Police have arrested a Toronto woman in connection with three recent homicides and investigators say that they believe two of the victims may have been 'randomly targeted.'
Why do only mammals have tusks? Study traces their surprising origins
Tusks are a striking feature of many animals -- elephants, hippos, warthogs, walruses -- and are often sought-after by humans.
But no birds, fish or reptiles today sport this extreme and ever-growing bit of anatomy. Only mammals do, even though they weren't the first tusked creatures. It is an ancient trait that predates dinosaurs, a new study has found.
"We were able to show that the first tusks belonged to animals that came before modern mammals, called dicynodonts," said Ken Angielczyk, a curator at Chicago's Field Museum and an author of the new study, in a news release. "They're very weird animals."
Ranging from the size of a rat to elephantine, the dicynodonts lived from about 270 million to 201 million years ago. While their closest living relatives are mammals, they looked more reptilian, with turtle-shaped heads.
Dicynodonts were the most abundant and diverse vertebrates before the rise of the dinosaurs, and they all had a pair of tusks protruding from their upper jaws.
Tusks versus teeth
Before digging into how exactly tusks evolved, the researchers had to define exactly what a tusk is and how it differs from a tooth -- something that had been ambiguous.
They determined that a tusk must extend from the mouth, consist solely of a substance called dentine and continue to grow throughout an animal's life -- even if it gets damaged. Teeth are also made from dentine. However, they are coated in enamel. This, along with their shape, makes them durable, but once adult teeth grow in, there's not much that can be done if they do break. They don't regrow.
"Enamel-coated teeth are a different evolutionary strategy than dentine-coated tusks -- it's a trade-off," said Megan Whitney, postdoctoral fellow at Harvard University's department of organismic and evolutionary biology. She was the lead author of the study.
The researchers then analyzed thin sections of 19 fossilized tusks of dicynodonts, representing 10 different species found in South Africa, Antarctica, Zambia and Tanzania. They also used micro-computerized tomography scans to examine how the fossils were attached to the skull, and whether their roots showed evidence of continuous growth. They found that while a few of the dicynodonts studied had true tusks, with no enamel, the rest had big teeth.
The scientists also found there wasn't a strict progression from non-tusks to tusks. Different members of the dicynodont family evolved tusks independently at different times, and some never evolved true tusks.
"I fully expected there to be a single moment in dicynodont evolutionary history where tusks evolved because that's the simplest explanation. However, we found convergent evolution of tusks later in dicynodont evolution," Whitney said. Convergent evolution is when similar features evolve independently in different species or different periods in time.
For tusks to evolve, they found that a flexible ligament attaching the tooth to the jaw was needed, as well as reduced rates of teeth replacement -- a combination of features that today is uniquely found in modern mammals.
"It all ladders up to giving us a better understanding of the tusks we see in mammals today," said Angielczyk, speaking of the research, which published in the journal Proceedings of the Royal Society B Biological Sciences.
CTVNews.ca Top Stories
NDP house leader laments 'agents of chaos' in precarious Parliament
NDP House leader Peter Julian says there's more his party wants to do in Parliament before the next election, but if the current dysfunction continues it will become a factor in how they vote on a confidence measure.
Former Colorado county clerk Tina Peters sentenced to 9 years for voting data scheme
A judge ripped into a Colorado county clerk for her crimes and lies before sentencing her Thursday to nine years behind bars for a data-breach scheme spawned from the rampant false claims about voting machine fraud in the 2020 presidential race.
A teen charged with the murder of another teen on Prince Edward Island last year has pleaded guilty to a lesser charge of manslaughter.
The jury tasked with determining if Canadian musician Jacob Hoggard sexually assaulted a young woman in northeastern Ontario eight years ago began deliberating Friday after nearly two weeks of testimony that saw the singer and his accuser give starkly different accounts of what happened.
A northeastern Ontario jury has started deliberating in Canadian musician Jacob Hoggard's sexual assault trial, we can now tell you what they weren't allowed to hear.
At least two people are dead and others are injured after a fire ripped through a century-old building in Old Montreal early Friday morning, sources told Noovo Info.
Canadian family stuck in Lebanon anxiously awaits flight options amid Israeli strikes
A Canadian man who is trapped in Lebanon with his family says they are anxiously waiting for seats on a flight out of the country, as a barrage of Israeli airstrikes continues.
Yazidi woman captured by ISIS rescued in Gaza after more than a decade in captivity
A 21-year-old Yazidi woman has been rescued from Gaza where she had been held captive by Hamas for years after being trafficked by ISIS.
Local Spotlight
Chantal Kreviazuk is set to return to Winnipeg to mark a major milestone in her illustrious musical career.
From the beaches of Cannes to the bustling streets of New York City, a new film by a trio of Manitoba directors has toured the international film festival circuit to much pomp and circumstance.
A husband and wife have been on the road trip of a lifetime and have decided to stop in Saskatchewan for the winter.
The grave of a previously unknown Canadian soldier has been identified as a man from Hayfield, Man. who fought in the First World War.
A group of classic car enthusiasts donated hundreds of blankets to nursing homes in Nova Scotia.
Moving into the second week of October, the eastern half of Canada can expect some brisker fall air to break down from the north
What does New Westminster's təməsew̓txʷ Aquatic and Community Centre have in common with a historic 68,000-seat stadium in Beijing, an NFL stadium and the aquatics venue for the Paris Olympics? They've all been named among the world's most beautiful sports venues for 2024.
The last living member of the legendary Vancouver Asahi baseball team, Kaye Kaminishi, died on Saturday, Sept. 28, surrounded by family. He was 102 years old.
New data from Greater Vancouver and the Fraser Valley shows a surge in supply and drop in demand in the region's historically hot real estate market.