Vertebrate Paleontology of Montana

Home , 2014 in paleontology, Adapidae, Agriochoerus, Aphelops, Aptian, Aquilops

John R. Horner1 and Dale A. Hanson2

1Chapman University, Orange, California; Montana State University, Bozeman, Montana 2South Dakota School of Mines & Technology, Rapid City, South Dakota

(1) INTRODUCTION derived concerning the evolution, behavior, and paleo- Montana is renowned for its rich paleontological ecology of vertebrate fossil taxa from Montana. treasures, particularly those of vertebrate animals All Paleozoic vertebrates from Montana come such as fi shes, dinosaurs, and mammals. For exam- from marine sediments, whereas the Mesozoic as- ple, the most speciose fi sh fauna in the world comes semblages are derived from transgressive–regressive from Fergus County. The fi rst dinosaur remains noted alternating marine and freshwater deposits, and the from the western hemisphere came from an area near Cenozoic faunas are derived strictly from freshwater the mouth of the Judith River in what would become terrestrial environments. Fergus County. The fi rst Tyrannosaurus rex skeleton, (2) PALEOZOIC VERTEBRATES and many more since, have come from Garfi eld and McCone Counties. The fi rst dinosaur recognized to Two vertebrate assemblages are known from the show the relationship between dinosaurs and birds Paleozoic, one of Early Devonian age, and the other of came from Carbon County, and the fi rst dinosaur eggs, Late Mississippian age. embryos, and nests revealing dinosaur social behav- a. Early Devonian (Emsian: 407–397 Ma) iors were found in Teton County. The fi rst dinosaur Beartooth Butte Formation confi rmed to have denned in burrows was found in The oldest vertebrate remains found in Montana Beaverhead County. come from the Beartooth Butte Formation exposed Although Montana is not often thought of for in the Big Belt and Big Snowy Mountains of central mammal fossils, a great diversity of late Mesozoic Montana. These Devonian sediments, representing and Cenozoic mammals also occurs within the State. an estuarine environment at the edge of the continent Especially noteworthy are the mid to Late Cretaceous (Dorf, 1934; Sandberg, 1961), yield bony plates (fi g. primitive mammals found within the great dino- 1) of armored fi shes called arthrodires and antiarchs saur-producing formations of eastern Montana, the (see Fiorillo, 2000), which are both groups within the early and late Paleocene mammals of the Fort Union Placodermi, the “dominant vertebrates of the Devo- Formation in central and eastern Montana, and the nian Period” (Young, 2010). The Beartooth Butte late Eocene/early Oligocene deposits in southwestern Formation, yielding the best examples of these fi sh- Montana. Additionally, middle Eocene and middle es, is named for Beartooth Butte, located along the Miocene strata contain important mammal fossils, in Beartooth Highway in Wyoming, adjacent to the Mon- some cases representing unique occurrences. tana border. Twenty-one species have been described This chapter highlights Montana’s most signifi cant from the Wyoming site (Bryant, 1935; Elliot and Ilyes, vertebrate fossils, and the environments in which the 1996; Fiorillo, 2000). Although some placoderms in animals lived and died. We have chosen to list repre- other regions of North America grew to gigantic pro- sentative Holotypes, and taxa that have been formally portions, the specimens from Montana and Wyoming described in the literature, rather than listing all of represent individuals of about 20 to 30 cm in length. the species reported in “faunal lists,” since these lists Fiorillo (2000) presented data from a stable oxy- often contain very fragmentary remains, and only best gen and carbon isotope study of the various sites in guesses of their identities. The taxa listed here are Wyoming and Montana, and was able to hypothesize what we consider to be the most representative, from that the Montana sites had a higher freshwater com- which important and interesting hypotheses have been ponent as opposed to the Wyoming sites, which had 1 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics

Figure 1. Dermal armor plate from the placoderm, Cyrtaspidichthys sculptus from the Beartooth Butte Formation, Wyoming/Montana border. Photo by James St. John. higher salinity. This study helps to confi rm that these pian, Big Snowy Group (Horner, 1985). The Bear Devonian fi shes lived in both freshwater and marine Gulch Limestone was deposited in an embayment of environments (Young, 2010), and that a shallow em- the “Montana Trough” (see Williams, 1983), a narrow bayment existed in Wyoming at the time (see fi g. 2). seaway that connected the Panthalassic Ocean to the Williston Basin (fi g. 3), which at the time was located b. Late Devonian, Early Mississippian (361 Ma) Sappington Formation about 10º North latitude (Grogan and Lund, 2002). No vertebrates have been formally described from The Bear Gulch Limestone sediments consist of this unit, although fi sh remains have been reported fi ne-grained micritic muds deposited rhythmically that (Gutschick and others, 1962). now form a plattenkalk lagerstätte (Williams, 1983), preserving exquisite soft-bodied organisms and fi shes c. Late Mississippian (Serpukhovian: 330.9–323.2 (see Lund and Grogan, 2013). Evaluation of the sedi- Ma) Bear Gulch Limestone ments together with paleoclimatology models suggests Fish fossils were fi rst discovered in the Bear that the climate fl uctuated from semi-arid to tropi- Gulch Limestone of Fergus County in 1968 by Chuck cal, and that deposition within the seaway alternated Allen, a man from Beckett, Montana who was quar- between slow during arid conditions to rapid during rying building stone. The fi rst fi sh he found was a tropical seasons (Grogan and Lund, 2002). This alter- coelacanth, which he reported to the University of nating deposition is refl ected in specimen preserva- Montana, Museum of Paleontology. Bill Melton, the tion: slow depositional periods produced disarticulated curator, and his fi eld assistant, J. Horner, went to the skeletal remains scattered about on the sediment fl oor, site the following year and opened a quarry to evaluate whereas rapid deposition preserved whole bodies and the rock’s potential. In less than a week they had dis- soft tissues. covered a plethora of fi shes and soft-bodied animals, The Bear Gulch fi sh fauna is extraordinary and is all new to science. Paleozoic fi sh expert Richard Lund represented by more than 3,000 catalogued specimens from New York was brought in, and so began what (fi g. 4), representing more than 130 diff erent species, would eventually produce hundreds of new species, the majority of which are chondrichthyans (see table and the world’s most diverse Paleozoic fi sh fauna. 1), which include sharks and their kin (Horner and The Bear Gulch Limestone is a facies of the Heath Lund, 1985; Lund and others, 2012). Among the bony Formation, and therefore part of the Late Mississip- fi sh, the paleoniscoids are the most speciose of the ray-fi n fi shes (Actinopterygii), and the coelacanths are 2 Horner and Hanson: Vertebrate Paleontology

Figure 2. Paleogeographic map showing North America as it may have looked during the Early Devonian. Note the Beartooth embayment in western Montana.

3 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics

Figure 3. Paleogeographic map showing North America as it may have looked during the Late Mississippian. Note the Montana trough and Williston Basin Embayment.

