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The diversity and distribution of nonmarine teleost fishes in the Western Interior of North America during the late Maastrichtian is documented based on isolated elements from vertebrate microfossil localities in the Hell Creek Formation of Montana, the Lance Formation of Wyoming, and the Scollard Formation of Alberta. A minimum of 20 taxa are recognized based on >1900 abdominal centra and tooth-bearing elements. These include two elopomorphs, six osteoglossomorphs, three ostariophysans, one esocid, six acanthomorphs, and two taxa of unknown relationships. These assemblages differ from late Cam-panian assemblages in the absence of the Clupeomorpha and the presence of the Perciformes. Within the Hell Creek Formation, we record patterns in the relative abundances of the most abundant taxa leading up to the Cretaceous-Paleogene (K-Pg) boundary. Most notably, acanthomorphs increased in abundance upsection, whereas a group of osteoglossomorphs, represented by Coriops and (or) Lopadichthys, concurrently decreased in abundance. Conversely, some teleosts exhibited more stable or slightly fluctuating relative abundances throughout the formation (Wilsonichthyidae, Esocidae). These late Maastrichtian teleost assemblages are of higher diversity than an early Eocene assemblage from Wyoming preserved under similar tapho-nomic conditions. This pattern suggests either that lower Cenozoic deposits in the Western Interior are insufficiently sampled or that the K-Pg mass extinction event adversely affected nonmarine teleosts. Key words: Scollard, Hell Creek, Lance, Cretaceous, Cretaceous-Paleogene mass extinction, Osteoglossomorpha, Elopomorpha, Ostariophysi, Esocidae, Acanthomorpha, diversity. La diversite et la repartition des poissons teleosteens non marins dans l'interieur de l'Ouest de l'Amerique du Nord au Maastrichtien tardif sont documentees a la lumiere d'elements isoles issus de localites a microfossiles de vertebres dans la Formation de Hell Creek du Montana, la Formation de Lance du Wyoming et la Formation de Scollard de l'Alberta. Au moins 20 taxons sont releves a la lumiere de plus de 1 900 centra abdominaux et elements dentes. Ces taxons compren-nent deux elopomorphes, six osteoglossomorphes, trois ostariophysiens, un esocide, six acanthomorphes et deux taxons aux relations inconnues. Ces assemblages se distinguent d'assemblages du Campanien tardif par l'absence de clupeomor-phes et la presence de perciformes. Dans la Formation de Hell Creek, nous notons que les abondances relatives des taxons les plus abondants definissent des motifs a l'approche de la limite Cretace-Paleogene (K-Pg). L'abondance des acanthomor-phes augmente notamment vers le haut de la coupe, alors que l'abondance d'un groupe d'osteoglossomorphes represente par Coriops et (ou) Lopadichthys presente une diminution concurrente. A l'inverse, certains teleosteens sont caracterises par des abondances relatives plus stables ou legerement fluctuantes dans l'ensemble de la formation (wilsonichthyides, eso-cides). La diversite de ces assemblages de teleosteens du Maastrichtien tardif est plus grande que celle d'un assemblage de l'Eocene precoce du Wyoming preserve dans des conditions taphonomiques semblables. Cette distribution donne a penser que l'echantillonnage des depots du Cenozo'ique inferieur dans l'interieur de l'Ouest est insuffisant ou que l'evenement d'extinction massive a la limite K-Pg a eu des effets nefastes sur les teleosteens non marins. [Traduit par la Redaction] Mots-cles: Scollard, Hell Creek, Lance, Cretace, extinction massive Cretace-Paleogene, osteoglossomorphes, elopomorphes, ostariophysiens, esocides, acanthomorphes, diversite., Introduction Vertebrate microfossil assemblages, which are concentrations of small disarticulated and isolated vertebrate hard parts (e.g., bones, teeth, and scales), have long been recognized as an exceptional source of information [...]

