Drawing Animals in Detail
There are two major components to creating a detailed animal drawing: structure and surface. The fur of longhaired cats and dogs can obscure their musculature, but it is still necessary to understand the form underneath the fuzz if you are going to create a convincing drawing, rather than a formless fur ball. Observing similar shorthaired breeds is a useful source of information. Modeling the form of shorthairs is comparatively straightforward, as the shadow wraps around the form quite cleanly, but with long hair, clumps of hair often stick out in contrary directions and break up the form. If the fur is correctly modeled, with accurate highlights and direction of growth indicated, this problem can be minimized.
Studying anatomy is certainly worthwhile, but much of the skeleton is disguised under layers of muscle and fur, so in the first instance your time will be best spent observing visible structure and form. Careful observation is your key to correctly drawing the specific breed and individual animal; examples can be a guide, but then you have to trust your own eyes. With some animals, the variation between breeds is relatively subtle—a horse's head is always the same fundamental shape. Some animals, particularly dogs and cats, exhibit extreme differences in face shape and body type.
Sketch the basic structure, noting joints and key bones.
If you are interested in drawing animals, you'll want to obtain a reference source and spend some time studying their anatomy. You don't need to learn the names of bones or muscles unless it helps you remember how to draw them—what's most important is to remember how animals look and move. Simplified sketches of the skeleton can help you make sense of the way a creature changes form.
You'll easily be able to locate anatomical diagrams on the Internet (veterinary sites often have helpful diagrams) or at your local library. Your vet might have a skeleton you can look at, or observing the three-dimensional skeleton at a science museum is excellent drawing practice.
Create a basic structural sketch and a detailed value drawing of the skull from several angles. Create detailed studies of the paws, hooves, or claws, and do a sketch of the full skeleton. Pay particular attention to the joints and any bone that is close to the surface of the skin. Do a sketch showing the main muscle groups and tendons.