Small, medium or large?
It's not just a choice for coffee sizes; it also used to be a choice in neck length in the family giraffes belong to.
A US researcher has described the Samotherium, an extinct species of animal from the giraffidae family, which had a neck length between its modern day relatives the giraffe and the okapi.
While textbooks have used the animal, found in Samos, Greece, and other places around Eurasia, as an example of evolution, there hadn't been enough fossil evidence to back it up.
A study by Melinda Danowitz of the New York Institute of Technology College of Osteopathic Medicine, published by the Royal Society today, is the first time a complete fossil of the animal's neck has been described.
The Samotherium is closely related to the giraffe and, while it isn't a direct ancestor of the long-necked mammal or the short-necked okapi, had a "transitional neck" between the two living species.
Several cervical vertebrae of the Samotherium, comprising almost complete necks, have been found and have been housed in museums for around a century, though their anatomy and structure have never been fully described scientifically.
The animal shared similar a "mosaic of characteristics and dimensions that closely resemble either the okapi or the giraffe".
"[The Samotherium]'s proposed position is a key region in the evolutionary tree of giraffids as it represents a transitional stage of neck elongation," Ms Danowitz says.
The long neck of the giraffe allows it to eat vegetation from heights other animals can't reach, but the increased distance between the heart and brain mean an increase in blood pressure is needed to compensate.
Whereas the short neck of the okapi, native to the Democratic Republic of Congo, likely relates to fighting and/or feeding.