132-521: Stegosauria is a group of herbivorous ornithischian dinosaurs that lived during the Jurassic and early Cretaceous periods . Stegosaurian fossils have been found mostly in the Northern Hemisphere ( North America , Europe and Asia ), Africa and possibly South America . Their geographical origins are unclear; the earliest unequivocal stegosaurian, Bashanosaurus primitivus ,
264-667: A eurypodan synapomorphy . Huayangosaurus lived during the Bathonian stage of the Middle Jurassic , about 166 million years ago. A few million years later, during the Callovian - Oxfordian , from China much larger species are known, with long, "graviportal" (adapted for moving only in a slow manner on land due to a high body weight) hindlimbs: Chungkingosaurus , Chialingosaurus , Tuojiangosaurus and Gigantspinosaurus . Most of these are considered members of
396-427: A stegosaurine . Subsequently, in 1964, Oskar Kuhn referred the nomen nudum "Omosaurus leedsi" Seeley vide Huene 1901 to Lexovisaurus as Lexovisaurus leedsi . In 1983, Peter Galton renamed Omosaurus vetustus Huene 1910 into Lexovisaurus vetustus . However, in 2008 Susannah Maidment and colleagues concluded that the holotype of Lexovisaurus , BMNH R1989, was undiagnostic, so they split off BMNH R3167 and
528-523: A decrease in abundance of leaf-chewing larvae in the fall when hardwood leaf palatability decreases due to increased tannin levels which results in a decline of arthropod species richness , and increased palatability of plant communities at higher elevations where grasshoppers abundances are lower. Climatic stressors such as ocean acidification can lead to responses in plant-herbivore interactions in relation to palatability as well. The myriad defenses displayed by plants means that their herbivores need
660-419: A deep mandible, compared to that of Huayangosaurus . Stegosaurids also lack premaxillary teeth. All stegosaurians are quadrupedal , with hoof-like toes on all four limbs. All stegosaurians after Huayangosaurus have forelimbs much shorter than their hindlimbs. Their hindlimbs are long and straight, designed to carry the weight of the animal while stepping. The condyles of the lower thighbone are short from
792-444: A dinosaur excavated at a small brick pit at the hamlet of Tanholt , close to Eye , Cambridgeshire . In September 1885 the remains were shown to paleontologist Henry Woodward whose notes form the first documentation on the subject. Later it was mistakenly assumed the find had been made at the industrial brick pits at Fletton , the usual source of Leeds' specimens. In 1887 the fossil was described by John Whitaker Hulke and named as
924-457: A fossil hunter working for Professor Othniel Charles Marsh , in Wyoming excavated a fossil that Marsh the same year named Stegosaurus . At first, Marsh still entertained some incorrect notions about its morphology. He assumed that the plates formed a flat skin cover — hence the name, meaning "roof saurian" — and that the animal was bipedal with the spikes sticking out sideways from the rear of
1056-415: A fusion into two blocks, an ulnar and a radial. The front feet of stegosaurians are commonly depicted in art and in museum displays with fingers splayed out and slanted downward. However, in this position, most bones in the hand would be disarticulated. In reality, the hand bones of stegosaurians were arranged into vertical columns, with the main fingers, orientated outwards, forming a tube-like structure. This
1188-623: A greater and more diverse set of resources. Coevolution and phylogenetic correlation between herbivores and plants are important aspects of the influence of herbivore and plant interactions on communities and ecosystem functioning, especially in regard to herbivorous insects. This is apparent in the adaptations plants develop to tolerate and/or defend from insect herbivory and the responses of herbivores to overcome these adaptations. The evolution of antagonistic and mutualistic plant-herbivore interactions are not mutually exclusive and may co-occur. Plant phylogeny has been found to facilitate
1320-528: A head-on aggressive stance. Stegosaurian tracks were first recognized in 1996 from a hindprint-only trackway discovered at the Cleveland-Lloyd quarry , which is located near Price, Utah. Two years later, a new ichnogenus called Stegopodus was erected for another set of stegosaurian tracks which were found near Arches National Park , also in Utah. Unlike the first, this trackway preserved traces of
1452-465: A herbivore in a dense forest would spend more time handling (eating) the vegetation because there was so much vegetation around than a herbivore in a sparse forest, who could easily browse through the forest vegetation. According to the Holling's disk equation, a herbivore in the sparse forest would be more efficient at eating than the herbivore in the dense forest. The marginal value theorem describes
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#17327913856571584-432: A horn-covered beak or rhamphotheca , which covered the front of the snout (two premaxillaries ) and lower jaw (a single predentary ) bones. Similar structures are seen in turtles and birds . Apart from Huayangosaurus , stegosaurians subsequently lost all premaxillary teeth within the upper beak. Huayangosaurus still had seven per side. The upper and lower jaws are equipped with rows of small teeth. Later species have
1716-490: A large antitrochanter (supracetabular process) in the ilium , a long prepubic process and long femur relative to the length of the humerus . Furthermore, stegosaurid sacral ribs are T-shaped in parasagittal cross-section and the dorsal vertebrae have an elongated neural arch. The first exact clade definition of Stegosauria was given by Peter Malcolm Galton in 1997: all thyreophoran Ornithischia more closely related to Stegosaurus than to Ankylosaurus . This definition
1848-406: A long time considered a nomen nudum , was described in 1994. Like the spikes and shields of ankylosaurs , the bony plates and spines of stegosaurians evolved from the low-keeled osteoderms characteristic of basal thyreophorans. One such described genus, Scelidosaurus , is proposed to be morphologically close to the last common ancestor of the clade uniting stegosaurians and ankylosaurians,
1980-554: A matter of great debate. The first stegosaurian finds in the early 19th century were fragmentary. Better fossil material, of the genus Dacentrurus , was discovered in 1874 in England. Soon after, in 1877, the first nearly-complete skeleton was discovered in the United States. Professor Othniel Charles Marsh that year classified such specimens in the new genus Stegosaurus , from which the group acquired its name, and which
2112-495: A mutual relationship with the plant species that they forage by digging and disturbing the sediment which removes competing plants and subsequently allows colonization of other plant species. When herbivores are affected by trophic cascades , plant communities can be indirectly affected. Often these effects are felt when predator populations decline and herbivore populations are no longer limited, which leads to intense herbivore foraging which can suppress plant communities. With
2244-557: A new patch of food when the patch they are currently feeding on requires more energy to obtain food than an average patch. Within this theory, two subsequent parameters emerge, the Giving Up Density (GUD) and the Giving Up Time (GUT). The Giving Up Density (GUD) quantifies the amount of food that remains in a patch when a forager moves to a new patch. The Giving Up Time (GUT) is used when an animal continuously assesses
