Cretaceous "Hell Creek Faunal Facies"; Late Maastrichtian

    Phillip Bigelow

    The Hell Creek Formation is a layer of rock that was deposited at the very end of the "age of dinosaurs". This layer's deposition spanned a period of roughly 2 million years, from 67 million years ago to 65 million years ago. The formation1 (see shaded area on map) is found in Montana, North Dakota and South Dakota. A rock layer of the same age is found further south, and goes by another name (The Lance Formation). In Canada, correlative rock layers are the Frenchman Formation, the Willow Creek Formation, and the Scollard Formation. All of these these units were deposited by ancient rivers that flowed eastward into a large inland SEA that ran from north-central Canada to the Gulf of Mexico. The rock layer that underlies the Hell Creek Formation is called the Fox Hills Formation, and the overlying layer is called the Tullock Formation (Paleocene). In the Dakotas, the overlying formation is called the Ludlow Formation. The famous K-T boundary, which separates the Cretaceous and Cenozoic, occurs as a discontinuous but distinct thin marker bed within the Hell Creek Formation near its top, giving the rock unit added scientific importance.
    Some people wonder what types of plants and animals lived along with the dinosaurs. The following lists show you a life community at a particular point in time, and at a particular place on earth. As you will see, the species that were present in the Hell Creek Formation were rich and diverse. And this list shows only what has been found to date! What new species are yet to be discovered?

    1 In this context, a "formation" does not mean a hill, cliff, peak, or knob, or any other landform. In geology, a "formation" is defined as a distinct layer of rock that is recognizable over a large geographic area, and which can be distinguished from other adjacent, underlying, or overlying rock formations by unique features, such as it's geologic age, color, composition, or grain size, to name but a few features.

    Table of Contents

    1. Insect evidence                                        Questions? Check out my FAQ
    2. Insect Ichnotaxa
    3. Aquatic Invertebrates
    4. Mammalia
    5. Lower Vertebrates
    6. Dinosauria
    7. Freshwater Algae
    8. Palynomorphs (fossil pollen and spores)
    9. Megaflora



    Insect Evidence From The Hell Creek Formation

    [from Johnson et al. (2000)]

    "Previous studies have indicated no evidence for mass extinction among insects at the K-T boundary. These studies were based on global, family-level compilations of body-fossil data that indicated no deviation from background rates of extinction. In contrast, the palynologic and megafloral evidence cited above demonstrates a major extinction of plant taxa at the K-T boundary. To test these opposite conclusions, we examined insect-mediated plant damage on 6,000 leaves in a succession of 78 of our megafloral localities in southwestern North Dakota from a section that spans a 2.0 m.y. interval of the late Maastrichtian Hell Creek Formation and earliest Puercan Ludlow Member of the Fort Union Formation. All characterizable leaf hosts from these floras were assigned to morphotypes and/or Linnean taxa, providing explicit recognition of plant hosts. We identified 42 types of insect damage, representing insect herbivory from four functional feeding groups: external foliage feeders, leaf miners, gallers, and piercer-and-suckers. For the Hell Creek megaflora, 41 types of damage were identified, including several conspicuous examples of galls and scales on primary veins, serpentine mines, and diagnostic slot-hole feeding, each occurring monospecifically and abundantly on separate species of Lauraceae, Platanacae, and Cannabacae. For the [overlying, Tertiary-age] Fort Union megaflora, only 17 types of damage were identified; abundance levels were found to be significantly lower; and the associations were more generalized, lacking host-specific associations. These data demonstrate that, at local scales, insect herbivory suffered dramatically during the terminal Cretaceous event, with no evidence of subsequent recovery. Levels of herbivore diversity remained depressed until pronounced vegetational shifts in the Western Interior of North America during the Early Cenozoic Thermal Maximum in the latest Paleocene to early Eocene time."

    Insect Ichnotaxa from the Hell Creek Formation

    LINNAEAN NAMECOMMENTS
    Cephaloleichnites strongi Wilf et. al, 2000A hispine beetle ("leaf beetle")

    References:

    Johnson K. R., D. Nichols, C. Labandeira, and D. Pearson. 2000. Devastation of terrestrial ecosystems at the K-T boundary in North America: The first calibrated record of plant and animal response to the Chicxulub impact. In Catastrophic Events and Mass Extinctions: Impacts and Beyond, Vienna, pp. 85-86, LPI Contribution No. 1053, Lunar and Planetary Institute, Houston.

    Wilf, P., C. C. Labandeira, W. J. Kress, C. L. Staines, D. M. Windsor, A. L. Allen, and K. R. Johnson. 2000. Timing the radiations of leaf beetles: Hispines on gingers from latest Cretaceous to Recent. Science 289:291-294.


    Aquatic Invertebrates from the Hell Creek Formation

    LINNAEAN NAMECOMMENTS
    Plesielliptio postbiplicatus (Whitfield)Fresh water Pelecypod (fwp)
    Plesielliptio gibbosoides (Whitfield)fwp
    Plesielliptio whitfieldi Russell 1976fwp
    Rhabdotophorus aldrichi (White)fwp
    Pleurobema cryptorhynchus (White)fwp
    Plethobasus aesopiformis (Whitfield)fwp
    Plethobasus biesopoides (Whitfield)fwp
    Quadrula cylindricoides (Whitfield)fwp
    Proparreysia verrucosiformis (Whitfield)fwp
    Proparreysia holmesiana (White)fwp
    Proparreysia barnumi (Pilsbry)fwp
    Proparreysia percorrugata (Whitfield)fwp
    Proparreysia pyramidatoides (Whitfield)fwp
    Proparreysia letsoni (Whitfield)fwp
    Proparreysia retusoides (Whitfield)fwp
    Proparreysia corbiculoides (Whitfield)fwp
    Proparreysia paucinodosa Russell 1976fwp
    Obovaria? pyramidella (Whitfield)fwp
    Corbicula cf. subelliptica (Meek and Hayden)fwp
    Sphaerium beckmani Russell 1976fwp. "Pill clam". "Nut clam". "Fingernail clam". "Pea clam". Family Sphaeriidae.
    Pleiodon gen. (sub. gen. Pleiodon) Conrad 1834fwp
    Campeloma sp.Fresh water snail. See Cooley (2001), below. (Genus is misspelled in the abstract)
    Anomia gryphorhyncha Meek. HYPOTYPE. YPM 24103; other specimen YPM-45828Bivalve. Family Anomiidae. From a marine facies ("tongue") in South Dakota.
    Corbicula sp. A. YPM 45892From a marine facies ("tongue") in South Dakota. Modern members of this genus live in fresh water
    Crassostrea subtrigonalis (Evans & Shumard). YPM 45875.Oyster. Family Ostreidae. Collected from a marine facies ("tongue") in South Dakota.
    Granocardium (Ethmocardium) whitei (Dall). YPM 46205.Bivalve. Family Cardiidae. Collected from a marine facies ("tongue") in South Dakota.
    Hiatella? sp. A. HYPOTYPE. YPM 24688.Bivalve. Present members of this genus are rock borers. Collected from a marine facies ("tongue") in South Dakota.
    Leptosolen sp. indet. HYPOTYPE. YPM 24746.Bivalve. Family Cultellidae. Collected from a marine facies ("tongue") in South Dakota.
    Sphenodiscus lenticularis (Owen). YPM 44661Ammonite. From a marine facies ("tongue") in South Dakota.
    Discoscaphites rossi Landman & Waage. YPM 27082.Microconch of an ammonite. From a marine facies ("tongue") in South Dakota.
    undet. Scaphitidae. YPM 32430Ammonite. From a marine facies ("tongue") in South Dakota. Other attributes: specimen has hooks on it's shell.

