Archive

Tag Archives: science

The actinopterygians, or ray-finned fishes, are a substantial and significant component of modern vertebrate (animals with backbones) diversity. Ray-finned fishes are bony and have paired fins that are supported by rays (the actinosts) that insert directly in the body. Examples of modern ray-finned fishes include trout, eels, and bettas. Despite their prevalence today, the early evolution of this group is poorly understood compared to other major groups, driven by a lack of informative fossil data.

In his talk, Conrad Wilson explains how recent work on Early Carboniferous fossil sites from Nova Scotia and around the world provide new insight into the evolution of this group and how the development of the modern vertebrates may have been influenced by the mass extinction at the end of the Devonian Period (419 – 359 million years ago).

Mosasaurs were large, flipper-bearing swimming lizards from the age of the last dinosaurs, about 100–66 million years ago. Typically reaching the size of a pickup truck in length—and some nearly twice as long—over 70 mosasaur species are reported today based on the fossils collected from all over the world. Out of this highly diverse assemblage, halisaurine mosasaurs were small and seemed less well adapted to life in water since they lacked the well-developed flippers and tail fin of their larger contemporaries. Yet these small mosasaurs became increasingly more common in the fossil record towards the end of the Cretaceous, indicating their evolutionary success alongside their larger, fast-swimming cousins.

In his talk, Dr. Takuya Konishi, from the University of Cincinnati, explains why a recently discovered skull from Japan sheds new light on halisaurine mosasaurs’ potential survival strategy: that halisaurines evolved a pair of large, forward-facing eyes that would have increased their ability to see in the dark, allowing them to hunt at night.

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.

Montanoolithus_04_201409181406_1800

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.

There are many individuals in the Royal Tyrrell Museum of Palaeontology’s thirty-year history who have contributed to its success as Canada’s dinosaur museum. Maurice Stefanuk (1924-2016) was one of the Museum’s first technicians and research assistants who worked on many of the original specimens that are on display today in our Dinosaur Hall. Born and raised in Drumheller, Alberta, Maurice spent his childhood exploring the badlands. During one outing, he found a large carnivorous dinosaur tooth—a small discovery that sparked a life-long interest in fossils from the area.

During World War II, Stefanuk served as a sonar operator in the Royal Canadian Navy in the Battle of the North Atlantic protecting vital transport convoys from German U-boats. He made twenty-six dangerous transits from Canada to England.  In the fall of 1982, he joined the Royal Tyrrell Museum team, helping build exhibits as a dinosaur fossil preparator. After the Museum opened in 1985, he took field photographs of dinosaur quarries being excavated along the Red Deer River north of Drumheller and hiked the rugged badlands relocating them for Toronto-based palaeontology legend Dr. Loris S. Russell. New information learned from these dozens of sites was used in a recently published dinosaur biostratigraphic study.

Feb 8- Albertosaurus Skull

His biggest contribution to science was the discovery of two of the best skeletons of the comparatively rare tyrannosaur Albertosaurus (the Museum’s iconic symbol). One was discovered in 1973 east of Trochu, and the other in 1985, not far from the Museum. Both important specimens have been utilized in a number of displays and landmark scientific studies.

Albertosaurus has also become Alberta’s unofficial provincial dinosaur with representation on coins, stamps, and as part of the original Museum logo. When Canada House, home to the Canadian High Commission (and one of the most iconic buildings that make up Trafalgar Square in London, England), was undertaking some major renovations to reflect the art and culture of each province and territory, it was only natural for the Alberta Room to house an Albertosaurus. Just before he passed away, the cast of the skull of the second Albertosaurus Maurice discovered went on display.

Feb 8- Canada House

Image credit: High Commission of Canada in the United Kingdom.

Remarkably, during his time of service in the war, a picture of Maurice was taken on shore leave in Trafalgar Square, just a stone’s throw away from the future Canada House.  Of course he did not know it, but some seventy years after that picture was taken, a fossil he would find thirty years later would be displayed less than 100 metres from where that picture was taken.

Feb 8- Stefanuk

Speaker Series 2016: “Over the Heads of Dinosaurs – Pterosaurs!”

Pterosaurs (“winged reptiles”) appeared at the same time as the first dinosaurs, about 230 million years ago, and went extinct with the last of the dinosaurs 66 million years ago. Pterosaurs first appear in the fossil record as fully-evolved, specialized, flying animals, so their evolutionary origins are still a bit of a mystery. They ranged from the size of a sparrow all the way up to the largest flying animals known with wingspans of 10-12 metres. They were the first backboned animals to evolve active, powered, flapping flight, and did so many tens of millions of years before birds, and 170 million years before bats. Pterosaurs have been known for over 215 years (longer than for dinosaurs), but their skeletons are very delicate and their fossils are extremely rare. Most of what we know about pterosaurs comes from just a few sites scattered across the world where exceptional preservation of many individuals, soft-tissues such as skin and “fuzz,” or  three-dimensional skeletons give us detailed views of just a  few hundreds of thousands of years out of the 160 million years that pterosaurs lived.

