Earliest Archaeological Evidence of Human Ancestors Hunting and Scavenging
May 10, 2013 — A recent Baylor University research study has shed new light on the diet and food acquisition strategies of some the earliest human ancestors in Africa.
Beginning around two million years ago, early stone tool-making humans, known scientifically as Oldowan hominin, started to exhibit a number of physiological and ecological adaptations that required greater daily energy expenditures, including an increase in brain and body size, heavier investment in their offspring and significant home-range expansion. Demonstrating how these early humans acquired the extra energy they needed to sustain these shifts has been the subject of much debate among researchers.
A recent study led by Joseph Ferraro, Ph.D., assistant professor of anthropology at Baylor, offers new insight in this debate with a wealth of archaeological evidence from the two million-year-old site of Kanjera South (KJS), Kenya. The study’s findings were recently published in PLOS One.
“Considered in total, this study provides important early archaeological evidence for meat eating, hunting and scavenging behaviors -cornerstone adaptations that likely facilitated brain expansion in human evolution, movement of hominins out of Africa and into Eurasia, as well as important shifts in our social behavior, anatomy and physiology,” Ferraro said.
Located on the shores of Lake Victoria, KJS contains “three large, well-preserved, stratified” layers of animal remains. The research team worked at the site for more than a decade, recovering thousands of animal bones and rudimentary stone tools.
According to researchers, hominins at KJS met their new energy requirements through an increased reliance on meat eating. Specifically, the archaeological record at KJS shows that hominins acquired an abundance of nutritious animal remains through a combination of both hunting and scavenging behaviors. The KJS site is the earliest known archaeological evidence of these behaviors.
“Our study helps inform the ‘hunting vs. scavenging’ debate in Paleolithic archaeology. The record at KJS shows that it isn’t a case of either/or for Oldowan hominins two million years ago. Rather hominins at KJS were clearly doing both,” Ferraro said.
The fossil evidence for hominin hunting is particularly compelling. The record shows that Oldowan hominins acquired and butchered numerous small antelope carcasses. These animals are well represented at the site by most or all of their bones from the tops of their head to the tips of their hooves, indicating to researchers that they were transported to the site as whole carcasses.
Many of the bones also show evidence of cut marks made when hominins used simple stone tools to remove animal flesh. Some bones also bear evidence that hominins used fist-sized stones to break them open to acquire bone marrow.
In addition, modern studies in the Serengeti–an environment similar to KJS two million years ago–have also shown that predators completely devour antelopes of this size within minutes of their deaths. As a result, hominins could only have acquired these valuable remains on the savanna through active hunting.
The site also contains a large number of isolated heads of wildebeest-sized antelopes. In contrast to small antelope carcasses, the heads of these somewhat larger individuals are able to be consumed several days after death and could be scavenged, as even the largest African predators like lions and hyenas were unable to break them open to access their nutrient-rich brains.
“Tool-wielding hominins at KJS, on the other hand, could access this tissue and likely did so by scavenging these heads after the initial non-human hunters had consumed the rest of the carcass,” Ferraro said. “KJS hominins not only scavenged these head remains, they also transported them some distance to the archaeological site before breaking them open and consuming the brains. This is important because it provides the earliest archaeological evidence of this type of resource transport behavior in the human lineage.”
Other contributing authors to the study include: Thomas W. Plummer of Queens College & NYCEP; Briana L. Pobiner of the National Museum of Natural History, Smithsonian Institution; James S. Oliver of Illinois State Museum and Liverpool John Moores University; Laura C. Bishop of Liverpool John Moores University; David R. Braun of George Washington University; Peter W. Ditchfield of University of Oxford; John W. Seaman III , Katie M. Binetti and John W. Seaman Jr. of Baylor University; Fritz Hertel of California State University and Richard Potts of the National Museum of Natural History, Smithsonian Institution and National Museums of Kenya.
The research was supported by funding from the National Science Foundation, Leakey Foundation, Wenner-Gren Foundation, National Geographic Society, The Leverhulme Trust, University of California, Baylor University and the City University of New York. Additional logistical support was provided by the Smithsonian Institution’s Human Origins Program and the Peter Buck Fund for Human Origins Research, the British Institute of Eastern Africa and the National Museums of Kenya.
