In defence of parallel interphalangeal lines

Abstract

Virtually parallel lines can be drawn through the interphalangeal joints and across the ungual tips of every tetrapod manus or pes, including wings and flippers. Their presence indicates that phalanges operate in sets sharing common hinges, whether for walking (extension) or climbing (flexion). A recent paper has attempted to dismantle both the observation and utility of parallel interphalangeal lines. Here, I rebut those spurious arguments and report additional evidence.

Keywords:

• parallel interphalangeal lines
• hinge lines
• autopodia
• manus
• pes
• tetrapod