4 Horner and Hanson: Vertebrate Paleontology

Figure 4. Paratarrasius hibbardi, a tarrasiiformes Actinopterygian fi sh from the Bear Gulch Limestone. J Horner photo, University of Montana specimen. among the most speciose of the lobe-fi n fi shes (Sar- (3) MESOZOIC VERTEBRATES copterygii). The marine Dinwoody Formation and the terres- The fi shes come in a wide variety of body shapes, trial Chugwater Formation, both deposited during the some deep-bodied and laterally compressed, indicative Triassic Period in Montana, have yet to yield verte- of living high in the water column (e.g., Lund, 1990, brate specimens, although fossils do occur in these 2000), and others dorso-ventrally fl attened, indicative formations in Wyoming. of being bottom dwellers (Lund and Zangerl, 1974). a. Middle Jurassic (Callovian: 166–163 Ma) The earliest known lamprey (Janvier and Lund, Sundance Formation, Hulett Member 1983) is found here, as is a spiny-fi nned fi sh called an A sliver of the Sundance Formation, deposited in acanthodian (Zidek, 1980). Some shark species clearly the Sundance Sea, is exposed in south-central Mon- reveal their sexual dimorphic morphologies, the male tana (Carbon County). The Sundance Formation, pri- Falcatus falcatus, for example, sporting a large dorsal marily exposed in Wyoming, is equivalent to the Swift spine (Lund, 1985). There is also a large stethacanthid and Rierdon Formations of the marine Ellis Group in shark named Stethacanthus altonensis that probably Montana (Parcell and Williams, 2005). To date, fi shes reached 5 ft in length, and had a large, dorsal, comb- reported from the Montana part of the Sundance For- like structure (Lund, 1974). There are specimens that mation are referable only to Hulettia americana, al- show color patterns, last meals, and reproductive strat- though these beds have yet to be extensively sampled, egies (Grogan and Lund, 1995). and other taxa are found in Wyoming (see Schaeff er The Bear Gulch Bay teemed with a diverse vari- and Patterson, 1984). ety of taxa (fi g. 5), many of which are not preserved Along the northern edge of the Sundance Sea, in in any other location on earth (e.g., Lund and Lund, tidal fl at deposits located on the Montana–Wyoming 1984; Lund and Grogan, 2004; Mickle and others, border, enigmatic footprints have been reported (Har- 2009). The Bear Gulch Limestone is arguably the most ris and Lacovara, 2010). important Paleozoic fossil-bearing unit in the world. No vertebrate remains have been described from Pennsylvanian and Permian rocks in Montana have the marine Jurassic Ellis Group. not produced any described vertebrate remains. 5 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics

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Table 1—Continued.

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Table 1—Continued. $QN\ORVDXUXVPDJQLYHQWULV%URZQ Bugenasaura garbanii* *DOWRQ Pachycephalosaurus grangeri%URZQHW6FKODLNMHU Stygimoloch spinifer *DOWRQHW6XHV Stenotholus kohleri**LIILQHWDO Sphaerotholus buchholtzae*:LOOLDPVRQHW&DUU Acheroraptor temertyorum(YDQVHWDO Belonoolithus garbani-DFNVRQHW9DUULFFKLR Avisaurus archibaldi%UHWW6XUPDQHW3DXO Neoplagiaulax burgessi$UFKLEDOG Essonodon browni6LPSVRQ Meniscoessus borealis 6LPSVRQ Ectoconodon montanensis6LPSVRQ Glasbius twitchelli$UFKLEDOG Protungulatum coombsi$UFKLEDOGHWDO &HQR]RLF9HUWHEUDWHV D 3DOHRFHQH ±0D L 3XHUFDQ (DUO\3DOHRFHQH±0D 7XOORFN LQFO%XJ&UHHNDQWKLOOVIDXQD DQG /XGORZ0HPEHUVRIWKH)RUW8QLRQ)RUPDWLRQDQG6LPSVRQ4XDUU\LQWKH%HDU )RUPDWLRQ &UD]\0WQ%DVLQ Polyodon tuberculata*UDQGHHW%HPLV Lisserpeton bairdi(VWHV Derrisemys sterea+XWFKLVRQ Plastomenoides tetanetron+XWFKLVRQ Atoposemys entopteros*+XWFKLVRQ Cimexomys hausoi$UFKLEDOG Cimexomys minor6ORDQHW9DQ9DOHQ Mesodma garfieldensis $UFKLEDOG Neoplagiaulax nelsoni6ORDQ Acheronodon garbani$UFKLEDOG Stygimys kuszmauli6ORDQHW9DQ9DOHQ Catopsalis joyneri6ORDQHW9DQ9DOHQ Catopsalis waddleae%XFNOH\ Taeniolabis lamberti6LPPRQV Peradectes minor&OHPHQV Thylacodon montanensis:LOOLDPVRQHWDO Prodiacodon crustulum1RYDFHN Procerberus formicarum6ORDQHW9DQ9DOHQ Procerberus plutonis9DQ9DOHQ Crustulus fontanus&OHPHQV Leptacodon proserpinae9DQ9DOHQ Purgatorius ceratops9DQ9DOHQHW6ORDQ Purgatorius janisae9DQ9DOHQ Purgatorius unio9DQ9DOHQHW6ORDQ Ursolestes perpetior)R[HWDO Pandemonium dis9DQ9DOHQ Protungulatum donnae6ORDQHW9DQ9DOHQ Protungulatum gorgun9DQ9DOHQ Protungulatum mckeeveri$UFKLEDOG Protungulatum sloani9DQ9DOHQ Oxyprimus erikseni9DQ9DOHQ Chriacus calenancus9DQ9DOHQ Thangorodrim thalion 9DQ9DOHQ Ragnarok engdahli$UFKLEDOG Ragnarok harbichti 9DQ9DOHQ Haplaletes andakupensis9DQ9DOHQ Mimatuta morgoth9DQ9DOHQ Tinuviel eurydice9DQ9DOHQ Eoconodon nidhoggi9DQ9DOHQ Eoconodon hutchisoni&OHPHQV

9 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics Table 1—Continued. LL 7RUUHMRQLDQ 0LGGOH3DOHRFHQH±0D /HER0HPEHURIWKH)RUW8QLRQ )RUPDWLRQ *LGOH\DQG6LOEHUOLQJ4XDUULHVRIWKH&UD]\0WQ%DVLQ%HDU )RUPDWLRQDQG0HGLFLQH5RFNVRIVRXWKHDVWHUQ0RQWDQD Polyodon tuberculata%U\DQW Ammobatrachus montanensis*LOPRUH Plastomenoides lamberti+XWFKLVRQ Ptilodus gidleyi6LPSVRQ Ectypodus russelli6LPSVRQ Mesodma pygmaea6ORDQ Ptilodus gracilis*LGOH\ Ptilodus sinclairi6LPSVRQ Ectypodus grangeri6LPSVRQ Ectypodus aphronorus6ORDQ Ectypodus szalayi6ORDQ Ectypodus silberlingi6LPSVRQ Ptilodus montanus'RXJODVVG Ptilodus douglassi6LPSVRQ Baiotomeus lamberti.UDXVH Eucosmodon sparsus6LPSVRQ Parectypodus jepseni6LPSVRQ Stilpnodon simplicidens6LPSVRQ Leptonysson basiliscus9DQ9DOHQ Prodiacodon concordiarcensis6LPSVRQ Prodiacodon furor1RYDFHN Myrmecoboides montanensis*LGOH\ Emperodon acmeodontoides 6LPSVRQ Gelastops parcus6LPSVRQ Avunculus didelphodonti9DQ9DOHQ Jepsenella praepropera6LPSVRQ Pantolambda intermedius6LPSVRQ Pantomimus leari9DQ9DOHQ Coriphagus montanus'RXJODVVG Aphronorus fraudator6LPSVRQ Palaeosinopa diluculi 6LPSVRQ Didymictis tenuis6LPSVRQ Ictidopappus mustelinus6LPSVRQ Didymictis microlestes6LPSVRQ Leptacodon ladae6LPSVRQ Mckennatherium libitum 9DQ9DOHQ Leptacodon munusculum6LPSVRQ Pronothodectes matthewi*LGOH\ Palaechthon alticuspis*LGOH\ Palaechthon minor*LGOH\ Megopterna minuta'RXJODVVG Picrodus silberlingi'RXJODVVG Paromomys depressidens*LGOH\ Paromomys farrandi&OHPHQVHW:LOVRQ Paromomys maturus*LGOH\ Elpidophorus minor6LPSVRQ Eudaemonema cuspidata6LPSVRQ Elphidotarsius florencae*LGOH\ Tricentes latidens 6LPSVRQ Spanoxyodon latrunculus 6LPSVRQ Metachriacus provocator 6LPSVRQ Metachriacus punitor6LPSVRQ Chriacus pusillus 6LPSVRQ Chriacus pugnax6LPSVRQ Prothryptacodon furens6LPSVRQ Mimotricentes angustidens6LPSVRQ Deuterogonodon montanus6LPSVRQ Neoclaenodon latidens*LGOH\ Neoclaenodon montanensis*LGOH\ Neoclaenodon silberlingi*LGOH\ Claenodon vecordensis 6LPSVRQ 10 Horner and Hanson: Vertebrate Paleontology Table 1—Continued. Litomylus dissentaneus6LPSVRQ Haplaletes disceptatrix6LPSVRQ Litaletes disjunctus6LPSVRQ Ellipsodon aquilonius 6LPSVRQ Tetraclaenodon symbolicus 6LPSVRQ

