Dinosaurs: A new, ‘hip’ way to breathe

Ornithischians, one of the three major groups of dinosaurs, developed a unique mechanism to ensure airflow in the lungs.
1 figure

Figures

Hip evolution in ornithischians.

A simplified phylogenetic tree illustrating the evolution of the various components of the ornithischian hip from the Triassic Period (bottom) to the Cretaceous Period (top; app: anterior pubic process; hs: hip socket or acetabulum; il: ilium; is: ischium; ps: pubic shaft). The hypothetical ornithischian ancestor (full skeleton, bottom right) lacks an anterior pubic process, which is a projection of the pubis bone pointing towards the head. As Radermacher et al. demonstrate, this structure was present in Heterodontosaurus, an early ornithischian which walked on two legs. During evolution, the process grew bigger, and is thought to have helped anchor a muscle responsible for pelvic bellows, a new breathing mechanism which could have persisted even when ornithischians started to move on four legs (like, for example, Stegosaurus). All hips are oriented in the same direction and are not to scale. Estimated dates given in millions of years (Ma) and taken from Cohen et al., 2013.

Image credit: Christopher Brochu created the skeletons of Heterodontosaurus and Stegosaurus.

Download links

A two-part list of links to download the article, or parts of the article, in various formats.

Downloads (link to download the article as PDF)

Open citations (links to open the citations from this article in various online reference manager services)

Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)

  1. Marc R Spencer
(2021)
Dinosaurs: A new, ‘hip’ way to breathe
eLife 10:e70947.
https://doi.org/10.7554/eLife.70947