Seitaad is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of sauropodomorph dinosaur

Dinosaur

Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

 which lived during the lower Jurassic period in what is now southern Utah

Utah

Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...

, USA.

Seitaad is known from an articulated partial postcrania

Postcrania

Postcrania[p] in zoology and vertebrate paleontology refers to all or part of the skeleton apart from the skull. Frequently, fossil remains, e.g...

l holotype

Holotype

A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...

 skeleton

Skeleton

The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...

 referred to as UMNH

Utah Museum of Natural History

The Natural History Museum of Utah is a museum located at the Rio Tinto Center on the campus of the University of Utah in Salt Lake City, Utah, United States. The museum shows exhibits of natural history subjects, specifically about Utah's natural history...

 VP 18040. The skeleton is missing its head, neck and tail. It was collected from the Early Jurassic

Early Jurassic

The Early Jurassic epoch is the earliest of three epochs of the Jurassic period...

 Navajo Sandstone

Navajo Sandstone

Navajo Sandstone is a geologic formation in the Glen Canyon Group that is spread across the U.S. states of northern Arizona, northwest Colorado, and Utah; as part of the Colorado Plateau province of the United States...

, the uppermost unit of the Glen Canyon Group

Glen Canyon Group

The Glen Canyon Group is a geologic group of formations that is spread across the U.S. states of Nevada, Utah, northern Arizona, north west New Mexico and western Colorado. It is sometimes called the Glen Canyon Sandstone in Colorado and Utah. There are four formations within the group...

, dating to the Pliensbachian

Pliensbachian

The Pliensbachian is an age of the geologic timescale or stage in the stratigraphic column. It is part of the Early or Lower Jurassic epoch or series and spans the time between 189.6 ± 1.5 Ma and 183 ± 1.5 Ma . The Pliensbachian is preceded by the Sinemurian and followed by the Toarcian.The...

 stage, near Comb Ridge

Comb Ridge

Comb Ridge is a linear north to south-trending monocline nearly 120 miles long in southeast Utah and Arizona. Composed of Jurassic-age Navajo Sandstone, it displays massive eolian cross-bedding....

, San Juan County

San Juan County

San Juan County is the name of four counties in the United States:* San Juan County, Colorado* San Juan County, New Mexico* San Juan County, Utah* San Juan County, Washington...

. A phylogenetic study of Seitaad found it to be a plateosaur sauropodomorph, placing it in Massospondylidae

Massospondylidae

Massospondylidae is a family of massopod sauropodomorphs. Massospondylids are early sauropodomorph dinosaurs which existed in Asia, Africa and South America during the Late Triassic to the Early Jurassic periods...

 or alternatively (a less probable position) in Plateosauridae

Plateosauridae

Plateosauridae is a family of plateosaurian sauropodomorphs. Plateosaurids were early sauropodomorph dinosaurs which existed in Asia, Europe and South America during the Late Triassic period. Although several dinosaurs have been classified as plateosaurids over the years, a 2007 study by Adam M....

, but its placement within the Plateosauria

Plateosauria

Plateosauria is a clade of sauropodomorph dinosaurs which lived during the Late Triassic to the Late Cretaceous. The name Plateosauria was first coined by Gustav Tornier in 1913. The name afterwards fell out of use until the 1980s, when a new generation of paleontologists began using the name...

 is not well understood. In a cladistic analysis, presented by Apaldetti and colleagues in November 2011, Seitaad was found to be within Massopoda

Massopoda

The Massopoda is a clade of sauropodomorph dinosaurs which lived during the Late Triassic to the Late Cretaceous periods. Massopoda, which was first named by paleontologist Adam M...

, just outside Anchisauria

Anchisauria

The Anchisauria were a clade of sauropodomorph dinosaurs which lived during the Late Triassic and Early Jurassic. The name Anchisauria was first used by Galton and Upchurch in the second edition of The Dinosauria...

.

Seitaad was first described by Joseph J. W. Sertich and Mark A. Loewen in 2010

2010 in paleontology

-Anomalocaridids:-Newly named crustaceans:-Newly named insects:* A new family, Cascopleciidae, is published by Poinar Jr.* A new family of ceraphronoid Hymenopters, Radiophronidae, is published by Ortega-Blanco, Rasnitsyn, and Delclòs....

 and the type species

Type species

In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

 is Seitaad ruessi. The generic name is derived from Séít‘áád (Navajo language

Navajo language

Navajo or Navaho is an Athabaskan language spoken in the southwestern United States. It is geographically and linguistically one of the Southern Athabaskan languages .Navajo has more speakers than any other Native American language north of the...

), a mythological sand monster from the Diné folklore who buried its victims in dunes. Seitaad appears to have been entombed by the collapse of a sand dune. The specific name honours Everett Ruess, a young artist, poet and naturalist, who mysteriously disappeared in 1934 while exploring southern Utah. Seitaad is the second basal sauropodomorph dinosaur to have been identified in North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

.