nandi's blog

Lambeosaurus

Wednesday, November 30, 2016

Lambeosaurus reconstruction

Lambeosaurus (meaning “Lambe’s lizard”) is a genus of hadrosaurid dinosaur that lived about 75 million years ago, in the Late Cretaceous period (Campanian) of North America. This bipedal/quadrupedal, herbivorous dinosaur is known for its distinctive hollow cranial crest, which in the best-known species resembled a hatchet. Several possible species have been named, from Canada, the United States, and Mexico, but only the two Canadian species are currently recognized as valid.

L. lambei compared to a human by Dinoguy2

Lambeosaurus was belatedly described in 1923 by William Parks, over twenty years after the first material was studied by Lawrence Lambe. The genus has a complicated taxonomic history, in part because small-bodied crested hadrosaurids now recognized as juveniles were once thought to belong to their own genera and species. Currently, the various skulls assigned to the type speciesL. lambei are interpreted as showing age differences and sexual dimorphism. Lambeosaurus was closely related to the better known Corythosaurus, which is found in slightly older rocks, as well as the less well-known genera Hypacrosaurus and Olorotitan. All had unusual crests, which are now generally assumed to have served social functions like noisemaking and recognition.

Restoration of a crouched L. lambei by ДиБгд at Russian Wikipedia Tail and hands fixed by FunkMonk.

As in other lambeosaurines, the hollow crest would have formed a resonating chamber for its calls, amplifying them and making a distinctive sound in each species. The shape and patterning of the crest would also have helped individuals to recognize each other in the herd.

Lambeosaurus, best known through L. lambei, was quite similar to Corythosaurus in everything but the form of the head adornment. Compared to Corythosaurus, the crest of Lambeosaurus was shifted forward, and the hollow nasal passages within were at the front of the crest and stacked vertically. It also can be differentiated from Corythosaurus by its lack of forking nasal processes making up part of the sides of the crest, which is the only way to tell juveniles of the two genera apart, as the crests took on their distinctive forms as the animals aged.

Lambeosaurus was like other hadrosaurids, and could move on both two legs and all fours, as shown by footprints of related animals. It had a long tail stiffened by ossified tendons that prevented it from drooping. The hands had four fingers, lacking the innermost finger of the generalized five-fingered tetrapod hand, while the second, third, and fourth fingers were bunched together and bore hooves, suggesting the animal could have used the hands for support. The fifth finger was free and could be used to manipulate objects. Each foot had only the three central toes.

Skull of an adult Lambeosaurus lambei, AMNH. Photo by Ryan Somma

Some Lambeosaurus fossils display detailed impressions of the skin, showing that the skin of the body had a “pebbly” texture and that a weblike sheath of skin joined the fingers. When they were first described, these “webbed hands” were thought to prove the now-out-moded idea that duckbills were aquatic. The “web” actually enclosed a fleshy pad on the palm like that on a camel’s foot.

Lambeosaurus is the type genus of the Lambeosaurinae, the subfamily of hadrosaurids that had hollow skull crests. Among the lambeosaurines, it is closely related to similar dinosaurs such as Corythosaurus and Hypacrosaurus, with little separating them but crest form. The relationships among these dinosaur genera are difficult to pick out. Some early classifications placed these genera in the tribe Corythosaurini, which was found by David Evans and Robert Reisz to include Lambeosaurusas the sister taxon to a clade made up of CorythosaurusHypacrosaurus, and the Russian genus Olorotitan; these lambeosaurines, with Nipponosaurus.

Kentrosaurus

Wednesday, November 30, 2016

Kentrosaurus by Mueller Art

Kentrosaurus is a genus of stegosaurian dinosaur from the Late Jurassic of Tanzania. The type species is K. aethiopicus, named and described by German palaeontologist Edwin Hennig in 1915. Often thought to be a “primitive” member of the Stegosauria, several recent cladistic analyses find it as more derived than many other stegosaurs, and a close relative of Stegosaurus from the North American Morrison Formation within the Stegosauridae.

