Giraffes Have Short Necks Compared to Sauropods. Learn Why and How.

Giraffes at the Saint Louis Zoo

Giraffes at the Saint Louis Zoo

Whenever we go to the zoo, we head straight for the giraffes. We never get tired of their lanky grace and the way they bow their big heads down and blink at us through their long lashes. Can you imagine a dinosaur with a neck six times longer than a giraffe’s? How and why can that be?

A study by Michael Taylor and Mathew Wedel outlines the reasons that sauropods were able to have such incredibly long necks:

Small, light heads

Sauropod heads were small and light because they did not need to have big jaws to chew their food. “Sauropod heads were simple cropping devices with a brain and sense organs, and did not require special equipment for obtaining food,” such as beaks.

The giraffe and Paraceratherium are the longest necked mammals; the ostrich is the longest necked extant bird; Therizinosaurus and Gigantoraptor are the largest representatives of two long-necked theropod clades; Arambourgiania is the longest necked pterosaur; and Tanystropheus has a uniquely long neck relative to torso length. Human head modified from Gray’s Anatomy (1918 edition, fig. 602). Giraffe modified from photograph by Kevin Ryder (CC BY, http://flic.kr/p/cRvCcQ). Ostrich modified from photograph by “kei51” (CC BY, http://flic.kr/p/cowoYW). Paraceratherium modified from Osborn (1923, figure 1). Therizinosaurus modified from Nothronychus reconstruction by Scott Hartman. Gigantoraptor modified from Heyuannia reconstruction by Scott Hartman. Arambourgiania modified from Zhejiangopterus reconstruction by Witton & Naish (2008, figure 1). Tanystropheus modified from reconstruction by David Peters. Alternating blue and pink bars are 1 m tall.

The giraffe and Paraceratherium are the longest necked mammals; the ostrich is the longest necked extant bird; Therizinosaurus and Gigantoraptor are the largest representatives of two long-necked theropod clades; Arambourgiania is the longest necked pterosaur; and Tanystropheus has a uniquely long neck relative to torso length.  Alternating blue and pink bars are 1 m tall.

Wide bodies and strong legs

Sauropod torsos were large and wide enough to support a neck that not only could reach the ground but extend even father away from their bodies, allowing them to reach very high and very far.

Lighter bones and leaner muscles to carry them

Sauropod vertebrae were very pneumatic –  hollow but strong – consisting of 60% air. As Taylor and Wedel explain, “in effect, sauropods inflated their vertebrae within the muscular envelope of the neck, moving the bone, muscle and ligament away from the centre so that they acted with greater mechanical advantage.”

Sauropods to scale

Sauropods to scale

More and longer vertebrae

All mammals, including giraffes, have seven vertebrae, but sauropods are more closely related to birds and crocodiles and those lighter bones are more numerous and longer than those of mammals.

Air-sac breathing system

A super long neck means a super long trachea – or windpipe – to bring air to the lungs. Mammals need a short trachea to get the amount of oxygen they require, but rather than having the air flow through just the trachea, sauropods had an air sac system that allowed them to take advantage of all of the air space (helped by those lighter bones) in the whole neck rather than just the windpipe.

We are still learning new things about dinosaurs every day – how they compare to mammals, birds and reptiles and what they say about the life of and history of our planet. The adventures of paleontology and the science of fossils are made real for kids in Tumblehome Learning’s Galactic Academy of Science Adventure #2, The Furious Case of the Fraudulent Fossil, in which two friends, Benson and Anita, travel through time to outwit a fossil thief. It’s good reading!

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Taylor et al. (2013) Why sauropods had long necks; and why giraffes have short necks. PeerJ 1:e36
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Comments (One Response)

  1. Mike Taylor says:

    Thanks for this very nice and readable summary of our work!