Basic avian pulmonary design and flow-through ventilation in non-avian theropod dinosaurs

  title={Basic avian pulmonary design and flow-through ventilation in non-avian theropod dinosaurs},
  author={Patrick M. O’Connor and Leon P. A. M. Claessens},
Birds are unique among living vertebrates in possessing pneumaticity of the postcranial skeleton, with invasion of bone by the pulmonary air-sac system. The avian respiratory system includes high-compliance air sacs that ventilate a dorsally fixed, non-expanding parabronchial lung. Caudally positioned abdominal and thoracic air sacs are critical components of the avian aspiration pump, facilitating flow-through ventilation of the lung and near-constant airflow during both inspiration and… 

Vertebral morphometrics and lung structure in non-avian dinosaurs

Although fully avian lungs were a rather late innovation, it is quantitatively show that non-avian dinosaurs and basal dinosauriforms possessed bird-like costovertebral joints and a furrowed thoracic ceiling, which could have permitted high levels of aerobic and metabolic activity in dinosaurs, even in the hypoxic conditions of the Mesozoic, contributing to their successful radiation.

Evidence for Avian Intrathoracic Air Sacs in a New Predatory Dinosaur from Argentina

A new predatory dinosaur from Upper Cretaceous rocks in Argentina is described that exhibits extreme pneumatization of skeletal bone, including pneumatic hollowing of the furcula and ilium, and several pneumatized gastralia are described, which suggest that diverticulae of the air sac system were present in surface tissues of the thorax.

Cardio‐pulmonary anatomy in theropod dinosaurs: Implications from extant archosaurs

The likely absence of bird‐like pulmonary function in theropods is inconsistent with suggestions of cardiovascular anatomy more sophisticated than that of modern crocodilians.

Postcranial Pneumaticity in Dinosaurs and the Origin of the Avian Lung

The Air Space Proportion (ASP) is proposed as a measure of proportional volume of air in pneumatic bones, and indicates that increases in the number of cervical vertebrae, their proportional lengths, and their internal complexity occurred in parallel in most of these lineages.

Reassessment of the Evidence for Postcranial Skeletal Pneumaticity in Triassic Archosaurs, and the Early Evolution of the Avian Respiratory System

It is proposed that pulmonary air sacs were present in the common ancestor of Ornithodira and may have been subsequently lost or reduced in some members of the clade (notably in ornithischian dinosaurs), and was potentially primitive for Archosauria as a whole.

Evolution of the Dinosauriform Respiratory Apparatus: New Evidence from the Postcranial Axial Skeleton

Data from this study suggest a progression from a dorsally rigid, heterogeneously partitioned, multichambered lung in basal dinosauriform archosaurs towards the small entirely rigid avian‐style lung that was likely present in saurischian dinosaurs, consistent with a constant volume cavum pulmonale, thin walled parabronchi, and distinct air sacs.

Avian-like breathing mechanics in maniraptoran dinosaurs

This study presents a mechanism whereby uncinate processes, in conjunction with lateral and ventral movements of the sternum and gastral basket, affected avian-like breathing mechanics in extinct non-avian maniraptoran dinosaurs.

Evolution of the Respiratory System in Nonavian Theropods: Evidence From Rib and Vertebral Morphology

Comparing the thoracic rib and vertebral anatomy of Sinraptor, Allosaurus, Tyrannosaurus, and Deinonychus provides new evidence supporting the hypothesis of flow‐through ventilation in nonavian theropods, and concludes that an avian‐style pulmonary system was likely a universal theropod trait.

Evidence for bird-like air sacs in saurischian dinosaurs.

  • M. Wedel
  • Environmental Science, Geography
    Journal of experimental zoology. Part A, Ecological genetics and physiology
  • 2009
Several lines of evidence suggest that air sac-driven lung ventilation was primitive for Saurischia, and anatomical and evolutionary patterns of pneumatization in nonavian saurischian dinosaurs are diagnostic for specificAir sacs, including the cervical, clavicular, and abdominal air sacs.

Pulmonary anatomy in the Nile crocodile and the evolution of unidirectional airflow in Archosauria

The data indicate that the aspects of the crocodilian bronchial tree that maintain the aerodynamic valves and thus generate unidirectional airflow, are ancestral for Archosauria.



Vertebral pneumaticity, air sacs, and the physiology of sauropod dinosaurs

  • M. Wedel
  • Environmental Science, Biology
  • 2003
Air sacs and skeletal pneumaticity probably facilitated the evolution of extremely long necks in some sauropod lineages by overcoming respiratory dead space and reducing mass and may have conveyed some of the respiratory and thermoregulatory advantages enjoyed by birds, a possibility that is consistent with the observed rapid growth rates of sauropods.

Lung Structure and Ventilation in Theropod Dinosaurs and Early Birds

Paleontological and neontological evidence indicates that theropod dinosaurs possessed unmodified, bellowslike septate lungs that were ventilated with a crocodilelike hepatic-piston diaphragm mechanism, consistent with an ectothermic status for theropid dinosaurs and early birds.

Postcranial pneumatization in Archaeopteryx

Two specimens of Archaeopteryx are re-examine and show evidence of vertebral pneumaticity in the cervical and anterior thoracic vertebrae, thus confirming the phylogenetic continuity between the pNEumatic systems of non-avialan theropods and living birds.

Pulmonary pneumaticity in the postcranial skeleton of extant Aves: A case study examining Anseriformes

The relative effects of phylogeny, body size, and behavioral specializations that have been postulated to influence the extent of postcranial skeletal pneumaticity are extricated to extricate.

Comparative respiratory morphology: Themes and principles in the design and construction of the gas exchangers

  • J. Maina
  • Biology
    The Anatomical record
  • 2000
Along the evolutionary continuum, a kaleidoscope of gas exchangers has evolved from the simple cell membrane of the primeval unicells, and in fascinating processes of conformity, different groups of animals have developed similar respiratory structures.

Respiratory and Reproductive Paleophysiology of Dinosaurs and Early Birds

The absence of nasal respiratory turbinates in these animals indicates that they were likely to have maintained reptile‐like (ectothermic) metabolic rates during periods of rest or routine activity, and persistent in vivo burial of their nests and apparent lack of egg turning suggests that clutch incubation by dinosaurs was more reptile- than birdlike.

The origin and early evolution of birds

There is no evidence for a major or mass extinction of birds at the end of the Cretaceous, nor for a sudden ‘bottleneck’ in diversity that fostered the early Tertiary origination of living bird ‘Orders’.

Fluid mechanical valving of air flow in bird lungs.

To achieve unidirectional flow, air in the caudal portion of the primary bronchus must be directed towards the orifices of the mediodorsal bronchi.

Pulmonary function and metabolic physiology of theropod dinosaurs

Ultraviolet light analysis of a fossil of the theropod dinosaur Scipionyx samniticus revealed that the liver subdivided the visceral cavity into distinct anterior pleuropericardial and posterior abdominal regions, providing evidence that diaphragm-assisted lung ventilation was present in theropods.