Birds with Teeth

A couple of very early birds with teeth.

1. Ichthyornis (135-70 million years ago) lived 50 million years before T-Rex.
   Hesperornis (80-65 million years ago) arose during the time of T-Rex, but would not have "evolved from" T-Rex in any manner, because Hersperornis' "feathered body had long legs with webbed feet. It was unable to fly or walk. Its wings were small, used for steering when diving underwater." And since Velociraptor was over in Asia, we can rule that beast out too.

   Modern bird's true ancestors in the Cretaceous:

   "The Cretaceous saw the rise and extinction of the toothed birds, Hesperornis and Ichthyornis. The earliest fossils of birds resembling loons, grebes, cormorants, pelicans, flamingos, ibises, rails, and sandpipers were from the Cretaceous."
   (Source).

   Ichthyornis, Kansas and Texas, USA, and in Alberta, Canada, Cretaceous, 135-70 million years ago. Arose BEFORE T-Rex and Velociraptor.
   Ichthyornis (meaning "fish bird") was a tern-like, extinct bird that lived alongside dinosaurs like T. rex and Triceratops. It lived in flocks, nested on shorelines, and hunted for fish in Cretaceous seas. Ichthyornis lived 135-70 million years ago, during the Cretaceous period.
   (Source)

   "A true prehistoric bird of the late Cretaceous period--not a pterosaur or feathered dinosaur--Ichthyornis looked remarkably like a modern seagull, with a long beak and tapered body. However, there were some major differences: this prehistoric bird had a full set of sharp, reptilian teeth planted in a very reptile-like jaw (which is one reason why the first remains of Ichthyornis were confused with those of a marine reptile, Mosasaurus)."
   (Source)

   In appearance, the teeth are very similar to those of the toothed bird, Ichthyornis, but are somewhat smaller.
   (Source)

2. Hesperornis, western United States, Late Cretaceous, 80-65 million years ago.
   Arose at the same time as T-Rex and before Velociraptor.
   Hesperornis had a sleek, feathered body and long legs with webbed feet. Unable to fly or walk. Its wings were small, used for steering when diving underwater. Its long jaws had many small sharp teeth. It was a marine predator, eating fish, ammonites and belemnites. It lived in warm seas, coming ashore only to breed. Ungainly and vulnerable on land - Hesperornis couldn't walk - they crowded together in colonies for safety and chose inaccessible rocky outcrops.
   (Source) and (Source)

   "..Marsh found bones of previously unknown birds: slender, several feet in length, with powerful legs but very small, stubby wings. On a later expedition, Marsh found the skull of one of these birds, and discovered that it had teeth -- a trait missing from all modern birds, but present in the fossil Archaeopteryx, described only a few years earlier, and then as now the oldest and most primitive bird known."
   (Source)

New date for rise of mammals... 220-201 MYA...
More thought really needs to be invested in monotremes and marsupials.

The duck-billed platypus is a semiaquatic egg-laying mammal endemic to eastern Australia. Platypuses are mammals and, like all mammals, are considered warm blooded.