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.

Figure 1

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.

Figure 2

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.

Figure 3

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

Salamanders are a group of amphibians that are easily recognized by their moderately elongate body and tail, two pairs of limbs, and smooth skin. Southern Alberta is home to two kinds of salamander: the tiger salamander on the plains (including in the Drumheller region) and the long-toed salamander in the foothills and Rocky Mountains. Most of the 700 living species of salamanders occur only in the Northern Hemisphere (e.g., North America, Europe, and Asia) and belong to modern families that originated within the last 100 million years. The prevalence of living salamanders in the Northern Hemisphere suggests salamanders originated and diversified there. By contrast, frogs (which are closely related to salamanders) are more globally distributed and much of their evolutionary history seems to have been centered in the Southern Hemisphere.

Although North American contains about one-half of the living species of salamanders and has an extensive fossil record (including in Alberta), much of what we know about the origins and early evolution of salamanders relies on fossils from older rocks dating back to the Middle Jurassic to Early Cretaceous (about 160 to 100 million years ago) in Europe and Asia. In Asia, ancient salamander fossils are known from Siberia in the northeast and from Middle Asia (Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan) and Kazakhstan in the southwest. In his talk, Dr. Pavel Skutschas from St. Petersburg State University, Russia reviews his work on fossil salamanders from those regions and discusses what those Asian fossils tell us about the early evolutionary history of salamanders.

While humans have been misidentifying fossils for thousands of years, right back to the primitive Britons with their Devil’s toenails (Gryphea bivalves), fairie hearts (heart urchins), and petrified serpents (ammonites), there are certain horrendous mistakes that the palaeontological community will never forget. Some are quite intentional, where fake fossils have been created to deceive innocent collectors and scientists; in other cases, a particular fossil has been completely misinterpreted as representing a different type of animal or even turned out not to be a fossil at all. Sometimes the animal has been reconstructed with parts of the body upside down, back to front or, in extreme cases, with the wrong head. Finally, there are times when an innocent fossil has been used to promote particular agendas or ideologies.

This talk counts down the top twelve fossil failures over two-hundred years and includes everything from Piltdown Man to plesiosaur heads, chimeric dinosaurs to Charnia. Prepare to be astonished by the audacity, gullibility, and simple carelessness of the people that have made those fossil misidentifications.

The Cretaceous-Palaeogene (K-Pg) mass extinction is one of the most famous extinction events in Earth’s history, most notably as it marked the end of the Age of Dinosaurs approximately 66 million years ago. Although it is widely known that dinosaurs were wiped out during this event, many other types of animals also went extinct at the same time, both in the oceans and on land, resulting in the disappearance of nearly seventy-five percent of all species on Earth. Despite frequent claims of “ground-breaking discoveries,” the exact details of the K-Pg mass extinction remain shrouded in mystery. Ongoing research by palaeontologists and Earth scientists aims to elucidate how rapidly species went extinct, the reason(s) why some species disappeared while others survived, and what was/were the cause(s) of the mass extinction event.

In this talk, the Museum’s own Dr. François Therrien, Curator of Dinosaur Palaeoecology, will present an overview of the current state of knowledge about the K-Pg mass extinction and attempt to answer the question: “What killed the dinosaurs?”

Although often incorrectly identified as a dinosaur, the iconic sail-backed Dimetrodon was actually an ancient ancestor of today’s mammals. Dating back to the Permian Period, 295-272 million years ago, Dimetrodon was one of the first top predators on land and had several characteristics that made it an efficient predator. Foremost among these was a mouth full of large, serrated teeth required for subduing and consuming prey.

In her presentation, Dr. Kirstin Brink from the University of British Columbia provides a close study of the teeth using both histology (cutting open the teeth and using a microscope to identify tissues and structure) and CT scans (to examine the shape of the tooth roots within the jaws). This research revealed many differences in tooth shape between different species of Dimetrodon, and how tooth shape changed over millions of years of evolutionary time. The shape of the teeth of Dimetrodon was also key in the re-identification of an enigmatic fossil collected in 1845 as Canada’s own species of Dimetrodon, Dimetrodon borealis.

How do scientists commemorate the career and accomplishments of their colleagues? Not with a party and gifts, but with a “Festschrift,” which is the publication of a special volume of scientific papers written and compiled in dedication to their colleague. Two former researchers at the Royal Tyrrell Museum of Palaeontology each have been honoured with their own Festschrifts: Philip Currie in 2001 and the late Betsy Nicholls in 2006. More recently, Royal Tyrrell Museum researchers have been organizing Festschrifts for deserving colleagues.

