Soft-shelled turtles (Trionychidae) from the Bissekty Formation (Upper Cretaceous: Turonian) of Uzbekistan: Skull-based taxa and probable skull-shell associations

•We describe new material of Khunnuchelys kizlkumensis from the locality Dzharakuduk.•We describe a second, smaller, trionychine skull morphotype from Dzharakuduk.•The two skull taxa correspond to two shell taxa previously described from the locality.•Khunnuchelys shares some superficial similarities with plastomenids.

In this paper we describe previously unpublished trionychid turtle material, consisting of skull fragments, from the Late Cretaceous (late Turonian) Bissekty Formation of the Dzharakuduk locality in Uzbekistan. This material is assigned to two taxa: the skull-based Khunnuchelys kizylkumensis Brinkman et al. (1993, Can. J. Earth Sci. 30, 2214-2223) and Trionychini indet. Two specimens which cannot be confidently attributed to these two taxa are considered Trionychidae indet. In addition to these trionychid taxa known from skulls, the Dzharakuduk turtle assemblage includes at least two shell-based taxa, Aspideretoides cf. A. riabinini and “Trionyx” cf. “T.” kansaiensis. For this and other Late Cretaceous localities of Middle Asia and Kazakhstan, we suggest the probable skull-shell associations of Khunnuchelys spp. with “Trionyx” kansaiensis-like forms and Trionychini indet. with Aspideretoides-like forms.