Didymictis Explained

Didymictis ("double weasel") is an extinct genus of placental mammals from extinct subfamily Didymictinae within extinct family Viverravidae, that lived in North America and Europe from the late Paleocene to middle Eocene.[1] [2] [3] [4]

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.[5]

Didymictis has 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 contrast 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 and raccoons.[6]

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 carnivornas 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.[7]

Classification and phylogeny

History of species and classification

D. protenus is known from the earliest through late Wasatchian (early Eocene) of western North America.[8] Cope assigned his specimen, "one entire and a portion of the other mandibular ramus, with teeth well preserved", to the creodont 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 and Clarkforkian stages. It is slightly larger than D. leptornylus and slightly smaller than D. protenus.[8] Simpson in 1937 named a new subspecies, Didymictis protenus proteus, which Polly in 1997 reranked as the species D. proteus.[8] Dorr in 1952 described Didymictis dellensis, which Gingerich and Winkler in 1985 included in Protictis dellensis.[9] 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.[8]

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

Genus: †Didymictis
Species: Distribution of the species and type locality: Age:
†D. altidens [10] (Colorado and Wyoming)54,9 - 46,2 Ma
†D. dellensis [11] (Saskatchewan)
(Wyoming)[12] 		60,9 - 54,9 Ma
†D. leptomylus [13] (Colorado and Wyoming[14])54,9 - 50,5 Ma
†D. protenus [15] (Colorado,New Mexico and Wyoming)56,2 - 50,5 Ma
†D. proteus (Alberta)
(Colorado, South Carolina and Wyoming)		60,9 - 50,5 Ma
†D. vancleveae [16] (Colorado and Wyoming[17])50,5 - 46,2 Ma
†D. sp. [Erquelinnes, Hainaut, Belgium] [18] (Hainaut Province)56,0 - 55,2 Ma

External links

Notes and References

  1. Cope . E. D. . General Notes: The Northern Wasatach Fauna . December 1880 . American Naturalist . 14 . 12 . 908 . 10.1086/272689 .
  2. Book: McKenna . Malcolm C. . Bell . Susan K. . Classification of Mammals Above the Species Level . 16 March 2015 . 1997 . Columbia University Press . New York . 978-0-231-11012-9.
  3. J. J. Flynn (1998.) "Early Cenozoic Carnivora ("Miacoidea")." In C. M. Janis, K. M. Scott, and L. L. Jacobs (eds.) "Evolution of Tertiary Mammals of North America. Volume 1: Terrestrial Carnivores, Ungulates, and Ungulatelike Mammals." Cambridge University Press, Cambridge.
  4. Book: Gunnell, G. F. . Eocene Biodiversity: Unusual Occurrences and Rarely Sampled Habitats . 2001 . Springer . 9780306465284.
  5. Heinrich . R. E. . Houde . P. . Postcranial anatomy of Viverravus (Mammalia, Carnivora) and implications for substrate use in basal Carnivora . 2006 . Journal of Vertebrate Paleontology . 26 . 2 . 422–435 . 10.1671/0272-4634(2006)26[422:paovmc]2.0.co;2 . 40158814 . 2014-09-13 . 2014-08-13 . https://web.archive.org/web/20140813145105/http://biology-web.nmsu.edu/~houde/phoude.htm . dead .
  6. Matthew . W. D. . William Diller Matthew . Paleocene faunas of the San Juan basin, New Mexico . 1937 . Transactions of the American Philosophical Society . New Series . 30 . 1 . 46–47 . 1-4223-7738-5 . 4673155 . 1937Natur.140...46C . 10.1038/140046a0 . 42553547.
  7. Heinrich . R. E. . Rose . K. D. . Postcranial morphology and locomotor behaviour of two early Eocene miacoid carnivorans, Vulpavus and Didymictis . 1997 . Palaeontology . 40 . 279–306 . dead . https://web.archive.org/web/20140913170531/http://www.palass-pubs.org/palaeontology/pdf/Vol40/Pages%20279-305.pdf . 2014-09-13.
  8. 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
  9. 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
  10. Cope . Edward D. . The Bad Lands of the Wind River and their Fauna . 1880 . The American Naturalist . 14 . 10 . 2449738 . 10.1086/272667 . 745–748.
  11. Dorr . J. A. . Early Cenozoic stratigraphy and vertebrate paleontology of the Hoback Basin, Wyoming . 1952 . Bulletin of the Geological Society of America . 63 . 1 . 59–94 . 10.1130/0016-7606(1952)63[59:ECSAVP]2.0.CO;2 . 1952GSAB...63...59D.
  12. R. Secord (2008.) "The Tiffanian Land-Mammal Age (middle and late Paleocene) in the northern Bighorn Basin, Wyoming." University of Michigan Papers on Paleontology 35:1-192
  13. Cope . Edward D. . General Notes: The Northern Wasatach Fauna . 1880 . American Naturalist . 14 . 908 . 10.1086/272689 .
  14. K. D. Rose, A. E. Chew, R. H. Dunn, M. J. Kraus, H. C. Fricke and S. P. Zack (2012.) "Earliest Eocene mammalian fauna from the Paleocene-Eocene Thermal Maximum at Sand Creek Divide, southern Bighorn Basin, Wyoming." University of Michigan Papers on Paleontology 36:1-122
  15. Cope . Edward D. . Notes on the Eocene and Pliocene Lacustrine Formations of New Mexico, Including Descriptions of Certain New Species of Vertebrates . 1874 . Annual Report of the Chief of Engineers for 1874 . Appendix FF .
  16. Robinson . P. . 1966 . Fossil Mammalia of Huerfano Formation, Eocene, of Colorado . Bulletin of the Peabody Museum of Natural History . 21 . 48–49. (Plate VII)
  17. Gunnell . G. F. . Bartels . W. S. . Gingerich . P. D. . Torre . V. . Wapiti Valley Faunas: Early and Middle Eocene Fossil Vertebrates from the North Fork of the Shoshone River, Park Country, Wyoming . 1992 . Contributions from the Museum of Paleontology, the University of Michigan . 28 . 11 . 247–287 . 2027.42/48547.
  18. Lours Dollo (1909.) "The fossil vertebrates of Belgium" Annals of the New York Academy of Sciences, 19(1):99 - 119

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