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New Research Shows Tyrannosaurus Rex Took Nearly 40 Years to Fully Grow

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A detailed analysis of 17 fossil specimens of tyrannosaurus rex indicates that this iconic dinosaur grew much more slowly than previously believed, reaching an adult weight of approximately 8 tons by around age 40. This challenges earlier assumptions about its life history.

tyrannosaurus rex holotype specimen at the Carnegie Museum of Natural History in Pittsburgh, USA. Image credit: Scott Robert Anselmo / CC BY-SA 3.0.

tyrannosaurus rex is renowned as one of the most iconic non-avian dinosaurs, continually captivating paleontologists and the public alike.

Previous growth studies proposed that this ancient predator could exceed 8 tons within just 20 years and live for nearly 30 years.

Utilizing advanced statistical algorithms, the new research examined bone slices under specialized lighting, uncovering hidden growth rings that previous studies had overlooked.

This analysis not only extended the growing season for tyrannosaurus rex but also suggested that by age 15, some specimens might not be complete individuals of tyrannosaurus rex, but instead could belong to other species or unique variants.

“This is the largest dataset ever collected regarding tyrannosaurus rex,” stated Holly Woodward, a professor at Oklahoma State University.

“Through studying the tree rings preserved in fossilized bones, we reconstructed the growth history of these magnificent creatures year by year.”

Unlike the annual rings found in tree stumps, the cross-sections of tyrannosaurus rex bones only record the final 10 to 20 years of an individual’s life.

“Our innovative statistical approach allowed us to estimate growth trajectories by synthesizing growth records from various samples. We examined every growth stage in greater detail than any prior studies,” explained Dr. Nathan Myhrvold, a mathematician and paleontologist at Intellectual Ventures.

“The resulting compound growth curves provide a more accurate representation of how tyrannosaurus rex matured and evolved in size.”

Rather than competing for dominance into adulthood, tyrannosaurus rex demonstrated a gradual and steadier growth pattern than previously assumed.

“The prolonged growth phase over 40 years likely enabled young tyrannosaurs to occupy various ecological roles within their environment,” said Dr. Jack Horner of Chapman University.

“This may explain how they maintained their status as apex carnivores at the end of the Cretaceous period.”

The team’s findings were published in the online journal Peer J.

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HN Woodward et al. 2026. Long-term growth and the extension of subadult development of the tyrannosaurus rex species complex revealed through expanded histological sampling and statistical modeling. Peer J 14: e20469; doi: 10.7717/peerj.20469

Source: www.sci.news

Tyrannosaurus Growth: Understanding the 40-Year Journey to Full Size

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Tyrannosaurus Rex: A Late Bloomer

Science Photo Library / Alamy

The largest analysis of Tyrannosaurus rex fossils reveals that this colossal Cretaceous predator took approximately 35 to 40 years to reach maturity, significantly longer than previously believed.

This research suggests that there may have been multiple species of Tyrannosaurus rather than just one, raising questions about whether small specimens attributed to juveniles might actually belong to a distinct species known as Nanotyrannus.

Before this study, it was assumed that Tyrannosaurus rex reached a maximum weight of 8 tons by around 20 years of age and could have a lifespan of only 30 years.

“Previous growth studies on Tyrannosaurus rex were conducted in the early 2000s and were based on a limited sample size of seven specimens,” explains Holly Ballard from Oklahoma State University. “This was not the researchers’ fault; it was the available data at the time.”

Through their recent study, Ballard and her colleagues analyzed thigh and tibia bones from 17 specimens ranging in age from juvenile to adult, making it the largest dataset for Tyrannosaurus growth ever collected.

The research team examined the microstructure of bone tissue, including growth rings formed annually, similar to tree rings. However, the earliest growth rings were often destroyed as the marrow cavity expanded, necessitating a greater number of specimens across overlapping growth stages.

“This is why our sample size and age distribution are so critical and set us apart from past studies,” Ballard emphasizes.

