File:Phylogenetic tree of Theropods respiratory system 01.JPG

English: This diagram illustrate how scientists believe the dinosaur group theropoda shall be classed in a phylogenetic tree, besides Sauropoda and Pterosauria. The main reason with this diagram is to show groups or families which had respiratory system like birds. AS in the diagram is abbreviations for "Airsacs", and ASW means "AirSacs supported by immobile femur and a knee-driven Walk". BL means "Bellow lungs".

• Airsacs are known in many different theropods, as well as in birds, which most scientists believe are descendants of dinosaurus. Air sacs are found in the primitive Tawa hallae,^[1] the abelisaurid Majungasaurus,^[2] as well as Allosauroids like Aerosteon.^[3] There is also evidence for respiratory systems like penguinss in Deinonychosaurians.^[4] The primitive bird Archaeopteryx also had airsacs (Bonde and Christiansen, 2000).

• It is very likely that Deinonychosaurians had airsacs. We don't know whether Deinonychosauria had a walking/breathing system with immobile thighbones, ASW (like birds) or movable thighbones. However, some people suggsest coeluosaurs had the same type of leg movement as birds ("kneedriven walking").^[5]

• Bellow lungs are lungs like our own, which alternately is filled with air, and thereafter emptied, after which you take a new breath. This type of lungs exist in mammals, most reptiles, and most amphibians (although some frogs get their oxygen through the skin). There is no evidence for airsacs in Ornithischia, so the likely had bellow lungs.

References.=

1. ↑ (see the video at http://www.nsf.gov/news/special_reports/tawa/)
2. ↑ (Claessens & O'connor, 2006).
3. ↑ Alcober O.A, Sereno P.C, Larsson H.C.E et.al (2008), "Evidence for Avian Intrathoracic Air Sacs in a New Predatory Dinosaur from Argentina", Public Library of Science Journals.
4. ↑ http://www.stumbleupon.com/su/20q5Z4/news.bbc.co.uk/2/hi/science/nature/7081166.stm
5. ↑ http://www.geol.umd.edu/~tholtz/G104/lectures/104coelur.html.