Monthly Archives: September 2017

A deeper look at the cheetah

The process of reconstructing extinct animals is like a dissection in reverse, where one adds soft tissue layer by layer on top of the animal’s skeleton. But in order to be prepared to work in such a way, it is necessary to get familiar with the inverse process, that is, proper dissection of extant animals. I have taken part in many dissections of big cats in collaboration with the University of Valladolid and the Paleobiology department of the Museo Nacional de Ciencias Naturales. Those dissections have allowed me to acquire first-hand knowledge of the feline anatomy, and to understand in more depth the differences between the various species of big cats.
One good example is the cheetah. We know this animal as “the feline greyhound”, and its lean appearance is obviously related to the considerable length of its limb bones relative to its body size, but is that all?

This drawing of the cheetah skeleton shows the gracile proportions and elongated limbs of the fleetest living cat

Well, the fact is that the cheetah’s muscles are arranged in a different manner than in other big cats. In the limbs, the bulk of the muscle mass is concentrated in the proximal segments (that is, those closest to the animal´s trunk), while the distal parts (those farthest from the trunk) hardly retain any muscle mass at all, and it is mostly tendons, not muscle fibers, that reach those segments.

The musculature of the cheetah is that of a true runner, with limb muscle masses concentrating near the animal´s trunk and little more than tendons reaching the paws

The external appearance of the cheetah betrays its lean proportions, but many details are obscured by the arrangement of the fat tissue (little as there is…), skin, and fur

Such a particular arrangement of the muscles is reflected in the shape and position of the muscle insertion areas in the animal´s bones, something that we can track as dissection proceeds deeper inside. Sketches and photographs record all the findings made during the process, and it is this kind of observations which in turn allow us to restore the lost musculature of extinct animals using bone morphology as a guide.

This series of sketches shows the process of dissecting the cheetah´s forelimb, starting with the intact limb (top) and ending with the bare bones (bottom). Of course this is just a selection from several sketches showing different stages of the dissection

Unfortunately dissection is a destructive process and once the tissues are removed from the specimen there is no putting them back in place. But fortunately we have the option of scanning the intact specimen before dissecting it, as we did with this cheetah. CT scan imagery allows us to check time and again the relationships between soft tissue and skeleton, looking at those structures from any angle and using perspectives we couldn’t check during dissection.

Here we see a screen capture of our CT scan of the cheetah forelimb, showing the relationship between the animal’s bones and the´soft tissue outline

Observations like these pave the way for my work in the anatomical reconstruction of extinct carnivores, but it also gives me a renewed, deeper look at modern big cats. Whenever I see a wild cheetah moving around in its environment I perceive the lever system of its bones, muscles and tendons working right under the skin, and my admiration for these wonderful creatures grows even more.

You can learn much more about these processes of dissection and reconstruction in my film “Bringing the Sabertooths Back to Life”, available for download at Wild World Visuals online store:
http://www.wildworldvisuals.com/product/bringing-the-sabertooths-back-to-life/

Advertisements