John R. Horner1 and Dale A. Hanson2
(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
7DEOH9HUWHEUDWH3DOHRQWRORJLFDO+RORW\SHVIURP0RQWDQD QRWFRPSUHKHQVLYH 3DOHR]RLF9HUWHEUDWHV D (DUO\'HYRQLDQ (PVLDQ±0D %HDUWRRWK%XWWH)RUPDWLRQ 1R0RQWDQD+RORW\SHV$QWLDUFKDQGDUWKURGLUHLQGHWHUPLQDWHWD[D VHH)LRULOOR E/DWH0LVVLVVLSSLDQ 6HUSXNKRYLDQ±0D,8*6 %HDU*XOFK/LPHVWRQH )HUJXV&RXQW\ /LVWIURP/XQGDQG*URJHQ &KRUGDWD,QFHUWDH6HGLV Typhloesus wellsi0HOWRQHW6FRWW L $JQDWKD MDZOHVVILVK Hardistiella montanensis-DQYLHUHW/XQG LL $FDQWKRGLL VSLQ\ILVK Acanthodes lundi=LGHN LLL &KRQGULFKWK\HV VKDUNV Bealbonn rogaire/XQGHW*URJDQ Gregorius rexi/XQGHW*URJDQ Srianta dawsoni/XQGHW*URJDQ Srianta srianta/XQGHW*URJDQ Debeerius ellefseni*URJDQHW/XQG Heteropetalus elegantulus/XQGE Belantsea montana/XQG Harpacanthus fimbriatus/XQGHW*URJDQ Delphyodontos dacriformes/XQG Harpagofututor volsellorhinus/XQG Echinochimaera meltoni/XQGD Echinochimaera snyderi/XQG Traquairius agkistrocephalus/XQGHW*URJDQD Traquairius spinosus/XQGHW*URJDQE Traquairius nudus /XQGHW*URJDQE Polyrhizodus digitatus /XQG Netsepoye hawesi /XQG Siksika ottae /XQG Obruchevodus griffithi*URJDQHWDO Fissodopsis robustus/XQGHWDO Petalorhynchus beargulchensis/XQG Janassa clarki/XQG Rainerichthys zangerli *URJDQHW/XQG Papilionichthys stahlae *URJDQHW/XQG Damocles serratus/XQG Falcatus falcatus/XQG Orestiacanthus fergusi/XQG Stethacanthus productus/XQG Squatinactis montanus/XQGHW=DQJHUO Thrinacoselache gracia*URJHQHW/XQG LY 2VWHLFKWK\HV ERQ\ILVK Paratarrasius hibbardi/XQGHW0HOWRQ Discoserra pectinodon/XQG Guildayichthys carnegiei/XQG Aesopichthys erinaceus3RSOLQHW/XQG Cyranorhis bergeraci/XQGHW3RSOLQ Kalops monophrys3RSOLQHW/XQG Kaplops diophrys3RSOLQHW/XQG Proceramala montanensis3RSOLQHW/XQG Wendyichthys dicksoni/XQGHW3RSOLQ Wendyichthys lautreci/XQGHW3RSOLQ Allenypterus montanus/XQGHW/XQG Caridosuctor populosum/XQGHW/XQG Hadronector donbairdi/XQGHW/XQG Polyosteorhynchus beargulchensis/XQGHW/XQG Lochmocercus aciculodontus /XQGHW/XQG Lineagruan judithi0LFNOHHWDO Lineagruan snowyi0LFNOHHWDO Beagiacus pulcherrimus0LFNOHHWDO Paphosiscus circulocaudus*URJDQHW/XQG Paphosiscus scalmocristus*URJDQHW/XQG
6 Horner and Hanson: Vertebrate Paleontology Table 1—Continued. 0HVR]RLF9HUWHEUDWHV D 0LGGOH-XUDVVLF &DOORYLDQ±0D 6XQGDQFH)RUPDWLRQ+XOHWW0HPEHU 1R0RQWDQD+RORW\SHVHulettia americana (DVWPDQ VHH6FKDHIIHUDQG 3DWWHUVRQ E /DWH-XUDVVLF 7LWKRQLDQ±.LPPHULJLDQ±0D 0RUULVRQ)RUPDWLRQ Suuwassea emilieae+DUULVHW'RGVRQ c. (DUO\&UHWDFHRXV $SWLDQ$OELDQ±0D .RRWHQDL)RUPDWLRQ Toxolophosaurus cloudi2OVRQ G (DUO\&UHWDFHRXV $SWLDQ$OELDQ±0D &ORYHUO\)RUPDWLRQ Ceratodus frazieri2VWURP Paramacellodus keebleri1\GDPHW&LIHOOL Ptilotodon wilsoni1\GDPHW&LIHOOL Deinonychus antirrhopus2VWURP Tenontosaurus tilletti2VWURP Zephyrosaurus schaffi6XHV Sauropelta edwardsorum2VWURP Tatankacephalus cooneyorum* 3DUVRQVHW3DUVRQV Microvenator celer2VWURP Aquilops americanus)DUNHHWDO Rugocaudia cooneyi*:RRGUXII Gobiconodon ostromi-HQNLQV-UHW6FKDII Argaliatherium robustum&LIHOOLHW'DYLV Carinalestes murensis&LIHOOLHW'DYLV Montanalestes keeblerorum&LIHOOL Oklatheridium wiblei&LIHOOLHW'DYLV H 0LGGOH&UHWDFHRXV $OELDQ±&HQRPDQLDQ±0D 7KHUPRSROLV6KDOH Edgarosaurus muddi'UXFNHQPLOOHU I /DWH&UHWDFHRXV &HQRPDQLDQ0D %ODFNOHDI)RUPDWLRQ Oryctodromeus cubicularis9DUULFFKLRHWDO J /DWH&UHWDFHRXV &DPSDQLDQ±0D 7ZR0HGLFLQH)RUPDWLRQ L /RZHUOLWKRIDFLHV Cerasinops hodgkissi&KLQQHU\HW+RUQHU Acristavus gagslarsoni*DWHVHWDO Gryposaurus latidens+RUQHU LL 0LGGOHOLWKRIDFLHV Magnuviator ovimonsensis'H0DUHWDO Maiasaura peeblesorum+RUQHUHW0DNHOD Orodromeus makelai+RUQHUHW:HLVKDPSHO Bambiraptor feinbergi%XUQKDPHWDO LLL 8SSHUOLWKRIDFLHV Daspletosaurus horneri&DUUHWDO Palaeoscincus rugosidens**LOPRUH Brachyceratops montanensis*LOPRUH Achelousaurus horneri6DPSVRQ Einiosaurus procurvicornis6DPSVRQ Rubeosaurus ovatus 0F'RQDOGHW+RUQHU Oohkotokia horneri*3HQNDOVNL Prenoceratops pieganensis &KLQQHU\ Hypacrosaurus stebingeri+RUQHUHW&XUULH Prosaurolophus blackfeetensis*+RUQHU Glishades ericksoni*3ULHWR0DUTXH] Avisaurus gloriae9DUULFFKLRHW&KLDSSH Piksi barbaruina9DUULFFKLR 6HH$JQROLQ 9DUULFFKLR Montanazhdarcho minor3DGLDQHWDO K /DWH&UHWDFHRXV &DPSDQLDQ0D &ODJJHWW6KDOH Hesperornis montana6KXIHOGW L /DWH&UHWDFHRXV &DPSDQLDQ±0D -XGLWK5LYHU)RUPDWLRQ Lepidotus occidentalis/HLG\ Lepidotus haydeni*/HLG\ Myledaphus bipartitus&RSH Chiloscyllium missouriensis&DVH Psammorhynchus longipinnis*UDQGH Scapherpeton tectum&RSH 7 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics
Scapherpeton laticolle*&RSH Scapherpeton excisum*&RSH Scapherpeton favosum*&RSH Hemitrypus jordanianus*&RSH Nezpercius dodsoni%OREHWDO Deinosuchus hatcheri+ROODQG Compsemys variolosus&RSH Compsemy imbricarius&RSH Polythorax missuriensis&RSH Champsosaurus profundus&RSH Champsosaurus annectens&RSH Champsosaurus brevicollis&RSH Champsosaurus vaccinsulensis&RSH Troodon formosus/HLG\ Paronychodon lacustris&RSH Deinodon horridus*/HLG\ Zapsalis abradens*&RSH Aublysodon mirandus*/HLG\ Palaeoscincus costatus*/HLG\ Trachodon mirabilis /HLG\ Pteropelyx grallipes &RSH Diclonius calamaris*&RSH Diclonius pentagonius &RSH Diclonius perengulatus &RSH Dysganus peiganus &RSH Dysganus bicarinatus &RSH Dysganus haydenianus &RSH Dysganus encaustus &RSH Ceratops montanus*0DUVK Avaceratops lammersi'RGVRQ Mercuriceratops gemini5\DQHWDO Judiceratops tigris/RQJULFK Medusaceratops lokii5\DQHWDO Spiclypeus shipporum0DOORQHWDO Probrachylophosaurus bergei)UHHGPDQ)RZOHUHW+RUQHU Brachylophosaurus goodwini +RUQHU Zuul crurivastator$UERXUHW(YDQV Cimexomys judithae 6DKQL Cimexomys magnus6DKQL Cimolomys clarki 6DKQL Pediomys clemensi 6DKQL Alphadon halleyi 6DKQL Gypsonictops lewisi 6DKQL M /DWH&UHWDFHRXV &DPSDQLDQ±0DDVWULFKWLDQ0D %HDUSDZ)RUPDWLRQ Plioplatecarpus peckensis&XWKEHUWVRQHW+ROPHV N /DWH&UHWDFHRXV 0DDVWULFKWLDQ±0D 6W0DU\5LYHU)RUPDWLRQ Montanaceratops cerorhynchos%URZQHW6FKODLNMHU Paracimexomys propriscus+XQWHUHWDO Nidimys occultus+XQWHUHWDO Leptalestes toevsi+XQWHUHWDO O /DWH&UHWDFHRXV 0DDVWULFKWLDQ±0D +HOO&UHHN)RUPDWLRQ Paleopsephurus wilsoni 0DF$OSLQ Protoscaphirhynchus squamosus:LOLPRYVN\ Phyllodus paulkatoi(VWHVHW+LDWW Melvius thomasi%U\DQW Paranecturus garbanii'HPDU Obamadon gracilis/RQJULFK Stygiochelys estesi*DIIQH\HW+LDWW Emarginachelys cretacea:KHWVWRQH Brachychampsa montana*LOPRUH Tyrannosaurus rex2VERUQ 7ULHUDUFKXQFXVSUDLULHQVLV)RZOHUHWDO Nanotyrannus lancensis* *LOPRUH Triceratops maximus %URZQ 8 Ugrosaurus olsoni* &R%DEH HW )DVWRYVN\ Horner and Hanson: Vertebrate Paleontology
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 sh- es of both osteichthyes and chondrichthyes, amphibians, squamates, testudines, crocodil- ians, 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 speci- men 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 per- mission.
