The first and second cervical vertebrae of all mammals are modified into specific vertebrae called the atlas and axis vertebrae. I have pictured a baleen whale atlas, which measures about 12 inches across. The axis is directly behind it in the picture as it appears in my display case (hence the reflection). The atlas and axis nestle together followed by 5 more cervical vertebrae. The cervical vertebrae, C3-c7, are very thin in the whale, relative to thoracic or lumbar vertebrae, while in the giraffe the same 7 cervical vertebrae are extremely long. The evolutionary difference accounts for the long neck of the giraffe (not more cervical vertebrae). Both have the same number.