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Alberta is a great place for a dinosaur palaeontologist, with plenty of preserved skeletons and some of the best evidence for dinosaurs in the world.

However, in the Willow Creek Formation of southwestern Alberta, which records the last few million years before the extinction of dinosaurs, only three kinds of dinosaur skeletons have been found: Tyrannosaurus rex, an undetermined hadrosaur (duck-billed dinosaur), and an undetermined leptoceratopsid (small horned dinosaur). Were those the only dinosaurs living here during that time? Unlikely, but how do we know what dinosaurs were present if their skeletons weren’t preserved?

Unlike many geological formations in Alberta, dinosaur eggshells are quite common in the Willow Creek Formation. The ancient soils (a.k.a. paleosols) present in the formation suggest that conditions were arid to semi-arid at the time, which led to excellent preservation of dinosaur eggshell. Like skeletons, eggshells tend to be distinctive between the various kinds of dinosaurs and can be used to identify what dinosaurs were present.

A new scientific article by our Curator of Dinosaur Palaeoecology, François Therrien, in collaboration with Darla K. Zelenitsky, Kohei Tanaka, Philip J. Currie, and Christopher L. DeBuhr, presents an analysis of eggshells discovered in the Willow Creek Formation. The team inspected hundreds of dinosaur eggshells recovered from several sites in southwestern Alberta. They were able to determine that the eggshell fragments were produced by at least seven different types of dinosaurs: two ornithopods (a group of bipedal, herbivorous dinosaurs, including hadrosaurs) and five small theropods, including oviraptorosaurs, troodontids, and dromaeosaurs (colloquially, raptors). Because researchers frequently cannot correlate an eggshell with a specific species unless it is associated with a parent or a baby inside the egg, eggshells are given their own species names, in parallel to the way skeletons are named. These are called ootaxa.

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Montanoolithus eggshell, belonging to a small theropod, was discovered in southwestern Alberta. Art by Julius T. Csotonyi.

This research triples the known dinosaur diversity of the Willow Creek Formation, from three species based on skeletons only, to at least nine known from skeletons and eggshells. In addition, it extends the known temporal range of some of the ootaxa to 10 million years and gives a better sense of the ancient ecosystem in southwestern Alberta at the end of the Age of the Dinosaurs.

The article, titled “Latest Cretaceous eggshell assemblage from the Willow Creek Formation (upper Maastrichtian – lower Paleocene) of Alberta, Canada, reveals higher dinosaur diversity than represented by skeletal remains,” was published in the January 2017 issue of the Canadian Journal of Earth Science.

With the cold weather and the short days, it’s safe to say that most people are missing summer. For our palaeontologists though, the winter months are an important part of the research process. In summer, they go out in the field to dig up new specimens. Winter is the time for analyzing what they’ve collected, writing it up, and perhaps even publishing a paper on a new discovery. We’ve asked our palaeontologists how they spent last summer and, in this two part series, they summarize the work they accomplished.

David Eberth, Research Scientist, Sedimentary Geology and Palaeoecology

During the 2016 field season, I was able to make exciting new adjustments to the geologic time scale for Alberta. For the past 31 years, I have been involved in assessing the ages of bentonites that are associated with Alberta’s dinosaurs.  Bentonites are ancient volcanic ash and glass deposits that have been geologically altered by burial pressure and temperature after they were exploded from volcanoes. Given the mineral crystals they contain formed at the time of eruption and deposition, the tiny amounts of radioactive isotopes they contain can be analyzed to assess the age of sediments and fossils they were deposited with.

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Dry bentonite from Midland Provincial Park

Hunting for bentonites takes patience and requires lots of digging and hauling. A sample that looks good at the surface may turn out to be a bust once I dig more deeply into the rock. In the field, I examine samples with a hand lens, but samples must also be examined in much greater detail in the laboratory using a microscope. As it takes lots of effort to get to a location, I often collect a potential sample in bulk before returning to the lab. A bulk sample usually means six large zip-lock bags of rock that weigh about as much as two bowling balls.

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Collecting samples is hard work!