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 deposi- tion 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 deposi- tion 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 deposi- tion 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 stud- ied 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. Agnolin, F.L., and Varricchio, D.J., 2012, Systematic reinterpretation of Piksi barbaruina Varricchio, Montana continues to oﬀ er great potential for sig- 2002 from the Two Medicine Formation (Up- niﬁ cant new discoveries and research on fossil verte- per Cretaceous) of western USA (Montana) as brates and their paleoecological context. The Sapping- a pterosaur rather than a bird: Geodiversitas, ton Formation (Late Devonian–Early Mississippian) v. 34, p. 883–894, doi: https://doi.org/10.5252/ and formations of the Big Snowy Group, particularly g2012n4a10 facies of the Heath and Tyler Formations (Late Mis- sissippian–early Pennsylvanian), oﬀ er exciting future Alvarez, L.W., Alvarez, W., Asaro, F., and Michel, prospects within the Paleozoic record. The Triassic H.V., 1980, Extraterrestrial cause for the Cre- Chugwater Formation in Carbon County, although taceous–Tertiary extinction: Science, v. 208, not well exposed, has yet to produce any vertebrate p. 1095–1108, doi: https://doi.org/10.1126/sci- fossils. The Late Jurassic Morrison Formation has ence.208.4448.1095 produced a lot of fossil material that simply needs to Arbour, V.M., and Currie, P.J., 2013, Euoplocephalus be described. In the Cretaceous each of the marine tutus and the diversity of ankylosaurid dinosaurs units, and in particular the Thermopolis Formation in the Late Cretaceous of Alberta, Canada, and in Carbon County, the Telegraph Creek Formation Montana, USA: PLoS ONE, v. 8, no. 5, 39 p., doi: in Toole County, and the Bearpaw Shale in Phillips, https://doi.org/10.1371/journal.pone.0062421 Valley, and Wheatland Counties, deserves much more Arbour, V.M., and Evans, D.C., 2017, A new ankylo- attention, as do the terrestrial units such as the Living- saurine dinosaur from the Judith River Formation ston Group in Park, Gallatin, and Madison Counties. of Montana, USA, based on an exceptional skel- The 1,500-m-thick Livingston Group, composed of eton with soft tissue preservation: Royal Society several formations spanning the Late Cretaceous and Open Science, v. 4, no. 5, 28 p., doi: https://doi. early Paleocene, contains dinosaur remains, including org/10.1098/rsos.161086 skeletons, and yet the only described vertebrate speci- men is a single ﬁ sh (Schaeﬀ er, 1949). Middle Eocene Archibald, J.D., 1982, A study of Mammalia across the and middle Oligocene deposits in southwestern and Cretaceous–Tertiary boundary in Garﬁ eld County, 30 Horner and Hanson: Vertebrate Paleontology Montana: University of California Publications in Black, C.C., 1961a, Additions to the late Miocene Geological Sciences, v. 122, no. xvi, p. 1–286. Flint Creek local fauna: Annals of the Carnegie Archibald, J.D., Zhang, Y., Harper, T., and Cifelli, Museum, v. 36, p. 69–76. R.L., 2011, Protungulatum, conﬁ rmed Cretaceous Black, C.C., 1961b, Rodents and lagomorphs from the occurrence of an otherwise Paleocene Eutherian Miocene Fort Logan and Deep River Formations (placental?) mammal: Journal Mammalian Evolu- of Montana: Postilla, no. 48, 20 p. tion, v. 18, p. 153–161. Black, C.C., 1965, Fossil mammals from Montana, pt. Asher, R.J., McKenna, M.C., Emry, R.J., Tabrum, 2, Rodents from the early Oligocene Pipestone A.R., and Kron, D.G., 2002, Morphology and Springs local fauna: Annals of the Carnegie Mu- relationships of Apternodus and other extinct, seum, v. 38, p. 1–48. zalambdodont, placental mammals: Bulletin of Black, C.C., 1968, The Oligocene rodent Ischyromys the American Museum of Natural History, v. 273, and discussion of the family Ischyromyidae: An- 117 p., doi: https://doi.org/10.1206/0003-0090(20 nals of the Carnegie Museum, v. 39, p. 273–305. 02)273%3C0001:MAROAA%3E2.0.CO;2 Blob, R.W., Carrano, M.T., Rogers, R.R., Forster, Baker, K., Scannella, J., Hall, L., and Horner, J., 2011, C.A., and Espinoza, N.R., 2001, A new fossil frog Biogeographic implications of a partial ceratopsid from the Upper Cretaceous Judith River Forma- skeleton from the lower Two Medicine Formation tion of Montana: Journal of Vertebrate Paleontol- (Campanian), Montana: Journal of Vertebrate ogy, v. 21, p. 190–194, doi: https://doi.org/10.167 Paleontology, Society of Vertebrate Paleontology, 1/0272-4634(2001)021[0190:ANFFFT]2.0.CO;2 Programs and Abstracts, p. 65A–66A. Brett-Surman, M.K., and Paul, G.S., 1985, A new Barnosky, A.D., 1981, A skeleton of Mesoscalops family of bird-like dinosaurs linking Laurasia and (Mammalia, Insectivora) from the Miocene Deep Gondwanaland: Journal of Vertebrate Paleontolo- River Formation, Montana, and a review of the gy, v. 5, p. 133–138, doi: https://doi.org/10.1080/0 proscalopid moles: Evolutionary, functional, and 2724634.1985.10011851 stratigraphic relationships: Journal of Vertebrate Paleontology, v. 1, no. 3–4, p. 285–339, doi: Brown, B., 1908, The Ankylosauridae, a new family https://doi.org/10.1080/02724634.1981.10011904 of armored dinosaurs from the Upper Creta- ceous: Bulletin American Museum of Natural Barnosky, A.D., 1982, A new species of Proscalops History, v. 24, p. 187–201. (Mammalia, Insectivora) from the Arikareean Deep River Formation, Meagher County, Mon- Brown, B., 1933, A gigantic ceratopsian dinosaur, tana: Journal of Paleontology, v. 56, no. 5, p. Triceratops maximus, new species: American 1103–1111. Museum Novitates, v. 649, no. 12, p. 1–9. Barnosky, A.D., Bibi, F., Hopkins, S.S.B., and Nich- Brown, B., and Schlaikjer, E.M., 1942, The skeleton ols, R., 2007, Biostratigraphy and magnetostra- of Leptoceratops with the description of a new spe- tigraphy of the mid-Miocene Railroad Canyon cies: American Museum Novitates, no. 1169, p. 1–15. Sequence, Montana and Idaho, and age of the Brown, J.L., 1993, Sedimentology and depositional mid-Tertiary unconformity west of the Continen- history of the Lower Paleocene Tullock Mem- tal Divide: Journal of Vertebrate Paleontology, v. ber of the Fort Union Formation, Powder River 27, no. 1, p. 204–224, doi: https://doi.org/10.1671 Basin, Wyoming and Montana: U.S. Geological /0272-4634(2007)27[204:BAMOTM]2.0.CO;2 Survey Bulletin 1917, p. 1–42, doi: https://doi. Barnosky, A.D., and LaBar, W.J., 1989, Mid-Miocene org/10.3133/b1917L (Barstovian) environmental and tectonic setting Bryant, W.L., 1935, Cryptaspis and other Lower De- near Yellowstone Park, Wyoming and Montana: vonian fossil ﬁ shes from Beartooth Butte For- Geological Society of America Bulletin, v. 101, p. mation, Wyoming: Proceedings of the American 1448–1456, doi: https://doi.org/10.1671/0272-463 Philosophical Society, v. 75, p. 111–128. 4(2007)27[204:BAMOTM]2.0.CO;2
31 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics Bryant, L.J., 1987, A new genus and species of Amii- Carr, T.E., Varricchio, D.J., Sedlmayr, J.C., Roberts, dae (Holostei; Osteichthyes) from the Late Cre- E.M., and Moore, J.R., 2017, A new tyrannosaur taceous of North America, with comments on the with evidence of anagenesis and crocodile-like phylogeny of the Amiidae: Journal of Vertebrate facial sensory system: Scientiﬁ c Reports, v. 7, 11 Paleontology, v. 7, p. 349–361, doi: https://doi.org p., doi: https://doi.org/10.1038/srep44942 /10.1080/02724634.1988.10011669 Case, G.R., 1979, Additional ﬁ sh records from the Bryant, L.J., 1989, Non-dinosaurian lower vertebrates Judith River Formation (Campanian) of Mon- across the Cretaceous–Tertiary boundary in north- tana: Geobios, v. 12, p. 223–233, doi: https://doi. eastern Montana: University of California Publi- org/10.1016/S0016-6995(79)80080-7 cations in Geological Sciences, v. 134, p. 1–51. Chin, K., 2007, The paleobiological implications of Buckley, G.A., 1995, The multituberculate Catopsalis herbivorous dinosaur coprolites from the Upper from the early Paleocene of the Crazy Mountains Cretaceous Two Medicine Formation of Montana: Basin in Montana: Acta Palaeontologica Polonica, Why eat wood?: Palaios, v. 22, p. 554–566, doi: v. 40, p. 389–398. https://doi.org/10.2110/palo.2006.p06-087r Burbank, D.W., and Barnosky, A.D., 1990, The Chinnery, B.J., 2004, Description of Prenoceratops magnetochronology of Barstovian mammals in pieganensis gen et sp. nov. (Dinosauria: Neoc- southwestern Montana and implications for the eratopsia) from the Two Medicine Formation of initiation of Neogene crustal extension in the Montana: Journal of Vertebrate Paleontology, v. northern Rocky Mountains: Geological Society 24, no. 3, p. 572–590, doi: https://doi.org/10.1671 of America Bulletin, v. 102, no. 8, p. 1093–1104, /0272-4634(2004)024[0572:DOPPGE]2.0.CO;2 doi: https://doi.org/10.1130/0016-7606(1990)102 Chinnery, B.J., and Horner, J.R., 2007, A new neoc- %3C1093:TMOBMI%3E2.3.CO;2 eratopsian dinosaur linking North American and Burke, J.J., 1935, Pseudocylindrodon, a new rodent Asian taxa: Journal of Vertebrate Paleontology, genus from the Pipestone Springs Oligocene of v. 27, no. 3, p. 625–641, doi: https://doi.org/10.16 Montana: Annals of the Carnegie Museum, v. 25, 71/0272-4634(2007)27[625:ANNDLN]2.0.CO;2 p. 1–4. Cifelli, R.L., 1999, Tribosphenic mammal from the Burke, J.J., 1936, Ardynomys and Desmatolagus in the North American Early Cretaceous: Nature v. 401, North American