LLL 7LIIDQLDQ /DWH3DOHRFHQH±0D 7RQJXH5LYHU0HPEHURIWKH)RUW8QLRQ )RUPDWLRQWKH'RXJODVVDQG6FDUULWW4XDUULHVLQWKH%HDU)RUPDWLRQ &UD]\ 0WQ%DVLQ DQGWKH0HOYLOOH)RUPDWLRQ Ectypodus hunteri6LPSVRQ Neoplagiaulax donaldorum6FRWWHW.UDXVH Paleotomus senior9DQ9DOHQ Palaeosinopa senior6LPSVRQ Apator asaphes6LPSVRQ Deltatherium durini9DQ9DOHQ Bessoecetor thomsoni 6LPSVRQ Palaeosinopa simpsoni 9DQ9DOHQ Litolestes notissimus6LPSVRQ Plesiadapis anceps6LPSVRQ Plesiadapis praecursor*LQJHULFK Tetonius rex*LGOH\ Elpidophorus patratus 6LPSVRQ Carpodaptes hazelae6LPSVRQ Gingerichia geoteretes=DFNHWDO Gidleyina montanensis 6LPSVRQ Gidleyina silberlingi 6LPSVRQ Tetraclaenodon superior 6LPSVRQ Lithornis celetius +RXGH Lithornis plebius +RXGH

LY &ODUNIRUNLDQ /DWHVW3DOHRFHQH±0D (DJOH0LQHLQWKHXSSHU%HDU )RUPDWLRQ Protentomodon ursirivalis6LPSVRQ Leipsanolestes siegfriedti6LPSVRQ Planetetherium mirabile6LPSVRQ Carpolestes nigridens6LPSVRQ Thryptacodon pseudarctos6LPSVRQ Parapheliscus bjorni*9DQ9DOHQ

E (RFHQH ±0D L 8LQWDQ 0LGGOH(RFHQH±0D Microparamys solis'DZVRQHW&RQVWHQLXV Tarkadectes montanensis0F.HQQD Desmatotherium kayi+RXJK LL 'XFKHVQHDQ 0LGGOH(RFHQH±0D Mytonolagus ashcrafti)RVWRZLF])UHOLNHW7DEUXP Spurimus hoffmani.RUWKHW7DEUXP Metanoiamys norejkoi.RUWKHW7DEUXP Macrotarsius montanus&ODUN LLL &KDGURQLDQ /DWH(RFHQH±0D Helodermoides tuberculatus'RXJODVV Glyptosaurus montanus 'RXJODVVF Didelphidectes pumilis+RXJK Peratherium donohoei +RXJK Peratherium titanelix0DWWKHZ Ictops acutidens'RXJODVV Ictops intermedius 'RXJODVV Ictops major'RXJODVV Ictops montanus'RXJODVV Ictops tenuis 'RXJODVV Ictops thomsoni0DWWKHZ Palaeolagus brachyodon0DWWKHZ Palaeolagus temnodon'RXJODVV Ischyromys douglassi%ODFN 11 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics Table 1—Continued. Ischyromys veterior0DWWKHZ Sciurus (Prosciurus) vetustus0DWWKHZ Dakotallomys whitei.RUWK Sciurus jeffersoni'RXJODVV Pipestoneomys bisulcatus'RQRKRH Eumys minor 'RXJODVV Aulolithomys bounites%ODFN Gymnoptychus minimus0DWWKHZ Namatomys lloydi%ODFN Montanamus bjorki2VWUDQGHU Yoderimys burkei%ODFN Pseudocylindrodon medius%XUNH Pseudocylindrodon neglectus%XUNH Ardynomys occidentalis%XUNH Cylindrodon fontis'RXJODVV Dolocylindrodon rahnensis.RUWKHW7DEUXP Dolocylindrodon vukae.RUWKHW7DEUXP Xenotherium unicum'RXJODVV Hyaenodon minutus 'RXJODVV Bunaelurus infelix 0DWWKHZ Cynodictis paterculus 0DWWKHZ Parictis (Subparictis) montanus&ODUNHW*XHQVEXUJ Centetodon kuenzii/LOOHJUDYHQHW7DEUXP Micropternodus borealis0DWWKHZ Kentrogomphios strophensis:KLWH Cryptoryctes kayi5HHG Apternodus baladontus$VKHUHWDO Apternodus mediaevus0DWWKHZ Domnina thompsoni6LPSVRQ Stibarus montanus0DWWKHZ Agriochoerus maximus'RXJODVV Agriochoerus minimus'RXJODVV Bathygenys alpha'RXJODVV Limnenetes anceps'RXJODVV Limnenetes platyceps'RXJODVV Montanatylopus matthewi3URWKHUR Leptotragulus profectus0DWWKHZ Trigenicus socialis 'RXJODVV Pipestoneia douglassi7DEUXPHW0HWDLV Mesohippus latidens'RXJODVV Mesohippus montanensis 2VERUQ Mesohippus portentus 'RXJODVVE Triplopides rieli5DGLQVN\

F 2OLJRFHQH ±0D L 2UHOODQ (DUO\2OLJRFHQH±0D Pseudallomys nexodens.RUWK Brachygaulus leistneri.RUWKHW7DEUXP Brachygaulus nicholsi.RUWKHW7DEUXP Brachygaulus xerobothrus.RUWKHW7DEUXP Eumys cricetodontoides:KLWH Eumys latidens :KLWH Eumys spokanensis :KLWH Scottimus longiquus.RUWK Paradjidaumo spokanensis:KLWH Heliscomys gregoryi :RRG Hyaenodon montanus'RXJODVV Oreodon robustum 'RXJODVV Eucrotaphus helenae 'RXJODVV Oreodon macrorhinus 'RXJODVV Schizotheroides parvus+RXJK Anchitherium agreste/HLG\ Hyrachyus priscus 'RXJODVV Colodon cingulatus'RXJODVV 12 Horner and Hanson: Vertebrate Paleontology Table 1—Continued. LL $ULNDUHHDQ (DUO\2OLJRFHQHWR(DUO\0LRFHQH±0D Testudo copei.RHUQHU Megalagus dawsoni%ODFNE Niglarodon blacki5HQVEHUJHU Niglarodon koerneri%ODFNE Niglarodon loneyi5HQVEHUJHU Niglarodon progressus5HQVEHUJHU Eutypomys montanensis:RRGHW.RQL]HVNL Eumys eliensis%ODFNE Gregorymys montanensis+LEEDUGHW.HHQPRQ Mesocyon drummondanus 'RXJODVV Cynodesmus thooides6FRWW Stenoechinus tantalus5LFKHW5DVPXVVHQ Proscalops intermedius%DUQRVN\ Kukusepasutanka schultzi0DFGRQDOG Arretotherium acridens'RXJODVV Cyclopidius loganensis .RHUQHU Promerycochoerus grandis'RXJODVVD Promerycochoerus hatcheri 'RXJODVVD Promerycochoerus hollandi 'RXJODVVD Promerycochoerus minor 'RXJODVV Mesoreodon chelonyx6FRWW Mesoreodon danai .RHUQHU Mesoreodon intermedius 6FRWW Mesoreodon latidens 'RXJODVVD Mesoreodon longiceps'RXJODVVE Eucrotaphus montanus 'RXJODVVD Mesoreodon wheeleri .RHUQHU Eporeodon meagherensis .RHUQHU Ticholeptus bannackensis'RXJODVVD Ticholeptus brachymelis 'RXJODVVE Ticholeptus breviceps'RXJODVVD Leptomeryx transmontanus'RXJODVV Pronodens silberlingi.RHUQHU

