A bony connection signals laryngeal echolocation in bats

Area of Science:

• Comparative anatomy
• Evolutionary biology
• Bioacoustics

Background:

• Echolocation, used by bats to navigate, is not universal among species.
• Most bats use laryngeal echolocation, but some Pteropodidae (fruit bats) use tongue clicks.
• The stylohyal bone's articulation with the tympanic bone is key to understanding echolocation origins.

Purpose of the Study:

• To identify a distinct anatomical marker for laryngeal echolocation in bats.
• To investigate the evolutionary history of echolocation in bats, including fossil species.
• To differentiate between laryngeal and non-laryngeal echolocation mechanisms.

Main Methods:

• Micro-computed tomography (CT) scans of 35 bats from 26 species.
• Analysis of the stylohyal bone's articulation with the tympanic bone.
• Comparative morphological analysis across diverse bat families.

Main Results:

• Proximal articulation of the stylohyal bone with the tympanic bone consistently identifies laryngeal echolocators.
• This articulation is often fused in bats using laryngeal echolocation.
• The fossil bat Onychonycteris finneyi may have used laryngeal echolocation based on its stylohyal-tympanic morphology.

Conclusions:

• Stylohyal-tympanic bone articulation provides a reliable anatomical character for identifying laryngeal echolocating bats.
• This finding challenges previous assumptions about the echolocation capabilities of early bats like Onychonycteris finneyi.
• The study offers new insights into the evolution and timing of flight and echolocation in bats.