    Comments:
    All "Bug Creek Faunal Facies" taxa are excluded, due to an almost certain mixing of Cretaceous and Paleocene taxa.

    Russel (1976:366) claims that "Gastropods, some of which were identified but not described by Whitfield, are represented in the collection by enough material to show that a large and varied assemblage is present in the Hell Creek beds." If I can find a published source, I will add these fresh water gastropods to this list.

    Regarding the survival of these pelecypods into the Paleocene, Russel (p. 367) stated: "...none has been shown as yet to occur in Paleocene strata".

    Regarding the uniqueness of the Hell Creek Formation pelecypods, Russel (p. 367) wrote: "The largest number of Hell Creek species occurring in other faunas is in the Lance Formation, although the number is only five or six." (see also Morris, 1990).

    Does this indicate freshwater molluscan provincialism in the North American interior during the latest Cretaceous?

    All of the marine invertebrates were collected in South Dakota (Ziebach County) from the lower part of the Hell Creek Formation in 1961-1962 by K.M. Waage. These specimens were collected from the Breien Member of the formation. "YPM" is the acronym for a Yale-Peabody Museum specimen number.

    References:

    1. Cooley, J. B. 2001. Taphonomy and sedimentology of a tyrannosaurid locality from the late Cretaceous (Maastrichtian) Hell Creek Formation of eastern Montana. [Abstract]. Session no. 82. Geological Society of America Abstracts with Programs. Geological Society of America Annual Meeting , November 5-8, 2001, Boston, Massachusetts.
    2. Morris, P.J. 1990. Diversity and extinction: Detailed examination of freshwater molluscan faunas in an African Rift lake and at the K-T boundary. Geological Society of America Abstracts with Programs 22(7): A356.
    3. Morris, P.J., and P.G. Williamson, 1988. Pleiodon (Conrad) (Bivalvia: Mutelidae: Pleiodoninae) from the late Cretaceous of Montana: A First North American Record for the Mutelidae. Journal of Paleontology, v.62, no. 5, pp.758-765.
    4. Russell, L. S. 1976. Pelecypods of the Hell Creek Formation (Uppermost Cretaceous) of Garfield County, Montana. Canadian Journal of Earth Science, vol. 13, pp. 365-388.
    5. Whitfield, R. P. 1903. Notice of six new species of Unios from the Laramie group. Bulletin of the American Museum of Natural History, vol. 19(15), pp. 483-487.
    6. Whitfield, R. P. 1907. Remarks on and descriptions of new fossil Unionidae from the Laramie clays of Montana. Bulletin of the American Museum of Natural History, vol. 23(26), pp. 623-628.


    Mammalia from the Hell Creek Formation

    LINNAEAN NAMECOMMENTS
    Mesodma hensleighi Lillegraven 1969A multituberculate
    Mesodma formosa (Marsh, 1889)A multituberculate
    Mesodma thompsoni Clemens 1964A multituberculate
    ?Neoplagiaulax burgessi Archibald 1982A multituberculate
    ?Neoplagiaulacidae gen. et sp. indetA multituberculate
    Cimolodon nitidus Marsh 1889A multituberculate
    Cimolomys gracilisA multituberculate
    Meniscoessus robustus Marsh 1989A multituberculate
    Essonodon browni Simpson 1927A multituberculate
    Cimexomys minor Sloan and Van Valen 1965A multituberculate
    Paracimexomys priscus Archibald 1982A multituberculate
    Ectonodon montanensis Simpson 1927TYPE.-Amer. Mus. No. FM14406, an isolated left upper molar from Crooked Creek. A metatherian. The genus was reassigned as a junior synonym of Didelphodon (by McKenna & Bell, 1997). The current status of the species is not clear. In the mid-1990s, the museum reported the specimen lost.
    Alphadon marshi Simpson 1927A metatherian
    Alphadon wilsoni Lillegraven 1969A metatherian
    Alphadon lulli Clemens 1966A metatherian
    Alphadon rhaister Clemens 1966A metatherian
    Glasbius twitchelli Archibald 1982A metatherian
    Pediomys elegans Marsh 1889A metatherian
    Pediomys cooki Clemens 1966A metatherian
    Pediomys krejcii Clemens 1966A metatherian
    Pediomys hatcheri (Osborn 1898)A metatherian
    Pediomys florencae Clemens 1966A metatherian
    ?Pediomys cf. P. florencae Clemens 1966A metatherian
    Didelphodon vorax Marsh 1889A BADGER-SIZE metatherian! One of the larger Mesozoic mammals
    Gypsonictops hypoconusA eutherian
    Gypsonictops illuminatusA eutherian
    Cimolestes incisus Marsh 1889A eutherian
    Cimolestes cerberoides Lillegraven 1969A eutherian
    Cimolestes propalaeoryctes Lillegraven 1969A eutherian
    Cimolestes stirtoni Clemens 1973A eutherian
    Cimolestes magnus Clemens and Russell 1965A eutherian
    Batodon tenuis Marsh 1892A eutherian
    Purgatorius ceratops Van Valen and Sloan 1965Formerly considered to be a Primatomorph (Van Valen and Sloan, 1965), it may actually be in a sister group to Placentalia (Wible et al., 2007).

    Comments:

    Although Archibald (1982) listed many marsupials in the Hell Creek Formation, a new character trait analysis by Rougier et. al (1998) shows that all of Archibald's "marsupials" are in fact members of a more inclusive clade called Metatheria. Amazingly, this new study also indicates that no true marsupials have yet been found from the Mesozoic.