The analysis revealed that Tyrannosaurus rex grows more slowly than initially thought, with growth rates varying based on environmental factors.

However, determining the maximum age of Tyrannosaurus rex remains problematic, as animals cease to grow annual rings upon reaching maturity. “The most successful Tyrannosaurus likely lived to be around 40 years old, with very few individuals achieving that age,” Ballard notes. “In our sample, only two individuals reached full adult size.”

Interestingly, two other specimens exhibited slower growth, indicating they might belong to a different species, such as Nanotyrannus, or that they were possibly Tyrannosaurus rex that were sick or stunted due to environmental factors.

Lindsey Zanno from the North Carolina Museum of Natural Sciences describes this study as one of the most comprehensive investigations of Tyrannosaurus rex growth to date, building on her recent research suggesting that a small specimen from Montana might be a fully grown Tyrannosaurus rex around 20 years old, potentially named Nanotyrannus lansensis.

“I’m thrilled to finally have a growth curve for Tyrannosaurus rex that we can assert with confidence,” Zanno comments, especially regarding Nanotyrannus.

Thomas Carr from Carthage College in Wisconsin believes that this study will likely lead to the separation of Tyrannosaurus rex into different species and expects it to influence future dinosaur research significantly.

“We anticipate that growth estimates for other dinosaurs will undergo reassessment,” Carr states. “Overall, this could transform our understanding of dinosaur growth and development across the spectrum.”

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Nanotyrannus: Dinosaur Skeleton Resolves Long-Standing Debate Over ‘Small Tyrannosaurus’ Fossil

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Artist’s interpretation of the pack Nanotyrannus assailing a young tyrannosaurus

Anthony Hutchings

Fossils previously thought to belong to a juvenile tyrannosaurus rex have been identified as a fully mature carnivore of a distinct species, resolving a long-standing debate in paleontology.

This controversy originated from a skull unearthed in the Hell Creek Formation in Montana during the 1940s, which was initially identified as gorgosaurus. It was later proposed to be a juvenile tyrannosaurus. In 1988, other researchers posited that the fossil represented an adult of a smaller related species, which they designated Nanotyrannus lansensis.

Since then, a number of additional fossils classified as Nanotyrannus have been discovered, although many paleontologists contend that they are merely tyrannosaurus juveniles.

Now, researchers have examined a complete skeleton for the first time, providing compelling evidence that Nanotyrannus is indeed a separate species.

The skeleton is among a pair of specimens known as “Dueling Dinosaurs,” found by private fossil hunters in 2006, which includes a triceratops and what was initially believed to be a juvenile T. rex buried approximately 67 million years ago.

It was only in 2020, when the fossil came into the possession of the North Carolina Museum of Natural Sciences, that paleontologists could conduct a thorough analysis of it.

“Upon receiving the specimen, we recognized it was extraordinary,” remarks Lindsey Zanno from the North Carolina Museum of Natural Science. “We had no inkling it would radically alter decades of research concerning the world’s most renowned dinosaur.”

Mr. Zanno collaborated with his colleagues, including James Naples, a postdoctoral researcher at Stony Brook University in New York. She had initially supported the juvenile tyrannosaurus theory but was compelled to reevaluate her stance based on the findings.

“Nanotyrannus displays unique nerve and sinus patterns, a greater number of teeth, larger hands, and shorter tails. These traits remain consistent as the species develops from juvenile to adult,” she notes.

Lindsay Zanno with the proposed Nanotyrannuslansensis skeleton

North Carolina State University

Zanno and Napoli’s examination of the dinosaur’s limb bones confirmed that it was a fully mature specimen, approximately 20 years old, weighing around 700 kilograms and measuring about 5.5 meters in length. “This is roughly one-tenth the weight of an adult human and half the length of a tyrannosaurus,” Zanno explains.

