Ptilodontoidea is a group of extinct

mammals Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

from the

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...

. They were generally small, somewhat

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...

-like creatures of the extinct order

Multituberculata Multituberculata (commonly known as multituberculates, named for the multiple tubercles of their teeth) is an extinct order of rodent-like mammals with a fossil record spanning over 130 million years. They first appeared in the Middle Jurassic, a ...

. Some of these genera boast a great many species, though remains are generally sparse. ''

Ptilodus ''Ptilodus'' (meaning "soft-haired") is a genus of mammals from the extinct order of Multituberculata, and lived during the Paleocene in North America. ''Ptilodus'' was a relatively large multituberculate of in length, which is about the same s ...

'' is among the best known, and there's a tendency to depict it as an analog of a

squirrel Squirrels are members of the family Sciuridae, a family that includes small or medium-size rodents. The squirrel family includes tree squirrels, ground squirrels (including chipmunks and prairie dogs, among others), and flying squirrels. Squ ...

. Upper

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

remains are known from North America and Europe. Later representatives (

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), E ...

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

) hail from North America, Europe and Asia. These were some of the last multituberculates, and they are within the suborder

Cimolodonta Cimolodonta is a taxon of extinct mammals that lived from the Cretaceous to the Eocene. They were some of the more derived members of the extinct order Multituberculata. They probably lived something of a rodent-like existence until their ...

. The superfamily is further divided into the following families: *

Neoplagiaulacidae Neoplagiaulacidae is a family of mammal within the extinct order Multituberculata. Fossil remains are known from the Upper Cretaceous through to the latest Eocene/early Oligocene. Representatives have been found in North America, Europe and Asi ...

- 10 genera; *

Ptilodontidae Ptilodontidae is a family of primitive mammals within the extinct order Multituberculata. Representatives are known from the Upper Cretaceous and Paleocene of North America. The Ptilodontidae family was originally named Ptilodontinae and classi ...

- 4 genera; *

Cimolodontidae Cimolodontidae is a family of fossil mammals within the extinct order Multituberculata. Representatives are known from the Upper Cretaceous and Paleocene of North America. The family Cimolodontidae was named by Othniel Charles Marsh in 1889 a ...

- possibly 3 genera. The affinities of ''

Neoliotomus ''Neoliotomus'' is a genus of North American mammal from the Paleocene. It existed in the age immediately following the extinction of the last dinosaurs and was a member of the extinct order Multituberculata. It lies within the suborder Cimolo ...

'' are less clear, though it seems to fit somewhere within the superfamily.

References

* Kielan-Jaworowska Z & Hurum JH (2001), "Phylogeny and Systematics of multituberculate mammals." ''Paleontology'' 44, p. 389-429. * Much of this information has been derived fro

''MESOZOIC MAMMALS; Ptilodontoidea, an Internet directory''. {{Taxonbar, from=Q7257049 Ptilodontoids, Cretaceous mammals Paleocene mammals Eocene mammals Eocene extinctions