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Stagodontid marsupials from the Late Cretaceous of Canada and their systematic and functional implications

100%

Fox R. C., Naylor B. G.

Acta Palaeontologica Polonica

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2006

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tom 51

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nr 1

Previously undescribed specimens of stagodontid marsupials from Late Cretaceous deposits in Alberta, Canada, reveal new information concerning the upper dentition of Eodelphisspp. and the lower dentition of Didelphodon coyi. Additionally, an incomplete upper dentition of D. coyi from the Scollard Formation extends the range of this species into the Lancian, co−eval with D. vorax and D. padanicus. Stagodontids are in accord with other North American Late Cretaceous marsupials for which the appropriate parts are known in lacking diastemata between the canines and the molars while possessing well−developed palatal vacuities, implying that these morphologies characterized ancestral marsupials. If so, the diastema between P1 and P2 in the Asian middle Early Cretaceous “metatherian” Sinodelphys szalayi is convergent on that in Cenozoic didelphids, and the absence of palatal vacuities in South American Paleogene and Neogene borhyaenids is derived, representing a paedomorphic truncation of development. Claims that the Asian Late Cretaceous “metatherian” Deltatheridium pretrituberculare had a marsupial−like dental replacement pattern are tautological, deduced from an a priori acceptance of a marsupial model of replacement to the exclusion of other, no less realistic, alternatives. The new specimens of Didelphodon coyi demonstrate that upper and lower premolars occluded broadly, implying that the inflated lingual lobes characteristic of Didelphodon premolars evolved primarily as a crushing mechanism, not for passive protection of the gums. Recent speculations that stagodontids were aquatic are not based on credible morphologic or taphonomic evidence and are dismissed, as is speculation that the Judithian species of Eodelphis are sexual morphs of a single species. Current knowledge of Didelphodon compels correction of numerous errors concerning its morphology as presented in recent analyses of marsupial relationships.

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Modelling permafrost distribution in the Canadian Rocky Mountains: A GIS-based approach

100%

Woudsma C. G., Jensen J. F. N., Harris S. A.

Biuletyn Peryglacjalny

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2000

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tom 39

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An unusual early primate from the Paleocene Paskapoo Formation, Alberta, Canada

80%

Fox R.

Acta Palaeontologica Polonica

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2011

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tom 56

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nr 1

A new plesiadapiform primate, Phoxomylus puncticuspis gen. et sp. nov., is described based on an isolated but well−preserved upper molar from the early Tiffanian (late Paleocene) Cochrane 2 locality, southwestern Alberta, Canada. Although possessing a robust postprotoconal fold, an unambiguous synapomorphy of primates, Phoxomylus differs from other plesiadapiforms in its retention of primitive molar features, including acutely pointed major cusps and sharp crests, deep trigon basin, and lack of the bunodont coronal specializations that purportedly marked the transition from insectivorous non−primate ancestors to omnivorous/frugivorous basal primates. Coronal features of the holotype of P. puncticuspis imply that during mastication the mandible was adducted in a near−vertical plane, with little capacity for the transverse movement that is already seen in molar morphology of the earliest and most basal plesiadapiform, Purgatorius. Instead, molar morphology in P. puncticuspis implies emphasis on vertical piercing and shearing, specializations for insectivory unlikely to have been derived via reversal from plesiadapiform ancestors having more bunodont molars adapted for omnivory/frugivory. If that is the case, a long “ghost lineage” must link P. puncticuspis to other, basal plesiadapiforms that have yet to be discovered but that had not yet evolved omnivorous adaptations of the dentition.

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Relict Late Quaternary permafrost on a former nunatak at Plateau Mountain, S.W.Alberta, Canada

80%

Harris S. A.

Biuletyn Peryglacjalny

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1997

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tom 36

5

Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

80%

Currie P. J.

Acta Palaeontologica Polonica

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2003

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tom 48

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nr 2

Beautifully preserved, nearly complete theropod skeletons from Alberta (Canada) allow re−evaluation of the taxonomic status of North American tyrannosaurids. It is concluded that the most parsimonious interpretation of relationships leads to the separation of the two species of Albertosaurus(sensu Russell 1970) into Gorgosaurus libratusfrom the Campanian Dinosaur Park Formation and Albertosaurus sarcophagus from the upper Campanian/lower Maastrichtian Horseshoe Canyon Formation. Albertosaurus and Gorgosaurus are closely related, but can be distinguished from each other by more characters than are known to justify generic distinction within another tyrannosaurid clade that includes Daspletosaurus, Tarbosaurus and Tyrannosaurus. Daspletosaurus is known from multiple species that cover extensive geographic, ecological and temporal ranges, and it is sensible to maintain its generic distinction from Tyrannosaurus. All tyrannosaurid species have consistent ontogenetic trends. However, one needs to be cautious in assessing ontogenetic stage because many characters are size−dependent rather than age−dependent. There are relatively few osteological differences that can distinguish tyrannosaurid species at any age. For example, Nanotyrannus lancensis is probably a distinct species from Tyrannosaurus rex because there is no evidence of ontogenetic reduction of tooth counts in any other tyrannosaurid species. Some characters that are good for separating mature tyrannosaurids, such as differences in the sizes and shapes of maxillary fenestrae, are not useful for identifying the species of juveniles.

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New earliest Tiffanian [Late Paleocene] mammals from Cochrane 2, Southwestern Alberta, Canada

70%

Scott C. S., Fox R. C., Youzwyshyn G. P.

Acta Palaeontologica Polonica

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2002

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tom 47

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nr 4

New mammalian fossils at Cochrane 2, Paskapoo Formation, Alberta, Canada, document five new species and two new combinations: Ptilodus gnomus sp.nov.and Baiotomeus russelli sp.nov.(Multituberculata), Thryptacodon orthogonius comb.nov.and Litomylus grandaletes sp.nov.(“Condylarthra”), Pararyctes rutherfordi sp.nov., Bessoecetor septentrionalis comb.nov., and Paleotomus junior sp.nov.(Eutheria incertae sedis).These new taxa supplement a taxonomically diverse Cochrane 2 local fauna, representing one of the most species rich Paleocene mammalian localities in the world. An earliest Tiffanian age is estimated for the locality based on the presence of the index taxa Plesiadapis praecursor, Nannodectes intermedius, and Ectocion collinus.The Cochrane 2 local fauna fails to demonstrate a decrease in species number relative to those of late Torrejonian localities from the United States, as would be predicted by current paleoclimate scenarios; the rarity of earliest Tiffanian localities in North America suggests sampling error as a partial explanation for the apparent incongruity.

Ograniczanie wyników

4 Acta Palaeontologica Polonica

2 Biuletyn Peryglacjalny

2 Fox R. C.

2 Harris S. A.

1 Currie P. J.

1 Fox R.

1 Jensen J. F. N.

1 Naylor B. G.

1 Scott C. S.

1 Woudsma C. G.

1 Youzwyshyn G. P.

1 2011

1 2006

1 2003

1 2002

1 2000

1 1997

Stagodontid marsupials from the Late Cretaceous of Canada and their systematic and functional implications

Modelling permafrost distribution in the Canadian Rocky Mountains: A GIS-based approach

An unusual early primate from the Paleocene Paskapoo Formation, Alberta, Canada

Relict Late Quaternary permafrost on a former nunatak at Plateau Mountain, S.W.Alberta, Canada

Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada

New earliest Tiffanian [Late Paleocene] mammals from Cochrane 2, Southwestern Alberta, Canada