Named By: Richard Owen - 1845.
Synonyms: Bathmodon, Ectacodon, Lefalophodon, Loxolophodon, Manteodon, Metalophodon.
Classification: Chordata, Mammalia, Cimolesta, Pantodonta, Coryphodontidae.
Species: C. eocaenus (type), C. dabuensis, C. lobatus, C. oweni, C. proterus, C. ryani.
Size: Around 2.25 meters long, 1 meter tall at the shoulder.
Known locations: Across North America but particularly well known in the USA.
Time period: Selandian of the Paleocene through to Ypresian of the Eocene.
Fossil representation: Multiple individuals.
is one of the best known genera of pantodont, one of the earliest
major groups of large herbivorous mammals. Usually interpreted as
being similar to a modern hippopotamus, Coryphodon
were heavily built
with squat legs, the upper portion of which were longer than the
lower. This indicates that the legs were there for supporting a heavy
body rather than fast running. Coryphodon does
not seem to have been
in need of much in the way of defences however since most known
predators of the time seem to have been much smaller than Coryphodon.
Coryphodon had an enlarged pair of tusks in the upper jaw that were probably used for rooting up plants, although they may have also been used for display since male specimens have larger tusks. The other teeth in the mouth were suited for processing plants that had been grabbed by browsing. Popular opinion of Coryphodon however suggests that it was not an intelligent animal with the cranial cavity for the brain suggesting the total brain size relative to the total body size was one of the proportionately smallest known.
A 2009 paper authored by Jaelyn Eberle, Henry Fricke and John Humphrey in conjunction with the University of Colorado discussed the potential diet of Coryphodon in the June, 2009 issue of Geology. This study was focused upon the fossils of Coryphodon that that had been recovered from Ellesmere Island that lies west of northern Greenland. Ellesmere Island is situated within the Arctic Circle, and although it was much warmer and covered in forests back in the Eocene, it would still have experienced periods of constant daylight in the summer and constant nigh time in the winter.
The study which was centred around the isotopic study of tooth enamel revealed that during the summer period of extended daylight Coryphodon would eat soft vegetation such as flowering plants, aquatic plants and leaves. However during the extended periods of darkness when plant photosynthesis was impossible, Coryphodon would switch to a diet of leaf litter, twigs, evergreen needles and most revealingly fungi, an organism and food source that does not require light to grow. Not only does this study reveal the dietary range of Coryphodon, but it also reveals the behaviour of the northern populations living within the Arctic Circle. In this respect Coryphodon did not migrate south or hibernate, it simply switched between two seasonal food sources.
When Coryphodon fossils are compared to those of other pantodont genera in terms of size and relationship a scenario can be developed where the pantodont Barylambda was replaced by Coryphodon, while Coryphodon itself was ancestral to Hypercoryphodon.