Four New Dinosaur Species Identified
May 8, 2013 — Just when dinosaur researchers thought they had a thorough knowledge of ankylosaurs, a family of squat, armour plated, plant eaters, along comes University of Alberta graduate student, Victoria Arbour.
Arbour visited dinosaur fossil collections from Alberta to the U.K. examining skull armour and comparing those head details with other features of the fossilized ankylosaur remains. She made a breakthrough that resurrected research done more than 70 years ago.
Arbour explains that between 1900 and 1930 researchers had determined that small variations in the skull armour and the tail clubs in some ankylosaurs constituted four individual species of the dinosaurs.
“In the 1970s the earlier work was discarded and those four species were lumped into one called species Euoplocephalus,” said Arbour.
“I examined many fossils and found I could group some fossils together because their skull armour corresponded with a particular shape of their tail club,” said Arbour.
Finding common features in fossils that come from the same geologic time is evidence that the original researchers were right says Arbour. “There were in fact four different species represented by what scientists previously thought was only one species, Euoplocephalus.”
The four species span a period of about 10 million years. Arbour’s research shows three of those ankylosaurs species lived at the same time in what is now Dinosaur Provincial Park in southern Alberta.
Arbour says this opens the door to new questions.
“How did these three species shared their habitat, how did they divide food resources and manage to survive?” said Arbour.
Arbour will also look into how slight differences in skull ornamentation and tail shape between the species influenced the animals’ long reign on Earth.
Arbour’s research was published May 8, in the journal PLOS ONE.
Oldest? New ‘Bone-Head’ Dinosaur Hints at Higher Diversity of Small Dinosaurs
May 7, 2013 — Scientists have named a new species of bone-headed dinosaur (pachycephalosaur) from Alberta, Canada. Acrotholus audeti (Ack-RHO-tho-LUS) was identified from both recently discovered and historically collected fossils. Approximately six feet long and weighing about 40 kilograms in life, the newly identified plant-eating dinosaur represents the oldest bone-headed dinosaur in North America, and possibly the world.
Dr. Michael Ryan, curator of vertebrate paleontology at The Cleveland Museum of Natural History, co-authored research describing the new species, which was published May 7, 2013 in the journal Nature Communications.
Acrotholus means “high dome,” referring to its dome-shaped skull, which is composed of solid bone over 10 centimeters (two inches) thick. The name Acrotholus audeti also honors Alberta rancher Roy Audet, on whose land the best specimen was discovered in 2008. Acrotholus walked on two legs and had a greatly thickened, domed skull above its eyes, which was used for display to other members of its species, and may have also been used in head-butting contests. Acrotholus lived about 85 million years ago.
The new dinosaur discovery is based on two skull ‘caps’ from the Milk River Formation of southern Alberta. One of these was collected by the Royal Ontario Museum (ROM) more than 50 years ago. However, a better specimen was found in 2008 by University of Toronto graduate student Caleb Brown during a field expedition organized by Dr. David Evans of the Royal Ontario Museum and University of Toronto, and Ryan.
“Acrotholus provides a wealth of new information on the evolution of bone-headed dinosaurs. Although it is one of the earliest known members this group, its thickened skull dome is surprisingly well-developed for its geological age,” said lead author Evans, ROM curator, vertebrate palaeontology. “More importantly, the unique fossil record of these animals suggests that we are only beginning to understand the diversity of small-bodied plant-eating dinosaurs.”
Small mammals and reptiles can be very diverse and abundant in modern ecosystems, but small dinosaurs (less than 100 kg) are considerably less common than large ones in the fossil record. Whether this pattern is a true reflection of dinosaur communities, or is related to the greater potential for small bones to be destroyed by carnivores and natural decay, has been debated. The massively constructed skull domes of pachycephalosaurs are resistant to destruction, and are much more common than their relatively delicate skeletons — which resemble those of other small plant-eating dinosaurs. Therefore, the researchers suggest that the pachycephalosaur fossil record can provide valuable insights into the diversity of small, plant-eating dinosaurs as a whole.