Over the years there have been incredible advances in the science of radioisotopic dating. When I started out studying the ages of bentonites in the late 1980s, I was limited to using potassium-argon, and argon40/argon39 dating, which provided accuracy at the level of plus-or-minus 1 million years. Such results allowed me to compare the approximate ages of dinosaur occurrences from different places around the world, but prevented me from making detailed comparisons. More recently I have turned to a revolutionary new technique called uranium lead chemical abrasion thermal induction mass spectrometry (U-Pb CA-TIMS dating, for short). This technique uses zircon crystals that occur in the bentonites and provides very high resolution ages for Alberta’s dinosaurs — plus-or-minus 30,000 years.  For dinosaurs that are about 70 million years old, such accuracy and resolution is phenomenal. Today’s results are more than 20 times more accurate and precise than when I began studying bentonites in the 1980s. Calibrating the age of Alberta’s dinosaurs with such high precision has had profound scientific significance on our research at the Royal Tyrrell Museum of Palaeontology; we can assess patterns of dinosaur evolution, migration, and response to changes in climate and sea-level around the world. With so much new technology available, it’s an exciting time to be studying dinosaurs!

Prior to this summer, my work with CA-TIMS has focused on recalibrating the ages of the rocks and fossils at Dinosaur Provincial Park. Today we know that the dinosaurs at the Park range in age from 76.69 million years to 74.26 million years. This past summer, I spent many hours hunting for datable bentonites in the Horseshoe Canyon Formation in the Drumheller area. Six bentonites were ultimately targeted and will be dated this year.

Dennis Braman, Research Scientist, Palynology

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Callum Creek area

While not much field work happened this summer, the main focus was trying to unravel the biostratigraphy of the vertebrate localities along the Oldman River. Biostratigraphy is the use of fossils to date rock formations – if you know approximately when a plant or animal lived from other sites, you know approximately the age of any rock that contains them. I collected samples from a tributary of the Oldman River near Callum Creek with poor results, a section along the Crowsnest River that indicated the Willow Creek Formation is younger than that exposed along the Oldman River, and a section north of Pierce, Alberta, again to try to work out the biostratigraphy as it relates to the section along the Oldman River west of the Porcupine Hills. I have also been doing in-house work trying to determine the ages of a number of other vertebrate localities with the samples provided by other researchers.

Don Brinkman, Head of Preservation and Research, and James Gardener, Curator of Palaeoherpetology

Vertebrate microfossil localities are accumulations of smaller-sized (about 5 cm and less) fossilized bones, teeth, scales, and other hard body parts from vertebrates (animals with backbones). These fossil localities typically occur in fine-grained sedimentary rocks that were deposited in ancient rivers and ponds and on adjacent, low lying areas such as floodplains. The preserved fossils generally represent a mixture of aquatic, semi-aquatic, and terrestrial animals that lived within a localized area and during a restricted interval of time (tens to hundreds of years).  Although the fossils themselves are small, animals of different body sizes are routinely represented. For example, tiny jaws and vertebrae from small animals, such as frogs and minnow-sized fish, may be preserved along with thumb-sized teeth and toe bones from large dinosaurs.

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A salamander vertebra in situ

Fossils from vertebrate microfossil localities are important for providing information about the different kinds of animals represented at the localities and insights into ancient ecosystems. In fact, much of what we know about smaller- and medium-sized animals (less than 75 kilograms) during the last 15 million years of the Late Cretaceous in Alberta is founded on fossils from vertebrate microfossil localities.

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The Royal Tyrrell Museum of Palaeontology has long been interested in locating, collecting, and studying vertebrate microfossil localities (for further details on that and other research programs at the Museum, see the 2015 paper entitled “Introduction to the Special Issue commemorating the 30th anniversary of the Royal Tyrrell Museum of Palaeontology, with a summary of the Museum’s early history and its research contributions,” available for free download). A region of particular focus for the Museum has been the richly fossiliferous Dinosaur Provincial Park in southern Alberta. There, several dozens of vertebrate microfossil localities have been identified through an 85 metre sequence of rocks that spans about two million years of time during the latter part of the Late Cretaceous.

During the 2016 field season, Drs. Don Brinkman and Jim Gardner re-located and photo documented 20 vertebrate microfossil localities in Dinosaur Provincial Park. This survey was a first step in preparing to re-sample and study selected vertebrate microfossil localities of interest to their respective research agendas.

