| Janenschia | |
|---|---|
 | |
| Janenschiahumerus,radius andulna at theMuseum für Naturkunde, Berlin | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Clade: | †Neosauropoda |
| Clade: | †Macronaria |
| Genus: | †Janenschia Wild, 1991 |
| Species: | †J. robusta |
| Binomial name | |
| †Janenschia robusta (Fraas, 1908) | |
Janenschia (named afterWerner Janensch) is agenus of large herbivoroussauropoddinosaur from the LateJurassic (around 155 to 145 million years ago)Tendaguru Formation ofLindi Region,Tanzania.
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 theStuttgarter Naturaliensammlung inStuttgart,Germany. Fraas in 1908 decided to name both skeletons as different species of one genus:Gigantosaurus. Skeleton A becameGigantosaurus africanus and skeleton B becameGigantosaurus robustus. The latter species was based on theholotype partial skeletonSMNS 12144, consisting of a right hindlimb. Thespecific name was inspired by the heavy build of the animal.[1] While doing so, Fraas knew full well that the nameGigantosaurus was already preoccupied by another taxon:Gigantosaurus megalonyx, named byHarry 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 ofG. megalonyx had since been referred to another genus,Ornithopsis, byRichard Lydekker.[2][3][4][5][6]
In 1911,Richard Sternfeld renamedGigantosaurus Fraas 1908 toTornieria, pointing out that Fraas's arguments had been irrelevant.Tornieria africana became the type species of the new genus.[7]G. robustus was placed inTornieria, asT. robusta. Sternfeld's move was not well received in Germany, as he had acted without consent of the ailing Fraas. In a 1922 article describing the hand of the animal,Werner Janensch, who at the Tendaguru had collected additional material, announced that he would keep using the nameGigantosaurus robustus. He claimed thatG. megalonyx was a forgottennomen 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 synonymizedTornieria withBarosaurus as regarded its type species which then became aBarosaurus africanus.[8] Janensch, for the remainder of his career, would consistently apply the nameGigantosaurus robustus. In 1928,Sidney Henry Haughton exceptionally assignedTornieria robusta toBarosaurus also, as aBarosaurus robustus.[9]
In 1930, BaronFranz 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 ofG. megalonyx, which thus had not been anomen oblitum. Furthermore,Gigantosaurus robustus had not exactly been a well-known name itself, prior to 1922. Distasteful as it might be, Nopcsa concluded, it was inevitable to considerTornieria to be a valid name.[10] SMNS 12144 was subsequently referred toTornieria by other authors.[11][12][13][14]
In 1991, German palaeontologistRupert Wild of theStuttgart Museum of Natural Sciences clarified the taxonomic status ofG. robustus by concluding that it was generically distinct fromTornieria. He renamed itJanenschia in honor of Werner Janensch, who had studied the vertebrate fauna from Tendaguru.Janenschia was placed in the familyTitanosauridae, making it the oldest member ofTitanosauria.[15]
A number of specimens formerly assigned toJanenschia have been recognized as distinct genera. Two anterior dorsal vertebrae, and a possible posterior cervical vertebra, previously referred to the genus, were namedTendaguria in 2000.[16] On the other hand, the caudal vertebral seriesMB.R.2091.1–30 does not overlap with SMNS 12144 and instead represents the first taxon ofMamenchisauridae from outside Asia,Wamweracaudia.[17][18] Recent cladistic analysis placesJanenschia as a non-titanosauriform sauropod.[19][18]