G 0LRFHQH ±0D L +HPLQJIRUGLDQ (DUO\0LRFHQH±0D Sciurus angusticeps0DWWKHZHW0RRN Steneofiber hesperus'RXJODVV Paciculus montanus%ODFNE Dikkomys woodi%ODFNE Mookomys altifluminis:RRG Brachyerix macrotis0DWWKHZHW0RRN LL %DUVWRYLDQ 0LGGOH0LRFHQH±P\D Ogmophis arenarum'RXJODVV Ansomys hepburnensis+RSNLQV Trilaccogaulus bettae6XWWRQHW.RUWK Mylagaulus pristinus'RXJODVV Mylagaulus proximus 'RXJODVV Sciurus angusticeps0DWWKHZHW0RRN Palaearctomys macrorhinus 'RXJODVV Palaearctomys montanus'RXJODVV Sciurus arctomyoides'RXJODVV Spermophilus (Otospermophilus) jerae6XWWRQHW.RUWK Steneofiber montanus6FRWW Steneofiber complexus 'RXJODVV Steneofiber hesperus'RXJODVV Euroxenomys inconnexus6XWWRQHW.RUWK Paciculus montanus%ODFNE Cotimus alicae%ODFND Copemys lindsayi6XWWRQHW.RUWK Dikkomys woodi%ODFNE Peridiomys halis6XWWRQHW.RUWK Mookomys thrinax6XWWRQHW.RUWK 13 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics

Table 1—Continued. Perognathoides madisonensis'RUU Perognathus ancenensis6XWWRQHW.RUWK ?Canis anceps 6FRWW Aelurodon brachygnathus'RXJODVV Aelurodon montanensis:DQJHWDO Dinocyon ossifragus'RXJODVV Mustela minor 'RXJODVV Martes kinseyi*LGOH\ Hypsoparia bozemanensis 'RUU Parvericius montanus.RHUQHU Brachyerix macrotis0DWWKHZHW0RRN Mesoscalops montanensis%DUQRVN\ Talpa? platybrachys'RXJODVV Ancenycteris rasmusseni6XWWRQHW*HQRZD\V Hesperhys vagrans'RXJODVV Cyclopidius incisivus 6FRWW Cyclopidius quadratus .RHUQHU Promerycochoerus grinnelli .RHUQHU Promerycochoerus thorpei .RHUQHU Merycoides cursor'RXJODVVD Merycochoerus compressidens'RXJODVV Merychyus smithi'RXJODVV Poatrephes paludicola 'RXJODVV Merycochoerus altiramus'RXJODVV Merycochoerus elrodi'RXJODVV Merycochoerus laticeps'RXJODVV Merycochoerus madisonius'RXJODVV Procamelus lacustris 'RXJODVV Procamelus elrodi'RXJODVVH Procamelus madisonius 'RXJODVV Protolabis montanus'RXJODVV Gomphotherium serus'RXJODVV Cosoryx agilis 'RXJODVV Blastomeryx antilopinus6FRWW Blastomeryx borealis&RSH Cranioceras kinseyi )ULFN Palaeomeryx americanus'RXJODVV Palaeomeryx madisonius 'RXJODVV Achitherium VLF minimus'RXJODVV Anchitherium equinum6FRWW Desmatippus crenidens6FRWW Altippus taxus'RXJODVVE Merychippus missouriensis'RXJODVVE Aphelops ceratorhinus 'RXJODVV Aphelops montanus 'RXJODVVD 6SHFLHVFKDOOHQJHGRUQRORQJHUFRQVLGHUHGYDOLG Note.3OHDVHVHH6PLWKDQGRWKHUVYROXPHIRU4XDWHUQDU\YHUWHEUDWHIRVVLOV

14 Horner and Hanson: Vertebrate Paleontology

Figure 5. Depiction of the marine environment preserved in the Bear Gulch Limestone. The large shark is Stethacanthus altonensis, and a pair of Falcatus falcatus swim above it. Art by Kari Scannella, with permission.

15 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics

Figure 6. Paleogeographic map showing North America as it may have looked during the Late Jurassic. Note the embayment reaches northern Montana and the Williston Basin. b. Late Jurassic (Tithonian–Kimmerigian: 156–146 regressing distal coastal plain (Cooley and Schmitt, Ma) Morrison Formation 1998). At this time the seaway was regressing to the The Morrison Formation of Montana is described north and west of southern Montana (fi g. 6). Outcrops as an anastomosed fl uvial system deposited on a of the Morrison Formation are sparse in Montana, 16 Horner and Hanson: Vertebrate Paleontology mostly exposed around the peripheries of mountain Most of the Morrison vertebrate fossils are found ranges, and most often covered by vegetation. as associated skeletons, often with skulls, in the The Morrison Formation in Montana has produced anastomosing channel deposits, but the Mother’s Day a signifi cant collection of dinosaur remains, but only Site, located in Carbon County, is a bonebed primarily one holotype, a sauropod named Suuassea emilieae composed of disarticulated elements in a muddy silt- Harris et Dodson, 2004. Suuassea has most recently stone. Multiple individuals of diplodocid dinosaurs are been confi rmed as a member of the sauropod family represented (Myers and Storrs, 2007), possibly reveal- Dicraeosauridae (Tschopp and others, 2015). Besides ing aggregate, behavioral characteristics. Suuassea, other sauropods described from Montana c. Early Cretaceous (Aptian–Albian: 120–110 Ma) include Camarasaurus (Woodruff and Foster, 2017), Kootenai Formation Diplodocus (Woodruff and others, 2018; fi g. 7), and Disconformably overlying the Morrison Formation Amphicoelias (Wilson and Smith, 1996). The stego- in Montana is the Kootenai Formation in the western saurid Hesperosaurus mjosi has also been recently parts of the State, and the Cloverly Formation in the described from Park County (Maidment and others, central and south-central parts. The Kootenai was 2018). Unfortunately, the stratigraphic relationships deposited in the Cordilleran foreland basin, and con- of the various localities in Montana have not been sists primarily of sediments deposited in fl uvial and established, nor have their relationships with other fl uvio-lacustrine environments (DeCelles, 1986; fi g. localities in the west (Turner and Peterson, 1999). The 8). One vertebrate, Toxolophosaurus cloudi, a sphe- non-dinosaurian vertebrate fauna has also not yet been nodontid lizard-like reptile, has been described from described. the Kootenai Formation in Silver Bow County (Olson, 1960). d. Early Cretaceous (Aptian–Albian: 120– 110 Ma) Cloverly Formation The Cloverly Formation has been inter- preted as a facies of the Kootenai Formation in south-central Montana, and consists primarily of braided stream deposits (Moberly, 1960). The Cloverly Formation, exposed best in Carbon and Wheatland Counties, produces an extensive vertebrate fauna that Oreska and colleagues (2013) describe as including a variety of fi shes of both osteichthyes and chondrichthyes, amphibians, squamates, testudines, crocodilians, dinosaurs, and mammals (table 1). The dinosaurs, which dominate the fauna, were described initially by Ostrom (1969, 1970), and include the theropod Deinonychus antirrhopus, the coelurosaurian dinosaur that Ostrom (1969) highlighted in his study on the origin of birds (Ostrom, 1976). The Cloverly Formation of Montana has also produced an articulated specimen of the plant-eating dinosaur Tenontosaurus tilletti (fi g. 9) thought to have been brought down by a group of Deinonychus (Maxwell and Ostrom, 1995), and off ering the best evidence to date that dromaeosaurs might have been “pack hunters.” The Cloverly of Montana is also the

Figure 7. Diplodocid (sauropod) bones from the Morrison Formation of Park unit from which the best-known North Amer- County. Museum of the Rockies photo, with permission. ican, Lower Cretaceous ceratopsian, Aquilops 17 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics

Figure 8. Paleogeographic map showing North America as it may have looked during the Early Cretaceous. The western prong embayment extending into Montana was lake-like.

