Gnathabelodon is an extinct proboscidean (elephant) genus endemic to North America that includes species that lived during the Middle to Late Miocene. They were called "Spoon-billed Mastodons" since their lower jaw was elongated and shaped like a shoe-horn or spoon. The genus Gnathabelodon consists of two species: Thorpe's Spoon-billed Mastodon (G. thorpei) and Buckner's Spoon-billed Mastodon (G. buckneri). The flaring of the tip of their lower jaw was similar to that of the "shovel-tuskers" (Platybelodon

Platybelodon

Platybelodon was a genus of large herbivorous mammal related to the elephant . It lived during the Miocene Epoch, about 15-4 million years ago, and ranged over Africa, Europe, Asia and North America...

 and Amebelodon

Amebelodon

Amebelodon is a member of a diverse group of primitive proboscideans called gomphotheres, a group that also gave rise to the modern elephants and their close relative the mammoth. The most striking attribute of this animal is its lower tusks, which are narrow, elongated,and distinctly flattened...

) however Gnathabelodon species are distinct in having no lower tusks whilst the "shovel tuskers" have broad, flattened lower tusks. The upper tusks are large and curve outwards and upwards. In respects to dentition and overall body form, it was similar to other species of Gomphotherium.

Sources

• A Pictorial Guide to Fossils by Gerard Ramon Case
• Classification of Mammals by Malcolm C. McKenna and Susan K. Bell