Janenschia

''Janenschia'' (named after Werner Janensch) is a large herbivorous sauropod dinosaur from the Late Jurassic Tendaguru Formation of Lindi Region, Tanzania around 155 million years ago.

Discovery and naming

''Janenschia'' has had a convoluted nomenclatural history. In 1907, Eberhard Fraas at "site P", nine hundred metres to the southeast of Tendaguru Hill, discovered two skeletons of gigantic sauropods. They were designated as "Skeleton A" and "Skeleton B". The fossils were transported to the collection of the '' Stuttgarter Naturaliensammlung'' in Stuttgart, Germany. Fraas in 1908 decided to name both skeletons as different species of one genus, ''Gigantosaurus''. Skeleton A became ''Gigantosaurus africanus'' and skeleton B became ''Gigantosaurus robustus''. The latter species was based on the holotype partial skeleton SMNS 12144, consisting of a right hindlimb. The specific name was inspired by the heavy build of the animal. While doing so, Fraas knew full well that the name ''Gigantosaurus'' was already preoccupied by another taxon: '' Gigantosaurus megalonyx'', named by Harry Govier Seeley in 1869. Fraas thought his actions could be justified by the fact that the description by Seeley had been limited and that the material of ''G. megalonyx'' had since been referred to another genus, '' Ornithopsis'', by Richard Lydekker.

In 1911, Richard Sternfeld renamed ''Gigantosaurus'' Fraas 1908 into ''Tornieria'', pointing out that Fraas's arguments had been irrelevant. ''Tornieria africana'' became the type species of the new genus. ''G. robustus'' was placed in ''Tornieria'', as ''T. robusta''. Sternfeld's move was not well received in Germany, as he had acted without consent of the ailing Fraas. In 1922, Werner Janensch, who at the Tendaguru had collected additional material, in an article describing the hand of the animal announced that he would keep using the name ''Gigantosaurus robustus''. He claimed that ''G. megalonyx'' was a forgotten ''nomen oblitum'' and that the rules of the zoological nomenclature should be disregarded if they caused instability by replacing a well-known name by a completely new one. At the same time he synonymized ''Tornieria'' with ''Barosaurus'' as regarded its type species which then became a ''Barosaurus africanus''.Janensch, W., 1922, "Das Handskelett von ''Gigantosaurus robustus'' und ''Brachiosaurus brancai'' aus den Tendaguru-Schichten Deutsch-Ostafrikas", ''Centralblatt für Mineralogie, Geologie und Paläontologie'' 1922: 464–480 Janensch, for the remainder of his career, would consistently apply the name ''Gigantosaurus robustus''. In 1928, Sidney Henry Haughton exceptionally assigned ''Tornieria robusta'' to ''Barosaurus'' also, as a ''Barosaurus robustus''.

In 1930, Baron Franz Nopcsa rejected Janensch's arguments. He admitted that Sternfeld had been discourteous but pointed out that the ICZN only in 1927 recommended that the original author should be involved in such name changes. It would thus be absurd to object to an article written in 1911 — and in any case the lack of courtesy had no bearing on the validity of the name. Nopcsa had found several later mentions of ''G. megalonyx'', which thus had not been a ''nomen oblitum''. Furthermore, ''Gigantosaurus robustus'' had prior to 1922 not exactly been a well-known name itself. Distasteful as it might be, Nopcsa concluded, it was inevitable to consider ''Tornieria'' to be a valid name. SMNS 12144 was subsequently referred to ''Tornieria'' by other authors.

In 1991, German palaeontologist Rupert Wild of the Stuttgart Museum of Natural Sciences clarified the taxonomic status of ''G. robustus'', by concluding that it was generically distinct from ''Tornieria''. He renamed it ''Janenschia'' in honor of Werner Janensch, who had studied the vertebrate fauna from Tendaguru. ''Janenschia'' was placed in the family Titanosauridae, making it the oldest member of Titanosauria.

A number of specimens formerly assigned to ''Janenschia'' have been recognized as distinct genera. Two anterior dorsal vertebrae, and a possible posterior cervical vertebra, previously referred to the genus, were named ''Tendaguria'' in 2000. On the other hand, the caudal vertebral series MB.R.2091.1–30 does not overlap with SMNS 12144 and instead represents the first taxon of Mamenchisauridae from outside Asia, '' Wamweracaudia''. Recent cladistic analysis places ''Janenschia'' as a non-titanosauriform sauropod.

References

{{Taxonbar, from=Q133039

Macronaria
Dinosaur genera
Kimmeridgian dinosaurs
Tendaguru Formation
Fossil taxa described in 1991
Dinosaurs of Tanzania