Study Finds Crocodile Ancestors Stayed Warm-Blooded Until 66 Million Years Ago
Updated
Updated · Gizmodo · Aug 14
Study Finds Crocodile Ancestors Stayed Warm-Blooded Until 66 Million Years Ago
3 articles · Updated · Gizmodo · Aug 14
Summary
A fossil analysis of 81 archosaur species found crocodile ancestors likely remained warm-blooded until about 66 million years ago, overturning the long-held view that only the bird lineage evolved high-metabolism physiology.
Large blood-vessel holes in fossil leg bones pointed to nutrient blood-flow rates closer to mammals and active reptiles like Komodo dragons than to modern crocodiles, the study’s main evidence.
Roger Seymour and colleagues argue living crocodiles’ four-chambered hearts are another clue their lineage once supported warm-blooded metabolism before later shifting back to a lower-energy state.
That reversal may have helped crocodiles survive the Chicxulub asteroid aftermath, when a slower metabolism and aquatic ambush lifestyle could have been an advantage in the post-impact environment.