Fossils of K. aethiopicus have been found only in the Tendaguru Formation, dated to the late Kimmeridgian and early Tithonian ages, about 152 million years ago. Hundreds of bones were unearthed by German expeditions to German East Africa between 1909 and 1912. Although no complete skeletons are known, the remains provided a nearly complete picture of the build of the animal.

Kentrosaurus skeleton by nikkitikokathi @Flickr

Kentrosaurus was named by the German paleontologist Edwin Henning in 1915, as World War 1 raged, It is ironic that it became one of the many fossil victims of World War 11. One of the two skeletons of Kentrosaurus that were pieced together from the hundreds of bones taken back to Germany was on display in the Humboldt Museum in Berlin and was destroyed during Allied bombing of the city. it has since been replaced by a copy of the second skeleton, which is still on display in Tubingen. The illustration is based on this skeleton but recent evidence from China places the pelvic spike now on the shoulder.
 
Kentrosaurus generally measured around 4.5 metres (15 ft) in length as an adult, and weighed about one tonne (1.1 tons). It walked on all fours with straight hindlimbs. It had a small, elongated head with a beak used to bite off plant material that would be digested in a large gut. It had a, probably double, row of small plates running down its neck and back. These plates gradually merged into spikes on the hip and tail. The longest spikes were on the tail end and were used to actively defend the animal. There also was a long spine on each shoulder. The thigh bones come in two different types, suggesting that one sex was larger and more stout than the other.

Iguanodon

Wednesday, November 30, 2016

A pair of Iguanodon bernissartensis grazing Belgium Early Cretaceous Period Ardeosaurus in foreground Archaeopteryx in background

Iguanodon (meaning “iguana-tooth”) is a genus of ornithopod dinosaur that existed roughly halfway between the first of the swift bipedal hypsilophodontids of the mid-Jurassic and the duck-billed dinosaurs of the late Cretaceous. While many species have been classified in the genus Iguanodon, dating from the late Jurassic Period to the early Cretaceous Period of Asia, Europe, and North America, research in the first decade of the 21st century suggests that there is only one well-substantiated species: I. bernissartensis, which lived from the late Barremian to the earliest Aptian ages (Early Cretaceous) in Belgium, Spain, and possibly elsewhere in Europe, between about 126 and 125 million years ago. Iguanodon were large, bulky herbivores. Distinctive features include large thumb spikes, which were possibly used for defense against predators, combined with long prehensile fifth fingers able to forage for food.

The genus was named in 1825 by English geologist Gideon Mantell, based on fossil specimens that are now assigned to Therosaurus and MantellodonIguanodon was the second type of dinosaur formally named based on fossil specimens, after Megalosaurus. Together with Megalosaurus and Hylaeosaurus, it was one of the three genera originally used to define Dinosauria. The genus Iguanodon belongs to the larger group Iguanodontia, along with the duck-billed hadrosaurs. The taxonomy of this genus continues to be a topic of study as new species are named or long-standing ones reassigned to other genera.

I. bernissartensis skull and neck. Photo by Ghedoghedo

Scientific understanding of Iguanodon has evolved over time as new information has been obtained from fossils. The numerous specimens of this genus, including nearly complete skeletons from two well-known bonebeds, have allowed researchers to make informed hypotheses regarding many aspects of the living animal, including feeding, movement, and social behaviour. As one of the first scientifically well-known dinosaurs, Iguanodon has occupied a small but notable place in the public’s perception of dinosaurs, its artistic representation changing significantly in response to new interpretations of its remains.

Thumb spike

The thumb spike is one of the best-known features of Iguanodon. Although it was originally placed on the animal’s nose by Mantell, the complete Bernissart specimens allowed Dollo to place it correctly on the hand, as a modified thumb. (This would not be the last time a dinosaur’s modified thumb claw would be misinterpreted; NoasaurusBaryonyx, and Megaraptorare examples since the 1980s where an enlarged thumb claw was first put on the foot, as in dromaeosaurids.)

Hand of Iguanodon shown in the Natural History Museum. Credit to: Ballista.

This thumb is typically interpreted as a close-quarter stiletto-like weapon against predators, although it could also have been used to break into seeds and fruits, or against other Iguanodon. One author has suggested that the spike was attached to a venom gland, but this has not been accepted, as the spike was not hollow, nor were there any grooves on the spike for conducting venom.

