Dinosaurs – Species Encycolpedia


Saturday, November 26, 2016

Deinonychus antirrhopus by Carlo-Arellano

Deinonychus  is a genus of carnivorous dromaeosaurid coelurosaurian dinosaurs, with one described species, Deinonychus antirrhopus. This species, which could grow up to 3.4 metres (11 ft) long, lived during the early Cretaceous Period, about 115–108 million years ago (from the mid-Aptian to early Albian stages). Fossils have been recovered from the U.S. states of Montana, Utah, Wyoming, and Oklahoma, in rocks of the Cloverly Formation, Cedar Mountain Formation and Antlers Formation, though teeth that may belong to Deinonychus have been found much farther east in Maryland.

Size compared with a human

Paleontologist John Ostrom’s study of Deinonychus in the late 1960s revolutionized the way scientists thought about dinosaurs, leading to the “dinosaur renaissance” and igniting the debate on whether dinosaurs were warm-blooded or cold blooded. Before this, the popular conception of dinosaurs had been one of plodding, reptilian giants. Ostrom noted the small body, sleek, horizontal posture, ratite-like spine, and especially the enlarged raptorial claws on the feet, which suggested an active, agile predator.

“Terrible claw” refers to the unusually large, sickle-shaped talon on the second toe of each hind foot. The fossil YPM 5205 preserves a large, strongly curved ungual. In life, archosaurs have a horny sheath over this bone, which extends the length. Ostrom looked at crocodile and bird claws and reconstructed the claw for YPM 5205 as over 120 millimetres (4.7 in) long. The species name antirrhopus means “counter balance”, which refers to Ostrom’s idea about the function of the tail. As in other dromaeosaurids, the tail vertebrae have a series of ossified tendons and super-elongated bone processes. These features seemed to make the tail into a stiff counterbalance, but a fossil of the very closely related Velociraptor mongoliensis (IGM100/986) has an articulated tail skeleton that is curved laterally in a long S-shape. This suggests that, in life, the tail could bend to the sides with a high degree of flexibility. In both the Cloverly and Antlers formations, Deinonychus remains have been found closely associated with those of the ornithopod Tenontosaurus. Teeth discovered associated with Tenontosaurusspecimens imply they were hunted, or at least scavenged upon, by Deinonychus.

Skeleton of the dromaeosaurid dinosaur Deinonychus at Field Museum of Natural History. At the bottom is the skeleton of Buitreraptor.

Fossilized remains of Deinonychus have been recovered from the Cloverly Formation of Montana and Wyoming and in the roughly contemporary Antlers Formation of Oklahoma, in North America. The Cloverly formation has been dated to the late Aptian through early Albian stages of the early Cretaceous, about 115 to 108 Ma. Additionally, teeth found in the Arundel Clay Facies (mid-Aptian), of the Potomac Formation on the Atlantic Coastal Plain of Maryland may be assigned to the genus.

The first remains were uncovered in 1931 in southern Montana near the town of Billings. The team leader, paleontologist Barnum Brown, was primarily concerned with excavating and preparing the remains of the ornithopod dinosaur Tenontosaurus, but in his field report from the dig site to the American Museum of Natural History, he reported the discovery of a small carnivorous dinosaur close to a Tenontosaurus skeleton, “but encased in lime difficult to prepare.” He informally called the animal “Daptosaurus agilis” and made preparations for describing it and having the skeleton, specimen AMNH 3015, put on display, but never finished this work. Brown brought back from the Cloverly Formation the skeleton of a smaller theropod with seemingly oversized teeth that he informally named “Megadontosaurus”. John Ostrom, reviewing this material decades later, realized that the teeth came from Deinonychus, but the skeleton came from a completely different animal. He named this skeleton Microvenator.


Saturday, November 26, 2016

Corythosaurus in color by Ahrkeath on DeviantArt

Corythosaurus is a genus of hadrosaurid “duck-billed” dinosaur from the Upper Cretaceous Period, about 77–75.7 million years ago. It lived in what is now North America. Its name means “helmet lizard”, derived from Greek κόρυς. It was named and described in 1914 by Barnum Brown. Corythosaurus is now thought to be a lambeosaurine, related to NipponosaurusVelafronsHypacrosaurus, and OlorotitanCorythosaurus has an estimated length of 9 metres (30 ft), and has a skull, including the crest, that is 70.8 centimetres (27.9 in) tall.