The posterior portion of a sturgeon skull preserved in a nodule was recovered from the latest Campanian sediments of the Horseshoe Canyon Formation in the city of Edmonton, Alberta, Canada. It is described here as a new genus and species of Acipenseriformes. The skull represents an individual of at least 2 meters in total length. This species is of particular interest because different bones of the skull show a surface ornamentation with different patterns; the clavicle has large pits, the dermal skull bones have smaller pits and radiating ridges, and the subopercle shows fine radiating ridges. The new taxon, here named †Boreiosturion labyrinthicus, can be confidently included in the extant family Acipenseridae but a phylogenetic analysis does not further resolve relationships. This fossil is the first documentation of sturgeon in the latest Campanian of North America, and bridges the gap between the mid-Campanian assemblage of Dinosaur Park and the late Maastrichtian material from the Hell Creek Formation. [ABSTRACT FROM AUTHOR]

Although the Jurassic was a period of high diversity in ichthyosaurs, only a small number of specimens have been recorded from Canada to date. We describe here a new occurrence of an ophthalmosaurid ichthyosaur from a shallow marine depositional environment within the Bowser Basin of northern British Columbia. Based on vertebral diameters and the size of the humerus, the ichthyosaur was relatively large compared to other contemporaneous forms, yet possessed teeth that were small for its body size. As well, the height to length ratio of the preserved vertebrae suggests it may have had a more elongate, less regionalized body shape. Although indeterminate at a generic level, the presence of Late Jurassic ichthyosaurs in nearshore waters of northwestern North America further demonstrates their cosmopolitan distribution. Si le Jurassique fut une periode de forte diversite chez les ichthyosaures, seul un petit nombre de specimens a ete enregistre au Canada a ce jour. Nous decrivons une nouvelle occurrence d'ichthyosaure ophthalmosauride d'un milieu de sedimentation marin peu profond dans le bassin de Bowser du nord de la Colombie-Britannique. A la lumiere du diametre des vertebres et de la taille des humerus, l'ichthyosaure etait relativement grand par rapport a d'autres formes contemporaines, mais possedait de petites dents pour la taille de son corps. Le rapport entre la hauteur et la longueur des vertebres preservees semble en outre indiquer une forme du corps plus allongee et moins regionalisee. Bien que le genre ne soit pas determine, la presence d'ichthyosaures au Jurassique tardif dans les eaux littorales du nord-ouest de l'Amerique du Nord constitue une nouvelle demonstration de leur repartition cosmopolite. [Traduit par la Redaction], Introduction Ichthyosaurs were a diverse and cosmopolitan group of highly aquatic marine reptiles that first appeared in the Early Triassic and survived until the Late Cretaceous (Sander 2000; McGowan and [...]

Previously reported and new specimens of marine turtles from the late Campanian of Alberta, Canada, provide additional information on the diversity and distribution of chelonioid turtles at this time. An articulated carapace from the Bearpaw Formation previously interpreted as Lophochelys niobrarae is considered to be a juvenile of a specifically indeterminate chelonioid and is referred to Lophochelys sp. Isolated neurals and a hyoplastron from nonmarine estuarine deposits in the uppermost beds of the Dinosaur Park Formation are tentatively referred to Lophochelys sp. These specimens suggest that this chelonioid could enter freshwater environments. A new chelonioid, Kimurachelys slobodae gen. et sp. nov., is recognized on the basis of two mandibles and a maxilla from the uppermost beds of the Dinosaur Park Formation of southeastern Alberta. A partial postcranial skeleton of an indeterminate chelonioid from the Bearpaw Formation provides additional evidence that chelonioids of this formation included taxa that were phylogenetically intermediate between chelonioids of the late Santonian and members of the crown group. Des specimens deja signales et de nouveaux specimens de tortues de mer du Campanien tardif de l'Alberta (Canada) fournissent de nouveaux renseignements sur la diversite et la repartition des tortues chelonioides a cette epoque. Une carapace articulee de la Formation de Bearpaw precedemment interpretee comme appartenant a Lophochelys niobrarae est consideree provenir d'un chelonioide juvenile d'espece indeterminee et est affecte a Lophochelys sp. Des os neuraux isoles et un hyoplastron provenant de depots estuariens non marins dans les lits sommitaux de la Formation de Dinosaur Park sont provisoirement affectes a Lophochelys sp. Ces specimens donnent a penser que ce chelonioide pouvait penetrer dans des milieux d'eau douce. Un nouveau chelonioide, Kimurachelys slobodae gen. et sp. nov., est reconnu sur la base de deux mandibules et d'une maxille dans les lits sommitaux de la Formation de Dinosaur Park du sud-est de l'Alberta. Un squelette postcranien partiel d'un chelonioide indetermine de la Formation de Bearpaw fournit d'autres preuves du fait que les chelonioides de cette formation comprenaient des taxons intermediaires sur le plan phylogenique entre les chelonioides du Santonien tardif et les membres du groupecouronne. [Traduit par la Redaction], Introduction Marine turtles of Late Cretaceous age from the Western Interior of North America are of interest because they document early stages in the evolution of the Chelonioidea (Zangerl 1953; [...]

