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Willwood Formation

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]

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)

Description

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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

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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

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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

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Afrotheres

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Afrotheres reported from the Willwood Formation
Genus Species Presence Material Notes Images
Apheliscus A. sp. Upper Gray Bull.[6] A macroscelidean.

Apatotheres

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Apatotheres reported from the Willwood Formation
Genus Species Presence Material Notes Images
Apatemys A. bellulus Lysite and Lost Cabin Zone.[7] Also found in the Wind River Formation.[7]
A. chardini Middle and possibly lower Gray Bull zone.[7] The smallest species of the genus.[7]
A. kayi The oldest known species of the genus.[7]
A. sp., cf. A. rodens Eastern side of Red Butte, and north of Sheep Mountain.[7] YPM 23476, 30582, AMNH 48999.[7] 3 very large specimens of Apatemys.[7]

Bats

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Bats reported from the Willwood Formation
Genus Species Presence Material Notes Images
cf. Icaronycteris cf. I. sp. Locality SC-29, Park County, Wyoming.[8] 3 fragmentary specimens.[8]
 

Cimolestans

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Cimolestans reported from the Willwood Formation
Genus Species Presence Material Notes Images
Azgonyx A. gunnelli Localities SC-67, SC-308 and SC-351.[9] A tillodont.
A. sp. Locality SC-67.[9] A larger tillodont than A. gunnelli.
Coryphodon C. sp. Localities FG-61, SC-67 and SC-139.[9] [10] A pantodont.
 
Didelphodus D. absarokae Lower Gray Bull to the upper part of the Lysite zones.[7] A palaeoryctid.
Ectoganus E. bighornensis Localities HG-3 and SC-67.[9] A taeniodont.
E. copei USGS 3838, with postcrania.[10] A taeniodont.
E. gliriformis A fragmentary femur (PU 13173).[10] A taeniodont.
Esthonyx E. bisculatus Jaws, teeth and a few postcranial remains.[10] A tillodont.
E. spatularius Bighorn Basin,[11] and locality SC-67.[9] Fragmentary left dentary.[9] A tillodont.
Megalesthonyx M. hopsoni Buffalo Basin.[12] A tillodont.
cf. Palaeoryctes cf. P. sp. "USGSD 1661, 2151, 3711".[7] A palaeoryctid.
Palaeosinopa P. incerta Lower to upper Gray Bull zone,Bighorn Basin.[7][13] A pantolestid also found in the Wind River and San Jose formations.[7]
P. lutreola Middle and upper Gray Bull zone, Bighorn Basin.[7][13] A pantolestid.
P. veterrima Lower Gray Bull through Lysite zones, Bighorn Basin.[7][13] More than 50 specimens.[7] A pantolestid.
P. sp. Lower part of the formation.[6] UM 69722 (a partial skull and mandible).[6] A pantolestid.
cf. Pararyctes cf. P. sp. "Yale locality 363 at the 190-m level of the Willwood Formation in the Elk Creek Facies".[7] UW 7028.[7] A palaeoryctid.

