Titanosaurs were the largest land animals ever seen on Earth – these plant-fed dinosaurs combined features of both reptiles and mammals

You’re probably familiar with the classic sauropod dinosaurs—the quadrupedal herbivores famous for their long necks and tails. Animals like Brachiosaurus, Apatosaurus It is Diplodocus have been standard fixtures in science museums since the 1800s.

With their small brains and huge bodies, these creatures have long been the poster children of animals destined for extinction. But recent discoveries have completely rewritten the doomed sauropod narrative.

I study a lesser-known group of sauropod dinosaurs – the Titanosauria, or “titanic reptiles”. Instead of being extinct, titanosaurs flourished long after their more famous cousins ​​had disappeared. They were not only big and responsible all seven continentsthey stood amidst the recently evolved dinosaurs with duck bills and hornsup to one asteroid hit Earth and ended the age of dinosaurs.

The secret to titanosaurs’ remarkable biological success may be how they fused the best of reptile and mammalian traits to form a unique way of life.

Moving with the continents

Titanosaurs originated in the Early Cretaceous periodalmost 126 million years ago, at a time when many of the Earth’s landmasses were much closer than they are today.

During the next 75 million to 80 million years, the continents slowly separatedand titanosaurs wandered along with the changing formations, distributing themselves throughout the world.

There was almost 100 species of titanosaurs, constituting more than 30% of known sauropod dinosaurs. They varied greatly in size. Of the largest known sauropods ever discovered, including Argentinosaurus, Patagotitan It is Futalognkosauruswhose weight exceeded 60 tons (54.4 metric tons) and were larger than a semi-truck, even the smallest known sauropods, including Rinconsaurus, Saltasaurus It is Magyrosauruswhich weighed just 6 tons (5.4 metric tons) and were approximately the size of an African elephant.

Babies for Titans

Like many reptiles, titanosaurs started life relatively small, hatching from eggs no bigger than grapefruits.

O best data on titanosaur nests and the eggs come from a site in Argentina called Auca Mahuevo, with exposed rocks 75 million years old. The site contains hundreds of fossilized nests containing thousands of eggs, some of which are so well preserved that scientists have recovered skin impressions from ancient embryos.

The large number of nests found together, in multiple geological layers, suggests titanosaurs I came back to this site several times to lay their eggs. The nests are so widely spaced that it is unlikely that an adult titanosaur would have been able to move freely around the nesting site. Titanosaurs likely had an aloof parenting style, similar to many reptiles that lay multiple eggs and don’t spend much time tending the nest or caring for young.

A baby titanosaur it would be about 30 centimeters high, 1 meter long and 2.5 to 5 kg. Recent evidence from a site in Madagascar suggests that these little titans were born ready to fight.

Fossilized bones of the species Rapetosaurus suggest that by the time they would be knee-high to a modern human being, they were probably fending for themselves. Microscopic details recorded deep within the bones indicate that the baby Rapetosaurus They probably foraged for plants independently and moved much more nimbly than their lumbering adult relatives.

During the first century of dinosaur science, paleontologists imagined titanosaurs as giant, overgrown reptiles—and used reptilian growth rates to predict their milestones. In this slow-growth model, even the smallest titanosaurs would have taken nearly a century to reach their full size, meaning they would have been relatively small for much of their lives. New evidence suggests this growth pattern is unlikely.

Scientists like me study titanosaur bones at high magnification to better understand your growth. We looked at the microscopic patterns of bone minerals, as well as the density and architecture of the spaces that contained blood vessels and cells.

The denser the blood supply to a bone, the faster the animal will grow. These signatures are also present in living animals and can accurately reflect growth rates, anomalies and even age.

Bone data shows that titanosaur growth rates were alongside mammals such as whales – much, much faster than any living reptile – meaning they would have reached their enormous adult size in just a few decades. Scientists can’t know for sure how long titanosaurs lived, but based on large land animals living today, titanosaurs lived possibly 60 years or more.

Powered by plants

The rapid growth rates of sauropods were due in part to body temperature. By studying the chemistry of fossilized teeth and eggshellsscientists determined that titanosaurs had body temperatures ranging from about 95 to 100.5 degrees Fahrenheit (35 to 38 degrees Celsius). This is higher than that of crocodiles and crocodiles, about the same as that of modern mammals, and slightly lower than that of most birds, whose bodies can regularly become as hot as 104 F (40 C).

The rapid growth rates of titanosaurs were also driven by their prodigious appetite for plants. Microscopic patterns of scratches, wear and teeth marks indicate that titanosaurs in Argentina were fed a diverse, sand-rich diet, suggesting they were dining on plants found deeper below the groundwhere sediments would most commonly be found.

In India, pieces of fossilized feces, also known as coprolitesshow that titanosaurs ingested everything from plants from ground level to leaves and branches of trees.

Like all dinosaurs, titanosaurs replaced their teeth throughout their lives. But the data shows they replaced every tooth approximately every 20 days for maximum efficiency, one of the highest tooth replacement rates known in dinosaurs.

If it weren’t for asteroid impact 66 million years agoThese long-lived, incredibly diverse, and extremely successful animals would likely have continued to thrive, in places as far away as Madagascar, Romania, North America and even Antarctica. Instead, titanosaurs were among the witnesses – and victims – of Earth’s most recent mass extinction.

This article was republished from The conversation, an independent, nonprofit news organization that brings you trusted facts and analysis to help you understand our complex world. It was written by: Kristi Curry Rogers, Macalester College

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Kristi Curry Rogers receives funding from the National Science Foundation and the David B. Jones Foundation.