2376-706: A new species of the stegosaurian Omosaurus : Omosaurus durobrivensis . The specific name referred to the old Roman town of Durobrivae . On 30 May 1892 the specimen was bought by the British Museum of Natural History . The holotype , NHMUK R1989 , was found in the Peterborough Member of the Oxford Clay Formation , more especially the Kosmoceras jason biozone dating from the middle Callovian . Hulke mistakenly assumed
2508-415: A pelvis width of 114 cm (45 in). Part of the material described by Hulke was a left femur, specimen BMNH R1991, with a length of 99 cm (39 in). The Fletton and Normandy material show a combination of narrow flat plates on the back and round pointed spines that ran along the tail. A large spine was found that by Hoffstetter was placed on the shoulder, by Galton on the hip and by Maidment on
2640-458: A plesiomorphic characters. However, the absence of lateral scutes as well as pre-maxillary teeth mentioned above are not specifically diagnostic of stegosaurids, since these features are also present in some other stegosaurians, whose phylogenetic relationships are unclear. The discovery of an impression of the skin covering the dorsal plates has implications for all possible functions of stegosaurian plates. Christiansen and Tschopp (2010) found that
2772-460: A provenance from the younger Kimmeridge Clay Formation . It consists of a sacrum of five vertebrae, and two ilia. Other bones were referred to the species, among them two plates thought to be part of the dermal armour. However, on 22 August 1888 Othniel Charles Marsh visited Leeds' collection at Eyebury and recognised these elements as belonging to a giant fish, in 1889 by Arthur Smith Woodward named Leedsichthys . The plates are in fact part of
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#17327913856572904-715: A result of their plant-based diet, herbivorous animals typically have mouth structures ( jaws or mouthparts ) well adapted to mechanically break down plant materials, and their digestive systems have special enzymes (e.g. amylase and cellulase ) to digest polysaccharides . Grazing herbivores such as horses and cattles have wide flat- crowned teeth that are better adapted for grinding grass , tree bark and other tougher lignin -containing materials, and many of them evolved rumination or cecotropic behaviors to better extract nutrients from plants. A large percentage of herbivores also have mutualistic gut flora made up of bacteria and protozoans that help to degrade
3036-566: A row of smaller osteoderms, culminating in a long shoulder spine in front, curving to the rear. Later forms show very variable configurations, combining plates of various shape and size on the neck and front torso with spikes more to the rear of the animal. They seem to have lost the tail club and the flank rows are apparently absent also, with the exception of the shoulder spine, still shown by Kentrosaurus and extremely developed, as its name indicates, in Gigantspinosaurus . As far as
3168-407: A single median row of plates running post-cranially along the longitudinal axis and Lull argued in favour of bilaterally paired arrangement throughout the series. Current scientific consensus lies in the arrangement proposed by Gilmore - two parasagittal rows of staggered alternates, after the discovery of an almost complete skeleton preserved in this manner in rock. Furthermore, no two plates share
3300-635: A single plant can have hundreds of different chemical defenses. Chemical defenses can be divided into two main groups, carbon-based defenses and nitrogen-based defenses. Plants have also changed features that enhance the probability of attracting natural enemies to herbivores. Some emit semiochemicals, odors that attract natural enemies, while others provide food and housing to maintain the natural enemies' presence, e.g. ants that reduce herbivory. A given plant species often has many types of defensive mechanisms, mechanical or chemical, constitutive or induced, which allow it to escape from herbivores. According to
3432-406: A sprawled crocodilian pose for defensive behavior. The sprawled pose would allow them to tolerate the large lateral forces used in swinging the spiked tail against predators as a clubbing device. There have been several findings of possible sexual dimorphism in stegosaurids. Saitta (2015) presents evidence of two morphs of Hesperosaurus dorsal plates, with one morph having a wide, oval plate with
3564-567: A surface area 45% larger than the narrow, tall morph. Considering that dorsal plates most likely functioned as display structures and that the wide oval shape allowed a broad continuous display, Saitta assigns the wider morph with larger surface area as male. Kevin Padian , a paleontologist at the University of California, Berkeley, remarked that Saitta had misidentified features in his specimen's bone tissue sections and said “there’s no evidence
3696-574: A terrestrial mammal to be called a grazer, at least 90% of the forage has to be grass, and for a browser at least 90% tree leaves and twigs. An intermediate feeding strategy is called "mixed-feeding". In their daily need to take up energy from forage, herbivores of different body mass may be selective in choosing their food. "Selective" means that herbivores may choose their forage source depending on, e.g., season or food availability, but also that they may choose high quality (and consequently highly nutritious) forage before lower quality. The latter especially
3828-461: A thick base and central portion, but are transversely thin elsewhere. The plates become remarkably large and thin in Stegosaurus . They are found in varying sizes along the dorsum, with the central region of the back usually having the largest and tallest plates. The arrangement of these parasagittal dorsal plates has been intensely debated in the past. Discoverer Othniel Charles Marsh suggested
3960-399: A tradeoff however, between foraging on many plant species to avoid toxins or specializing on one type of plant that can be detoxified. Herbivore modification is when various adaptations to body or digestive systems of the herbivore allow them to overcome plant defenses. This might include detoxifying secondary metabolites , sequestering toxins unaltered, or avoiding toxins, such as through
4092-438: A trophic cascade involved plant-herbivore interactions are coral reef ecosystems. Herbivorous fish and marine animals are important algae and seaweed grazers, and in the absence of plant-eating fish, corals are outcompeted and seaweeds deprive corals of sunlight. Agricultural crop damage by the same species totals approximately $ 100 million every year. Insect crop damages also contribute largely to annual crop losses in
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4224-579: A variety of physical and metabolic alterations in the way the host plant interacts with itself and other surrounding biotic factors. Fungi, bacteria, and protists that feed on living plants are usually termed plant pathogens (plant diseases), while fungi and microbes that feed on dead plants are described as saprotrophs . Flowering plants that obtain nutrition from other living plants are usually termed parasitic plants . There is, however, no single exclusive and definitive ecological classification of consumption patterns; each textbook has its own variations on
4356-527: A variety of skills to overcome these defenses and obtain food. These allow herbivores to increase their feeding and use of a host plant. Herbivores have three primary strategies for dealing with plant defenses: choice, herbivore modification, and plant modification. Feeding choice involves which plants a herbivore chooses to consume. It has been suggested that many herbivores feed on a variety of plants to balance their nutrient uptake and to avoid consuming too much of any one type of defensive chemical. This involves