Corythosaurus is known from many complete specimens, including the nearly complete holotype found by Brown in 1911. The holotype skeleton is only missing the last section of the tail, and part of the forelimbs, but was preserved with impressions of polygonal scales. Corythosaurus is known from many skulls with tall crests. The crests resemble the crests of the cassowary and a Corinthian helmet. The most likely function of the crest is thought to be vocalization. As in a trombone, sound waves would travel through many chambers in the crest, and then get amplified when Corythosaurus exhaled. A Corythosaurus specimen has been preserved with its last meal in its chest cavity. Inside the cavity were remains of conifer needles, seeds, twigs, and fruits: Corythosaurus probably fed on all of these.

The two species of Corythosaurus are both present in slightly different levels of the Dinosaur Park Formation. Both still co-existed with theropods and other ornithischians, like DaspletosaurusBrachylophosaurusParasaurolophusScolosaurus, and Chasmosaurus.

Excavation of the holotype specimen of Corythosaurus casuarius by the Red Deer River.

Benson et al. (2012) estimated that Corythosaurus has an average length of 9 metres (30 ft). Richard Swann Lull’s earlier length estimate, published in 1942, found a slightly longer total length of 9.4 m (31 ft), a size similar to Lambeosaurus lambei, another Canadian lambeosaurine. In 1962, Edwin H. Colbert used models of specific dinosaurs, including Corythosaurus, to estimate their weight. The Corythosaurus model used, was modelled by Vincent Fusco after a mounted skeleton, and supervised by Barnum Brown. After testing, it was concluded that the average weight of Corythosaurus was 3.82 tonnes (3.76 long tons; 4.21 short tons). More recent size estimates of Corythosaurus, published in 2001, find the genus to be among the largest hadrosaurids, only smaller than Shantungosaurus and Parasaurolophus. The total length of Corythosaurusspecimen AMNH 5240 was found to be 8.1 m (27 ft), with a weight of 3.0785 tonnes (3.0299 long tons; 3.3935 short tons).

Size of the two species compared to a human.

Proportionally, the skull is much shorter and smaller than that of Edmontosaurus (formerly Trachodon), Kritosaurus, or Saurolophus, but when including its crest, its superficial area is almost as large.


Saturday, November 26, 2016

Compsognathus longipes, a coelurosaur from the Late Jurassic of Europe, pencil drawing by Nobu Tamura

Compsognathus is a genus of small, bipedal, carnivorous theropod dinosaurs. Members of its single species Compsognathus longipes could grow to the size of a turkey. They lived about 150 million years ago, the Tithonian age of the late Jurassic period, in what is now Europe. Paleontologists have found two well-preserved fossils, one in Germany in the 1850s and the second in France more than a century later. Today, C. longipes is the only recognized species, although the larger specimen discovered in France in the 1970s was once thought to belong to a separate species and named C. corallestris.

Size comparison of the French (orange) and German (green) specimens, with a human

Many presentations still describe Compsognathus as “chicken-sized” dinosaurs because of the small size of the German specimen, which is now believed to be a juvenile. Compsognathus longipes is one of the few dinosaur species for which diet is known with certainty: the remains of small, agile lizards are preserved in the bellies of both specimens. Teeth discovered in Portugal may be further fossil remains of the genus.

Although not recognized as such at the time of its discovery, Compsognathus is the first theropod dinosaur known from a reasonably complete fossil skeleton. Until the 1990s, it was the smallest known non-avialan dinosaur; earlier it had been incorrectly thought to be the closest relative of Archaeopteryx.

Compsognathus also holds the distinction of being the first dinosaur genus to be portrayed with feathers, by Thomas Henry Huxley in 1876.

Reconstruction of a skeleton, Museum of Ancient Life – Thanksgiving Point

The genus Compsognathus gives its name to the family Compsognathidae, a group composed mostly of small dinosaurs from the late Jurassic and early Cretaceous periods of China, Europe and South America. For many years it was the only member known; however in recent decades paleontologists have discovered several related genera. The clade includes AristosuchusHuaxiagnathusMirischiaSinosauropteryx, and perhaps Juravenator and Scipionyx. At one time, Mononykus was proposed as a member of the family, but this was rejected by Chen and coauthors in a 1998 paper; they considered the similarities between Mononykus and the compsognathids to be an example of convergent evolution. The position of Compsognathus and its relatives within the coelurosaur group is uncertain. Some, such as theropod expert Thomas Holtz Jr. and co-authors Ralph Molnar and Phil Currie in the landmark 2004 text Dinosauria, hold the family as the most basal of the coelurosaurs, while others as part of the Maniraptora.