Eulipotyphlans

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Eulipotyphlans reported from the Willwood Formation
Genus Species Presence Material Notes Images
Auroralestes A. simpsoni Lower part of the formation, Sand Creek Facies.[7] UW 9616 (right P4-M2) and YPM 35156.[7] An erinaceid, originally named Eolestes.
Batodonoides B. vanhouteni Locality SC-303, situated at the 2,110 m level of the formation.[14] Maxilla and dentaries.[14] A geolabidid.
Centetodon C. neashami "Lower middle Gray Bull and upper Gray Bull zones".[7] A geolabidid.
C. patratus UCMP 44954 and YPM 23088, possibly also UCMP 44957, 44958, 44959.[7] A geolabidid.
Creotarsus C. lepidus "Lower Gray Bull beds, Coon Creek, Garland Road, Bighorn Basin".[7] "AMNH 16169, left ramus with P4-M2, and associated tarsal bones".[7] An animal of enigmatic affinities but may be an erinaceomorph.
cf. Dartonius cf. D. jepseni "YPM 30559, fragment of left ramus with P4-M1 and trigonid of M2".[7] An erinaceid, originally referred to as "Leptacodon" jepseni.[15]
Dormaaliidae Dormaaliid, sp. A Sand Creek Facies.[7] UW 7048, 9627.[7] An amphilemurid.
Eolestes E. simpsoni Lower part of the formation, Sand Creek Facies.[7] UW 9616 (right P4-M2) and YPM 35156.[7] Now renamed to Auroralestes.
Insectivora (?) gen. et. sp. indeterminate YPM locality 355, lower part of the middle Gray Bull zone.[7] "YPM 30860, fragment of right ramus with M1(?) and trigonid of M2(?)".[7] Teeth which may represent an unusual insectivore or microchiropteran.
cf. Leipsanolestes cf. L. sp. Sand Creek Facies.[7] UW 9672, a left molar.[7] An erinaceid.
Leptacodon cf. "L." jepseni "YPM 30559, fragment of left ramus with P4-M1 and trigonid of M2".[7] Actually an erinaceid, now reassigned to a new genus, Dartonius.[15]
L. rosei Localities SC-188 and SC-29, Park County, Wyoming.[8] 3 dentaries, 2 maxillae, several isolated teeth and possibly a metatarsal.[8] A nyctitheriid.
Cf. L. sp. A single lower molar.[8] A nyctitheriid.
Limaconyssus L. habrus Locality SC-29, Park County, Wyoming.[8] Left dentary.[8] A nyctitheriid.
Macrocranion M. nitens Uppermost part of the lower Gray Bull zone to the upper part of the Lysite zone.[7] An amphilemurid.
Parapternodus P. antiquus Lower part of the formation.[7] YPM 31169, fragment of left ramus with M2-3.[7] An apternodontid.
Plagioctenodon P. krausae Sand Creek Facies.[7] A nyctitheriid.
cf. P. krausae Locality SC-29, Park County, Wyoming.[8] An isolated first or second lower incisor and the buccal half of an upper molar.[8] A nyctitheriid.
P. savagei YPM locality 104, lower part of the formation.[7] "YPM 34257, right P3-M2".[7] A nyctitheriid.
Pontifactor P. sp. "UW 8584, 9621, 9649, 9681, 9683, 9710, 9721, 9732, 9733, 10449, 10455, 10456".[7] A nyctitheriid.
Scenopagus S. hewettensis UW locality V -73020.[7] UW 8998 and possibly UW 9738, 10450.[7] An amphilemurid.
S. sp. Middle Gray Bull zone.[7] An amphilemurid, at least 2 species represented by inadequate material, at least one is probably new.[7]
Talpavoides T. dartoni Lower part of the formation.[7] An amphilemurid.
Wyonycteris W. chalix Locality SC-29, Park County, Wyoming.[8] "UM 76910, a right dentary".[8] A nyctitheriid, originally believed to be a bat.

Ferae

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Ferae reported from the Willwood Formation
Genus Species Presence Material Notes Images
Acarictis A. ryani Locality SC-67.[9] A broken right molar and a left molar.[9] A hyaenodont.
Alocodontulum A. atopum YRM 30790 and USGS 7208.[10] A palaeanodont.
Arfia A. junnei Localities SC-67, SC-69, SC-79, SC-121, SC-308 and SC-348.[9] A hyaenodont.
A. sp. Southern Bighorn Basin.[10] Fragmentary postcranial remains.[10] A hyaenodont.
Cf. Asiabradypus Cf. A. sp. Locality SC-67.[9] An edentulous right lower jaw (UM 87859m).[9] A palaeanodont.
Didymictis D. leptomylus Localities MP-40, SC-67 and SC-79.[9] Skull and teeth.[9] A viverravid.
D. protenus Multiple postcranial specimens.[10] A viverravid.
Dipsalidictis D. platypus Localities SC-67 and SC-141.[9] An oxyaenid.
D. transiens Localities SC-79 and SC-67.[9] An upper left canine and a trigonid of a molar.[9] An oxyaenid.
Miacis M. winkleri Localities SC-67, SC-348 and SC-350.[9] 3 fragmentary dentaries.[9] A miacid.
 