Hypsilophodon

Wednesday, November 30, 2016

Hypsilophodon skeleton

Hypsilophodon (meaning “Hypsilophus-tooth”) is an ornithopod dinosaur genus from the Early Cretaceous period of England.

The first remains of Hypsilophodon were found in 1849; the type species, Hypsilophodon foxii, was named in 1869. Abundant fossil discoveries were made on the Isle of Wight, giving a good impression of the build of the species. It was a small bipedal animal with an herbivorous or possibly omnivorous diet. Hypsilophodon reached up to 1.8 metres (5.9 ft) in length, weighed about 20 kg (45 lbs), and was an agile runner. It had a pointed head equipped with a sharp beak used to bite off plant material, much like modern day parrots.

Hypsilophodon foxii specimens NHM 28707, 39560-1. Original description: Chief part of the vertebral column, with some bones of the extremities, of a young Iguanodon; nat. size. From the Wealden of Cowleaze Chine, Isle of Wight. In the British Museum, and that of J. S. Bowerbank, Esq., F.R.S.

Older studies have given rise to number of misconceptions about Hypsilophodon: that it would climb trees, were armoured, reached a length of 2.3 metres (7.5 ft) and were also found outside of Wight. During the past decades new research has gradually shown this to be incorrect.

Hypsilophodon was a relatively small dinosaur, though not quite so small as, for example, Compsognathus. For Hypsilophodonoften a maximum length of 2.3 metres is stated. This has its origin in a study of 1974 by Galton, in which he extrapolated a length of 2.28 metres based on specimen BMNH R 167, a thigh bone. However, in 2009, Galton concluded that this femur in fact belonged to Valdosaurus and downsized Hypsilophodon to a maximum known length of 1.8 metres, the largest specimen being NHM R5829 with a femur length of 202 millimetres. Typical specimens are about 1.5 metres long. Hypsilophodon would have reached up to half a metre in height. In 2010, Gregory S. Paul estimated a weight of 20 kilograms (44 lb) for an animal two metres in length.

Hypsilophodon

Like most small dinosaurs, Hypsilophodon was bipedal: it ran on two legs. Its entire body was built for running. A light-weight, minimized skeleton, low, aerodynamic posture, long legs and stiff tail, immobilised by ossified tendons, for balance: all would have allowed it to travel remarkably fast for its size. Galton in 1974 concluded it would have been among the ornithischians best adapted to running.

Heterodontosaurus

Wednesday, November 30, 2016

Heterodontosaurus restoration

Heterodontosaurus was a small, lightly-built dinosaur with three different kinds of teeth (hence its name) and a beak. The sharp, cutting front, upper teeth were used for biting against the horny beak, the cheek teeth were for grinding food, and it also had two pairs of long, canine-like teeth that fit into sockets. It had five-fingered hands with claws, and three-toed feet with claws. Its back legs were longer than its front legs. It had a long, stiff tail.

Size comparison between the ornithischian dinosaur Heterodontosaurus and a human. Silhouette by Jaime A. Headden (User:Qilong), and File:Human (1).png. Compilation by Dropzink – Own work and https://qilong.wordpress.com/2012/10/08/pegomastax-and-the-echinodonts/

Heterodontosaurus was about the size of a turkey, 50 inches long (1.3 m) and 20 inches tall (50 cm). It weighed about 42 pounds (19 kg).
Heterodontosaurus lived in the late Triassic to early Jurassic period, roughly 208 to 200 million years ago. Large predators from that time were: pterosaurs, and  crocodilians. Other dinosaurs from South Africa who lived during the lower Jurassic include: Massospondylus, Thecodontosaurus, Lanasaurus, and Lesothosaurus.

Heterodontosaurus was an herbivore (plant-eater). It had three different kinds of teeth. These teeth were specialized for biting, grinding, and tearing its food. They may have stored food in cheek pouches.
Heterodontosaurus was an ornithopod, whose intelligence (as measured by its relative brain to body weight, or EQ) was midway among the dinosaurs.

