Stagodontidae is an extinct family of carnivorous metatherian mammals that inhabited North America and Europe
Description
Currently, the family includes four genera,
Eodelphis,
Didelphodon,
Fumodelphodon and
Hoodootherium, which together include some seven different species.
In addition, the
Cenomanian species
Pariadens kirklandi might be a member of the family.
Carneiro and Oliveira (2017) considered the species
Eobrasilia coutoi from the early
Eocene (
Itaboraian) of
Brazil to be a stagodontid;
if confirmed it would make it the only known
Cenozoic and the only known
member of the family. Stagodontids were some of the largest known Cretaceous mammals, ranging from in mass.
One of the most unusual features of stagodontids are their robust, bulbous premolars, which are thought to have been used to crush
freshwater mollusks,
a diet that apparently evolved independently at least twice within this clade.
Postcranial remains suggest that stagodontids may have been semi-aquatic.
The most well described forms are found in
Laramidia, but they are also present on Appalachian and
sites, further leading credence to their aquatic habits.
Cretaceous fossils were also found in
France, suggesting a pan-Laurasian distribution for Cretaceous metatherians.
The evolution of Didelphodon and other large stagodontids (as well as large like Nanocuris) occurs after the local extinction of eutriconodont mammals, suggesting passive or direct ecological replacement.[G. W. Rougier, B. M. Davis, and M. J. Novacek. 2015. A deltatheroidan mammal from the Upper Cretaceous Baynshiree Formation, eastern Mongolia. Cretaceous Research 52:167-177] They are considered rare in any given fauna they appear in, probably due to their specialised habits.
Classification
Stagodontids were once thought to be closely related to the
Sparassodonta, but later studies suggest they belong to a more ancient branch of the
metatherian family tree, possibly closely related to
pediomyids,
being in particular closest to
Pariadens, which forms the immediate outgroup to Stagodontidae.
With the possible exception of
Eobrasilia (see above), stagodontids are last known from the
Maastrichtian, and are thought to have gone extinct in the
K-T Extinction.
