Files in this Data Supplement:

• Supplemental Movie 1: Terrapene carolina breathing at rest. -

  Terrapene carolina (individual 03) breathing during a brief pause between locomotor bouts. This clip shows three simultaneously recorded images: the top portion of the screen shows light video, the middle shows X-ray video and the bottom shows ventilatory airflow. In this lateral view, the animal is wearing a custom-built pneumotach mask (appears dark in X-ray and light in regular video), which is attached to a differential pressure transducer and calibrated for airflow rates and volumes. The light area in the middle of the animal in the X-ray images is the air-filled lungs. A metal marker has been glued to the skin just superficial to the abdominal muscles which can be seen to move during breathing. In the airflow trace, zero airflow (the flat line in the middle) indicates no breathing, exhalation occurs when the trace is above zero and inhalation occurs when the trace is below zero. Note: the y-axis (voltage) scale of the breathing trace changes during the course of the clip.

• Supplemental Movie 2: Terrapene carolina breathing during locomotion. -

  The turtle (individual 03) takes 6 breaths and 20 strides during a locomotor bout which lasts approx. 25·s. This clip shows three simultaneously recorded images: the top portion of the screen shows light video, the middle shows X-ray video and the bottom shows ventilatory airflow. In this lateral view, the animal is wearing a custom-built pneumotach mask (appears dark in X-ray and light in regular video) which is attached to a differential pressure transducer and calibrated for airflow rates and volumes. The light area in the middle of the animal in the X-ray images is the air-filled lungs. A metal marker has been glued to the skin just superficial to the abdominal muscles which can be seen to move during breathing. In the airflow trace, zero airflow (the flat line in the middle) indicates no breathing, exhalation occurs when the trace is above zero and inhalation occurs when the trace is below zero. For this bout of locomotion, mean speed is 0.091 m s^–1; stride frequency is 0.8 strides s^–1; and stride length is 0.114 m s^–1.