Which dinosaur had the longest neck?

When most people imagine a dinosaur, they might initially think of a large, menacing tyrannosaurus rex, or the slow and lumbering stegosaurus with huge plates along its back, or the three-horned triceratops with its massive frill or crest above its neck. But one of the most frequently recognized types of dinosaurs is a sauropod.

As mentioned in my last post, all dinosaurs are generally divided into two categories: saurischia (“lizard hips”) and ornithischia (“bird hips”). Within saurischia, it’s further broken down into theropods (bipedal carnivores like t-rex) and sauropods.

Sauropods were plant-eating dinosaurs that walked on all four legs and had extremely long necks, with relatively small heads. They grew to colossal sizes and were the largest animals to have ever walked the earth. Technically blue whales are larger, but they live in the ocean and don’t have to deal with the constraints of gravity, so it’s apples and oranges in terms of a comparison. Some of the most well known sauropods are brontosaurus (now known as apatosaurus, though this is a heated debate among some paleontologists) and brachiosaurus.

dark rendering of long-necked dinosaurs — mamenchisaurs (artwork by cheungchungtat)

It’s true that a lot of sauropods had very long necks – it seems to be one of their defining features. But the long neck is intriguing, and it raises several questions. Why is the neck so long? Structurally speaking, how was this possible? And which dinosaur had the longest neck?

It’s always hard to say anything with total certainty about animals that went extinct more than 66 million years ago. I had never heard of the “Mamenchisaurus” until recently, but it seems to be a strong contender for dinosaur with the longest neck, and in any pictures (whether skeletal or depictions of what it probably looked like in real life) it’s startling. The Mamenchisaurus was approximately 60 feet in total length, and a good 30 feet of that was just the neck. Relative to its body size, this animal had the longest neck of any known dinosaur.

The Mamenchisaurus lived in what is now China (though of course the map looked very different back then) and seems to have lived during the Middle and Late Jurassic, and possibly in the Early Cretaceous.

long-necked dinosaur — how’s the weather up there?

At first, I thought that the purpose of the long neck would have been to reach really tall vegetation and trees, like modern giraffes. But it seems more likely that the dinosaur used its neck more horizontally to reach medium height or lower level vegetation, and the benefit in neck length was instead to sweep across much larger areas. This way, it didn’t need to move its body much (if at all) while feeding. No doubt this saved a lot of energy considering the colossal size and weight of the body!