By the Late Cretaceous mammals proper were well established. Fossil marsupial and montremes are known and genetic evidence indicates that true eutherian placentals were around (the most radical molecular clock models suggest most modern mammal orders were already established by the late Mesozoic but this is controversial. The old picture of all Mesozoic mammals being dinky insectivores has been revealed to be inaccurate by some amazing fossils, including one fossil of a badger-like Cretaceous mammal with a small dinosaur in its gut, so you might have fairly reversed the roles in your scene.

Nevertheless, you are technically justified calling these guys “cynodonts” since the group is (otherwise) a paraphyletic grade of close mammal relatives and in order to make the group a monophyletic taxon it has to include mammaliformes, including us. “Typical” cynodonts were once thought to have gone extinct in the Late Triassic, but now there is good evidence that a few hold-outs persisted at least into the Early Cretaceous alongside their true mammalian cousins. There is a controversial non-mammalian therapsid from the Paleocene (Chronoperates which I mentioned in the previous post) but I think the consensus view is that it is more likely to be a true mammal, albeit an archaic one.

There is a very detailed, although now a bit dated fan-site devoted to Mesozoic mammals here.

I guess my take home message would be that 1) the common ancestor of the Koala, Platypus and us was alive in the Mesozoic so you can safely call most Cretaceous synapsids “mammals” 2) despite what is often said in books and websites not all Cretaceous synapsids were retiring insectivores though that ecomorph was well represented among our kin, just as it is today by shrews and solenodons!

So what would you call mammal ancestors at 65 million years ago? I’d love to hear from someone who knows more about the details. And thanks for stopping by.

My understanding is that many of the non-avian dino feathers were a bit fur like – not quite like flight feathers in birds.

Plus it is MUCH easier to create fur using the techniques I used to make this image than it is to make feathers. Really, based on the bits of fossil feathers we’ve found, an artist is pretty much free to use as much artistic license as he wants in the feather/fur/coloration of most dinos (though there are some amazing examples even in the museum next door to me).