''Suuwassea'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

dicraeosaurid Dicraeosauridae is a family of diplodocoid sauropods who are the sister group to Diplodocidae. Dicraeosaurids are a part of the Flagellicaudata, along with Diplodocidae. Dicraeosauridae includes genera such as ''Amargasaurus'', ''Suuwassea'', ''D ...

sauropod Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their bo ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

found in the

Upper Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...

strata of the

Morrison Formation The Morrison Formation is a distinctive sequence of Late Jurassic, Upper Jurassic sedimentary rock found in the western United States which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandsto ...

, located in southern Carbon County,

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbi ...

, United States. The fossil remains were recovered in a series of expeditions during a period spanning the years 1999 and 2000 and were described by J.D. Harris and

Peter Dodson Peter Dodson (born August 20, 1946) is an American paleontologist who has published many papers and written and collaborated on books about dinosaurs. An authority on Ceratopsians, he has also authored several papers and textbooks on hadrosaurs a ...

in 2004. They consist of a disarticulated but associated partial skeleton, including partial vertebral series and limb bones.

Etymology

Since the fossil was found in an ancestral territory of the Native American

Crow A crow is a bird of the genus ''Corvus'', or more broadly a synonym for all of ''Corvus''. Crows are generally black in colour. The word "crow" is used as part of the common name of many species. The related term "raven" is not pinned scientifical ...

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 Thunder is the sound caused by lightning. Depending upon the distance from and nature of the lightning, it can range from a long, low rumble to a sudden, loud crack. The sudden increase in temperature and hence pressure caused by the lightning pr ...

” and ''wassa'', “ancient”, are a nod to the “thunder lizard” moniker often applied to sauropods. The specific descriptor honours the deceased sponsor of the expeditions that recovered the fossil, Emilie deHellebranth (1914–2001).

Description

''Suuwassea'' is a dicraeosaurid, estimated to have reached in length and in body mass, characterized by skull and axial skeleton features it shares with

Diplodocidae Diplodocids, or members of the family Diplodocidae ("double beams"), are a group of sauropod dinosaurs. The family includes some of the longest creatures ever to walk the Earth, including ''Diplodocus'' and '' Supersaurus'', some of which may hav ...

and

Dicraeosauridae Dicraeosauridae is a family of diplodocoid sauropods who are the sister group to Diplodocidae. Dicraeosaurids are a part of the Flagellicaudata, along with Diplodocidae. Dicraeosauridae includes genera such as ''Amargasaurus'', ''Suuwassea'', ''D ...

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 the latter than with clade Dicraeosauridae.

Classification

In the original description, ''Suuwassea'' was placed at Flagellicaudata ''incertae sedis'' due to the mosaic of primitive and derived characters found in both dicraeosaurids and diplodocids. Later phylogenetic analysis placed it as a member of the diplodocid subfamily

Apatosaurinae Apatosaurinae is a subfamily of diplodocid sauropods that existed between 157 and 150 million years ago in North America. The group includes two genera for certain, ''Apatosaurus'' and ''Brontosaurus'', and at least five species. ''Atlantosaurus ...

, but subsequent studies recovered it as a North American member of Dicraeosauridae. A cladogram showing ''Suuwassea'' among other Dicraeosauridae, according to Tschopp et al., 2015:

References

{{Portal bar, Dinosaurs, United States Dicraeosaurids Late Jurassic dinosaurs of North America Dinosaurs of the Morrison Formation Fossil taxa described in 2004 Taxa named by Peter Dodson Paleontology in Montana