Plant-eating Dinosaurs Could Have Evolved To Be Even Larger, Reaching 100 Tonnes

An image of a Jurassic dinosaur bone fossil.

Titanosaurs, the last surviving sauropod dinosaurs, achieved their colossal size by eating a lot and growing incredibly fast. Despite their already enormous size, they may have evolved to be even larger given more time, according to paleontologists. Their size allowed for more efficient oxygen supply throughout their body, making almost no limits to how large they could grow.

Discovering a new Titanosaur Species

Paleontologists Kristina Curry Rogers and Catherine Forster discovered a new species of titanosaur, named Rapetosaurus krausei, when they found a single rib bone that was almost 3 meters long, which is about the length of a ping-pong table, in 2001. This bone was the first evidence of a new type of titanosaur.

Titanosaurs, which got their name from the Greek words "titano" meaning gigantic and "sauros" meaning lizard, were the final surviving group of sauropod dinosaurs. These herbivorous creatures were characterized by their long necks, long tails, and small heads.

They were discovered after other famous sauropods, such as Brachiosaurus, Diplodocus, and Apatosaurus, which existed during the Jurassic period around 201 to 145 million years ago.

BBC reports that titanosaurs are "titanic" and challenging to excavate, as a single skeleton can take an entire field season or more to extract from the rocks.

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How Titanosaurs Evolved To Be One of the Largest Animals To Ever Walk the Earth

According to Rogers, a paleontologist and professor of biology and geology at Macalester College in Minnesota, USA, scientists think that titanosaurs grew rapidly and didn't stop until they reached their enormous adult sizes.

She compares their growth rates to those of whales, which are considered very fast in the animal kingdom. However, unlike whales which consume high-protein milk from their mothers, titanosaurs had to forage for their own food.

All titanosaurs hatched from eggs between the size of a softball and a soccer ball and grew quickly by constantly eating to achieve their colossal size without much parental care, which is different from their meat-eating relatives that paused their growth more often as they got older.

Although titanosaurs were the largest sauropods, their ancestors among sauropods were already big. They are believed to have evolved to 70-80 tonnes from a 20-30 tonne ancestor, but it probably didn't require that much evolutionary innovation, as all the structures and systems were already set up for success at huge sizes.

According to Matthew T Carrano, a paleobiologist at the Smithsonian Institution in Washington, D.C., it was possible that titanosaurs could have reached 100 tonnes, raising the question of whether their colossal size was limited only by the asteroid impact that hit the Earth 66 million years ago.

Titanosaurs were able to evolve to such sizes due to the long necks, pillar-like limbs, and "pneumatic" air sacs that made their skeletons lighter, in addition to short feet and joint structures with enormous volumes of squishy cartilage at the ends of their bones, which was an adaptation for better sustaining the animal's massive body weight.

These characteristics also allowed them to grow to almost any size without limits. However, there is no clear answer on how the titanosaurs managed to outgrow their sauropod ancestors.