4488-423: A vast increase of digging activities in that country. This resulted in a new wave of Chinese stegosaurian discoveries, starting with Chialingosaurus in 1957. Chinese finds of the 1970s and 1980s included Wuerhosaurus , Tuojiangosaurus , Chungkingosaurus , Huayangosaurus , Yingshanosaurus and Gigantspinosaurus . This increased the age range of good fossil stegosaurian material, as they represented
4620-456: A vertical bone plate covering the outer side of the lower jaw teeth. The structure of the upper jaw, with a low ridge above, and running parallel to, the tooth row, indicates the presence of a fleshy cheek. In stegosaurians, the typical archosaurian skull opening, the antorbital fenestra in front of the eye socket, is small, sometimes reduced to a narrow horizontal slit. In general, stegosaurids have proportionally long, low and narrow snouts with
4752-460: Is a model for predicting animal behavior while looking for food or other resources, such as shelter or water. This model assesses both individual movement, such as animal behavior while looking for food, and distribution within a habitat, such as dynamics at the population and community level. For example, the model would be used to look at the browsing behavior of a deer while looking for food, as well as that deer's specific location and movement within
4884-403: Is aided in reproduction. Plants can also be indirectly affected by herbivores through nutrient recycling , with plants benefiting from herbivores when nutrients are recycled very efficiently. Another form of plant-herbivore mutualism is physical changes to the environment and/or plant community structure by herbivores which serve as ecosystem engineers , such as wallowing by bison. Swans form
5016-431: Is derived from Latin herba 'small plant, herb' and vora , from vorare 'to eat, devour'. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants , algae and photosynthesizing bacteria . More generally, organisms that feed on autotrophs in general are known as primary consumers . Herbivory is usually limited to animals that eat plants. Insect herbivory can cause
5148-563: Is determined by the body mass of the herbivore, with small herbivores selecting for high-quality forage, and with increasing body mass animals are less selective. Several theories attempt to explain and quantify the relationship between animals and their food, such as Kleiber's law , Holling's disk equation and the marginal value theorem (see below). Kleiber's law describes the relationship between an animal's size and its feeding strategy, saying that larger animals need to eat less food per unit weight than smaller animals. Kleiber's law states that
5280-783: Is irrelevant and derived to explain trends that do not exist in nature. Holling's disk equation models the efficiency at which predators consume prey. The model predicts that as the number of prey increases, the amount of time predators spend handling prey also increases, and therefore the efficiency of the predator decreases. In 1959, S. Holling proposed an equation to model the rate of return for an optimal diet: Rate (R )=Energy gained in foraging (Ef)/(time searching (Ts) + time handling (Th)) R = E f / ( T s + T h ) {\displaystyle R=Ef/(Ts+Th)} Where s=cost of search per unit time f=rate of encounter with items, h=handling time, e=energy gained per encounter. In effect, this would indicate that
5412-435: Is known, all forms possessed some sort of thagomizer, though these are rarely preserved articulated allowing to establish the exact arrangement. A fossil of Chungkingosaurus sp. has been reported with three pairs of spikes pointing outwards and a fourth pair pointing to the rear. The most derived species, like Stegosaurus , Hesperosaurus and Wuerhosaurus , have very large and flat back plates. Stegosaurid plates have
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5544-416: Is not regarded as valid. The nomen nudum "Omosaurus leedsi" (mistakenly considered a nomen dubium by Maidment et al. 2008) has since been referred to Loricatosaurus . Lexovisaurus was a medium-sized stegosaur, reaching 6 metres (20 ft) in length and 2 metric tons (2.2 short tons) in body mass. Little information about the holotype is available apart from it having a general stegosaurian build and
5676-628: Is poorly supported by the data, stegosaurians are an exception in that their decline coincides with that of the Cycadophyta . Though Late Cretaceous stegosaurian fossils have been reported, these have mostly turned out to be misidentified. A well-known example is Dravidosaurus , known from Coniacian fossils found in India. Though originally thought to be stegosaurian, in 1991 these badly-eroded fossils were suggested to instead have been based on plesiosaurian pelvis and hindlimb material, and none of
5808-428: Is similar to the hands of sauropod dinosaurs , and is also supported by evidence from stegosaurian footprints and fossils found in a lifelike pose. The long hindlimbs elevated the tail base, such that the tail pointed out behind the animal almost horizontally from that high position. While walking, the tail would not have sloped downwards as this would have impeded the function of the tail base retractor muscles, to pull
5940-414: Is still by far the most famous stegosaurian. During the latter half of the twentieth century, many important Chinese finds were made, representing about half of the presently known diversity of stegosaurians. The first known discovery of a possible stegosaurian was probably made in the early nineteenth century in England. It consisted of a lower jaw fragment and was in 1848 named Regnosaurus . In 1845, in
6072-488: Is the ability of a plant to withstand damage without a reduction in fitness. This can occur by diverting herbivory to non-essential plant parts, resource allocation, compensatory growth, or by rapid regrowth and recovery from herbivory. Resistance refers to the ability of a plant to reduce the amount of damage it receives from herbivores. This can occur via avoidance in space or time, physical defenses, or chemical defenses. Defenses can either be constitutive, always present in
6204-508: Is widespread, with members across the Northern Hemisphere, Africa and possibly South America . Huayangosauridae (derived from Huayangosaurus , " Huayang reptile") is a family of stegosaurian dinosaurs from the Jurassic of China . The group is defined as all taxa closer to the namesake genus Huayangosaurus than Stegosaurus , and was originally named as the family Huayangosaurinae by Dong Zhiming and colleagues in
6336-541: The Eurypoda . Galton (2019) interpreted plates of an armored dinosaur from the Lower Jurassic ( Sinemurian - Pliensbachian ) Lower Kota Formation of India as fossils of a member of Ankylosauria ; the author argued that this finding indicates a probable early Early Jurassic origin for both Ankylosauria and its sister group Stegosauria. Footprints attributed to the ichnotaxon Deltapodus brodricki from
6468-591: The Hekou Group of China, and Yanbeilong of the Zuoyun Formation of China, all of which date to the Aptian - Albian . It has often been suggested that the decline in stegosaur diversity was part of a Jurassic-Cretaceous transition, where angiosperms become the dominant plants, causing a faunal turnover where new groups of herbivores evolved. Although in general the case for such a causal relation