    All "Bug Creek Faunal Facies" taxa excluded, due to an almost certain mixing of Cretaceous and Paleocene taxa (Lofgren et al., 1990; Lofgren, 1995).

    References:

    1. Archibald, J. D. 1982. A study of Mammalia and Geology across the Cretaceous-Tertiary Boundary in Garfield County, Montana. University of California Publications in Geological Sciences, volume 122, pages 242-243.
    2. Lillegraven, J. A., Z. Kielan-Jaworowska, and W. A. Clemens (eds.). 1979. Mesozoic Mammals: The First Two-Thirds of Mammalian History. University of California Press. 311 pages.
    3. Lofgren, D. L. 1995. The Bug Creek Problem and the Cretaceous-Tertiary Transition at McGuire Creek, Montana. University Of California Publications In Geological Sciences 140: 1-185.
    4. Lofgren, D.L., C.L. Hotton, and A.D. Runkel. 1990. Reworking of Cretaceous dinosaurs into Paleocene channel deposits, upper Hell Creek Formation, Montana. Geology 18: 874-877.
    5. Rougier, G.W., J.R. Wible, and M.J. Novacek. 1998. Implications of Deltatheridium specimens for early marsupial history. Nature, volume 396, pages 459-463.
    6. Simpson GG. 1927. Multis, metatherians and Gypsonictops, Mammalian fauna of the Hell Creek Formation of Montana. American Museum Novitates 267:1-7.
    7. Van Valen, L., and R. E. Sloan. 1965. The earliest primates. Science, volume 150, pages 743-745.
    8. Wible, J. R., G. W. Rougier, M. J. Novacek, and R. J. Asher. 2007. Cretaceous eutherians and Laurasian origin for placental mammals near the K/T boundary. Nature 447:1003-1006.
    9. Wilson, G. P. 2005. Mammalian faunal dynamics during the last 1.8 million years of the Cretaceous in Garfield County, Montana. Journal of Mammalian Evolution 12, Nos. 1 and 2.


    Lower Vertebrates from the Hell Creek Formation

    LINNAEAN NAMEVERNACULAR NAME and COMMENTS
    Lissodus selachos (Estes) 1964Hybodontid shark
    Squatirhina americana Estes 1964Orectolobid shark
    Brachaelurus estesi (Herman) 1975Orectolobid shark (rare)
    Ischyrhiza avonicola Estes 1964sawfish (extremely rare)
    Myledaphus bipartitus Cope 1876ray (relatively common)
    "Acipenser" eruciferus (Cope) 1876sturgeon
    "Acipenser" albertensis Lambe 1902sturgeon
    Protoscaphirhynchus squamosus Wilmovsky 1956sturgeon
    Paleopsephurus wilsoni MacAlpin 1947Paddlefish (Polydontid, see Grande and Bemis, 1991)
    Large, undescribed PolyodontidaePaddlefish (Polydontid, see Grande and Bemis, 1991)
    Melvius thomasi Bryant 1987a large amiid fish (family that includes the modern Bowfin)
    Kindleia fragosa Jordan 1927small amiid fish (ubiquitous). Closely related to the modern Bowfin
    Lepisosteus occidentalis (Leidy) 1856garfish ("gar pike") (extremely common)
    Belonostomus longirostris (Lambe) 1902A long-snouted slender fish (affinity= ?Aspidorhynchidae). Rare
    Belonostomus sp.see above
    Phyllodus paulkatoi Estes and Hiatt 1978fish with columnar teeth
    Palaeolabrus montanensis Estes 1969fish (incertae sedis)
    Platacodon nanus Marsh 1889small teleost fish
    Pachyrhizodontoidei indet.fish
    Albanerpeton nexuosus Estes 1981salamander
    Opisthotriton kayi Auffenberg 1961salamander
    Prodesmodon copei Estes 1964salamander (extremely rare)
    Scapherpeton tectum Cope 1876salamander (most common salamander.)
    Lisserpeton bairdi Estes 1965salamander
    cf. Piceoerpeton sp.salamander
    Habrosaurus dilatus Gilmore 1928LARGE salamander (160 cm long)
    Scotiophryne pustulosa Estes 1969small frog
    Plesiobaena antiqua Lambe 1902Baenid turtle
    Eubaena cephalica (Hay) 1904Baenid turtle
    Stygiochelys estesi Gaffney and Hiatt 1971Baenid turtle
    Palatobaena bairdi Gaffney 1972Baenid turtle
    Neurankylus eximius Lambe 1902Largest baenid turtle in Hell Cr. Formation
    Thescelus insiliens Hay 1908 Baenid turtle
    Emarginochelys cretacea Whetstone 1978Chelydrid-like turtle
    Chelydridae indet.Chelydrid-like turtle
    "Clemmys" backmani Russell 1934Thin-shelled macrobaenid turtle
    Adocus sp.Flattened dermatemydid turtle
    Basilemys sinuosa Riggs 1906BIG dermatemydid land tortoise! 1+ meters long
    Dermatemydine indet.Dermatemydid turtle
    Kinosternidae?Small kinosternid turtle
    Trionyx (Trionyx)Similar in appearance to living trionychid turtle
    Trionyx (Aspideretes)Large trionychid turtle
    "Plastomenus" ATrionychid turtle
    "Plastomenus" CTrionychid turtle
    Helopanoplia distincta Hay 1908 Trionychid turtle
    Aspideretoides foveatus Gardiner et al. 1995Trionychid turtle
    Compsemys victa Leidy 1856Baenid? turtle
    Champsosaurus sp. indet.Long-snouted aquatic diapsid (Suborder Choristodera)
    Haptosphenus placodon Estes 1964Teiid lizard
    Leptochamops denticulatus (Gilmore) 1928Small teiid lizard
    Peneteius aquilonius Estes 1969Teiid lizard
    Chamops segnis Marsh 1892Largest teiid lizard in Hell Creek Formation
    Contogenys sloani Estes 1969?Scincid? lizard
    Exostinus lancensis Cope 1873Xenosaurid lizard
    Odaxosaurus piger Gilmore 1928Anguid lizard
    Proxestops jepseni (Gilmore) 1942Anguid lizard
    Parasaniwa wyomingensis Gilmore 1928Necrosaurid lizard
    Paraderma bogerti Estes 1964?Helodermatid? lizard
    Palaeosaniwa canadensis Gilmore 1928A LARGE Monstersauria lizard (Balsai, 2001), closely related today's varanid lizards. It was the largest lizard in the Hell Cr. Fm, and Balsai has even suggested that it may have been venomous. We're talking MONITOR lizard-size!
    Boidae indet.Snake. Earliest-known boid. See Bryant (1989:49, 76)
    Borealosuchus sternbergi (Gilmore 1910); = "Leidyosuchus" sternbergi Gilmore Crocodyloid; See Brochu (1997)
    Brachychampsa montana Gilmore 1911Alligatoroid; possibly a turtle-eater (see Carpenter and Lindsey, 1980 ref., below).
    "Undescribed alligatorine A"Alligatoroid
    "Undescribed alligatorine B"Alligatoroid
    Thoracosaurus neocesariensis(DeKay) 1842 Marine crocodyloid. Extant marine crocs are sometimes found in rivers. This occurrence is reported within the terrestrial Hell Creek Formation by Estes and Berberian (1970). See ref. below.
    Pterosauria gen. et sp. indet.These records of pterosaur remains from the Hell Creek Formation are two indeterminate specimens, which have been recorded from North Dakota but not described (Johnson et al., 2000; Pearson et al., 2002). See Johnson et al. and Pearson et al. references, below
    Pterosauria (azhdarchid) Another pterosaur. See Henderson and Peterson (2006) reference, below

