functions), it has been possible to identify cycles of 400,000, 100,000 and 20,000 years, represented “by successive alternations of a loamy layer and another calcareous one,” known as “pairs,” of which 125 have been identified and enumerated. This has enabled narrowing the layers of the emerging successions to stages of twenty thousand years. “On a human scale twenty thousand years may seem a long time. On a geological scale, however, it represents spectacular precision,” explained Mr. Pujalte.
Geology is a “historical science” and, as such, any advance enabling greater precision in the chronology of events represents significant progress. “This is what the purpose of our work has been: to establish the chronology, approximately, of the past three million years of this Cretaceous period, and which in future research will enable establishing the geological and oceanographic phenomena of such an interval with precision,” pointed out the Professor of Geology at the UPV/EHU Faculty of Science and Technology.
Ancient reptile birth preserved in fossil: Ichthyosaur fossil may show oldest live reptilian birth
An ichthyosaur fossil may show the earliest live birth from an ancient Mesozoic marine reptile, according to a study published February 12, 2014 in PLOS ONE by Ryosuke Motani from the University of California, Davis, and colleagues.
Ichthyosaurs were giant marine reptiles that evolved from land reptiles and moved to the water. Scientists report a new fossil specimen that belongs to Chaohusaurus (Reptilia, Ichthyopterygia), the oldest of Mesozoic marine reptiles that lived approximately 248 million years ago. The partial skeleton was recovered in China and may show a live birth. The maternal skeleton was associated with three embryos and neonates: one inside the mother, another exiting the pelvis-with half the body still inside the mother-and the third outside of the mother. The headfirst birth posture of the second embryo indicates that live births in ichthyosaurs may have taken place on land, instead of in the water, as some studies have previously suggested.
The new specimen may contain the oldest fossil embryos of Mesozoic marine reptile, about 10 million years older than those indicated on previous records. The authors also suggest that live births in land reptiles may have appeared much earlier than previously thought.
Dr. Motani added, “The study reports the oldest vertebrate fossil to capture the ‘moment’ of live-birth, with a baby emerging from the pelvis of its mother. The 248-million-year old fossil of an ichthyosaur suggests that live-bearing evolved on land and not in the sea.”
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.”
Fossils abound: ‘Epic’ new Burgess Shale site in Canada’s Kootenay National Park
Yoho National Park’s 505-million-year-old Burgess Shale — home to some of the planet’s earliest animals, including a very primitive human relative — is one of the world’s most important fossil sites. Now, more than a century after its discovery, a compelling sequel has been unearthed: 42 kilometres away in Kootenay National Park, a new Burgess Shale fossil bed has been located that appears to equal the importance of the original discovery, and may one day even surpass it.
A paper published today in the scientific journal Nature Communications describes Kootenay National Park’s new ‘Marble Canyon’ fossil beds for the first time. The authors suggest that the area and its extraordinary fossils will greatly further our understanding of the sudden explosion of animal life during the Cambrian Period.
The find was made in the summer of 2012 by a team from the Royal Ontario Museum (ROM, Jean-Bernard Caron), Pomona College (Robert Gaines), the University of Toronto (Jean-Bernard Caron, Cédric Aria), the University of Saskatchewan (Gabriela Mángano) and Uppsala University (Michael Streng).
“This new discovery is an epic sequel to a research story that began at the turn of the previous century. There is no doubt in my mind that this new material will significantly increase our understanding of early animal evolution,” said Dr. Jean-Bernard Caron, Curator of Invertebrate Paleontology at the ROM, Associate Professor at the University of Toronto and the study’s lead author. “The rate at which we are finding animals — many of which are new — is astonishing, and there is a high possibility that we’ll eventually find more species here than at the original Yoho National Park site, and potentially more than from anywhere else in the world.”
In a short 15-day field season, the researchers collected thousands of specimens representing more than 50 species, several of which were new to science. Incredibly, many of the species previously known from Yoho are better preserved in Kootenay, retaining very fine, never-before-seen anatomical details that are important for understanding the shape of the animal ‘family tree.’
The new site parallels Yoho in its spectacular richness of arthropods, a group that today represents more than 80% of all living animals, including insects, spiders and lobsters.
Another curious similarity between Marble Canyon and the original discovery is that both sites would still be buried today if not for the dedicated exploratory work of scientists.
In 1909, world-renowned paleontologist Charles Walcott spent a summer exploring Yoho National Park’s mountainous topography in search of hidden treasures, only to stumble upon what he would later name the Burgess Shale on the final day of his field season on August 29. Similarly, in 2012, a ROM field expedition led by Caron spent part of their summer in search of the next big paleontological discovery.
