Concealed weapons: erectile claws in African frogs.

Area of Science:

• Vertebrate Paleontology
• Amphibian Biology
• Functional Morphology

Background:

• Vertebrate claws are crucial for behavior and typically consist of keratin.
• Keratinous claws are uncommon in amphibians, suggesting independent evolution from amniotes.
• Existing amphibian claws differ in microstructure and origin from amniote claws.

Purpose of the Study:

• To investigate the unique defensive claw structure in certain African frogs.
• To describe the morphology and functional mechanism of these non-keratinous claws.
• To compare these novel claws with known vertebrate claw types.

Main Methods:

• Microstructural analysis of the African frog claw.
• Skeletal examination of terminal phalanges and associated bony nodules.
• Functional assessment of claw erection and skin penetration mechanism.

Main Results:

• African frogs possess unique, non-keratinous defensive claws.
• These claws feature sectorial terminal phalanges that cut through skin.
• A neomorphic bony nodule and collagen-rich tissue facilitate claw erection and skin piercing.

Conclusions:

• The African frog claw represents a novel vertebrate claw type, distinct from keratinous claws.
• This unique mechanism of piercing the skin for functionality is unprecedented in vertebrates.
• The findings highlight the diverse evolutionary pathways of defensive structures in amphibians.