MOBILITY OF THE AXIAL REGIONS IN A CAPTIVE AMAZON RIVER DOLPHIN (INIA GEOFFRENSIS) - Biology, Evolution and Conservation of River Dolphins Within South America and Asia - page 71

Chapter 4
M OBILITY OF THE A XIAL R EGIONS IN A
C APTIVE A MAZON R IVER D OLPHIN
( I NIA GEOFFRENSIS )
Timothy D. Smith 1, 3  and Anne M. Burrows 2, 4
1 School of Physical Therapy, Slippery Rock University, Slippery Rock PA, 16057 USA
2 Department of Anthropology, University of Pittsburgh, Pittsburgh, PA, USA
3 Section of Mammals, Carnegie Museum of Natural History; Pittsburgh, PA, USA
4 Department of Physical Therapy, Duquesne University, Pittsburgh, PA, USA
A BSTRACT
Here we analyze mobility of axial regions in a captive Amazon River dolphin (Inia
geoffrensis), specifically regarding lateral movements of the neck and torso. Still images
from video recordings of the swimming dolphin were extracted and analyzed using Scion
Image software. Lateral movements of the neck can reach nearly a right angle (deviating
from the thoracic region by up to at least 84 degrees). Much more lateral mobility is seen
in the torso, with most occurring in the posterior torso (presumably at intervertebral joints
in the caudal vertebrae). In sum, the lateral mobility allows this captive dolphin to touch
rostrum to tail by lateral bending. Osteological correlates of lateral mobility in this
species are also reviewed in this chapter. Based on behavioral descriptions in the
literature, the extreme lateral mobility observed in this captive animal are likely
representative of the species in general, and relates to locomotion in a complex
environment. Further investigations must determine whether this mobility, and the
morphological features that permit it, are unique adaptations or primitive features that
characterized an ancestral condition.
Keywords : caudal, cervical, Inia geoffrensis , lumbar, thoracic, vertebra.
 [e-mail]