It’s all about the bones

squirrel monkey invert1

Skeletons are fascinating. How did they evolve? Why do we have them? What is their purpose? Over the last 5 months, I have been dedicating a portion of my time studying the skeletal anatomy of a variety of animals at my university. If I could only impart one piece of advice to fellow artists, it would be that they should allocate time into studying a specimen collection of any kind. Study the bones, and draw them often.

 

Here I want to make note of some facts about the skeleton. One function of the skeleton is to provide support for your body, a kind of framework. Another function is to protect vital organs while allowing movement. For example, the rib cage is able to expand to accommodate the expansion of the lungs upon inhalation. The skull protects the brain, and teeth (when they are present) are specialized for particular diets. I can provide many more examples as to how important bones are, and why we should learn as much as we can about them. For the artist, it is absolutely critical that the skeleton should be studied in detail. For life drawing sessions, it is crucial to know the bones, their shapes, and where muscles originate and insert. Knowing the skeleton takes away a lot of mystery and guesswork in a drawing. Below I have included a drawing I am working on of a skeleton of a human infant. The skeleton I am drawing is real, and has been in the university for many years. I feel that the skeleton helps give me a realistic understanding of proportions. Human beings have the largest braincase in proportion to the body amongst any primate, and this is highly evident when looking at the skeleton. I will have to wait until the Fall semester to continue working on this drawing, as the skeleton is in the Anthropology lab. I have a long list of unfinished drawings, but that is ok. It gives me something to look forwards to working on.

human fetal skeleton1

Now about drawing the skeleton. To start out with, draw the individual bones. Generally, animal bones are stored in labeled boxes and are usually completely disarticulated, that is, the bones are present in their individual form. This is a perfect way to study the skeleton, as you can look at an individual humerus, or foot bone, and learn which side of the body it belongs to. The term ‘siding’ bones is where you differentiate which bones belong to which side of the body. You can even do some comparative anatomy work, which is very intriguing, and thought-provoking. Below are sketches of a Stump-tailed macaque’s left femur and innominate viewed from behind. I use a colour atlas of human anatomy to learn about the structures of the bones. The innominate bone is quite different from ours, but it is still part of the pelvis. The femur, however, is surprisingly similar to ours. It is not specialized for bipediality, but it is still readily identifiable as a femur.

Macaque leg1

Before drawing any bones, I take out all of the bones contained in the box and organize them on my work space. Many bones, when laid out side by side, will look like mirror images of one another. Depending on their features, I can identify which bones belonw on the left or the right side of the body. Sometimes I’ll find small, oddly shaped bones that I do not know the name of. These are called sesamoid bones, and they are primarily situated within tendons wherever joints occur. They are typically small, but one type is quite large and very well known: the patella, or kneecap. All sesamoid bones are very important as they reduce friction and help absorb shock. Every bit of the skeleton is important.

Learning to draw the ribcage was one of my primary goals. Before working on drawings of a complete ribcage, I needed to look at the individual vertebrae and ribs, and see their individual structures. I group individual vertebrae into four piles: cervical, thoracic, lumbar, and caudal. That last grouping is reserved primarily for animals with prominent tails, as our tail bones are reduced to the point that they are no longer external (except in some rare cases!) Below I have three drawings of different thoraxes, the top belonging to a European Polecat, the middle, a Stump-tailed macaque and the bottom, a Squirrel monkey. Although many of the skeletal specimens I find in the collection are completely disarticulated, I sometimes have the fortune of finding nearly complete skeletons that are still held together by dried tissues. These specimens are particularly valuable for learning how the ribs and vertebrae are put together. To make sure I don’t lose track on which vertebra I am on, I count the spines on the vertebrae and write their corresponding number. I also make sure to notice what small defining features differentiate each spine. For example, one spine might have a more rounded top, and the one following it might be very short. It is important to note that drawing is not a race. Take your time, as much time as you need, and allow yourself to take in small details and contemplate them.

