Forelimb skeletal morphology and flight mode evolution in pelecaniform birds

Area of Science:

• Comparative anatomy
• Functional morphology
• Avian paleontology

Background:

• Pelecaniform birds exhibit diverse flight modes, from soaring to continuous flapping.
• Understanding the relationship between skeletal morphology and flight mechanics is crucial for avian evolution studies.

Purpose of the Study:

• To investigate how forelimb skeletal morphology in pelecaniform birds varies with body size and flight mode.
• To determine if phylogenetic history influences allometric scaling patterns of wing elements.
• To identify specific skeletal features associated with different flight modes.

Main Methods:

• Measurements of wing elements (length, diameter) from 50 pelecaniform species.
• Allometric and discriminant function analyses (DFAs) were performed, considering phylogenetic relationships (independent contrasts).
• Flight modes were categorized based on habitual behaviors: soar, flap-glide, and continuous flap.

Main Results:

• Phylogenetically corrected analyses revealed positive allometry only in ulna length; other wing elements showed isometry.
• Ahistorical allometric analyses yielded different results, highlighting the importance of phylogenetic control.
• Discriminant function analysis significantly separated flight mode groups, with carpometacarpal dimensions (dorsoventral diameter, total length) being key discriminators.

Conclusions:

• Pelecaniform wing bones, particularly the carpometacarpus, exhibit specific morphologies adapted to distinct flight modes.
• Skeletal adaptations reflect the functional demands of aerial locomotion and flight control in pelecaniforms.
• Phylogenetic analysis is essential for accurate interpretation of allometric scaling in avian skeletal morphology.