This next picture shows how I map out the wrinkles with basic lines, any shading at this point only acts as a guide also. Naturally an older elephant will have much deeper set wrinkles with darker areas of skin, the tusks will be left fairly pale so that they stand out against the trunk. Tusks grow throughout the elephant's life, but few will ever reach their full length due to breaking caused by wear. An African elephant uses them to dig, push trees, scrape etc. They are also useful to fight predators and even for fighting other elephants in the group to assert their superiority during the mating season. I have drawn a slight texture to them, I may decide to darken the underpart a little later on in the picture when I can see the balance of contrast further down the line.
The elephant's tusks are an extension of its canine teeth.