{{italictitle}}
{{italictitle}}{{Taxobox
| name =
Scelidosaurus
| fossil_range = {{Fossil range|208|194}}
Early JurassicThe Early Jurassic epoch The Early Jurassic epoch The Early Jurassic epoch (in chronostratigraphy corresponding to the Lower Jurassic series is the earliest of three epochs of the Jurassic period...
| image = Scelidosaurus skeleton.png
| image_width = 250px
| image_caption = A nearly complete skeleton of
Scelidosaurus, showing fossils of the bony scutes, from the
Charmouth Heritage Coast CentreCharmouth Heritage Coast Centre is based in the upstairs floor of a long-disused cement factory on the foreshore of Charmouth in Dorset, England....
| regnum =
AnimalAnimals are a major group of mostly multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously...
ia
| phylum =
ChordataChordates are animals which are either vertebrates or one of several closely related invertebrates. They are united by having, for at least some period of their life cycle, a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail...
| classis =
SauropsidaReptiles, or members of the class Reptilia, are air-breathing, generally "cold-blooded" amniotes that generally have skin covered in scales or scutes. They are tetrapods and lay amniote eggs, whose embryos are surrounded by the amnion membrane...
| superordo =
Dinosaur{{Otheruses}}{{pp-semi-protected|small=yes}}{{Otheruses}}{{pp-semi-protected|small=yes}}{{Taxobox|name = Dinosaurs|fossil_range = {{Fossil range|230|65|earliest=230|latest=0|PS=
Descendant taxon Aves survives to present.}}|image = field_dinos_2.jpg...
ia
| ordo =
OrnithischiaOrnithischia or Predentata is an extinct order of beaked, herbivorous dinosaurs. The name ornithischia is derived from the Greek ornitheos meaning 'of a bird' and ischion meaning 'hip joint'...
| subordo =
ThyreophoraThe Thyreophora were a subgroup of the ornithischian dinosaurs...
| infraordo =
AnkylosauriaAnkylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms. Ankylosaurs were bulky quadrupeds, with short, powerful limbs. They are first known to have appeared in the early Jurassic Period of...
| familia =
Scelidosauridae
| familia_authority =
CopeEdward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope quickly distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of...
, 1869
| genus =
Scelidosaurus
| genus_authority=
OwenSir Richard Owen KCB was an English biologist, comparative anatomist and palaeontologist.Owen is probably best remembered today for coining the word Dinosauria and for his outspoken opposition to Charles Darwin's theory of evolution by natural selection...
, 1859
|subdivision_ranks=
SpeciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
|subdivision=
- S. harrisonii Owen, 1861 (type
In taxonomy, a type species is a technical phrase, involved in the application of formal names...
)
}}
Scelidosaurus ({{pron-en|ˌsɛlɨdɵˈsɔrəs}}, meaning "limb lizard", from
GreekAncient Greek is the historical stage in the development of the Greek language spanning across the Archaic , Classical , and Hellenistic periods of ancient Greece and the ancient world. It is predated in the 2nd millennium BC by Mycenaean Greek...
skelos/σκελος meaning 'leg' and
saurus/σαυρος meaning 'lizard') is a
genusIn biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...
of quadrupedal, lightly plated,
herbivorousA herbivore is an animal that is adapted to eat plants and not meat.Herbivory is a form of predation in which an organism consumes principally autotrophs such as plants, algae and photosynthesizing bacteria....
dinosaur{{Otheruses}}{{pp-semi-protected|small=yes}}{{Otheruses}}{{pp-semi-protected|small=yes}}{{Taxobox|name = Dinosaurs|fossil_range = {{Fossil range|230|65|earliest=230|latest=0|PS=
Descendant taxon Aves survives to present.}}|image = field_dinos_2.jpg...
about {{convert|4|m|ft}} long. It lived during the Early
JurassicThe Jurassic is a geologic period and system that extends from about Ma to Ma, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the "Age of Reptiles". The start of the period is marked by...
Period, during the
HettangianThe Hettangian is the earliest age or lowest stage of the Jurassic period of the geologic timescale. It spans the time between 199.6 ± 0.6 Ma and 196.5 ± 1 Ma . The Hettangian follows the Rhaetian and is followed by the Sinemurian.In Europe stratigraphy the Hettangian is a part of the time span in...
to
SinemurianIn the geologic timescale, the Sinemurian is an age or stage in the Early or Lower Jurassic epoch or series. It spans the time between 196.5 ± 2 Ma and 189.6 ± 1.5 Ma...
stagesIn chronostratigraphy, a stage is a succession of rock strata laid down in an single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries.Rock...
around 208 to 194
million years agoIn astronomy, geology, and paleontology, mya or "m.y.a." is an abbreviation for "million years ago". Like the related unit bya, mya is traditionally written in lower case...