Oligocene: Annals of the Carne- p. 363–366. gie Museum, v. 25, p. 135–154. Cifelli, R.L., Wible, J.R., and Jenkins, F.A., Jr., 1998, Burke, J.J., 1938, A new cylindrodont rodent from the Triconodont mammals from the Cloverly For- Oligocene of Montana: Annals of the Carnegie mation (Lower Cretaceous), Montana and Wyo- Museum, v. 27, p. 255–275. ming: Journal of Vertebrate Paleontology, v. 18, p. Burnham, D.A., Drestler, K.L., Currie, P.J., Bakker, 237–241, doi: https://doi.org/10.1080/02724634.1 R.T., Zhou, Z., and Ostrom, J.H., 2000, Remark- 998.10011048 able new birdlike dinosaur (Theropoda: Man- Cifelli, R.L., and Davis, B.M., 2015, Tribosphenic iraptora) from the Upper Cretaceous of Montana: mammals from the Lower Cretaceous Cloverly University of Kansas Paleontological Contribu- Formation of Montana and Wyoming: Journal tions, New Series v. 13, p. 1–14. of Vertebrate Paleontology, v. 35, no. 3, article Calede, J.J., 2016, The rise of modern mammalian fau- e920848-1-18, doi: https://doi.org/10.1080/02724 nas: Tempo and mode of faunal turnover in west- 634.2014.920848 ern Montana during the Oligocene: Seattle, Uni- Clark, J., 1941, An anaptomorphid primate from the versity of Washington, Ph.D. dissertation, 449 p. Oligocene of Montana: Journal of Paleontology, Calede, J.J., and Rasmussen, D L., 2015, Field guide v. 15, p. 562–563. to the geology and paleontology of the Cabbage Clark, J., and Guensburg, T.E., 1972, Arctoid genetic Patch beds in the Flint Creek Basin (Renova For- characters as related to the genus Parictis: Fieldi- mation, Arikareean): Northwest Geology, v. 44, p ana, v. 26, no. 1, 71 p. 157–188. 32 Horner and Hanson: Vertebrate Paleontology Clemens, W.A., 2006, Early Paleocene (Puercan) Cuthbertson, R.S., and Holmes, R.B., 2015, A new peradectid marsupials from northeastern Mon- species of Plioplatecarpus (Mosasauridae, Plio- tana, North American Western Interior: Palaeon- platecarpinae) from the Bearpaw Formation of tographica, v. 277, p. 19–31. Montana, U.S.A.: Journal of Vertebrate Paleontol- Clemens, W.A., 2011, Eoconodon (“Triisodontidae,” ogy, v. 35, 18 p., doi: https://doi.org/10.1080/0272 Mammalia) from the Early Paleocene (Puercan) 4634.2014.922980 of northeastern Montana, USA: Palaeontologia Dawson, M.R., and Constenius, K.N., 2018, Mammali- Electronica, v. 14, no. 3, 22 p. an fauna of the middle Eocene Kishenehn Forma- Clemens, W.A., 2017, A pantodont (Mammalia) from tion, Middle Fork of the Flathead River, Montana: the latest Puercan North American Land Mammal Annals of the Carnegie Museum, v. 85, p. 25–60. Age (earliest Paleocene) of the Western Interior, DeCelles, P.G., 1986, Sedimentation in a tectonically USA: Historical Biology, v. 30, no. 1–2, p. 183– partitioned, nonmarine foreland basin: The Lower 188, doi: https://doi.org/10.1080/08912963.2016. Cretaceous Kootenai Formation, southwestern 1276178 Montana: Geological Society of America Bul- Clemens, W.A., and Wilson, G.P., 2009, Early Torre- letin, v. 97, no. 8, p. 911–931, doi: https://doi. jonian mammalian local faunas from northeastern org/10.1130/0016-7606(1986)97%3C911:SIAT- Montana, in Albright, L.B. III, ed., Papers on PN%3E2.0.CO;2 geology, vertebrate paleontology, and biostratigra- DeMar, D.G., Jr., 2013, A new fossil salamander phy in honor of Michael O. Woodburne: Museum (Caudata, Proteidae) from the Upper Cretaceous of Arizona Bulletin 65, p. 111–158. (Maastrichtian) Hell Creek Formation, Montana, CoBabe, E.A., and Fastovsky, D.E., 1987, Ugrosaurus U.S.A.: Journal of Vertebrate Paleontology, v. 33, olsoni, a new ceratopsian (Reptilia: Ornithischia) no. 3, p. 588–598, doi: https://doi.org/10.1080/02 from the Hell Creek Formation of eastern Mon- 724634.2013.734887 tana: Journal of Paleontology, v. 61, p. 148–154, DeMar, D.G., Jr., Conrad, J.L., Head, J.J., Varricchio, doi: https://doi.org/10.1017/S0022336000028298 D.J., and Wilson, G.P., 2017, A new Late Cre- CoBabe, E.A., Chamberlain, K.R., Ivie, M.A., and taceous iguanodonomorph from North America Giersch, J. J., 2012, A new insect and plant and the origin of New World Pleurodonta (Squa- lagerstätte from a Tertiary lake deposit along the mata, Iguania): Proceedings of the Royal Soci- Canyon Ferry Reservoir, southwestern Montana: ety, B, v. 284, 7 p., doi: https://doi.org/10.1098/ Rocky Mountain Geology, v. 37, p. 13–30, doi: rspb.2016.1902 https://doi.org/10.2113/gsrocky.37.1.13 Dodson, P., 1986, Avaceratops lammersi: A new cera- Cooley, J.T., and Schmitt, J.G., 1998, Sedimentology topsid from the Judith River Formation of Mon- and stratigraphy of an anastomosed ﬂ uvial system tana: Philadelphia, Proceedings of the Academy in the Morrison Formation (Upper Jurassic) of of Natural Sciences, v. 138, p. 305–317. southwest Montana: Modern Geology v. 22, p. Donohoe, J.C., 1956, New aplodontid rodent 171–208. from Montana Oligocene: Journal of Mam- Cope, E.D., 1876, On some extinct reptiles and Batra- malogy, v. 37, p. 264–268, doi: https://doi. chia from the Judith River and Fox Hills beds of org/10.2307/1376688 Montana: Proceedings Academy Natural Scienc- Dorf, E., 1934, Stratigraphy and paleontology of a es, Philadelphia v. 28, p. 340–359. new Devonian Formation at Beartooth Butte, Wy- Cope, E.D., 1877, Descriptions of new Vertebra- oming: Journal of Geology v. 42, p. 720–737. ta from the upper Tertiary formations of the Dorr, J.A., Jr., 1954, Hypsoparia bozemanensis; a new West: Proceedings of the American Philosophical genus and species of Leptarctine Mustelid from Society, v. 17, p. 219–231. the late Miocene Madison Valley Formation of Cope, E.D., 1889, Notes on the Dinosauria of the Montana: Annals of the Carnegie Museum, v. 33, Laramie: The American Naturalist, v. 23, p. p. 179–184. 904–906. 33 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics Dorr, J.A., Jr., 1956, Anceney local mammal fau- Druckenmiller, P.S., 2002, Osteology of a new plesio- na, latest Miocene, Madison Valley Formation, saur from the Lower Cretaceous (Albian) Ther- Montana: Journal of Paleontology, v. 30, no. 1, p. mopolis Shale of Montana: Journal of Vertebrate 62–74. Paleontolology, v. 22, no. 1, p. 29–42. Douglass, E., 1899, The Neocene lake beds of western Eastman, C.R., 1899, Jurassic ﬁ shes from Black Hills Montana: Missoula, University of Montana, M.S. of South Dakota: Geological Society of Amer- thesis, 27 p. ica Bulletin, v. 10, p. 397–408, doi: https://doi. Douglass, E., 1900, New species of Merycochoerus in org/10.1130/GSAB-10-397 Montana: American Journal of Science, Part I, v. Elliot, D.K., and Ilyes, R.R., 1996, Lower Devonian 10, p. 428–438. vertebrate biostratigraphy of the western United Douglass, E., 1901, New species of Merycochoerus in States: Modern Geology, v. 20, p. 253–262. Montana: American Journal of Science, Part II, v. Estes, R., 1965, A new fossil salamander from Mon- 11, p. 72–83. tana and Wyoming: Copeia 1965, p. 317–331. Douglass, E., 1902, Fossil Mammalia of the White Estes, R., and Hiatt, R., 1978, Studies of fossil phyl- River beds of Montana: Transactions of the lodont ﬁ shes: A new species of Phyllodus (Elopi- American Philosophical Society, v. 20, no. 3, p. formes, Albuloidea) from the Late Cretaceous of 237–279. Montana: Paleobios, v. 28, p. 1–10. Douglass, E., 1903, New vertebrates from the Mon- Evans, D.C., Larson, D.W., and Currie, P.J., 2013, tana Tertiary: Annals of the Carnegie Museum, v. A new dromaeosaurid (Dinosauria: Theropoda) 2, p. 145–149. with Asian aﬃ nities from the latest Cretaceous of Douglass, E., 1905, The Tertiary of Montana: Mem- North America: Naturwissenschaften, v. 100, p. oirs of the Carnegie Museum, v. 2, p. 203–221. 1041–1049. Douglass, E., 1907a, Some new Merycoidodonts: An- Farke, A.A., Maxwell, W.D., Cifelli, R.L., and Wedel, nals of the Carnegie Museum, v. 4, p. 99–109. M.J., 2014, A ceratopsian dinosaur from the Low- er Cretaceous of western North America, and the Douglass, E., 1907b, New Merycoidodonts from the biogeography of Neoceratopsia: PLoS ONE, v. 9, Miocene of Montana: Bulletin of the American no. 12, 18 p., doi, https://doi.org/10.1371/journal. Museum of Natural History, v. 23, p. 202–222. pone.0112055 Douglass, E., 1908a, Rhinoceroses from the Oligo- Fiorillo, A.R., 1990, The ﬁ rst occurrence of hadrosaur cene and Miocene deposits of North Dakota and (Dinosauria) remains from the marine Claggett Montana: Annals of the Carnegie Museum, v. 4, Formation, Late Cretaceous of south-central no. 3–4, p. 256–266. Montana: Journal of Vertebrate Paleontology, v. Douglass, E., 1908b, Fossil horses from North Dakota 10, p. 515–517, doi: https://doi.org/10.1080/0272 and Montana: Annals of the Carnegie Museum, v. 4634.1990.10011834 4, no. 3–4, p. 267–277. Fiorillo, A.R., 2000, The ancient environment of the Douglass, E., 1908c, Some Oligocene lizards: An- Beartooth Butte Formation (Devonian) in Wyo- nals of the Carnegie Museum, v. 4, no. 3–4, p. ming and Montana: Combining paleontological 278–285. inquiry with federal management needs: United Douglass, E., 1908d, Vertebrate fossils from the Fort States Department of Agriculture, Forest Service Union beds: Annals of the Carnegie Museum, v. Proceedings, v. RMRS-P-15-3, p. 160–167. 5, p. 11–26. Fostowicz-Frelik, L., and Tabrum, A.R., 2009, Lep- Douglass, E., 1908e, A description of a new species of orids (Mammalia, Lagomorpha) from the Dia- Procamelus from the upper Miocene of Montana mond O Ranch local fauna, latest middle Eocene with notes upon Procamelus madisonius Doug- of southwestern Montana: Annals of the Carnegie lass: Annals of the Carnegie Museum, v. 5, no. Museum, v. 78, no. 3, p. 253–271. 