Quote:
Tinny:
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1. Any modern reptile or bird evolved, not one from another, but from a common ancestor. That common ancestor will not be entirely the same in its lung structure as either reptiles or birds.
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Is there any fossil evidence?
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I haven't looked into this topic for many years, but here are some old quotes (back from when I was a hard-core antievolutionist) I still have (the 'intro' is mine). The quotes from Science are about a find that is only instance I know of of lungs (soft tissue) being preserved in a dinosaur well enough to examine.
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1) The lung of the avian (bird) respiratory system is unique – no other extant animal has its one-way flow-through design, in which the flow of air during both inspiration and expiration is in the same direction. Theropod dinosaurs’ respiratory systems (and many other of their physiological structures, such as particular muscles, trachea, colon, etc.)are closely related to those of modern-day crocodiles, not those of modern-day birds.
“In modern crocodiles this muscle runs from the pubis to the liver and helps move the liver back
and forth like a piston, causing the lungs to expand and contract. An airtight layer of tissue, the
diaphragm, separates liver and lungs. Finding this arrangement, called a hepatic-piston
diaphragm, in the theropod dinosaurs rules out the possibility that they breathed with a
sophisticated birdlike lung…” (Bernice Wuethrich, Stunning Fossil Shows Breath of a Dinosaur,
Science, v283, Number 5401, January 22 1999, p468)
“Together, these [numerous anatomical and physiological] features are consistent with Scipionyx
having used a hepatic piston, diaphragm-assisted breathing (similar to that which occurs in extant
crocodilians) … These attributes are inconsistent with Scipionyx having had an avian-style, lung
air sac system. Moreover, data indicative of diaphragm breathing in such disparate forms as
Sinosauropteryx and Scipionyx reinforce the hypothesis that diaphragm-assisted lung ventilation
was widespread in theropod dinosaurs.” (John A. Ruben, Cristiano Dal Sasso, et al., Pulmonary
Function and Metabolic Physiology of Theropod Dinosaurs, Science, v283, Number 5401,
January 22 1999, p515-516)
“Abdominal air sacs are of fundamental importance to the function of both neo- and paleopulmo
portions of the lung in extant birds. Their likely absence in Scipionyx is an indication that an
avian [bird] style, flow-through, air sac lung was not present in this theropod.” (John A. Ruben,
Cristiano Dal Sasso, et al., Pulmonary Function and Metabolic Physiology of Theropod
Dinosaurs, Science, v283, Number 5401, January 22 1999, p514)
“One reason this is significant is that, as Ruben argues, “a transition from a crocodilian to a bird
lung would be impossible, because the transitional animal would have a life-threatening hernia or
hole in it’s diaphragm””. (Ashly L. Camp, On the Alleged Dinosaurian Ancestry of Birds,
Copyright October 10 1998,
http://home.sprynet.com/trueorigin/birdevo.htm)
“Just how such an utterly different respiratory system could have evolved gradually from the
standard vertebrate design [to that of birds’] is fantastically difficult to envisage, especially
bearing in mind that the maintenance of respiratory function is absolutely vital to the life of an
organism to the extent that the slightest malfunction leads to death within minutes" (Michael
Denton, Evolution: A Theory in Crisis, 1985, Adler & Adler, Bethesda Maryland, p208)