Albertosuchus knudsenii gen. et sp. nov. is described on the basis of an incomplete skeleton from the lower part (uppermost Cretaceous) of the Scollard Formation, southern Alberta, Canada. It is probably a crocodyloid, the only Canadian representative of the group and also the sole crocodylian known during the latest Cretaceous in Canada. Within the Crocodyloidea, A. knudsenii is one of the most basal forms and shares a sister-group relationship with the European genus Arenysuchus. However, it needs to be emphasized that because of its incompleteness, phylogenetic relationships proposed here for A. knudsenii may change when better-preserved specimens are found. Albertosuchus knudsenii differs from other crocodyloids in having no premaxilla-maxillary notch, a very short mandibular symphysis with the involvement of the splenial, and an extremely deep hypapophysis on the last cervical and anterior dorsal vertebrae. The discovery of A. knudsenii may expand the geographical range of the Crocodyloidea into Canada during the Cretaceous. Crocodylians in the lower part of the Scollard Formation are of low diversity compared with that of the corresponding Hell Creek Formation of Montana and Lance Formation of Wyoming, both farther to the south in the USA. Albertosuchus knudsenii gen. et sp. nov. est decrit sur la base d'un squelette incomplet provenant de la partie inferieure (Cretace sommital) de la Formation de Scollard, dans le sud de l'Alberta (Canada). Il s'agit probablement d'un crocodiloide, le seul representant canadien dugroupe et egalement le seul crocodilien connu du Cretace terminal au Canada. Au sein des crocodiloides, A. knudsenii est une des formes les plus basales et partage un lien de groupe-frere avec le genre europeen Arenysuchus. Il importe toutefois de souligner que, en raison de son caractere incomplet, les relations phylogenetiques proposees ici pour A. knudsenii pourraient changer avec la decouverte de specimens mieux preserves. Albertosuchus knudsenii se distingue d'autres crocodiloides par l'absence d'encoche premaxillaire-maxillaire, une symphyse mandibulaire tres courte avec intervention du splenial et une hypapophyse extremement profonde sur la derniere vertebre cervicale et les vertebres dorsales anterieures. La decouverte d'A. knudsenii pourrait elargir l'aire de repartition geographique des crocodiloides jusqu'au Canada durant le Cretace. Les crocodiliens dans la partie inferieure de la Formation de Scollard presentent une faible diversite par rapport a celle des Formations correspondantes de Hell Creek au Montana et de Lance au Wyoming, toutes deux situees plus au sud, aux Etats-Unis. [Traduit par la Redaction], Introduction Crocodylians are an important part of most Late Cretaceous and Palaeocene vertebrate assemblages in the Western Interior of North America. In Canada, crocodylian remains are common in the middle-upper [...]