2–3, p. 159-165. Fowler, D.W., Wilson, J.P., Freedman Fowler, E.A., Noto, C.R., Anduza, D., and Horner, J.R., 2020, 34 Horner and Hanson: Vertebrate Paleontology Trierarchuncus prairiensis gen. et sp. nov., the tin of the American Museum of Natural History, last alvarezsaurid: Hell Creek Formation (upper- v. 41, p. 541–556. most Maastrichtian), Montana. Cretaceous Re- Gidley, J.W., 1923, Paleocene primates of the Fort search 104560. Union, with discussion of the relationships of Fox, R.C., Scott, C.S., and Buckley, G.A., 2015, A the Eocene primates: Proceedings of the United giant purgatoriid (Plesiadapiformes) from the States National Museum, v. 63, p. 1–38. Paleocene of Montana, USA: Mosaic evolution Gidley, J.W., 1927, A true martin from the Madison in the earliest primates: Palaeontology, v. 58, p. Valley (Miocene) of Montana: Journal of Mam- 277–291, doi: https://doi.org/10.1111/pala.12141 malogy, v. 8, p. 239–242. Freedman Fowler, E.A., and Horner, J.R., 2015, A new Giﬃ n, E.B., Gabriel, D.L., and Johnson, R.E., 1987, A Brachylophosaurin Hadrosaur (Dinosauria: Or- new pachycephalosaurid skull (Ornithischia) from nithischia) with an intermediate nasal crest from the Cretaceous Hell Creek Formation of Mon- the Campanian Judith River Formation of north tana: Journal of Vertebrate Paleontology, v. 7, p. central Montana: PLoS ONE, v. 10, no. 11, 55 p., 398–407, doi: https://doi.org/10.1080/02724634.1 doi: https://doi.org/10.1371/journal.pone.0141304 988.10011672 Frick, C., 1937, Horned ruminants of North Ameri- Gilmore, C.W., 1911, A new fossil alligator from the ca: Bulletin of the American Museum of Natural Hell Creek Beds of Montana, Proceedings of the History, v. 69, 669 p. United States National Museum, v. 41, no. 1860, Gaﬀ ney, E.S., and Hiatt, R., 1971, A new baenid turtle p. 297–302. from the Upper Cretaceous of Montana: Ameri- Gilmore, C.W., 1914, A new ceratopsian dinosaur can Museum Novitates, v. 2443, p. 1–9. from the Upper Cretaceous of Montana, with note Galton, P.M., 1995, The species of the basal hypsi- on Hypacrosaurus: Smithsonian Miscellaneous lophodontid dinosaur Thescelosaurus Gilmore Collections v. 63, p. 1–10. (Ornithischia: Ornithopoda) from the Late Creta- Gilmore, C.W., 1928, Fossil footprints from the Fort ceous of North America: Abhandlungen, Neues Union (Paleocene) of Montana: Proceedings of Jahrbuch für Geologie und Paläontologie, v. 198, the United States National Museum, v. 74, p. 1–7. no. 3, p. 297–311. Gilmore, C.W., 1930, On dinosaurian reptiles from the Galton, P.M., and Sues, H.D., 1983, New data on Two Medicine Formation of Montana: Proceed- pachycephalosaurid dinosaurs (Reptilia: Ornith- ings of the United States National Museum, v. 77, ischia) from North America: Canadian Journal p. 1–39. of Earth Sciences, v. 20, no. 3, p. 462–472, doi: https://doi.org/10.1139/e83-043 Gilmore, C.W., 1946, A new carnivorous dinosaur from the Lance Formation of Montana: Smithso- Gates, T.A., Horner, J.R., Hanna, R.R. and Nelson, nian Miscellaneous Collections, v. 106, p. 1–19. C.R., 2011, New unadorned hadrosaurine had- rosaurid (Dinosauria, Ornithopoda) from the Gingerich, P.D., 1975, New North American Plesi- Campanian of North America: Journal of Verte- adapidae (Mammalia, Primates) and a biostra- brate Paleontology, v. 31, no. 4, p. 798–811, doi: tigraphic zonation of the middle and upper https://doi.org/10.1080/02724634.2011.577854 Paleocene: Contributions from the Museum of Paleontology, University of Michigan, v. 24, p. Gidley, J.W., 1909, Notes on the fossil mammalian 135–148. genus Ptilodus, with descriptions of new species: Proceedings of the U.S. National Museum, v. 36, Gingerich, P.D., Houde, P., and Krause, D., 1983, A p. 611–626. new earliest Tiﬀ anian (late Paleocene) mamma- lian fauna from the Bangtail Plateau, western Gidley, J.W., 1915, An extinct marsupial from the Fort Crazy Mountain Basin, Montana: Journal of Pale- Union with notes on the Myrmecobidae and other ontology v. 57, no. 5, p. 957–970. families of this group: Proceedings of the United States National Museum, v. 48, p. 395–402. Grande, L., and Bemis, W.E., 1991, Osteology and phylogenetic relationships of fossil and recent Gidley, J.W., 1919, New species of claenodonts from paddleﬁ shes (Polyodontidae) with comments on the Fort Union (basal Eocene) of Montana: Bulle- 35 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics the interrelationships of Acipenseriformes: Jour- Grogan, E.D., and Lund, R., 2015, Two new Acti- nal of Vertebrate Paleontology Memoir 16, v. 11, nopterygii (Vertebrata, Osteichthyes) with cosine 121 p. from the Bear Gulch Limestone (Heath Forma- Grande, L., 2006, An exquisitely preserved skeleton tion, Serpukhovian, Mississippian) of Montana representing a primitive sturgeon from the Upper USA: Proceedings of the Academy of Natural Cretaceous Judith River Formation of Montana Sciences of Philadelphia, v. 164, no. 1, p. 111– (Acipenseriformes: Acipenseridae: N. gen. and 132. sp.): Journal of Paleontology, v. 80, p. 1–39. Gutschick, R.C., Suttner, L.J., and Switek, M.J., 1962, Grogan, E.D., and Lund, R., 1995, Pigment patterns; Biostratigraphy of transitional Devonian-Mis- soft anatomy and relationships of Bear Gulch sissippian Sappington Formation of southwest Chondrichthyes (Namurian E2b; Lower Car- Montana, in Hansen, A.R., and McKeever, J.H., boniferous; Montana, USA): Geobios, v. 28, p. eds., The Devonian System of Montana and adja- 145–146, doi: https://doi.org/10.1016/S0016- cent areas: Billings Geological Society, Thirteenth 6995(95)80102-2 Annual Field Conference Guidebook, p. 79–89. Grogan, E.D., and Lund, R., 2000, Debeerius ellefseni Hanson, D.A., 2015, An early Arikareean (middle Oli- (Fam. Nov., Gen. Nov., Spec. Nov.), an autodi- gocene) mammal assemblage from west central astylic chondrichthyan from the Mississippian Montana: Journal of Vertebrate Paleontology, Pro- Bear Gulch Limestone of Montana (USA), the gram and Abstracts, p. 138. relationships of chondrichthyes, and comments on Hanson, D.A., and Scannella, J., 2016, Skull variabil- gnathostome evolution: Journal of Morphology, ity within a population of the large oreodont Me- v. 243, p. 219–245, doi: https://doi.org/10.1002/ goreodon grandis from a single locality in west (SICI)1097-4687(200003)243:3%3C219::AID- central Montana—A preliminary assessment: JMOR1%3E3.0.CO;2-1 Journal of Vertebrate Paleontology, Program and Grogan, E.D., and Lund, R., 2002, The geological and Abstracts, p. 149. biological environment of the Bear Gulch Lime- Harris, J.D., and Dodson, P., 2004, A new diplodocid stone (Mississippian of Montana, USA) and a sauropod from the Upper Jurassic Morrison For- model for its deposition: Geodiversitas, v. 24, p. mation of Montana, USA: Acta Palaeontologica 295–315. Polonica, v. 49, p. 197–210. Grogan, E.D., and Lund, R., 2008, A basal elasmo- Harris, J.D., and Lacovara, K.J., 2010, Enigmatic fos- branch, Thrinacoselache gracia n. gen and sp., sil footprints from the Sundance Formation (Up- (Thrinacodontidae, new family) from the Bear per Jurassic) of Bighorn Canyon National Recre- Gulch Limestone, Serpukhovian of Montana, ation Area, Wyoming: Ichnos, v. 11, p. 151–166, USA: Journal of Vertebrate Paleontology, v. 28, p. doi: https://doi.org/10.1080/10420940490442304 970–988, doi: https://doi.org/10.1671/0272-4634- Hibbard, C.W., and Keenmon, K.A., 1950, New evi- 28.4.970 dence of the lower Miocene age of the Blacktail Grogan, E., and Lund, R., 2009, Two new inioptery- Deer Creek Formation in Montana: Contributions gians (Chondrichthyes) from the Mississippian from the Museum of Paleontology, Ann Arbor, (Serpukhovian) Bear Gulch Limestone of Mon- University of Michigan, v. 8, p. 193–204. tana with evidence of a new form of chondrich- Holland, W.J., 1909, Deinosuchus hatcheri, a new ge- thyan neurocranium: Acta Zoologica v. 90, no. s1, nus and species of crocodile from the Judith River p. 134–151, doi: https://doi.org/10.1111/j.1463- beds of Montana: Carnegie Museum Annals, v. 6, 6395.2008.00371.x p. 281–294. Grogan, E.D., Lund, R., and Fath, M., 2014, A new Hopkins, S.S.B., 2004, Phylogeny and biogeography petalodont chondrichthyan from the Bear Gulch of the genus Ansomys Qiu, 1987 (Mammalia: Limestone of Montana, USA, with reassessment Rodentia: Aplodontidae) and a description of a of Netsepoye hawesi and comments on the mor- new species from the Barstovian (mid-Miocene) phology of homomorphic petalodonts: Paleonto- of Montana: Journal of Paleontology, v. 78, no. 4, logical Journal, v. 48, p. 1003–1014. 