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Dinosaurs were not the only animals that grew fast during the Mesozoic

A recent study led by Macalester College in Minnesota has found that not only did the earliest dinosaurs exhibit rapid growth rates, but so did many animals during the Mesozoic era, spanning from 252 to 66 million years ago. 

The scientists delved into the growth strategies of some of the earliest dinosaurs and their contemporaries, shedding light on a key aspect that might have contributed to the dinosaurs’ eventual dominance.

One of the oldest known Mesozoic ecosystems

By analyzing fossilized leg bones from the Ischigualasto Formation in Argentina, dated between 231-229 million years old, the team was able to examine the growth patterns of various species living in one of the oldest known Mesozoic ecosystems. 

This selection included not only some of the earliest known dinosaurs but also several non-dinosaur reptiles and an early mammalian relative.

Rapid growth rates among Mesozoic animals

The histological analysis revealed that elevated growth rates were common among ancient animals of the Mesozoic era, aligning more closely with the growth rates of modern mammals and birds than those of present-day reptiles. 

Interestingly, while early dinosaurs demonstrated particularly rapid growth, they were not alone; several non-dinosaur reptiles exhibited similar growth rates.

“Our results indicate that the Ischigualasto vertebrate fauna collectively exhibits relatively high growth rates. Dinosaurs are among the fastest growing taxa in the sample, but they occupied this niche alongside crocodylomorphs, archosauriformes, and large-bodied pseudosuchians,” noted the researchers.

Dinosaur success was not solely tied to rapid growth

This discovery suggests that rapid growth was a widespread trait among different lineages during the Triassic period (252-201 million years ago), indicating that while this characteristic may have been advantageous for dinosaurs, it was not unique to them. 

This challenges the notion that elevated growth rates were solely responsible for the dinosaurs’ success and suggests that other factors also played a role in their rise to prominence in Mesozoic ecosystems.

“Our sample comes from a time in which dinosaurs were the new kids on the block, restricted to relatively small, basic body plans, and evolving within a world rich with a diverse array of more specialized, non-dinosaur reptiles,” wrote the researchers.

“We tackled the question of how all of these animals grew, and found that the earliest dinosaurs grew quickly, and that these rapid growth rates probably played a significant role in dinosaurs’ subsequent ascent within Mesozoic ecosystems; but dinosaurs weren’t unique – many of their non-dino sidekicks shared rapid growth 230 million years ago.”

More about the Mesozoic era 

The Mesozoic Era, known as the “Age of Reptiles,” is divided into three periods: the Triassic, Jurassic, and Cretaceous.

This era witnessed the dominance and diversity of reptilian life forms, especially dinosaurs, but it also included a variety of other animals that shared the planet with these iconic creatures.

Triassic period 

During the Triassic period, the early Mesozoic era, the world saw the emergence of the first dinosaurs alongside a group of reptiles known as archosaurs, which also included the ancestors of crocodiles and birds.

The seas were home to the first marine reptiles like ichthyosaurs and nothosaurs, while the skies began to be patrolled by the first pterosaurs near its end.

Jurassic period 

The Jurassic period marked an increase in the diversity and complexity of dinosaur life. Giant sauropods like Brachiosaurus and Diplodocus roamed the land, feeding on the abundant vegetation.

This period also saw the rise of more sophisticated predators, including the well-known Allosaurus. The oceans teemed with marine reptiles such as plesiosaurs and the larger ichthyosaurs, while the air saw greater diversity in pterosaurs.

Cretaceous period 

The Cretaceous period brought even greater diversity and the dominance of dinosaurs. Tyrannosaurus rex, Triceratops, and Velociraptor are iconic representatives of this period. Flowering plants appeared, changing landscapes and providing new food sources.

The seas were dominated by large marine reptiles like mosasaurs and the enormous pliosaurs, and the skies witnessed the evolution of birds from certain groups of small theropod dinosaurs.

Dramatic ending

However, the Mesozoic era came to a dramatic end approximately 66 million years ago with a mass extinction event, likely caused by a combination of volcanic activity, climate change, and the impact of a massive comet or asteroid.

This event led to the demise of the majority of dinosaur species, along with many other forms of life, paving the way for mammals to become the dominant terrestrial animals in the subsequent Cenozoic era.

The study is published in the journal PLoS ONE.


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