Myledaphus bipartitus is a Late Cretaceous (75 Ma) freshwater guitarfish, commonly represented by teeth and vertebral centra. The species was first described in 1876, but until now, very little has been known about its ecology and life history. We analyzed the age and growth using 117 fossilized centra (74 hemisectioned) from the Oldman and Dinosaur Park formations of southern Alberta. The resulting estimated maximum age was 16 years. Radial distance (RD) at the estimated asymptotic growth was calculated, and average RD at birth and 3 years were compared with two extant marine species of Rhinobatos (R. productus and R. rhinobatos). Birth ring size ranged from 0.9 to 1.8 mm RD. At age three, centrum RD was between 2.8 and 4.6 mm RD for M. bipartitus and significantly less than R. productus and R. rhinobatos (5.0-6.6 mm RD). Myledaphus approached 'asymptotic' growth at 7.8 mm RD in the growth equation. The growth trajectory of Myledaphus had a similar slope to the Rhinobatos species, but with significantly smaller centrum RD. Rhinobatos rhinobatos also outlived Myledaphus by 8 years. Myledaphus bipartitus est un poisson-guitare d'eau douce du Cretace tardif (75 Ma) communement represente par des dents et des centres vertebraux. L'espece a ete decrite pour la premiere fois en 1876, mais jusqu'a present, les connaissances sur son ecologie et son cycle de vie etaient tres limitees. Nous en avons analyse l'age et la croissance a la lumiere de 117 centres fossilises (74 hemisectionnes) des Formations d'Oldman et de Dinosaur Park du sud de l'Alberta. L'age maximum ainsi estime etait de 16 ans. La distance radiale (RD) au taux de croissance asymptotique estime a ete calculee, et les RD moyennes a la naissance et a trois ans ont ete comparees a celles de deux especes marines actuelles de Rhinobatos (R. productus et R. rhinobatos). La taille des anneaux a la naissance, en termes de RD, va de 0,9 mm a 1,8 mm. A 3 ans, la RD des centres va de 2,8 mm a 4,6 mm pour M. bipartitus et est significativement plus faible que celles de R. productus et R. rhinobatos (RD de 5,0-6,6 mm). Myledaphus s'approche de la croissance << asymptotique >> a une RD de 7,8 mm dans l'equation de croissance. La trajectoire de croissance de Myledaphus presente une pente semblable a celle des especes de Rhinobatos, bien qu'avec des RD des centres significativement plus faibles. La duree de vie de Rhinobatos rhinobatos surpasse egalement de 8 ans celle de Myledaphus. [Traduit par la Redaction], Introduction Myledaphus bipartitus, Cope, 1876, is a Late Cretaceous enigmatic freshwater batoid represented predominantly by isolated teeth (Cappetta 2012). It is known from various Campanian formations such as the Oldman [...]

A high-resolution biostratigraphic analysis of 287 dinosaurian macrofossils and 138 bonebeds in the Edmonton Group (Upper Cretaceous) of southern Alberta provides evidence for at least three dinosaurian assemblage zones in the Horseshoe Canyon Formation (HCFm). From bottom to top the zones comprise unique assemblages of ornithischians and are named as follows: (1) Edmontosaurus regalis--Pachyrhinosaurus canadensis (lower zone); (2) Hypacrosaurus altispinus--Saurolophus osborni (middlezone); and (3) Eotriceratops xerinsularis (upper zone). Whereas the lower and middle zones are well defined and based on abundant specimens, the validity of the uppermost zone (E. xerinsularis) is tentative because it is based on a single specimen and the absence of dinosaur taxa from lower in section. The transition from the lower to the middle zone coincides with the replacement of a warm-and-wet saturated deltaic setting by a cooler, coastal-plain landscape, characterized by seasonal rainfall and better-drained substrates. Whereas changes in rainfall and substrate drainage appear to have influenced the faunal change, changes in mean annual temperature and proximity to shoreline appear to have had little influence on faunal change. We speculate that the faunal change between the middle and upper zones also resulted from a change in climate, with ornithischian dinosaurs responding to the re-establishment of wetter-and-warmer climates and poorly-drained substrates. Compared with the shorter-duration and climatically-consistent dinosaurian assemblage zones in the older Dinosaur Park Formation of southern Alberta, HCFm assemblage zones record long-term morphological stasis in dinosaurs. Furthermore, the coincidence of faunal and paleoenvironmental changes in the HCFm suggest climate-change-driven dinosaur migrations into and out of the region. Une analyse biostratigraphique de haute definition de 287 macrofossiles de dinosauriens et de 138 lits a ossements dans le Groupe d'Edmonton (Cretace superieur) du sud de l'Alberta appuie la these d'au moins trois zones d'assemblage dinosaurien dans la Formation de Horseshoe Canyon (HCFm). De la base vers le sommet, ces zones comprennent des