36 Horner and Hanson: Vertebrate Paleontology p. 731–740, doi: https://doi.org/10.1666/0022-336 ridae) from Montana and Alberta, in Carpenter, 0(2004)078%3C0731:PABOTG%3E2.0.CO;2 K., Hirsch, K.F., and Horner, J.R., eds., Dinosaur Horner, J.R., 1979, Upper Cretaceous dinosaurs from eggs and babies: Cambridge, Massachusetts, the Bearpaw Shale (marine) of south-central Mon- Cambridge University Press, p. 312–336. tana, with a checklist of Upper Cretaceous dinosaur Horner, J.R., Goodwin, M.B., and Myhrvold, N., 2011, remains from marine sediments in North America: Dinosaur census reveals abundant Tyrannosaurus Journal of Paleontology, v. 53, p. 566–577. and rare ontogenetic stages in the Upper Cre- Horner, J.R., 1982, Evidence of colony nesting and taceous Hell Creek Formation (Maastrichtian), “site ﬁ delity” among ornithischian dinosaurs: Montana, USA: PLoS ONE, v. 6, 9 p., doi: https:// Nature, v. 297, p. 675–676. doi.org/10.1371/journal.pone.0016574 Horner, J.R., 1985, The stratigraphic position of the Horner, J.R., and Makela, R., 1979, Nest of juveniles Bear Gulch Limestone (mid Carboniferous) of provides evidence of family structure among central Montana, in Neuvième Congrès Interna- dinosaurs: Nature v. 281, p. 296–298. tional Stratigraphic and Geological Carboniﬁ ère: Horner, J.R., and Weishampel, D.B., 1988, A compar- Compte Rendu v. V, p. 427–436. ative embryological study of two ornithischian Horner, J.R., 1988, A new hadrosaur (Reptilia, Ornith- dinosaurs: Nature v. 332, p. 256–257. ischia) from the Upper Cretaceous Judith River Houde, P., 1988, Paleognathus birds from the early Formation of Montana: Journal of Vertebrate Tertiary of the Northern Hemisphere: Publica- Paleontology v. 8, p. 314–321, doi: https://doi.org tions of the Nuttall Ornithological Club, v. 22, p. /10.1080/02724634.1988.10011714 1–148. Horner, J.R., 1989, The Mesozoic terrestrial ecosys- Hough, J., 1955, An upper Eocene fauna from the tems of Montana, in French, D.E., and Grabb, Sage Creek area, Beaverhead County, Montana: R.F., eds., Geologic Resources of Montana: Journal of Paleontology, v. 29, no. 1, p. 22–36. Montana Geological Society Field Conference Hough, J.R., 1961, Review of Oligocene didelphid Guidebook, Montana Centennial edition, v. 1, p. marsupials: Journal of Paleontology, v. 35, no. 1, 153–162. p. 218–228. Horner, J.R., 1992, Cranial morphology of Prosaurol- Hutchison, J.H., 2009, New soft-shelled turtles (Plas- ophus (Ornithischia: Hadrosauridae) with de- tomeninae, Trionychidae, Testudines) from the scriptions of two new hadrosaurid species and an Late Cretaceous and Paleocene of North America: evaluation of hadrosaurid phylogenetic relation- PaleoBios, v. 29, no. 2, p. 36–47. ships: Museum of the Rockies Occasional Paper v. 2, p. 1–119. Hutchison, J.H., 2013, New turtles from the Paleogene of North America, in Brinkman, D.B., Holroyd, Horner, J.R., 1999, Egg clutches and embryos of two P.A., and Gardner, J.D., eds., Morphology and hadrosaurian dinosaurs: Journal of Vertebrate Evolution of Turtles: Springer, p. 477–497. Paleontology, v. 19, p. 607–611, doi: https://doi.or g/10.1080/02724634.1999.10011174 Hunter, J.P, Heinrich, R.E., and Weishampel, D.B., 2010, Mammals from the St. Mary River For- Horner, J.R., and Lund, R., 1985, Biotic distribution mation (Upper Cretaceous), Montana: Journal of and diversity in the Bear Gulch Limestone, in Vertebrate Paleontology, v. 30, p. 885–898, doi: Neuvième Congrès International Stratigraphic https://doi.org/10.1080/02724631003763490 and Geological Carboniﬁ ère: Compte Rendu v. V, p. 437–442. Jackson, F., and Varricchio, D.J., 2016, Fossil egg and eggshells from the Upper Cretaceous Hell Creek Horner, J.R., Varricchio, D.J., and Goodwin, M.B., Formation, Montana: Journal of Vertebrate Pale- 1992, Marine transgressions and the evolution of ontology, v. 36, 14 p., doi: https://doi.org/10.1080 Cretaceous dinosaurs: Nature, v. 358, p. 59–61. /02724634.2016.1185432 Horner, J.R., and Currie, P.J., 1994, Embryonic and Janvier, P., and Lund, R., 1983, Hardistiella montan- neonatal morphology and ontogeny of a new spe- ensis n. gen. et sp. (Petromyzontida) from the cies of Hypacrosaurus (Ornithischia, Lambeosau- Lower Carboniferous of Montana, with remarks 37 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics on the aﬃ nities of the lampreys: Journal of of Paleontology, Ann Arbor, University of Michi- Vertebrate Paleontology v. 2, p. 407–413, doi: gan, v. 26, p. 157–196. https://doi.org/10.1080/02724634.1983.10011943 Kuenzi, W.D., and Fields, R.W., 1971, Tertiary stratig- Jenkins, F.A., and Schaﬀ , C.R., 1988, The Early raphy, structure, and geologic history, Jeﬀ erson Cretaceous mammal Gobiconodon (Mammalia, Basin, Montana: Geological Society of America Triconodonta) from the Cloverly Formation in Bulletin, v. 82, no. 12, p. 3373–3394, doi: https:// Montana: Journal of Vertebrate Paleontology, v. 8, doi.org/10.1130/0016-7606(1971)82[3373:TS- p. 1–24, doi: https://doi.org/10.1080/02724634.19 SAGH]2.0.CO;2 88.10011681 Lash, C.E., 2011, Depositional environment and Koerner, H.E., 1940, The geology and vertebrate taphonomy of marine vertebrate biofacies in the paleontology of the Fort Logan and Deep River Lower Cretaceous (Albian) Thermopolis Shale, formations of Montana: American Journal of Sci- south-central Montana: Bozeman, Montana State ence, v. 238, no. 12, p. 837–862. University, M.S. thesis, 172 p. Korth, W.W., 1981, New Oligocene rodents from Leidy, J., 1856, Notices of the remains of extinct western North America: Annals of the Carnegie reptiles and ﬁ shes, discovered by Dr. F.V. Hayden Museum, v. 50, p. 289–318. in the badlands of the Judith River, Nebraska Korth, W.W., 1992, A new genus of prosciurine rodent Territory: Proceedings of the Academy of Natural (Mammalia: Rodentia: Aplodontidae) from the Sciences v. 8, p. 72. Oligocene (Orellan) of Montana: Annals of the Leidy, J., 1873, Contributions to the extinct vertebrate Carnegie Museum, v. 61, p. 171–175. fauna of the Western Territories, in Hayden, F.V., Korth, W.W., 2012, Aplodontid rodents (Mammalia) ed., Report of the U.S. Geological Survey of the from the Orellan (early Oligocene) Canyon Ferry Territories, Part 1, p. 14–358. fauna of Montana: Paludicola, v. 9, no. 1, p. 1–6. LaRock, J.W., 2001, Sedimentology and taphonomy Korth, W.W., and Tabrum, A.R., 2011, A new aplodon- of a dinosaur bonebed from the Upper Cretaceous toid rodent (Mammalia) from the early Oligocene (Campanian) Judith River Formation of north (Orellan) of Montana and a suggested origin for central Montana: Bozeman, Montana State Uni- the family Mylagaulidae: Annals of the Carnegie versity, M.S. thesis, p. 1–61. Museum, v. 80, no. 1, p. 67–81. Lillegraven, J.A., and Tabrum, A.R., 1983, A new Korth, W.W., and Tabrum, A.R., 2016, A new genus of species of Centetodon (Mammalia, Insectivora, cylindrodontid rodent from the Chadronian (late Geolabididae) from southwestern Montana and Eocene) of southwestern Montana and a reas- its biogeographical implications: Contributions to sessment of the genus Pseudocylindrodon Burke, Geology, University of Wyoming, v. 22, p. 57–73. 1935: Annals of the Carnegie Museum, v. 84, no. Longrich, N.R., 2013, Judiceratops tigris, a new 1, p. 75–93. horned dinosaur from the Middle Campanian Korth, W.W., and Tabrum, A.R., 2017, Rodents (Mam- Judith River Formation of Montana: Bulletin of malia) from Diamond O Ranch local fauna, the Peabody Museum of Natural History, v. 54, p. southwestern Montana: Annals of the Carnegie 51–65. Museum, v. 84, no. 4, p. 301–318. Lorenz, J.C., and Gavin, W., 1984, Geology of the Krause, D.W., 1987, Baiotomeus, a new ptilodontid Two Medicine Formation and the sedimentology multituberculate (Mammalia) from the middle of a dinosaur nesting ground, in McBane, J.D., Paleocene of western North America: Journal of and Garrison, P.B., eds., Northwest Montana and Paleontology, v. 61, p. 595–603, doi: https://doi. adjacent Canada: Montana Geological Society org/10.1017/S0022336000028766 Field Conference Guidebook, p. 175–186. Krause, D.W., and Gingerich, P.D., 1983, Mammalian Lund, R., 1974, Stethacanthus altonen- fauna from the Douglas Quarry, earliest Tiﬀ anian sis (Elasmobranchii) from the Bear Gulch (Late Paleocene) of the eastern Crazy Mountain Limestone of Montana: Annals of the Carnegie Basin, Montana: Contributions from the Museum Museum, v. 45, p. 161–178. 38 Horner and Hanson: Vertebrate Paleontology Lund, R., 1977a, Echinochimaera meltoni new genus Museum Natural History, (serie C) v. 53, p. and species (Chimaeriformes), from the Mis- 195–205. sissippian of Montana: Annals of the Carnegie Lund, R., 1989, New petalodonts (Chondrichthyes) Museum, v. 46, p. 195–221. from the Upper Mississippian Bear Gulch Lime- Lund, R., 1977b, A new petalodont (Chondrichthyes, stone (Namurian E2b) of Montana: Journal of Bradyodonti) from the Upper Mississippian of Vertebrate Paleontology v. 9, p. 350–368, doi: Montana: Annals of the Carnegie Museum, v. 46, https://doi.org/10.1080/02724634.1989.10011767 p. 129–155. Lund, R., 1990, Chondrichthyan life history styles as Lund, R., 1980, Viviparity and intrauterine feeding in revealed by the 320 million years old Mississippi- a new holocephalan ﬁ sh from the Lower Carbon- an of Montana: Environmental Biology of Fishes, iferous of Montana: Science v. 209, p. 697–699, v. 27, p. 1–19. doi: https://doi.org/10.1126/science.209.4457.697 Lund, R., 2000, The new actinopterygian order Guil- Lund, R., 1982, Harpagofututor volsellorhi- dayichthyiformes from the Lower Carbonifer- nus new genus and species (Chondrichthyes, ous of Montana (USA): Geodiversitas, v. 22, p. Chondrenchelyiformes) from the Namurian 171–206. Bear Gulch Limestone, Chondrenchelys prob- Lund, R., Greenfest-Allen, E., and Grogan, E.D., lematica Traquair (Visean) and their sexual 2012, Habitat and diversity of the Bear Gulch dimorphism: Journal of Paleontology, v. 56, p. ﬁ sh: Life in a 318 million year old Mississippian 938–958. bay: Palaeogeography, Palaeoclimatology, Palae- Lund, R., 1983, On a