Plateosaurus

Plateosaurus (probably meaning "broad lizard", often mistranslated as "flat lizard") 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. Plateosaurus is a basal (early) sauropodomorph dinosaur, a so-called "prosauropod". The type species is Plateosaurus trossingensis; before 2019, that honor was given to Plateosaurus engelhardti, but it was ruled as undiagnostic (i.e. indistinguishable from other dinosaurs) by the ICZN. Currently, there are three valid species; in addition to P. trossingensis, P. longiceps and P. gracilis are also known. 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 (invalid duplicate names) 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. The abundance of its fossils in Swabia, Germany, has led to the nickname Schwäbischer Lindwurm (Swabian lindworm).

Plateosaurus was a bipedal herbivore with a small skull on a long, flexible neck, sharp but plump plant-crushing teeth, powerful hind limbs, short but muscular arms and grasping hands with large claws on three fingers, possibly used for defence and feeding. Unusually for a dinosaur, Plateosaurus showed strong developmental plasticity: instead of having a fairly uniform adult size, fully grown individuals were between 4.8 and 10 metres (16 and 33 ft) long and weighed between 600 and 4,000 kilograms (1,300 and 8,800 lb). Commonly, the animals lived for at least 12 to 20 years, but the maximum life span is not known.

Despite the great quantity and excellent quality of the fossil material, Plateosaurus was for a long time one of the most misunderstood dinosaurs. Some researchers proposed theories that were later shown to conflict with geological and palaeontological evidence, but have become the paradigm of public opinion. Since 1980 the taxonomy (relationships), taphonomy (how the animals became embedded and fossilised), biomechanics (how their skeletons worked), and palaeobiology (life circumstances) of Plateosaurus have been re-studied in detail, altering the interpretation of the animal's biology, posture and behaviour.

In 1834, physician Johann Friedrich Engelhardt discovered some vertebrae and leg bones at Heroldsberg near Nuremberg, Germany.[2] Three years later German palaeontologist Hermann von Meyer designated them as the type specimen of a new genus, Plateosaurus.[2] Since then, remains of well over 100 individuals of Plateosaurus have been discovered at various locations throughout Europe.[3]

Map of important Plateosaurus localities. Red = likely type locality Heroldsberg, black = important sites with many and well-preserved specimens. Other localities in blue.[A]
Photograph of an articulated skeleton missing the head and tail, seen from above. The animal has the limbs strongly folded in a squatting posture, the arms are spread out with the palms facing up and inward. The body and neck curve to the right, with the body making a 40° curve and the neck a 110° curve. The trunk is compressed, which can be seen from the shoulder blades sticking straight up and the ribs being folded backwards. All sediment that is not necessary to keep the bones of the body and neck connected has been removed.
P. engelhardti, collection number F 33 of the Staatliches Museum für Naturkunde Stuttgart, Germany, in dorsal view. The skeleton was kept in articulation as found at Trossingen by Seemann in 1933. It has the typical folded hind limbs of most Plateosaurus finds. Unusually, the anterior body is not twisted to one side.[3]
Outdated 1912 life restoration by Otto Jaekel showing tripodal pose
Skull cast of P. gracilis
Photograph of the skull in side view, with a partial neck composed of seven vertebrae extending from it, seemingly articulated. However, the vertebrae are at a right angle, i.e. their neural spines point to what is to the left for the skull. Among each other they are articulated, forming a 110° curve, which the cervical ribs follow. Next to the fossil are explanatory signs, including a schematic drawing showing the skull openings and giving their names. The name shown is Plateosaurus quenstedti, a junior synonym of P. engelhardti.
P. engelhardti skull and neck (MB 1927.19.1) previously assigned to P. quenstedti and P. longiceps, at the Museum für Naturkunde, Berlin
Restoration of P. engelhardti
P. engelhardti skull cast, Royal Ontario Museum
Size comparison of four Plateosaurus specimens representing two species
Mounted P. engelhardti skeleton in Sauriermuseum, Frick
Life restoration of P. gracilis, formerly known as Sellosaurus gracilis
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.
Mounted cast of SMNS 13200. An example of the out-dated skeleton mounts in the State Museum of Natural History Stuttgart in quadrupedal posture. The shoulder girdle is in an anatomically infeasible position, the elbow is disarticulated, and the ribcage has the wrong shape, wide instead of high oval.
Mount of P. engelhardti GPIT/RE/7288, a nearly complete individual from Trossingen at the museum of the Institute for Geosciences of the Eberhard-Karls-University Tübingen, Germany. Anatomically, this mount created under the direction of Friedrich von Huene is one of the best in the world, epitomising the agile, bipedal and digitigrade view of Plateosaurus confirmed by recent research.
Restoration of P. engelhardti and contemporary animals from the Trossingen Formation
P. engelhardti, collection number MSF 23 of the Sauriermuseum Frick, Switzerland, in dorsal view. This is the most complete Plateosaurus skeleton from Frick.