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Dr. Don Brinkman poses at one of the sites

At the end of the 2016 field season, Museum staff sampled the new eggshell locality. This locality is interesting because it preserves abundant and well-preserved bones of teleost fish and amphibians, groups of particular interest to Brinkman and Gardner, respectively.  It also was the first vertebrate microfossil locality that Brinkman found when he began his work in 1985. Nearly 600 kilograms of fossiliferous matrix were collected from the new eggshell locality and transported to the Royal Tyrrell Museum of Palaeontology. Over the winter, the matrix will be washed through fine screens to recover the fossils.  We look forward to seeing what treasures might be revealed.

Join us for part two of this series, where we share what our mammologist and dinosaur palaeontologists were up to last summer!

The extinction of mammoths is the most prominent of Late Pleistocene extinctions that wiped out nearly 70% of large mammals (megafauna) from western Europe through South America about 10,000 years ago. However, on small islands off the coast of Alaska and Siberia, populations of mammoths persisted for many thousands of years after mainland populations disappeared.

In his talk, Dr. Duane Froese from the University of Alberta presents new research on the extinction of mammoths and other megafauna from Arctic North America and the causes of the final extinction of a population on St. Paul Island, Alaska, about 6000 years ago.

Congratulations to the Royal Tyrrell Museum’s Palaeoichthyology Research Assistant, Dr. Julien Divay. A paper which he coauthored is one of publishing company Elsevier’s top five most cited articles from the journal Cretaceous Research for the past three years. Why is this? Dr. Divay explains:

The article describes dinosaur ichnoassemblages (assemblages of trace fossils, in this case footprints and track ways) from the late Early Cretaceous of southern Shandong Province, in eastern China. In recent years, China has been investing money into the preservation and study of its geological/palaeontological heritage, by creating geoparks (China has 200 now, compared to Canada’s two parks, Stonehammer and Tumbler Ridge, and Tumbler Ridge was only recognised since the publication of our article), and inviting international researchers to work on them. That is how I was invited to tour multiple localities throughout China in 2012, including the Shandong sites, and to publish on these as part of an international collaboration led by Dr. Lida Xing (then a Ph.D. student and now a professor at China University of Geosciences, Beijing campus). We also took the opportunity to publish on a fish from Chongqing around the time I started at the Royal Tyrrell Museum in spring of 2015.

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Eight of the ten authors (from left): Julien Divay, Richard McCrea and Lisa Buckley (Peace Region Palaeontology Research Centre, BC), Lida Xing (CUG, Beijing), Martin Lockley (University of Colorado, Denver), Qingzi Wu (Land and Resources Bureau, Shandong), Hendrik Klein (Saurierwelt Paläontologisches Museum, Neumarkt, Germany), Daniel Marty (Office de la culture, Paléontologie A16, Switzerland), and Yonggang Tang (palaeoartist).

The Cretaceous Research article “Diverse dinosaur ichnoassemblages from the Lower Cretaceous Dasheng Group in the Yishu fault zone, Shandong Province, China,” published in 2013, is co-authored by ten people based in China, the U.S., Switzerland, Germany, Poland, and Canada. I suspect that its popularity is based on three factors:

  • It is part of this push to publish the previously undocumented palaeo heritage of China, meaning that all of these new articles coming out in recent years are quite popular in China, and have a tendency to cite one another. This is likely all the more true for dinosaur tracks articles, since these were mostly ignored in China up until just a few years ago, and are now worked on by a relatively small group of people. In fact, the trip ended with the holding of the first Chinese Dinosaur Tracks Symposium in Qijiang with pretty much all of us.
  • The assemblages of Shandong are diverse, with at least two different groups of theropods, at least two different groups of sauropods differentiated by morphology and posture, and a mysterious tetradactyl (four-toed) track way that we tentatively (but, I think, reliably) attribute to a psittacosaur.
  • One of the theropod track ways is didactyl (two-toed), which is quite rare. This also gets a lot of attention, since it represents a deinonychosaurian (colloquially: a medium-sized raptor) track, and these tend to be crowd-pleasers
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Some of the didactyl tracks.

