An animal halfway between an okapi and a giraffe in neck length is easy to imagine: take a short neck and stretch it. Fossils allow a more demanding question. As a neck lengthens, do all its bones change together, or can different features and regions follow different paths?
Melinda Danowitz, Rebecca Domalski and Nikos Solounias investigated the neck of Samotherium major, an extinct giraffid with proportions between the two living genera. Their 2015 study in Royal Society Open Science showed that its intermediate condition was much richer than a single measurement of length.
A rare chance to follow most of a fossil neck
Fossil research often depends on isolated vertebrae. One bone can preserve a useful feature, but it cannot show how the neck’s anatomy changes from the head towards the shoulders. The Samotherium material, originating from Samos in Greece and housed in museum collections, included a nearly complete cervical series.
The researchers examined its bones alongside giraffe and okapi specimens. They described joint surfaces, ridges and projecting processes and measured their dimensions. Ratios, such as vertebral length relative to width, helped distinguish differences in shape from the fact that the animals were different sizes.
The comparison was divided into upper-neck vertebrae, C2–C3, and lower-neck vertebrae, C5–C7. These labels count positions behind the skull. Separating the regions mattered because a bone close to the head and one near the trunk do not necessarily perform the same mechanical role.
Samotherium was a relative on an extinct branch of the family, not a demonstrated direct ancestor of modern giraffes or okapis. Its value is that it preserves an anatomical combination no living giraffid provides. It helps test what an intermediate body plan actually contains.
“Between” can mean a mixture
In the upper neck, Samotherium combined features resembling either of the living genera. Some joint-related structures were more giraffe-like, while others more closely resembled okapi anatomy. One feature did not automatically predict the state of the next.
For example, the elongated projections carrying joints at the front of certain vertebrae resembled the giraffe condition, while the broader joint surfaces towards the back more closely matched the okapi. These structures participate in connections between neighbouring bones. Their combination shows why the neck cannot be described adequately as merely an okapi neck enlarged to a different scale.
The term mosaic captures this kind of anatomy: a structure brings together traits that resemble different comparisons. It does not mean the animal was a hybrid between a giraffe and an okapi. It describes the pattern of similarities visible in the bones.
The team’s measurements supported that interpretation. Across different features of the upper vertebrae, Samotherium tended to fall closer to one living comparison or the other, rather than occupying the same middle position for everything.
Farther down, individual features had intermediate forms
The lower neck told a somewhat different story. Here, several features themselves lay between the giraffe and okapi conditions.
The sixth cervical vertebra offered particularly clear examples. On its underside, an okapi has a ridge continuing along the vertebral body, whereas the corresponding ridge is absent in the giraffe comparison. In Samotherium, it was developed towards the front and absent towards the rear.
Another part of the same vertebra, a plate-like projection on its lower side, was complete in okapi and deeply excavated in giraffe. The fossil had a partial notch. The anatomical middle was visible in the shape of one structure, rather than only in a mixture of separate giraffe-like and okapi-like traits.
That difference gives “intermediate” two useful meanings. The upper neck combined contrasting states; the lower neck included states between the contrasts. Neither is captured by a total-neck-length measurement.
Bones can suggest posture, with care
The researchers also examined features that might reveal how Samotherium held its neck. They considered the position of a projection on the first vertebra, the relatively short spine on C7 and aspects of the skull’s palate. Together, these resembled features they associated with a relatively upright neck.
They proposed that Samotherium carried its neck fairly vertically. That is an inference from bone shape and anatomical comparisons, not a posture directly preserved in a living animal. Fossil joints and muscle-attachment features constrain a reconstruction while leaving uncertainty about habitual movement and soft tissues.
The study also found distinctive Samotherium features that did not fit either living comparison. Its anatomy was its own viable arrangement, not an unfinished version of a modern giraffe.
Evolution changes relationships between parts
Our giraffe neck-evolution guide covers the larger question of how long necks arose. This fossil study contributes something more specific: evidence that different regions and features can change in different combinations.
A later mechanical comparison of first thoracic vertebrae reached a complementary problem from living mammals. It found that the giraffe’s neck-like first chest vertebra experienced relatively high compressive stress in a standardised model, suggesting that mobility and support may be distributed across neighbouring parts of the spine. The studies use different methods, but both caution against making one bone or one dimension represent the entire neck.
More complete cervical series from other extinct giraffids could test whether the same regional patterns recur. Models that include joints and plausible soft tissues could then explore what those combinations allowed the animals to do. The first task, accomplished here, was to describe the intermediate anatomy in enough detail to make those questions concrete.
Sources
Melinda Danowitz, Rebecca Domalski, Nikos Solounias (2015). The cervical anatomy of Samotherium, an intermediate-necked giraffid. Royal Society Open Science. DOI: 10.1098/rsos.150521. Read the full paper.