. Its fossils have been found in both
EnglandEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west and the North Sea to the east, with the English Channel to the south separating it from continental...
and in
ArizonaThe State of Arizona is a state located in the southwestern region of the United States. The capital and largest city is Phoenix. The second largest city is Tucson, followed in size by the four Phoenix metropolitan area cities of Mesa, Glendale, Chandler, and Scottsdale.Arizona was the 48th and...
, in the United States.
Scelidosaurus has been called the earliest complete dinosaur. This genus and related genera have been found on three continents.
Comparative anatomist
Richard OwenSir Richard Owen KCB was an English biologist, comparative anatomist and palaeontologist.Owen is probably best remembered today for coining the word Dinosauria and for his outspoken opposition to Charles Darwin's theory of evolution by natural selection...
described
Scelidosaurus in 1859. Only one
speciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
,
S. harrisonii, is considered valid today, although other species have been proposed over the years. One of the most primitive of the
thyreophoraThe Thyreophora were a subgroup of the ornithischian dinosaurs...
ns, the exact placement of
Scelidosaurus within the suborder has been the subject of debate for nearly 150 years. This is not helped by the paucity of knowledge about its closest relatives.
Description
A full-grown
Scelidosaurus was rather small, compared to most other dinosaurs. Some scientists have estimated a length of 4 metres (13 ft)
Scelidosaurus was
quadrupedQuadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...
al, with the hindlimbs considerably longer than the forelimbs. It may have reared up on its hind legs to browse on foliage from trees, but its forefeet were as large as its hind feet, indicating a mostly quadrupedal posture.
Scelidosaurus had four toes, with the innermost digit being the smallest.
Skull
Unlike later ankylosaurs, the
skullThe skull is a bony structure found in the head of many animals. The skull supports the structures of the face and protects the head against injury....
was low and triangular in shape, longer than it was wide, similar to that of primitive ornithischians. The head of
Scelidosaurus was small, and it had a neck that was longer than that of most armored dinosaurs.
Like other thyreophorans,
Scelidosaurus was
herbivorousA herbivore is an animal that is adapted to eat plants and not meat.Herbivory is a form of predation in which an organism consumes principally autotrophs such as plants, algae and photosynthesizing bacteria....
, with very small, leaf-shaped cheek teeth suitable for cropping vegetation. It is believed
Scelidosaurus fed with a puncture-crush system of tooth-on-tooth action, with simple up-and-down jaw movement. Unlike later ankylosaurs,
Scelidosaurus still had the five pairs of fenestrae (skull openings) seen in primitive ornithischians, and its teeth were more leaf-shaped than later armored dinosaurs.
Armor
The most obvious feature of
Scelidosaurus is its armor, consisting of bony
scuteA scute or scutum is a bony external plate or scale, as on the shell of a turtle, the skin of crocodilians, or the feet of some birds.-Properties:Scutes are similar to scales and serve the same function...
s embedded in the skin. These osteoderms were arranged in parallel rows down the animal's body. Osteoderms are also found in the skin of
crocodileA crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all members of the order Crocodilia: i.e...
s,
armadilloArmadillos are small placental mammals, known for having a leathery armor shell. The Dasypodidae are the only surviving family in the order Cingulata, part of the superorder Xenarthra along with the anteaters and sloths...
s and some
lizardLizards are a very large and widespread group of squamate reptiles, with nearly 5,000 species, ranging across all continents except Antarctica as well as most oceanic island chains...
s. These osteoderms ranged in both size and shape; most were small, flat plates, but thicker scutes also occurred. The scutes were aligned in regular horizontal rows down the animal's neck, back, and hips, with smaller scutes arranged on the limbs and tail. The lateral scutes were conical, rather than the blade-like osteoderms of
Scutellosaurus, and have been used to identify the genus. It also had a pair of distinctive three-pointed scutes behind the head. Compared to later ankylosaurs,
Scelidosaurus was lightly armored.
Fossilized skin impressions have also been found. Between the bony scutes,
Scelidosaurus had rounded scales similar to those of a
Gila monsterThe Gila monster , Heloderma suspectum, is a species of venomous lizard native to the southwestern United States and northern Mexico...