African heterodontosaurid localities: Tyinindini, Voyizane, and Tushielaw denote Heterodontosaurus finds Carol Abraczinskas, Paul C. Sereno – Sereno PC (2012) Taxonomy, morphology, masticatory function and phylogeny of heterodontosaurid dinosaurs. ZooKeys 226: 1-225. doi:10.3897/zookeys.226.2840.

Heterodontosaurus was a relatively fast, bipedal (two-legged) dinosaur. It may have run on two legs and walked on four.
A Heterodontosaurus fossil was first found in South Africa. It was named by Alan J. Charig and Alfred W. Crompton in 1962.

CLASSIFICATION
Heterodontosaurus was a very early Ornithischian dinosaur, the order of bird-hipped, herbivorous dinosaurs. It was an Ornithopod ( the bird-footed, beaked, bipedal, herbivorous dinosaurs), and belonged to the family Heterodontosauridae. The type species is H. tucki.

Herrerasaurus

Wednesday, November 30, 2016

Herrerasaurus skeleton

Herrerasaurus was one the first dinosaurs and was native to South America and was the apex predator of its homeland.

Herrerasaurus was one of the earliest dinosaurs. Its name means “Herrera’s lizard”, after the rancher who discovered the first specimen. All known fossils of this carnivore have been discovered in rocks of Carnian age (late Triassic according to the ICS, dated to 231.4 million years ago) in northwestern Argentina.

Skeletal reconstruction of Herrerasaurus

Oscar Alcober, Ricardo Martinez – Alcober OA, Martinez RN (2010) A new herrerasaurid (Dinosauria, Saurischia) from the Upper Triassic Ischigualasto Formation of northwestern Argentina. ZooKeys 63 : 55–81. doi:10.3897/zookeys.63.550

The type species, Herrerasaurus ischigualastensis, was described by Osvaldo Reig in 1963 and is the only species assigned to the genus. Ischisaurus and Frenguellisaurus are synonyms.

For many years, the classification of Herrerasaurus was unclear because it was known from very fragmentary remains. It was hypothesized to be a basal theropod, a basal sauropodomorph, a basal saurischian, or not a dinosaur at all but another type of archosaur. However, with the discovery of an almost complete skeleton and skull in 1988, Herrerasaurus has been classified as either an early theropod or an early saurischian in at least five recent reviews of theropod evolution, with many researchers treating it at least tentatively as the most primitive member of Theropoda.

Herrerasaurus ischigualastensis by Sergey Krasovskiy

It is a member of the Herrerasauridae, a family of similar genera that were among the earliest of the dinosaurian evolutionary radiation. Herrerasaurids may be predatory, but are sometimes considered too primitive to be actual theropods.

Giganotosaurus

Wednesday, November 30, 2016

The night is dark, and full of terrors Art by Giganotosaur (Martin Colombo)

Giganotosaurus is a genus of theropod dinosaur that lived in what is now Argentina, during the early Cenomanian age of the Late Cretaceous period, approximately 99.6 to 97 million years ago. The holotype specimen was discovered in the Candeleros Formation of Patagonia in 1993, and is almost 70% complete. The animal was named G. carolinii in 1995; the genus name translates as “giant southern lizard” and the specific name honours the discoverer, Rubén D. Carolini. A dentary bone, a tooth and some tracks, discovered before the holotype, were later assigned to this animal. The genus attracted much interest and became part of a scientific debate about the maximum sizes of theropod dinosaurs.

Giganotosaurus carolinii vs Tyrannosaurus sizes by Scott Hartman

Giganotosaurus was one of the largest known terrestrial carnivores, but the exact size has been hard to determine due to the incompleteness of the remains found so far. Estimates for the most complete specimen range from a length of 12 to 13 m (39 to 43 ft), a skull 1.53 to 1.80 m (5.0 to 5.9 ft) in length, and a weight of 4.2 to 13.8 t (4.6 to 15.2 short tons). The dentary bone that belonged to a supposedly larger individual has been used to extrapolate a length of 13.2 m (43 ft). Some researchers have found the animal to be larger than Tyrannosaurus, which has historically been considered the largest theropod, while others have found them to be equal in size, and the largest size estimates for Giganotosaurus exaggerated. The skull was low, with rugose (rough and wrinkled) nasal bones and a ridge-like crest on the lacrimal bone in front of the eye. The front of the lower jaw was flattened, and had a downwards projecting process (or “chin”) at the tip. The teeth were compressed sideways and had serrations. The neck was strong and the pectoral girdle proportionally small.