“We can predict that many new small dinosaur species like Acrotholus are waiting to be discovered by researchers willing to sort through the many small bones that they pick up in the field,” said co-author Ryan of The Cleveland Museum of Natural History. “This fully domed and mature individual suggests that there is an undiscovered, hidden diversity of small-bodied dinosaurs. So when we look back, we need to reimagine the paleoenvironment. There is an evolutionary history that we just don’t know because the fossil record is incomplete. This discovery also highlights the importance of landowners, like Roy Audet, who grant access to their land and allow scientifically important finds to be made.”
This dinosaur is the latest in a series of new finds being made by Evans and Ryan as part of their Southern Alberta Dinosaur Project, which aims to fill in gaps in of the record of Late Cretaceous dinosaurs and study their evolution. This project focuses on the palaeontology of some of the oldest dinosaur-bearing rocks in Alberta, which have been studied less intensely than those of the famous badlands of Dinosaur Provincial Park and Drumheller.
Acrotholus was identified by a team comprising of palaeontologists Evans, of the Royal Ontario Museum; and Ryan, of The Cleveland Museum of Natural History; as well as Ryan Schott, Caleb Brown, and Derek Larson, all graduate students at the University of Toronto who studied under Evans.
Bird Fossil Sheds Light On How Swift and Hummingbird Flight Came to Be
May 1, 2013 — A tiny bird fossil discovered in Wyoming offers clues to the precursors of swift and hummingbird wings. The fossil is unusual in having exceptionally well-preserved feathers, which allowed the researchers to reconstruct the size and shape of the bird’s wings in ways not possible with bones alone.
Researchers spotted the specimen — the nearly complete skeleton of a bird that would have fit in the palm of your hand and weighed less than an ounce — while working at the Field Museum of Natural History in Chicago.
The newly discovered bird was named Eocypselus rowei, in honor of John W. Rowe, Chairman of the Field Museum’s Board of Trustees.
First collected in southwestern Wyoming in a fossil site known as the Green River Formation, E. rowei lived roughly 50 million years ago, after the dinosaurs disappeared but before the earliest humans came to be.
E. rowei was a tiny bird — only twelve centimeters from head to tail. Feathers account for more than half of the bird’s total wing length.
To find out where the fossil fit in the bird family tree, the researchers compared the specimen to extinct and modern day species. Their analyses suggest that the bird was an evolutionary precursor to the group that includes today’s swifts and hummingbirds.
Given the differences in wing shape between these two closely related groups of birds, scientists have puzzled over how swift and hummingbird flight came to be. Finding fossil relatives like this specimen is key to figuring that out, the researchers say.
“This fossil bird represents the closest we’ve gotten to the point where swifts and hummingbirds went their separate ways,” said lead author Daniel Ksepka of the National Evolutionary Synthesis Center in Durham, North Carolina.
Hummingbirds have short wings relative to their bodies, which makes them good at hovering in mid-air. Swifts have super-long wings for gliding and high-speed flight. But the wings of E. rowei were somewhere in between.
“[Based on its wing shape] it probably wasn’t a hoverer, like a hummingbird, and it probably wasn’t as efficient at fast flight as a swift,” Ksepka said.
The shape of the bird’s wings, coupled with its tiny size, suggest that the ancestors of today’s swifts and hummingbirds got small before each group’s unique flight behavior came to be. “Hummingbirds came from small-bodied ancestors, but the ability to hover didn’t come to be until later,” Ksepka explained.
Closer study of the feathers under a scanning electron microscope revealed that carbon residues in the fossils — once thought to be traces of bacteria that fed on feathers — are fossilized melanosomes, tiny cell structures containing melanin pigments that give birds and other animals their color. The findings suggest that the ancient bird was probably black and may have had a glossy or iridescent sheen, like swifts living today. Based on its beak shape it probably ate insects, the researchers say.
The other authors of this study were Julia Clarke, Sterling Nesbitt and Felicia Kulp of the University of Texas at Austin, and Lance Grande of the Field Museum of Natural History.
The results will appear in the May 1 issue of the journal Proceedings of the Royal Society B.
What Happened to Dinosaurs’ Predecessors After Earth’s Largest Extinction 252 Million Years Ago?
Predecessors to dinosaurs missed the race to fill habitats emptied when nine out of 10 species disappeared during Earth’s largest mass extinction 252 million years ago.
Or did they?
That thinking was based on fossil records from sites in South Africa and southwest Russia.