The newest addition is the March 2016 issue of the journal Palaeobiodiversity and Palaeoenvironments. Co-edited by Royal Tyrrell Museum researcher Jim Gardner and colleague Tomáš Přikryl (Czech Academy of Sciences and Charles University, Prague), this new Festschrift honours the Czech herpetologist Zbyněk Roček.

As summarized by the editors’ introductory article in the Festschrift, the honouree Zbyněk Roček has led an interesting life and career.

He was born soon after the end of the Second World War, in a small town in what was then Czechoslovakia. He grew up, did his schooling, and began his academic career under the communist regime that dominated all aspects of private and professional life across Eastern Europe in those grim Cold War years.

By the mid-1990s, circumstances had changed markedly: communism had collapsed across Eastern Europe, the former Czechoslovakia had peacefully split into the Czech Republic and Slovakia, and Prague (the capital of the Czech Republic and where Prof. Roček lived) once again was becoming a fashionable and vibrant European city.

For the first time in several generations, Eastern European scientists could freely interact and exchange ideas with colleagues in the West. That change resulted in a surge of new work and collaborations, which have benefited science immensely. In a manner familiar to many scientists, the way in which Prof. Roček’s academic career unfolded was due to a sequence of fortuitous events, helpful colleagues, and seized opportunities.

Originally intending to be an ornithologist (bird biologist), Zbyněk instead was encouraged to switch to herpetology (study of amphibians and reptiles), and he ultimately became a leading expert on the evolution and fossil record of frogs. During his nearly five decades long career, Prof. Roček has published numerous articles and books, taught several generations of zoologists, and continues to be an active researcher well into retirement.

Like any good Festschrift, Professor Roček’s volume reflects the breadth of his research interests. It contains nine papers about fish, amphibians, and reptiles, ranging in age from the earliest Mesozoic through to the present, and with near global coverage. Participation by a total of 23 authors, from 11 countries and at varying stages of their careers, attests to the esteem Prof. Roček has earned within the scientific community.

For the Royal Tyrrell Museum of Palaeontology, our participation in this volume continues our institution’s tradition of fostering international collaborative scientific research.

A1_12549_Cover page 1.indd

Cover of the March 2016 issue of “Palaeobiodiversity and Palaeoenvironments” containing scientific papers honouring the Czech palaeoherpetologist Zbyněk Roček. Cover image courtesy of “Palaeobiodiversity and Palaeoenvironments,” Springer-Verlag GmbH, Heidelberg.

For a limited time (until 30 April 2016), the publisher is generously providing free access to the entire volume at: http://link.springer.com/journal/12549/96/1/page/1

 

British Columbia’s Eocene Lakes and Forests: New Perspectives on Temperate Islands from a Past Greenhouse World

Dr. David R. Greenwood, Brandon University, Manitoba

During the early Eocene, about 55 to 50 million years ago, warm climates extended into Canada’s Arctic as far north as Ellesmere Island, supporting biologically rich forests of conifers, broadleaf trees, and a diverse fauna. In the south, climates were subtropical to tropical. In the 1890s, fossil palm fronds were routinely collected from Eocene-age rocks in what is now downtown Vancouver. Inland from Vancouver, however, are many other plant fossil sites that tell a story of a much cooler climate where the plant and animal fossils reconstruct Eocene forests with a temperate character, much like the Arctic Eocene forests.

In this talk, Dr. Greenwood discusses the history of study of these cooler highland Eocene fossil sites starting with J.W. and G.M. Dawson and important contributors from Canadian and U.S. universities over the 1950s to present day, highlighting how our understanding of the age, and the kind of questions being asked have changed as successive generations of palaeobotanists have studied the fossil leaves, seeds, fruits, flowers, and conifer cones. Once considered middle Eocene, these interior British Columbia fossil sites are now known to fall within the Early Eocene Climatic Optimum, a sustained period of globally warm climates from 52 to 50 million years ago. The plant fossils reveal ancient connections between East Asia and North America. Using case studies, Dr. Greenwood shows the early Eocene temperate forests of British Columbia were much more diverse than those of present day eastern North America, under climates not that different from modern-day Seattle and Portland.

 

 

 

 

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