    Comments:
    The following may be Paleocene in age. Stratigraphic position highly dubious. Included for historical context. It is best to exclude the taxon from the "Hell Creek Faunal Facies":
    **Coriops amnicolus Estes 1969, fish. May be Paleocene in age.
    **Proamphiuma cretacea Estes 1969, eel-like salamander. May be Paleocene in age.
    **Colpodontosaurus crascens Estes 1964, Necrosaurid lizard. May be Paleocene in age.

    All "Bug Creek Faunal Facies" taxa excluded, due to an almost certain mixing of Cretaceous and Paleocene taxa (Lofgren et al., 1990; Lofgren, 1995).

    References:

    1. Balsai, M. J. 2001. The phylogenetic position of Palaeosaniwa and the early evolution of the Platynotan (Varanoid) anguimorphs. Unpublished PhD dissertation. University of Pennsylvania.
    2. Brochu, C. 1997. A review of "Leidyosuchus" from the Cretaceous through Eocene of North America. Journal of Vertebrate Paleontology 17[4]:679-697.
    3. Bryant, L.J. 1989. Non-dinosaurian lower vertebrates across the Cretaceous-Tertiary Boundary in Northeastern Montana. University of California Publications in Geological Sciences volume 134. University of California Press, 107 pages.
    4. Carpenter, K., and D. Lindsey. 1980. The dentiary of Brachychampsa montana Gilmore (Alligatorinae; Crocodylidae), a late Cretaceous turtle-eating alligator. Journal of Paleontology, vol. 54(6):1213-1217.
    5. Estes, R., and P. Berberian. 1970. Paleoecology of a late Cretaceous vertebrate community from Montana. Breviora volume 343, 35 pages.
    6. Gardner, James D., Anthony P. Russell, and Donald B. Brinkman. 1995. Systematics and taxonomy of the soft-shelled turtles (Family Trionychidae) from the Judith River Group (mid-Campanian) of North America. Canadian Journal of Earth Sciences 32: 631-643.
    7. Grande, L. and W. E. Bemis. 1991. Osteology and phylogenetic relationships of fossil and Recent paddlefishes (Polydontidae) with comments on the interrelationships of Acipenseriformes. Journal of Vertebrate Paleontology, vol. 11, supplement to number 1, 121 pages.
    8. Henderson, M. D. & J. E. Peterson. 2006. An azhdarchid pterosaur cervical vertebra from the Hell Creek Formation (Maastrichtian) of southeastern Montana. Journal of Vertebrate Paleontology 26(1):192-195.
    9. Hutchison, J. H., and J. D. Archibald. 1986. Diversity of turtles across the Cretaceous/Tertiary Boundary in Northeastern Montana. Palaeogeography, Palaeoclimatology, Palaeoecology 55:1-22.
    10. Johnson K. R., D. Nichols, C. Labandeira, and D. Pearson. 2000. Devastation of terrestrial ecosystems at the K-T boundary in North America: The first calibrated record of plant and animal response to the Chicxulub impact. In Catastrophic Events and Mass Extinctions: Impacts and Beyond, Vienna, pp. 85-86, LPI Contribution No. 1053, Lunar and Planetary Institute, Houston.
    11. Lofgren, D. L. 1995. The Bug Creek Problem and the Cretaceous-Tertiary Transition at McGuire Creek, Montana. University Of California Publications In Geological Sciences 140: 1-185.
    12. Lofgren, D.L., C.L. Hotton, and A.D. Runkel. 1990. Reworking of Cretaceous dinosaurs into Paleocene channel deposits, upper Hell Creek Formation, Montana. Geology 18: 874-877.
    13. Pearson, D., A. T. Schaefer, K. R. Johnson, D. J. Nichols, and J. P. Hunter. 2002. Vertebrate biostratigraphy of the Hell Creek Formation in southwestern North Dakota and northwestern South Dakota; pp. 145-167 in J. H. Hartman, K. R. Johnson, and D. J. Nichols (eds.), The Hell Creek Formation and the Cretaceous-Tertiary boundary in the northern great plains: an integrated continental record of the end of the Cretaceous. Geological Society of America Special Paper 361.