Additionally, Zanno and Napoli reanalyzed 200 tyrannosaur fossils and concluded that another nearly complete skeleton, known as Jane from the Hell Creek Formation, is misclassified as a tyrannosaurid fossil. They propose that Jane is actually a new species within this genus, designated Nanotyrannus letaeus.

“Although we possess only one skeleton of N. Retheus, its anatomy suggests it was part of a larger species,” remarks Zanno. “The configuration of the palatal sinuses and the shape of the bone behind the eye are distinctive.”

Proposed Nanotyrannus lansensis skull features more teeth than the tyrannosaurus skull.

Matt Zeher/North Carolina Museum of Natural Science

Scott Parsons, a researcher at the South Carolina State Museum, asserts that this latest study clarifies the debate surrounding Nanotyrannus being its own genus and species.

“In my opinion, Nanotyrannus was among the most formidable dinosaur predators, and being pursued by one would be quite a terrifying experience,” Parsons remarks, noting its long legs and fearsome thumb claws.

“In essence, we can compare Nanotyrannus and tyrannosaurus to modern-day cheetahs and lions. While they shared a similar overall anatomy, they had distinct hunting strategies.”

Thomas Carr from Carthage College in Wisconsin has expressed that the new findings are “quite definitive” that the dueling dinosaur specimen represents an almost adult species, one that differs from tyrannosaurus.

Additionally, Holly Ballard from Oklahoma State University, who led the 2020 research, stated that there is “no contention” regarding the team’s conclusion that the fossil belonged to an individual nearing adult size.

However, neither Ballard nor Carr are fully convinced that the other fossil, Jane, constitutes a new species of Nanotyrannus. “Jane is still maturing and large,” emphasizes Ballard, suggesting it may be a new taxon rather than a juvenile tyrannosaurus. “We’re returning to the old debates,” Ballard laments.

“Moreover, in the Hell Creek Formation, if there are numerous small tyrannosaurs in circulation, where are the juvenile tyrannosaurus? ” Kerr questions, stating that it complicates the fossil record. “We simply haven’t uncovered enough tyrannosaurs to fully elucidate what was occurring during the growth phases of the tyrannosaurids in the Hell Creek Formation.”

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Unveiling the King: New Insights into the Enigmatic Origins of Tyrannosaurus Rex

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The genus Tyrannosaurus had its direct ancestors migrate from Asia over 70 million years ago, according to a groundbreaking study conducted by researchers at University College of Paleontologists in London.

Tyrannosaurus Rex evolved in North America, while its direct ancestors originated from Asia. Image credit: Pedro Salas/Sergey Krasovskiy.

This research, led by Cassius Morrison, a Ph.D. student at University College London, indicates that the rapid increase in the size of tyrannosaur dinosaurs and their close relatives, the Megaraptors, coincided with a global climate cooling that followed a temperature peak 92 million years ago.

This finding suggests that Tyrannosaurus Rex and its relatives may have been better adapted to cooler climates compared to other dinosaur groups at the time, likely due to their feathers and warmer physiology.

The geographical origins of Tyrannosaurus Rex have been a topic of intense debate,” stated Morrison.

“Paleontologists remain divided over whether their ancestors originated from Asia or North America.”

“Our modeling indicates that the “grandparents” of Tyrannosaurus Rex likely migrated to North America from Asia, crossing the Bering Strait between modern-day Siberia and Alaska.”

“This aligns with prior research showing that Tyrannosaurus Rex shares a closer relation to Asian relatives like Turbosaurus than to North American relatives such as Daspletosaurus.

“Numerous Tyrannosaurus Rex fossils have been found in North America, but our findings imply that the direct ancestors of this group may not yet have been unearthed in Asia.”

Paleontologists concluded that Tyrannosaurus Rex actually evolved in North America, particularly in Lalamidia, and was widely distributed across the region.

This conclusion contradicts last year’s findings suggesting that Tyrannosaurus mcraeensis, discovered in New Mexico, could be North American ancestors of Tyrannosaurus Rex from 3 to 5 million years ago. The team argued that the fossils of Tyrannosaurus mcraeensis were not properly dated.