Dragon; fossil

Comments Divay: “One of my favourite pictures: As I went prospecting for more tracks around one of the localities, I found this statue of a pacing dragon, immediately above the didactyl track way (Lida and the crane we were using are visible at the bottom of the hill, to the right). 2012 was a year of the dragon, too, by the way.”

The paper is available in Cretaceous Research 45 (2013).

Dinosaur Provincial Park received a special pair of visitors in August: Drs. Pan Conrad and Dina Bower of the Planetary Environments Laboratory at the NASA Goddard Space Flight Center in Maryland. Dr. Conrad is an astrobiologist and mineralogist. She studies both minerals and extraterrestrial life. Dr. Bower is a palaeobiologist and geobiologist—she studies microbes from the beginning of life on Earth. Both are involved in the search for proof of prehistoric life on Mars.

Mars and Earth formed at the same time but look radically different now. It’s unclear if this is merely because of their respective locations (Earth is in a sweet spot, Mars not so much) or because Mars was damaged in some way. About four million years after the planets were formed, asteroids shot through the solar system and Mars may have been hit so badly that the planet re-melted. We do know that its magnetic field was lost, which means the planet has no protection against deadly radiation, both background radiation and from the sun.

full_marsWhy does this matter? These deadly radioactive particles are able to strip away a planet’s atmosphere. It’s possible that life emerged at the same time on both Earth and Mars (either concurrently or one seeded the other—yes, there is a possibility that all life on Earth is technically extraterrestrial); however, life on Mars was thwarted. While there are no signs of life on the surface of Mars, there may be evidence beneath the surface. As there are a lot of rocks on Mars, the challenge is figuring out which ones may hold the fossils of early life.

We know roughly when life emerged on Earth, so the best place to start looking is in rocks that are the same age, but dating rocks on Mars is tricky. On Earth, we need to know the mass of a sample in order to accurately date it. As there is currently no way to bring samples back from Mars, how can we get samples to analyze?

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One of the most exciting things about the Royal Tyrrell Museum is that it’s more than a Museum, it’s an active research facility, so there are exciting things happening all the time that further our understanding of ancient life.

Dr. James Gardner, our Curator of Palaeoherpetology (the study of prehistoric reptiles and amphibians), has just published a paper on fossil tadpoles in a special issue of the journal Fossil Imprint, available for free here.

Scientific research papers often owe their origins to chance events and may take years to come to fruition. Such is the case for “The Fossil Record of Tadpoles.” Dr. Gardner’s interest in fossil tadpoles was sparked in the early 1990s, when he recognized a 45 million year old tadpole fossil in the University of Florida Museum of Natural History’s fossil plant collection. He began working on a manuscript reviewing the fossil record of all tadpoles but it was set aside for decades, as he became busy with other projects – his PhD dissertation, for example. Fast forward a quarter century later, when Dr. Gardner was invited to contribute a paper to a volume commemorating the Czech palaeontologist Zdeněk Špinar (1916–1995). Knowing that Professor Špinar had published many papers on fossil tadpoles, Dr. Gardner decided to resurrect and update his dusty and almost forgotten manuscript.

One of the most characteristic features of anurans (frogs and toads) is their two-stage or biphasic life cycle consisting of a free swimming, vaguely fish-like, and typically herbivorous larval form (tadpole) that undergoes profound and rapid structural remodeling (metamorphosis) to become a four-legged, hopping, and exclusively carnivorous adult.

 

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Metamorphosis of tadpole into frog. Source.

 

Metamorphosed or adult frogs are moderately well represented in the fossil record; but many people are surprised that tadpoles also appear. At first glance, tadpoles seem poor candidates for fossilization: they are small, have only a rudimentary skeleton, and the tadpole phase of a frog’s life cycle generally lasts only a few months.

However, lakes provide an ideal environment for preserving those kinds of fossils, thanks to the fine-grained sediments in lake bottoms that can quickly cover and preserve carcasses. They are also ideal habitats for tadpoles.

