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Primitive boreosphenidan mammal [?Deltatheroida] from the Early Cretaceous of Oklahoma

100%
Kielan-Jaworowska Z., Cifelli R. L.
Acta Palaeontologica Polonica
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2001
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tom 46
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nr 3
We describe a new boreosphenidan mammal, Atokatheridium boreni gen. et sp. n., from the Early Cretaceous of Oklahoma, based on an upper molar and a tentatively referred lower molar. The upper molar is characterized by a small protocone and unwinged conules, broad stylar shelf, paracone taller than metacone, and lack of pre- and postcingula. Comparisons with relevant Early and Late Cretaceous boreosphenidans suggest closest similarity to Deltatheroida, including one character (extreme development of the distal stylar shelf, which projects labially and lacks cusps) interpreted as derived. The tentatively attributed lower molar shows similarity to Deltatheridium and the ?aegialodontid genus Kielantherium in having the paraconid higher than the metaconid, but differs from Kielantherium in having a differently shaped talonid. From Aegialodon it differs in having a vertically oriented (rather than semi-procumbent) paraconid and a larger talonid. We figure also two isolated trigonids, differing in size, which show some resemblance to that of ?Atokatheridium. Deltatheroidans, despite their generally primitive dental morphology, are otherwise surely known only from the Late Cretaceous, and are largely restricted to the Old World. If a deltatheroidan, the new taxon implies a significant temporal range extension for the group, and provides another biogeographic link between Cretaceous mammals of Asia and North America.
2
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An extended range of the multituberculate Kryptobaatar and distribution of mammals in the Upper Cretaceous of the Gobi Desert

80%
Kielan-Jaworowska Z., Hurum J. H., Badamgarav D.
Acta Palaeontologica Polonica
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2003
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tom 48
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nr 2
The Late Cretaceous multituberculate mammal Kryptobaatar dashzevegi Kielan−Jaworowska, 1970 is the most common mammalian taxon in the Upper Cretaceous (?lower Campanian) rocks of the Djadokhta Formation at Bayan Zag¹ (= Bayn Dzak) and Tögrög (= Toogreek), and in the beds of Ukhaa Tolgod in the Gobi Desert. Kryptobaataris also common in the Bayan Mandahu Formation (equivalent of the Djadokhta Formation), Inner Mongolia, China, represented there by K. mandahuensis. Kryptobaatar has not been reported as yet from the younger (?upper Campanian) Baruungoyot Formation nor from its stratigraphic equivalents, the red beds of Hermiin Tsav (= Khermeen Tsav). In this paper we report the discovery of an incomplete skull of Kryptobaatar dashzevegi at Hermiin Tsav I. It is the second mammal species common to the Djadokhta and Baruungoyot Formations (the first being Deltatheridium pretrituberculare). We provide a corrected list of mammals found in the Late Cretaceous localities of the Gobi Desert, and we argue (albeit inconclusively), that mammal evidence shows that the Ukhaa Tolgod beds might be closer in time of deposition to the Djadokhta Formation than to that of the Baruungoyot Formation.
3
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Reappraisal of the tribosphenidan mammals from the Trinity Group (Aptian-Albian) of Texas and Oklahoma

70%
Davis B. M., Cifelli R. L.
Acta Palaeontologica Polonica
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2011
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tom 56
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nr 3
The Trinity therians have long been the focus of attempts to reconstruct the evolutionary history of higher mammals, especially in the context of the development of tribospheny. In this paper, we update the taxonomy of the tribosphenidan taxa known from the Trinity Group and establish with more confidence the premolar/molar count in each. Many isolated specimens can be referred to a specific tooth locus. Additional diversity is revealed within the Deltatheroida, with the description of an additional species of Oklatheridium; Pappotherium is here considered a likely metatherian based on the inferred presence of four molars, while Holoclemensia is a basal eutherian (the opposite of some traditional interpretations). The remainder of the genera, Kermackia and Slaughteria, cannot be allied with either of the living groups of tribosphenidan mammals using the available data. We identify strong morphological diversity within this assemblage of stem taxa, including modifications to the traditional tribosphenic occlusal pattern in Kermackia. Mammalian evolution at the base of the tribosphenidan radiation was complex, and this underscores the need for caution when interpreting the morphology and relationships of taxa known by incomplete material.
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