Suuwassea

Taxobox
name = "Suuwassea"
fossil_range = Late Jurassic
regnum = Animalia
phylum = Chordata
classis = Sauropsida
superordo = Dinosauria
ordo = Saurischia
subordo = Sauropodomorpha
superfamilia = Diplodocoidea
genus = "Suuwassea"
genus_authority = Harris & Dodson, 2004
subdivision_ranks=Species
subdivision=
*"S. emilieae" Harris & Dodson, 2004 (type)

"Suuwassea" (meaning "ancient thunder") is a genus of diplodocoid sauropod dinosaur found in the Upper Jurassic strata of the Morrison Formation, located in southern Carbon County, Montana, USA. The fossil remains were recovered in a series of expeditions during a period spanning the years 1999 and 2000, described by J.D. Harris and Peter Dodson in 2004. They consist of a disarticulated but associated partial skeleton, including partial vertebral series and limb bones.

Since the fossil was found in an ancestral territory of the Native American Crow tribe, the etymology of the generic name is derived from a term in their language, "suuwassa", “the first thunder heard in Spring”. The root "suu", meaning “thunder” and "wassa", “ancient”, are a nod to the “thunder lizard” moniker often applied to sauropods. The specific epithet honours the deceased sponsor of the expeditions that recovered the fossil.

"Suuwassea" is a basal diplodocoid, estimated to have been 14 to 15 meters long (46 to 49 ft), characterized by skull and axial skeleton features it shares with Diplodocidae and Dicraeosauridae though it is too primitive to pertain to any of the latter clades. The herbivore differs from dicraeosaurids in the unfused state of the frontal, and from diplodocids in the arrangement of bones around the foramen magnum, though it possesses a greater number of similarities with them than with clade Dicraeosauridae.

"S. emilieae"’s find is concurrent with other finds of medium-sized sauropods in Morrison Formation’s northern section contrary to the finds of large animals in the southern reaches. This size difference was possibly due to new environments created as the Middle Jurassic Sundance Sea retreated northward. This sauropod’s phylogenetic analysis puts in doubt a number of autapomorphic characters of both Diplodocidae and Dicraeosauridae, opening the possibility that these are plesiomorphies differentially retained by each family. The presence of dicraeosaurid characters on a Laurasian diplodocoid also raises the question of the origin and distribution of a purported ancestral diplodocoid: Laurasia, Gondwana, or both.

References

*Harris, J.D. and Dodson, P. (2004). "A new diplodocoid sauropod dinosaur from the Upper Jurassic Morrison Formation of Montana, USA." "Acta Palaeontologica Polonica 49 (2):" 197–210.