cf. M. sp. USGS 7161.[10] A miacid.
Oxyaena O. forcipata Relatively complete skeletal remains.[10] An oxyaenid.
O. gulo USGS 7186.[10] An oxyaenid.
O. intermedia Fragmentary postcrania.[10] An oxyaenid.
O. platypus [10] Now moved to the genus Dipsalidictis.
Palaeanodon P. ignavus Partial skeletons including postcrania.[10] A palaeanodont.
P. nievelti Localities SC-67 and SC-121.[9] A palaeanodont.
Palaeonictis P. occidentalis "Hind foot skeleton and associated fragments".[10] An oxyaenid.
 
P. sp. Locality SC-67.[9] Trigonid of a right molar.[9] An oxyaenid.
Prolimnocyon P. atavus Bighorn Basin.[16] Partial skeleton.[16] A hyaenodont.
P. eerius Localities SC-67 and possibly SC-139.[9] Crushed skull.[9] A hyaenodont.
Prototomus P. deimos Localities SC-67 and SC-349.[9] 4 fragmentary specimens.[9] A hyaenodont.
P. sp. 4 specimens.[10] A hyaenodont.
Tritemnodon T. sp. 2 specimens with postcrania.[10] A hyaenodont.
 
?Uintacyon ?U. sp. [10] A miacid.
Viverravus V. bowni Locality SC-67,[9] and locality SC-29, Park County, Wyoming.[8] A viverravid.
V. politus Locality SC-67.[9] A left maxilla.[9] A viverravid.
Vulpavus cf. V. canavus 3 specimens.[10] A miacid.

Leptictids

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Leptictids reported from the Willwood Formation
Genus Species Presence Material Notes Images
Palaeictops P. bicuspis Also found in the Wind River Formation.[7]
Prodiacodon P. tauricinerei Mostly in the Gray Bull zone, one or two specimens in the Bighorn Basin Lysite zone.[7]
P. sp. Middle Gray Bull zone.[7] YPM 26013, 26040, possibly 26026.[7]

Marsupials

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Marsupials reported from the Willwood Formation
Genus Species Presence Material Notes Images
Mimoperadectes M. labrus Localities SC-67 and SC-69.[9] Left dentary.[9]
 
Peradectes P. cf. P. chesteri 2 isolated teeth.[8]
 

Multituberculates

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Multituberculates reported from the Willwood Formation
Genus Species Presence Material Notes Images
Ectypodus E. powelli Locality SC-29, Park County, Wyoming.[8] 10 isolated teeth from at least 2 individuals.[8] A neoplagiaulacid.
E. tardus Locality SC-67.[9] Tooth crowns.[9] A neoplagiaulacid.

Primatomorphs

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Primatomorphs reported from the Willwood Formation
Genus Species Presence Material Notes Images
Absarokius A. abbotti [17] An omomyid.
A. metoecus [17] An omomyid.
Anemorhysis A. pattersoni Upper part of the formation.[18] An omomyid.
A. wortmani Upper part of the formation.[18] An omomyid.
Arapahovius A. advena Northwest Wyoming.[17] An omomyid.
Arctodontomys A. wilsoni Locality SC-67.[9] Small sample of teeth.[9] A microsyopid.
Bownomomys B. americana [17] An omomyid, formerly listed as a species of Teilhardina.
B. crassidens [17] An omomyid, formerly listed as a species of Teilhardina.
Cantius C. abditus A substantially complete skull and mandible.[19] An adapiform.
C. torresi Localities SC-67 and SC-69.[9] An adapiform.
Carpolestes C. cf. C. nigridens Locality SC-29, Park County, Wyoming.[8] A right dentary.[8] A carpolestid.
Chlororhysis C. incomptus Upper part of the formation.[18] An omomyid.
Micromomys M. willwoodensis Clark's Fork Basin.[20] A micromomyid.
Microsyops M. latidens Southern Bighorn Basin.[21] Over a thousand specimens.[21] A plesiadapiform.
Cf. Niptomomys Cf. N. sp. Locality SC-67.[9] An edentulous right dentary.[9] A microsyopid.
Phenacolemur P. praecox Localities SC-67 and SC-348.[9] Right and left dentaries.[9] A paramomyid.
P. willwoodensis Upper part of the formation.[22] A paramomyid.
Pseudotetonius P. ambiguus [17] An omomyid.
Steinius S. annectens Northwest Wyoming.[17] An omomyid.
S. vespertinus "AMNH 16835, fragment of a left ramus with M1 through M3".[6] An omomyid.
Strigorhysis S. sp., cf. S. bridgerensis [17] An omomyid.
Tatmanius T. szalayi Northwest Wyoming.[17] An omomyid.
Teilhardina T. americana [17] Now moved to the genus Bownomomys.
T. crassidens [17] Now moved to the genus Bownomomys.
T. tenuicula [17] An omomyid.
Tetonius T. homunculus [17] An omomyid.
T. matthewi [17] An omomyid.
T. sp. [17] An omomyid.
Tinimomys T. graybullensis The lingual half of a right upper molar.[8] A microsyopid.
Worlandia cf. W. sp. Locality SC-29, Park County, Wyoming.[8] 2 isolated teeth.[8] A plagiomenid colugo.