Saturday, November 26, 2016

Coelophysis by Typothorax on DeviantArt

Coelophysis is an genus of coelophysid theropod dinosaur that lived approximately 203 to 196 million years ago during the latter part of the Triassic Period in what is now the southwestern United States. It was a small, slenderly-built, ground-dwelling, bipedal carnivore, that could grow up to 3 m (9.8 ft) long. Coelophysis is one of the earliest known dinosaur genera. Scattered material representing similar animals has been found worldwide in some Late Triassic and Early Jurassic formations. The type species C. bauri, originally given to the genus Coelurus by Edward Drinker Cope in 1887, was described by the latter in 1889. The names Longosaurus and Rioarribasaurus are synonymous with Coelophysis. Another dinosaur genus, Megapnosaurus, has also been considered to be a synonym. This primitive theropod is notable for being one of the most specimen-rich dinosaur genera.

Size of C. bauri compared to a human

Coelophysis is known from a number of complete fossil skeletons of the species C. bauri, which was a lightly built dinosaur which measured up to 3 metres (9.8 ft) in length and which was more than a meter tall at the hips. Paul (1988) estimated the weight of the gracile form at 15 kg (33 lb), and the weight of the robust form at 20 kg (44 lb). Coelophysis was a bipedal, carnivorous, theropod dinosaur that was a fast and agile runner. Despite being an early dinosaur, the evolution of the theropod body form had already advanced greatly from creatures like Herrerasaurus and Eoraptor. The torso of Coelophysisconforms to the basic theropod body shape, but the pectoral girdle displays some interesting special characteristics: C. baurihad a furcula (wishbone), the earliest known example in a dinosaur. Coelophysis also preserves the ancestral condition of possessing four digits on the hand (manus). It had only three functional digits, the fourth embedded in the flesh of the hand.

Coelophysis is a distinct taxonomic unit (genus), composed of two species; C. bauri and C. rhodesiensis (the latter formerly classified as the genus Megapnosaurus). Two additional originally described species, C. longicollis and C. willistoni, are now considered synonymous with C. bauriC. rhodesiensis is probably part of this generic complex, and is known from the Jurassic of southern Africa. A third possible species is Coelophysis kayentakatae, previously referred to the genus Megapnosaurus. There is not a clear consensus at this point.


Saturday, November 19, 2016

Albertosaurus life restoration

Albertosaurus (meaning “Alberta lizard”) is a genus of tyrannosaurid theropod dinosaurs that lived in western North America during the Late Cretaceous Period, about 70 million years ago. The type species, A. sarcophagus, was apparently restricted in range to the modern-day Canadian province of Alberta, after which the genus is named. Scientists disagree on the content of the genus, with some recognizing Gorgosaurus libratus as a second species.

As a tyrannosaurid, Albertosaurus was a bipedal predator with tiny, two-fingered hands and a massive head that had dozens of large, sharp teeth. It may have been at the top of the food chain in its local ecosystem. While Albertosaurus was very large for a theropod, it was much smaller than its larger and more famous relative Tyrannosaurus, growing to nine to ten metres long and weighing less than possibly 2 metric tons.

Since the first discovery in 1884, fossils of more than 30 individuals have been recovered, providing scientists with a more detailed knowledge of Albertosaurus anatomy than is available for most other tyrannosaurids. The discovery of 26 individuals at one site provides evidence of pack behaviour and allows studies of ontogeny and population biology, which are impossible with lesser-known dinosaurs.

Albertosaurus sarcophagus Osborn, 1905 theropod dinosaur from the Upper Cretaceous of Alberta, western Canada (public display, Dakota Dinosaur Museum, Dickinson, North Dakota, USA). Classification: Animalia, Chordata, Vertebrata, Dinosauria, Theropoda, Tyrannosauridae Theropod were small to large, bipedal dinosaurs. Almost all known members of the group were carnivorous (predators and/or scavengers). They represent the ancestral group to the birds, and some theropods are known to have had feathers. Some of the most well known dinosaurs to the general public are theropods, such as Tyrannosaurus, Allosaurus, and Spinosaurus.

Albertosaurus is the best known of all tyrannosaurids. Recent discoveries include wishbones-a feature it shared with other advanced theropods as well as with birds. Many museum specimens of Tyrannosaurus have filled in gaps in our knowledge of the larger dinosaur with information taken from Albertosaurus.


Saturday, November 19, 2016

Cryolophosaurus by PaleoGuy on DeviantArt

Cryolophosaurus is a genus of large theropods known from only a single species Cryolophosaurus ellioti, known from the early Jurassic period of Antarctica. It was about 6.5 metres (21.3 ft) long and 465 kilograms (1,025 lb) in weight, making it one of the largest theropods of its time.

