The taxonomic history of Plateosaurus is "long and confusing", a "chaotic tangle of names".
As of 2011, only two species are universally accepted as valid: the type species P. engelhardti and P. gracilis, previously assigned to its own genus Sellosaurus.
British palaeontologist Peter Galton showed clearly that all cranial material from Trossingen, Halberstadt and Frick pertains to one species.
Moser performed the most extensive and detailed investigation of all plateosaurid material from Germany and Switzerland, concluding that all Plateosaurus and most other prosauropod material from the Keuper stems from the same species as the type material of Plateosaurus engelhardti.
Moser considered Sellosaurus to be the same genus as Plateosaurus, but did not discuss whether S. gracilis and P. engelhardti belong to the same species.
Palaeontologist Adam Yates of the University of the Witwatersrand cast further doubt on the generic separation.
He included the type material of Sellosaurus gracilis in Plateosaurus as P. gracilis and reintroduced the old name Efraasia for some material that had been assigned to Sellosaurus.
In 1926, von Huene had already concluded the two genera were the same.

Yates has cautioned that P. gracilis may be a metataxon, which means that there is neither evidence that the material assigned to it is monophyletic (belongs to one species), nor that it is paraphyletic (belongs to several species).
This is the case because the holotype of P. (Sellosaurus) gracilis has no skull, and the other specimens consist of skulls and material that overlaps too little with the holotype to make it certain that it belongs to the same taxon.
It is therefore possible that the known material contains more species belonging to Plateosaurus.

Some scientists regard other species as valid as well, for example P. erlenbergensis.
Such works, however, ignore Moser (2003), the publication that shows the type series of P. engelhardti to be diagnostic, and other material to be referable to it.
The taxonomic history of Plateosaurus is "long and confusing", a "chaotic tangle of names". As of 2011, only two species are universally accepted as valid: the type species P. engelhardti and P. gracilis, previously assigned to its own genus Sellosaurus. British palaeontologist Peter Galton showed clearly that all cranial material from Trossingen, Halberstadt and Frick pertains to one species. Moser performed the most extensive and detailed investigation of all plateosaurid material from Germany and Switzerland, concluding that all Plateosaurus and most other prosauropod material from the Keuper stems from the same species as the type material of Plateosaurus engelhardti. Moser considered Sellosaurus to be the same genus as Plateosaurus, but did not discuss whether S. gracilis and P. engelhardti belong to the same species. Palaeontologist Adam Yates of the University of the Witwatersrand cast further doubt on the generic separation. He included the type material of Sellosaurus gracilis in Plateosaurus as P. gracilis and reintroduced the old name Efraasia for some material that had been assigned to Sellosaurus. In 1926, von Huene had already concluded the two genera were the same.
Yates has cautioned that P. gracilis may be a metataxon, which means that there is neither evidence that the material assigned to it is monophyletic (belongs to one species), nor that it is paraphyletic (belongs to several species). This is the case because the holotype of P. (Sellosaurus) gracilis has no skull, and the other specimens consist of skulls and material that overlaps too little with the holotype to make it certain that it belongs to the same taxon. It is therefore possible that the known material contains more species belonging to Plateosaurus.
Some scientists regard other species as valid as well, for example P. erlenbergensis. Such works, however, ignore Moser (2003), the publication that shows the type series of P. engelhardti to be diagnostic, and other material to be referable to it.
Plateosaurus