Rodents

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Rodents reported from the Willwood Formation
Genus Species Presence Material Notes Images
Acritoparamys Cf. A. atavus Locality SC-67.[9] A small isolated lower incisor (UM 86003m).[9]
A. atwateri Localities SC-67, SC-308 and SC-351.[9] Several dentaries and teeth.[9]
Franimys F. sp. "ACM 10524 (a skull with the right P4 and M2-M3, edentulous mandible, and several postcranial elements)".[6]
Notoparamys N. costilloi Upper part of the formation.[23] 18 specimens.[23] Also known from the Huerfano Formation. "Pseudotomus" coloradensis and Leptotomus loomisi are probably junior synonyms.[23]
Paramys P. taurus Localities SC-67, SC-139 and SC-350.[9] Jaw fragments and incisors.[9]

Ungulates

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Ungulates reported from the Willwood Formation
Genus Species Presence Material Notes Images
Anacodon A. ursidens [10] An arctocyonid.
Bunophorus cf. B. grangeri USGS 16470 (a very incomplete skeleton).[10] A dichobunid originally listed as cf. Wasatchia dorseyana.
Cardiolophus C. radinskyi UM 64913.[24] An isectolophid.
Copecion C. davisi Localities BR-2, SC-51, SC-67, SC-69, SC-79, SC-139, SC-308, SC-345, SC-348, SC-349 and SC-351.[9] A phenacodontid.
Chriacus C. badgleyi Localities SC-67, SC-79, SC-121 and SC-342.[9] An arctocyonid.
 
C. sp. Several skeletal specimens.[10] An arctocyonid.
Diacodexis D. ilicis Localities SC-67 and SC-308.[9] A dichobunid.
D. metsiacus Several specimens, including a near-complete skeleton.[10] A dichobunid.
Dissacus D. praenuntius Park County, Wyoming.[9][25] Teeth, jaw elements & bone fragments.[9][25] A mesonychid.
D. serior USGS locality D-1754, Bighorn Basin, Wyoming.[25] Left dentary fragments (USGS 27612).[25] A mesonychid.
D. willwoodensis Bighorn Basin, Wyoming.[25] Mandibles.[25] A mesonychid.
Ectocion E. osbornianus Locality SC-67 and SC-351.[9] 2 fragmentary dentaries.[9] and a single postcranial association.[10] A phenacodontid.
 
E. parvus Localities HG-3, SC-67, SC-69, SC-121, SC-139, SC-182, SC-308 and SC-351.[9] A phenacodontid.
Hapalodectes H. anthracinus University of Wyoming locality V-73086, Wyoming.[25] Teeth (USGS 9628).[25] A mesonychian
H. leptognathus A fragmentary specimen (USGS 5912).[10] A mesonychian.
Heptodon cf. H. calciculus Wind River Basin.[10] Remains of a subadult with postcrania.[10]
Homogalax H. protapirinus Bighorn Basin.[26] A skull (YPM(PU) 16168),[26] and several other specimens.[27][24] An isectolophid.
 
cf. H. protapirinus At least 2 specimens.[10] An isectolophid.
Hyopsodus H. loomisi Localities SC-67, SC-69, SC-79, SC-121, SC-308 and SC-342.[9] A hyopsodontid.
 