Individuals of this species may have grown even larger, because the only known specimen probably represents a sub-adult. Cryolophosaurus is known from a skull, a femur and other material, the skull and femur of which have caused its classification to vary greatly. The femur possesses many primitive characteristics that have classified Cryolophosaurus as a dilophosaurid or a neotheropod outside of Dilophosauridae and Averostra, where as the skull has many advanced features, leading the genus to be considered a tetanuran, an abelisaurid, a ceratosaur and even an allosaurid. Since its original description, the consensus is that Cryolophosaurus is either a primitive member of the Tetanurae or a close relative of that group.

Cryolophosaurus possessed a distinctive crest on its head that spanned the head from side to side, similar to a Spanish comb. Based on evidence from related species and studies of bone texture, it is thought that this bizarre crest was used for intra-species recognition. The brain of Cryolophosaurus was also more primitive than those of other theropods.

Reconstructed holotype skeleton

Cryolophosaurus was first excavated from Antarctica’s Early Jurassic, Sinemurian to Pliensbachian aged Hanson Formation, formerly the upper Falla Formation, by paleontologist Dr. William Hammer in 1991. It was the first carnivorous dinosaur to be discovered in Antarctica and the first non-avian dinosaur from the continent to be officially named. The sediments in which its fossils were found have been dated at ~194 to 188 million years ago, representing the Early Jurassic Period.

All known specimens of Cryolophosaurus have been recovered in the Hanson Formation, which is one of only two major dinosaur-bearing rock formations found on the continent of Antarctica. It was discovered in “tuffaceous” siltstone deposited in the Sinemurian to Pliensbachian stage of the Early Jurassic, approximately 194 to 188 million years ago. This geological formation is part of the Victoria Group of the Transantarctic Mountains, which is approximately 4,000 metres (13,000 ft) above sea level. The high altitude of this site supports the idea that early Jurassic Antarctica had forests populated by a diverse range of species, at least along the coast. The Hanson Formation was deposited in an active volcano−tectonic rift system formed during the breakup of Gondwana.


Saturday, November 19, 2016

Allosauruses by deskridge on DeviantArt

Allosaurus is a genus of large theropod dinosaur that lived 155 to 150 million years ago during the late Jurassic period (Kimmeridgian to early Tithonian). The name “Allosaurus” means “different lizard”. It is derived from the Greek ἄλλος/allos(“different, other”) and σαῦρος/sauros (“lizard / generic reptile”). The first fossil remains that could definitively be ascribed to this genus were described in 1877 by paleontologist Othniel Charles Marsh. These remains became known as Antrodemus. As one of the first well-known theropod dinosaurs, it has long attracted attention outside of paleontological circles. Indeed, it has been a top feature in several films and documentaries about prehistoric life.

Allosaurus was a large bipedal predator. Its skull was large and equipped with dozens of sharp, serrated teeth. It averaged 8.5 m (28 ft) in length, though fragmentary remains suggest it could have reached over 12 m (39 ft). Relative to the large and powerful hindlimbs, its three-fingered forelimbs were small, and the body was balanced by a long and heavily muscled tail. It is classified as an allosaurid, a type of carnosaurian theropod dinosaur. The genus has a complicated taxonomy, and includes an uncertain number of valid species, the best known of which is A. fragilis. The bulk of Allosaurus remains have come from North America’s Morrison Formation, with material also known from Portugal and possibly Tanzania. It was known for over half of the 20th century as Antrodemus, but study of the copious remains from the Cleveland-Lloyd Dinosaur Quarry brought the name “Allosaurus” back to prominence, and established it as one of the best-known dinosaurs.

Allosaurus vs Trex size comparison

As the most abundant large predator in the Morrison Formation, Allosaurus was at the top of the food chain, probably preying on contemporaneous large herbivorous dinosaurs, and perhaps even other predators. Potential prey included ornithopods, stegosaurids, and sauropods. Some paleontologists interpret Allosaurus as having had cooperative social behavior, and hunting in packs, while others believe individuals may have been aggressive toward each other, and that congregations of this genus are the result of lone individuals feeding on the same carcasses. It may have attacked large prey by ambush, using its upper jaw like a hatchet.