It turns out, however, that scientists may have been looking in the wrong places.
Newly discovered fossils from 10 million years after the mass extinction reveal a lineage of animals thought to have led to dinosaurs in Tanzania and Zambia.
That’s still millions of years before dinosaur relatives were seen in the fossil record elsewhere on Earth.
“The fossil record from the Karoo of South Africa, for example, is a good representation of four-legged land animals across southern Pangea before the extinction,” says Christian Sidor, a paleontologist at the University of Washington.
Pangea was a landmass in which all the world’s continents were once joined together. Southern Pangea was made up of what is today Africa, South America, Antarctica, Australia and India.
“After the extinction,” says Sidor, “animals weren’t as uniformly and widely distributed as before. We had to go looking in some fairly unorthodox places.”
Sidor is the lead author of a paper reporting the findings; it appears in this week’s issue of the journal Proceedings of the National Academy of Sciences.
The insights come from seven fossil-hunting expeditions in Tanzania, Zambia and Antarctica funded by the National Science Foundation (NSF). Additional work involved combing through existing fossil collections.
“These scientists have identified an outcome of mass extinctions–that species ecologically marginalized before the extinction may be ‘freed up’ to experience evolutionary bursts then dominate after the extinction,” says H. Richard Lane, program director in NSF’s Division of Earth Sciences.
The researchers created two “snapshots” of four-legged animals about five million years before, and again about 10 million years after, the extinction 252 million years ago.
Prior to the extinction, for example, the pig-sized Dicynodon–said to resemble a fat lizard with a short tail and turtle’s head–was a dominant plant-eating species across southern Pangea.
After the mass extinction, Dicynodon disappeared. Related species were so greatly decreased in number that newly emerging herbivores could then compete with them.
“Groups that did well before the extinction didn’t necessarily do well afterward,” Sidor says.
The snapshot of life 10 million years after the extinction reveals that, among other things, archosaurs roamed in Tanzanian and Zambian basins, but weren’t distributed across southern Pangea as had been the pattern for four-legged animals before the extinction.
Archosaurs, whose living relatives are birds and crocodilians, are of interest to scientists because it’s thought that they led to animals like Asilisaurus, a dinosaur-like animal, and Nyasasaurus parringtoni, a dog-sized creature with a five-foot-long tail that could be the earliest dinosaur.
“Early archosaurs being found mainly in Tanzania is an example of how fragmented animal communities became after the extinction,” Sidor says.
A new framework for analyzing biogeographic patterns from species distributions, developed by paper co-author Daril Vilhena of University of Washington, provided a way to discern the complex recovery.
It revealed that before the extinction, 35 percent of four-legged species were found in two or more of the five areas studied.
Some species’ ranges stretched 1,600 miles (2,600 kilometers), encompassing the Tanzanian and South African basins.
Ten million years after the extinction, there was clear geographic clustering. Just seven percent of species were found in two or more regions.
The technique–a new way to statistically consider how connected or isolated species are from each other–could be useful to other paleontologists and to modern-day biogeographers, Sidor says.
Beginning in the early 2000s, he and his co-authors conducted expeditions to collect fossils from sites in Tanzania that hadn’t been visited since the 1960s, and in Zambia where there had been little work since the 1980s.
Two expeditions to Antarctica provided additional finds, as did efforts to look at museum fossils that had not been fully documented or named.
The fossils turned out to hold a treasure trove of information, the scientists say, on life some 250 million years ago.
Other co-authors of the paper are Adam Huttenlocker, Brandon Peecook, Sterling Nesbitt and Linda Tsuji from University of Washington; Kenneth Angielczyk of the Field Museum of Natural History in Chicago; Roger Smith of the Iziko South African Museum in Cape Town; and Sébastien Steyer from the National Museum of Natural History in Paris.
The project was also funded by the National Geographic Society, Evolving Earth Foundation, the Grainger Foundation, the Field Museum/IDP Inc. African Partners Program, and the National Research Council of South Africa.
First Snapshot of Organisms Eating Each Other: Feast Clue to Smell of Ancient Earth
Apr. 29, 2013 — Tiny 1,900 million-year-old fossils from rocks around Lake Superior, Canada, give the first ever snapshot of organisms eating each other and suggest what the ancient Earth would have smelled like.
