Petrosal bones of placental mammals from the Late Cretaceous of Uzbekistan

摘要

Petrosal bones representing "Zhelestidae" and Kulbeckia ("Zalambdalestidae") were recovered from the Late Cretaceous of Uzbekistan and are formally described. The "zhelestid" petrosal retains several characters ancestral to eutherians (if not more basally in the mammalian phylogeny), including a prootic canal, a lateral flange, and a less elliptical fenestra vestibuli. The only other eutherian taxon to retain these structures is the Early Cretaceous Prokennalestes. No characters unique to "zhelestids" and ungulates were found in the "zhelestid" petrosal. The petrosal of Kulbeckia shares several characters in common with other "zalambdalestids" (such as Zalambdalestes and Barunlestes), as well as Asioryctes and Kennalestes, including a curved ridge connecting the crista interfenestralis to the caudal tympanic process, and presence of a 'tympanic process" at the posterior aspect of the petrosal.