New paper: pneumatic diverticula in the neural canals of birds

Morphological variation in paramedullary airways; yellow = spinal cord, green = diverticula. The spectrum of variation is discretized into four groups: i , branches of intertransverse diverticula contact spinal cord at intervertebral joints; ii , branches of intertransverse diverticula extend partially into the vertebral canal, but remain discontinuous;