The fossils, preserved in Gunflint chert, capture ancient microbes in the act of feasting on a cyanobacterium-like fossil called Gunflintia — with the perforated sheaths of Gunflintia being the discarded leftovers of this early meal.
A team, led by Dr David Wacey of the University of Western Australia and Bergen University, Norway, and Professor Martin Brasier of Oxford University, reports in this week’s Proceedings of the National Academy of Sciences the fossil evidence for how this type of feeding on organic matter — called ‘heterotrophy’ — was taking place. They also show that the ancient microbes appeared to prefer to snack on Gunflintia as a ‘tasty morsel’ in preference to another bacterium (Huroniospora).
‘What we call ‘heterotrophy’ is the same thing we do after dinner as the bacteria in our gut break down organic matter,’ said Professor Martin Brasier of Oxford University’s Department of Earth Sciences, an author of the paper. ‘Whilst there is chemical evidence suggesting that this mode of feeding dates back 3,500 million years, in this study for the first time we identify how it was happening and ‘who was eating who’. In fact we’ve all experienced modern bacteria feeding in this way as that’s where that ‘rotten egg’ whiff of hydrogen sulfide comes from in a blocked drain. So, rather surprisingly, we can say that life on earth 1,900 million years ago would have smelled a lot like rotten eggs.’
The team analysed the microscopic fossils, ranging from about 3-15 microns in diameter, using a battery of new techniques and found that one species — a tubular form thought to be the outer sheath of Gunflintia — was more perforated after death than other kinds, consistent with them having been eaten by bacteria.
In some places many of the tiny fossils had been partially or entirely replaced with iron sulfide (‘fool’s gold’) a waste product of heterotrophic sulfate-reducing bacteria that is also a highly visible marker. The team also found that these Gunflintia fossils carried clusters of even smaller (c.1 micron) spherical and rod-shaped bacteria that were seemingly in the process of consuming their hosts.
Dr Wacey said that: ‘recent geochemical analyses have shown that the sulfur-based activities of bacteria can likely be traced back to 3,500 million years or so — a finding reported by our group in Nature Geoscience in 2011. Whilst the Gunflint fossils are only about half as old, they confirm that such bacteria were indeed flourishing by 1,900 million years ago. And that they were also highly particular about what they chose to eat.’
Fish Was On the Menu for Early Flying Dinosaur
Apr. 22, 2013 — University of Alberta-led research reveals that Microraptor, a small flying dinosaur was a complete hunter, able to swoop down and pickup fish as well as its previously known prey of birds and tree dwelling mammals.
U of A paleontology graduate student Scott Persons says new evidence of Microrpator’s hunting ability came from fossilized remains in China. “We were very fortunate that this Microraptor was found in volcanic ash and its stomach content of fish was easily identified.”
Prior to this, paleontologists believed microraptors which were about the size of a modern day hawk, lived in trees where they preyed exclusively on small birds and mammals about the size of squirrels.
“Now we know that Microraptor operated in varied terrain and had a varied diet,” said Persons. “It took advantage of a variety of prey in the wet, forested environment that was China during the early Cretaceous period, 120 million years ago.”
Further analysis of the fossil revealed that its teeth were adapted to catching slippery, wiggling prey like fish. Dinosaur researchers have established that most meat eaters had teeth with serrations on both sides which like a steak knife helped the predator saw through meat.
But the Microraptor’s teeth are serrated on just one side and its teeth are angled forwards.
“Microraptor seems adapted to impale fish on its teeth. With reduced serrations the prey wouldn’t tear itself apart while it struggled,” said Persons. “Microraptor could simply raise its head back, the fish would slip off the teeth and be swallowed whole, no fuss no muss.”
Persons likens the Microraptor’s wing configuration to a bi-plane. “It had long feathers on its forearms, hind legs and tail,” said Persons. “It was capable of short, controlled flights.”
This is the first evidence of a flying raptor, a member of the Dromaeosaur family of dinosaurs to successfully prey on fish.
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 Carnivorous Dinosaur from Madagascar Raises More Questions Than It Answers
The first new species of dinosaur from Madagascar in nearly a decade was announced today, filling an important gap in the island’s fossil record.