For this study, researchers examined the migratory patterns of Tyrannosaurus and its relatives across the globe.

They employed mathematical models that represented fossils, dinosaur evolutionary trees, as well as the geography and climate of the era.

Importantly, the model addressed gaps in the fossil record and factored in uncertainties in the calculations.

Megaraptors are considered one of the most enigmatic large carnivorous dinosaurs.

In contrast to Tyrannosaurus Rex, they evolved slender heads and limbs as long as human height, with claws measuring up to 35 cm (14 inches).

Scientists conclude that Megaraptors were more widely distributed than previously thought, first appearing in Asia around 120 million years ago, spreading to Europe, and likely reaching Gondwana (encompassing regions of present-day Africa, South America, and the Southwest).

This suggests that Megaraptors inhabited regions like Europe and Africa, where no fossils had been found before.

They may have adapted differently from their Tyrannosaurus relatives, perhaps utilizing their claws for hunting instead of relying on powerful bites.

In South Gondwana, they could have preyed on small sauropods, while Tyrannosaurus Rex hunted large herbivores such as Triceratops, Edmontosaurus, and Ankylosaurus.

Both Tyrannosaurids and Megaraptors grew to enormous sizes nearly simultaneously as the climate cooled after the Cretaceous thermal peak 92 million years ago.

This rapid growth occurred following the extinction of other giant carnivorous dinosaurs, Carcharodontosaurids, which left a void at the top of the food chain.

The authors suggest that both Tyrannosaurus and Megaraptor could utilize cooler temperatures more effectively than their rival dinosaur groups.

By the end of the dinosaur age, Tyrannosaurus Rex weighed up to 9 tons (similar to very large African elephants and light tanks), while the Megaraptor reached lengths of up to 10 meters.

“Our findings illuminate the emergence of the largest tyrannosaurs in North and South America during the Cretaceous period and how they thrived by the end of the dinosaur epoch,” remarked Charlie Scheller of the University of London.

“They may have achieved their massive size to fill the ecological role left by the similarly large Carcharodontosaurid theropods that went extinct approximately 90 million years ago.”

“This extinction likely removed any ecological barriers that previously constrained the growth of tyrannosaurs.”

“Around 120 million years ago, Megaraptors were part of a diverse array of dinosaur species,” stated Dr. Mauro Alanciagaroland, a paleontologist at the Museum of Natural Sciences and the Bernardino Rivadavia Museum in Argentina.

“As the Cretaceous period progressed and the continents began to drift apart, these predators became increasingly specialized.”

“Such evolutionary shifts prompted them to adapt to more specific habitats.

“In areas like Asia, Megaraptors were ultimately replaced by Tyrannosaurus, but in regions like Australia and Patagonia, they became apex predators, dominating these ecosystems.”

This study is published in the journal Royal Society Open Science.

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Cassius Morrison et al. 2025. The Rise of the King: the origins of Gondwanan and the evolution of the Megaraptor dinosaurs. R. Soc. Open Sci. 12(5): 242238; doi: 10.1098/rsos.242238

Source: www.sci.news

A new type of Tyrannosaurus found in China

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Paleontologists have discovered the fossil of a deep-snouted tyrannosaur dinosaur. Asiatyrannus shui Southeast China.

Fossil remains Asiatyrannus shuiThe first deep-snouted tyrannosaur discovered in Ganzhou, southeastern China. Image courtesy of Zheng others., doi:10.1038/s41598-024-66278-5.

Asiatyrannus shui It lived on Earth during the Late Cretaceous period, about 69 million years ago.

This new species is TyrannosaurinaeIt is one of two extinct subfamilies. Tyrannosauridae — The most derived group of the superfamily Tyrannosauroidea.

“Tyrannosauroidea are the most distinctive, best known and most intensively studied group of dinosaurs, represented by around 30 species,” said Dr Wenjie Chen from the Zhejiang Museum of Natural History and colleagues.