H. powellianus "AMNH 4147, right mandible fragment with M1 through M3".[6] A hyopsodontid.
Hyracotherium H. grangeri Locality SC-67.[9] 2 isolated teeth.[9] An equid.
H. sandrae Localities FG-61, SC-67, SC-69, SC-79, SC-121 and SC-139.[9] An equid.
H. sp. Skeletal remains with postcrania.[10] An equid.
Lambdotherium L. popoagicum Multiple localities A brontotherid.
Meniscotherium M. priscum Locality SC-67(?)[9] Left dentary fragment.[9] A phenacodontid.
 
Pachyaena P. gigantea YPM localities 131 & 149, Wyoming.[25] Jaw elements & teeth.[25] A mesonychid.
 
P. gracilis USGS locality D-1640.[25] Maxillary fragments (USGS 7185).[25] A mesonychid.
P. ossifraga Locality SC-348.[9] Trigonid of a right molar.[9] A mesonychid.
P. sp. Postcranial material.[10] A mesonychid.
Phenacodus P. cf. P. intermedius Localities SC-67 and SC-141.[9] A phenacodontid.
P. primaevus Near complete skeletons.[10] A phenacodontid.
P. vortmani Near complete skeletons.[10] A phenacodontid.
Princetonia P. yalensis Locality SC-121(?)[9] Right dentary.[9] An arctocyonid.
Thryptacodon T. antiquus [10] An arctocyonid.
T. barae Localities MP-38 and SC-121.[9] An arctocyonid.
T. olseni [10] An arctocyonid.
T. sp. 2 partial skeletons.[10] An arctocyonid.
Wasatchia cf. W. dorseyana USGS 16470 (a very incomplete skeleton).[10] Now a junior synonym of Bunophorus.
Xenicohippus Lower part of the Upper Willwood Formation.[28] A hyracotheriine.

Reptiles

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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

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Birds reported from the Willwood Formation
Genus Species Presence Material Notes Images
Anachronornis A. anhimops Clark Quadrangle, Park County, Wyoming.[29] USNM 496700.[29] An anseriform.
Anseriformes Familia Incertae sedis Clark Quadrangle, Park County, Wyoming.[29] USNM 496701 (right quadrate missing the pterygoid condyle); USNM 496702 (fragmentary right femur consisting of only the proximal and distal ends).[29] Generally similar to Anachronornis & Danielsavis.[29]
Aves indet. Localities SC-67 and SC-121.[9] A cervical vertebra and proximal part of a carpometacarpus.[9] An indeterminate bird.
Calcardea C. junnei "UM 76882, anterior part of sternum, partial left coracoid. nearly complete right coracoid, partial left humerus. two nearly complete vertebrae. fragmentary left and right tarsometatarsi, and several phalanges, all probably representing a single individual bird."[8] Originally thought to be a heron, now thought to be related to Vastanavis.[30]
Diatryma D. gigantea Several specimens.[31] Now deemed a junior synonym of Gastornis.
Eogeranoides E. campivagus "Fragmentary tibiotarsus and tarsometatarsus remains".[32] A dubious geranoidid, may be a junior synonym of Paragrus prentici.
Gastornis G. gigantea Several specimens.[31] A gastornithiform.
 
Geranoides G. jepseni Elk Creek, Bighorn Basin.[32] A geranoidid, now deemed a junior synonym of Palaeophasianus meleagroides.
Microolithus M. wilsoni Partial eggs.[33] Fossil bird eggs.
Palaeophasianus "P." incompletus "A fragmentary distal end of a tarsometatarsus".[32] A very large possible geranoidid, may actually belong to the genus Paragrus or be outside Geranoididae entirely.
P. meleagroides Elk Creek, Bighorn Basin.[32] A geranoidid.
?P. sp. AMNH 5156.[32] A geranoidid.
Paracathartes P. howardae [34] A lithornithid.
Paragrus P. prentici [32] A geranoidid.
Primoptynx P. poliotauros Specimen including all major postcranial bones.[35] A large owl.
Sandcoleus S. copiosus Clark Quadrangale, Park County, Wyoming.[36] "Two articulated partial skeletons and a number of other elements".[36] A sandcoleid mousebird.

