The Cervical Osteology of Okapia johnstoni and Giraffa camelopardalis

Part of a giraffe's chest backbone has features of a neck. The boundary between neck and chest is less straightforward than a count of bones suggests. Giraffes have seven neck vertebrae, yet the first vertebra carrying ribs resembles a continuation of the neck in several aspects of its shape.

Melinda Danowitz and Nikos Solounias compared six adult giraffe and eleven okapi skeletons in museum collections, taking detailed measurements from three of each. They described the neck bones and the transition into the chest, examining joint surfaces, projecting processes and the locations of structures where muscles attach. The short-necked okapi provided a comparison within the same family, making it possible to distinguish giraffe specialisations from shared features.

The giraffe's third through seventh neck vertebrae were unusually similar to one another, whereas the corresponding okapi bones changed shape more markedly along the sequence. The strongest anatomical transition towards the chest also occurred one vertebra farther back in giraffes. These are comparisons of skeletons, not measurements of movement or muscle forces in living animals. They reveal that elongating the giraffe neck involved reorganising a sequence of bones and its boundary with the chest, rather than simply making seven ordinary vertebrae longer.