Allosaurus was a typical large theropod, having a massive skull on a short neck, a long tail and reduced forelimbs. Allosaurus fragilis, the best-known species, had an average length of 8.5 m (28 ft), with the largest definitive Allosaurus specimen (AMNH 680) estimated at 9.7 meters (32 feet) long, and an estimated weight of 2.3 metric tons (2.5 short tons). In his 1976 monograph on Allosaurus, James Madsen mentioned a range of bone sizes which he interpreted to show a maximum length of 12 to 13 m (39 to 43 ft). As with dinosaurs in general, weight estimates are debatable, and since 1980 have ranged between 1,500 kilograms (3,300 pounds), 1,000 to 4,000 kg (2,200 to 8,800 lb), and 1,010 kilograms (2,230 pounds) for modal adult weight (not maximum). John Foster, a specialist on the Morrison Formation, suggests that 1,000 kg (2,200 lb) is reasonable for large adults of A. fragilis, but that 700 kg (1,500 lb) is a closer estimate for individuals represented by the average-sized thigh bones he has measured. Using the subadult specimen nicknamed “Big Al”, researchers using computer modelling arrived at a best estimate of 1,500 kilograms (3,300 lb) for the individual, but by varying parameters they found a range from approximately 1,400 kilograms (3,100 lb) to approximately 2,000 kilograms (4,400 lb).

Mounted skeleton of “Big Al II” (specimen SMA 0005). Author: “The_Wookies”

Several gigantic specimens have been attributed to Allosaurus, but may in fact belong to other genera. The closely related genus Saurophaganax (OMNH 1708) reached perhaps 10.9 m (36 ft) in length, and its single species has sometimes been included in the genus Allosaurus as Allosaurus maximus, though recent studies support it as a separate genus. Another potential specimen of Allosaurus, once assigned to the genus Epanterias (AMNH 5767), may have measured 12.1 meters (40 feet) in length. A more recent discovery is a partial skeleton from the Peterson Quarry in Morrison rocks of New Mexico; this large allosaurid may be another individual of Saurophaganax.


The skull and teeth of Allosaurus were modestly proportioned for a theropod of its size. Paleontologist Gregory S. Paul gives a length of 845 mm (33.3 in) for a skull belonging to an individual he estimates at 7.9 m (26 ft) long. Each premaxilla (the bones that formed the tip of the snout), held five teeth with D-shaped cross-sections, and each maxilla (the main tooth-bearing bones in the upper jaw) had between 14 and 17 teeth; the number of teeth does not exactly correspond to the size of the bone. Each dentary (the tooth-bearing bone of the lower jaw) had between 14 and 17 teeth, with an average count of 16. The teeth became shorter, narrower, and more curved toward the back of the skull. All of the teeth had saw-like edges. They were shed easily, and were replaced continually, making them common fossils.

Allosaurus skull

The skull had a pair of horns above and in front of the eyes. These horns were composed of extensions of the lacrimal bones, and varied in shape and size. There were also lower paired ridges running along the top edges of the nasal bones that led into the horns. The horns were probably covered in a keratin sheath and may have had a variety of functions, including acting as sunshades for the eye, being used for display, and being used in combat against other members of the same species (although they were fragile). There was a ridge along the back of the skull roof for muscle attachment, as is also seen in tyrannosaurids.

Inside the lacrimal bones were depressions that may have held glands, such as salt glands. Within the maxillae were sinuses that were better developed than those of more basal theropods such as Ceratosaurus and Marshosaurus; they may have been related to the sense of smell, perhaps holding something like Jacobson’s organ. The roof of the braincase was thin, perhaps to improve thermoregulation for the brain. The skull and lower jaws had joints that permitted motion within these units. In the lower jaws, the bones of the front and back halves loosely articulated, permitting the jaws to bow outward and increasing the animal’s gape. The braincase and frontals may also have had a joint.


Allosaurus was an allosaurid, a member of a family of large theropods within the larger group Carnosauria. The family name Allosauridae was created for this genus in 1878 by Othniel Charles Marsh, but the term was largely unused until the 1970s in favor of Megalosauridae, another family of large theropods that eventually became a wastebasket taxon. This, along with the use of Antrodemus for Allosaurus during the same period, is a point that needs to be remembered when searching for information on Allosaurus in publications that predate James Madsen’s 1976 monograph. Major publications using the name “Megalosauridae” instead of “Allosauridae” include Gilmore, 1920, von Huene, 1926, Romer, 1956 and 1966, Steel, 1970, and Walker, 1964.

Following the publication of Madsen’s influential monograph, Allosauridae became the preferred family assignment, but it too was not strongly defined. Semi-technical works used Allosauridae for a variety of large theropods, usually those that were larger and better-known than megalosaurids. Typical theropods that were thought to be related to Allosaurus included IndosaurusPiatnitzkysaurusPiveteausaurusYangchuanosaurusAcrocanthosaurusChilantaisaurusCompsosuchusStokesosaurus, and Szechuanosaurus. Given modern knowledge of theropod diversity and the advent of cladistic study of evolutionary relationships, none of these theropods is now recognized as an allosaurid, although several, like Acrocanthosaurus and Yangchuanosaurus, are members of closely related families.