18 Horner and Hanson: Vertebrate Paleontology

Figure 9. The skull of Tenontosaurus tilletti from the Cloverly Formation of Carbon County. Museum of the Rockies photo, with permission.

americanus, is found (Farke and others, 2014), pro- 2011). Lash describes a fossil zone at the bottom of viding the earliest evidence of dinosaur migrations the upper Thermopolis Member, a unit described by between Asia and North America. Dinosaurian egg Porter and others (1993) as the Muddy Sandstone. remains and neonate bones are not uncommon in the Within the fossil zone Lash reported disarticulated Cloverly (Maxwell and Horner, 1994), and suggest the remains of fi shes (Osteichthyes and Chondrichthyes), paleolandscape was conducive for nesting. testudines, plesiosaurs, and crocodilians, including Rare, triconodont mammals are also described an articulated marine crocodile (Lash, 2011). The from the Montana beds (Jenkins and Schaff , 1988; sole described Holotype from the Montana part of the Cifelli and others, 1998; Cifelli, 1999; table 1). Gobi- Thermopolis Formation is a polycotylid plesiosaur conodon ostromi (Jenkins and Schaff , 1988) is repre- named Edgarosaurus muddi found in Carbon County sented by nearly complete skeletons, a rarity for this (Druckenmiller, 2002). time period, and signifi cantly, Montanalestes keebler- f. Late Cretaceous (Cenomanian: 95 Ma) orum (Cifelli, 1999) is currently the earliest eutherian Blackleaf Formation mammal known from North America. Overlying the Kootenai Formation in central and e. Middle Cretaceous (Albian–Cenomanian: 103–98 southwestern Montana is the Blackleaf Formation, Ma) Thermopolis Shale of the Colorado Group which yields few vertebrate remains from its central Porter and others (1993) and Lash (2011) state that locations, but a unique dinosaur from localities in the the Thermopolis Shale or Formation overlies the Koo- southwestern part of the State (Beaverhead County), tenai Formation in south-central Montana, although very near the Idaho border. Oryctodromeus cubicu- this is also the area where the Cloverly Formation was laris, a “hypsilophodontid” dinosaur, was discovered recognized and described (see Moberly, 1960; Ostrom, to have nested in underground dens (Varricchio and 1970). Regardless, the Thermopolis Formation is others, 2007). This is the fi rst dinosaur confi rmed to represented primarily by marine black shale laid down have burrowed. A life restoration of Orytodromeus and along the western edge of the Western Interior Seaway its young in a burrow is on display in the Hall of Gi- (in Montana and Wyoming; fi g. 10) that extended from ants at the Museum of the Rockies in Bozeman. Other the Gulf of Mexico to the Arctic Ocean. The Thermop- described taxa from this formation include a couple olis Formation is overlain by the Mowry Shale (Lash, crocodilians, including Bernissartia, the cryptodiran 19 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics

Figure 10. Paleogeographic map showing North America as it may have looked during the Middle Cretaceous, and the deposition of the marine Colorado Group.

20 Horner and Hanson: Vertebrate Paleontology turtle Glyptops, and two neopterygian fi shes (Ullmann of the terrestrial St. Mary River Formation proximal to and others, 2012). These animals apparently lived the cordillera, and the Hell Creek Formation distally. within an intermontane basin. The Two Medicine Formation is exposed along the g. Late Cretaceous (Campanian: 80–74 Ma) Two Rocky Mountain Front in Glacier, Pondera, Teton, and Medicine Formation Lewis and Clark Counties. It is a 650-m-thick wedge During the Late Cretaceous, the Western Interior of terrestrial sandstones and mudrocks deposited on Seaway underwent a series of three regressive–trans- the western side of the foredeep. The formation is gressive pulses that are recorded in foredeep, clastic divisible into three lithofacies with distinct faunal ele- wedge sediments exposed along the eastern front of ments (see Lorenz and Gavin, 1984; Horner, 1989). the cordillera (fi g. 11). The fi rst regressive terrestri- i. The lower lithofacies (top of the lower lithofa- al sequence, following the recession of the marine cies, see fi g. 8), dated from ~79 to 80 Ma (Rogers and Colorado transgressive pulse, deposited sediments of others, 1993) and best exposed in Teton and Pondera the lower Two Medicine Formation proximal to the Counties, yields a group of dinosaur taxa that reveal cordillera, and the Eagle Sandstone more distally. A ancestral relationships with more derived taxa from second transgressive pulse deposited marine shale of younger sediments. Lower lithofacies dinosaur taxa the Claggett Formation, which separates the under- include the protoceratopsian Cerasinops and the had- lying Eagle Sandstone from the overlying terrestrial rosaurids Avicristatus and Gryposaurus latidens (table Judith River Formation. Proximal to the Judith River 1; Chinnery and Horner, 2007; Gates and others, 2011; Formation is the middle lithofacies of the Two Medi- Horner, 1992). There is also an undescribed species cine Formation. Overlying the Judith River Formation of Daspletosaurus from this horizon that provided and the eastern limit of the Two Medicine Formation information about the digestive tract of tyrannosaurid is the Bearpaw Formation, which represents the third dinosaurs (Varricchio, 2001), and a provisionally de- pulse of the seaway. The fi nal regression of the Bear- scribed ceratopsian (Baker and others, 2011). No other paw sea from Montana was followed by the deposition taxa have been described.

Figure 11. Diagram showing the facies relationships of the Late Cretaceous transgressive-regressive clastic wedge east of the cordillera. 21 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics ii. The middle lithofacies dated from ~78–79 Ma and are attributed to Troodon (Varricchio and others, and exposed in Teton and Pondera Counties, yields 2002). Bambiraptor, a small saurornitholestine thero- three dinosaur taxa including the “hypsilophodontid” pod, is also found at this stratigraphic level (Burn- Orodromeus (Horner and Weishampel, 1988), the had- ham and others, 2000). In addition to the dinosaurs, rosaurid Maiasaura (Horner and Makela, 1979; fi g. the mammals Alphadon and Cimexomys, and a new 12), and the troodontid Troodon (see Varricchio and iguanomorph lizard Magnuviator ovimonsensis, have others, 2002). The site that produced the fi rst skeletons also been described from the Willow Creek Anticline of these taxa is the Willow Creek Anticline in Teton sediments (Montellano, 1988; Montellano and others, County. The 50-m-thick stratigraphic section exposed 2000; DeMar and others, 2017). in the anticline consists of braided and anastomosing iii. The upper lithofacies (76.5 to 74.5 Ma) is best stream deposits, mudrocks containing caliche nodules, exposed in Glacier County and yields a very diverse and lacustrine limestones (Lorenz and Gavin, 1984). vertebrate fauna, some species apparently indistin- The mudrock horizons yield associations of nests guishable from taxa found in the Dinosaur Park For- referable to Maiasaura, providing clues to dinosaur mation of Alberta, and other species new and possibly behavior, including parental care and feeding, colo- transitional between Campanian and Maastrichtian nial nesting, site fi delity, nest construction, and social taxa (e.g., Horner and others, 1992; Arbour and Cur- aggregation, among others (Horner and Makela, 1979; rie, 2013; Carr and others, 2017). This upper horizon Horner, 1982; Schmitt and others, 2014). The lacus- of the Two Medicine Formation was initially collected trine sediments have produced an azdarchid pterodac- by Barnum Brown of the American Museum in New tyloid (Padian, 1984). Maiasaura is arguably the most York, around the turn of the 20th century, and a bit lat- comprehensively known dinosaur (see Woodward and er by Charles Gilmore of the Smithsonian Institution. others, 2015) because of the associations of its skel- Both early collectors made signifi cant collections, etons, ranging from embryos to full-grown adults, its but only Gilmore described new taxa (see Gilmore, eggs, nests, coprolites indicating food choice (Chin, 1914). Collection eff orts by the Museum of the Rock- 2007), and footprints. Another dinosaur, Troodon ies during the 1980s produced a wide variety of new formosus, from a lacustrine horizon at the Willow taxa (table 1), including three new horned dinosaurs Creek Anticline, is also represented by a plethora of (Sampson, 1995; McDonald and Horner, 2010), and specimens, including eggs, embryos, and skeletons some “new” contested species (Horner, 1992; Prie- (Varricchio and others, 1999, 2002). The fi rst con- to-Marquez, 2010; Penkalski, 2013). One new taxon, fi rmed dinosaur embryos also came from the Willow Hypacrosaurus stebingeri, is represented by eggs, Creek Anticline (Horner and Weishampel, 1988), embryos, and a suite of diff erent growth stages, some