“We were already aware of the presence of some Burgess Shale fossils in Kootenay National Park,” said Dr. Robert Gaines, a geologist from Pomona College, who along with Caron and colleagues had spent August 2008 at a much smaller fossil deposit in the park located near Stanley Glacier. “We had a hunch that if we followed the formation along the mountain topography into new areas with the right rock types, maybe, just maybe, we would get lucky — though we never in our wildest dreams thought we’d track down a motherload like this.”
Just like Walcott a century before, a hunch led Caron and his team to a talus slope high in the Canadian Rockies. Along this rocky slope they found a startling variety of fossils that immediately caught their attention. The researchers then pinpointed the source of the fossils to higher up on the slopes and began to excavate the fossils layer-by-layer.
“It didn’t take us very long at all to realize that we had dug up something special,” added Gaines. “To me, the Burgess Shale is a grand tale in every way imaginable, and we are incredibly proud to be part of this new chapter and to keep the story alive and thriving in everyone’s imagination.”
“We are very excited to go back to the field this summer,” said Caron. “One of our main goals is to discover more new species.”
The new fossil site is protected by Parks Canada, with the exact location remaining confidential to protect its integrity. Future visitor opportunities have not been ruled out.
Burgess Shale facts:
• This new finding is the latest in a recent string of Burgess Shale discoveries, including confirmation that Pikaia, found only in Yoho National Park, is the most primitive known vertebrate and therefore the ancestor of all descendant vertebrates, including humans.
• In over 100 years of research, approximately 200 animal species have been identified at the original Burgess Shale discovery in Yoho National Park in over 600 field days. In just 15 days of field collecting, 50 animal species have already been unearthed at the new Kootenay National Park site.
• Some species found at the new Kootenay site are also found in China’s famous Chengjiang fossil beds, which are 10 million years older. This contributes to the pool of evidence suggesting that the local and worldwide distribution of Cambrian animals, as well as their longevity, might have been underestimated.
• The original Burgess Shale site in Yoho National Park was recognized in 1980 as one of Canada’s first UNESCO World Heritage Sites. Now protected under the larger Rocky Mountain Parks UNESCO World Heritage Site, the Burgess Shale attracts thousands of visitors to Yoho National Park each year for guided hikes to the restricted fossil beds from July to September. Both Parks Canada and the Burgess Shale Geoscience Foundation lead hikes to the fossils.
• All the Burgess Shale fossil specimens in the Marble Canyon area of were collected under a Parks Canada Research and Collection permit and are held in trust for Parks Canada at the Royal Ontario Museum in Toronto.
Giant mass extinction quicker than previously thought: End-Permian extinction happened in 60,000 years
The largest mass extinction in the history of animal life occurred some 252 million years ago, wiping out more than 96 percent of marine species and 70 percent of life on land — including the largest insects known to have inhabited Earth. Multiple theories have aimed to explain the cause of what’s now known as the end-Permian extinction, including an asteroid impact, massive volcanic eruptions, or a cataclysmic cascade of environmental events. But pinpointing the cause of the extinction requires better measurements of how long the extinction period lasted.
Now researchers at MIT have determined that the end-Permian extinction occurred over 60,000 years, give or take 48,000 years — practically instantaneous, from a geologic perspective. The new timescale is based on more precise dating techniques, and indicates that the most severe extinction in history may have happened more than 10 times faster than scientists had previously thought.
“We’ve got the extinction nailed in absolute time and duration,” says Sam Bowring, the Robert R. Shrock Professor of Earth and Planetary Sciences at MIT. “How do you kill 96 percent of everything that lived in the oceans in tens of thousands of years? It could be that an exceptional extinction requires an exceptional explanation.”
In addition to establishing the extinction’s duration, Bowring, graduate student Seth Burgess, and a colleague from the Nanjing Institute of Geology and Paleontology also found that, 10,000 years before the die-off, the oceans experienced a pulse of light carbon, which likely reflects a massive addition of carbon dioxide to the atmosphere. This dramatic change may have led to widespread ocean acidification and increased sea temperatures by 10 degrees Celsius or more, killing the majority of sea life.
But what originally triggered the spike in carbon dioxide? The leading theory among geologists and paleontologists has to do with widespread, long-lasting volcanic eruptions from the Siberian Traps, a region of Russia whose steplike hills are a result of repeated eruptions of magma. To determine whether eruptions from the Siberian Traps triggered a massive increase in oceanic carbon dioxide, Burgess and Bowring are using similar dating techniques to establish a timescale for the Permian period’s volcanic eruptions that are estimated to have covered over five million cubic kilometers.
