Description: The conventional view of mammals during the Mesozoic has been of tiny shrew-like animals that scurried at the feet of the dinosaurs, relegated to coming out only at night when “the coast was clear”. In 2000, the discovery of a new mammal from the Yixian Formation of Liaoning Province, China known as Repenomamus belied that tiny scurrying animal paradigm. Two species were discovered: Repenomamus giganticus, a dog-sized animal, and Repenomamus robustus, about the size of a modern-day Opossum. R. robustus weighed some 5 kg, and was 50 cm or so in overall length. In 2005, a specimen was found in which the remains of a hatchling Psittacosaurus (see my other offerings for an example of a subadult) were contained within the body cavity. While it can be debated whether the tiny dinosaur was preyed upon or scavenged, there can be no doubt that this mammal did indeed turn the tables on the dinosaurian overlords of the Mesozoic. To my knowledge, this is the only example of its kind on offer anywhere.