6600-503: The Hettangian -aged deposits of France , indicating a possibly earlier origin. The perhaps most basal known stegosaurian, the four-metre-long Huayangosaurus , is still close to Scelidosaurus in build, with a higher and shorter skull, a short neck, a low torso, long slender forelimbs, short hindlimbs, large condyles on the thighbone, a narrow pelvis, long ischial and pubic shafts, and a relatively long tail. Its small tail club might be
6732-506: The Stegosauridae , became larger, and developed long hindlimbs that no longer allowed them to run. This increased the importance of active defence by the thagomizer , which could ward off even large predators because the tail was in a higher position, pointing horizontally to the rear from the broad pelvis. Stegosaurids had complex arrays of spikes and plates running along their backs, hips and tails. Stegosauria includes two families,
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#17327913856576864-491: The cellulose in plants, whose heavily cross-linking polymer structure makes it far more difficult to digest than the protein - and fat -rich animal tissues that carnivores eat. Herbivore is the anglicized form of a modern Latin coinage, herbivora , cited in Charles Lyell 's 1830 Principles of Geology . Richard Owen employed the anglicized term in an 1854 work on fossil teeth and skeletons. Herbivora
6996-435: The sacral vertebrae have given rise to the incorrect notion of a "second brain". Despite the downwards curvature of the rump, the neck base was not very low and the head was held a considerable distance off the ground. The neck was flexible and moderately long. Huayangosaurus still had the probably original number of nine cervical vertebrae; Miragaia has an elongated neck with seventeen. The stegosaurian shoulder girdle
7128-432: The wetland ecosystem . Such differences in herbivore modalities can potentially lead to trade-offs that influence species traits and may lead to additive effects on community composition and ecosystem functioning. Seasonal changes and environmental gradients such as elevation and latitude often affect the palatability of plants which in turn influences herbivore community assemblages and vice versa. Examples include
7260-553: The French finds naming them as a separate new genus: Loricatosaurus . This made Lexovisaurus a nomen dubium , while O. vetustus was found to be undiagnostic and declared a nomen dubium . Other workers though, combining the English material collected by Leeds due to its shared provenance, have considered Lexovisaurus a valid taxon . In the meantime, Omosaurus vetustus has been renamed Eoplophysis , although this genus
7392-533: The Jurassic and early Cretaceous, and which were defined by Paul Sereno as all stegosaurians more closely related to Stegosaurus than to Huayangosaurus . This definition was also formalized in the PhyloCode by Daniel Madzia and colleagues in 2021 as "the largest clade containing Stegosaurus stenops , but not Huayangosaurus taibaii ". They include per definition the well-known Stegosaurus . This group
7524-662: The Middle Jurassic ( Aalenian ) of England represent the oldest probable record of stegosaurians reported so far. Outside that, there are assigned fossils to stegosauria from the Toarcian : the specimen "IVPP V.219", a chimaera with bones of the sauropod Sanpasaurus is known from the Maanshan Member of the Ziliujing Formation . The earliest possible trackways of stegosaurians are discovered from
7656-595: The Middle to Upper Jurassic (Callovian–Tithonian). A single plaster cast of one of these handprints is in the collections of the Queensland Museum . There has been debate about whether the spikes were used simply for display, as posited by Gilmore in 1914, or used as a weapon. Robert Bakker noted that it is likely that the stegosaur tail was much more flexible than those of other ornithischian dinosaurs because it lacked ossified tendons, thus lending credence to
7788-827: The Stegosauridae-Huayangosauridae split. Huayangosauridae was formally defined in 2021 by Daniel Madzia and colleagues, who used the previous definitions of all taxa closer to Huayangosaurus taibaii than Stegosaurus stenops . In 2017, Raven and Maidment published a new phylogenetic analysis, including almost every known stegosaurian genus: Laquintasaura venezuelae Emausaurus ernsti Scelidosaurus harrisonii [REDACTED] Gastonia burgei Euoplocephalus tutus To date, several genera from China bearing names have been proposed but not formally described, including " Changdusaurus ". Until formal descriptions are published, these genera are regarded as nomina nuda . Yingshanosaurus , for
7920-515: The U.S. Herbivores also affect economics through the revenue generated by hunting and ecotourism. For example, the hunting of herbivorous game species such as white-tailed deer, cottontail rabbits, antelope, and elk in the U.S. contributes greatly to the billion-dollar annually, hunting industry. Ecotourism is a major source of revenue, particularly in Africa, where many large mammalian herbivores such as elephants, zebras, and giraffes help to bring in
8052-439: The animal has stopped growing”. Paidan also expressed ethical concerns about the use of private specimens in the study. Kentrosaurus , Dacentrurus and Stegosaurus are also suggested to have exhibited dimorphism in the form of three extra sacral ribs in the females. In order to explore the feeding habits of stegosaurids, Reichel (2010) created a 3-D model of Stegosaurus teeth using the software ZBrush . The model finds that
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#17327913856578184-440: The area of the present state of South Africa , remains were discovered that much later would be named Paranthodon . In 1874, other remains from England were named Craterosaurus . All three taxa were based on fragmentary material and were not recognised as possible stegosaurians until the twentieth century. They gave no reason to suspect the existence of a new distinctive group of dinosaurs. In 1874, extensive remains of what
8316-416: The balance between eating all the food in a patch for immediate energy, or moving to a new patch and leaving the plants in the first patch to regenerate for future use. The theory predicts that absent complicating factors, an animal should leave a resource patch when the rate of payoff (amount of food) falls below the average rate of payoff for the entire area. According to this theory, an animal should move to
8448-445: The beaks of modern birds. At the same time this finding implies that the use of plates for thermo-regulation may be less likely because the keratinous covering would make heat transfer from the bone highly ineffective. In 1877, Othniel Marsh discovered and named Stegosaurus armatus , from which the name of the family ‘Stegosauridae’ was erected in 1880. In comparison to basal stegosaurians, notable synapomorphies of Stegosauridae include
8580-466: The bite forces of Stegosaurus was significantly weaker than that of Labradors , wolves and humans. The finding suggests that these dinosaurs would be capable of breaking smaller branches and leaves with their teeth, but would not be able to bite through a thick object (12 mm or more in diameter). Parrish et al .’s (2004) description of Jurassic flora in the stegosaurid-rich Morrison Formation supports this finding. The flora during this time-period
8712-655: The centrum. This is more than most sauropod dinosaurs, which also achieved the elongation of the neck through similar mechanisms and had access to fodder higher off the ground. 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 non-vascular autotrophs such as mosses , algae and lichens , but do not include those feeding on decomposed plant matters (i.e. detritivores ) or macrofungi (i.e. fungivores ). As
