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Willwood Formation

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Coordinates: 44°30′N 108°00′W / 44.5°N 108.0°W / 44.5; -108.0
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Willwood Formation
Stratigraphic range: Thanetian-Ypresian (Clarkforkian-Bridgerian)
~56–48 Ma
TypeGeological formation
Sub-unitsGray Bull beds, Sand Coulee beds, Sand Creek Facies, Wa-1 Zone
Lithology
PrimaryMudstone, shale
OtherSandstone, conglomerate
Location
Coordinates44°30′N 108°00′W / 44.5°N 108.0°W / 44.5; -108.0
Approximate paleocoordinates49°12′N 90°48′W / 49.2°N 90.8°W / 49.2; -90.8
Region Wyoming
Country USA
ExtentBighorn Basin
Type section
Named forShale, mudstone, limestone
Willwood Formation is located in the United States
Willwood Formation
Willwood Formation (the United States)
Willwood Formation is located in Wyoming
Willwood Formation
Willwood Formation (Wyoming)

The Willwood Formation is a sedimentary sequence deposited during the late Paleocene to early Eocene, or Clarkforkian, Wasatchian and Bridgerian in the NALMA classification.[1][2]

Description

It consists of fine grained clastic rocks (mudstone and shale) interbedded with medium grained clastic rocks (sandstone) and sporadic conglomerates. The formation underlies portions of the Bighorn Basin of Big Horn, Hot Springs, Park and Washakie counties of Wyoming.[3]

Dating

Radiometric dating of volcanic tuffs, combined with comparisons with other formations using magnetostratigraphy, using numerous samples from various levels of the formation suggest an age range of 55 – 52 million years ago, placing the Paleocene-Eocene boundary near the base of the formation.[4]

Fossil content

Trace fossils have been found in the Willwood Formation.[5] Fossil birds include Gastornis, Neocathartes and Paracathartes. A fossil alligatorid, namely Orthogenysuchus, was also found in this formation.

Mammals

Cimolestans
Genus Species Presence Material Notes Images
Palaeosinopa P. incerta Bighorn Basin.[6] A pantolestid.
P. lutreola Bighorn Basin.[6] A pantolestid.
P. veterrima Bighorn Basin.[6] A pantolestid.
Eulipotyphlans
Genus Species Presence Material Notes Images
Batodonoides B. vanhouteni Locality SC-303, situated at the 2,110 m level of the formation.[7] Maxilla and dentaries.[7] A geolabidid.
File:The smallest mammal (5040381547).jpg
Primatomorphs
Genus Species Presence Material Notes Images
Anemorhysis A. pattersoni Upper part of the formation. [8] An omomyid.
A. wortmani Upper part of the formation. [8] An omomyid.
Arapahovius A. advena Northwest Wyoming.[9] An omomyid.
Cantius C. abditus A substantially complete skull and mandible.[10] An adapiform.
Chlororhysis C. incomptus Upper part of the formation. [8] An omomyid.
Micromomys M. willwoodensis Clark's Fork Basin.[11] A micromomyid.
Microsyops M. latidens Southern Bighorn Basin.[12] Over a thousand specimens.[12] A plesiadapiform.
Phenacolemur P. willwoodensis Upper part of the formation.[13] A paramomyid.
Steinius S. annectens Northwest Wyoming.[9] An omomyid.
Tatmanius T. szalayi Northwest Wyoming.[9] An omomyid.
Ungulates
Genus Species Presence Material Notes Images
Xenicohippus Lower part of the Upper Willwood Formation. [14] A hyracotheriine.

Reptiles

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
Birds
Genus Species Presence Material Notes Images
Diatryma D. gigantea Several specimens.[15] Now deemed a junior synonym of Gastornis.
Eogeranoides E. campivagus "Fragmentary tibiotarsus and tarsometatarsus remains".[16] A dubious geranoidid, may be a junior synonym of Paragrus prentici.
Gastornis G. gigantea Several specimens.[15] A gastornithiform.
Geranoides G. jepseni Elk Creek, Bighorn Basin.[16] A geranoidid, now deemed a junior synonym of Palaeophasianus meleagroides.
Microolithus M. wilsoni Partial eggs.[17] Fossil bird eggs.
Palaeophasianus "P." incompletus "A fragmentary distal end of a tarsometatarsus".[16] A very large possible geranoidid, may actually belong to the genus Paragrus or be outside Geranoididae entirely.
P. meleagroides Elk Creek, Bighorn Basin.[16] A geranoidid.
?P. sp. AMNH 5156.[16] A geranoidid.
Paracathartes P. howardae [18] A lithornithid.
Paragrus P. prentici [16] A geranoidid.
Primoptynx P. poliotauros Specimen including all major postcranial bones.[19] A large owl.
Sandcoleus S. copiosus Clark Quadrangale, Park County, Wyoming.[20] "Two articulated partial skeletons and a number of other elements".[20] A sandcoleid mousebird.
Crocodilians
Genus Species Presence Material Notes Images
Orthogenysuchus O. olseni [21] A caiman.
Testudines
Genus Species Presence Material Notes Images
Gomphochelys G. nanus Southeastern Bighorn Basin, Washakie County, Wyoming.[22] A dermatemydid.