“The oldest tyrannosaurs appeared in the Middle Jurassic period, about 165 million years ago.”

“They emerged as apex predators in their respective ecosystems in Asia and western North America during the last 20 million years of the Cretaceous period.”

“The large body size and deep snout are characteristic of ecologically dominant Late Cretaceous tyrannosaurids.”

Asiatyrannus shui It is a small to medium-sized tyrannosaurine dinosaur with a skull length of 47.5 cm (18.7 in) and an estimated total length of 3.5 to 4 m (11.5 to 13.1 ft).

“The new species, Kienzosaurus “Other large tyrannosaurine dinosaurs at similar developmental stages have been discovered,” the paleontologists noted.

In September 2017, a nearly complete skull and a partially detached postcranial skeleton of a new species of dinosaur were discovered at a construction site in the Nanxiong Formation in Shahe Town, Ganzhou City, Jiangxi Province, China.

“Asiatic Tyrannus and Kienzosaurus “Different skull proportions and body sizes suggest that they may have occupied different ecological niches,” the researchers say.

“In the Campano-Maastrichtian of East/Central Asia and Laramidia, the large carnivore guild was dominated by tyrannosaurids, and adult medium-sized predators were rare or absent.”

“The scientists interpreted that the ‘missing intermediate-sized’ niche in the theropod guilds of Laramidia and Asia during the Late Cretaceous may have been assimilated by juvenile and subadult tyrannosaurids.”

“In southeastern China, Kienzosaurus It undoubtedly held the position of apex predator, Asiatic Tyrannus May represent a niche for small to medium-sized theropods between large and small theropods. Kienzosaurus and a diversified set of small oviraptorosaurs.”

of Investigation result Published in this week’s journal Scientific Reports.

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W. Zheng others2024. The first deep-snouted tyrannosaur from the Late Cretaceous, discovered in Ganzhou, southeastern China. Scientific Reports 14, 16276; doi: 10.1038/s41598-024-66278-5

Source: www.sci.news

How intelligent were the Tyrannosaurus and other giant theropod dinosaurs?

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Large theropods were as intelligent as reptiles, but not as smart as apes, according to a new study led by paleontologists at the University of Bristol.

tyrannosaurus rex Holotype specimen at the Carnegie Museum of Natural History in Pittsburgh, USA. Image credit: Scott Robert Anselmo / CC BY-SA 3.0.

in study Vanderbilt University paleontologist Suzana Herculano-Hausel announced last year that dinosaurs tyrannosaurus It had a huge number of neurons and was much more intelligent than expected.

She argued that these high numbers of neurons could directly inform intelligence, metabolism, and life history. tyrannosaurus In some habits they were more like monkeys.

Theropod dinosaurs of North America from the Late Cretaceous tyrannosaurus “It is an apex predator, one of the largest, heaviest, and most powerful (in terms of bite force) terrestrial carnivores ever known,” said Dr. Heidi George from the University of Bristol.

“Recently, Dr. Herculano Hausel proposed that we should add primate-level intelligence to great apes. tyrannosaurusAlready an impressive predation history, based on high estimates of the number of neurons in the forebrain. ”

“This conclusion arose from the paradigm that neurological variables inferred from endocasts can be used to infer metabolic parameters, behavior, and lifespan of fossil species.”

In the new study, Dr. George and his co-authors took a closer look at the techniques used to predict both brain size and number of neurons in dinosaur brains.

They found that previous assumptions about the size of dinosaur brains and the number of neurons they contained were unreliable.

This new study follows decades of analysis in which paleontologists and biologists studied the size and anatomy of dinosaur brains and used these data to infer behavior and lifestyle.

Information about dinosaur brains comes not only from the shape of the brain cavity itself, but also from its mineral fillings, called endocasts.

The authors found that their brain size, particularly the size of the forebrain, was overestimated, and thus the number of neurons was also overestimated.

