So I suppose I'm back to the habitat question. I'm wondering if long necks are correlated with seasonally arid environments, where being able to reach any available foliage in (comparatively unaffected) riparian zones would be critical to survival during the dry season and/or periods of prolonged or irregular drought. Conversely, one could then predict that the shortest-necked sauropods would tend to be found in the areas least subject to seasonal aridity.