Invertebrates

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
Insects
Genus Species Presence Material Notes Images
Naktodemasis N. bowni Bighorn Basin.[23] "Burrows composed of nested ellipsoidal packets backfilled with thin, tightly spaced, menisci subparallel to the bounding packet."[23] Burrows likely constructed by burrowing bugs or cicada nymphs.[23]

Wasatchian correlations

Wasatchian correlations in North America
Formation Wasatch DeBeque Claron Indian Meadows Pass Peak Tatman Willwood Golden Valley Coldwater Allenby Kamloops Ootsa Lake Margaret Nanjemoy Hatchetigbee Tetas de Cabra Hannold Hill Coalmont Cuchara Galisteo San Jose Ypresian (IUCS) • Itaboraian (SALMA)
Bumbanian (ALMA) • Mangaorapan (NZ)
Basin Powder River
Uinta
Piceance
Colorado Plateau
Wind River
Green River
Bighorn		 Piceance
Colorado Plateau


Wind River



Green River





Bighorn		 Williston Okanagan Princeton Buck Creek Nechako Sverdrup Potomac GoM Laguna Salada Rio Grande North Park Raton Galisteo San Juan
Willwood Formation is located in North America
Willwood Formation
Willwood Formation
Willwood Formation
Willwood Formation
Willwood Formation
Willwood Formation
Willwood Formation
Willwood Formation
Willwood Formation
Willwood Formation
Willwood Formation
Willwood Formation
Willwood Formation
Willwood Formation
Willwood Formation
Willwood Formation
Willwood Formation
Willwood Formation
Willwood Formation
Willwood Formation
Willwood Formation
Willwood Formation (North America)
Country  United States  Canada  United States  Mexico  United States
Copelemur
Coryphodon
Diacodexis
Homogalax
Oxyaena
Paramys
Primates
Birds
Reptiles
Fish
Insects
Flora
Environments Alluvial-fluvio-lacustrine Fluvial Fluvial Fluvio-lacustrine Fluvial Lacustrine Fluvio-lacustrine Deltaic-paludal Shallow marine Fluvial Shallow marine Fluvial Fluvial
Wasatchian volcanoclastics