“It is clear that whatever triggered extinction must have acted very quickly,” says Burgess, the lead author of a paper that reports the results in this week’s Proceedings of the National Academy of Sciences, “fast enough to destabilize the biosphere before the majority of plant and animal life had time to adapt in an effort to survive.”
Pinning dates on an extinction
In 2006, Bowring and his students made a trip to Meishan, China, a region whose rock formations bear evidence of the end-Permian extinction; geochronologists and paleontologists have flocked to the area to look for clues in its layers of sedimentary rock. In particular, scientists have focused on a section of rock that is thought to delineate the end of the Permian, and the beginning of the Triassic, based on evidence such as the number of fossils found in surrounding rock layers.
Bowring sampled rocks from this area, as well as from nearby alternating layers of volcanic ash beds and fossil-bearing rocks. After analyzing the rocks in the lab, his team reported in 2011 that the end-Permian likely lasted less than 200,000 years. However, this timeframe still wasn’t precise enough to draw any conclusions about what caused the extinction.
Now, the team has revised its estimates using more accurate dating techniques based on a better understanding of uncertainties in timescale measurements.
With this knowledge, Bowring and his colleagues reanalyzed rock samples collected from five volcanic ash beds at the Permian-Triassic boundary. The researchers pulverized rocks and separated out tiny zircon crystals containing a mix of uranium and lead. They then isolated uranium from lead, and measured the ratios of both isotopes to determine the age of each rock sample.
From their measurements, the researchers determined a much more precise “age model” for the end-Permian extinction, which now appears to have lasted about 60,000 years — with an uncertainty of 48,000 years — and was immediately preceded by a sharp increase in carbon dioxide in the oceans.
‘Spiraling toward the truth’
The new timeline adds weight to the theory that the extinction was triggered by massive volcanic eruptions from the Siberian Traps that released volatile chemicals, including carbon dioxide, into the atmosphere and oceans. With such a short extinction timeline, Bowring says it is possible that a single, catastrophic pulse of magmatic activity triggered an almost instantaneous collapse of all global ecosystems.
To confirm whether the Siberian Traps are indeed the extinction’s smoking gun, Burgess and Bowring plan to determine an equally precise timeline for the Siberian Traps eruptions, and will compare it to the new extinction timeline to see where the two events overlap. The researchers will investigate additional areas in China to see if the duration of the extinction can be even more precisely determined.
“We’ve refined our approach, and now we have higher accuracy and precision,” Bowring says. “You can think of it as slowly spiraling in toward the truth.”
‘Steak-knife’ teeth reveal ecology of oldest land predators
The first top predators to walk on land were not afraid to bite off more than they could chew, a University of Toronto Mississauga study has found.
Graduate student and lead author Kirstin Brink along with Professor Robert Reisz from U of T Mississauga’s Department of Biology suggest that Dimetrodon, a carnivore that walked on land between 298 million and 272 million years ago, was the first terrestrial vertebrate to develop serrated ziphodont teeth.
According to the study published in Nature Communications, ziphodont teeth, with their serrated edges, produced a more-efficient bite and would have allowed Dimetrodon to eat prey much larger than itself.
While most meat-eating dinosaurs possessed ziphodont teeth, fossil evidence suggests serrated teeth first evolved in Dimetrodon some 40 million years earlier than theropod dinosaurs.
“Technologies such as scanning electron microscope (SEM) and histology allowed us to examine these teeth in detail to reveal previously unknown patterns in the evolutionary history of Dimetrodon,” Brink said.
The four-meter-long Dimetrodon was the top of the terrestrial food chain in the Early Permian Period and is considered to be the forerunner of mammals.
According to Brink and Reisz’s research, Dimetrodon had a diversity of previously unknown tooth structures and were also the first terrestrial vertebrate to develop cusps — teeth with raised points on the crown, which are dominant in mammals.
The study also suggests ziphodont teeth were confined to later species of Dimetrodon, indicating a gradual change in feeding habits.
“This research is an important step in reconstructing the structure of ancient complex communities,” Reisz said.
“Teeth tell us a lot more about the ecology of animals than just looking at the skeleton.”
“We already know from fossil evidence which animals existed at that time but now with this type of research we are starting to piece together how the members of these communities interacted.”
Brink and Reisz studied the changes in Dimetrodon teeth across 25 million years of evolution.
The analysis indicated the changes in tooth structure occurred in the absence of any significant evolution in skull morphology. This, Brink and Reisz suggest, indicates a change in feeding style and trophic interactions.
“The steak knife configuration of these teeth and the architecture of the skull suggest Dimetrodon was able to grab and rip and dismember large prey,” Reisz said.
“Teeth fossils have attracted a lot of attention in dinosaurs but much less is known about the animals that lived during this first chapter in terrestrial evolution.”