assemblages uniques d'ornithischiens et sont designees comme suit: (1) Edmontosaurus regalis--Pachyrhinosaurus canadensis (zone inferieure), (2) Hypacrosaurus altispinus--Saurolophus osborni (zone mediane) et (3) Eotriceratops xerinsularis (zone superieure). Si les zones inferieure et mediane sont bien definies a la lumiere de specimens abondants, la validite de la zone superieure (E. xerinsularis) reste a confirmer puisque sa definition repose sur un seul specimen et sur l'absence de taxons dinosauriens plus bas dans la section. La transition de la zone inferieure a la zone mediane coincide avec le remplacement d'un milieu deltaique sature chaud et humide par un paysage de plaine cotiere plus frais caracterise par des pluies saisonnieres et des substrats mieux ressuyes. Si des variations de la pluviometrie et du ressuyage du substrat semblent avoir influence les changements fauniques, les variations de la temperature annuelle moyenne et la proximite du littoral semblent, en revanche, n'avoir eu que peu d'incidence sur les changements aux assemblages fauniques. Nous postulons que les changements fauniques entre les zones mediane et superieure decoulent egalement de changements climatiques, les dinosaures ornithischiens reagissant au retablissement de climats plus humides et chauds et de substrats mal ressuyes. Par rapport aux zones d'assemblage dinosaurien de plus courtes durees et coherentes sur le plan climatique de la Formation de Dinosaur Park, plus vieille, du sud de l'Alberta, les zones d'assemblage de la HCFm refletent une stase morphologique de longue duree chez les dinosaures. En outre, la coincidence de changements fauniques et paleoenvironnementaux dans la HCFm laisse croire a des migrations de dinosaures vers la region et vers l'exterieur de celle-ci en reponse a des changements climatiques. [Traduit par la Redaction], Introduction Since 1910, the Upper Cretaceous Edmonton Group (Horseshoe Canyon Formation, Battle and Scollard formations) in south central Alberta has yielded 209 partial to complete dinosaur skeletons, 138 macrofossil, and [...]

Turtle fossils of Paleocene age have been recovered from four formations in Alberta, Canada: the upper (Paleocene) part of the Scollard Formation, the upper (Paleocene) portion of the Willow Creek Formation, and the exclusively Paleocene Porcupine Hills and Paskapoo formations. At least three non-trionychid turtle taxa can be recognized. Definitely present are a generically indeterminate baenid, the macrobaenid Judithemys backmani, and the chelydrid Protochelydra zangerli. The carapace of a juvenile chelydrid could be either a juvenile of P. zangerli or a fourth, distinct taxon. The macrobaenid J. backmani and the chelydrid P. zangerli are the most abundant non-trionychid turtles from the Paleocene of Alberta. The turtles from the Paleocene of Alberta differ from those of comparable age in New Mexico, USA, and other more southern localities in the North American Western Interior in (i) the presence of macrobaenids and chelydrids and (ii) the absence of kinosternoids. These differences mirror those of the Late Cretaceous, suggesting that biogeographic patterns of non-trionychid turtle distributions that were established during the Late Cretaceous in the Western Interior continued well into the Paleocene. Des fossiles de tortue d'age paleocene ont ete recuperes de quatre formations en Alberta (Canada), a savoir la partie superieure (paleocene) de la Formation de Scollard, la partie superieure (paleocene) de la Formation de Willow Creek et les Formations de Porcupine Hills et de Paskapoo, d'age exclusivement paleocene. Au moins trois taxons de tortues non trionychidees sont reconnus. Un baenide de genre indetermine est definitivement present, ainsi que le macrobaenide Judithemys backmani et le chelydride Protochelydra zangerli. La carapace d'un chelydride juvenile pourrait appartenir soit a un specimen juvenile de P. zangerli ou a un quatrieme taxon distinct. Le macrobaenide J. backmani et le chelydride P. zangerli sont les tortues non trionychidees les plus abondantes du Paleocene de l'Alberta. Les tortues du Paleocene de l'Alberta se distinguent de tortues d'age semblable du Nouveau-Mexique (Etats-Unis) et d'autres localites plus meridionales de l'Interieur de l'Ouest de l'Amerique du Nord par (i) la presence de macrobaenides et de chelydrides et (ii) l'absence de kinosternoides. Ces differences sont semblables aux differences observees au Cretace tardif, ce qui porte a croire que les patrons biogeographiques de repartition des tortues non trionychidees etablis au Cretace tardif dans l'Interieur de l'Ouest se sont maintenus durant une bonne partie du Paleocene. [Traduit par la Redaction], Introduction The Paleocene of Alberta, Canada, is well known for a high diversity of mammals and for the most diverse freshwater Paleocene fish assemblage known from North America (Fox 1990; [...]