 

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Figure 1: An indeterminate tadpole body fossil from the middle Eocene (approximately 45 million years ago) of Utah, USA. Head points towards top of figure and scale bar along left side is in 1 mm increments. Note the characteristic tadpole body form, consisting of a globular head + body and an elongate, narrow tail. This specimen lacks any indication of a skeleton; either the individual died at a young stage before the bones began ossifying or bones were present but did not preserve. Note the preserved eye pigments, brain, and digestive tract. This fossil is in the collections of the University of Florida Museum of Natural History, Gainesville, Florida.

 

Dr. Gardner’s review showed that the fossil record of tadpoles is better than most people realize. Tadpole body fossils have been known since the early 1800s, but in an interesting historical quirk, the first examples reported in 1828 were not recognized as tadpoles. It took another three years before tadpole fossils which were identified as tadpoles were published. Since then, fossil tadpoles have been reported from over 40 localities on most continents, except Antarctica and Australia. Those localities are in lake-style deposits and range in age from the Early Cretaceous to late Miocene (140–10 million years ago). A number of those localities have yielded multiple examples of different-sized tadpole body fossils, some so well preserved that their body outlines and details of internal structures like nerves and blood vessels can be seen.

 

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Figure 2. Examples of fossil tadpoles preserving bones and at different growth stages, both with their head pointing towards top of figure. Left: Pre-metamorphic tadpole of Shomronella jordanica (basal Pipimorpha) from the Early Cretaceous (about 130 million years ago) of northern Israel or Palestinian West Bank. This locality has yielded over 250 tadpoles of Shomronella. Right: Later stage tadpole undergoing metamorphosis of Palaeobatrachus vicentinus (Palaeobatrachidae) from the middle or late Oligocene (about 28 million years ago) of northeastern Italy. This is the only fossil tadpole known from the locality. The Shomronella fossil is in the collections of Hebrew University, Jerusalem, Israel and the Palaeobatrachus fossil is in the collections of Paläontologisches Museum, Humboldt University, Berlin, Germany; both photographs are courtesy of Prof. Zbyněk Roček (Prague, Czech Republic).

 

Size series of tadpole fossils from the same species are especially valuable because they provide large enough samples for palaeontologists to trace patterns of growth and metamorphosis in fossil frogs (the human equivalent would be having examples of everything from a baby to a teenager). The tadpole fossil record demonstrates that the distinctive tadpole body form and lifestyle and its astounding metamorphosis into a four-legged and hopping adult are ancient attributes of frogs.

This fish-like larval form can appear similar to other animals, such as fish and insects. In addition to reviewing the fossil record of tadpole body fossils, Dr. Gardner also examined reports of other fossils that have been interpreted as tadpoles. Those include 385 million year old larval fish fossils from the Middle Devonian of Scotland, a recently metamorphosed and 250 million year old skeleton of a proto-frog from the Early Triassic of Madagascar, and a piece of 20 million year old amber from the Dominican Republic containing what may be a tadpole hatching from an egg. Dr. Gardner provided the evidence against interpreting most of these fossils as tadpoles, although some, such as the Dominican amber, are ambiguous.

This paper and a second paper by Dr. Gardner on North American frogs from the Campanian titled “The Hopping Dead” (proof that scientists have a sense of humour) are available here. Fossil Imprint is an open access journal.

One of the most intriguing and enduring aspects of dinosaurs is their extinction at the end of the Cretaceous Period. After decades of research into this topic, most palaeontologists can agree on several details regarding the dinosaur mass-extinction. First, the extinction was due, at least in part, to an asteroid impact with the Earth at the end of the Cretaceous. Second, not all dinosaurs went extinct at the end of the Cretaceous. A group of small, feathered, and very specialized dinosaurs survived, and actually thrived – today we just call these birds.

Despite the relative agreement on these areas, there is still ongoing debate between palaeontologists regarding other aspects of the end-Cretaceous mass extinction. Two of these hotly debated questions include:

  1. Was the dinosaur extinction a sudden, catastrophic event, or were dinosaurs already on the decline prior to the impact?
  2. Why did birds survive the extinction when so many closely related, and very similar, dinosaur groups died out completely?