The cladogram of the classification of Allosauroidea by Drew R. Eddy, Julia A. Clarke

Allosauridae is one of four families in Carnosauria; the other three are Neovenatoridae, Carcharodontosauridae and Sinraptoridae. Allosauridae has at times been proposed as ancestral to the Tyrannosauridae (which would make it paraphyletic), one recent example being Gregory S. Paul’s Predatory Dinosaurs of the World, but this has been rejected, with tyrannosaurids identified as members of a separate branch of theropods, the Coelurosauria. Allosauridae is the smallest of the carnosaur families, with only Saurophaganax and a currently unnamed French allosauroid accepted as possible valid genera besides Allosaurus in the most recent review. Another genus, Epanterias, is a potential valid member, but it and Saurophaganax may turn out to be large examples of Allosaurus. Recent reviews have kept the genus Saurophaganax and included Epanterias with Allosaurus.

Species and taxonomy

There are currently four valid and one undescribed species of Allosaurus (A. amplusA. europaeus, the type species A. fragilis, the as-yet not formally described “A. jimmadseni”, and A. lucasi).

A. fragilis, “A. jimmadseni”, A. amplus, and A. lucasi are all known from remains discovered in the Kimmeridgian–Tithonian Upper Jurassic-age Morrison Formation of the United States, spread across the states of Colorado, Montana, New Mexico, Oklahoma, South Dakota, Utah, and Wyoming. A. fragilis is regarded as the most common, known from the remains of at least sixty individuals. For a while in the late 1980s and early 1990s it was common to recognize A. fragilis as the short-snouted species, with the long-snouted taxon being A. atrox; however, subsequent analysis of specimens from the Cleveland-Lloyd Quarry, Como Bluff, and Dry Mesa Quarry showed that the differences seen in the Morrison Formation material could be attributed to individual variation. A study of skull elements from the Cleveland-Lloyd site found wide variation between individuals, calling into question previous species-level distinctions based on such features as the shape of the lacrimal horns, and the proposed differentiation of “A. jimmadseni” based on the shape of the jugal. A. europaeus was found in the Kimmeridgian-age Porto Novo Member of the Lourinhã Formation, but may be the same as A. fragilis.

Allosaurus tendagurensis was found in Kimmeridgian-age rocks of Tendaguru, in Mtwara, Tanzania. Subsequent studies classified it as a non-coelurosaurian tetanuran, either a megalosaurid or carcharodontosaur. Although obscure, it was a large theropod, possibly around 10 meters (33 feet) long and 2.5 metric tons (2.8 short tons) in weight.


Saturday, November 19, 2016


Anchisaurus is a genus of basal sauropodomorph. An early herbivorous dinosaur, it lived during the Early Jurassic period; more specifically, the Pliensbachian to Toarcian ages, 190 to 174 million years ago. Until recently it was classed as a member of Prosauropoda. The name comes from the Greek αγχι/agkhi anchi-; “near, close” + Greek σαυρος/sauros; “lizard”. Anchisaurus was coined as a replacement name for Amphisaurus, which was itself a replacement name for Hitchcock’s Megadactylus, both of which had already been used for other animals.

Anchisaurus was a rather small dinosaur, with a length of just over 2 metres (6.6 ft), which helps explain why it was once mistaken for human bones. It probably weighed around 27 kilograms (60 lb). However, Marsh’s species A. major (also known as Ammosaurus) was larger, from 2.5 to 4 metres (8 ft 2 in to 13 ft 1 in) and some estimates give it a weight of up to 70 pounds (32 kg). Gregory S. Paul estimated its length at 2.2 meters and its weight at 20 kg in 2010.

Anchisaurus size

Sauropodomorph remains were first discovered in North America in 1818, when some large bones were uncovered by Mr. Solomon Ellsworth Jr while with gunpowder excavating a well in East Windsor, Connecticut. At the time of their discovery it was thought that the bones might be those of a human, but the presence of tail vertebrae in 1821 falsified that idea. They are now recognized as those of an indeterminate sauropodomorph, possibly more closely related to the plateosaurian prosauropods.

Due to its primitive appearance, Anchisaurus was previously classified as a prosauropod, a member of a group of animals related to or ancestral to the sauropods. Recent investigations show that a group of traditional prosauropods form a monophyletic sister-group to Sauropoda, and that Anchisaurus is instead closer to sauropods.