. Between the large scutes, very small (5-10 millimetres [0.2-0.4 in]) flat "granules" of bone were distributed within the skin. In later ankylosaurs, these small scutes may have developed into larger scutes, fusing into the multi-osteodermal plate armor seen in genera such as
Ankylosaurus.
Diet
Scelidosaurus and its Jurassic relatives were herbivorous. However, while other ornithischians possessed teeth capable of grinding plant material,
Scelidosaurus had smaller, less complex teeth and a jaw capable of only simple up-and-down jaw movements. In this aspect, they resembled the stegosaurids, which also bore primitive teeth and simple jaws. Also like stegosaurs, they may have swallowed
gastrolithA gastrolith, also called a stomach stone or gizzard stones, is a rock held inside a gastrointestinal tract. Gastroliths are retained in the muscular gizzard and used to grind food in animals lacking suitable grinding teeth. The grain size depends upon the size of the animal and the gastrolith's...
s to aid processing of food (because of the lack of chewing ability), in the same manner used by modern birds and crocodiles. Their diet would have consisted of leaved plants or fruits, as grasses did not evolve until late into the Cretaceous Period, after
Scelidosaurus had become extinct.
Classification
Scelidosaurus was an ornithischian and has been classified at different times as an ankylosaur or stegosaur. This debate is still ongoing; at this time, it is considered to be either more closely related to ankylosaurids than to stegosaurids and, by extension, a true ankylosaur, or basal to the ankylosaur-stegosaur split. The stegosaur classification has fallen out of favor, but is seen in older dinosaur books. Despite its ankylosaur classification,
Scelidosaurus shared similarities with
StegosaurusStegosaurus is a genus of stegosaurid armored dinosaur from the Late Jurassic period in what is now western North America. In 2006, a specimen of Stegosaurus was announced from Portugal, showing that they were present in Europe as well...
, including a heavy body highest at the hips and bony plates down its back.
Scelidosaurus gives its name to the
Scelidosauridae, a group of primitive ornithischians close to the ancestry of ankylosaurs and stegosaurs. Aside from
Scelidosaurus, other members of the
cladeA clade is a term used in modern alpha taxonomy, the scientific classification of living and fossil organisms, to describe a monophyletic group, defined as a group consisting of a single common ancestor and all its descendants.[The term "monophyletic group" is used in this article...]
include
BienosaurusBienosaurus was a dinosaur from the Early Jurassic. The genus was an armored dinosaur from the Lower Lufeng Formation in Yunnan Province in China.-Discovery and species:...
and possibly
ScutellosaurusScutellosaurus is a genus of herbivorous dinosaur that lived in North America around 200 to 196 million years ago, in the Early Jurassic times....
. Originally proposed by
Edward Drinker CopeEdward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope quickly distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of...
in 1869, the family was resurrected by Chinese paleontologist
Dong ZhimingDong Zhiming , from the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, is one of China's leading paleontologists. He began working at the IVPP in 1962, learning from Yang Zhongjian who was director at the time...
in 2001 after study of
Bienosaurus, which shares close affinities with
Scelidosaurus. The scelidosaurids have been found in Early Jurassic formations, and may have persisted into the Late Jurassic. Their fossils have been found in
ChinaChina is a cultural region, an ancient civilization, and, depending on perspective, a national or multinational entity extending over a large area in East Asia....
, England, and Arizona. Some paleontologists consider the Scelidosauridae
paraphyleticIn phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all the descendants of that ancestor.- Relation to monophyletic groups :...
, but
BentonMichael J. Benton is a Fellow of the Royal Society of Edinburgh and professor of vertebrate palaeontology in the Department of Earth Sciences at the University of Bristol...
(2004) lists the group as
monophyleticIn common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it consists of an ancestor and all its descendants. The term is synonymous with the uncommon term holophyly...
.
Fossil records of thyreophorans more basal than
Scelidosaurus are sparse. The more primitive
Scutellosaurus, also found in Arizona, was an earlier genus which was facultatively bipedal. A trackway of a possible early armoured dinosaur, from around 195 million years ago, has been found in France. Ancestors of these primitive thyreophorans evolved from early ornithischians similar to
LesothosaurusLesothosaurus is an herbivorous ornithischian dinosaur. It was named by paleontologist Peter Galton in 1978, the name meaning "lizard from Lesotho". The genus is monotypic, having only one valid species, Lesothosaurus diagnosticus, within the genus....
during the Late Jurassic.
Species
S. harrisonii, described by Owen, is currently the only recognized
speciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
, based on several nearly complete skeletons. A potential second species from the
SinemurianIn the geologic timescale, the Sinemurian is an age or stage in the Early or Lower Jurassic epoch or series. It spans the time between 196.5 ± 2 Ma and 189.6 ± 1.5 Ma...
