Janenschia robusta (Fraas, 1908)

D, Michael D. & Emic, 2012, The early evolution of titanosauriform sauropod dinosaurs, Zoological Journal of the Linnean Society 166 (3), pp. 624-671 : 648-649

JANENSCHIA ROBUSTA ( WILD, 1991)

Janenschia is an important taxon because of its proposed titanosaur affinities (e.g. McIntosh, 1990; Upchurch, 1995; Bonaparte, Heinrich & Wild, 2000; Wilson, 2002; Upchurch et al., 2004) and Late Jurassic age. Janenschia appears to be a titanosauriform based on the absence of a proximomedial triangular scar on the fibula (Appendix 3). Bonaparte et al. (2000) pointed out that the procoelous anterior caudal vertebrae possibly referable to Janenschia could not strongly attest to titanosaur affinities because this feature is also present in some diplodocoids and non-neosauropods (see also Whitlock et al., 2011). Upchurch (1995), Wilson (2002), and Upchurch et al. (2004) suggested titanosaur affinities for Janenschia on the basis of its robust forelimb bones and a raised ulnar olecranon process. However, similarly robust bones and a raised olecranon are found in some non-titanosaurs or non-titanosauriforms such as Tehuelchesaurus according to this analysis, and these features were not found to be titanosaur synapomorphies in this study.

Likewise, Royo-Torres & Cobos (2009) presented evidence that some material referred to Janenschia pertains to non-neosauropods. Furthermore, several features of Janenschia are inconsistent with its placement within Titanosauria, Somphospondyli, or even Titanosauriformes: ulnar proximal arms subequally developed, the lack of an embracing proximal tibia and fibula, and a divided posterior fossa on the astragalus (Appendix 3). Curry Rogers (2005) included Janenschia in a cladistic analysis of titanosaurs, but a strict consensus of those results did not resolve its relationships amongst titanosauriforms. The only other cladistic analysis that included Janenschia recovered it as a non-titanosaur ( Carballido et al., 2011b). The titanosaur affinities of Janenschia cannot be substantiated at present.