Figure 12.The skulls of an adult and juvenile Maiasaura peeblesorum (Montana’s State Fossil) from the middle lithofacies of the Two Medicine Formation. Museum of the Rockies photo, with permission. 22 Horner and Hanson: Vertebrate Paleontology of which are found in extensive bonebeds (Horner and gust, the month of September, and into mid-October. Currie, 1994; Varricchio and Horner, 1993). Hypacro- Cope departed on the Josephine, the last steamboat of saurus stebingeri is arguably the second most compre- the year, with hundreds of pounds of fossils. The other hensively represented dinosaur taxon. two men made their journey home by stage and rail. In summary, the lower facies of the Two Medicine More than 10 years passed before John Bell Formation yields isolated taxa that aid in more clearly Hatcher, collecting for Othniel Marsh and the Yale understanding the phylogenetic relationships of lat- Peabody Museum in New Haven, Connecticut, came er Campanian dinosaurs, whereas the middle facies to Montana to explore the Judith River Formation for yields nesting grounds and bonebed associations that vertebrate remains. Hatcher found what Marsh would provide clues to dinosaur behaviors. The upper facies describe and name Ceratops montanaus (Marsh, yields both isolated taxa, revealing relationships of 1888), based on a single orbital horn that is now con- some later taxa, and additionally yielding nesting hori- sidered a nomen dubium. The specimen was found in zons and bonebeds. what would become Blaine County. h. Late Cretaceous (Campanian: 78 Ma) Asok Sahni, collecting for the American Museum Claggett Shale in New York during the early 1970s, described a few The Claggett Shale represents a trangressive pulse new mammalian taxa as well as various vertebrate of the marine, Cretaceous intercontinental seaway. The taxa represented by teeth and small bones recovered Claggett yields isolated dinosaur remains (Fiorillo, from microsite screenings (Sahni, 1972). A more re- 1990) and has produced a single described bird, Hes- cent summary of the mammalian fauna was published perornis montana (Shufeldt, 1915). by Montellano (1992). The fi rst relatively complete dinosaur skeleton i. Late Cretaceous (Campanian: 79–74.9 Ma) from the Judith River Formation was not described Judith River Formation until 1986, with the naming of Avaceratops lammersi The Judith River Formation is equivalent to the from Wheatland County (Dodson, 1986). Following middle lithofacies of the Two Medicine Formation another hiatus of more than 20 years, a number of new (see fi g. 11), and represents the distal part of the taxa were added from Hill and Fergus Counties. Most regressive–transgressive clastic wedge (Rogers and dinosaur specimens from the Judith River Formation others, 1993). occur as isolated individuals that have been described The Judith River Formation, exposed at the mouth recently (e.g., Ryan and others, 2010, 2014; Longrich, of the Judith River in Fergus County, produced the 2013; Mallon and others, 2016; Freedman Fowler and fi rst dinosaur fossils described from North America Horner, 2015; Arbour and Evans, 2017). Dinosaur (Leidy, 1856). The specimens had been collected by nests and embryos have also been described from Hill F.V. Hayden during a geological expedition the pre- County (Horner, 1999). ceding year. The collection consisted of isolated teeth, Bonebeds, exquisitely preserved articulated skel- which formed the basis for creating several new dino- etons of Brachylophosaurus canadensis (see Prie- saur taxa that are mostly considered nomen dubium, to-Marquez, 2005) with associated skin impressions although the taxon Troodon formosus is still in use. and biomolecular preservation, have been described Following Hayden’s expedition, E.D. Cope, work- from the distal, eastern parts of the Judithian clastic ing for the Philadelphia Academy of Science, explored wedge in Phillips County (see LaRock, 2001; Murphy the Judith River Formation exposures along the Mis- and others, 2006; Schweitzer and others, 2009). This souri River in 1876. The story of Cope’s expedition is distal part of the Judith River Formation is called the iterated in a book by Charles H. Sternberg (1909), one Parkman Sandstone, which is the shore facies of the of Cope’s fi eld assistants. Sternberg noted that they regressive Claggett Sea. had met in Helena in August and proceeded to Fort j. Late Cretaceous (Campanian–Maastrichtian: Benton and the Judith River even though the newspa- 70.5 Ma) Bearpaw Formation pers had that very month told of the massacre at the Little Bighorn. Cope and his fi eld party were not de- The Bearpaw Formation, the last transgressive terred. Cope, Sternberg, and a fellow named Mr. Issac pulse of the Cretaceous Western Interior Seaway in collected dinosaur remains for the remainder of Au- Montana (fi g. 13), yields a wide variety of vertebrates, 23 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics

Figure 13. Paleogeographic map showing North America as it may have looked during the Late Cretaceous, and the deposition of the marine Bearpaw Shale.

24 Horner and Hanson: Vertebrate Paleontology but only one described mosasaur, Plioplatecarpus later testing hypotheses concerning the extinction of peckensis Cuthbertson et Holmes, 2015, and three dinosaurs. The majority of specimens from this rock dinosaurs of questionable identity, which include unit are curated in the American Museum of Natural two hadrosaurids and a nodosaurid (Horner, 1979). History in New York; the Museum of Paleontology at It is likely that this unit will produce more skeletal the University of California, Berkeley; the Museum of remains with extraordinary preservation, such as skin the Rockies at Montana State University; The Univer- and soft-tissue impressions, due to preservation of the sity of Washington Burke Museum; and the Burpee specimens in concreted limestone nodules. Museum in Rockford, Illinois (table 1). Interestingly, nearly all the vertebrate specimens were found as k. Late Cretaceous (Maastrichtian: 72–66 Ma) St. Mary River Formation isolated individuals or in microsites. Bonebeds are rare in Montana, but more common in facies farther east in The St. Mary River Formation is exposed most the Dakotas. Based on the most recent dinosaur census extensively in southwestern Alberta, but a narrow data from the formation, Triceratops is the most com- wedge is exposed along the Rocky Mountain Front in mon (fi g. 14), followed by Edmontosaurus and Tyran- Glacier and Lewis and Clark Counties. It is composed nosaurus, and then by other ornithischian taxa before of braided stream deposits and mudrocks with caliche additional saurischians (Horner and others, 2011). limestone lenses. The unit has yielded one described protoceratopsian dinosaur (Montanoceratops cer- Probably the most famous of all taxonomic inter- orhynchos), originally described as Leptoceratops actions of any taxa in the fossil record is that between cerorhynchos by Barnum Brown and Erich Schlaikjer Tyrannosaurus and Triceratops, which have a long in 1942, and later reassigned to Montanoceratops cer- history of illustrations depicting head-to head aggres- orhynchos by Charles Sternberg in 1951. The St. Mary sive confl icts. Here we avoid the argument of how T. River Formation has also yielded a few mammal taxa rex might have acquired its meal, showing them sim- (see Hunter and others, 2010). ply together in their riverine environment (fi g. 15). Because the dinosaur taxa terminate at the K-Pg l. Late Cretaceous (Maastrichtian: 66.8–66 Ma) boundary, it is the mammalian taxa that provide the Hell Creek Formation best perspectives of the transition between the Meso- The Hell Creek Formation is arguably the most zoic and Cenozoic. Two hypotheses have prevailed for comprehensively collected and studied fossil-bearing nearly 40 years: the catastrophic, asteroid hypotheses unit in Montana. Ever since Barnum Brown collect- (Alvarez and others, 1980), and a more gradual extinc- ed the fi rst Tyrannosaurus rex skeleton at the turn of tion (see Archibald, 1982; Wilson and others, 2014). the 20th century, paleontologists have been scouring The problem is yet to be resolved. the formation for fossil remains for museums and

