You’ve likely heard of the iconic sauropod dinosaurs, those massive four-legged herbivores known for their elongated necks and tails. Creatures like Brachiosaurus, Apatosaurus, and Diplodocus have been museum staples since the 19th century.
These dinosaurs, with their tiny brains and colossal bodies, were once considered the epitome of creatures doomed to extinction. However, recent findings have dramatically altered that perception.
I focus my research on a less familiar group of sauropod dinosaurs called the Titanosauria, or “titanic reptiles.” Contrary to becoming extinct, titanosaurs thrived well after their more renowned relatives disappeared. They dominated across all seven continents, coexisting with the newly emerged duck-billed and horned dinosaurs, until an asteroid collision marked the end of the dinosaur era.
The remarkable success of titanosaurs might be attributed to their unique blend of reptilian and mammalian traits, which fostered a distinctive lifestyle.
Titanosaurs first appeared around the Early Cretaceous Period, nearly 126 million years ago, during a time when the Earth’s continents were much closer than they are today.
Around 200 million years ago, the supercontinent Pangea began to split and drift apart.
Over the next 75 to 80 million years, as the continents gradually separated, titanosaurs dispersed globally, adapting to the shifting landscapes.
There were nearly 100 species of titanosaurs, accounting for more than 30 percent of all known sauropod dinosaurs. Their sizes varied significantly, from the largest sauropods ever discovered, such as Argentinosaurus, Patagotitan, and Futalognkosaurus, which weighed over 60 tons and were larger than a semi-truck, to the smallest sauropods like Rinconsaurus, Saltasaurus, and Magyarosaurus, which weighed around 6 tons and were about the size of an African elephant.
Titanosaurs started their lives quite small, hatching from eggs no larger than grapefruits.
The most comprehensive information on titanosaur nests and eggs comes from a site in Argentina named Auca Mahuevo. This site, with its 75 million-year-old exposed rocks, contains hundreds of fossilized nests with thousands of eggs, some preserving skin impressions from ancient embryos.
The abundance of nests found together suggests titanosaurs returned to this site repeatedly to lay their eggs. The nests were so closely packed that it’s improbable an adult titanosaur could navigate through the nesting ground. This indicates titanosaurs likely practiced a hands-off approach to parenting, similar to many reptiles today that lay numerous eggs and provide minimal care post-hatching.
A titanosaur hatchling would have been about 1 foot tall, 3 feet long, and weighed between 5-10 pounds. Evidence from Madagascar shows these young dinosaurs were highly independent, foraging for plants and moving agilely from an early age.
Initially, scientists believed titanosaurs grew slowly, like other reptiles. However, new research has challenged this view.
By examining titanosaur bones under high magnification, we can observe the patterns of bone minerals and the structure of spaces that once housed blood vessels and cells.
A dense network of blood vessels in the bones indicates rapid growth, similar to that seen in mammals like whales, suggesting titanosaurs reached their massive sizes much quicker than previously thought.
The rapid growth of titanosaurs was likely fueled by their high body temperatures and voracious plant-based diets. Studies of their fossilized teeth and eggshells have shown that titanosaurs had body temperatures comparable to modern mammals.
Their diets were diverse, as evidenced by microscopic wear patterns on their teeth and fossilized feces, indicating they consumed everything from ground-level plants to tree leaves and branches.
Titanosaurs continually replaced their teeth, about every 20 days, to efficiently process their plant-based diet.
If not for the asteroid impact 66 million years ago, these successful and diverse creatures might have continued to thrive across the globe, from Madagascar to Antarctica. Unfortunately, titanosaurs were among the many species that perished in the last mass extinction event on Earth.
Kristi Curry Rogers, a Professor of Biology and Geology at Macalester College, shares this insight. This article, originally published on The Conversation, is republished here under a Creative Commons license.