''Seitaad'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

of sauropodomorph

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 ...

which lived during the Early

Jurassic period The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...

in what is now southern

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to its ...

, United States. ''Seitaad'' is known from an

articulated An articulated vehicle is a vehicle which has a permanent or semi-permanent pivot joint in its construction, allowing it to turn more sharply. There are many kinds, from heavy equipment to buses, trams and trains. Steam locomotives were sometim ...

partial

postcrania Postcrania (postcranium, adjective: postcranial) in zoology and vertebrate paleontology is all or part of the skeleton apart from the skull. Frequently, fossil remains, e.g. of dinosaurs or other extinct tetrapods, consist of partial or isolated s ...

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...

skeleton A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...

referred to as UMNH VP 18040. The skeleton is missing its head, neck and tail. It was collected from the Lower Jurassic

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

, the uppermost unit of the Glen Canyon Group, dating to the

Pliensbachian The Pliensbachian is an age of the geologic timescale and stage in the stratigraphic column. It is part of the Early or Lower Jurassic Epoch or Series and spans the time between 190.8 ± 1.5 Ma and 182.7 ± 1.5 Ma (million years ago). The ...

stage, near

Comb Ridge Comb Ridge ( nv, ) is a linear north to south-trending monocline nearly 80 miles long in Southeastern Utah and Northeastern Arizona. Its northern end merges with the Abajo Mountains some eleven miles west of Blanding. It extends essentially du ...

, San Juan County. A phylogenetic study of ''Seitaad'' found it to be a plateosaur sauropodomorph, placing it in Massospondylidae or alternatively (a less probable position) in Plateosauridae, but its placement within the Plateosauria is not well understood. In a

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived ch ...

analysis, presented by Apaldetti and colleagues in November 2011, ''Seitaad'' was found to be within

Massopoda Massopoda is a clade of sauropodomorph dinosaurs which lived during the Late Triassic to Late Cretaceous epochs. It was named by paleontologist Adam M. Yates of the University of the Witwatersrand in 2007. Massopoda is a stem-based taxon, define ...

, just outside

Anchisauria Anchisauria is an extinct clade of sauropodomorph dinosaurs that lived from the Late Triassic to the Late Cretaceous. The name Anchisauria was first used Haekel and defined by Galton and Upchurch in the second edition of ''The Dinosauria''. It is ...

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

2010 File:2010 Events Collage New.png, From top left, clockwise: The 2010 Chile earthquake was one of the strongest recorded in history; The Eruption of Eyjafjallajökull in Iceland disrupts air travel in Europe; A scene from the opening ceremony of ...

and the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...

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

Navajo language Navajo or Navaho (; Navajo: or ) is a Southern Athabaskan languages, Southern Athabaskan language of the Na-Dene languages, Na-Dené family, through which it is related to languages spoken across the western areas of North America. Navajo is s ...

), 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 Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

honours

Everett Ruess Everett Ruess (March 28, 1914 – ''c.'' November 1934) was an American artist, poet, and writer. He carried out solo explorations of the High Sierra, the California coast, and the deserts of the American Southwest. In 1934, he disappeared while ...

, 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.

References

Fossil taxa described in 2010 Early Jurassic dinosaurs of North America Massopoda Paleontology in Utah {{Sauropodomorph-stub