Cretaceous first appearances

Cimolodonta is a clade of multituberculate mammals that lived from the Cretaceous to the Eocene. They probably lived something of a rodent-like existence until their ecological niche was assumed by true rodents. The more basal multituberculates are found in a different suborder, "Plagiaulacida", a paraphyletic group containing all non cimolodontan multituberculates.

Anacoracidae is a family of extinct mackerel sharks that lived during the Cretaceous. It includes four valid genera: Nanocorax, Ptychocorax, Scindocorax, and Squalicorax. Two previously-included genera, Galeocorax and Pseudocorax, were reassigned to the family Pseudocoracidae.

Toxasteridae is an extinct family of sea urchins.

Palaeophiidae is an extinct family of marine snake within the infraorder Alethinophidia.

Comahuesuchidae is a family of notosuchian crocodyliforms. Constructed in 1991, it includes the genera Comahuesuchus and Anatosuchus. Among the characteristics that are unique to this family is an external naris that is inset into the tip of the snout. There is also a diastema, or gap between the teeth, at the tip of the upper and lower jaws. Both Anatosuchus and Comahuesuchus have maxillary tooth rows in the upper jaw that extend out and over the dentary tooth rows of the lower jaw.