-age Lower Lufeng Formation,
S. oehleri, was described by D.J. Simmons in 1965 under its own genus,
TatisaurusTatisaurus is a genus of dinosaur from the Early Jurassic from the Lower Lufeng Formation in Yunnan Province in China. Little is known as the remains are fragmentary.-Discovery and species:...
. In 1996
Spencer G. LucasSpencer G. Lucas is an American paleontologist and stratigrapher, and curator of paleontology at the New Mexico Museum of Natural History and Science. His main areas of study are late Paleozoic, Mesozoic and early Cenozoic vertebrate fossils, stratigraphy, and continental deposits, particularly in...
moved it to
Scelidosaurus. Although the fossils are fragmentary, this reassessment has not been accepted, and
S. oehleri is today once again recognized as
Tatisaurus.
History of discovery
While James Harrison of
CharmouthCharmouth is a village at the mouth of the River Char in West Dorset, England, with a population of 1,687 according to the 2001 census.The cliffs above the beach are noted for the number of fossils from the Jurassic era. Charmouth Heritage Coast Centre acts as a visitor centre for the Jurassic...
, England was quarrying the cliffs of
Black VenBlack Ven is a cliff in Dorset, England. It is part of the Jurassic Coast World Heritage site. The cliff is famous for its mudslides, in fact, it has the largest mudslides in Europe. The area is popular with tourists because a number of fossils are found in the area.- History :The Black Ven has...
(between Charmouth and
Lyme RegisLyme Regis is a coastal town in West Dorset, England, situated 25 miles west of Dorchester and east of Exeter. The town lies in Lyme Bay, on the English Channel coast at the Dorset-Devon border. It is nicknamed "The Pearl of Dorset." In the 13th century it developed into one of the major British...
), possibly for raw material for the manufacture of
cementIn the most general sense of the word, a cement is a binder, a substance which sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term "opus caementicium" to describe masonry which resembled concrete and was made from crushed...
, in 1858, he found a few fragmentary
fossilFossils are the preserved remains or traces of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous rock formations and sedimentary layers is known as the fossil record...
s of limb bones. He sent them to Professor
Richard OwenSir Richard Owen KCB was an English biologist, comparative anatomist and palaeontologist.Owen is probably best remembered today for coining the word Dinosauria and for his outspoken opposition to Charles Darwin's theory of evolution by natural selection...
of the
Natural History MuseumThe Natural History Museum is one of three large museums on Exhibition Road, South Kensington, London . Its main frontage is on Cromwell Road...
(originally the
British MuseumThe British Museum is a museum of human history and culture situated in London. Its collections, which number more than seven million objects, are amongst the largest and most comprehensive in the world and originate from all continents, illustrating and documenting the story of human culture from...
(Natural History), London). These, with later finds from the same spot, revealed a nearly complete skeleton.
Scelidosaurus was named by Sir Richard Owen in 1859; however, a complete description did not appear until 1863. Unfortunately, mixed in with the
Scelidosaurus fossils were the partial remains of a theropod dinosaur; this was not discovered until 1968. In 1888,
Richard LydekkerRichard Lydekker was an English naturalist, geologist and writer of numerous books on natural history.Lydekker was born in London, and educated at Trinity College, Cambridge, where he took a first-class in the Natural Science tripos...
selected the knee joint as the lectotype of
Scelidosaurus.
For many years, the enigmatic fossils of
Scelidosaurus caused some debate over the classification of the genus. Von Zittel (1902), Swinton (1934), and Appleby
et al. (1967) identified the genus as a stegosaur. In a 1968 paper, Romer argued it was an ankylosaur. In 1977, Richard Thulborn of the
University of QueenslandThe University of Queensland, also known as UQ, is a public university located in Brisbane, Australia. Founded in 1909, it is the oldest university in Queensland and the fifth in the nation. The main campus is located in St Lucia, southwest of the Brisbane CBD...
attempted to reclassify
Scelidosaurus as an ornithopod similar to
TenontosaurusTenontosaurus is a genus of medium- to large-sized ornithopod dinosaur. It was formerly thought to be a 'hypsilophodont', but since Hypsilophodontia is no longer considered a clade, it is now considered to be a very primitive iguanodont.-Description:...
or
IguanodonIguanodon is a genus of ornithopod dinosaur that lived roughly halfway between the first of the swift bipedal hypsilophodontids and the ornithopods' culmination in the duck-billed dinosaurs...
