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Fossilized Stomach Contents Reveal What Young Tyrannosaurs Ate

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Paleontologists in Canada have found a 75-million-year-old skeleton of a juvenile of the tyrannosaurid dinosaur Gorgosaurus libratus with the remains of two young individuals of the small dinosaur Citipes elegans in its abdominal cavity.

A juvenile of Gorgosaurus libratus feeding on Citipes elegans. Image credit: Julius Csotonyi / Royal Tyrrell Museum of Palaeontology / University of Calgary.

Tyrannosaurids are a group of carnivorous dinosaurs that dominated the ecosystems of Asia and North America near the end of the Cretaceous period, between 80 and 66 million years ago.

Among the largest land predators to have ever existed, they grew from meter-long hatchlings to multiton sizes (9- to 12-m long, 2,000 to 6,000 kg) over the course of their life span.

Juveniles were gracile with narrow skulls, blade-like teeth, and long slender hind limbs, whereas adults were robust with massive skulls and large incrassate teeth and were capable of generating bone-crushing bites.

These changes suggest that tyrannosaurids underwent a major dietary shift, in which juvenile and adult individuals occupied different ecological niches.

Fossil evidence reveals that dinosaurian megaherbivores (i.e., species with an adult mass of over 1,000 kg, including ceratopsids, giant ornithomimosaurs, hadrosaurids, and sauropods) were common prey items of large tyrannosaurids, a diet for which the necessary adaptations and bite forces only developed when individuals reached late juvenile or early subadult growth stages.

“Unfortunately, fossil evidence for diet in young tyrannosaurids is largely unknown, thus limiting our understanding of ontogenetic dietary shifts in these iconic predators,” said lead author Dr. François Therrien, a paleontologist at the Royal Tyrrell Museum, and colleagues.

Juvenile Gorgosaurus libratus preserving stomach contents: photographs of specimen in (A) right lateral view and (B) left anterolateral view; (C) interpretive illustration of specimen in right lateral view; skeleton consists of a nearly complete skull, the left side of the body and limbs, and a nearly complete pelvis; red rectangle delineates location of stomach contents; (D) histological photomicrograph of tibia showing the presence of five lines of arrested growths and two annuli (marked by asterisks), indicating that the individual was between 5 and 7 years old. Scale bars - 50 cm in (A-C) and 1 mm in (D). Image credit: Therrien et al., doi: 10.1126/sciadv.adi0505.

Juvenile Gorgosaurus libratus preserving stomach contents: photographs of specimen in (A) right lateral view and (B) left anterolateral view; (C) interpretive illustration of specimen in right lateral view; skeleton consists of a nearly complete skull, the left side of the body and limbs, and a nearly complete pelvis; red rectangle delineates location of stomach contents; (D) histological photomicrograph of tibia showing the presence of five lines of arrested growths and two annuli (marked by asterisks), indicating that the individual was between 5 and 7 years old. Scale bars – 50 cm in (A-C) and 1 mm in (D). Image credit: Therrien et al., doi: 10.1126/sciadv.adi0505.

In their research, the authors examined a well-preserved specimen of Gorgosaurus libratus found in Dinosaur Provincial Park in Alberta, Canada.

Gorgosaurus libratus was a tyrannosaur that lived 75 million years ago — several million years before Tyrannosaurus rex — in what is now southern Alberta,” they said.

“The age of this individual when it died has been estimated at between five and seven years old.”

“With an estimated body mass of 335 kg based on its thigh bone (femur) length, the juvenile would have been less than 13% of the body mass of an adult.”

The researchers found the partial remains of two small dinosaurs inside the stomach cavity of the Gorgosaurus libratus specimen.

“Before it died, the carnivore dismembered two young, bird-like herbivorous dinosaurs of the species Citipes elegans,” they said.

“Rather than swallowing its prey whole, the young tyrannosaur only ate the hind limbs (the meatiest parts of the body).”

“The prey were caenagnathid dinosaurs, similar to Oviraptor from Asia.”

The further study of the fossilized bones indicated that both Citipes elegans individuals were within their first year of life when they died.

“The rock within the ribcage was removed to expose what was hidden inside. The complete hind legs of two baby dinosaurs, both under a year old, were present in its stomach,” Dr. Therrien said.

Because the elements of the two individuals are at different stages of digestion, the scientists were able to conclude that Gorgosaurus libratus’ stomach contents represent two different meals, ingested hours or days apart.

The presence of two dinosaurs of the same species and age in the stomach contents, ingested at different times, suggests that young caenagnathids may have been among the preferred prey of juvenile gorgosaurs.

This specimen is the first to provide direct evidence that young gorgosaurs had different diets than their adult counterparts.

Based on tooth marks left on bones, adult gorgosaurs are known to have hunted megaherbivore dinosaurs, such as ceratopsians and hadrosaurs.

Adult gorgosaurs used their massive skulls and large teeth to capture large prey, bite through bone, and scrape and tear flesh from carcasses.

However, juvenile gorgosaurs weren’t built to hunt such large prey. Juveniles were lean, with narrow skulls, blade-like teeth, and long, slender hind limbs. They were ideally suited for capturing and dismembering small and young prey.

The evidence suggests that tyrannosaurs occupied different ecological niches over their lifetime.

As young tyrannosaurs grew and matured, they would have transitioned from hunting small and young dinosaurs to preying on large herbivores.

This dietary shift likely began around the age of 11, when the tyrannosaurs’ skulls and teeth started becoming more robust.

“It’s well-known that tyrannosaurs changed a lot during growth, from slender forms to these robust, bone-crushing dinosaurs, and we know that this change was related to feeding behavior,” said University of Calgary’s Dr. Darla Zelenitsky, co-author of the study.

“They appear to have gone from hunting prey like Citipes elegans (small fraction of their size) as teenagers to hunting megaherbivore dinosaurs (as large, or larger, than their size) as adults.”

The team’s paper was published in the journal Science Advances.

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François Therrien et al. 2023. Exceptionally preserved stomach contents of a young tyrannosaurid reveal an ontogenetic dietary shift in an iconic extinct predator. Science Advances 9 (49); doi: 10.1126/sciadv.adi0505

 

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‘Big Sam’: Paleontologists unearth giant skull of Pachyrhinosaurus in Alberta

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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.

On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.

They call it “Big Sam.”

The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.

It didn’t die alone.

“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.

She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”

“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.

The head alone, she said, is about the size of a baby elephant.

The discovery was a long time coming.

The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.

“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.

When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”

“It contains about 100 to 300 bones per square metre,” she said.

Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.

About a year ago, they found the second adult: Big Sam.

Bamforth said both dinosaurs are believed to have been the elders in the herd.

“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.

“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”

The genders of the two adults are unknown.

Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.

The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.

She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.

“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.

“It’s pretty exciting.”

This report by The Canadian Press was first published Sept. 25, 2024.

The Canadian Press. All rights reserved.

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The ancient jar smashed by a 4-year-old is back on display at an Israeli museum after repair

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TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.

Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.

Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.

The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.

The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.

It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.

Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.

Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.

Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.

Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.

Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.

The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”

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B.C. sets up a panel on bear deaths, will review conservation officer training

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VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.

Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”

Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.

“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.

B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.

Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.

Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.

Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.

“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”

Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”

“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.

Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.

“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.

This report by The Canadian Press was first published Sept. 9, 2024.

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