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I think it's got nothing to do with what the pinna (commonly known as the sticky out bit) does and everything to do with the way reptiles have 'evolved'. eg there has been no need for pinnae in reptiles, so no genome exists. that's a bit boring isn't it?
Ok, here’s my theory: Modern day reptiles, like my two tortoises here, are low slung on their legs. [attachment=4316]Their bodies are close to the ground and usually, when at rest, the body is settled on the ground, or as with snakes, the entire body is for the most part in contact with the ground most of the time. This would mean that most reptiles, in common with snakes, rely largely on vibration travelling through the ground and felt throughout the entire body to amplify sound. The strongest feeling of this vibration on the body, or on whichever leg, gives the direction from which the vibration is emanating. This would make a directional air vibration concentration device (the pinna) unnecessary.As for the earlier reptiles (the dinosaurs), many of these were similarly low slung on their legs, while other much larger dinosaurs, such as Diplodocus, lived largely in water to help the legs bear the weight of these huge creatures, and water is an excellent conductor of sound waves. So again, like modern fish, sound and the direction from which it is coming, can be determined from the first point of contact with the body. For a modern example of this in a reptile, just take a look at the Crocodilians.Another reason why dinosaurs did not develop a directional sense of hearing may well be the habitat at their time. The Earth was covered in vegetation which would have included large tree ferns etc. In such conditions, airborne sound waves would be absorbed by some of the vegetation and bounced by trunks. This would have made airborne sound waves an unreliable means of detecting direction. Ground vibration, on the other hand, I do not think is quite so vulnerable to echoes, so would be a far better means of detecting direction. The evolution of a directional airborne sound wave concentration device was therefore not simply unnecessary, but might even have proved to be so unreliable as to put the individual at risk.Will you be breathing again now? Or will you wait for someone more knowledgeable on Herpetology to give a more rational explanation?
Turtles, lizards and snakes etc. would probably not find streamlining of any real benefit.
Have a look at the ears on a sealion, then tell me they have not been streamlined.If a creature spends time in water then streamlined mutations will be beneficial, e.g. vestigial pinnae (sealion), no pinnae (seal).
QuoteHave a look at the ears on a sealion, then tell me they have not been streamlined.If a creature spends time in water then streamlined mutations will be beneficial, e.g. vestigial pinnae (sealion), no pinnae (seal).Precisely my point, as you say Sealions have a vestigial pinnae. They are more suited to the animals lifestyle than a large, forward facing cup shaped ear would be. They are small, smooth and streamlined themselves. The drag effect of this pinna would be minimal. Also your wording is an indication as to the presence of this pinna, 'vestigial'. Perhaps at some time in it's past, the Sealion's ancestors had need of a directional listening device, which is no longer required. At some time in the next 100 or so generations, this vestigial pinnae may have disappeared altogether. Evolution at work.