''Didymictis'' ("double

weasel Weasels are mammals of the genus ''Mustela'' of the family Mustelidae. The genus ''Mustela'' includes the least weasels, polecats, stoats, ferrets, and European mink. Members of this genus are small, active predators, with long and slend ...

") is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of placental mammals from extinct subfamily Didymictinae within extinct family Viverravidae, that lived in

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

and

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

from the late

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), ...

to middle

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

Description

''Didymictis'' is the only viverravid genus for which there are considerable postcranial remains. The genus was primarily terrestrial but at least partly cursorial, similar to a

civets A civet () is a small, lean, mostly nocturnal mammal native to tropical Asia and Africa, especially the tropical forests. The term ''civet'' applies to over a dozen different species, mostly from the family Viverridae. Most of the species's div ...

. ''Didymictis'' had an elongated and relatively large skull with small and low braincase and a long and narrow basicranial region. The occipital and sagittal crests are very high. The limbs are of moderate length with subdigitigrade and five-toed feet. The dentition () contrasts those of basal carnivoraforms by the sharp differentiation between sectorial and tubercular dentition, the loss of the last molar and an elongated second molar, similar to the dentition in

bears Bears are carnivoran mammals of the family Ursidae (). They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats throughout most o ...

and

raccoons The raccoon ( or , ''Procyon lotor''), sometimes called the North American, northern or common raccoon (also spelled racoon) to distinguish it from Procyonina, other species of raccoon, is a mammal native to North America. It is the largest ...

. Comparing ''Didymictis'' to '' Vulpavus'', a much smaller and more agile carnivoraform, Heinrich and Rose in 1997 noted that ''Didymictis''' limbs, especially the hindlimb, are similar to those in extant carnivorans adapted for speed, and the forelimbs to some extent are specialized to digging. The authors concluded that ''Didymictis'' was a relatively specialized terrestrial carnivore capable of hunting with speed or pursuing by digging.

Classification and phylogeny

History of species and classification

''D. protenus'' is known from the earliest through late

Wasatchian The Wasatchian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 55,400,000 to 50,300,000 years Before Present, BP lasting . I ...

(early Eocene) of western North America.P. D. Polly (1997
"Ancestry and Species Definition in Paleontology: A Stratocladistic Analysis of Paleocene-Eocene Viverravidae (Mammalia, Carnivora) from Wyoming."
Contributions from the Museum of Paleontology, University of Michigan 30(1):1-53

Cope A cope ( ("rain coat") or ("cape")) is a liturgical long mantle or cloak, open at the front and fastened at the breast with a band or clasp. It may be of any liturgical colour. A cope may be worn by any rank of the Catholic or Anglican clerg ...

assigned his specimen, "one entire and a portion of the other mandibular ramus, with teeth well preserved", to the

creodont Creodonta ("meat teeth") is a former order of extinct carnivorous placental mammals that lived from the early Paleocene to the late Miocene epochs in North America, Europe, Asia and Africa. Originally thought to be a single group of animals ance ...

genus '' Limnocyon'' and named his new species ''L. protenus''. Cope later created a new genus and renamed his species ''Didymictis protenus''. ''D. proteus'' is known from the late Paleocene and earliest Eocene of Wyoming and the only species present in the

Tiffanian The Tiffanian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 60,200,000 to 56,800,000 years BP lasting . It is usually co ...

and

Clarkforkian The Clarkforkian North American Stage, on the geologic timescale, is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 56,800,000 to 55,400,000 years BP lasting . Considered t ...

stages. It is slightly larger than ''D. leptornylus'' and slightly smaller than ''D. protenus''. Simpson in 1937 named a new subspecies, ''Didymictis protenus proteus'', which Polly in 1997 reranked as the species ''D. proteus''. Dorr in 1952 described ''Didymictis dellensis'', which Gingerich and Winkler in 1985 included in ''Protictis dellensis''.P. D. Gingerich and D. A. Winkler (1985
"Systematics of Paleocene Viverravidae (Mammalia, Carnivora) in the Bighorn Basin and Clark's Fork Basin, Wyoming."
Contributions from the Museum of Paleontology, University of Michigan 27(4):87-128 Polly in 1997 finally included these species in ''D. proteus''. ''D. leptomylus'' is known from the early Wasatchian of western North America, but by far fewer specimens than ''D. proteus''. ''D. vancleveae'' is known from a fragmented jaw with several teeth (Colorado) described by Robinson in 1966 and another tooth (Wyoming) tentatively assigned to this species. Robinson described ''D. vancleveae'' as larger than ''D. altidens'' and probably the youngest ''Didymicits''. He assumed that the genus grew larger as it evolved.

Taxonomy

References

External links

* {{Taxonbar, from=Q5274262 Viverravids Paleocene mammals Paleocene mammals of North America Prehistoric placental genera Taxa named by Edward Drinker Cope