Respiratory Evolution Facilitated the Origin of Pterosaur Flight and Aerial Gigantism

Pterosaurs, enigmatic extinct Mesozoic reptiles, were the first vertebrates to achieve true flapping flight. Various lines of evidence provide strong support for highly efficient wing design, control, and flight capabilities. However, little is known of the pulmonary system that powered flight in pterosaurs. We investigated the structure and function of the pterosaurian breathing apparatus through a broad scale comparative study of respiratory structure and function in living and extinct archosaurs, using computer-assisted tomographic (CT) scanning of pterosaur and bird skeletal remains, cineradiographic (X-ray film) studies of the skeletal breathing pump in extant birds and alligators, and study of skeletal structure in historic fossil specimens. In this report we present various lines of skeletal evidence that indicate that pterosaurs had a highly effective flow-through respiratory system, capable of sustaining powered flight, predating the appearance of an analogous breathing system in birds by approximately seventy million years. Convergent evolution of gigantism in several Cretaceous pterosaur lineages was made possible through body density reduction by expansion of the pulmonary air sac system throughout the trunk and the distal limb girdle skeleton, highlighting the importance of respiratory adaptations in pterosaur evolution, and the dramatic effect of the release of physical constraints on morphological diversification and evolutionary radiation

The sympathetic postganglionic and sensory innervation of oviducal magnum in hen: a choleratoxin subunit B-conjugated horseradish peroxidase study

The anatomy of the extrinsic innervation of the avian magnum has not been accurately demonstrated previously. In the present study, choleratoxin subunit B-conjugated horseradish peroxidase (CB-HRP) was used as a retrograde tracer to determine the sympathetic postganglionic and sensory innervation of the magnum of hens. With regard to the sympathetic postganglionic innervation, following CB-HRP injections under the serosa of the magnum, CB-HRP-positive neurons were found bilaterally in the C12–LS13 ganglia of the sympathetic chain, splanchnic ganglia and adrenal ganglia. The number of labelled neurons in the left ganglia of the sympathetic chain and splanchnic ganglia was approximately 2.1 times that in the right ganglia. This suggests that the unilateral magnum is bilaterally innervated with sympathetic postganglionic nerves, the left nerves being predominant. With regard to the sensory innervation, following tracer injections, CB-HRP-positive neurons were found bilaterally in the spinal ganglia C13–LS12, jugular ganglia and nodose ganglia. The number of positive cells in the left ganglia was about 2.2 times that in the right ganglia. In the spinal ganglia, 85.6% of the labelled neurons were in the T5–LS2 and LS8–LS11 ganglia. These results suggest that the sensory nerve fibres of the magnum reach the central nervous system principally via two groups of spinal ganglia and vagus nerves, and that the innervation is bilateral although the left-hand route predominates. Moreover, 45.7% of all the CB-HRP-labelled neurons were found in the rectal region of the intestinal nerve of Remak (INR), which suggests that the INR plays a very important role in the functional regulation of the magnum