Editing Diplodocidae (section)

===Diet and feeding===
Their teeth were only present in the front of the mouth, and looked like pencils or pegs. They probably used their teeth to crop off food, without chewing, and relied on [[gastrolith]]s (gizzard stones) to break down tough [[plant]] fibers (similar to modern [[bird]]s).
Diplodocines have highly unusual teeth compared to other sauropods. The crowns are long and slender, and elliptical in cross-section, while the apex forms a blunt, triangular point.<ref name="Upchurch2000"/> The most prominent wear facet is on the apex, though unlike all other wear patterns observed within sauropods, diplodocine wear patterns are on the labial (cheek) side of both the upper and lower teeth.<ref name="Upchurch2000"/> 
[[File:Seismosaurus skull.jpg|left|thumb|Seismosaurus (=Diplodocus)]]
This implies that the feeding mechanism of ''Diplodocus'' and other diplodocids was radically different from that of other sauropods. Unilateral branch stripping is the most likely feeding behavior of ''Diplodocus'',<ref name="Norman1985"/><ref name="Dodson1990"/><ref name="BarrettUpchurch1994"/> as it explains the unusual wear patterns of the teeth (coming from tooth–food contact). In unilateral branch stripping, one tooth row would have been used to strip foliage from the stem, while the other would act as a guide and stabilizer. With the elongated preorbital (in front of the eyes) region of the skull, longer portions of stems could be stripped in a single action.<ref name="Upchurch2000"/> Also, the palinal (backwards) motion of the lower jaws could have contributed two significant roles to feeding behaviour: 1) an increased gape, and 2) allowed fine adjustments of the relative positions of the tooth rows, creating a smooth stripping action.<ref name="Upchurch2000"/>

Young ''et al.'' (2012) used biomechanical modelling to examine the performance of the diplodocine skull. It was concluded that the proposal that its dentition was used for bark-stripping was not supported by the data, which showed that under that scenario, the skull and teeth would undergo extreme stresses. The hypotheses of branch-stripping and/or precision biting were both shown to be biomechanically plausible feeding behaviors.<ref name="Young2012"/> Diplodocine teeth were also continually replaced throughout their lives, usually in less than 35 days, as was discovered by Michael D'Emic ''et al.'' Within each tooth socket, as many as five replacement teeth were developing to replace the next one. Studies of the teeth also reveal that it preferred different vegetation from the other sauropods of the Morrison, such as ''Camarasaurus''. This may have better allowed the various species of sauropods to exist without competition.<ref name="D'Emic2013"/>