Furthermore, we show that estimates of neuron number are not a reliable guide to intelligence.

“To reliably reconstruct the biology of a long-extinct species, researchers need to examine multiple lines of evidence, including skeletal anatomy, bone histology, the behavior of living relatives, and trace fossils.” the researchers said.

“To determine the intelligence of dinosaurs and other extinct animals, it's best to use a wealth of evidence, from gross anatomy to fossilized footprints, rather than relying solely on estimates of neuron counts,” Dr. Heidi said. added.

“We argue that it is not a good idea to predict the intelligence of extinct species when only the number of neurons reconstructed from endocasts is sufficient,” said Dr. Kai Kasper, a paleontologist at Heinrich Heine University. Ta.

“Neuron number is not a good predictor of cognitive ability, and using neuron number to predict intelligence in long-extinct species can lead to very misleading interpretations,” Mikel Crusafont Catalan Paleontologist said Dr. Ornella Bertrand, a paleontologist at the Institute.

“The possibility is that tyrannosaurus The possibility that they were as intelligent as baboons is both fascinating and frightening, and has the potential to transform the way we view our past,” said Dr Darren Naish, a palaeontologist at the University of Southampton. .

“But our study shows how all the data we have contradicts this idea. They were more like smart giant crocodiles, which was just as fascinating. ”

of result Published in anatomical records.

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Kai R. Kasper other.How clever! tyrannosaurus• Examine claims about the extraordinary cognitive abilities of dinosaurs and the application of neuron number estimation in paleontological research. anatomical records, published online on April 26, 2024. doi: 10.1002/ar.25459

Source: www.sci.news

Huge new tyrannosaurus rex found in New Mexico

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discovery of Tyrannosaurus macraiensissister species of the famous one tyrannosaurus rexsuggests that tyrannosaurid dinosaurs originated from Laramidia, an island continent that existed between 100 million and 66 million years ago and stretched from present-day Alaska to Mexico.

rebuilding the life of Tyrannosaurus McClain. Image credit: Sergey Krasovskiy.

“Tyrannosaur dinosaurs were the dominant predators of North America and Asia during the Late Cretaceous period,” said Dr. Sebastian Dalman of the New Mexico Museum of Natural History and Science and his colleagues.

“Evolved from a diminutive ancestor in the mid-Cretaceous period, became an apex predator in the late Cretaceous period, and eventually tyrannosaurus”

“tyrannosaurusWith a sturdy skeleton and powerful bone-crushing jaws, this animal was the dominant carnivore of the late Maastrichtian period in western North America. ”

“Grows up to 12 meters long and weighs 10 tons, tyrannosaurus It was the largest terrestrial predator of its time, and perhaps of all time. ”

“where and when Tyrannosaurini (tyrannosaurus and relatives) origin remains unknown. Competing hypotheses place its origin in Asia or western North America (Laramidia). ”

The newly identified species is Tyrannosaurus McClainlived in what is now the United States 71 million to 73 million years ago, or 5 million to 7 million years ago. tyrannosaurus.

The fossilized partial skull of this dinosaur was discovered in the Hall Lake Formation in New Mexico.

Although the specimens were initially assigned; tyrannosaurus and its size is tyrannosaurusPaleontologists have proposed that the specimen belongs to a new species, due to several subtle differences in the shape and joints between the specimen and the skull. tyrannosaurus.

Analysis of the relationship between Tyrannosaurus McClain and other theropod dinosaur species. Tyrannosaurus McClain It may have been a sister species of tyrannosaurusmaking it the closest known relative. tyrannosaurus.

The authors suggest that Tyrannosaurini may have originated in southern Laramidia, an island continent that existed between 100 million and 66 million years ago and stretched from present-day Alaska to Mexico.

Additionally, Tyrannosaurus, along with other giant dinosaurs of southern Laramidia such as ceratopsians, hadrosaurs and titanosaurs, may have evolved to large body sizes by about 72 million years ago, the researchers say. is suggesting.

