New material of the Late Cretaceous deltatheroidan mammal Sulestes from Uzbekistan and phylogenetic reassessment of the metatherian-eutherian dichotomy

Sulestes karakshi Nessov, 1985b (= Deltatheroides kizylkumensis Nessov, 1993 = Marsasia aenigma Nessov, 1997) from the Late Cretaceous (Turonian) Bissekty local fauna, Kyzylkum Desert, Uzbekistan, is revised based on additional material from the type locality. It is characterized by an absence of palatal vacuities, double-rooted P1, an asymmetrical M3 with reduced metastylar lobe, an unreduced M4 and m4, obliquely oriented p1, anterior wall of the upper canine alveolus formed by premaxilla, and Meckelian groove on the dentary. PAUP analyses using a data matrix modified from Rougier etal. (1998, 2004) places Sulestes within Deltatheridiidae in an unresolved trichotomy with the Mongolian Campanian Deltatheridium and Deltatheroides. Oklatheridium from the Early Cretaceous of North America is sister taxon to these Late Cretaceous Asiatic deltatheridiidans. Deltatheridiidae is the sister group to other Metatheria including the crown clade Marsupialia. A Deltatheroides-like taxon from the Maastrichtian at Guriliin Tsav, Mongolia, is not related to the Stagodontidae but is sister taxon to other Boreometatheria. The North American Early Cretaceous Atokatheridium, Pappotherium, and Montanalestes are stem tribosphenic mammals, while Holoclemensia is at the base of the eutherian lineage.