Cifelliodon

Cifelliodon is an extinct genus of mammaliaform known from the Yellow Cat Member of the Cedar Mountain Formation in Utah, United States, dated to the Early Cretaceous. It contains the species Cifelliodon wahkarmoosuch, described in 2018 based on an isolated skull. This specimen is well preserved and large for a mammaliaform of its time period. Its teeth have been compared to those of the hammer-headed bat, a fruit-eater, while scans of the inner skull allowed for hypotheses regarding brain structure and function. Some of its features resemble those of earlier mammaliamorphs of the Triassic, while others are seen in crown members of Mammalia.

The classification of Cifelliodon has been disputed, with the genus variously labelled a haramiyidan, an allotherian, or neither. The researchers who described it labelled it as evidence that mammaliamorphs with large bodies and diverse ecological roles lived in North America during the Early Cretaceous. The Yellow Cat Member, believed to represent a long span of geologic time, has also yielded remains of a range of dinosaurs.