SCHAUB, M.J.*; ZALISKO, E.J.; SCHAEFER, J.C.: Another Advantage of Long Sauropod Necks: Reaching Out and Over Hazardous Environments.
Long necks in sauropods may have diverse advantages. In addition to reaching up to browse on high vegetation, long necks permit sauropods to graze where they cannot easily stand, pass, or reach. Such restrictive environments include the margins and bottoms of aquatic systems. We tested the forces required to extract limbs from mud to estimate the difficulties encountered by a large sauropod struggling to move through saturated soil. Sauropod leg models consisted of PVC pipes (1.6-11.4 cm diameter) with attached end caps. Additional weight was added inside the tubes as needed to adjust each leg to a standard weight of 2.5 kg. Thus the legs varied only in their dimensions. Legs were submerged into a tub containing saturated potting soil to a depth of 45 cm. A pulley system was used to determine the force required to vertically extract each limb in a standard period of time. The results indicate that drag force increases at nearly the same rate as the radius of the leg. In addition to requiring greater forces for limb extraction, muddy environments pose other challenges. Saturated soils often consist of a moving, unstable substrate. Extracting limbs from deep mud likely required a degree of agility and flexibility beyond that found in large sauropods. Longer necks would allow these animals to graze at the margins of aquatic environments that they otherwise could not reach.