Dahalokely tokana (pronounced “dah-HAH-loo-KAY-lee too-KAH-nah”) is estimated to have been between nine and 14 feet long, and it lived around 90 million years ago. Dahalokely belongs to a group called abelisauroids, carnivorous dinosaurs common to the southern continents. Up to this point, no dinosaur remains from between 165 and 70 million years ago could be identified to the species level in Madagascar-a 95 million year gap in the fossil record. Dahalokely shortens this gap by 20 million years.
The fossils of Dahalokely were excavated in 2007 and 2010, near the city of Antsiranana (Diego-Suarez) in northernmost Madagascar. Bones recovered included vertebrae and ribs. Because this area of the skeleton is so distinct in some dinosaurs, the research team was able to definitively identify the specimen as a new species. Several unique features — including the shape of some cavities on the side of the vertebrae — were unlike those in any other dinosaur. Other features in the vertebrae identified Dahalokely as an abelisauroid dinosaur.
When Dahalokely was alive, Madagascar was connected to India, and the two landmasses were isolated in the middle of the Indian Ocean. Geological evidence indicates that India and Madagascar separated around 88 million years ago, just after Dahalokely lived. Thus, Dahalokely potentially could have been ancestral to animals that lived later in both Madagascar and India. However, not quite enough of Dahalokely is yet known to resolve this issue. The bones known so far preserve an intriguing mix of features found in dinosaurs from both Madagascar and India.
“We had always suspected that abelisauroids were in Madagascar 90 million years ago, because they were also found in younger rocks on the island. Dahalokely nicely confirms this hypothesis,” said project leader Andrew Farke, Augustyn Family Curator of Paleontology at the Raymond M. Alf Museum of Paleontology. Farke continued, “But, the fossils of Dahalokely are tantalizingly incomplete — there is so much more we want to know. Was Dahalokely closely related to later abelisauroids on Madagascar, or did it die out without descendents?”
The name “Dahalokely tokana” is from the Malagasy language, meaning “lonely small bandit.” This refers to the presumed carnivorous diet of the animal, as well as to the fact that it lived at a time when the landmasses of India and Madagascar together were isolated from the rest of the world.
“This dinosaur was closely related to other famous dinosaurs from the southern continents, like the horned Carnotaurus from Argentina and Majungasaurus, also from Madagascar,” said project member Joe Sertich, Curator of Dinosaurs at the Denver Museum of Nature & Science and the team member who discovered the new dinosaur. “This just reinforces the importance of exploring new areas around the world where undiscovered dinosaur species are still waiting,” added Sertich.
The research was funded by the Jurassic Foundation, Sigma Xi, National Science Foundation, and the Raymond M. Alf Museum of Paleontology. The paper naming Dahalokely appears in the April 18, 2013, release of the journal PLOS ONE.
Coelacanth Genome Surfaces: Unexpected Insights from a Fish With a 300-Million-Year-Old Fossil Record
Apr. 17, 2013 — An international team of researchers has decoded the genome of a creature whose evolutionary history is both enigmatic and illuminating: the African coelacanth. A sea-cave dwelling, five-foot long fish with limb-like fins, the coelacanth was once thought to be extinct. A living coelacanth was discovered off the African coast in 1938, and since then, questions about these ancient-looking fish — popularly known as “living fossils” — have loomed large. Coelacanths today closely resemble the fossilized skeletons of their more than 300-million-year-old ancestors. Its genome confirms what many researchers had long suspected: genes in coelacanths are evolving more slowly than in other organisms.
“We found that the genes overall are evolving significantly slower than in every other fish and land vertebrate that we looked at,” said Jessica Alföldi, a research scientist at the Broad Institute and co-first author of a paper on the coelacanth genome, which appears in Nature this week. “This is the first time that we’ve had a big enough gene set to really see that.”
Researchers hypothesize that this slow rate of change may be because coelacanths simply have not needed to change: they live primarily off of the Eastern African coast (a second coelacanth species lives off the coast of Indonesia), at ocean depths where relatively little has changed over the millennia.
“We often talk about how species have changed over time,” said Kerstin Lindblad-Toh, scientific director of the Broad Institute’s vertebrate genome biology group and senior author. “But there are still a few places on Earth where organisms don’t have to change, and this is one of them. Coelacanths are likely very specialized to such a specific, non-changing, extreme environment — it is ideally suited to the deep sea just the way it is.”
