Could All Reptiles Be Like the Crocs?

Certain anatomical features distinguish the alligators, crocodiles, gharials and caimen from the other reptiles.

1. A four-chambered heart, something also found in birds and mammals
2. A unidirectional respiratory system
3. A semi-erect posture, midway between the legs of mammals and birds (which were straightly tucked underneath their bodies) and those of other reptiles (which splay away from the body, resulting in a respiratory issue called "carrier's constraint")

On an alternate Earth, ALL of Reptilia (including the legless snakes) have most if not all of the features listed above. (Specifically, each species of reptile has 15% of its body volume reserved for air sacs.) Is this sort of thing both biologically and evolutionarily feasible for all reptiles?

posted about 7 years ago

JohnWDailey‭

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