Why doesn't the elephant have a pleural space?
The elephant is the only mammal whose pleural space is obliterated by connective tissue. This has been known for 300 years but never explained. The elephant is also the only animal that can snorkel at depth. The resulting pressure differences require changes in the pleural membranes and pleural space.
West
John B
JB
Department of Medicine, University of California San Diego, La Jolla, California 92093-0623, USA.
D000818:Animals; D005075:Biological Evolution; D004606:Elephants / Q000033:anatomy & histology* / Q000502:physiology*; D009666:Nose / Q000033:anatomy & histology; D010994:Pleura / Q000033:anatomy & histology*; D013550:Swimming / Q000502:physiology*