Because of their resemblance to fossils dating back millions of years, coelacanths today are often referred to as “living fossils” — a term coined by Charles Darwin. But the coelacanth is not a relic of the past brought back to life: it is a species that has survived, reproduced, but changed very little in appearance for millions of years. “It’s not a living fossil; it’s a living organism,” said Alföldi. “It doesn’t live in a time bubble; it lives in our world, which is why it’s so fascinating to find out that its genes are evolving more slowly than ours.”
The coelacanth genome has also allowed scientists to test other long-debated questions. For example, coelacanths possess some features that look oddly similar to those seen only in animals that dwell on land, including “lobed” fins, which resemble the limbs of four-legged land animals (known as tetrapods). Another odd-looking group of fish known as lungfish possesses lobed fins too. It is likely that one of the ancestral lobed-finned fish species gave rise to the first four-legged amphibious creatures to climb out of the water and up on to land, but until now, researchers could not determine which of the two is the more likely candidate.
In addition to sequencing the full genome — nearly 3 billion “letters” of DNA — from the coelacanth, the researchers also looked at RNA content from coelacanth (both the African and Indonesian species) and from the lungfish. This information allowed them to compare genes in use in the brain, kidneys, liver, spleen and gut of lungfish with gene sets from coelacanth and 20 other vertebrate species. Their results suggested that tetrapods are more closely related to lungfish than to the coelacanth.
However, the coelacanth is still a critical organism to study in order to understand what is often called the water-to-land transition. Lungfish may be more closely related to land animals, but its genome remains inscrutable: at 100 billion letters in length, the lungfish genome is simply too unwieldy for scientists to sequence, assemble, and analyze. The coelacanth’s more modest-sized genome (comparable in length to our own) is yielding valuable clues about the genetic changes that may have allowed tetrapods to flourish on land.
By looking at what genes were lost when vertebrates came on land as well as what regulatory elements — parts of the genome that govern where, when, and to what degree genes are active — were gained, the researchers made several unusual discoveries:
•Sense of smell. The team found that many regulatory changes influenced genes involved in smell perception and detecting airborne odors. They hypothesize that as creatures moved from sea to land, they needed new means of detecting chemicals in the environment around them.
•Immunity. The researchers found a significant number of immune-related regulatory changes when they compared the coelacanth genome to the genomes of animals on land. They hypothesized that these changes may be part of a response to new pathogens encountered on land.
•Evolutionary development. Researchers found several key genetic regions that may have been “evolutionarily recruited” to form tetrapod innovations such as limbs, fingers and toes, and the mammalian placenta. One of these regions, known as HoxD, harbors a particular sequence that is shared across coelacanths and tetrapods. It is likely that this sequence from the coelacanth was co-opted by tetrapods to help form hands and feet.
•Urea cycle. Fish get rid of nitrogen by excreting ammonia into the water, but humans and other land animals quickly convert ammonia into less toxic urea using the urea cycle. Researchers found that the most important gene involved in this cycle has been modified in tetrapods.
The coelacanth genome may hold other clues for researchers investigating the evolution of tetrapods. “This is just the beginning of many analyses on what the coelacanth can teach us about the emergence of land vertebrates, including humans, and, combined with modern empirical approaches, can lend insights into the mechanisms that have contributed to major evolutionary innovations,” said Chris Amemiya, a member of the Benaroya Research Institute and co-first author of the Nature paper. Amemiya is also a professor at the University of Washington.
Sequencing the full coelacanth genome was uniquely challenging for many reasons. Coelacanths are an endangered species, meaning that samples available for research are almost nonexistent. This meant that each sample obtained was precious: researchers would have “one shot” at sequencing the collected genetic material, according to Alföldi. But the difficulties in obtaining a sample and the challenges of sequencing it also knit the community together.
“The international nature of the work, its evolutionary value and history, and the fact that it was a technically challenging project really brought people together,” said Lindblad-Toh. ” We had representatives from every populated continent on earth working on this project.”
Although its genome offers some tantalizing answers, the research team anticipates that further study of the fish’s immunity, respiration, physiology, and more will lead to deep insights into how some vertebrates adapted to life on land, while others remained creatures of the sea.