Crocodilians

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Crocodilians reported from the Willwood Formation
Genus Species Presence Material Notes Images
Allognathosuchus A. sp. Localities SC-67, SC-139, SC-342 and SC-349.[9] An alligatorid.
 
Crocodilia indet. Localities SC-67, SC-69 and SC-121.[9] Dermal scutes and vertebral centra.[9] May represent either large Allognathosuchus or small Borealosuchus.
Borealosuchus B. sp. Localities SC-67, SC-79, SC-139, SC-342, SC-345 and SC-350.[9]
Orthogenysuchus O. olseni [37] A caiman.
Boverisuchus B. sp. Locality SC-348.[9] A single tooth (UM 83817m).[9]

Squamates

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Squamates reported from the Willwood Formation
Genus Species Presence Material Notes Images
Anguidae indet. 2 fragmentary dentaries (UM 76872 and 76873).[8] A very small anguid lizard.[8]
Anguimorpha A dentary, maxilla and 1 or 2 premaxillae (UM 76874–76875, 76878-76879(?), and 768811).[8] A gerrhonotine or diploglossine.[8]
Anguimorph CG "UCMP 150871, 150872 (jaw frag-ments), 150920 (jaw fragment), 150969 (parietal fragment),151038 (left frontal), 151067 (right maxilla fragment), 151095 (right maxilla fragment), 167499 (right maxilla fragment), 167553 (left maxilla fragment)".[38]
Anniealexandria A. gansi UCMP locality V99019.[38] Skull fragments and vertebrae.[38] An amphisbaenian.
Anolbanolis A. banalis UCMP locality V99019.[38] An iguanian.
Apodosauriscus A. thermophilus UCMP locality V99019.[38] Skull fragments.[38] An anguid.
Blutwurstia B. oliviae Clarks Fork Basin.[39] A xenosaurid.
cf. Eodiploglossus cf. E. sp. CG "UCMP 150916 (right maxilla fragment), 150919 (right frontal), 150962 (partial left frontal), 151070, 151071 (skull fragments), 167338 (partial right frontal), 167426 (left maxilla fragment), 167447 (left maxilla fragment), 167456 (jaw fragment),?167527 (right pterygoid fragment), 167602 (right dentary fragment), 400180 (right maxilla fragment)".[38] An anguid.
Gaultia G. silvaticus UCMP locality V99019.[38] A glyptosaurine.
Gerrhonotinae Gerrhonotine CG Skull fragments.[38] An alligator lizard.
Glyptosaurinae Glyptosaurine CG "UCMP 151033 (right maxilla fragment), ?151068 (left pterygoid fragment), 151935 (parietal fragment), 167269 (parietal fragment),?167613 (right palatine fragment)."[38] A glyptosaurine.
Iguanidae Iguanid CG "UCMP 151078 (right dentary fragment), 400156 (partial right postorbital), 400169 (partial right squamosal)".[38] An iguanid lizard.
Lacertilia indet. Localities SC-67 and SC-308.[9] Vertebrae.[9] Indeterminate lizards.
Melanosaurus M. maximus A frontal, numerous osteoderms and vertebrae.[9] A glyptosaurine.
Palaeoxantusia P. sp. CG Skull fragments.[38] A night lizard.
Proxestops Cf. P. sp. Locality MP-40.[9] UM 88170m (2 osteoderms).[9] A glyptosaurine.
P. sp. CG Skull fragments.[38] A glyptosaurine.
Provaranosaurus cf. P. sp. CG "UCMP 167299 (right dentary fragment)".[38] A xenosaurid.
cf. Saniwa cf. S. sp. CG-1 "UCMP 150921 (jaw fragment with partial tooth), 151099 (premaxilla), 167572 (jaw fragment with tooth)".[38] A varanid.
cf. S. sp. CG-2 "UCMP 150873 (right dentary fragment with tooth), 150971 (tooth), 167324 (distal right humerus), 167336 (edentulous left dentary fragment), 167355 (parietal fragment)".[38] A varanid.
Suzanniwana S. patriciana UCMP locality V99019.[38] An iguanid.
Varanoidea A dentary and maxilla (UM 76876 and 768771).[8] One or possibly 2 species of Parasaniwa or Provaranosaurus-like varanoids.[8]
Xantusiidae Xantusiid CG "UCMP 150827 (right maxilla fragment), 150965 (maxilla fragment), 150970 (right maxilla fragment), 167413 (left frontal fragment), 167495 (right maxilla fragment), 167575 (premaxilla), 167599 (right maxilla fragment), 167600 (left maxilla fragment)".[38] A night lizard.

