Ophthalmosaurus was a 20 foot long ichthyosaur which swam in the oceans around Europe during the middle and late Jurassic Period. It is named after its distinctive large eyes.
The coloration in the illustration that you see below is based upon the Spotted Dolphin (Stenella frontalis). This drawing was made with No.2 pencil, No.3 pencil, and marker for the eye.
UPDATE: Below is a revised version which I made, which has more accurate body proportions. This drawing was made with No.2 pencil, No.3 pencil, and Prismacolor colored pencils.
Keep your pencils, and your scientific information, sharp.