Table 1. Description of kinematic variables calculated from landmark data for comparisons of feeding and climbing behaviors by Sicyopterus stimpsoni.

Kinematic variable	Description
Cranial elevation angle	Rotation angle of a vector between the anterior edge of the neurocranium (point 18) and the insertion of epaxial muscles on the neurocranium (point 20), relative to the orientation of this vector at the beginning of the cycle
Premaxillary protrusionangle	Rotation angle of a vector between the anterior tip of the upper lip (point 15) and the anterior edge of the neurocranium (point 18), relative to the orientation of this vector at the beginning of the cycle
Premaxillary protrusionlength	Distance that the anterior tip of the upper lip (point 15) has extended during the cycle, relative to its position at the start of the cycle
Hyoid retraction angle	Angle between a vector running from the midpoint of the hyoid arch (point 8) to a stationary point calculated midway between the bases of the left and right pectoral fins (average of points 12 and 13), and a vector running from the midpoint of the hyoid arch (point 8) to the right opercular landmark (point 11)
Hyoid retraction length	Change in the distance between the midpoint of the hyoid arch (point 8) and a stationary point calculated midway between the bases of the left and right pectoral fins (average of points 12 and 13), relative to this distance at the start of the cycle
Mandibular retraction length	Change in distance from the anterior tip of the mandible (point 3) to a stationary point calculated midway between the bases of the left and right pectoral fins (average of points 12 and 13), relative to this distance at the start of the cycle
Opercular expansion length	Distance between left and right opercular landmark tips (points 10 and 11)
Oral sucker area	Geometric model of the area enclosed by the oral sucker in ventral view; see Fig. 2 for calculation