Reconstructed skeleton, Australian Museum, Sydney.

Part of the family CarcharodontosauridaeGiganotosaurus is one of the most completely known members of the group, which includes other very large theropods, such as the closely related Mapusaurus and CarcharodontosaurusGiganotosaurusis thought to have been homeothermic (a type of “warm-bloodedness”), with a metabolism between that of a mammal and a reptile, which would have enabled fast growth. It may have been relatively slow-moving, with a suggested running speed of 14 metres per second (50 km/h; 31 mph). It would have been capable of closing its jaws quickly, capturing and bringing down prey by delivering powerful bites. The “chin” may have helped in resisting stress when a bite was delivered against prey. Giganotosaurus is thought to have been the apex predator of its ecosystem, and it may have fed on juvenile sauropod dinosaurs.

Holotype skeleton with reconstructed skull, arm, and feet, on the floor in EBPM

Classification

Coria and Salgado originally found Giganotosaurus to group more closely with the theropod clade tetanurae than to more basal (or “primitive”) theropods such as ceratosaurs, due to shared features (synapomorphies) in the legs, skull, and pelvis. Other features showed that it was outside the more derived (or “advanced”) clade coelurosauria. In 1996, Sereno and colleagues found GiganotosaurusCarcharodontosaurus, and Acrocanthosaurus to be closely related within the superfamily Allosauroidea, and grouped them in the family Carcharodontosauridae. Features shared between these genera include the lacrimal and postorbital bones forming a broad “shelf” over the orbit, and the squared front end of the lower jaw.

Source: www.wikipedia.org / www.natgeo.com

Gallimimus

Wednesday, November 30, 2016

Gallimimus bullatus by Kana-hebi on DeviantArt

Gallimimus (meaning “chicken mimic”) is a genus of ornithomimid theropod dinosaurs from the late Cretaceous period (Maastrichtian stage) Nemegt Formation of Mongolia. With individuals as long as 8 m (26 ft), it was one of the largest ornithomimosaurs. Gallimimus is known from multiple individuals, ranging from juvenile (about 0.5 m tall at the hip) to adult (about 2 m tall at the hip). The type species is G.bullatus, which means “capsuled chicken mimic”.
 
Reconstructed skeleton (based on the adult holotype and a juvenile specimen), Natural History Museum, London

The first fossil remains of this dinosaur were discovered in early August 1963 by a team of Professor Zofia Kielan-Jaworowska at Tsagan Khushu during a Polish-Mongolian expedition to the Gobi Desert of Mongolia. The find was reported by her in 1965. In 1972, it was named and described by paleontologists Rinchen Barsbold, Halszka Osmólska, and Ewa Roniewicz. The only named species is the type species Gallimimus bullatus. The generic name is derived from Latin gallus, “chicken”, and mimus, “mimic”, in reference to the neural arches of the front neck vertebrae which resemble those of the Galliformes. The specific name is derived from Latin bulla, a magic capsule worn by Roman youth around the neck, in reference to a bulbous swelling in the braincase on the underside of the parasphenoid, in the form of a capsule. The holotype specimen, IGM 100/11, consists of a partial skeleton including the skull and lower jaws. It is a larger skeleton; several other partial skeletons have been described, most of them of juveniles, and numerous single bones.

Human-gallimimus size comparison

A second species announced by Barsbold in 1996, “Gallimimus mongoliensis” based on specimen IGM 100/14 from the older Bayanshiree Formation, has never been formally referred to this genus. In a reanalysis of the nearly complete skeleton of “Gallimimus mongoliensis” Barsbold concluded in 2006 that it is not a species of Gallimimus but may represent a new, currently unnamed ornithomimid genus.

Gallimimus was assigned to the Ornithomimidae in 1972. This is confirmed by recent cladistic analyses.