Figure 14. The skull of a full-grown Triceratops horridus from the lower Hell Creek Formation. The skull is 3 m long. Museum of the Rockies photo, with permission. 25 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics

Figure 15. Depiction of a feathered Tyrannosaurus rex and a vividly colored Triceratops prorsus on the edge of a river during deposition of the Hell Creek Formation. Art by Kari Scannella, with permission.

(4) CENOZOIC VERTEBRATES ecology. Farther to the west, middle and late Paleo- Cenozoic sediments in Montana can be divided cene deposits in Sweetgrass County have yielded a into two large-scale sediment regimes, the central and bounty of mammalian specimens providing important eastern Montana Paleocene–early Eocene regressive insights concerning the early evolution of mammals. sediments, and the western Montana, late Eocene– “Three of the best known Paleocene mammalian lo- Pliocene intermontane basin sediments. calities in North America—Silberling Quarry, Gidley Quarry, and Scarritt Quarry—lie on the eastern fl ank a. Paleocene (66–55 Ma) of the Crazy Mountains in south-central Montana” The early Paleocene sediments of the Fort Union (Gingerich and others, 1983). These localities, togeth- Formation in eastern Montana were deposited contem- er with those in eastern Montana and another locality poraneously with a change in base level apparently near Bear Creek in Carbon County, have long been the coinciding with the advancing Cannonball Sea to the focus of research exploring the evolution and relation- east. This resulted in swamp or fen-like environments ships of our modern groups of mammalian taxa (e.g., in the southeastern part of the State (see Brown, 1993). Simpson references; Krause and Gingerich, 1983; These swamp environments are now the massive coal O’Leary and others, 2013; see table 1). Paleognathus deposits in Big Horn, Richland, and Rosebud Coun- birds have also been reported from Crazy Mountain ties. In Garfi eld and McCone Counties, the coal lenses Basin Paleocene sediments in the Bangtail Hills near are much thinner and are replaced by braided stream Bozeman (see Houde, 1988). and anastomosed river deposits. Important primitive b. Eocene (55.0–33.7 Ma) mammal fossils from the early Paleocene sediments above the K-Pg boundary are the focus of many stud- Only a few early Eocene fossils have been found ies focused on faunal replacement and post extinction in Montana, in the Wasatch Formation outcrops of southeastern Montana, from the early Wasatchian 26 Horner and Hanson: Vertebrate Paleontology North American Land Mammal Age (NALMA) at States. The late Oligocene (early to middle Arikareean about 54 Ma, but none have been described. More NALMA) is, however, well represented in Montana records exist for middle Eocene fossils, albeit still primarily by three nearly contemporaneous areas: relatively uncommon, from the southwestern part of the Cabbage Patch deposits near Drummond, Granite the State in the Sage Creek basin southeast of Dillon, County; the outcrops adjacent to Canyon Ferry Reser- in Beaverhead County (Hough, 1955; Fostowicz-Fre- voir, Broadwater, and Lewis and Clark Counties; and lik and Tabrum, 2009; Korth and Tabrum, 2017). regions near White Sulphur Springs, Meagher County. Although this area contains probably the most tempo- Additional Oligocene deposits are found in the high rally extensive suite of Cenozoic fossils known from buttes in Carter County in southeastern Montana, but any area of Montana (Tabrum, 2001), it is important these are limited in exposure. The Cabbage Patch principally because it provides the only Montana deposits consist of numerous small outcrops, often localities containing mid-Eocene fossils, primarily isolated from one another and challenging to correlate from the Bridgerian and Uintan North American Land at the local level. These deposits have produced fossil Mammal Ages (NALMAs) at about 52 to 40 million leaves and other plant material, freshwater molluscs, years ago (mya), with a few records of Duchesnean fi sh, amphibian, turtle, bird, and mammal fossils and early Chadronian NALMA localities spanning 40 (Calede and Rasmussen, 2015). Showing a long col- to 35 mya. The fi rst of these mid-Eocene fossils was lecting history, the fi rst record of these deposits was collected by Earl Douglass in 1897, which he report- published in 1903 by Earl Douglass on three mammal ed on a few years later (Douglass, 1903). His report specimens, and Jonathan Calede recently completed spurred collecting expeditions to the area through his Ph.D. dissertation on the paleontology of these de- subsequent years, including A.E. Wood of Columbia posits, in which he noted that as many as 30 new spe- University and Amherst College, J.L. Kay and Alan cies remain to be described from the Cabbage Patch Tabrum of the Carnegie Museum, and Jean Hough of beds (Calede, 2016). The Canyon Ferry outcrops have the U.S. Geological Survey. also produced a variety of fossils of similar diversity, The intermontane basins of southwestern Mon- including insects, bird feathers, leaves, petrifi ed wood, tana are especially well known for the late Eocene and mammals (CoBabe and others, 2012; White, 1954; (middle to late Chadronian NALMA) and earliest Douglass, 1907a; Hanson, 2015), although these are Oligocene (Orellan NALMA) fossils found there, found in disparate localities. One research quarry has spanning a time frame from about 34 to 33 Ma. Lo- produced a number of mostly intact Arikareean mam- calities such as Pipestone Springs, Little Pipestone, mal skulls, including 13 examples of one species of a Thompson Creek, and Easter Lily in Jeff erson County large oreodont Megoreodon grandis (a pig/sheep-like are frequently cited in publications (e.g., Douglass, animal; fi g. 16), a beaver, a sabertooth, several ro- 1901, 1905; Matthew, 1903; Black, 1965; Kuenzi and dent taxa, and other signifi cant fi nds. Another nearby Fields, 1971; Nichols, 2001; Korth and Tabrum, 2016) locality contains numerous trackways of a large bird, discussing this time interval, and have produced an probably a heron-like wader, and several specimens of extensive variety of holotypes (table 1). Signifi cant two species of small marsupials, rare in other Montana from the paleontological standpoint, these localities, as deposits. Earl Douglass’ primary Canyon Ferry Lake well as many others of similar age in Montana, have area locality has produced several additional examples produced abundant small mammals such as rodents, of the same large oreodont, as well as other mammals lagomorphs, and artiodactyls, and small and medium of the same age. Hanson (2015) and Hanson and Scan- sized perissodactyls. This is in contrast to many local- nella (2016) prepared brief reports on the Canyon Fer- ities elsewhere that are dominated by large mammal ry faunas and geology. The fossiliferous outcrops near remains. White Sulphur Springs have, at present, not been studied in a comprehensive manner, but many important c. Oligocene (33.7–23.8 Ma) specimens have been reported historically, beginning Very few fossil localities are known in Montana in 1893 by William Berryman Scott (Scott, 1893). For between the early Oligocene Orellan NALMA at about many years, the long time span that the White Sulphur 33 Ma and the late Oligocene Arikareean NALMA Springs outcrops represent was not fully recognized, at about 30 Ma, presenting diffi culties for biostrati- leading to some reports lumping together fossils span- graphic correlations here and elsewhere in the United ning a time period of about 16 million years. The main 27 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics

