Giraffe neck is longer than thought Anatomical evidence for giraffe’s eighth “neck” vertebra

Researchers at the University of Tokyo demonstrated that the first thoracic vertebra of giraffe acts like a cervical vertebra. The additional “neck” vertebra enhances neck flexibility, and provides advantages in eating leaves of treetops and in drinking water on the ground beneath their long legs.

The giraffe possesses a unique body plan with an extraordinarily long and flexible neck. However, the giraffe neck, like the human, basically consists of just seven bony cervical vertebrae. Previous studies have assumed that the thoracic vertebrae are held fixed relative to each other and the majority of the head and neck movement occurs in the cervical vertebrae.

Graduate student Ms. Megu Gunji and Professor Hideki Endo at the University of Tokyo dissected giraffe carcasses donated from zoos around Japan, and described the musculoskeletal structure around neck-trunk junction of the giraffe. They found modifications of the musculoskeletal structure in this region, and demonstrated that the eighth vertebra (first thoracic vertebra) of the giraffe possesses high mobility similar to the cervical vertebrae. This suggests that the first thoracic vertebra, normally part of the body, functions as part of the neck in the giraffe. The additional neck vertebra acts as a fulcrum in neck movement, and contributes to enlarging a reachable space of head and neck in adult giraffes by about 50 cm. This unique vertebra enables the giraffe to both eat leaves from treetops and to drink water on the ground.

“Prior studies have assumed that the skeletal structure of the mammalian neck is basically unchanged,” says Ms Gunji. “However, the present study found a novel neck structure among mammals. This provides a new insight into the developmental mechanisms behind body structure and form in humans and other mammals.”