Fabrosaurus

Wednesday, November 30, 2016

Fabrosaurus

Fabrosaurus (meaning “Fabre’s lizard” in honor of Jean Fabre, a French geologist and a colleague of Ginsburg on the expedition that collected the fossil in Basutoland, Southern Africa; Greek sauros “lizard”)) was a genus of herbivorous dinosaur which lived during the Early Jurassic (Hettangian to Sinemurian stages 199 – 189 mya).

Fabrosaurus was named by paleontologist Leonard Ginsburg in 1964 based on partial jawbone with three teeth. The type species, F. australis, was named for the location of the fossils in Lesotho, Southern Africa (australis being Latin for “southern”).

Fabrosaurus size

Subsequent discoveries included two crushed skulls and disarticulated post-cranial bones (including vertebrae, ribs, and limb bones), allowing for a more complete reconstruction. However, as additional ornithischian fossils were discovered, the features of F. australis were thought to be shared by other species, and by the 1990s and 2000s most authors working with the group found Fabrosaurus to be a nomen dubium (doubtful name), finding the holotype material described by Ginsburg to be insufficient to distinguish a new taxon. Some claim the fossils represent simple variation of Lesothosaurus, which is regarded as valid.

Ceratopsia Facts

Wednesday, November 30, 2016

Ceratopsia by Mad-Hatter-LCarol on DeviantArt

Ceratopsians are also known as ceratopians, and it means ‘horned eye’. They are very interesting dinosaurs and a lot different than the sauropods and theropods. To identify a ceratopian is not difficult because they had horns, bony frills and curved bony beaks. Ceratopians lived mainly in the Cretaceous period.

One of the most popular type of ceratopian was the Triceratops. The reason why they are called ‘horned eye’ is because they had remarkable horns above their eyes. Triceratops was the largest of this group of family and its brow horns were nearly up to a meter long.

Triceratops, one of the largest ceratopsians (a chasmosaurinae ceratopsid). It had solid frill and long horns.

Most of the ceratopians had an enormous neck frill. The frill was made of solid bone, and covered with their skin. This frill protected the ceratopians neck from being bitten or clawed by the predators. In some dinosaurs like the big Torosaurus, the bony frill grew halfway down the creature’s back. One particular dinosaur, the Psittacosaurus (parrot-lizard), did not have an obvious neck frill, but it did have another feature of the ceratopian group, which was a parrot-like beak. Experts believe this dinosaur should belong to the ceratopians, despite not having a transparent neck frill.

All ceratopians ate were herbivores and ate plants and their parrot-like beaks helped them to chop off tough plant stems. The horned eye dinosaurs included many different types of dinosaur. The group lived mainly towards the end of the Cretaceous period. Like the ornithopods, the ceratopians evolved during their time on Earth. Some of the first ceratopians, like the Protoceratops, did not have have horns, instead they had a thick, bony areas over their snouts and eyes. But eventually in time, the ceratopians developed horns. Pentaceratops was the later dinosaur to appear than Protoceratops. Pentaceratops had the most horns of all the horned dinosaurs, and its name means ‘five horned face’.

Like the rhinoceroses of today, the ceratopians walked on all four legs. The Styracosaurus had strong, muscular legs to support its massive heavy head. Its feet ended in toes which were spread out to help carry the weight of its enormous body. Another dinosaur as mentioned earlier, the Psittacosaurus, usually walked on two legs most of the time, but it may have walked on four legs in certain occasions. The ceratopians lived in North America, Europe and Asia, which are believed to be the only places where their skeleton fossils have been found so far.

Another fact about ceratopians is that some of them had holes in their frills.The neck frills were large and heavy, and to make them lighter, some of them had large holes in them to reduce the weight. Also the skin covering the bony frill stretched over the holes to make them invisible.

Ceratopsian fossil discoveries. The presence of Jurassic ceratopsians only in Asia indicates an Asian origin for the group, while the more derived ceratopsids occur only in North America save for one Asian species. Questionable remains are indicated with question marks. By Sheep81

Source: www.natgeo.com / www.wikipedia.org

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