''Scutellosaurus'' ( ) is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of basal thyreophoran dinosaur that lived approximately 196

million years ago Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds. Usage Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...

during the early part of the

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...

Period in what is now Arizona, USA. It is classified in

Thyreophora Thyreophora ("shield bearers", often known simply as "armored dinosaurs") is a group of armored ornithischian dinosaurs that lived from the Early Jurassic until the end of the Cretaceous. Thyreophorans are characterized by the presence of bod ...

, the armoured dinosaurs; its closest relatives may have been '' Emausaurus'' and '' Scelidosaurus'', another armored dinosaur which was mainly a quadrupedal dinosaur, unlike

bipedal Bipedalism is a form of terrestrial locomotion where an animal moves by means of its two rear (or lower) limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' ...

''Scutellosaurus''. It is one of the earliest representatives of the armored dinosaurs and the basalmost form discovered to date. ''Scutellosaurus'' was a small, lightly-built, ground-dwelling

herbivore A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat ...

, that could grow up to an estimated long.

Discovery

The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

specimen of ''Scutellosaurus lawleri'' (MNA.V.175) was recovered at the West Moenkopi Plateau locality in the Silty Facies Member of the

Kayenta Formation The Kayenta Formation is a geological formation in the Glen Canyon Group that is spread across the Colorado Plateau area of the United States, including northern Arizona, northwest Colorado, Nevada, and Utah. Originally suggested as being Sinemur ...

, in Coconino County,

Arizona Arizona is a U.S. state, state in the Southwestern United States, Southwestern region of the United States, sharing the Four Corners region of the western United States with Colorado, New Mexico, and Utah. It also borders Nevada to the nort ...

on the land of the

Navajo Nation The Navajo Nation (), also known as Navajoland, is an Indian reservation of Navajo people in the United States. It occupies portions of northeastern Arizona, northwestern New Mexico, and southeastern Utah. The seat of government is located in ...

. The specimen was discovered and collected by David Lawler in red claystone sediments that were deposited during the

Sinemurian In the geologic timescale, the Sinemurian is an age (geology), age and stage (stratigraphy), stage in the Early Jurassic, Early or Lower Jurassic epoch (geology), Epoch or series (stratigraphy), Series. It spans the time between 199.5 ±0.3 annu ...

stage of the

period, approximately 196 million years ago. The genus name ''Scutellosaurus'' means "little-shielded lizard", and is derived from the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

word "scutellum" meaning "little shield", and the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

word "sauros" (σαύρα) meaning "lizard". The

type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * ...

and only valid

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

known today is ''Scutellosaurus lawleri''. The specific name honors David Lawler who collected the fossil. The holotype specimen was described by Edwin Colbert (1981) based on the following: partially preserved premaxillae with teeth, a right maxilla with seven teeth, a left maxilla with five teeth, dentaries that are missing their posterior portions, a left dentary with 18 teeth, a right dentary with 10 teeth, other skull fragments, 21 presacral vertebral centra, several complete and partial neural arches and spines, five sacral vertebrae, 58 caudal vertebrae with neural arches and several chevrons, several incomplete ribs, both scapulae, both coracoids, partially preserved ilia, fragments of the pubic bones and of the ischia, both humeri, the distal end of the right radius, the proximal and distal ends of the left radius and ulna, fragments of the manus, both femora, the right tibia, the proximal end of the right fibula, the right astragalus, the left tibia, the left fibula, various bones of the pedes, including a possible distal tarsal bone, and over 300 osteoderms.''The Illustrated Dinosaur Encyclopedia'', D. Dixon, 1998 (

Description

''Scutellosaurus'' was lightly built, and was probably capable of walking on its hind legs. It had an unusually long tail, possibly to provide a counterbalance against the weight of the armored body. It was a relatively small dinosaur, measuring in length and in body mass. The fossil evidence includes several partial skeletons recovered from

by the

Museum of Northern Arizona The Museum of Northern Arizona is a museum in Flagstaff, Arizona, United States, established as a repository for Indigenous material and natural history specimens from the Colorado Plateau. The museum was founded in 1928 by zoologist Dr. Harol ...

and the

University of California Museum of Paleontology The University of California Museum of Paleontology (UCMP) is a paleontology museum located on the campus of the University of California, Berkeley. The museum is within the Valley Life Sciences Building (VLSB), designed by George W. Kelham ...

, although the skull is poorly known from these specimens. There were several hundred

osteoderm Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct amph ...

s running along its neck to its back and as far down as its tail. These formed parallel rows, with as many as five rows on each side. It also had double rows of

s, or external plates, running neck to tail. Some of these shields were flat, while others were pitted.

References

{{Taxonbar, from=Q131646 Thyreophora Dinosaur genera Sinemurian dinosaurs Kayenta Formation Taxa named by Edwin H. Colbert Fossil taxa described in 1981 Dinosaurs of the United States