New Evidence on the Stem Placental Mammal Paranyctoides from the Upper Cretaceous of Uzbekistan

A newly discovered maxillary fragment (ZIN 102716) of Paranyctoides quadrans from the Bissekty Formation (Upper Cretaceous, Turonian) at Dzharakuduk, Uzbekistan shows this species has a P5 about half the labiolingual width of M1 and an infraorbital foramen placed above P4 near the anterior margin of the orbit and below the maxillolacrimal contact. The maxillary foramen, likely posterior to M1, is positioned more posteriorly compared to other stem placental mammals. The infraorbital canal is roofed by a thin plate of maxilla with facets for the lacrimal and jugal above. The posterior part of this roof may be formed entirely by the lacrimal. In Paranyctoides the upper posterior premolars (P4–5) and molars were confined to the posterior third of the maxilla below the orbit, as in the stem therian Eomaia. In a majority of stem placentals, including Early Cretaceous Prokennalestes and Acristatherium, the upper posterior premolars and molars occupy the posterior half of the maxilla, with P4–5 placed in front of the orbit. A new phylogenetic analysis places Paranyctoides in a polytomy with Sheikhdzheilia, Lainodon, and Zhelestinae.