You’re probably familiar with classic sauropod dinosaurs, four-legged herbivores famous for their long necks and tails. like animals brachiosaurus, apatosaurus And Diplodocus They 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 for animals doomed to extinction. But recent discoveries have completely rewritten the doomed sauropod narrative.
I study Titanosauria, or “titanic reptiles,” a lesser-known group of sauropod dinosaurs. Rather than becoming extinct, titanosaurs continued to thrive long after their more famous cousins had gone extinct. Not only were they large and responsible on all seven continents, they held their own among the newly evolving duck-billed and horned dinosaurs until an asteroid hit Earth, ending the age of dinosaurs.
The secret to the remarkable biological success of titanosaurs may be how they combined the best of both reptilian and mammalian characteristics to create a unique lifestyle.
moving with continents
Titanosaurs appeared about 126 million years ago, during the Early Cretaceous Period, when most of Earth’s landmasses were much closer together than they are today.
Over the next 75 to 80 million years, the continents gradually separated and the titanosaurs dispersed around the world, drifting in changing formations.
There were approximately 100 species of titanosaurs, accounting for more than 30% of known sauropod dinosaurs. Their sizes were very different. The largest known sauropods discovered so far are: argentinasaurus, patagotitan And FutalognkosaurusDown to the smallest known sauropods, which weighed more than 60 tons (54.4 metric tons) and were larger than a semi-truck Rinconsaurus, saltasaurus And MagyarosaurusThey weighed only around 6 tons (5.4 metric tons), about the size of an African elephant.
From babies to titans
Like many reptiles, titanosaurs started life relatively small, hatching from eggs no larger than grapefruits.
The best data on titanosaur nests and eggs comes from a site in Argentina called Auca Mahuevo, where exposed rocks are 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 obtained skin impressions from ancient embryos.
Multiple nests coexist in multiple geological layers, indicating that titanosaurs returned to this area repeatedly to lay their eggs. The nests are so closely spaced that it is unlikely that an adult titanosaur could move freely around the nesting area. Titanosaurs likely had a hands-off parenting style, similar to many reptiles that laid large numbers of eggs and did not spend much time tending the nest or caring for the young.
A hatched titanosaur hatchling would have been roughly 30 centimeters tall, 1 meter long and weighed 2.5–5 kg (5–10 pounds). Recent evidence from a site in Madagascar shows that these tiny giants are born ready to rumble.
Fossilized bones of the species rapetosaurus They suggest that by the time they were knee-high to a modern human, they were probably fending for themselves. Microscopic details recorded deep in bones reveal baby’s presence rapetosaurus They probably foraged plants independently and moved much more nimbly than their lumbering adult relatives.
In the first century of dinosaur science, paleontologists imagined titanosaurs as giant, overgrown reptiles and used reptilian growth rates to estimate their milestones. In this slow growth pattern, even the smallest titanosaurs would have taken nearly a century to reach their full size; This means that they will remain relatively small for a significant part of their lives. New evidence suggests this growth model is unlikely.
Scientists like me study the bones of titanosaurs at high magnification to better understand their growth. We look at the microscopic patterns of bone minerals, as well as the density and architecture of the spaces that hold blood vessels and cells.
The more intense blood flow to the bone, the faster the animal grows. These signatures are also present in living animals and can accurately reflect growth rates, anomalies, and even age.
Bone data show that titanosaurs’ growth rates were on par with mammals like whales (much, much faster than any living reptile), meaning they would have reached massive adult sizes in just a few decades. Scientists don’t know for sure how long titanosaurs lived, but compared to large land animals living today, we can say that titanosaurs probably lived 60 years or more.
It feeds on plants
Sauropods’ rapid growth rates were partly due to their body temperature. Scientists studying the chemistry of fossilized teeth and eggshells determined that titanosaurs’ body temperatures ranged from approximately 95 to 100.5 degrees Fahrenheit (35 to 38 degrees Celsius). This is higher than that of crocodiles and crocodiles, about the same as modern mammals, and slightly lower than most birds, whose bodies can regularly heat up to 40C.
Titanosaurs’ rapid growth rates were also due to their extraordinary appetite for plants. Microscopic scratches, abrasions, and pits on their teeth suggest that titanosaurs from Argentina ate a diverse diet rich in sand; This suggests that they fed on plants lower underground, where sediments were more widely available.
In India, fossilized pieces of feces, also known as coprolites, show titanosaurs devoured everything from ground-level plants to leaves and branches of trees.
Like all dinosaurs, titanosaurs changed their teeth throughout their lives. But the data shows that they replaced each tooth approximately every 20 days for maximum efficiency, one of the highest tooth replacement rates known for dinosaurs.
Had it not been for the asteroid impact 66 million years ago, these long-lived, incredibly diverse, and highly 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 last mass extinction.
This article is republished from The Conversation, an independent, nonprofit news organization providing facts and authoritative analysis to help you understand our complex world. 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.