The family Anchisauridae was first proposed by Othniel Charles Marsh in 1885 and later defined as a clade consisting of Anchisaurus and its nearest relatives. However, it is not clear which other genera are included in the family; many of the dinosaurs once included have since been moved elsewhere, and the group is not used in most current taxonomies.


Saturday, November 19, 2016


Atlascopcosaurus (meaning “Atlas Copco lizard”) is a genus of herbivorous basal euornithopod dinosaur from the Early Cretaceous of the present Australia.

The type specimen, NMV P166409, was found in 1984 at the Dinosaur Cove East site at the coast of Victoria, in layers of the Eumeralla Formation dating from the early Cretaceous, Aptian-Albian. This holotype consists of a piece of the upper jaw, a partial maxilla with teeth. Nothing else is known about it; as the rest of the skeleton remains undiscovered it can only be inferred from closely related species that the genus represents a small bipedal herbivore. By extrapolation it has been estimated that it was about two to three metres (6.5–10 ft) long and weighed appoximately 125 kg. Because the teeth are not species-specific and the maxilla fragment is little informative, the taxon is today commonly seen as a nomen dubium.


The type species, Atlascopcosaurus loadsi, was named and described by Tom Rich and Patricia Vickers-Rich in 1988/1989. The generic name refers to the Atlas Copco Company who had provided equipment for the dig that discovered this dinosaur in 1984. The project revealed 85 fossil bone fragments of various species. This opened the door for more excavation and, along with other companies, Atlas Copco helped over ten years excavate about sixty metres of tunnel in a cliff wall at the sea shore. The specific name, loadsi, honours William Loads, the state manager for Atlas Copco at the time, who assisted during the dig.

Atlascopcosaurus was in 1988 assigned to the Hypsilophodontidae. These are today seen as an unnatural (paraphyletic) group and Atlascopcosaurus is now simply considered a basal member of the Ornithopoda.


Saturday, November 19, 2016

Ankylosaurus by WillDynamo55 on DeviantArt

Ankylosaurus is a genus of armored dinosaur. Fossils of Ankylosaurus have been found in geological formations dating to the very end of the Cretaceous Period, between about 68–66 million years ago, in western North America, making it among the last of the non-avian dinosaurs. It was named by Barnum Brown in 1908, and the only species classified in the genus is A. magniventris. The genus name means “fused lizard” and the specific name means “great belly”. A handful of specimens have been excavated to date, but a complete skeleton has not been discovered. Though other members of Ankylosauria are represented by more extensive fossil material, Ankylosaurus is often considered the archetypal member of its group.

Size of the largest known specimen (green), compared to a human

The largest known ankylosaurid, Ankylosaurus measured up to 6.25 m (20.5 feet) in length, 1.7 m (5.6 feet) in height, and weighed 6 tonnes (13,000 lb). It was a quadrupedal animal, with a broad, robust body. It had a wide, low skull, with two horns pointing backwards from the back of the head, and two horns below these that pointed backwards and down. The front part of the jaws were covered in a beak, with rows of small, leaf-shaped teeth further behind it. It was covered in armor plates, or osteoderms, with bony half-rings covering the neck, and had a large club on the end of its tail. Bones in the skull and other parts of the body were fused, increasing their strength, and this feature is the source of the genus name.

Ankylosaurus is a member of the family Ankylosauridae, and its closest relatives appear to be Anodontosaurus and EuoplocephalusAnkylosaurus is thought to have been a slow moving animal, able to make quick movements when necessary. Its broad muzzle indicates it was a non-selective browser. Sinuses and nasal chambers in the snout may have been for heat and water balance or played a role in vocalization. The tail club is thought to have been used in defense against predators or in intraspecific combat. Ankylosaurus has been found in the Hell Creek, Lance, and Scollard formations, but appears to have been rare in its environment. Although it lived alongside a nodosaurid ankylosaur, their ranges and ecological niches do not appear to have overlapped, and Ankylosaurus may have inhabited upland areas. Ankylosaurus also lived alongside dinosaurs such as TyrannosaurusTriceratops, and Edmontosaurus.


Ankylosaurus is the largest known ankylosaurid dinosaur, estimated to have been up to 6.25 m (20.5 feet) long, 1.5 m (4.9 feet) wide, and 1.7 m (5.6 feet) tall at the hip. This length has been proposed by American palaeontologist Kenneth Carpenter, and is based on the largest known skull (specimen NMC 8880), which is 64.5 cm (25.4 inches) long and 74.5 cm (29.3 inches) wide. The smallest known skull (specimen AMNH 5214) is 55.5 cm (21.9 inches) long and 64.5 cm (25.4 inches) wide, and this specimen is estimated to have been 5.4 m (17.7 feet) long and around 1.4 m (4.6 feet) tall. Other authors have proposed a body length of 7 m (23 feet), 8–9 m (26.2–29.5 ft), or more than 9 m (29.5 feet). The weight of the animal has been estimated at 6 tonnes (13,000 lb).