Wasatchian fauna

Wasatchian flora
Volcanic Yes No Yes No Yes No Yes No Yes No

See also

References

  1. ^ Willwood Formation at Fossilworks.org
  2. ^ Neasham & Vondra, 1972
  3. ^ "Willwood Formation". USGS.
  4. ^ Tauxe et al., 1994
  5. ^ Bown & Kraus, 1982
  6. ^ a b c Dunn, Rachel H.; Rose, Kenneth D. (2015-07). "Evolution of early Eocene Palaeosinopa (Mammalia, Pantolestidae) in the Willwood Formation of the Bighorn Basin, Wyoming". Journal of Paleontology. 89 (4): 665–694. doi:10.1017/jpa.2015.31. ISSN 0022-3360. {{cite journal}}: Check date values in: |date= (help)
  7. ^ a b Bloch, Jonathan I.; Rose, Kenneth D.; Gingerich, Philip D. (1998-08). "New Species of Batodonoides (Lipotyphla, Geolabididae) from the Early Eocene of Wyoming: Smallest Known Mammal?". Journal of Mammalogy. 79 (3): 804. doi:10.2307/1383090. ISSN 0022-2372. {{cite journal}}: Check date values in: |date= (help)
  8. ^ a b c Bown, Thomas M.; Rose, Kenneth D. (1984). "Reassessment of Some Early Eocene Omomyidae, with Description of a New Genus and Three New Species". Folia Primatologica. 43 (2–3): 97–112. doi:10.1159/000156175. ISSN 0015-5713.
  9. ^ a b c Bown, Thomas M.; Rose, Kenneth D. (1991-06-01). "Evolutionary relationships of a new genus and three new species of Omomyid primates (Willwood Formation, Lower Eocene, Bighorn Basin, Wyoming)". Journal of Human Evolution. 20 (6): 465–480. doi:10.1016/0047-2484(91)90020-V. ISSN 0047-2484.
  10. ^ Rose, K.; Macphee, R.; Alexander, J. P. (1999). "Skull of Early Eocene Cantius abditus (Primates:Adapiformes) and its phylogenetic implications, with a reevaluation of "Hesperolemur" actius". American journal of physical anthropology. doi:10.1002/(SICI)1096-8644(199908)109:4<523::AID-AJPA8>3.0.CO;2-U.
  11. ^ Rose, Kenneth D.; Bown, Thomas M. (1982). "New Plesiadapiform Primates from the Eocene of Wyoming and Montana". Journal of Vertebrate Paleontology. 2 (1): 63–69. ISSN 0272-4634.
  12. ^ a b Selig, Keegan R.; Silcox, Mary T. (2021-09-09). "The largest and earliest known sample of dental caries in an extinct mammal (Mammalia, Euarchonta, Microsyops latidens) and its ecological implications". Scientific Reports. 11 (1): 15920. doi:10.1038/s41598-021-95330-x. ISSN 2045-2322.
  13. ^ Silcox, Mary T.; Rose, Kenneth D.; Bown, Thomas M. (2008-11). "Early Eocene Paromomyidae (Mammalia, Primates) from the southern Bighorn Basin, Wyoming: Systematics and evolution". Journal of Paleontology. 82 (6): 1074–1113. doi:10.1666/07-116.1. ISSN 0022-3360. {{cite journal}}: Check date values in: |date= (help)
  14. ^ Bown, Thomas M.; Kihm, Allen J. (1981). "Xenicohippus, an Unusual New Hyracotheriine (Mammalia, Perissodactyla) from Lower Eocene Rocks of Wyoming, Colorado and New Mexico". Journal of Paleontology. 55 (1): 257–270. ISSN 0022-3360.
  15. ^ a b Witmer, Lawrence M.; Rose, Kenneth D. (1991). "Biomechanics of the Jaw Apparatus of the Gigantic Eocene Bird Diatryma: Implications for Diet and Mode of Life". Paleobiology. 17 (2): 95–120. ISSN 0094-8373.
  16. ^ a b c d e f Mayr, Gerald (2016-09). "On the taxonomy and osteology of the Early Eocene North American Geranoididae (Aves, Gruoidea)". Swiss Journal of Palaeontology. 135 (2): 315–325. doi:10.1007/s13358-016-0117-2. ISSN 1664-2384. {{cite journal}}: Check date values in: |date= (help)
  17. ^ JACKSON, FRANKIE D.; VARRICCHIO, DAVID J.; CORSINI, JOSEPH A. (2013). "AVIAN EGGS FROM THE EOCENE WILLWOOD AND CHADRON FORMATIONS OF WYOMING AND NEBRASKA". Journal of Vertebrate Paleontology. 33 (5): 1190–1201. ISSN 0272-4634.
  18. ^ Harrison, C. J. O. (1979). "A new cathartid vulture from the lower Eocene of Wyoming". Tertiary Research Special Papers. 5: 29–39.
  19. ^ Mayr, Gerald; Gingerich, Philip D.; Smith, Thierry (2020-03-03). "Skeleton of a new owl from the early Eocene of North America (Aves, Strigiformes) with an accipitrid-like foot morphology". Journal of Vertebrate Paleontology. 40 (2): e1769116. doi:10.1080/02724634.2020.1769116. ISSN 0272-4634.
  20. ^ a b Zelenkov, Nikita V.; Dyke, Gareth J. (2008-11). "THE FOSSIL RECORD AND EVOLUTION OF MOUSEBIRDS (AVES: COLIIFORMES)". Palaeontology. 51 (6): 1403–1418. doi:10.1111/j.1475-4983.2008.00814.x. {{cite journal}}: Check date values in: |date= (help)
  21. ^ Mook, C. C. (1924). "A new crocodilian from the Wasatch Beds". American Museum Novitates (137): 1–4.
  22. ^ BOURQUE, JASON R.; HUTCHISON, J. HOWARD; HOLROYD, PATRICIA A.; BLOCH, JONATHAN I. (2015). "A NEW DERMATEMYDID (TESTUDINES, KINOSTERNOIDEA) FROM THE PALEOCENE-EOCENE THERMAL MAXIMUM, WILLWOOD FORMATION, SOUTHEASTERN BIGHORN BASIN, WYOMING". Journal of Vertebrate Paleontology. 35 (2): 1–19. ISSN 0272-4634.
  23. ^ a b c Smith, Jon J.; Hasiotis, Stephen T.; Kraus, Mary J.; Woody, Daniel T. (2008-03). "Naktodemasis bowni: New ichnogenus and ichnospecies for adhesive meniscate burrows (AMB), and paleoenvironmental implications, Paleogene Willwood Formation, Bighorn Basin, Wyoming". Journal of Paleontology. 82 (2): 267–278. doi:10.1666/06-023.1. ISSN 0022-3360. {{cite journal}}: Check date values in: |date= (help)

Bibliography

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