Testudines

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Testudines reported from the Willwood Formation
Genus Species Presence Material Notes Images
Chelonia indet. Localities SC-67, SC-121 and SC-348.[9] Several pieces of the carapace and plastron.[9] Indeterminate medium to large turtles.
Echmatemys E. sp. Locality SC-67.[9] Much of the plastron and several peripherals or pleurals from the carapace (UM 83627), and a peripheral (UM 66617m).[9]
 
Gomphochelys G. nanus Southeastern Bighorn Basin, Washakie County, Wyoming.[40] A dermatemydid.
Cf. Plastomenus Cf. P. sp. Localities SC-67 and SC-350.[9] Fragmentary pieces of the carapace and plastron.[9] A trionychid.

Amphibians

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Amphibians reported from the Willwood Formation
Genus Species Presence Material Notes Images
Anura Distal end of a humerus (UM 76883).[8] A small frog.
Urodela Numerous vertebrae, UM 76871 (a-j).[8] A small salamander.

Fish

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Fish reported from the Willwood Formation
Genus Species Presence Material Notes Images
Amia A. sp. Localities SC-67 and SC-342.[9] Isolated cervical vertebrae, and a concretion of broken bones including 1 or 2 tooth-bearing bones likely belonging to Amia. A bowfin.
 
Cuneatus C. maximus [41] A large gar.
Lepisosteus L. sp. "Mostly diamond-shaped ganoid scales, but some specimens include distinct opisthocoelous vertebrae, basioccipitals and other cranial elements."[9] A gar.
 

Invertebrates

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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.

Invertebrate ichnotaxa

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Invertebrate ichnotaxa reported from the Willwood Formation
Ichnogenus Ichnospecies Presence Material Notes Images
Camborygma C. litonomos Polecat Bench.[42] Prismatic cylindrical structures.[42] Likely represent crayfish burrows.[43][42]
Cocoon traces Polecat Bench.[44]
Cf. Cylindricum Cf. C. isp. Polecat Bench.[44] "Predominantly vertical, straight to sinuous, unbranched, unlined, and smooth walled shafts with circular cross sections and gently rounded, unenlarged terminations".[42] Burrows possibly created by beetles, hymenopterans, emerging cicada nymphs, spiders or molluscs.[42]
Edaphichnium E. lubricatum Polecat Bench.[44] "Tubular burrows with ellipsoidal fecal pellets".[45] Formed by substrate feeding by Earthworms or other invertebrates.
Naktodemasis N. bowni Bighorn Basin.[46] "Burrows composed of nested ellipsoidal packets backfilled with thin, tightly spaced, menisci subparallel to the bounding packet."[46] Burrows likely constructed by burrowing bugs or cicada nymphs.[42][46]
cf. Planolites cf. P. isp. Polecat Bench.[44] Traces made by the feeding of worm-like animals.
 
cf. Steinchnus S. isp. Polecat Bench.[44] Traces made by invertebrates, possibly beetles or mole crickets.

