Episode 101 – Sauropods

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Dinosaurs are famous for being successful, strange, and super-sized, but one group outdoes all the rest. This episode, we’re discussing the fascinating and puzzling group of animals that smash the record for largest land animals of all time: Sauropods.

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Giants Among Giants

Sauropods are famous, strange, successful, and enormous. They have a body plan unlike any other animals, with bulky torsos supported by columnar legs and small heads at the end of very long necks. This unusual shape not only makes them instantly recognizable but was also apparently a winning evolutionary strategy; sauropods thrived in a variety of habitats all around the world for over 100 million years.

Sauropods have been known since the 1800s, and new species are being named to this day. Left: Diplodocus (this specimen is Dippy!) a famous genus of sauropod named in 1878. Image by Drow male / CC BY-SA 4.0; Right: Artist’s reconstruction of Yamanasaurus from Ecuador, named within this past year. Image by Prehistopia / CC BY-SA 4.0.

And of course, they were huge. The very largest species of land mammals and non-sauropod dinosaurs could weigh 10, 15, even 20 tons – impressive, to be sure! But 20 tons is practically average for sauropods, and the very largest of them were over 30 meters (100 feet) long, with estimated weights of at least 50 tons. Sauropods are the largest land animals of all time, and nothing else even comes close.

Sauropod Evolution

Sauropods belong to a broader group called sauropodomorphs, which got their start in the Late Triassic. These early forms looked a lot like most early dinosaurs: 1-2 meters (3-6 feet) long, bipedal, and with grasping hands. These include Eoraptor, Panphagia, Thecodonotosaurus, and more. Already, these early sauropod-cousins had small heads and long necks compared to other early dinos.

Eoraptor, an early sauropodomorph from Argentina, was originally thought to be a relative of theropods, hence the name. Image by The Lord of the Allosaurs / CC BY-SA 3.0

From those humble beginnings came a group called prosauropods, including such famous forms as Plateosaurus and Massospondylus. These were dominant herbivores all over the world, and could reach sizes of 5-10 meters (15-30 feet) and a few tons in weight at a time when most other dinosaurs were still relatively small and scarce. Like their ancestors, prosauropods were bipedal, but like their descendants, they had long necks and sturdy bodies.

Plateosaurus, a successful prosauropod and one of the earliest dinosaurs to be given a name back in the early 1800s. Image by FunkMonk / CC BY-SA 3.0

The earliest true sauropods show up around the Late Triassic or Early Jurassic, and by the Middle Jurassic, they have the features we might recognize: tiny heads with simple teeth and wide-gaping jaws; extremely long necks; and four pillar-like legs to support bodies that could weigh 10-20 tons or more. Among the totality of sauropod diversity were species with neck sails, skin armor, tail clubs, weird comb-faces, and much more. There were even dwarf sauropods that were only the size of a cow!

Over the course of their evolution, several groups of sauropods would reach super-giant sizes, with bodies well over 30 meters (100 feet) long and weighing at least 50 tons, maybe significantly more. Incredibly, these unparalleled sizes evolved independently in diplodocids (like Diplodocus), titanosaurs (Argentinosaurus), brachiosaurs (Brachiosaurus), and more.

Argentinosaurus is one of the largest sauropods – and thus largest land animals – of all time, with size estimates of well over 30 meters (100 feet) and 50 tons.
Image by Sellers et al 2013 / CC BY 2.5

Living Large

You might wonder – as scientists have for centuries – how sauropods managed to grow so big. It’s probably safe to say that there was no single feature that did the trick, but instead the combined effect of many features. Like many dinosaurs, sauropods had sturdy bones to support their weight; air sacs that contributed to an efficient, bird-like breathing system; a parasagittal stance with the legs held directly under the body for support; and many features to help their huge bodies keep cool, such as expanded nasal passages.

But they were also champion eaters. Sauropods’ bodies are built for maximum lunch with minimal effort: bulk browsing. Their long necks allowed them to reach lots of food while standing in one spot, while their small heads and simple teeth were good for snipping vegetation but not chewing, instead vacuuming up their food to be digested by stomach stones.

Sauropods and their ancestors were dominant herbivores all over the planet from the Late Triassic to the Late Cretaceous, but even their size and success couldn’t save them from demise at the K-Pg boundary.

So much more

Tons of great sauropod info at Dr. Tom Holtz’s course, Dinosaurs: a Natural History.

Sauropods and the Evolution of Gigantism: Technical paper and popular article.

Early history of sauropod discoveries (non-technical)

Lots of debate and discussion has surrounded sauropod neck posture, with various studies looking to biomechanics or living comparisons.

This episode’s Patron question regarded the impact of sauropods on the landscape. In our answer, we referenced information from page 20 of this paper, and also from this paper.

If you enjoyed this topic and want more like it, check out these related episodes:

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