They speculate that the evolution of giant tyrannosaurines may have been driven by the enormous body size of the herbivores they preyed on in southern Laramidia.

“The evolution of giant tyrannosaurs in southern North America suggests that large dinosaurs evolved at lower latitudes in North America, along with giant ceratopsians, hadrosaurs, and titanosaurs.” said.

of study It was published in the magazine scientific report.

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SG Dalman other. 2023. Giant tyrannosaurs that lived in southern North America from the Campanian to the Maastrichtian and the evolution of giant tyrannosaurids. science officer 13, 22124; doi: 10.1038/s41598-023-47011-0

Source: www.sci.news

Discovery of new Tyrannosaurus species through early fossil findings

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Artist's impression of Tyrannosaurus macraensis, a relative of Tyrannosaurus rex

sergei krasinski

A portion of a dinosaur skull discovered 40 years ago has been identified as a new species of dinosaur. tyrannosaurusand is probably the closest relative tyrannosaurus rex. The study adds a new twist to the long-standing debate about how many different tyrannosaurus species there were, and could help shed light on how the iconic predator evolved.

tyrannosaurus They first appeared in North America about 68 million years ago, 2 million years before the mass extinction event that wiped out most dinosaurs. Paleontologists are puzzled about the origins of this carnivore. Some suggest that it is an ancestor of tyrannosaurus Some people walked across land bridges from prehistoric Asia, while others traced their origins to southern North America.

Anthony Fiorillo Researchers from the New Mexico Museum of Natural History and Science reviewed fossils in the museum's collection that were discovered in a rock formation known as the McRae Formation in western New Mexico.

Skulls were originally classified as: tyrannosaurus, Fiorillo and his colleagues noticed differences in the bones.They proposed that this specimen represented an older species, which they named Tyrannosaurus macraiensis in reference to the rock in which it was found.

They estimated that the dinosaur was about 12 meters long, comparable in size to an aosaurus. Tyrannosaurus, However, it lived about 4 million years ago.

difference between tyrannosaurus and T. macraensis It would have been relatively subtle.on the other hand tyrannosaurus He had a prominent ridge on his eyebrow, and a bone-crushingly wide jaw with the same ridge. T. macraensis The body is less developed and the skull is thinner, Fiorillo said.

Jawbone identified as new species of Tyrannosaurus

nick longrich

Other recent studies have proposed that several species exist. tyrannosaurus And the so-called tyrannosaurus Fossils need to be reallocated. However, such proposals are controversial and are mostly rejected by dinosaur paleontologists. The new study is likely to spark further debate about that number. tyrannosaurus The species was found in North America.

“I hesitate to consider Tyrannosaurus macraiensis as different from tyrannosaurus rex” Jared Voris at the University of Calgary, Canada. He points out that many of the anatomical features that make the new species unique are also present in the specimen. tyrannosaurus.

Regardless of species assignment, the existence of such large tyrannosaurs millions of years ago is tyrannosaurus This suggests that southwestern North America was an important center of dinosaur evolution. “The age range of the proposed specimen is unique and requires further study,” Voris said. That's because it could outline a clearer picture of dinosaur evolution during the last few million years of the Cretaceous.

The New Mexico tyrannosaurus was discovered in the same rock as a giant horned dinosaur, an anthropomorphic duck-billed dinosaur, and a long-necked herbivore up to 30 meters long. Fiorillo and his colleagues tyrannosaurus It may have evolved to its gigantic size to prey on these large herbivores, and later spread north as the last “tyrant lizard” to stalk the planet.

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Source: www.newscientist.com

Paleontologists identify Nanotyrannus as a distinct and small tyrannosaurus species

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Tyrannosaurus is one of the most intensively studied and best known dinosaurs. Nevertheless, their relationship and system are highly controversial. The ongoing discussion is Nanotyrannus lansensisinterpreted as either a separate genus of small-bodied tyrannosaurs, or a juvenile tyrannosaurus. tyrannosaurus rex. In a new study, paleontologists from the University of Bath and the University of Chicago examined multiple lines of evidence that Nanotyrannus lansensis as a separate species.

