Are mice and rats the closest species in appearance and behaviour to the mammals that survived the Cretaceous extinction event?

Are mice and rats the closest species in appearance and behaviour to the mammals that survived the Cretaceous extinction event? We don’t know much about which mammals survived the Cretaceous. It might have been a diverse group, or it might have been just a select few.



This chart depicts some early mammaliaform families and how the Cretaceous extinction affected them.[1] [2]

The scientists who published this chart suspect that the survivors were small and insectivorous, maybe like this guy.[3]

That chart assumes that most placental families became extinct and new ones replaced them. This chart shows a different possibility; maybe most modern mammal families existed before Cretaceous extinction.[4] The red dashed line shows the Cretaceous-Cenozoic boundary.

Blue numbers show likely divergence dates. These numbers are shown to two decimal places, but every number is uncertain. My source describes the entire topic as “highly contentious” which is what scientists say when they feel tempted to get into fist fights. Many paleontologists suspect that most of the divergences shown in that chart happened after the Cretaceous extinction. Molecular biologists, on the other hand, tend to favor the idea that the major modern mammal families mostly existed before the Cretaceous extinction, as shown in this chart.[5] Another way of thinking about this is to consider environments or lifestyles that might have allowed mammals to survive. One researcher has proposed that “ground-dwelling and semi-arboreal mammals were better able to survive the cataclysm than tree-dwelling mammals, due to the global devastation of forests that followed the Chicxulub asteroid impact.”[6] That’s possible but the data behind it consists mostly of guesswork. Conclusion This is another great question for which scientists don’t have a solid answer. Comment with an extra chart. I just want to add that the Cretaceous extinction eliminated most families of mammals. What we have now is just a sliver of what existed during the age of dinosaurs. This chart shows those families.[7] [8]

[1] Untangling the Multiple Ecological Radiations of Early Mammals [2] Untangling the Multiple Ecological Radiations of Early Mammals [3] Paleocene mammals of the world [4] Mammal madness: is the mammal tree of life not yet resolved? | Philosophical Transactions of the Royal Society B: Biological Sciences [5] Mammal madness: is the mammal tree of life not yet resolved? | Philosophical Transactions of the Royal Society B: Biological Sciences [6] Study suggests ground-dwelling mammals survived mass extinction 66 million years ago [7] https://www.researchgate.net/figure/Phylogeny-of-fossil-mammals-Critical-phylogenetic-nodes-are-shown-in-numbers-The_fig1_283270234 [8] Untangling the Multiple Ecological Radiations of Early Mammals