    Dinosauria from the Hell Creek Formation

    LINNAEAN NAMECOMMENTS
    Avisaurus archibaldi Brett-Surman and Paul 1985An enantiornithine bird
    Mononykinae incertae sedis (Hutchinson and Chiappe, 1998)"The Montanan mononykine". A theropod closely related to, and of overall similarity to, the feathered Asian genus Mononykus
    Aublysodon mirandus = ?StygivenatorTheropod (a tooth taxon)
    Aublysodon molnari = ?StygivenatorTheropod (aka, "The Jordan Theropod")
    Tyrannosaurus rex Osborn 1905 (?= Nanotyrannus lancensis Bakker, Williams and Currie, 1988) (= Albertosaurus megagracilis Paul 1988)Possibly the most massive theropod that ever lived. Thom Carr (1999) believes that Nanotyrannus is a juvenile T. rex.
    Ricardoestesia gen. Currie, Rigby and Sloan 1990:117Theropod (a tooth/jaw taxon; note spelling***)
    Ornithomimus sp.Theropod
    Ornithomimid indet.Theropod
    ?Chirostenotes sp. (=?Caenagnathus)A theropod closely related to the Asian genus Oviraptor
    Troodon formosus Leidy 1856Theropod
    Troodon indet.Theropod
    Dromaeosaurus sp.Theropod
    ?Velociraptor sp.Theropod
    Dromaeosaurid indet.#1Theropod
    Dromaeosaurid indet. #2Theropod
    ?Thescelosaurus garbanii Morris, 1976 (=Bugenasaura infernalis? Galton, 1995)Ornithischian (up to 12-16 feet long)
    ?Thescelosaurus sp.Ornithischian
    Edmontosaurus regalisHadrosaur ornithischian
    Edmontosaurus annectens (= "Anatosaurus" annectens) (= "Trachodon")Hadrosaur ornithischian
    Anatotitan copei (= "Anatosaurus" copei) (="Trachodon")Hadrosaur ornithischian
    ?Parasaurolophus walkeriHadrosaur ornithischian
    Dracorex hogwartsia Bakker et al., 2006"Bonehead" ornithischian. (See Bakker et al., 2006, below). May actually be an adolescent Pachycepalosaurus or Stygimoloch.
    Pachycephalosaurus wyomingensis"Bonehead" ornithischian
    Stegoceras edmontonense"Bonehead" ornithischian
    Stegoceras sp."Bonehead" ornithischian
    Stygimoloch spinifer (= Stenotholus kohleri)"Bonehead" ornithischian
    Paronychodon lacustris Cope, 1876 (nomen dubium)A dubious tooth taxon. May be teeth from the theropod genus Ricardoestesia (Currie et al., 1990; Sankey, 2003)
    Ankylosaurus indet.Ankylosaur ornithischian
    Ankylosaurus magniventrisAnkylosaur ornithischian
    Ankylosaurid indet.Ankylosaur ornithischian
    ?Edmontonia sp.Nodosaur ankylosaurian
    Triceratops horridus Marsh, 1889 (including Torosaurus)Ceratopsian ornithischian. New research (Scannella and Horner, 2010) suggests that Torosaurus latus Marsh 1891 is actually the adult growth stage of Triceratops, meaning that Torosaurus is a junior synonym of Triceratops
    Eggshell fragments (Dinosauria)Jepsen G.L. 1931. Dinosaur egg shell fragments from Montana. Science 73(1879): 12-13. See also Horner, J. and Gorman. p. 195. Digging Dinosaurs. Workman Press.


    AN ESTIMATION OF THE VARIOUS HELL CREEK FORMATION DINOSAUR POPULATIONS

    A paleo-population study is one of the most difficult of analyses to conduct in field paleontology. Here is the most recent estimate of the proportions of the eight most common dinosaurian families in the Hell Creek Formation, based on detailed field studies by White, Fastovsky and Sheehan (1998).

    •Ceratopsidae 61%
    •Hadrosauridae 23%
    •Ornithomimidae 5%
    •Tyrannosauridae 4%
    •Hypsilophodontidae 3%
    •Dromaeosauridae 2% (represented only by teeth)
    •Pachycephalosauridae 1%
    •Troodontidae 1% (represented only by teeth)

    Comments:
    Troodon formosus is also found in the Two Medicine Formation (72 million years old at it's top). If T. formosus is also found in the Hell Creek Formation (~65-67 million years old), then this theropod species has a very long temporal range. It is quite possible that the Hell Creek Troodon material (teeth) will turn out to be from new species. This idea was first proposed by Currie et al. (1990).

    *** Ricardoestesia was originally misspelled by the typesetter as Richardoestesia in the Currie et al. (1990) paper. George Olshevsky (1992), as first revisor, published the corrected spelling in his serial publication Mesozoic Meanderings #2 (2nd Printing).

    References:

    1. Various authors, 1990. Dinosaur Distributions, p. 117-118, IN Weishampel, D. B., P. Dodson, and H. Osmolska (eds.).1990. The Dinosauria. University of California Press, Berkeley.
    2. Bakker, R. T., R. M. Sullivan, V. Porter, P. Larson, and S. J. Salsbury. 2006. Dracorex hogwartsia, n. gen., n. sp., a spiked, flat-headed pachycephalosaurid dinosaur from the Upper Cretaceous Hell Creek Formation of South Dakota. in Lucas, S. G. and Sullivan, R. M., eds., Late Cretaceous vertebrates from the Western Interior. New Mexico Museum of Natural History and Science Bulletin 35, p. 331345.
    3. Carr, T. D. 1999. Craniofacial ontogeny in Tyrannosauridae (Dinosauria, Coelurosauria). Journal of Vertebrate Paleontology 19(3): 497-520.
    4. Currie, P. J., J. K. Rigby, Jr., and R. E. Sloan. 1990. Theropod teeth from the Judith River Formation of southern Alberta, Canada, IN Carpenter, K., and P.J. Currie (eds.). Dinosaur Systematics: Perspectives and Approaches. Cambridge University Press. (information on the Hell Creek Fm. occurrence on page 117).
    5. Galton, P.M. 1995. The species of the basal hypsilophodontid dinosaur Thescelosaurus Gilmore (Ornithischia; Ornithopoda) from the Late Cretaceous of North America. Neues Jahrbuch fuer Geologie und Palaeontologie. Abhandlungen, vol. 198(3):297-311.
    6. Holtz, T. 1997. Internet Usenet post to sci.bio.paleontology on 4/29/1997. (regarding status of Aublysodon).
    7. Hutchinson, J.R., and Chiappe, L.M. 1998. The first known Alvarezsaurid (Theropoda: Aves) from North America. Journal of Vertebrate Paleontology 18(3):447-450.
    8. Olshevsky, G. 1997. Whatever happened to Trachodon?. Jeff's Journal of Dinosaur Paleontology: http://www.dinosauria.com/jdp/misc/trachodon.html (regarding taxonomic status of "Anatosaurus")
    9. Sankey, J.T. 2003. New theropod and bird teeth from the Late Cretaceous (Maastrichtian) Hell Creek and Lance Formations. Society of Vertebrate Paleontology Annual Meeting, Journal of Vertebrate Paleontology Abstracts of Papers 23(3):93A.
    10. Scannella, J. B., and Horner, J. R., 2010. Torosaurus Marsh, 1891, is Triceratops Marsh, 1889 (Ceratopsidae: Chasmosaurinae): synonymy through ontogeny. Journal of Vertebrate Paleontology 30(4):1157 - 1168.
    11. Sues, H-D. 1997. On Chirostenotes, a Late Cretaceous oviraptorosaur (Dinosauria: Theropoda) from western North America. Journal of Vertebrate Paleontology 17(4): 698-716.
    12. White, P.D., D.E. Fastovsky, and P.M. Sheehan. 1998. Taphonomy and suggested structure of the dinosaurian assemblage of the Hell Creek Formation (Maastrichtian), eastern Montana and western North Dakota. Palaios, volume 13:41-51.