8844-824: The colonization and community assembly of herbivores, and there is evidence of phylogenetic linkage between plant beta diversity and phylogenetic beta diversity of insect clades such as butterflies . These types of eco-evolutionary feedbacks between plants and herbivores are likely the main driving force behind plant and herbivore diversity. Abiotic factors such as climate and biogeographical features also impact plant-herbivore communities and interactions. For example, in temperate freshwater wetlands herbivorous waterfowl communities change according to season, with species that eat above-ground vegetation being abundant during summer, and species that forage below-ground being present in winter months. These seasonal herbivore communities differ in both their assemblage and functions within
8976-523: The derived Stegosauridae . Lexovisaurus and Loricatosaurus , stegosaurid finds from England and France of approximately equivalent age to the Chinese specimens, are likely the same taxon . During the Late Jurassic , stegosaurids seem to have experienced their greatest radiation. In Europe, Dacentrurus and the closely related Miragaia were present. While older finds had been limited to
9108-495: The description of Huayangosaurus . Huayangosaurinae was originally differentiated by the remaining taxa within Stegosauridae by the presence of teeth in the premaxilla , an antorbital fenestra , and a mandibular fenestra . Huayangosaurinae, known from the Middle Jurassic of the Shaximiao Formation , was proposed to be intermediate between Scelidosaurinae and Stegosaurinae , suggesting that
9240-424: The effectiveness of plant defenses activated by sunlight. A plant defense is a trait that increases plant fitness when faced with herbivory. This is measured relative to another plant that lacks the defensive trait. Plant defenses increase survival and/or reproduction (fitness) of plants under pressure of predation from herbivores. Defense can be divided into two main categories, tolerance and resistance. Tolerance
9372-538: The end of that period. Herbivory among four-limbed terrestrial vertebrates, the tetrapods , developed in the Late Carboniferous (307–299 million years ago). The oldest known example being Desmatodon hesperis. Early tetrapods were large amphibious piscivores . While amphibians continued to feed on fish and insects, some reptiles began exploring two new food types, tetrapods (carnivory) and plants (herbivory). The entire dinosaur order ornithischia
9504-406: The equivalent of millions of US dollars to various nations annually. Lexovisaurus Lexovisaurus is a genus of stegosaur from mid-to-Late Jurassic Europe , 165.7-164.7 mya . Fossils of limb bones and armor fragments have been found in middle to late Jurassic-aged strata of England and France . In the early 1880s collector Alfred Nicholson Leeds acquired a skeleton of
9636-493: The first land plants evolved. Insects fed on the spores of early Devonian plants, and the Rhynie chert also provides evidence that organisms fed on plants using a "pierce and suck" technique. During the next 75 million years , plants evolved a range of more complex organs, such as roots and seeds. There is no evidence of any organism being fed upon until the middle-late Mississippian , 330.9 million years ago . There
9768-533: The first relatively complete skeletons from the Middle Jurassic and the Early Cretaceous . Especially important was Huayangosaurus , which provided unique information about the early evolution of the group. Towards the end of the twentieth century, the so-called Dinosaur Renaissance took place in which a vast increase in scientific attention was given to the Dinosauria. In 2007, Jiangjunosaurus
9900-596: The food chain because they consume plants to digest the carbohydrates photosynthetically produced by a plant. Carnivores in turn consume herbivores for the same reason, while omnivores can obtain their nutrients from either plants or animals. Due to a herbivore's ability to survive solely on tough and fibrous plant matter, they are termed the primary consumers in the food cycle (chain). Herbivory, carnivory, and omnivory can be regarded as special cases of consumer–resource interactions . Two herbivore feeding strategies are grazing (e.g. cows) and browsing (e.g. moose). For
10032-565: The food source, in this case, the plant. Several factors play into these fluctuating populations and help stabilize predator-prey dynamics. For example, spatial heterogeneity is maintained, which means there will always be pockets of plants not found by herbivores. This stabilizing dynamic plays an especially important role for specialist herbivores that feed on one species of plant and prevents these specialists from wiping out their food source. Prey defenses also help stabilize predator-prey dynamics, and for more information on these relationships see
10164-422: The forefeet. Fossil remains indicate that stegosaurians have five digits on the forefeet and three weight-bearing digits on the hind feet. From this, scientists were able to predict the appearance of stegosaurian tracks in 1990, six years in advance of the first actual discovery of Morrison stegosaurian tracks. More trackways have been found since the erection of Stegopodus . None, however, have preserved traces of
10296-426: The forested habitat and its interaction with other deer while in that habitat. This model has been criticized as circular and untestable. Critics have pointed out that its proponents use examples that fit the theory, but do not use the model when it does not fit the reality. Other critics point out that animals do not have the ability to assess and maximize their potential gains, therefore the optimal foraging theory
10428-832: The fossil record of their jaws near the Permio-Carboniferous boundary, approximately 300 million years ago. The earliest evidence of their herbivory has been attributed to dental occlusion , the process in which teeth from the upper jaw come in contact with teeth in the lower jaw is present. The evolution of dental occlusion led to a drastic increase in plant food processing and provides evidence about feeding strategies based on tooth wear patterns. Examination of phylogenetic frameworks of tooth and jaw morphologes has revealed that dental occlusion developed independently in several lineages tetrapod herbivores. This suggests that evolution and spread occurred simultaneously within various lineages. Herbivores form an important link in
10560-495: The fossils are demonstrably stegosaurian. The reinterpretation of Dravidosaurus as a plesiosaur wasn't accepted by Galton and Upchurch (2004), who stated that the skull and plates of Dravidosaurus are certainly not plesiosaurian, and noted the need to redescribe the fossil material of Dravidosaurus . A purported stegosaurian dermal plate was reported from the latest Cretaceous ( Maastrichtian ) Kallamedu Formation (southern India); however, Galton & Ayyasami (2017) interpreted
10692-533: The front feet and stegosaurian traces remain rare. Deltapodus is an ichnogenus attributed as stegosaurian prints, and are known across Europe, North Africa, and China. One Deltapodus footprint measures less than 6 cm in length and represents the smallest known stegosaurian track. Some tracks preserve exquisite scaly skin pattern. Australia's 'Dinosaur Coast' in Broome , Western Australia includes tracks of several different thyreophoran track-makers. Of these,
10824-400: The front to the rear. This would have limited the supported rotation of the knee joint, making running impossible. Huayangosaurus had a thighbone like a running animal. The upper leg was always longer than the lower leg. Huayangosaurus had relatively long and slender arms. The forelimbs of later forms are very robust, with a massive humerus and ulna . The wrist bones were reinforced by