dentition of Polyrhizodus (Chon- oecology, v. 342–343, p. 1–16, doi: https://doi. drichthyes, Petalodontiformes) from the Bear org/10.1016/j.palaeo.2012.04.016 Gulch Limestone: Journal of Vertebrate Paleon- Lund, R., and Grogan, E.D., 1997a, Cochliodonts from tology v. 3, p. 1–6, doi: https://doi.org/10.1080/02 the Mississippian Bear Gulch Limestone Heath 724634.1983.10384478 Formation; Big Snowy Group (Chesterian) of Lund, R., 1984, On the spines of the Stethacanthidae Montana and the relationships of the Holoceph- (Chondrichthyes), with a description of a new ali: Dinofest International Symposium, Proceed- genus from the Mississippian Bear Gulch Lime- ings for 1997, p. 477–492. stone: Geobios, v. 17, p. 281–295, doi: https://doi. Lund, R., and Grogan, E.D., 1997b, Relationships of org/10.1016/S0016-6995(84)80095-9 the Chimaeriformes and the basal radiation of the Lund, R., 1985, The morphology of Falcatus fal- Chondrichthyes: Reviews in Fish Biology and catus (St. John and Worthen), a Mississippian Fisheries, v. 7, p. 65–123. stethacantid chondrichthyan from the Bear Gulch Lund, R., and Grogan, E.D., 2004, Two tenacu- Limestone of Montana: Journal of Vertebrate lum-bearing Holocephalimorpha (Chondrich- Paleontology, v. 5, p. 1–19, doi: https://doi.org/10. thyes) from the Bear Gulch Limestone (Ches- 1080/02724634.1985.10011842 terian, Serpukhovian) of Montana, USA, part Lund, R., 1986, On Damocles serratus, nov. gen. et sp. 1, in Arratia, G., Wilson, M.V.H., and Cloutier, (Elasmobranchii, Cladodontida) from the Upper R., eds., Recent advances in the origin and early Mississippian Bear Gulch Limestone of Mon- radiation of vertebrates: München,Verlag Dr. Frie- tana: Journal of Vertebrate Paleontology, v. 6, p. drich Pfeil, p. 171–188. 12–19, doi: https://doi.org/10.1080/02724634.198 Lund, R., and Grogan, E.D., 2013, Fossil ﬁ shes of 6.10011594 Bear Gulch: http://people.sju.edu/~egrogan/Bear- Lund, R., 1988, New Mississippian Holocephali Gulch/index.html [Accessed March, 11, 2020]. (Chondrichthyes) and the evolution of the Ho- Lund, R., and Lund, W.L., 1984, New genera and locephali, in Russell, D.E., Santoro, J.P., and species of coelacanths from the Bear Gulch Sigogneau-Russell, D., eds., Teeth Revisited: Limestone (Lower Carboniferous) of Montana Proceedings of the VII International Symposium (U.S.A.): Geobios, v. 17, p. 237–244, doi: https:// on Dental Morphology: Paris, Memoir National doi.org/10.1016/S0016-6995(84)80145-X 39 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics Lund, R., and Melton, W.G., Jr., 1982, A new acti- Matthew, W.D., 1903, The fauna of the Titanotherium nopterygian ﬁ sh from the Mississippian Bear beds at Pipestone Springs, Montana: Bulletin of Gulch Limestone of Montana: Palaeontology, v. the American Museum of Natural History, v. 19, 25, p. 85–498. art. 6, p. 197–226. Lund, R., and Poplin, C., 1997, The rhadinichthy- Matthew, W.D., and Mook, C.C., 1933, New fossil ids (paleoniscoid actinopterygians) from the mammals from the Deep River beds of Montana: Bear Gulch Limestone of Montana: Journal of American Museum Novitates, no. 601, 7 p. Vertebrate Paleontology, v. 17, p. 466–486, doi: Maxwell, W.D., and Horner, J.R., 1994, Neonate https://doi.org/10.1080/02724634.1997.10010996 dinosaurian remains and dinosaurian eggshell Lund, R., and Zangerl, R., 1974, Squatinactis cau- from the Cloverly Formation, Montana: Journal dispinatus, a new elasmobranch from the Upper of Vertebrate Paleontology, v. 14, p. 143–146, doi: Mississippian of Montana: Annals of the Carnegie https://doi.org/10.1080/02724634.1994.10011547 Museum, v. 45, p. 43–54. Maxwell, W.D., and Ostrom, J.H., 1995, Taphonomy Lund, R., Grogan, E.D., and Fath, M., 2014, On the and paleontological implications of Tenontosau- relationships of the Petalodontiformes (Chon- rus-Deinonychus associations: Journal of Verte- drichthyes): Paleontological Journal, v. 48, no. 9, brate Paleontology v. 15, no. 4, p. 707–712, doi: p. 1015–1029. https://doi.org/10.1080/02724634.1995.10011256 MacAlpin, A.J., 1947, Paleopsephurus wilsoni a new McDonald, A.T., and Horner, J.R., 2010, New material polyodontid ﬁ sh from the Upper Cretaceous of of “Styracosaurus” ovatus from the Two Medi- Montana, with a discussion of allied ﬁ sh, living cine Formation of Montana, in Ryan, M.J., Chin- and fossil: Contributions of the Museum of nery-Allgeier, B.J., and Eberth, D.A., eds., New Paleontology, Ann Arbor, University of Michigan, perspectives on horned dinosaurs: The Royal v. 6, p. 167–234. Tyrrell Museum Ceratopsian Symposium: Bloom- Macdonald, J.R., 1956, The North American anthra- ington and Indianapolis, Indiana University Press, cotheres: Journal of Paleontology, v. 30, no. 3, p. p. 156–168. 615–645. McKenna, M.C., 1990, Plagiomenids (Mammalia: Maidment, S.C.R., Woodruﬀ , D.C., and Horner, J.R., ?Dermoptera) from the Oligocene of Oregon, 2018, A new specimen of the ornithischian dino- Montana, and South Dakota, and middle Eocene saur Hesperosaurus mjosi from the Upper Jurassic of northwestern Wyoming, in Bown, T.M. and Morrison Formation of Montana, USA and impli- Rose, K.D.,eds., Dawn of the Age of Mammals in cations for growth and size in Morrison stegosaurs: the northern part of the Rocky Mountain interior, Journal of Vertebrate Paleontology, 22 p., doi: North America: Geological Society of America https://doi.org/10.1080/02724634.2017.1406366 Special Paper 243, p. 211–234. Mallon, J.C., Ott, C.J., Larson, P.L., Iuliano, E.M., and Melton, W.G., and Scott, H., 1973, Conodont bearing Evans, D.C., 2016, Spiclypeus shipporum gen. animals from the Bear Gulch Limestone, Mon- et sp. nov., a boldly audacious new chasmosau- tana: Geological Society of America Special rine ceratopsid (Dinosauria: Ornithischia) from Paper 141, p. 31–65. the Judith River Formation (Upper Cretaceous: Mickle, K.E., Lund, R., and Grogan, E.D., 2009, Campanian) of Montana, USA: PLoS ONE, v. 11, Three new palaeoniscoid ﬁ shes from the Bear no. 5, 40 p., doi: https://doi.org/10.1371/journal. Gulch Limestone (Serpukhovian, Mississippian) pone.0154218 of Montana (USA) and the relationships of lower Marsh, O.C., 1888, A new family of horned Dinosau- actinopterygians: Geodiversitas, v. 31, p. 623– ria from the Cretaceous: The American Journal of 668, doi: https://doi.org/10.5252/g2009n3a6 Science, ser. 3, v. 36, p. 477–478. Moberly, R.M., Jr., 1960, Morrison, Clover- Marsh, O.C., 1890, Description of new dinosaurian ly, and Sykes Mountain Formations, north- reptiles: American Journal of Science, ser. 3, v. ern Bighorn Basin, Wyoming and Mon- 34, p. 81–86. tana: Geological Society of America Bulletin, v. 71, p.1137–1176, doi: https://doi. 40 Horner and Hanson: Vertebrate Paleontology org/10.1130/0016-7606(1960)71[1137:MCASM- O’Leary, M.A., Bloch, J.I., Flynn, J.J., Gaudin, T.J., F]2.0.CO;2 Giallombardo, A., Giannini, N.P., Goldberg, Montellano, M., 1988, Alphadon halleyi (Didelphidae, S.L., Kraatz, B.P., Luo, Z.-X., Meng, J., Ni, Marsupialia) from the Two Medicine Formation X., Novacek, M.J., Perini, F.A., Randall, Z.S., (Late Cretaceous, Judithian) of Montana: Journal Rougier, G.W., Sargis, E.J., Silcox, M.T., Sim- of Vertebrate Paleontology, v. 8, p. 378–382, doi: mons, N.B., Spaulding, M., Velazco, P.M., https://doi.org/10.1080/02724634.1988.10011726 Weksler, M., Wible, J.R., and Cirranello, A.L., 2013, The placental mammal ancestor and the Montellano, M., 1992, Mammalian fauna of the Judith post-K-Pg radiation of placentals: Science, v. River Formation (Late Cretaceous, Judithian), 339, p. 662–667, doi: https://doi.org/10.1126/sci- north central Montana: Los Angeles, University ence.1229237 of California Publications in Geological Sciences, v. 136, p. 1–114. Olson, E.C., 1960, A Trilophosaurid reptile from the Kootenai Formation (Lower Cretaceous): Journal Montellano, M., Weil, A., and Clemens, W.A., 2000, of Paleontology, v. 34, p. 551–555. An exceptional specimen of Cimexomys judithae (Mammalia: Multituberculata) from the Campa- Oreska, M.P.J., Carrano, M.T., and Dzikiewicz, K.M., nian Two Medicine Formation of Montana, and 2013, Vertebrate paleontology of the Cloverly phylogenetic status of Cimexomys: Journal of Formation (Lower Cretaceous), I: Faunal compo- Vertebrate Paleontology, v. 20, no. 2, p. 333–340, sition, biostratigraphic relationships, and sam- doi: https://doi.org/10.1671/0272-4634(2000)020[ pling: Journal of Vertebrate Paleontology, v. 33, 0333:AESOCJ]2.0.CO;2 no. 2, p. 264–292, doi: https://doi.org/10.1080/02 724634.2012.717567 Murphy, N.L., Trexler, D., and Thompson, M., 2006, “Leonardo,” a mummiﬁ ed Brachylophosaurus Ostrander, G.E., 1983, A new genus of eomyid (Mam- from the Judith River Formation, in Carpenter, malia, Rodentia) from the early Oligocene (Cha- K., Horns and beaks: Ceratopsian and Ornitho- dronian), Pipestone Springs, Montana: Journal of pod dinosaurs: Bloomington, Indiana University Paleontology, v. 57, no. 1, p. 140–144. Press, p. 117–133. Osborn, H.F., 1904, New Oligocene horses: Bulletin Myers, T.S., and Storrs, G.W., 2007, Taphonomy of the American Museum of Natural History, v. of the Mother’s Day Quarry, Upper Jurassic 20, p. 167–179. Morrison Formation, south-central Montana, Osborn, H.F., 1905, Tyrannosaurus and other Cre- USA: Palaios, v. 22, p. 651–666, doi: https://doi. taceous carnivorous dinosaurs: Bulletin of the org/10.2110/palo.2005.p05-123r American Museum of Natural History, v. 21, p. Nichols, R., 2001, Cenozoic vertebrate paleontology 259–265. and geology of southwestern Montana and adja- Ostrom, J.H., 1969, Osteology of Deinonychus an- cent areas, in Guidebook for the Field Trips, Hill, tirrhopus, an unusual theropod from the Lower C.L., ed., Guidebook for the Field Trips: Society Cretaceous of Montana: Bulletin of the Peabody of Vertebrate Paleontology 61st Annual Meeting, Museum of Natural History, v. 30, p. 1–165. Bozeman, Museum of the Rockies Occasional Ostrom, J.H., 1970, Stratigraphy and paleontology of Paper no. 3, p. 77–144. the Cloverly Formation (Lower Cretaceous) of Novacek, M.J., 1977, A review of Paleocene and the Bighorn Basin area, Wyoming and Montana: Eocene Leptictidae (Eutheria: Mammalia) from Bulletin of the Peabody Museum Natural History, North America: Paleobios, v. 24, p. 1–24. v. 35, p. 1–234. Nydam, R.L., and Cifelli, R.L., 2002, Lizards from Ostrom, J.H., 1976, Archaeopteryx and the origin of the Lower Cretaceous (Aptian–Albian) Antlers birds: Biological Journal of the Linnean Society, and Cloverly Formations: Journal of Vertebrate v. 8, p. 91–182. Paleontology, v. 22, p. 286–298, doi: https://doi. Padian, K., 1984, A large pterodactyloid from the Two org/10.1671/0272-4634(2002)022[0286:LFTL- Medicine Formation (Campanian) of Montana: CA]2.0.CO;2
