''Cimexomys'' is an extinct North American mammal that lived from the 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 ...

to the

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''pal ...

. For a while, it shared the world with

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

s, but outlived them. It was a member 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 ...

and lies 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 ...

. It is perhaps a member of the Paracimexomys group, though it is not certain. The genus ''Cimexomys'' ("bug mouse") was named by Sloan and Van Valen in 1965. Most remains are restricted to teeth. "Cimex" means "bug", with reference to the type locality of ''Cimexomys minor'' in the Bug Creek Anthills in

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columb ...

, United States. The inclusion of ''Cimexomys'' in the Paracimexomys group is tentative, (Kielan-Jaworowska & Hurum, 2001, p. 403). Some species are termed here as ''"Cimexomys"'', and they're listed towards the end. New species have previously been christened with great enthusiasm, and much reidentification has also occurred.

Species

Further names include ''"Cimexomys" bellus'', ''"C." clarki'' and ''"C." electus''.

''Cimexomys arapahoensis''

Age: Lower Paleocene of the Denver Formation in

Colorado Colorado (, other variants) is a state in the Mountain states, Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the wes ...

(United States)
"''C. arapahoensis'' is known from four dental and mandiblar fossils from the Alexander Locality of the Denver Formation (

) and is the largest known species of ''Cimexomyx''. I estimated its mass at about 120 g based on its lower first molar." (Eric W. Dewar, 2002) ''C. minor'' has also been identified from this location.

''Cimexomys gratus''

Age: Puercan (Paleocene) of the Polecat Bench Formation in

Wyoming Wyoming () is a state in the Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the southwest, and Colorado to the s ...

(USA). This animal weighed about 130 g, about five mice or a third of a rat.

''Cimexomys judithae''

This species (Sahni A. 1972) is also known as ''Paracymexomys judithae'' (Archibald J.D. 1982). Fossils come from the Campanian (Upper Cretaceous) of the

Two Medicine Formation The Two Medicine Formation is a geological formation, or rock body, in northwestern Montana and southern Alberta that was deposited between and (million years ago), during Campanian (Late Cretaceous) time. It crops out to the east of the Rocky M ...

(USA). A near complete dentition and skeletal elements were discovered at Egg Mountain, a site associated with a dinosaur nesting colony, though this wasn't the original material. ''C. judithae'' is reportedly more derived than other species, and the integrity of the genus is suspect, (as reflected here by the later entries for ''"Cimexomys"''). Montellano reassigned this species to the cimex genus in 1992. The body mass is estimated to have been around 20 g. Based on the new material from Montana, the authors "argued that ''Cimexomys'' is too primitive to be included among either the

Taeniolabidoidea Taeniolabidoidea is a group of extinct mammals known from North America and Asia. They were the largest members of the extinct order Multituberculata, as well as the largest non-therian mammals. ''Lambdopsalis'' even provides direct fossil eviden ...

or Ptilodontoidea. This agrees with our conclusion as we tentatively place ''Cimexomys'' in the informal "Paracimexomys group", which we erect for plesiomorphic (basal), poorly known members of the Cimolodonta", (Kielan-Jaworowska & Hurum, 2001, p. 393).

''Cimexomys minor''

(Sloan R.E. and Van Valen L. 1965)
Age: Upper Cretaceous - Lower Paleocene
Place: Hell Creek Formation, Montana and Denver Formation, Colorado (USA) and Ravenscrag Formation,

Saskatchewan Saskatchewan ( ; ) is a province in western Canada, bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and on the south by the U.S. states of Montana and North Dak ...

(Canada). Remains are small teeth of an eighth to a tenth of an inch in length. The animal weighed about 25 g, the same as a standard mouse.

''"Cimexomys" antiquus''

(Fox R.C. 1971). Fossils are known from the Santonian (Upper Cretaceous) of Utah. The type fossil is in

Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...

, Canada. It weighed about 30 g.

''Cimexomys gregoryi''

Fossil remains of the species ''"Cimexomys" gregoryi'' (Eaton J.G. 1993) have been found in Campanian (Upper Cretaceous)-aged strata in the USA. This species shows similarities to the genus '' Bryceomys''.

References

* Sahni (1972) ''Bulletin of the American Museum of Natural History'' 147 (6) * Sloan & Van Valen (1965), "Cretaceous mammals from Montana". ''Science'' 148, p. 220-227 * Fox (1971), ''Canadian J of Earth Sci'' 8, p. 916 * Kielan-Jaworowska Z & Hurum JH (2001), "Phylogeny and Systematics of multituberculate mammals". ''Paleontology'' 44, p. 389-429 {{Taxonbar, from=Q5120126 Cimolodonts Cretaceous mammals of North America Paleocene mammals of North America Santonian genus first appearances Paleocene genus extinctions Hell Creek fauna Milk River Formation Fossil taxa described in 1965 Prehistoric mammal genera