Figure 16. The skull of Megoreodon grandis (dorsal view) from the Canyon Ferry mammal Quarry, early Arikareean (Oligocene). Muse- um of the Rockies photo, with permission. collecting level, historically termed the Deep River Paradise Valley in Park County, where several re- beds in the literature, has produced the majority of the searchers have studied the fossils and sediments (Bur- published specimens, but this level is actually middle bank and Barnosky, 1990; Barnosky and LaBar, 1989), Miocene in age. The lower, more restricted level is and the high bluff s to the east of the Madison River in often termed the Fort Logan beds. These lower beds Gallatin County, where Earl Douglass collected many appear to be nearly contemporaneous with the Cab- fossils in his early years of collecting. bage Patch and Canyon Ferry localities (Scott, 1893; The Flint Creek beds are another area of Barsto- Koerner, 1940; Black 1961b). vian sediments in Granite County (Douglass, 1903; d. Miocene (23.8–5.3 Ma) Black, 1961a; Barnosky and others, 2007), and as noted above, the Deep River beds near White Sulphur A signifi cant hiatus exists between these late Oli- Springs have produced many important fossils from gocene localities and the middle Miocene in Montana this time range. The Deep River beds produced some and elsewhere, which lasted in Montana from about of the early major collections from the middle Mio- 17.3 to 16.7 Ma (Barnosky and others, 2007), before cene, and helped to shape the early understanding of deposition resumed on a broad basis during the latest this period (see Scott, 1893; Koerner, 1940; Black, Hemingfordian into the early Barstovian NALMA. 1961b; Barnosky, 1981, 1982; Rensberger, 1981). Barstovian-aged sediments are scattered throughout Today, the Miocene is best known from Nebraska and southwestern Montana, often located in more rolling California, but the Montana formations, in some cases, terrain. Very few natural exposures of these sediments contain taxa that are unknown from other locations, occur, so some signifi cant localities are found in indicating a unique environment was probably present highway road cuts, such as the Anceney locality (Dorr, in this area during this time. 1956; Sutton and Korth, 1995) that produced the skull of the bear dog tentatively identifi ed as Protepicyon Since the late Barstovian, after about 13 Ma, depo- raki (fi g. 17; and Wang and others, 1999) and a bat sition of fossiliferous sediments throughout Montana Ancenycteris rasmusseni (Sutton and Genoways, has been sporadic, infl uenced mainly by modern river 1974), and a roadcut on Interstate 90 that produced the course development and glaciation. Late Barstovian-, Holotype and only known specimen of a robust canid Clarendonian-, and Hemphillian-aged deposits (13 to Aelurodon montanensis (Wang and others, 2004). The 5 Ma) are known or suggested, but these are relatively few exceptions include extensive natural exposures isolated and contain sparse fossils, and are diffi cult to of Barstovian-aged sediments in large outcrops of the age precisely. Many of the recovered fossils have rela- Hepburn’s Mesa Formation in the southern part of the tively long time ranges, adding to the challenge. 28 Horner and Hanson: Vertebrate Paleontology

Figure 17. The skull of Protepicyon raki from the Anceney locality, Barstovian (Miocene). Museum of the Rockies photo, with permission.

e. Pliocene–Pleistocene (5.3–0.02 Ma) exposures, many of these areas represent paleoenvi- Notable deposits near Deer Lodge (Powell Coun- ronments of low relief and corresponding extensive, ty) and Logan (Gallatin County) have produced monotonous landscapes of interior areas. The paleoto- Pliocene or early Pleistocene animals, including pography of Oregon and California deposits are more Gomphotherium, an early elephantid typically found similar to Montana’s, but these areas are much closer in deposits of Hemphillian age or younger. Typical to the Pacifi c Ocean, and were probably even closer Pleistocene faunas have been found in many river in those earlier periods. The Montana fossil record, sediments, including commercial gravel operations, therefore, represents a sampling of a unique region throughout Montana. Doeden’s gravel operations near of mountain ranges and valleys with probably a more Miles City (Custer County) have produced a large fau- varied seasonal climate, throughout the Cenozoic. na of early to mid-Pleistocene remains (Wilson, 2003), The scientifi c literature discussing vertebrate and isolated finds of fairly complete mammoths have fossil specimens from Montana began with the ear- been found in a few places. Some cave deposits have ly descriptions of fragmentary dinosaur remains and also produced Pleistocene remains. See Smith and isolated teeth by Joseph Leidy and Edwin Drinker others (2020) for more complete information about Cope, all collected along the Missouri River in what Quaternary vertebrate fossils. is now Fergus County. William Berryman Scott re- An important consideration for the Montana ported on some fossil mammals from Deep Creek, Cenozoic deposits is their geographic and topograph- near Fort Logan in Meager County in 1893. But the ic relationships with other similarly aged deposits in true beginnings of paleontological publishing really North America. Fossiliferous late Eocene deposits oc- began with Earl Douglass in 1902. Douglass moved cur in South Dakota, Nebraska, California, Wyoming, to Montana to teach school in a one-room school- Utah, and the Gulf Coast. Oligocene deposits occur in house on the Madison River in 1894. During his free South Dakota, Nebraska, Oregon, and New Mexico. time, he wandered the hillsides near the school. On Miocene fossils are best known from Nebraska, South these walks, he began fi nding fossil mammals, and a Dakota, California, and Oregon. Although deposits of lifelong ambition was born. He reported his fi nds and these similar ages occur in other areas in North Amer- was encouraged to continue his searches. Although ica, often with more extensive vertical and lateral lacking a geologic or paleontologic background, he

29 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics read numerous books and became self-educated on southeastern Montana hold promise to produce signif- a par with his peers. He enrolled at the University of icant fi nds, as previous studies have suggested. Mon- Montana, and in 1900 received what is reportedly the tana is ideally suited to contribute important research fi rst ever Masters degree awarded by the University. on the eff ects of mountain valley paleoenvironments During that period of time he discovered and collected on mammal development and adaptation. There are so the fi rst dinosaur skeletons found in Montana. They many more fossil vertebrate discoveries to be made in were collected from the Bearpaw Shale in Wheatland Montana. and northern Stillwater Counties (see Horner, 1979). ACKNOWLEDGMENTS Marcus Farr, a paleontologist at Princeton University, hired Douglass to collect for him in 1900 and 1901, We thank David Krause (Denver Museum of Na- but in 1902, Douglass began to collect for the Carne- ture) for help with the Paleocene taxa, Mark Goodwin gie Museum full-time in southwest Montana, as well (U.C. Berkeley) for help with the types residing in the as in North Dakota, Minnesota, Idaho, and eventually Museum of Paleontology, Dick Lund for help with the Utah. His most famous fi nd occurred in northeastern Bear Gulch Limestone taxa, and Greg Liggett (BLM) Utah in 1908, where he discovered the Carnegie Quar- for sharing his listing of Holotypes from BLM-admin- ry in the Jurassic Morrison Formation, which became istered lands in Montana and other support. We are what we now know as Dinosaur National Monument. also grateful to David Varricchio (Montana State Uni- He continued to explore in Montana for a few more versity) and Greg Wilson (University of Washington) years, before moving to Utah permanently. During his for their helpful reviews, and off er a special thanks to research on Montana paleontology, he published 12 John Metesh (Montana Bureau of Mines and Geology, papers describing mammal discoveries in the 10 years Butte) for his invitation to participate in the Centennial between 1899 and 1909. In those publications, as sole Volume, and to Susan Vuke for her editorial support. author, he erected 71 new taxa of mammals and three REFERENCES CITED lizards from Montana, of which 46 mammals and 2 lizards are still valid species today. 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