polecat thorax1

stump tailed macaque thorax

squirrel monkey thorax1

When looking at bones in all their diversity, you will start to notice how some features bear similarities to one another. For example, I noticed a similarity to one of the limb bones, the ulna, and the calcaneus, a foot bone. The ulna looks almost like a calcaneus that has been stretched out, and both bones feature a small notch where a major tendon is attached. This similarity makes sense, both bones are involved in a lever function. Remember the rule: form follows function. This can really be seen when looking at, and studying each individual bone. Sometimes, I wonder if convergent evolution is not only acting on completely unrelated species, but also on completely different bones. At least, I tend to think the idea of convergence applies.

ulna calcaneus1

The skull is, of course, a highly modified feature of the skeleton that often bears the most distinctive variation. For example, many animals can be identified by looking at their teeth, and sometimes the shape of the teeth may be the only way to visually differentiate species. Teeth can give us plenty of information on an animal’s diet and behaviour, and they are one of the more durable structures in the fossil record. Looking at our teeth, they are fairly generalized, meaning that we can eat a wide variety of foods. Compare this with a different animal, such as the Cheetah, and you’ll see that their teeth are specialized for a carnivorous diet. Note the slicing molars and long canines.

Cheetah1

When looking at a skull, and making comparisons between species, I begin to think about similarities in diet. Take a look at the skull of a Black bear cub when compared to the Musk deer. When I look at the Black bear’s skull, I note how slender the jaws appear, especially in comparison to the larger Grizzly and Kodiak bears. The jaws of the Black bear taper off, and are strongly reminiscent of that of a grazing mammal. Although these bears are all omnivorous, the Black bear has a greater tendency towards grazing on a wide variety of plant matter. Check out the notable gap behind the canine teeth of the Black bear. This gap is known as the diastema, and is very prominent in herbivorous mammals. Apparently, its function is to aid in the manipulation of plant material. Is the Black bear on an evolutionary path to herbivory? Or will its descendants remain omnivorous? I could be right or wrong, but for the time being I am allowing myself to think about what I am looking at. I enjoy allowing myself to think about the specimen in front of me.

black bear skull1

muskdeer skull1

Drawing individual bones can be tedious work, but it’s critical to remain dedicated to learning each part. I will typically spend up to 5 or 6 hours a day in the collection room. At some time between 11:45 and 12:30, I make sure to have lunch. I may sometimes have lunch a little later. I’ll make sure that I walk around campus to check out some of the interesting plants and animals that I might find. The campus is notable for its great redwoods and many ginkgoes, the latter which produce particularly pungent seeds whose odor can be appreciated around Fall time. Only the female trees produce these seeds, and there are quite a lot of female ginkgoes around the Biology buildings on campus. The ginkgoes are quite the spectacle in the Fall, as their green leaves change to a stunning golden yellow. It doesn’t take long for the yellow colour to eventually fade, and unfortunately the colour does not preserve well. The Tulip trees are also blessed with this fine yellow hue; one does not need to travel too far to appreciate Fall’s colours. And look at the Yellow-rumped warbler; it seems golden yellow is a lovely colour for this time of year.

tulip tree1

Tulip trees acquiring their yellow colour in Fall.

Yellow rumped warbler 4

A Yellow rumped warbler is a common bird in the Fall and Winter months here.

 

Now that I’ve taken time to walk around and appreciate what I have seen, I am ready to return to my work. When I take a walk around campus, my mind is not focused completely on producing drawings. When I take a break, I give myself a chance to recharge and get back to work. Studying bones and all their intricate details is tedious and difficult at times. Taking breaks from my work is why I can continue being dedicated to my work. When I look at the colours on those trees, I am thinking only of the trees, and not about how I need to get back to my work, or how much work I have ahead of me. Even though I am looking at a lot of skeletal remains, I feel that the skeleton carries the essence of the animal that it once was. The skeleton was once alive, but is now a legacy of that animal and its ancestors. Although I have more to learn, I am aware that progress will come with time, because I am already dedicating myself to my studies. I feel that no time is wasted, even if I have only looked at the bones instead of drawing them. Looking, feeling and knowing is just as important as drawing, and that is something I feel every artist deserves to know.

tree shrew1

Tupaia will also have to wait until the Fall semester for completion

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