41 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics Journal of Vertebrate Paleontology, v. 4, no. 4, p. org/10.1671/0272-4634(2005)025[0144:NIOT- 516–524, doi: https://doi.org/10.1080/02724634.1 CO]2.0.CO;2 984.10012027 Prieto-Marquez, A., 2010, Glishades ericksoni, a new Padian, K., de Ricqlès, A.J., and Horner, J.R., 1995, hadrosauroid (Dinosauria: Ornithopoda) from the Bone histology determines identiﬁ cation of a new Late Cretaceous of North America: Zootaxa, v. fossil taxon of pterosaur (Reptilia: Archosauria): 2452, no. 1, p. 1–17. Comptes Rendus de l’Academie des Science, Prothero, D.R., 1986, A new Oromerycid (Mam- serie II, v. 320, p. 77–84. malia, Artiodactyla) from the early Oligocene Parcell, W., and Williams, M., 2005, Mixed sediment of Montana: Journal of Paleontology, v. 60, deposition in a retro-arc foreland basin: Lower no. 2, p. 458–465, doi: https://doi.org/10.1017/ Ellis Group (M. Jurassic), Wyoming and Mon- S0022336000021983 tana, U.S.A.: Sedimentary Geology, v. 177, no. Radinsky, L.B., 1967, A Review of the Rhinocerotoid 3–4, p. 175–194, doi: https://doi.org/10.1016/j. Family Hyracodontidae (Perissodactyla): Bulletin sedgeo.2005.02.007 of the American Museum of Natural History, v. Parsons, W.L., and Parsons, K.M., 2009, A new anky- 136, no. 1, 46 p. losaur (Dinosauria: Ankylosauria) from the Lower Reed, C.A., 1954, Some fossorial mammals from the Cretaceous Cloverly Formation of central Mon- Tertiary of western North America: Journal of tana: Canadian Journal of Earth Sciences, v. 46, Paleontology, v. 28, no. 1, p. 102–111. no. 10, p. 721–738, doi: https://doi.org/10.1139/ E09-045 Rensberger, J.M., 1981, Evolution in a late Oligo- cene–early Miocene succession of meniscomyine Penkalski, P., 2013, A new ankylosaurid from the Late rodents in the Deep River Formation, Montana: Cretaceous Two Medicine Formation of Montana, Journal of Vertebrate Paleontology, v. 1, no. 2, p. USA: Acta Palaeontologia Polonica, v. 59, p. 185–209, doi: https://doi.org/10.1080/02724634.1 617–634. 981.10011891 Poplin, C., and Lund, R., 2000, Two new Rich, T.H.V., and Rasmussen, D.L., 1973, New North deep-bodied actinopterygians from Bear American erinaceine hedgehogs (Mammalia, Gulch, (Montana, USA, Lower Carbonif- Insectivora): Occasional Papers of the Museum of erous): Journal of Vertebrate Paleontolo- Natural History, Lawrence, University of Kansas, gy, v. 20, no. 3, p. 428–449, doi: https://doi. v. 21, p. 1–54. org/10.1671/0272-4634(2000)020[0428:TNDB- PA]2.0.CO;2 Rogers, R.R, Swisher III, C.C., and Horner, J.R., 1993, 40Ar/39Ar age and correlation of the non-marine Poplin, C., and Lund, R., 2002, Two Carboniferous Two Medicine Formation (Upper Cretaceous), ﬁ ne-eyed paleoniscoids (Pisces, Actinopterygii) northwestern Montana, USA: Canadian Journal of from Bear Gulch (USA): Journal of Paleontol- Earth Sciences, v. 30, p. 1066–1075, doi: https:// ogy, v. 76, no. 6, p. 1014–1028, doi: https://doi. doi.org/10.1139/e93-090 org/10.1017/S002233600005784X Ryan, M.J., Evans, D.C., Currie, P.J., and Loewen, Porter, K.W., Dyman, T.S., Tysdal, R.G., 1993, Se- M.A., 2014, A new chasmosaurine from northern quence boundaries and other surfaces in Lower Larmidia expands frill disparity in ceratopsid di- and lower Upper Cretaceous rocks of central nosaurs: Naturwissenschaften, v. 101, p. 505–512. and southwest Montana: A preliminary report, in Hunter, L.D., ed., Energy and mineral resources Ryan, M.J., Russell, A.P., and Hartman, S., 2010, A of central Montana: Montana Geological Society new chasmosaurine ceratopsid from the Judith Field Conference Guidebook, p. 45–59. River Formation, Montana, in Ryan, M.J., Chin- nery-Allgeier, B.J., and Ebreth, D.A., eds., New Prieto-Marquez, A., 2005, New information on the cra- Perspectives on Horned Dinosaurs: The Royal nium of Brachylophosaurus, with a revision of its Tyrrell Museum Ceratopsian Symposium, Bloom- phylogenetic position: Journal of Vertebrate Pale- ington, Indiana University Press, p. 91–116. ontology, v. 25, no. 1, p. 144–156, doi: https://doi.
42 Horner and Hanson: Vertebrate Paleontology Sahni, A., 1972, The vertebrate fauna of the Judith Shufeldt, R.W., 1915, The fossil remains of a species River Formation, Montana: Bulletin of the Amer- of Hesperornis found in Montana: The Auk, v. 32, ican Museum of Natural History, v. 147, no. 6, p. p. 290–294. 321–412. Simmons, N.B., 1987, A revision of Taeniolabis Sampson, S.D., 1995, Two new horned dinosaurs from (Mammalia: Multituberculata), with a new spe- the Upper Cretaceous Two Medicine Formation cies from the Puercan of eastern Montana: Journal of Montana; with a phylogenetic analysis of the of Paleontology, v. 61, no. 4, p. 794–808, doi: Centrosaurinae (Ornithischia: Ceratopsidae): https://doi.org/10.1017/S0022336000029140 Journal of Vertebrate Paleontology, v. 15, no. 4, p. Simpson, G.G., 1927, Mammalian fauna of the Hell 743–760, doi: https://doi.org/10.1080/02724634.1 Creek Formation of Montana: American Museum 995.10011259 Novitates, no. 267, p. 1–7. Sandberg, C.A., 1961, Widespread Beartooth Butte Simpson, G.G., 1928, A new mammalian fauna from Formation of Early Devonian age in Montana and the Fort Union of southern Montana: American Wyoming and its paleogeographic signiﬁ cance: Museum Novitates, no. 297, p. 1–15. American Association of Petroleum Geologists Bulletin, v. 45, p. 1301–1309. Simpson, G.G., 1935, New Paleocene mammals from the Fort Union of Montana: Proceedings of the Schaeﬀ er, B., 1949, A teleost from the Livingston United States National Museum, v. 83, p. 221– Formation of Montana: American Museum Novi- 244. tates, no. 1427, p. 1–16. Simpson, G.G., 1936, A new fauna from the Fort Schaeﬀ er, B., and Patterson, C., 1984, Jurassic ﬁ shes Union of Montana: American Museum Novitates, from the western United States, with comments no. 873, p. 1–27. on Jurassic ﬁ sh distribution: American Museum Novitates, no. 2796, p. 1–86. Simpson, G.G., 1937, The Fort Union of the Crazy Mountain ﬁ eld, Montana and its mammalian fau- Schmitt, J.G., Jackson, F.D., and Hanna, R.R., 2014, nas: Washington, D.C., Smithsonian Institution, Debris ﬂ ow origin of an unusual Late Cretaceous United States National Museum Bulletin 169, p. hadrosaur bonebed in the Two Medicine Forma- 1–287. tion of western Montana, in Eberth, D, and Evans, D., eds., Hadrosaurs: Bloomington, Indiana Uni- Simpson, G.G., 1940, Studies on the earliest primates: versity Press, p. 486–501. Bulletin of the American Museum of Natural His- tory, v. 77, p. 185–212. Schweitzer, M.H., Zheng, W., Organ, C.L., Avci, R., Suo, Z., Freimark, L.M., Lebleu, V.S., Duncan, Simpson, G.G., 1941, A new Oligocene Insectivore: M.B., Vander Heiden, M.G., Neveu, J.M., Lane, American Museum Novitates, no. 1150, 3 p. W.S., Cottrell, J.S., Horner, J.R., Cantley, L.C., Sloan, R.E., 1981, Systematics of Paleocene multitu- Kalluri, R., and Asara, J.M., 2009, Biomolecu- berculates from the San Juan Basin, New Mexico, lar characterization and protein sequences of the in Lucas, S.G., Rigby, J.K. Jr.,, and Kues, B.S., Campanian hadrosaur B. canadensis: Science, v. eds., Advances in San Juan Basin Paleontology: 324, p. 626–631, doi: https://doi.org/10.1126/sci- Albuquerque, University of New Mexico Press, p. ence.1165069 127–160. Scott, 1893, The Mammalia of the Deep River beds: Sloan, R.E., 1987, Paleocene and latest Cretaceous Transactions of the American Philosophical Soci- mammal ages, biozones, magnetozones, rates ety, v. 18, no. 2, p. 55–185. of sedimentation, and evolution, in Fassett, J.E., Scott, C.S., and Krause, D.W., 2006, Multituberculates and Rigby, J.K. Jr., eds.,The Cretaceous–Tertia- (Mammalia, Allotheria) from the earliest Tiﬀ a- ry boundary in the San Juan and Raton Basins: nian (late Paleocene) Douglass Quarry, eastern Geological Society of America Special Paper 209, Crazy Mountains Basin, Montana: Contributions p. 165–204. from the Museum of Paleontology, Ann Arbor, Sloan, R.E., and Van Valen, L., 1965, Cretaceous University of Michigan v. 31, no. 10, p. 211–243. mammals from Montana: Science v. 148, no.