. Thulborn argued
Scelidosaurus was a lightly-built bipedal dinosaur adapted for running. Thulborn's 1977 theories on the genus have since been rejected.
In 1968, B. H. Newman applied to have Lydekker's selection of the knee joint as the lectotype officially rescinded by the
International Commission on Zoological NomenclatureInternational Commission on Zoological Nomenclature is an organization dedicated to "achieving stability and sense in the scientific naming of animals". Founded in 1895, it currently comprises 28 members from 20 countries, mainly practicing zoological taxonomists...
, as the joint was from a megalosaur. Wells
et al. informally reassigned these bones, consisting of a
femurThe femur, or thigh bone, is the most proximal bone of the leg in vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs...
and partial
tibiaThe tibia, shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates and connects the knee with the ankle bones.The tibia is named for the greek aulos flute, also known as a tibia.-In humans:...
, to "
Merosaurus"Merosaurus" is the informal name given to an as yet undescribed genus of dinosaur from the Early Jurassic ....
" in 1995.
In 1989, scutes identified as belonging to
Scelidosaurus, which were found in the
Kayenta FormationThe Kayenta Formation is a geologic layer in the Glen Canyon Group that is spread across the Colorado Plateau province of the United States, including northern Arizona, northwest Colorado, Nevada, and Utah. This rock formation is particularly prominent in southeastern Utah, where it is seen in the...
(Glen Canyon Group) of northern Arizona, helped to determine the age of the strata was around 200 million years ago. These scutes also established a geographic tie-in between Arizona's Glen Canyon and Europe, where fossils of
Scelidosaurus had previously been discovered. Some scientists have disputed the assignment to
Scelidosaurus, though.
In 2000, Martill
et al. announced the preservation of soft tissue in a specimen of
Scelidosaurus. These fossils consist of eight caudal vertebrae in a cut slab of carbonate
mudstone, which was judged to date from the late
HettangianThe Hettangian is the earliest age or lowest stage of the Jurassic period of the geologic timescale. It spans the time between 199.6 ± 0.6 Ma and 196.5 ± 1 Ma . The Hettangian follows the Rhaetian and is followed by the Sinemurian.In Europe stratigraphy the Hettangian is a part of the time span in...
to
SinemurianIn the geologic timescale, the Sinemurian is an age or stage in the Early or Lower Jurassic epoch or series. It spans the time between 196.5 ± 2 Ma and 189.6 ± 1.5 Ma...
stagesIn chronostratigraphy, a stage is a succession of rock strata laid down in an single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries.Rock...
. Parts of the fossil were preserved in such a way that an envelope of preserved soft tissue is visible around the vertebrae, and show the presence of an epidermal layer over the scutes. The authors concluded that the osteoderms of all basal armored dinosaurs were covered in a tough, probably keratinous layer of skin.
In popular culture
Although
Scelidosaurus is nowhere near as well-known as its sister taxa
Ankylosaurus or
Stegosaurus, the genus has appeared infrequently in popular media. One instance is in Nintendo's
Jurassic Park III: Park BuilderJurassic Park III: Park Builder is a construction and management simulation game for the Game Boy Advance that was developed by Konami and released in 2001.-Summary:...
video game, where the player controls a menagerie of dinosaurs, including
Scelidosaurus. The dinosaur is also one of the main exhibits at the
Charmouth Heritage Coast CentreCharmouth Heritage Coast Centre is based in the upstairs floor of a long-disused cement factory on the foreshore of Charmouth in Dorset, England....
in
CharmouthCharmouth is a village at the mouth of the River Char in West Dorset, England, with a population of 1,687 according to the 2001 census.The cliffs above the beach are noted for the number of fossils from the Jurassic era. Charmouth Heritage Coast Centre acts as a visitor centre for the Jurassic...
,
EnglandEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west and the North Sea to the east, with the English Channel to the south separating it from continental...
. The center houses both a model and a cast of
Scelidosaurus, fossils of which were collected in the area. The children's show
Harry and His Bucket Full of DinosaursHarry and His Bucket Full of Dinosaurs is a series of children's books written and drawn by Ian Whybrow and Adrian Reynolds. The series is about a 5-year-old boy named Harry, who has a bucket full of dinosaurs. In the books the dinosaurs talk to Harry but seem to be toys to the other characters...
features a
Scelidosaurus named Sid as one of Harry's dinosaur friends.
External links
{{commons}}
{{Wikispecies|Scelidosaurus}}
{{portalpar|Dinosaurs}}