RE: Tell us about the dinosaurs
November 18, 2010 at 1:38 pm
(This post was last modified: November 18, 2010 at 1:46 pm by Anomalocaris.)
It's a fair question to ask why what average people think of as dinosaurs died out while many other cold booded creatures which average people think of as similar to dinosaurs didn't.
But to correct their misconcetions, one can point out that three things:
1. Dinosaurs didn't die out. Birds can be shown by multiple unrelated techniques to have descended directly from dinosaurs, and are in fact themselves dinosaurs. Many dinosaurs had bird like feathers, arranged on their bodies in bird like ways. The evolution of Flying birds' bone structure can be traced step by step back to ground dwelling theropod dinosaurs with hardly a missing link. Remove the evidence of flight feathers from the fossil of the first bird and you will hardly be able to tell the bones apart from relatives of velociraptors. Biochemically the birds are similar to dinosaurs. A tyrannosaurs steak will taste like chicken. Characteristic behavioral patterns of birds, like how bird sleeps and nests, are reminiscent of behavior found in ground dwelling dinosaurs. Every time you hear birds chirp you hear evidence of non-extinction of dinosaurs.
2. Dinosaurs were not very similar to most living reptiles. Their circulatory system separates the delivery of oxygenated blood from non-oxygenated blood, and were thus more efficient than any other reptile's besides crocodiles. Their respiration system uses single pass through flow system involving air sacs throughout their bodies which are unlike those of any reptiles and are far more efficient than those in any mammals. The gait of the dinosaurs were also unlike those of living reptile. Dinosaurs walked like birds and mammals, and some extinct crocodiles, with their legs tucked in and supporting their bodies from underneath, not sprawled out to the side, like lizards sunning themselves.
3. Dinosaurs were warm blooded, unlike any living reptiles. To be sure, not all dinosaurs exhibit unambiguous evidence of endothermy, and it may be that the genes and biochemistry of dinosaurs can more easily accommodate very different levels and types of endothermy between related species than is the case with mammals, but many mid-to-late medium to small sized theropod dinosaurs show unambiguous evidence of internally driven warm bloodedness.
All this does not address why dinosaurs outside the avian lineage apparently didn't produce a single species that survived the Cretaceous termination event, as the closely related birds, more distantly related crocodiles, and the very distantly related mammals, lizards, and snakes were able to do. But it does suggest the reason is not based solely on the particular physiology, genetics or biochemistry of ground dwelling dinosaurs.
But to correct their misconcetions, one can point out that three things:
1. Dinosaurs didn't die out. Birds can be shown by multiple unrelated techniques to have descended directly from dinosaurs, and are in fact themselves dinosaurs. Many dinosaurs had bird like feathers, arranged on their bodies in bird like ways. The evolution of Flying birds' bone structure can be traced step by step back to ground dwelling theropod dinosaurs with hardly a missing link. Remove the evidence of flight feathers from the fossil of the first bird and you will hardly be able to tell the bones apart from relatives of velociraptors. Biochemically the birds are similar to dinosaurs. A tyrannosaurs steak will taste like chicken. Characteristic behavioral patterns of birds, like how bird sleeps and nests, are reminiscent of behavior found in ground dwelling dinosaurs. Every time you hear birds chirp you hear evidence of non-extinction of dinosaurs.
2. Dinosaurs were not very similar to most living reptiles. Their circulatory system separates the delivery of oxygenated blood from non-oxygenated blood, and were thus more efficient than any other reptile's besides crocodiles. Their respiration system uses single pass through flow system involving air sacs throughout their bodies which are unlike those of any reptiles and are far more efficient than those in any mammals. The gait of the dinosaurs were also unlike those of living reptile. Dinosaurs walked like birds and mammals, and some extinct crocodiles, with their legs tucked in and supporting their bodies from underneath, not sprawled out to the side, like lizards sunning themselves.
3. Dinosaurs were warm blooded, unlike any living reptiles. To be sure, not all dinosaurs exhibit unambiguous evidence of endothermy, and it may be that the genes and biochemistry of dinosaurs can more easily accommodate very different levels and types of endothermy between related species than is the case with mammals, but many mid-to-late medium to small sized theropod dinosaurs show unambiguous evidence of internally driven warm bloodedness.
All this does not address why dinosaurs outside the avian lineage apparently didn't produce a single species that survived the Cretaceous termination event, as the closely related birds, more distantly related crocodiles, and the very distantly related mammals, lizards, and snakes were able to do. But it does suggest the reason is not based solely on the particular physiology, genetics or biochemistry of ground dwelling dinosaurs.
