page_title: Plateosaurus
section_title: Posture and gait
hierarchical_section_title: Plateosaurus / Palaeobiology / Posture and gait
caption_attribution_description: Left lower arm and hand of Plateosaurus engelhardti IFGT "Skelett 2" from Trossingen, Germany on exhibit at the museum of the Institute for Geosciences of the Eberhard-Karls-University Tübingen, Germany. Mount created under the direction of Friedrich von Huene.
context_page_description: Plateosaurus is a genus of plateosaurid dinosaur that lived during the Late Triassic period, around 214 to 204 million years ago, in what is now Central and Northern Europe and Greenland, North America. Plateosaurus is a basal sauropodomorph dinosaur, a so-called "prosauropod". As of 2011, two species are recognised: the type species P. engelhardti from the late Norian and Rhaetian, and the slightly earlier P. gracilis from the lower Norian. However, others have been assigned in the past, and there is no broad consensus on the species taxonomy of plateosaurid dinosaurs. Similarly, there are a plethora of synonyms at the genus level.
  Discovered in 1834 by Johann Friedrich Engelhardt and described three years later by Hermann von Meyer, Plateosaurus was the fifth named dinosaur genus that is still considered valid. Although it had been described before Richard Owen formally named Dinosauria in 1842, it was not one of the three genera used by Owen to define the group, because at the time, it was poorly known and difficult to identify as a dinosaur. It is now among the dinosaurs best known to science: over 100 skeletons have been found, some of them nearly complete.
context_section_description: Practically every imaginable posture has been suggested for Plateosaurus in the scientific literature at some point. Von Huene assumed digitigrade bipedality with erect hind limbs for the animals he excavated at Trossingen, with the backbone held at a steep angle (at least during rapid locomotion). In contrast, Jaekel, the main investigator of the Halberstadt material, initially concluded that the animals walked quadrupedally, like lizards, with a sprawling limb position, plantigrade feet, and laterally undulating the body. Only a year later, Jaekel instead favoured a clumsy, kangaroo-like hopping, a change of heart for which he was mocked by German zoologist Gustav Tornier, who interpreted the shape of the articulation surfaces in the hip and shoulder as typically reptilian. Fraas, the first excavator of the Trossingen lagerstätte, also favoured a reptilian posture. Müller-Stoll listed a number of characters required for an erect limb posture that Plateosaurus supposedly lacked, concluding that the lizard-like reconstructions were correct. However, most of these adaptations are actually present in Plateosaurus.
  From 1980 on, a better understanding of dinosaur biomechanics, and studies by palaeontologists Andreas Christian and Holger Preuschoft on the resistance to bending of the back of Plateosaurus, led to widespread acceptance of an erect, digitigrade limb posture and a roughly horizontal position of the back. Many researchers were of the opinion that Plateosaurus could use both quadrupedal gaits (for slow speeds) and bipedal gaits (for rapid locomotion), and Wellnhofer insisted that the tail curved strongly downward, making a bipedal posture impossible. However, Moser showed that the tail was in fact straight.
  The bipedal-quadrupedal consensus was changed by a detailed study of the forelimbs of Plateosaurus by Bonnan and Senter (2007), which clearly showed that Plateosaurus was incapable of pronating its hands. The pronated position in some museum mounts had been achieved by exchanging the position of radius and ulna in the elbow. The lack of forelimb pronation meant that Plateosaurus was an obligate (i.e. unable to walk in any other way) biped. Further indicators for a purely bipedal mode of locomotion are the great difference in limb length (the hind limb is roughly twice as long as the forelimb), the very limited motion range of the forelimb, and the fact that the centre of mass rests squarely over the hind limbs.
  Plateosaurus shows a number of cursorial adaptations, including an erect hind limb posture, a relatively long lower leg, an elongated metatarsus and a digitigrade foot posture. However, in contrast to mammalian cursors, the moment arms of the limb extending muscles are short, especially in the ankle, where a distinct, moment arm-increasing tuber on the calcaneum is missing. This means that in contrast to running mammals, Plateosaurus probably did not use gaits with aerial, unsupported phases. Instead, Plateosaurus must have increased speed by using higher stride frequencies, created by rapid and powerful limb retraction. Reliance on limb retraction instead of extension is typical for non-avian dinosaurs.
caption: Dorsal view of left lower arm and hand of P. engelhardti ("Skelett 2") at the museum of the Institute for Geosciences of the Eberhard-Karls-University Tübingen, Germany. The shape of the radius dictates that the hand could not be pronated (turned palm down), and thus not play a role in locomotion.
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