This presentation by the Museum’s own Dr. Donald Henderson, Curator of Dinosaurs, introduces pterosaurs and highlights many of their exceptional fossils that have been found in the past twenty years, and explains how our understanding of these mysterious animals has dramatically improved over this short time.

Illustraion by Bob Nicholls (c) 2014.

Illustration by Bob Nicholls (c) 2014.

In the scientific community, art serves as a visual source of influential enlightenment, sparking the curiosity of the general public and researchers alike. The palaeoart entitled “Double Death” by Bob Nicholls depicts an exciting contest between two large theropod dinosaurs, Carcharodontosaurus saharicus, fighting over which one will get to eat a medium-sized sauropod dinosaur.

The concept for this picture originally stemmed in the late 1990s when Nicholls watched two birds jointly holding a piece of food. He then translated this idea into a dramatic piece of fleshed out digital art using dinosaurs. The dynamism in the resulting illustration prompted Dr. Donald Henderson, Curator of Dinosaurs, to ask “Could these two theropod dinosaurs REALLY lift a dinosaur almost as big as themselves and not fall over?”

To answer this question, Dr. Henderson conducted a biomechanical analysis using three-dimensional digital models to assess whether a pair of C. saharicus could successfully lift a medium-sized sauropod and not lose balance.

“I calculated how heavy each of the participants were, the two C. saharicus and the sauropod.  I also had to know where their centre of weight was.”

With the body mass and centre of mass determined for the C. saharicus, it turns out that a single animal weighing six tonnes could lift two and a half tonnes and not fall over. This two and a half tonnes represents about 40% of the body weight; however, the limb bones of animals in general can easily experience forces equal to two to three times total body weight when walking or running, so the additional 40% is well within the capacity of the limbs. It would appear that two C. saharicus could, between them, lift a five-tonne dinosaur without difficulty.

This led to two more questions: “Are the neck muscles strong enough to hold up a tonne or two of weight?” and “Are the jaw muscles strong enough to hold up a tonne or two of flesh?”

Estimating the jaw and neck muscle strengths of extinct dinosaurs begins by looking at the sizes of the attachment areas of the various muscles on the fossilized bones. Estimates of the cross-sectional areas of the muscles of interest are then determined. From looking at the muscles in living backboned animals today, we can see that skeletal muscles all have about the same force generating capacity, and the total force is related to the cross-sectional areas of the muscles. Applying these observations and a known muscle tension factor, we can calculate a probable lifting/holding force for the muscles of interest.

The jaws muscles were found to be able to exert sufficient force to hold 512 kg, but the neck muscles would only have been able to support 424 kg. This leads to the neck muscles being the limiting factor, and that two C. saharicus could only lift an animal weighing about 850 kg. The apparent excess capacity of the jaw muscles suggests that a high bite force was important for puncturing and pulling apart large prey items. The large body size of C. saharicus, in comparison to the smaller holding and lifting abilities of the neck and jaws, would have provided a stable, not-easily-toppled platform for manipulating small, struggling prey items.

“The animal ended up being a little bit smaller than the one Bob had done in his illustration, but the basic idea is fine. I just used basic first-year physics to work that out.”

The research conducted by Dr. Henderson was published in the August issue of The Anatomical Record along with the scientific illustration by Bob Nicholls.

“Our ideas have changed, but we still need the artists to bring these things to life, to make them more than just a collection of bones. These were real animals that lived in a real environment.”

Speaker Series 2015: “Money for Nothing—Three Decades of Research at the Royal Tyrrell Museum of Palaeontology”

This year marks the thirtieth anniversary of the Royal Tyrrell Museum of Palaeontology. In the January 29 edition of the 2015 Speaker Series, Dr. Jim Gardner, Curator of Palaeoherpetology, reflects on the history of the Museum and the accomplishments of its research program.

Since its opening in 1985, the Museum has become one of Alberta’s must-see tourist attractions, a significant contributor to the local economy, and one of the premier palaeontological research institutions in the world. Although the international palaeontological community is familiar with much of the scientific research that has been generated by the Museum’s scientists, many of the stories and accomplishments of the research program are less well known to the general public. Dr. Gardner walks us through how the scientific research done by staff, and by other scientists and students using the Museum’s extensive fossil collection, drives all aspects of the Museum’s activities.

 

The Royal Tyrrell Museum’s Speaker Series talks are free and held every Thursday from January to April 2015 at 11:00 a.m. in the Museum auditorium. Please visit the website for more information about upcoming speakers.

%d bloggers like this: