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.
World’s Oldest Dinosaur Embryo Bonebed Yields Organic Remains
Apr. 10, 2013 — The great age of the embryos is unusual because almost all known dinosaur embryos are from the Cretaceous Period. The Cretaceous ended some 125 million years after the bones at the Lufeng site were buried and fossilized.
Led by University of Toronto Mississauga paleontologist Robert Reisz, an international team of scientists from Canada, Taiwan, the People’s Republic of China, Australia, and Germany excavated and analyzed over 200 bones from individuals at different stages of embryonic development.
“We are opening a new window into the lives of dinosaurs,” says Reisz. “This is the first time we’ve been able to track the growth of embryonic dinosaurs as they developed. Our findings will have a major impact on our understanding of the biology of these animals.”
The bones represent about 20 embryonic individuals of the long-necked sauropodomorph Lufengosaurus, the most common dinosaur in the region during the Early Jurassic period. An adult Lufengosaurus was approximately eight metres long.
The disarticulated bones probably came from several nests containing dinosaurs at various embryonic stages, giving Reisz’s team the rare opportunity to study ongoing growth patterns. Dinosaur embryos are more commonly found in single nests or partial nests, which offer only a snapshot of one developmental stage.
To investigate the dinosaurs’ development, the team concentrated on the largest embryonic bone, the femur. This bone showed a consistently rapid growth rate, doubling in length from 12 to 24 mm as the dinosaurs grew inside their eggs. Reisz says this very fast growth may indicate that sauropodomorphs like Lufengosaurus had a short incubation period.
Reisz’s team found the femurs were being reshaped even as they were in the egg. Examination of the bones’ anatomy and internal structure showed that as they contracted and pulled on the hard bone tissue, the dinosaurs’ muscles played an active role in changing the shape of the developing femur. “This suggests that dinosaurs, like modern birds, moved around inside their eggs,” says Reisz. “It represents the first evidence of such movement in a dinosaur.”
The Taiwanese members of the team also discovered organic material inside the embryonic bones. Using precisely targeted infrared spectroscopy, they conducted chemical analyses of the dinosaur bone and found evidence of what Reisz says may be collagen fibres. Collagen is a protein characteristically found in bone.
“The bones of ancient animals are transformed to rock during the fossilization process,” says Reisz. “To find remnants of proteins in the embryos is really remarkable, particularly since these specimens are over 100 million years older than other fossils containing similar organic material.”
Only about one square metre of the bonebed has been excavated to date, but this small area also yielded pieces of eggshell, the oldest known for any terrestrial vertebrate. Reisz says this is the first time that even fragments of such delicate dinosaur eggshells, less than 100 microns thick, have been found in good condition.
“A find such as the Lufeng bonebed is extraordinarily rare in the fossil record, and is valuable for both its great age and the opportunity it offers to study dinosaur embryology,” says Reisz. “It greatly enhances our knowledge of how these remarkable animals from the beginning of the Age of Dinosaurs grew.”
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.
Diversification in Ancient Tadpole Shrimps Challenges the Term ‘Living Fossil’
Apr. 2, 2013 — The term ‘living fossil’ has a controversial history. For decades, scientists have argued about its usefulness as it appears to suggest that some organisms have stopped evolving. New research has now investigated the origin of tadpole shrimps, a group commonly regarded as ‘living fossils’ which includes the familiar Triops. The research reveals that living species of tadpole shrimp are much younger than the fossils they so much resemble, calling into question the term ‘living fossil’.
Darwin informally introduced the term ‘living fossil’ in On the Origin of Species when talking about the platypus and lungfish, groups that appear to have diversified little and appear not to have changed over millions of years. For him living fossils were odd remnants of formerly more diverse groups, and suggestive of a connection between different extant groups. Ever since, the term has been widely used to describe organisms such as the coelacanth, the horseshoe crab and the ginkgo tree. The term has been controversial, as it appears to suggest that evolution has stopped altogether for these organisms, and some scientists have argued that it should be abandoned.
Tadpole shrimps are a small group of ancient crustaceans (a group which includes the familiar Triops) that are often called ‘living fossils’, because the living species look virtually identical to fossils older than the dinosaurs. Analysing DNA sequences of all known tadpole shrimps, and using fossils from related crustacean groups — such as the water flea and the brine shrimp — the team of researchers, from the University of Hull, University of Leicester and the Natural History Museum in London, showed that tadpole shrimps have in fact undergone several periods of radiation and extinction. The new study is published today in PeerJ, a new peer reviewed open access journal in which all articles are freely available to everyone (https://PeerJ.com).
Different species of tadpole shrimp often look very similar (they are called ‘cryptic species’), and so it is only with the advent of DNA sequencing that scientists have realized that they are a surprisingly diverse group. The team’s results uncovered a total of 38 species, many of them still undescribed. This abundance of ‘cryptic species’ makes it very difficult for fossils to be assigned to any particular species as they all look remarkably similar. For example, 250-million-year-old fossils have been assigned to the living European species Triops cancriformis whereas the team’s results indicate that the living T. cancriformis evolved less than 25 million years ago. First author Tom Mathers says “In groups like tadpole shrimps where cryptic speciation is common, the fossil record says very little about patterns of evolution and diversification and so the term ‘living fossil’ can be quite misleading. For this reason, we used fossils from related groups to gain an understanding about the evolution of tadpole shrimps.”
The lead author Africa Gómez said, “Living fossils evolve like any other organism, they just happen to have a good body plan that has survived the test of time. A good analogy could be made with cars. For example the Mini has an old design that is still selling, but newly made Minis have electronic windows, GPS and airbags: in that sense, they are still ‘evolving’, they are not unchanged but most of the change has been ‘under the hood’ rather than external. By comparison, organisms labeled as ‘living fossils’ such as tadpole shrimps, are constantly fine-tuning their adaptation to their environment. Although outwardly they look very similar to tadpole shrimp fossils from the age of the dinosaurs, their DNA and reproductive strategies are relatively hidden features that are constantly evolving. The flexibility of their reproductive strategies, which our research has revealed, could be the evolutionary trick that has allowed them to persist as a morphologically conservative group for so long.”
Background
Tadpole shrimps include the familiar Triops — which is often sold as dried eggs in toy shops — that can easily be grown at home. Their fossils can be found from the Carboniferous, 300 million years ago, and the group has survived several mass extinction events. Currently, tadpole shrimps occupy a range of temporal aquatic habitats with different water chemistry conditions, such as hypersaline Australian lakes, rice fields, coastal pools, river floodplains and arctic ponds. Their eggs can survive in a dry state for several decades, only hatching when suitable conditions return.