Horseshoeichthys armaserratus, gen. et sp. nov., (Clupeomorpha: Ellimmichthyiformes: Sorbinichthyidae) is described from the Horseshoe Canyon Formation (Maastrichtian), Albertosaurus bonebed locality, Alberta, Canada. Horseshoeichthys armaserratus is classified as an ellimmichthyiform based on the following characters: the presence of a sixth infraorbital with a sensory canal that leads to the fifth infraorbital, absence of a supraorbital bone, subrectangular predorsal scutes, parietals in contact with each other at the midline, and two supramaxillae. The specimen is classified in the Sorbinichthyidae Family as it has abdominal ribs articulating in pits on the centra, posterior spines on predorsal scutes, and absence of a median spine on predorsal scutes. A new genus and species is proposed based on the presence of (anteriorly) Y-shaped mesethmoid, supraorbital, subrectangular predorsal scutes with coarse, rounded serrae on the posterior margin and a large anterior projection, scales with serrae on the circuli, and two postcleithra. This specimen represents the first freshwater ellimmichthyiform from the Upper Cretaceous of North America and the highest paleolatitude (59°N) occurrence known for the family. Furthermore, the dentary and centra have distinctive morphologies that are matched by specimens in microvertebrate localities from three underlying formations, including the Milk River Formation (Santonian), which indicates at least a 14 million year history for this lineage. Horseshoeichthys armaserratus, gen. et sp. nov., (Clupeomorpha: Ellimmichthyiformes: Sorbinichthyidae), de la localite du gisement d'ossements d'Albertosaurus de la Formation de Horseshoe Canyon (Maastrichtien), en Alberta, au Canada, est decrit. Horseshoeichthys armaserratus est affecte aux ellimmichthyiformes a la lumiere des caracteres suivants : la presence d'un sixieme sous-orbitaire presentant un canal sensoriel qui mene au cinquieme sous-orbitaire, l'absence d'un os sus-orbitaire, des plaques osseuses pre-dorsales sub-rectangulaires, des parietaux en contact les uns avec les autres au niveau de la ligne meediane et deux sus-maxillaires. Le specimen est affecte aux sorbinichthyides puisqu'il presente des cotes abdominales s'articulant dans des fosses sur le centrum et des eepines posteerieures sur les plaques osseuses pre-dorsales, et que ces dernieres n'ont pas d'eepine meediane. Un nouveau genre et une nouvelle espece sont proposesa la lumiere de la presence d'un meesethmolde (anterieurement) en forme de Y, d'un sus-orbitaire, de plaques osseuses pre- dorsales sub-rectangulaires presentant des stries arrondies et epaisses sur leur bord libre posterieur et une grande projection anterieure, d'ecailles avec des stries sur le circulus et de deux postcleithra. Ce specimen represente le premier ellimmichthyiforme d'eau douce du Cretace superieur de l'Ameerique du Nord et l'exemple connu de cette famille provenant de la plus haute paleolatitude (59°N). En outre, le dentaire et le centrum presentent des morphologies particulieres semblables a celles de specimens trouvees dans des localitees de microvertebres de trois formations sous-jacentes, dont la Formation de Milk River (Santonien), ce qui indique une histoire d'au moins 14 millions d'annees pour cette lignee. [Traduit par la Redaction], Introduction Ellimmichthyiformes are an extinct order of double-armored non-clupeiform clupemorphs with taxa that inhabited both marine and freshwater environments (Grande 1985; Hay et al. 2007; Alvarado-Ortega et al. 2008). Ellimmichthyiforms [...]

