Ontogenetic similarities between giraffe and sauropod neck osteological mobility

A growing giraffe’s neck may become more flexible, not less. A comparison of newborn and adult skeletons found that the longer adult neck could bend through a wider range. The same pattern appeared in a long-necked dinosaur, giving researchers a way to examine ancient movement through a living animal.

Daniel Vidal, Pedro Mocho and colleagues built virtual necks from scans of one newborn and one adult giraffe, then compared them with younger and older specimens of the dinosaur Spinophorosaurus. They rotated neighbouring bones until their joint surfaces were about to lose contact. They also checked whether the reconstructed giraffes could reproduce neck positions reported in living animals.

Both giraffe models could fold the neck back towards the body without fully separating the joints, but the adult model allowed greater movement. Its neck also contained proportionally less space between the bones. Elongation changed the geometry of the joints in ways that permitted wider bending. These are skeletal possibilities from very few specimens, not measurements of live neck flexibility or every restraint imposed by soft tissues. Nevertheless, a longer neck need not be a stiffer one—and giraffes provide a useful reality check for reconstructions of dinosaurs.