Tuesday, May 18, 2010

bird-dino postures

uncinate process in birds

JR Codd 2010 Compar.Biochem.Physiol.A156:303-8
Uncinate processes in birds: morphology, physiology, and function

The avian respiratory system is remarkable in terms of its complexity &
efficiency. The evolution of this system with its unique lung morphology &
physiology has contributed to birds being one of the most successful
vertebrate lineages.
Despite holding the attention of the scientific community for a long time,
much remains to be discovered about the complexities of this system. Recent
advances have highlighted the important role that accessory breathing
structures, the uncinate processes, play in understanding how this system
functions & evolved.
Almost all spp of extant bird have uncinate processes extending from the
mid-point of the vertebral ribs. These processes are integral to the
mechanics of ventilation in birds, being active in both in- & expiration,
but also playing some role during locomotion.
The morphological variation in the uncinate processes suggests that the
constraints placed on the body by adaptations to different forms of
locomotion are key to understanding differences in how birds breathe.
These processes also occur in the theropod dinosaurs, providing further
evidence that they are the ancestors of modern birds, but also highlighting
the intrinsic flexibility in the ventilatory systems of these animals.
death pose of long necked dinos & posture of resting geese: sleeping with head on back above abd. air sacs (parallel to backfloating & whale blowhole on back) while floating or on nest, the eyes see behind when awake but static, able to see predators which approach from behind. Uncinate processes probably evolved as air sac flexible cages allowing leaping-breathing like kangaroos) but bellows not deflating during sleep which would result in sinking.
kangaroo leap breathe

Amazing argonaut octopus: here

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