Review of the cetacean nose: form, function, and evolution

Area of Science:

• Paleontology
• Evolutionary Biology
• Comparative Anatomy

Background:

• Cetaceans exhibit unique nasal anatomical modifications, including the posterior placement of external nares.
• These changes are linked to functional shifts like the evolution of echolocation in odontocetes and reduced olfaction in Neoceti.

Purpose of the Study:

• To review the anatomical and embryological development of the cetacean nose.
• To propose a sequence of evolutionary transformations in the cetacean nose during the transition to aquatic life.
• To discuss the functional implications of these nasal modifications.

Main Methods:

• Review of anatomical and embryological data of cetacean noses.
• Analysis of evolutionary transformations from terrestrial to aquatic lifestyles.
• Examination of genetic changes, including olfactory receptor gene reduction.

Main Results:

• Basilosaurids and later whales show reduced nasal turbinates.
• Neoceti (odontocetes and mysticetes) exhibit significant reduction of major olfactory structures (ethmoturbinates, cribriform plate, maxilloturbinates).
• Odontocetes show further reduction and loss of olfactory structures, with modifications for biosonar sound production.

Conclusions:

• The evolution of the cetacean nose involved a sequence of anatomical and functional changes, including posterior nares migration and reduced olfaction.
• These modifications reflect genetic changes and are crucial for adaptation to an aquatic environment and specialized functions like echolocation.
• While odontocetes largely lost olfaction, mysticetes retain some olfactory capabilities.