Myotragus balearicus - 1st Known Cold Blooded Mammal

"(PhysOrg.com) -- An extinct goat that lived on a barren Mediterranean island survived for millions of years by reducing in size and by becoming cold-blooded, which has never before been discovered in mammals...

The bones of warm-blooded animals show uninterrupted fast growth, while the bones of cold-blooded animals have parallel growth lines showing interrupted growth corresponding to growth cycles, rather like the rings seen in tree trunks. Growth and metabolism rates are adjusted to suit the amount of food available, whereas warm-blooded animals require food to be available continuously. The Myotragus bones showed the same interrupted growth as reptiles."