Nanotyrannus attack a boy tyrannosaurus. Image credit: Raul Martin.

first skull Nanotyrannus It was discovered in Montana in 1942, but paleontologists have debated for decades whether it was a separate species or just a juvenile of a much larger species. tyrannosaurus.

In the new study, paleontologist Nick Longlich of the University of Bath and paleontologist Evan Saitta of the University of Chicago reanalyzed the fossil and looked at its growth rings and body structure. Nanotyrannusand hitherto unrecognized fossils of youth tyrannosaurus.

Measuring tree rings Nanotyrannus They found that the bone was more densely packed toward the outside, indicating that bone growth was slowing down. That suggests these animals were nearly life-sized. It is not a young body that grows quickly.

Fossil growth modeling shows that the animal could have weighed between 900 and 1,500 kg and reached a maximum length of 5 meters, about 15% of the size of a giant. . tyrannosaurus8,000 kg and grew to over 9 m.

“I was quite surprised when I saw these results. I didn't expect to see such conclusive results,” said Dr. Longlich.

“If they were young tyrannosaurus They're supposed to grow like crazy and gain hundreds of pounds a year, but we don't see it that way. ”

“We tried modeling the data in different ways, but still got low growth rates. This seems to put an end to the hypothesis that these animals are young.” tyrannosaurus”

Researchers found no fossil evidence that combined both traits to support the existence of different species Nanotyrannus and tyrannosaurus —If one turns into the other, it will exist.

Every fossil they examined could be confidently identified as one or the other species.

The growth patterns of other tyrannosaurs were also inconsistent with the hypothesis that these tyrannosaurs were young. tyrannosaurus.

“If you look at other juvenile tyrannosaurs, you'll see a lot of characteristics that are typical of adults. Very young. tarbosaurus — next of kin of tyrannosaurus — exhibiting unique characteristics of adults,” Dr. Longrich said.

“Just as kittens look like cats and puppies look like dogs, the various juvenile tyrannosaurs are also unique. And Nanotyrannus nothing similar tyrannosaurus”

“It may have grown in a completely different way than other tyrannosaurs or other dinosaurs, but it's more likely that it simply wasn't a dinosaur. tyrannosaurus”

But it poses a mystery. Nanotyrannus not a boy tyrannosaurusSo why didn't anyone find the young man? tyrannosaurus?

“That was always one of the big questions. Well, it turns out we actually found it,” Dr. Longrich said.

“However, this fossil was collected many years ago, put away in a box of unidentified bones in a museum drawer, and then forgotten.”

Nanotyrannus They were lighter in build and had longer limbs than their stouter relatives. It also had larger arms, unlike those known for their short arms. tyrannosaurus.

“Actually, my arms are longer than people's.” tyrannosaurus.Even the biggest one tyrannosaurushave shorter arms and smaller claws than these smaller animals. Nanotyrannus. This was an animal whose arms were actually pretty scary weapons. It's actually a completely different animal, smaller, faster and more agile,” Dr. Longrich said.

“tyrannosaurus While animals relied on size and strength, this animal relied on speed. ”

“The long arms and other features suggest it was only a distant relative.” tyrannosaurus — and may have been sitting outside the family TyrannosauridaeWhich tyrannosaurus Part of the predatory dinosaur family. ”

a paper The survey results were published in a magazine fossil research.

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Nicholas R. Longrich and Evan T. Saitta. 2024. Taxonomic status of Nanotyrannus lansensis (Dinosaur: Tyrannosauridae) – A different taxon of small tyrannosaurs. Phos.stud 2 (1): 1-65; doi: 10.3390/fossils2010001

Source: www.sci.news