    Fresh Water Algae from the Hell Creek Formation

    LINNAEAN NAMECOMMENTS
    Sphaerochara brewsterensis-
    Tectochara sp.-

    Reference:

    1. Chiment, J. 1985. Late Cretaceous and early Tertiary charophyte floras from Garfield Co., Montana. American Association for the Advancement of Science (AAAS) Annual Meeting, Program with Abstracts, New York.


    Palynomorphs (fossil pollen and spores) from the Hell Creek Formation

    LINNAEAN NAMECOMMENTS
    Alnipollenites-
    Aquilapollenites"Several species, many specimens". Bohor et al. (1984)
    Aquilapollenites attenuatusPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Aquilapollenites collarisPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Aquilapollenites conatusPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Aquilapollenites delicatusPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Aquilapollenites marmarthensisPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Aquilapollenites quadricretaeusPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Aquilapollenites quadrilobusPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Aquilapollenites reductusPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Aquilapollenites senonicusPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Aquilapollenites turbidusPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Balmeisporites-
    Cranwellia rumseyensisPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Cranwellia striata-
    Cranwellia striatellipollisPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Gunnera microreticulata-
    Kurtzipites Anderson 1960 Misspelled as "Kurzlpites" by Smit and Van der Kaars (1983, figure 2)
    Libopollis jarzeniiPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Leptopecopites pocockiiPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Liliacidites spp.Rigby, Jr. et al. 1987
    Liliacidites complexusPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Marsypiletes cretaceusPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Myrtipites scabratusPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Orbiculapollis lucidusPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Pandaniidites-
    Proteacidites spp.Pearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001. (Misspelled as "Proteaccidites" in Bohr et al. (1984)).
    Racemonocolpites formosusPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Retibrevicolporites beccusPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Striatellipollis striatellusPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Styxpollenites calamitasPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Tricolpites microreticulatusPearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001
    Tricolpites parvistriatus-
    Ulmipollenites-
    Wodehouseia spinata-

    References:

    1. Bohor et al. 1984. Mineralogic evidence for an impact event at the Cretaceous-Tertiary Boundary. Science 224: 867-869.
    2. Nichols, D.J., D.M. Jarzen, C.J. Orth, and P.Q. Oliver. 1986. Palynological and iridium anomalies at Cretaceous-Tertiary boundary, south-central Saskatchewan: Science 231:714-717.
    3. Pearson, D. A., T. Schaefer, K. R. Johnson, and D. J. Nichols. 2001. Palynologically calibrated vertebrate record from North Dakota consistent with abrupt dinosaur extinction at the Cretaceous-Tertiary boundary. Geology 29, No. 1: 39-42.
    4. Rigby, Jr. et al. 1987. Dinosaurs from the Paleocene part of the Hell Creek Formation, McCone County, Montana. Palaios 2: 296-302.
    5. Smit and Van Der Kaars. 1983. Terminal Cretaceous Extinctions in the Hell Creek area, Montana: compatible with catastrophic extinction. Science 223:1177-1179.


    Mega Flora from the Hell Creek Formation

    Overview (from Johnson, 1997):
    190 plant morphotypes, including:

    1 bryophyte (mosses and liverworts)

    6 "pteridophytes" (A paraphyletic group: modern examples are horsetails, club mosses and ferns.)

    1 ginkgo (uncommon)
    Ginkgo adiantoides

    1 cycadophyte (cycads; uncommon)
    Nilssonia yukonensis Hollick

    9 conifers
    •Taxodiaceae (family that contains today's Bald Cypress)
    •Araucariaceae (family that contains today's Monkey Puzzle Tree and Norfolk Island Pine)
    •Cheirolepidiaceae (very widespread Mesozoic conifer group. All members are extinct)

    172 angiosperms (90% of all specimens collected, as well as 90% of all taxa found)
    •Lauraceae (Laurel family)
    •Platanaceae (family includes today's American sycamore or plane tree)
    •Magnoliaceae (Magnolia family)
    •Berberidaceae (Barberry family)
    •Arecaceae (palms)