Gastropods

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Gastropods reported from the Willwood Formation
Genus Species Presence Material Notes Images
Cf. Albertanella Cf. A. minuta [8] A pupillid.
Discus D. ralstonensis Many individuals (some juvenile specimens).[8] An endodontid.
Elimia or Pleurocera E. or P. sp. Some 25 specimens, many are internal molds.[9] A pleurocerid.
Grangerella cf. G.(?) phenacodorum 2 specimens originally referred to Protoboysia complicata.[8] A grangerellid.
G. sinclairi [8] A grangerellid.
Cf. Gyraulus Cf. G. sp. Locality SC-69.[9] A poorly-preserved planispiral internal mold.[9] A pulmonatan.
 
Hendersonia H. evanstonensis Several specimens, none preserving the operculum.[8] A helicinid.
Holospira H. sp. Localities SC-67, SC-139, SC-345 and SC-349.[9] 7 individuals.[9] An urocoptid.
 
"Hydrobia" "H." sp. Locality SC-69.[9] "A very small, dextral, high-spired shell with 9 whorls".[9] A hydrobiid.
 
Cf. Microphysula Cf. M. sp. A single individual.[8] A sagdid.
 
Oreohelix O. megarche A single specimen (UM(I) 65404).[8] An oreohelicid.
Cf. Pupilla Cf. P. sp. UM(I) 654071.[8] A pupillid.
 

Plants

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Plants reported from the Willwood Formation
Genus Species Presence Material Notes Images
Celtis C. phenacodorum Endocarps.[9] An urticale.

Wasatchian correlations

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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 (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

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References

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  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 d e f Johnson, Edward (June 1, 2005). "A New Early Eocene Mammalian Fauna from the Great Divide Basin, Southwestern Wyoming: Vertebrate Paleontology, Paleoclimatology, and Biostratigraphy". Masters Theses.
  7. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au av aw Bown, T.; Schankler, David M. (1982). "A review of the Proteutheria and Insectivora of the Willwood Formation (Lower Eocene), Bighorn Basin, Wyoming". Geological Survey Bulletin. Vol. 1523. doi:10.3133/B1523. S2CID 127861247.
  8. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak D., Gingerich, Philip (1987). Early Eocene bats (Mammalia, Chiroptera) and other vertebrates in freshwater limestones of the Willwood Formation, Clark's Fork Basin, Wyoming. Museum of Paleontology, University of Michigan. OCLC 17313505.{{cite book}}: CS1 maint: multiple names: authors list (link)
  9. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au av aw ax ay az ba bb bc bd be bf bg bh bi bj bk bl bm bn bo bp bq br bs bt bu bv bw bx by bz ca cb cc cd ce cf cg ch ci cj ck cl cm cn co cp Gingerich, Philip D. (1989). New earliest Wasatchian mammalian fauna from the eocene of northwestern Wyoming: composition and diversity in a rarely sampled high-floodplain assemblage. University of Michigan. OCLC 1066072691.
  10. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj Rose, Kenneth D. (1990), "Postcranial skeletal remains and adaptations in early Eocene mammals from the Willwood Formation, Bighorn Basin, Wyoming", Geological Society of America Special Papers, Geological Society of America, pp. 107–134, retrieved September 5, 2022
  11. ^ Rose, Kenneth D.; Rana, Rajendra S.; Sahni, Ashok; Kumar, Kishor; Singh, Lachham; Smith, Thierry (June 2009). "First Tillodont from India: Additional Evidence for an Early Eocene Faunal Connection between Europe and India?". Acta Palaeontologica Polonica. 54 (2): 351–355. doi:10.4202/app.2008.0067. ISSN 0567-7920. S2CID 129644411.
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  13. ^ a b c Dunn, Rachel H.; Rose, Kenneth D. (July 2015). "Evolution of early Eocene Palaeosinopa (Mammalia, Pantolestidae) in the Willwood Formation of the Bighorn Basin, Wyoming". Journal of Paleontology. 89 (4): 665–694. Bibcode:2015JPal...89..665D. doi:10.1017/jpa.2015.31. ISSN 0022-3360. S2CID 131544565.
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  46. ^ a b c Smith, Jon J.; Hasiotis, Stephen T.; Kraus, Mary J.; Woody, Daniel T. (March 2008). "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. Bibcode:2008JPal...82..267S. doi:10.1666/06-023.1. ISSN 0022-3360. S2CID 130604162.

Bibliography

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