10956-575: The ichnogenus Garbina (a Nyulnyulan word for 'shield') and Luluichnus (honours the late Paddy Roe, OAM who went by the name 'Lulu') have been considered registered by stegosaurs. Garbina includes the largest stegosaur tracks measuring 80 cm in length. Trackway data show Garbina track-makers were capable of bipedal and quadrupedal progression. While has no body fossil evidence currently known for stegosaurs, handprints from underground coal mines near Oakey , Queensland, resembling Garbina tracks suggests their occurrence in this country from at least
11088-400: The idea of the tail as a weapon. He also observed that Stegosaurus could have maneuvered its rear easily by keeping its large hindlimbs stationary and pushing off with its very powerfully muscled but short forelimbs, allowing it to swivel deftly to deal with attack. In 2010, analysis of a digitized model of Kentrosaurus aethiopicus showed that the tail could bring the thagomizer around to
11220-430: The incorporation of silica into cell walls is analogous to that of the role of lignin in that it is a compression-resistant structural component of cell walls; so that plants with their cell walls impregnated with silica are thereby afforded a measure of protection against herbivory. Chemical defenses are secondary metabolites produced by the plant that deter herbivory. There are a wide variety of these in nature and
11352-406: The interaction of herbivory and plant defense is negative, with one individual reducing the fitness of the other, some is beneficial. This beneficial herbivory takes the form of mutualisms in which both partners benefit in some way from the interaction. Seed dispersal by herbivores and pollination are two forms of mutualistic herbivory in which the herbivore receives a food resource and the plant
11484-479: The large axial channel in old adults from small canals in young adults, facilitated the further enlargement of the spikes by increasing the amount of nourishment supplied. On the other hand, plates do not show a similar degree of bone compaction or cortical thickening indicating they would not be capable of taking much weight from above. This suggests they were not as important as spikes in active defense. The protective nature of dorsal plates has also been questioned in
11616-465: The latter's skull roof. In 1915 Omosaurus durobrivensis was renamed Dacentrurus durobrivensis , as the name Omosaurus had been preoccupied, which had already been indicated by Marsh in the 1870s. In 1957 the French palaeontologist Robert Hoffstetter created a separate genus for the species: Lexovisaurus . The generic name is derived from the Lexovii , a Gallic tribe in ancient times inhabiting
11748-407: The metabolic rate (q 0 ) of an animal is the mass of the animal (M) raised to the 3/4 power: q 0 =M Therefore, the mass of the animal increases at a faster rate than the metabolic rate. Herbivores employ numerous types of feeding strategies. Many herbivores do not fall into one specific feeding strategy, but employ several strategies and eat a variety of plant parts. Optimal foraging theory
11880-584: The method of cladistics , allowing for the first time to exactly calculate stegosaurian evolutionary relationships. Stegosaurids are distinguished from other stegosaurians in that the former have lost the plesiomorphic pre-maxillary teeth and lateral scute rows along the trunk. Furthermore, stegosaurids have long narrow skulls and longer hindlimbs compared to their forelimbs. However, these two features are not diagnostic of Stegosauridae because they may also be present in non-stegosaurid stegosaurians. Stegosaurians had characteristic small, long, flat, narrow heads and
12012-488: The northern continents, in this phase Gondwana was colonised also as shown by Kentrosaurus living in Africa . No unequivocal stegosaurian fossils have been reported from South-America , India, Madagascar , Australia, or Antarctica , though. A Late Jurassic Chinese stegosaurian is Jiangjunosaurus . The most derived Jurassic stegosaurians are known from North-America : Stegosaurus (perhaps several species thereof) and
12144-685: The only substantial discoveries were those of Wuerhosaurus from Northern China, the exact age of which is highly uncertain More recent discoveries from Asia however would later begin to fill out the Early Cretaceous diversity of the group. Indeterminate stegosaurs are known from the Early Cretaceous of Siberia , including the Ilek Formation and Batylykh Formation . The youngest known definitive remains of stegosaurs are those of Mongolostegus from Mongolia, possibly Stegosaurus from
12276-451: The ontogeny, the dorsal osteoderms are composed of dense ossified collagen fibres in both the cortical and cancellous sections of the bone, suggesting that plates and spikes are formed from the direct mineralization of already existing fibrous networks in the skin. However, the many structural features, seen in the spikes and plates of old adults specimens, are acquired at different stages of development. Extensive vascular networks form in
12408-528: The origins of stegosaurs lay in Asia. Following phylogenetic analyses, Huayangosauridae was expanded to also include the taxon Chungkingosaurus , known from specimens from younger Late Jurassic deposits of the Shaximiao Formation. Huayangosauridae is either the sister taxon to all other stegosaurs, or close to the origin of the clade, with taxa like Gigantspinosaurus or Isaberrysaura outside
12540-468: The past Davitashvili (1961) noted that narrow dorsal location of the plates still left the sides vulnerable. Since the pattern of plates and spines vary between species, he suggested it could be important for intraspecific recognition and as a display for sexual selection. This is corroborated by Spassov's (1982) observations that the plates are arranged for maximum visible effect when viewed laterally during non-aggressive agonistic behaviour, as opposed to from
12672-402: The patch quality. Interactions between plants and herbivores can play a prevalent role in ecosystem dynamics such community structure and functional processes. Plant diversity and distribution is often driven by herbivory, and it is likely that trade-offs between plant competitiveness and defensiveness , and between colonization and mortality allow for coexistence between species in
12804-570: The plant, or induced, produced or translocated by the plant following damage or stress. Physical, or mechanical, defenses are barriers or structures designed to deter herbivores or reduce intake rates, lowering overall herbivory. Thorns such as those found on roses or acacia trees are one example, as are the spines on a cactus. Smaller hairs known as trichomes may cover leaves or stems and are especially effective against invertebrate herbivores. In addition, some plants have waxes or resins that alter their texture, making them difficult to eat. Also
12936-419: The plates during the change from juveniles to young adults and persist in old adults but spikes acquire a thick cortex with a large axial vascular channel only in old adults. Hayashi et al . argue that the formation of nourishing vascular networks in young adults supported the growth of large plates. This would have enhanced the size of the animal, which may have helped attract mates and deter rivals. Furthermore,
13068-424: The possible functions of these dorsal plates, a study of the ontogenetic histology of the plates and spikes suggests that the plates serve different functions at different stages of the stegosaurids’ life histories. The terminal spikes in the tail are thought to have been used in old adults, at least, as a weapon for defence. However, the function of stegosaurid plates and spikes, at different life stages, still remains