    LINNAEAN NAMECOMMENTS
    **Annona? robustaAbundant at Brownie Butte, MT
    "Artocarpus" lessigiana (Lesquereux) Knowlton. TYPE. YPM-6310; YPM-6428-
    **"Celastrus" taurenensis Ward. TYPE. YPM 6223-6224Some may be Eucommiacaea. A mixed taxonomic bag?
    "Cinnamomum" lineafolia Knowlton. TYPE. YPM-6220Included in "Ficus" affinis by L. Hickey. Belongs in Rhamnaceae (modern Buckthorns and Ceanothus). Some other specimens referred to Cinnamomum sezanensis(?) sp.), a real cinnamon bush
    ** "Cissus" marginata (Lesquereux) Brown. TYPE. YPM-6125; other specimens YPM 6380-6381; YPM-6433Also spelled "marginatus". Common flora at Brownie Butte, MT.
    ** "Dryophyllum" subfalcatum Lesquereux. TYPE. YPM-6170; other specimens YPM 6384-6385; YPM 6382-6383One of the most common plant taxa in the Hell Creek and Lance Formations. Common at Brownie Butte, MT. If it is close to real Dryophyllum then it is a beech/chestnut-like tree (Fagaceae). It may also be a walnut-like tree (Juglandaceae)
    "Dryophyllum" tenneseensis. TYPE. YPM-6167; other specimens YPM 6356-6357see above
    **"Ficus" sp.-
    "Ficus" artocarpoides Lesquereux. TYPE. YPM-6212; other specimens YPM 6440-6441; YPM-6388; YPM-6389AThese fossil "figs" have been determined to be probable equisitalean root tubers
    "Ficus" planicostata Lesquereux. TYPE. YPM-6128; other specimen YPM-6353Synonymous with "Ficus" affinis. Probably in the Rhamnaceae (Buckthorn family)
    **"Ficus trinervisPart of the "Ficus" affinis complex
    **"Juglans" leconteana -
    Leepierceia preartocarpoides (Brown) Johnson, gen. et comb. nov. Johnson, 1996. Incertae sedis. Probably in the Platanaceae: Hamamelididae. A common broad-leaf angiosperm. (see also Johnson and Stucky, 1995)
    Liriodendrites bradacci Johnson, gen. et spec. nov.(Johnson, 1996. In the Magnoliidae: a common taxon)
    "Liriodendron" laramiense Ward. TYPE. YPM-6297; other specimens YPM 6358-6362 May be related to today's tulip tree (yellow poplar)
    Liriodendron? YPM 7583-7585 May be related to today's tulip tree (yellow poplar)
    Marmarthia pearsonii Johnson, gen. et spec. nov. (Johnson, 1996. In the Lauraceae: a common taxon)
    Marmarthia trivialis (Lesquereux) Johnson, gen. et comb. nov. (Johnson, 1996. In the Lauraceae: a common taxon)
    Platanites marginata (Lesquereux) Johnson, comb. nov. Johnson, 1996. In the Platanaceae: Hamamelididae. A common taxon
    "Quercus" viburnifolia Lesquereux. TYPE. YPM-6226 Included within "Cissus" marginata. May be in the Platanaceae (American sycamore or plane tree)
    "Rhamnus" cleburnii Lesquereux. TYPES. YPM 6183-6184; other specimens YPM-6390; YPM-6442A Buckthorn look-alike.
    "Vitis" stantonii (Knowlton) Brown. TYPE. YPM-6138; other specimens YPM-7042; YPM 6349-6351This could be a real Vitus (a real grape)
    **"Viburnum" sp.-
    "Ziziphus" fibrillosus YPM-6305-
    Androvettia catenulata Bell. TYPE. YPM-6267; other speciemens YPM 6386-6387-
    Araliaephyllum polevoi (Kryshtofovich) Krassilov. TYPE. YPM 6179-6182-
    Berberidaceae. TYPE. YPM-6320Today's Barberry is a member of this family
    Bisonia niemii Johnson, gen. et spec. nov.Incertae sedis. Johnson, 1996. A broad leaf, probably in the Laurales. A common taxon. Type specimen was found near a T. rex skeleton in S. Dakota (the "Sue" site)
    ?Cannabaceae. TYPES. YPM 6203-6205; Other specimen YPM-6363AThe family that includes marijuana!
    Carpites ulmiformis Dorf. YPM-6172-
    Chloranthaceae. TYPES. YPM 6214-6215-
    Cissites insignis Capellini and Heer. TYPE. YPM-6318-
    Cissites lobata Dorf. TYPE. YPM-6306May belong in Hamemelididae (subclass which includes sycamore)
    Cissites puilasokensis Heer. TYPE. YPM 6311-6312-
    Coniferales YPM-8792; YPM 8820-8821conifer
    Cupressinocladus interruptus (Newberry) Schweitzer YPM-6354-
    Dilleniidae. TYPE #1. YPM-6193; TYPES #2. YPM 6286-6287-
    Dombeyopsis trivialis Lesquereux YPM-6346; YPM 6377-6379; YPM 6347-6348-
    Dombeyopsis YPM 8198-8201-
    **Dombeyopsis obtusa In Platanales, according to Leo Hickey
    Elatides longifolia (Lesquereux) Johnson. TYPE. YPM-6296-
    Erlingdorfia montana (Brown) Johnson, gen. et comb. nov.Johnson, 1996. In the Platanaceae: Hamamelididae (related to today's Sycamore). A common taxon. See also Johnson and Stucky, 1995.
    Fagaceae. TYPE. YPM-6229Possibly related to members of today's beech family
    Filicales. TYPE #1. YPM-6243; TYPE #2. YPM-6132; TYPE #3. YPM-6322; TYPE #4. YPM-6199-
    Filicites knowltonii Dorf. TYPE. YPM-6259-
    Flacourtiaceae. TYPE. YPM-6273-
    *Gingko adiantoides. TYPE. YPM-6242The only gingko in the Hell Creek Formation; uncommon
    Glyptostrobus Endlicher 1847. TYPE. YPM-6400-
    Glyptostrobus sp. #2. TYPE. YPM-6133-
    Grewiopsis saportana Lesquereux. TYPE. YPM-6126Another generic Hamamelididae
    Hamamelididae. TYPE #1. YPM-6269; TYPE #2. YPM-6146"Witch-Hazel Family". Witch-Hazel and Sweet Gum are modern examples of this plant group.
    Laurales. TYPE #1. YPM-6435; TYPES #2. YPM 6207-6210; TYPE #3. YPM-6154; TYPES #4. YPM 6293-6294; other specimen YPM-6436Today's cinnamon and avocado trees are examples of this group
    Laurophyllum wardiana (Knowlton) Dorf, 1942. YPM-6177-
    Magnolia pulchra Ward, 1884-85[1886]. TYPE. YPM-6309This species was thought to occur only in southern Wyoming flora, but Leo Hickey claims it is found further north in Montana and the Dakotas
    Magnoliopsida. TYPE #1. YPM-6241; TYPES #2. YPM 6134-6135; TYPE #3. YPM-6307; TYPE #4. YPM-6129; TYPE #5. YPM-6127; TYPES #6. YPM 6300-6304; other specimens YPM-6429; YPM-6434-
    Marchantia pealii Knowlton. TYPES. YPM 6252-6253-
    Metasequoia sp. #2. TYPE. YPM-6158Related to today's Dawn Redwood. Examine a fossil Metasequoia seed cone from the Hell Creek Formation
    *Nilssonia yukonensis Hollick. TYPE. YPM-6295The only Hell Creek Formation cycad. Uncommon. A distant living relative is our sago palm.
    Onoclea hesperia Brown 1962. TYPE. YPM-6143-
    Palaeoaster inquirenda. TYPE. YPM-6131 Angiosperm. Produces LARGE seed pods.

    References.:

    Smith, U. R. 2000. Palaeoaster (Papaveraceae), the Cretaceous poppy. Ph.D. Thesis, Yale University: New Haven.

    Smith, U. R., and Hickey, L. J. 1994. A capsular fruit from the latest Cretaceous of the Western Interior United States. American Journal of Botany 81: 102-103.

