A surrogate forelimb: Evolution, function and development of the avian cervical spine

Area of Science:

• Avian Anatomy and Paleontology
• Evolutionary Biology
• Biomechanics

Background:

• The avian neck functions as a surrogate forelimb, enabling complex interactions with the environment.
• Birds exhibit significant diversity in neck morphology, from vertebral count to individual vertebra structure.
• Current knowledge of avian neck anatomy and function is primarily based on commercially relevant species.

Purpose of the Study:

• To review the development, function, and evolution of the avian cervical spine.
• To highlight the disparity between known morphofunctional aspects and the drivers of neck variation.
• To identify knowledge gaps concerning the evolutionary history and macroevolutionary impact of the avian neck.

Main Methods:

• Review of existing literature on avian neck musculoskeletal anatomy, kinematics, and development.
• Synthesis of recent studies quantifying morphological variation and skeletal integration in avian necks.
• Identification of areas requiring future research for a comprehensive understanding.

Main Results:

• The avian neck's musculoskeletal anatomy, kinematics, and development are documented, though with limited species diversity.
• Quantification of extant morphological variation and integration patterns provides insights into functional constraints.
• The evolutionary history and macroevolutionary consequences of avian cervical spine diversity remain largely unexplored.

Conclusions:

• Significant gaps exist in understanding the drivers and evolutionary history of avian neck diversity.
• Further research is needed across a broader range of avian taxa to elucidate neck development, kinematics, and evolutionary impact.
• A comprehensive understanding of the avian cervical spine is essential for explaining avian diversification and success.