13200-538: The presence of herbivores. However, the effects of herbivory on plant diversity and richness is variable. For example, increased abundance of herbivores such as deer decrease plant diversity and species richness , while other large mammalian herbivores like bison control dominant species which allows other species to flourish. Plant-herbivore interactions can also operate so that plant communities mediate herbivore communities. Plant communities that are more diverse typically sustain greater herbivore richness by providing
13332-455: The presence of the vascular networks in the plates of the young adult indicate a secondary use of the plates as a thermoregulatory device for heat loss much like the elephant ear, toucan bill or alligator osteoderms. The thickening of the cortical section of the bone and the compaction of bone in the terminal tail-spikes in old adults suggest that they were used as defence weapons, but not until an ontogenetically late stage. The development of
13464-485: The primitive Huayangosauridae and the more derived Stegosauridae . The stegosaurids like all other stegosaurians were quadrupedal herbivores that exhibited the characteristic stegosaurian dorsal dermal plates. These large, thin, erect plates are thought to be aligned parasagittally from the neck to near the end of the tail. The end of the tail has pairs of spikes, sometimes referred to as a thagomizer . Although defense, thermo-regulation and display have been theorized to be
13596-403: The production of large amounts of saliva to reduce effectiveness of defenses. Herbivores may also utilize symbionts to evade plant defenses. For example, some aphids use bacteria in their gut to provide essential amino acids lacking in their sap diet. Plant modification occurs when herbivores manipulate their plant prey to increase feeding. For example, some caterpillars roll leaves to reduce
13728-402: The rear, while the front prepubic process lengthened. Like all Thyreophora , stegosaurians were protected by bony scutes that were not part of the skeleton proper but skin ossifications instead: the so-called osteoderms . Huayangosaurus had several types. On its neck, back, and tail were two rows of paired small vertical plates and spikes. The very tail end bore a small club. Each flank had
13860-512: The region of Normandy , where several stegosaurian specimens had been discovered which by Hoffstetter were referred to Lexovisaurus . While the type species remains Omosaurus durobrivensis , the combinatio nova is Lexovisaurus durobrivensis . Hofstetter also referred a much more complete stegosaurian skeleton in 1901 discovered by Leeds in the Fletton brick pit, specimen BMNH R3167 that in 1911 had been named Stegosaurus priscus , placed as
13992-407: The relatively short torso towards the front curved strongly downwards. The dorsal vertebrae typically were very high, with very tall neural arches and transverse processes pointing obliquely upwards to almost the level of the neural spine top. Stegosaurian back vertebrae can easily be identified by this unique configuration. The tall neural arches often house deep neural canals ; enlarged canals in
14124-424: The same size and shape, making the possibility of bilaterally paired rows even less likely. Plates are usually found with distinct vascular grooves on their lateral surfaces, suggesting the presence of a circulatory network. Stegosaurids also have osteoderms on the throat in the form of small depressed ossicles and two pairs of elongated spike-like tail-spines. With Stegosaurus fossils also ossicles have been found in
14256-620: The scapula. The stegosaurian pelvis was originally moderately large, as shown by Huayangosaurus . Later species, however, convergent to the Ankylosauria developed very broad pelves , in which the iliac bones formed wide horizontal plates with flaring front blades to allow for an enormous belly-gut. The ilia were attached to the sacral vertebrae via a sacral yoke formed by fused sacral ribs. Huayangosaurus still had rather long and obliquely oriented ischia and pubic bones . In more derived species, these became more horizontal and shorter to
14388-490: The section on Plant Defenses. Eating a second prey type helps herbivores' populations stabilize. Alternating between two or more plant types provides population stability for the herbivore, while the populations of the plants oscillate. This plays an important role for generalist herbivores that eat a variety of plants. Keystone herbivores keep vegetation populations in check and allow for a greater diversity of both herbivores and plants. When an invasive herbivore or plant enters
14520-633: The sides of the dinosaur, possibly striking an attacker beside it. In 2001, a study of tail spikes by McWhinney et al., showed a high incidence of trauma-related damage. This too supports the theory that the spikes were used in combat. There is also evidence for Stegosaurus defending itself, in the form of an Allosaurus tail vertebra with a partially healed puncture wound that fits a Stegosaurus tail spike. Stegosaurus stenops had four dermal spikes, each about 60–90 cm (2–3 ft) long. Discoveries of articulated stegosaur armor show that, at least in some species, these spikes protruded horizontally from
14652-556: The size of herbivores having an effect on the amount of energy intake that is needed, larger herbivores need to forage on higher quality or more plants to gain the optimal amount of nutrients and energy compared to smaller herbivores. Environmental degradation from white-tailed deer ( Odocoileus virginianus ) in the US alone has the potential to both change vegetative communities through over-browsing and cost forest restoration projects upwards of $ 750 million annually. Another example of
14784-426: The skin was smooth with long, parallel, shallow grooves indicating a keratinous structure covering the plates. The addition of beta-keratin , a strong protein, would indeed allow the plates to bear more weight, suggesting they may have been used for active defense. A keratinous covering would also allow greater surface area for the plates to be uses as a mating display structures, which could be potentially coloured like
14916-489: The skull. A succession of additional discoveries from the Como Bluff sites allowed a quick update of the presumed build. In 1882, Marsh was able to publish the first skeletal reconstruction of a stegosaur. Hereby, stegosaurians became much better known to the general public. The American finds at the time represented the bulk of known stegosaurian fossils, with about twenty skeletons collected. The next important discovery
15048-445: The somewhat older Hesperosaurus . Stegosaurus was quite large (some specimens indicate a length of at least seven metres), had high plates, no shoulder spine, and a short, deep rump. From the Early Cretaceous , far fewer finds are known and it seems that the group had declined in diversity. Some fragmentary fossils have been described, such as Craterosaurus from England and Paranthodon from South Africa . Up until recently,
15180-625: The specimen as a bone of a sauropod dinosaur. Nevertheless, the authors considered the survival of stegosaurians into the Maastrichtian to be possible, noting the presence of the stegosaurian ichnotaxon Deltapodus in the Maastrichtian Lameta Formation (western India). In an ontogenetic histological analysis of Stegosaurus plates and spikes, Hayashi et al . (2012) examined their structure and function through juveniles to old adults. They found that throughout