    PaleoasterYPM 8187-8194; YPM-8195; YPM-8196See above
    Paranymphaea hastata Brown YPM-6438; YPM-6430-
    Pistia corrugata Lesquereux. TYPE. YPM-6198; other specimen YPM-6431-
    **Platanophyllum sp.-
    Platanophyllum montanum (Brown) Dorf. TYPE. YPM-6176; other specimens YPM-6443; YPM 6341-6344; YPM-6352; YPM 6375-6376; YPM 6371-6372; YPM-6373-
    Porosia verrucosa Hickey. TYPE. YPM-6136-
    **Rhamnus salicifoliusAnother Buckthorn look-alike. Abundant at Brownie Butte, MT
    Rosaceae. TYPES. YPM 6201-6202; other specimen YPM-6365AFamily that includes today's roses, apples, cherries, almonds, etc. (a large family)
    Rosidae. TYPE #1. YPM-6326; TYPE #2. YPM-6169; TYPE #3. YPM-6144-
    Sabalites sp. YPM-6439Palm
    Sapindopsis powelliana (Lesquereux) Johnson. TYPES. YPM 6246-6247-
    Sequoia sp. TYPE. YPM-6191Most Lancian Sequoia are placed in S. artus
    **Sequoites artus-
    Taxodium olrikii (Heer) Brown. TYPE. YPM-6192; Other specimens YPM 7777-7778 Related to today's Bald Cypress
    Trochodendrales. TYPE. YPM-6194; Other specimen YPM-6437-
    **Trochodendroides arctica-
    Trochodendroides nebrascensis (Newberry) Dorf. TYPES. YPM 6231-6232; Other specimen YPM-6444-
    Ulmaceae. TYPE #1. YPM-6159; TYPE #2. YPM-6160 Elm?
    Urticaceae. TYPES #1. YPM 6221-6222; TYPE #2. YPM-6142Nettle family
    Zingiberopsis attenuata Hickey and Peterson, 1978. TYPE. YPM-6328Related to todays ginger plant. Its closest living relative is the Asian genus Alpinia. Some Hell Creek Fm. specimens show damage from hispine beetles ("leaf beetles" (Wilf et. al, 2000)).
    aff. "Dryophyllum" subfalcatum. TYPE. YPM-6255-
    aff. "Populus" nebrascensis. TYPE. YPM-6137-
    aff. "Vitis" Stantonii (Knowlton) Brown. TYPE #1. YPM-6298; TYPE #2. YPM-6288; TYPE #3. YPM-6321-
    aff. Cercidiphyllum sp. TYPE. YPM-6254Witch-hazels and Katsura trees. Johnson (1998) notes the presence of Cercidiphyllaceae in the Formation
    aff. Laurales. TYPE #1. YPM-6324; TYPE #2 YPM-6156-
    aff. Platanaceae. TYPE #1. YPM-6244;TYPES #2. YPM 6280-6281;TYPE #3. YPM-6168; TYPE #4. YPM-6162; TYPES #5. YPM 6329-6330-
    aff. Saururaceae. TYPE. YPM-6315-
    cf. "Cinnamomum" lineafolia. TYPE. YPM-6240-
    cf. "Cocculus" flabella. TYPE. YPM-6140-
    cf. Cissites acerifolia Lesquereux. TYPE. YPM-6185-
    cf. Nelumbo. TYPE #1 YPM-6316A; TYPE #2 YPM-6316B-
    cf. Pistia corrugata. TYPE. YPM-6200Floating aquatic herb
    unknown flowers. YPM-7209A-
    unknown seed. TYPE. YPM-6206-
    unknown seed. YPM-6445-

    Comments:

    Dr. Kirk Johnson claims that there are no grasses, oaks, maples, or willows in the Hell Creek Formation. Ferns are uncommon in the majority of the formation, however there is a great increase in the abundance of fossil fern spores in the two centimeters of rock that directly overlies the impact fallout layer (the famous K-T boundary layer). This increase in fern spore abundance is commonly referred to as "the fern spike" (meaning that if the abundance of spores as a function of stratigraphic position were plotted out, the graph would show a spike just above the impact fallout layer). Johnson also found that the majority of the angiosperm genera in the Hell Creek Formation are now extinct. He also believes that, very roughly, 80% of the terrestrial plant taxa died out in what is now Montana and the Dakotas at the K/T boundary.

    Many of the modern plant affinities in the Hell Creek Formation (e.g., those with the prefix "aff." or with quotes around the genus name) may not in reality belong to these genera; instead they could be entirely different plants that resemble modern genera. Therefore, there is some question regarding whether the modern Populus or Juglans, as two examples, actually lived in the latest Cretaceous.

    Compared to the rich Hell Creek Formation fossil plant localities of the Dakotas, relatively few plant specimens have been collected from Montana. I added a few taxa that were collected at Brownie Butte Montana by Shoemaker, but most plants were collected from North Dakota (Slope County) and from South Dakota. "TYPE" after the binomial means that it is represented by a type specimen found in the Yale-Peabody Museum collections. "YPM" is the prefix for the Yale-Peabody Museum specimen number.
    The Araucariaceae may be the source plants for amber in the formation. Cretaceous amber from Lebonon (135 mya - 120 mya) comes from the flora Araucaria and Agathis. I have not found any specific references regarding the source flora for the North American Hell Creek amber, so if anyone has a reference on its source, please let me know!

    References:

    1. Yale-Peabody Museum specimen collection gopher server, year 1994.

    2. * = Johnson, K. 1997. Hell Creek Flora, pp. 300-302, in Currie, P., and K. Padian (eds.), Encyclopedia of Dinosaurs, Academic Press, 869 pages.

    3. Johnson, K. R. 1998. Floristics and taphonomy of anomalous, small-leaved floras from the middle Hell Creek Formation (Late Cretaceous; late Maastrichtian), southwestern North Dakota. American Journal of Botany, Vol. 85, No.6, 1-191. Baltimore, Maryland Meeting. June 1998 Supplement-Abstracts, pg. 75, Abstract 218.

    4. Johnson, K. R., and Stucky, R.K. 1995.Prehistoric Journey Robert Rinehart Publishers. 144 p.

    5. Johnson, K. R. 1996. Description of seven common fossil leaf species from the Hell Creek Formation (Upper Cretaceous: Upper Maastrichtian), North Dakota, South Dakota, and Montana. Proceedings of the Denver Museum of Natural History Series 3, No. 12, 47 p.

    6. Wilf, P., C. C. Labandeira, W. J. Kress, C. L. Staines, D. M. Windsor, A. L. Allen, and K. R. Johnson. 2000. Timing the radiations of leaf beetles: Hispines on gingers from latest Cretaceous to Recent. Science 289:291-294.

    7. ** = Also found at Brownie Butte, MT by Dr. R. E. Shoemaker.


    ACKNOWLEDGEMENTS
    There have been so many people who have discussed the Hell Creek Formation with me that I cannot possibly do justice by listing only a few names while leaving the rest of them out. Therefore, I give a big THANK YOU to all who have contacted me over the last decade and a half.


    Go back to my opening page

    Hell Creek Life copyright © 1997-2010 by Phillip Bigelow
    Last revised: July 21, 2010; First edition: November 3, 1997