I take great care with the anatomical accuracy of my drawings. This is what gives a work of art, no differently than the figure itself, a sense of power, speed or agility. It is what makes a work convincing. If the anatomical structure is wrong, the piece cannot convey a sense of life.The structure of the head is of fundamental importance to the character and expression of a species. If you don't get the head right, the rest hardly matters. This grey wolf skull was borrowed from the Royal Ontario Museum, and provided minute detail on skull shape and dentition.

Once the head is well understood and the character captured, the overall structural anatomy of the individual is established. The musculoskeletal framework is the architecture for the entire figure, and is unique to each species. Veterinary and anatomical texts are invaluable for checking details. The following books are still the standards for artists' reference:
Calderone, Frank. Animal Painting and Anatomy
Ellenberger, Wilhelm. Atlas of Animal Anatomy for Artists
Lanteri, Edouard. Modeling and Sculpting Animals
Muybridge, Edward. Animals in Motion
With as much anatomical information as I can gather, I build an accurate picture of the particular species in which I am interested. Some sculptors use relative units of external measure, including coat, to come up with a proportionate model. I work from the inside out, preferring to visualize and build the skeleton, muscling, fat and coat to create the final figure. Outside proportions change dramatically when the body moves, and only the skeletal framework can keep the integrity of the figure accurate. This gives me an accurate picture of the animal, including the location of joints, the length of bony levers and their range of motion, the depth of muscle mass and coat coverage. External form and movement can be understood in terms of the mechanics of what's going on inside.

With a good understanding of the anatomy of a species, I'm no longer tethered to the use of photographic reference and am free to depict my subjects as I please. This anatomical knowledge, combined with studies of gait and gesture, and observation from life, give an artist a fundamental grasp of the creature in question. Drawings like the one below are done completely from memory.

 

Studio Page 1, Forming the Creative Idea; how an artwork is conceived

Studio Page 2, Gathering Reference Material; the use of photograhy in art