The faunal assemblage from the early Maastrichtian portion of the Horseshoe Canyon Formation is described on the basis of four new vertebrate microfossil localities and remains from the Albertosaurus bonebed. All of the localities sampled were deposited during a cool, dry climate at a palaeolatitude of ~58°N. Thus, these assemblages provide insight into a northern cool-climate assemblage in the early Maastrichtian of western North America. This fauna is characterized by the presence of taxa with more northern affinities, such as Holostean A, champsosaurs, Troodon, and toothed birds. Warm-climate taxa, such as crocodylians, large and diverse turtles, and albanerpetontids are notable in their absence. The Albertosaurus bonebed locality at the top of unit 4 of the Horseshoe Canyon Formation was deposited during the initial stages of a trend to a warmer and wetter climate that is represented in unit 5. The bonebed shares many taxa with the underlying vertebrate microfossil localities. However, a notable difference is the presence of Atrociraptor marshalli from the Albertosaurus bonebed but not the other localities in the upper Horseshoe Canyon Formation. The presence of Atrociraptor may be attributable to this change in climate rather than local ecological conditions. Also, the assemblages are different in the paucity of fish remains in the bonebed, and the relative rarity of shed hadrosaur teeth. The low abundance of aquatic taxa and rarity of shed teeth of hadrosaurs indicate that the locality is largely autochthonous, with little material being transported into the site. L'assemblage faunique de la portion du Maastrichtien precoce de la Formation de Horseshoe Canyon est decrit a la lumiere de quatre nouvelles localitees de microfossiles de vertebres et de restes provenant du gisement d'ossements d'Albertosaurus. Toutes les localiteeseechantillonneees teemoignent d'un depot en climat sec et frais a une paleolatitude d'environ 58[grados]N. Ainsi, ces assemblages offrent une fenetre sur un assemblage de climat nordique frais du Maastrichtien precoce de l'ouest de l'Amerique du Nord. Cette faune est caracteriseee par la presence de taxons presentant des affinites plus nordiques, tels que des holosteens A, des champsosaures, Troodon et des oiseaux a dents. L'absence de taxons de climat chaud, tels que des crocodiliens, diverses tortues dont de grandes especes et des albanerpetontides, est notable. Les sediments de la localite du gisement d'ossements d'Albertosaurus au sommet de l'unite 4 de la Formation de Horseshoe Canyon ont ete deposes durant les stades initiaux d'une transition vers le climat plus chaud et plus humide representee dans l'unite; 5. Le gisement d'ossements presente bon nombre des mesmes taxons que les localiteesa microfossiles de vertebras sous-jacentes. Toutefois, le fait qu'Atrociraptor marshalli soit present dans le gisement d'ossements d'Albertosaurus, mais absent des autres localitees de la partie superieure de la Formation de Horseshoe Canyon constitue une difference notable. La presence d'Atrociraptor pourrait etre attribuable au changement climatique susmentionne plutot qu'a des conditions ecologiques locales. La paucitee de restes de poissons dans le gisement d'ossements et la rarete relative des dents d'hadrosaure tombees distinguent egalement le gisement d'ossements. La faible abondance de taxons aquatiques et la rarete de dents d'hadrosaure tombeees indiquent qu'il s'agit d'une localitee principalement autochtone caracterisee par une faible proportion de materiel apporte sur les lieux. [Traduit par la Redaction], Introduction Vertebrate microfossil localities are an important source of palaeoecological data because they provide information about the diversity and relative abundance of many taxa not represented by articulated skeletons. While [...]

A new turtle, Aurorachelys gaffneyi gen. et sp. nov., is described on the basis of a carapace and plastron of late Turonian-Coniacian age from Axel Heiberg Island in the High Canadian Arctic. This turtle is a member of the Macrobaenidae, a group that is thought to have originated in Asia. It differs from all other Late Cretaceous macrobaenids in its nearly circular shell. The earliest record of macrobaenids in North America documented by this specimen, together with the earliest records of other turtle clades that presumably originated in Asia, indicates that turtle dispersal was episodic, with most first occurrences of Asian taxa in North America clustering around the Turonian. The high global temperatures of the Turonian are interpreted as facilitating this episode of dispersal of Asian turtle groups into North America. Islands and seamounts in the young, volcanically active Arctic Ocean during the Late Cretaceous may have acted as an alternative to an Alaskan intercontinental route, and may have allowed macrobaenids to enter the part of North America east of the interior continental seaway.

Abstract: A skeleton of a new ceratopsid dinosaur, Eotriceratops xerinsularis gen. et sp. nov., is described in this paper. It is the first associated vertebrate skeleton found within the upper [...]