43 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics 3667, p. 220–227, doi: https://doi.org/10.1126/ Survey, 99-1, p. 77–114. science.148.3667.220 Ullmann, P.V., Varricchio, D., and Knell, M.J., 2012, Smith, L.N., Hill, C.L., and Reiten, J., 2020, Qua- Taphonomy and taxonomy of a vertebrate micro- ternary and late Tertiary of Montana: Climate, site in the mid-Cretaceous (Albian–Cenomanian) glaciation, stratigraphy, and vertebrate fossils, in Blackleaf Formation, southwest Montana: Histor- Metesh, J.J., and Vuke, S.M., eds., Geology of ical Biology, v. 24, no. 3, p. 311–328, doi: https:// Montana—Geologic History: Montana Bureau of doi.org/10.1080/08912963.2011.602405 Mines and Geology Special Publication 122, v. 1, Van Valen, L., 1965, A middle Palaeocene Primate: 64 p. Nature, v. 207, p. 435–436. Sternberg, C.H., 1909, The Life of a fossil hunter: Van Valen, L., 1966, Deltatheridia, a new order of New York, H. Holt, 286 p. mammals: Bulletin of the American Museum of Sues, H.D., 1980, Anatomy and relationships of a Natural History, v. 132, 126 p. new hypsilophodontid dinosaur from the Lower Van Valen, L., 1967, New Paleocene insectivores Cretaceous of North America: Palaeontographica and insectivore classiﬁ cation: Bulletin of the Abteilung a Palaeozoologie-Stratigraphie, v. 169, American Museum of Natural History, v. 135, p. p. 51–72. 217–284. Sutton, J.F., and Genoways, H.H., 1974, A new ves- Van Valen, L.M., 1978, The beginning of the age of pertilionine bat from the Barstovian deposits of mammals: Evolutionary Theory, v. 4, p. 45–80. Montana: Lubbock, Texas Tech University Muse- um, Occasional Papers, no. 20, 8 p. Van Valen, L.M., and Sloan, R.E., 1965, The earliest primates: Science, v. 150, no. 3697, p. 743–745, Sutton, J.F., and Korth, W.W., 1995, Rodents (Mam- doi: https://doi.org/10.1126/science.150.3697.743 malia) from the Barstovian (Miocene) Anceney local fauna: Montana: Annals of the Carnegie Van Valen, L.M., 1994, The origin of the plesiadapid Museum, v. 64, p. 267–314. primates and the nature of Purgatorius: Evolution- ary Monographs, v. 15, p. 1–79. Tabrum, A.R., 2001, Tertiary paleontology of south- western Montana and adjacent Idaho, in Hill, Varricchio, D.J., 2001, Gut contents from a Cretaceous C.L., ed., Guidebook for the Field Trips, Society tyrannosaurid: Implications for theropod dinosaur of Vertebrate Paleontology 61st Annual Meeting: digestive tracts: Journal of Paleontology, v. 75, p. Bozeman, Museum of the Rockies, Occasional 401–406. Paper no. 3, p. 93–112. Varricchio, D.J., 2002, A new bird from the Upper Tabrum, A.R., and Metais, G., 2007, Pipestoneia Cretaceous Two Medicine Formation of Montana: douglassi, A new genus and species of seleno- Canadian Journal of Earth Sciences, v. 39, no. 1, dont artiodactyl from the Pipestone Springs area, p. 19–26, doi: https://doi.org/10.1139/e01-057 Jeﬀ erson County, Montana: Bulletin of the Car- Varricchio, D.J., and Chiappe, L.M., 1995, A New Enan- negie Museum of Natural History, Mammalian tiornithine bird from the Upper Cretaceous Two Paleontology on a Global Stage: Papers in Honor Medicine Formation of Montana: Journal of Ver- of Mary R. Dawson, v. 39, p. 83–96. tebrate Paleontology, v. 15, no. 1, p. 201–204, doi: Tschopp, E., Mateus, O.V., and Benson, R.B.J., 2015, https://doi.org/10.1080/02724634.1995.10011219 A specimen-level phylogenetic analysis and tax- Varricchio, D.J., Jackson, F.D., and Trueman, C.N., onomic revision of the Diplodocidae (Dinosauri- 1999, A nesting trace with eggs for the Cretaceous dae, Sauropoda): PeerJ, v. 3, 298 p., doi: https:// theropod dinosaur Troodon formosus: Journal of doi.org/10.7717/peerj.857 Vertebrate Paleontology, v. 19, no. 1, p. 91–100, Turner, C.E., and Peterson, F., 1999, Biostratigra- doi: https://doi.org/10.1080/02724634.1999.1001 phy of dinosaurs in the Upper Jurassic Morrison 1125 Formation of the Western Interior, U.S.A., in Varricchio, D.J., and Horner, J.R., 1993, Hadrosau- Gillette, D., ed., Vertebrate Paleontology in Utah: rid and lambeosaurid bone beds from the Upper Miscellaneous Publication of the Utah Geological Cretaceous Two Medicine Formation of Montana: 44 Horner and Hanson: Vertebrate Paleontology Taphonomic and biologic implications: Canadian g/10.1671/0272-4634(2002)022[0779:ANGOD- Journal of Earth Sciences, v. 30, no. 5, p. 997– P]2.0.CO;2 1006, doi: https://doi.org/10.1139/e93-083 Williamson, T.D., Brusatte, S.L., Carr, T.D., Weil, A., Varricchio, D.J., Horner, J.R., and Jackson, and Standhardt, B.R., 2012, The phylogeny and F.D., 2002, Embryos and eggs for the Cre- evolution of Cretaceous–Paleogene metatherians: taceous theropod dinosaur Troodon formo- Cladistic analysis and description of new early sus: Journal of Vertebrate Paleontology, Palaeocene specimens from the Nacimiento For- v. 22, no. 3, p. 564–576, doi: https://doi. mation, New Mexico: Journal of Systematic Pa- org/10.1671/0272-4634(2002)022[0564:E- laeontology, v. 10, no. 4, p. 625–651, doi: https:// AEFTC]2.0.CO;2 doi.org/10.1080/14772019.2011.631592 Varricchio, D.J., Martin, A.J., and Katsura, Y., 2007, Wilson, J.A., and Smith, M.B., 1996, New remains of First trace and body fossil evidence of a burrow- Amphicoelias Cope (Dinosauria: Sauropoda) from ing, denning dinosaur: Proceedings of the Royal the Upper Jurassic of Montana and diplodocoid Society B: Biological Sciences, v. 274, p. 1361– phylogeny: Journal of Vertebrate Paleontology, v. 1368. 16, p. 73A. Wang, X., Tedford, R.H., and Taylor, B.E., 1999, Wilson, G.P., Clemens, W.A., Horner, J.R., and Hart- Phylogenetic systematics of the Borophaginae man, J.H., eds., 2014, Through the end of the (Carnivora: Canidae): Bulletin of the American Cretaceous in the type locality of the Hell Creek Museum of Natural History, v. 243, 391 p. Formation in Montana and adjacent areas: Geo- Wang, X., Wideman, B.C., Nichols, R., and logical Society of America Special Paper 503, Hanneman, D.L., 2004, A new species of Aeluro- 392 p. don (Carnivora, Canidae) from the Barstovian Wilson, M.C., 2003, Pleistocene vertebrates from the of Montana: Journal of Vertebrate Paleontol- Doeden Local Fauna (Illinoian/Sangamonian?), ogy, v. 24, no. 2, p. 445–452, doi: https://doi. Yellowstone River Valley, eastern Montana: org/10.1671/2493 Geological Society of America, Abstracts with Whetstone, K.N., 1978, A new genus of cryptodiran Programs, v. 35, no. 5, p. 16. turtles (Testudinoidea, Chelydridae) from the Wood, A.E., 1931, Phylogeny of the heteromyid ro- Upper Cretaceous Hell Creek Formation of Mon- dents: American Museum Novitates, v. 501, 21 p. tana: Lawrence, University of Kansas Science Wood, A.E., 1933, A new heteromyid rodent from the Bulletin, v. 51, p. 539–563. Oligocene of Montana: Journal of Mammalogy, v. White, T.E., 1954, Preliminary analysis of the fossil 14, no. 2, p. 134–141. vertebrates of the Canyon Ferry Reservoir area: Wood, A.E., and Konizeski, R.L., 1965, A new euty- Proceedings of the United States National Muse- pomyid rodent from the Arikareean (Miocene) of um, v. 103, p. 395–438. Montana: Journal of Paleontology, v. 39, no. 3, p. Wilimovsky, N.J., 1956, Protoscaphirhynchus squa- 492–496. mosus, a new sturgeon from the Upper Cretaceous Woodruﬀ , D.C., 2012, A new titanosauriform from the of Montana: Journal of Paleontology, v. 30, no. 5, Early Cretaceous Cloverly Formation of Mon- p. 1205–1208. tana: Cretaceous Research, v. 36, p. 58–66, doi: Williams, L.A., 1983, Deposition of the Bear https://doi.org/10.1016/j.cretres.2012.02.003 Gulch Limestone: A Carboniferous platten- Woodruﬀ , D.C., and Foster, J.R., 2017, The ﬁ rst spec- kalk from central Montana: Sedimentolo- imen of Camarasaurus (Dinosauria: Sauropoda) gy v. 30, no. 6, p. 843–860, doi: https://doi. from Montana: The northernmost occurrence of org/10.1111/j.1365-3091.1983.tb00714.x the genus: PLoS ONE, v. 12, no. 5, 61 p., doi: Williamson, T.E., and Carr, T.D., 2003, A new genus https://doi.org/10.1371%2Fjournal.pone.0177423 of highly derived pachycephalosaurian from west- Woodruﬀ , D.C., Carr, T.D., Storrs, G., Waskov, K.A., ern North America: Journal of Vertebrate Paleon- Scannella, J.B., Norden, K.K., and Wilson, J.P., tology, v. 22, no. 4, p. 779–801, doi: https://doi.or 2018, The smallest Diplodocus skull: Ontoge- 45 MBMG Special Publication 122: Geology of Montana, vol. 2: Special Topics ny recapitulating phylogeny and growth-related dietary changes in the largest dinosaurs: Scientiﬁ c Reports, v. 8, 61 p., doi: https://doi.org/10.1038/ s41598-018-32620-x Woodward, H.N., Freedman Fowler, E.A., Farlow, J.O., and Horner, J.R., 2015, Maiasaura, a mod- el organism for extinct vertebrate population biology: A large sample statistical assessment of growth dynamics and survivorship: Paleobi- ology, v. 41, no. 4, p. 503–527, doi: https://doi. org/10.1017/pab.2015.19 Young, G.C., 2010, Placoderms (armored ﬁ sh): Dom- inant vertebrates of the Devonian Period: Annual Review of Earth and Planetary Sciences, v. 38, p. 523–550, doi: https://doi.org/10.1146/an- nurev-earth-040809-152507 Zack, S.P., Penkrot, T.A., Krause, D.W., and Maas, M.C., 2005, A new apheliscine “condylarth” mammal from the late Paleocene of Montana and Alberta and the phylogeny of “hyopsodontids”: Acta Palaeontologica Polonica, v. 50, no. 4, p. 809–830. Zidek, J., 1980, Acanthodes lundi, new species (Acan- thodii) and associated coprolites from uppermost Mississippian Heath Formation of central Mon- tana: Annals of the Carnegie Museum, v. 49, p. 49–78.