15312-453: The system, the balance is thrown off and the diversity can collapse to a monotaxon system. The back and forth relationship of plant defense and herbivore offense drives coevolution between plants and herbivores, resulting in a "coevolutionary arms race". The escape and radiation mechanisms for coevolution, presents the idea that adaptations in herbivores and their host plants, has been the driving force behind speciation . While much of
15444-452: The tail, not vertically as is often depicted. Initially, Marsh described S. armatus as having eight spikes in its tail, unlike S. stenops . However, recent research re-examined this and concluded this species also had four. A digital articulation and manipulation of digital scans of specimen material of Kentrosaurus inferred that stegosaurids may have used an erect limb posture, like that of most mammals, for habitual locomotion while using
15576-485: The theme. The understanding of herbivory in geological time comes from three sources: fossilized plants, which may preserve evidence of defence (such as spines), or herbivory-related damage; the observation of plant debris in fossilised animal faeces ; and the construction of herbivore mouthparts. Although herbivory was long thought to be a Mesozoic phenomenon, fossils have shown that plants were being consumed by arthropods within less than 20 million years after
15708-421: The theory of predator –prey interactions, the relationship between herbivores and plants is cyclic. When prey (plants) are numerous their predators (herbivores) increase in numbers, reducing the prey population, which in turn causes predator number to decline. The prey population eventually recovers, starting a new cycle. This suggests that the population of the herbivore fluctuates around the carrying capacity of
15840-422: The thighbones backwards. However, it has been suggested by Robert Thomas Bakker that stegosaurians could rear on their hind legs to reach higher layers of plants, the tail then being used as a "third leg". The mobility of the tail was increased by a reduction or absence of ossified tendons, that with many Ornithischia stiffen the hip region. Huayangosaurus still possessed them. In species that had short forelimbs,
15972-489: The throat region, bony skin discs that protected the lower neck. Many basal stegosaurs like Gigantspinosaurus and Huayangosaurus have been discovered with parascapular spines, or spines emerging from the shoulder region. Among stegosaurids, only Kentrosaurus has been found with parascapular spines, which project posteriorly out of the lower part of the shoulder plates. These spines are long, rounded and comma-shaped in lateral view and have an enlarged base. Loricatosaurus
16104-430: The tripodal stance would also give them access to young trees and high bushes. Another piece of evidence suggesting that some stegosaurids may have consumed more than just low vegetation was the discovery of the long-necked stegosaurid Miragaia longicollum . This dinosaur's neck has at least 17 cervical vertebrae achieved through the transformation of thoracic vertebrae into cervical vertebrae and possible lengthening of
16236-429: Was a gap of 50 to 100 million years between the time each organ evolved and the time organisms evolved to feed upon them; this may be due to the low levels of oxygen during this period, which may have suppressed evolution. Further than their arthropod status, the identity of these early herbivores is uncertain. Hole feeding and skeletonization are recorded in the early Permian , with surface fluid feeding evolving by
16368-541: Was also believed to have a parascapular spine, but Maidment et al . (2008) observed that the discovered specimen, from which the spine is described, has a completely different morphology than the parascapular spine specimens of other stegosaurs. They suggest it may be a fragmentary tail spine instead. Stegosaurids also lack lateral scute rows that run longitudinally on either side of the trunk in Huayangosaurus and ankylosaurs , indicating yet another secondary loss of
16500-542: Was clearly a large herbivore equipped with spikes were uncovered in England; the first partial stegosaurian skeleton known. They were named Omosaurus by Richard Owen in 1875. Later, this name was shown to be preoccupied by the phytosaur Omosaurus and the stegosaurian was renamed Dacentrurus . Other English nineteenth century and early twentieth century finds would be assigned to Omosaurus ; later they would, together with French fossils, be partly renamed Lexovisaurus and Loricatosaurus . In 1877, Arthur Lakes ,
16632-431: Was composed of herbivorous dinosaurs. Carnivory was a natural transition from insectivory for medium and large tetrapods, requiring minimal adaptation. In contrast, a complex set of adaptations was necessary for feeding on highly fibrous plant materials. Arthropods evolved herbivory in four phases, changing their approach to it in response to changing plant communities. Tetrapod herbivores made their first appearance in
16764-501: Was dominated by seasonal small, fast-growing herbaceous plants, which stegosaurids could consume easily if Reichel's reconstruction is accurate. Mallison (2010) suggested that Kentrosaurus may have used a tripodal stance on their hindlimbs and tail to double the foraging height from the general low browsing height under one metre for stegosaurids. This challenged the view that stegosaurs are primarily low vegetation feeders because of their small heads, short necks and short forelimbs, since
16896-593: Was formalized in the PhyloCode by Daniel Madzia and colleagues in 2021 as "the largest clade containing Stegosaurus stenops , but not Ankylosaurus magniventris ". Thus defined, the Stegosauria are by definition the sister group of the Ankylosauria within the Eurypoda . The vast majority of stegosaurian dinosaurs thus far recovered belong to the Stegosauridae, which lived in the later part of
17028-483: Was found in the Bathonian Shaximiao Formation of China. Stegosaurians were armored dinosaurs ( thyreophorans ). Originally, they did not differ much from more primitive members of that group, being small, low-slung, running animals protected by armored scutes . An early evolutionary innovation was the development of spikes as defensive weapons. Later species, belonging to a subgroup called
17160-475: Was made when a German expedition to the Tendaguru , then part of German East Africa , from 1909 to 1912 excavated over a thousand bones of Kentrosaurus . The finds increased the known variability of the group, Kentrosaurus being rather small and having long rows of spikes on the hip and tail. From the 1950s onwards, the geology of China was systematically surveyed in detail and infrastructural works led to
17292-585: Was reported, the first Chinese dinosaur named since 1994. Nevertheless, European and North-American sites have become productive again during the 1990s, Miragaia having been found in the Lourinhã Formation in Portugal and a number of relatively complete Hesperosaurus skeletons having been excavated in Wyoming. Apart from the fossils per se, important new insights have been gained by applying
17424-403: Was very robust. In Huayangosaurus , the acromion , a process on the lower front edge of the shoulderblade , was moderately developed; the coracoid was about as wide as the lower end of the scapula , with which it formed the shoulder joint . Later forms tend to have a strongly expanded acromion, while the coracoid, largely attached to the acromion, no longer extends to the rear lower corner of
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