[D] Suuwassea emilieae [sG] [T]
Harris & Dodson, 2004
Jurassic Late ?Tithonian
Saurischia Sauropodomorpha Sauropoda Diplodocidae [Flagellicaudata]
Morrison Formation, Montana, US
14 -15 meter
Genus - Typespecies
Holotype and only known specimen
ANS 21122, Suuwassea is a relatively small diplodocoid. The genus name is derived from suuwassa, a compound of the Crow (Siouan) words *suu* \\\'thunder\\\' and *wassa* \\\'ancient\\\'. The compound means \\\'first thunder heard in spring\\\'. The species name, emilieae, honors the late Emilie deHellebranth, who funded the expeditions that recovered the specimen.
Suuwassea emilieae gen. et sp. nov. is diagnosed by numerous cranial, axial, and appendicular autapomorphies. The holotype consists of a premaxilla, partial maxilla, quadrate, braincase with partial skull roof, several partial and complete cranial and middle cervical, cranial dorsal, and caudal vertebrae, ribs, complete scapulocoracoid, humerus, partial tibia, complete fibula, calcaneus, and partial pes. It displays numerous synapomorphies of the Diplodocoidea, including characters of both the Diplodocidae (Apatosaurus + (Diplodocus + Barosaurus)) and Dicraeosaurinae (Dicraeosaurus + Amargasaurus).
Preliminary phylogenetic analysis
Preliminary phylogenetic analysis indicates that Suuwassea is a diplodocoid more derived than rebbachisaurids but in a trichotomy with both the Diplodocidae and Dicraeosauridae. Suuwassea represents the first well-supported, North American, non-diplodocid representative of the Diplodocoidea and provides new insight into the origins of both the Diplodocidae and Dicraeosaurinae.
Harris, Jerald D. (2006). The significance of Suuwassea emiliae (Dinosauria: Sauropoda) for flagellicaudatan intrarelationships and evolution. Journal of Systematic Palaeontology 4: 185-198.
\\\"Suuwassea emilieae is a recently described dinosaur taxon discovered in the Upper Jurassic Morrison Formation of the western United States and the only non-diplodocid flagellicaudatan (Dinosauria: Sauropoda) known from North America.
It retains sauropod symplesiomorphies that are unexpected in a Late Jurassic taxon and thus sheds light on the evolutionary origins of the Flagellicaudata. Despite being comparatively small, the holotype of Suuwassea demonstrates hallmarks of relatively advanced age.
A phylogenetic analysis of 30 taxa and 331 characters retains _Suuwassea_ in a trichotomy with the Diplodocidae (Apatosaurus + (Diplodocus + Barosaurus)) and Dicraeosaurinae (Dicraeosaurus + Amargasaurus). This lack of resolution is probably due to a combination of missing data, character conflict and poor incorporation of specimens referred to diplodocid taxa that differ from their holotype specimens and species holotypes.
Middle Jurassic palaeobiogeographical reconstructions conflict with the hypothetical distribution of flagellicaudatans in the Middle and Late Jurassic based on their phylogeny, implying that physical barriers, such as epeiric seas, were not responsible for limiting their initial radiation. The postparietal foramen shared by Suuwassea, Dicraeosaurus, Tornieria and Amargasaurus may correlate to preferred existence in near-shore, terrestrial environments.\\\"