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.

Key words: Mammalia,“Z helestidae”,“Z alambdalestidae”, Kulbeckia,pet rosal,L ate Cretaceous,Uzbeki stan.

Eric G. Ekdale [eekdale@mail.utexas.edu], Department of Biology, San Diego State University, San Diego, California 92182−4614, USA. Present address: Department of Geological Sciences, The University of Texas, Austin, Texas 78712−0254, USA; J. David Archibald [darchibald@sunstroke.sdsu.edu], Department of Biology, San Diego State University, San Diego, California 92182−4614, USA; Alexander O. Averianov [sasha@AA1923.spb.edu], Zoological Institute, Russian Academy of Sciences, Universitetskaya nab. 1, Saint Petersburg 199034, Russia.