is still used as the group name. In 2011, John Whitlock published a study that placed Apatosaurus a more basal diplodocid, sometimes less basal than Supersaurus. Cladogram of the Diplodocidae after Tschopp, Mateus, and Benson (2015). Paleobiology It was believed throughout the 19th and early 20th centuries that sauropods like Apatosaurus were too massive to support their own weight on dry land. It was theorized that they lived partly submerged in water, perhaps in swamps. More recent findings do not support this; sauropods are now thought to have been fully terrestrial animals. A study of diplodocid snouts showed that the square snout, large proportion of pits, and fine, subparallel scratches of the teeth of Apatosaurus suggests it was a ground-height, nonselective browser. It may have eaten ferns, cycadeoids, seed ferns, horsetails, and algae. Stevens and Parish (2005) speculate that these sauropods fed from riverbanks on submerged water plants. A 2015 study of the necks of Apatosaurus and Brontosaurus found many differences between them and other diplodocids, and that these variations may have shown that the necks of Apatosaurus and Brontosaurus were used for intraspecific combat. Various uses for the single claw on the forelimb of sauropods have been proposed. One suggestion is that they were used for defense, but their shape and size make this unlikely. It was also possible they were for feeding, but the most probable use for the claw was grasping objects such as tree trunks when rearing. Trackways of sauropods like Apatosaurus show that they may have had a range of around per day, and that they could potentially have reached a top speed of per hour. The slow locomotion of sauropods may be due to their minimal muscling, or to recoil after strides. A trackway of a juvenile has led some to believe that they were capable of bipedalism, though this is disputed. Neck posture Diplodocids like Apatosaurus are often portrayed with their necks held high up in the air, allowing them to browse on tall trees. Some studies state diplodocid necks were less flexible than previously believed, because the structure of the neck vertebrae would not have allowed the neck to bend far upward, and that sauropods like Apatosaurus were adapted to low browsing or ground feeding. Other studies by Taylor find that all tetrapods appear to hold their necks at the maximum possible vertical extension when in a normal, alert posture; they argue