A new scientific article published today in the journal Current Biology investigates these questions. The scientific team was led by Derek Larson, Assistant Curator at the Philip J. Currie Dinosaur Museum, Wembley, Alberta, who completed the research as a PhD student at the University of Toronto. Also on the team are co-authors Dr. Caleb Brown of the Royal Tyrrell Museum of Palaeontology, Drumheller, and Dr. David Evans of the Royal Ontario Museum, Toronto.

The team concentrated on a group of small meat-eating dinosaurs known as maniraptorans – a group that includes modern birds, and dinosaurs like Velociraptor and Dromaeosaurus. Because these dinosaurs are smaller, rare, and generally more incomplete than their larger counterparts, their response to the end-Cretaceous extinction has been less well-studied. Due to the rarity of well-preserved skeletons, the team decided to use teeth; specifically, they measured the teeth and tracked how they changed through time. These dinosaurs (like sharks today) constantly shed teeth throughout their lifetime, so as a result, one animal could contribute hundreds of teeth to fossil record. Teeth are also very useful, because their shape is related to the diet of the animal. Look at an animal’s teeth, and you get a good idea of what it eats. Despite the rarity of complete skeletons, the team had many teeth to sample, and in the end they were able to measure more than 3,000 teeth from four different groups of maniraptorans. These teeth did not come from one fossil deposit, but actually spanned rocks for the 18 million years preceding the Cretaceous mass-extinction.

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Figure 1: Maniraptoran Teeth – This image depicts representative teeth from the four groups of bird-like dinosaurs (including toothed birds) analyzed in this study, with enlarged images of tooth serrations. Scale = 1 mm. Photo credit: Don Brinkman. Modified from Larson et al. 2010. Can. J. Earth Sci. 47: 1159-1181.

 

The ultimate goal of the project was to assign all of these teeth to successive time bins, and then track how their shape changed through time right up to the extinction event. If these dinosaurs were in steady decline, we would expect the variety of tooth shapes to decrease up to the extinction event, but if the extinction was sudden, the tooth shapes would be relatively constant through time. After crunching the numbers, the end result is that the disparity of the teeth (a fancy way of saying how different they are from each other in terms of shape) shows no decline leading up the extinction event. This means that, at least for the small meat-eating dinosaurs, the extinction was sudden.

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Figure 2: Tooth Disparity Through Time – A plot of tooth disparity (shape variation) thought the last 20 million years of the Cretaceous from the four groups of bird-like dinosaurs analyzed in this study. Image credit Larson et al., 2016 Current Biology.

But what does this research say about why birds survived the extinction? After looking at so many teeth, the team realized that the difference might be that those birds that survived the extinction did not have teeth, but had toothless beaks. This means that while most of these small dinosaurs with sharp teeth needed to eat meat regularly, the beaked birds might have been able to eat seeds.

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Figure 3: Cretaceous Bird-Like Dinosaurs – A number of bird-like dinosaurs reconstructed in their environment in the Hell Creek Formation at the end of the Cretaceous. Middle ground and background: two different dromaeosaurid species hunting vertebrate prey (a lizard and a toothed bird). Foreground: hypothetical toothless bird closely related to the earliest modern birds. Image credit: Danielle Dufault.

This is important because seeds are very good at lying dormant for long periods of time. If the ecosystems collapsed following the impact, and most resources were limited, there would still have been lots of seeds to eat. The same thing is seen today—when a forest fire clears out a section of forest, the first birds to return to the area are seed-eaters. To test this idea, the team mapped seed-eating diets onto a family tree of birds and showed that many of the bird groups that survived the extinction would likely have had ancestors that ate seeds. Whether or not this idea holds up over time will depend on future scientists finding more fossil birds and testing these ideas.

 

A link to the press release is available here: https://dinomuseum.ca/wp-content/uploads/2016/04/Larson-2016-Bird-Dinosaur-Press-Release-PJCDM.pdf

A link to the scientific paper is available here: http://www.cell.com/current-biology/fulltext/S0960-9822(16)30249-4

Reference: Larson, D.W., Brown, C.M., and Evans, D.C. 2016. Dental disparity and ecological stability in bird-like dinosaurs prior to the end-Cretaceous mass extinction. Current Biology 26, 1–9. http://dx.doi.org/10.1016/j.cub.2016.03.039

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