The structure of much of the skeleton of Ankylosaurus, including most of the pelvis, tail and feet, is still unknown. It was quadrupedal, and its hind limbs were longer than the forelimbs. The scapula (shoulder blade) and coracoid (a rectangular bone connected to the lower end of the scapula) of specimen AMNH 5895 were fused, and had entheses (connective tissue) for various muscle attachments. The scapula was 61.5 cm (24.2 inches) long. The humerus (upper arm bone) was short and very broad, and about 54 cm (21 inches) long in specimen AMNH 5214. The femur (thigh bone) was very robust, and 67 cm (26 inches) long in AMNH 5214. While the feet of Ankylosaurus are incompletely known, the hindfeet probably had three toes, as is the case in related animals.


The three known Ankylosaurus skulls differ in various details, but this is thought to be the result of taphonomy (changes happening during fossilisation of the remains) and individual variation. The skull was low and triangular in shape, wider than it was long. It had a broad beak on the premaxillae. The orbits (eye sockets) were almost round to slightly oval and did not face directly sideways, because the skull tapered towards the front. Crests above the orbits merged into the upper squamosal horns (their shape has been described as “pyramidal”), which pointed backwards to the sides from the back of the skull. The crest and horn were probably separate elements originally, as seen in the related Pinacosaurus and Euoplocephalus. Below the upper horns, jugal horns were present, which pointed backwards and down. The horns may have originally been osteoderms (armor plates) that fused to the skull. However, the scale pattern on the skull surface was instead the result of remodelling of the skull. This obliterated the sutures between skull elements, which is common for adult ankylosaurs. The scale pattern of the skull was variable between specimens, though some details are shared; it had a diamond-shaped scale (internarial scale) at the font of the snout, two squamosal osteoderms above the orbit, and a ridge of scales at the back of the skull.

Cast of Ankylosaurus skull (AMNH 5214) in front view, Museum of the Rockies


 A prominent feature of Ankylosaurus was its armor, consisting of knobs and plates of bone known as osteoderms or scutes embedded in the skin. These have not been found in articulation, so their exact placement on the body is unknown, though inferences can be made based on related animals. The osteoderms ranged from 1 cm (0.4 inches) in diameter to 35.5 cm (14.0 inches) in length, and also varied in shape. The osteoderms of Ankylosaurus were generally thin walled and hollowed on the underside. Compared to Euoplocephalus, the osteoderms of Ankylosaurus were smoother in texture. The osteoderms covering the body were very flat, though with a low keel at one margin. In contrast, the nodosaurid Edmontonia had high keels, stretching from one margin to the other on the midline of its osteoderms. Ankylosaurus had some smaller osteoderms with a keel across the midline. Some osteoderms without keels may have been placed above the hip region, as in Euoplocephalus. Flattened, pointed plates resemble those on the sides of the tail of Saichania. Osteoderms with oval keels could have been placed on the upper side of the tail or the side of the limbs. Small osteoderms and ossicles likely occupied the space between the larger ones.

Only known tail club (AMNH 5214), American Museum of Natural History


Brown considered Ankylosaurus so distinct that he made it the type genus of a new family, Ankylosauridae (members of which are called ankylosaurids), typified by massive, triangular skulls, short necks, stiff backs, broad bodies, and osteoderms. He also classified Palaeoscincus (only known from teeth), and Euoplocephalus (then only known from a partial skull and osteoderms) as part of the family. Due to the fragmentary remains, Brown was unable to fully distinguish between Euoplocephalus and Ankylosaurus. Only having few, incomplete members of the family to compare with, he believed the group was part of the suborder Stegosauria. In 1923, Osborn coined the name Ankylosauria (members of which are called ankylosaurs or ankylosaurians), thereby placing the ankylosaurids in their own suborder.

Ankylosauria and Stegosauria are now grouped together within the clade Thyreophora. This group first appeared in the Sinemurian age, and survived for 135 million years, until disappearing in the Maastrichtian. They were widespread and inhabited a broad range of environments. As more complete specimens and new genera have been discovered, theories about ankylosaurian interrelatedness have become more complex, and hypotheses have often changed between studies. In addition to Ankylosauridae, Ankylosauria has been divided into the families Nodosauridae, and sometimes Polacanthidae (these families lacked tail clubs). Ankylosaurus is considered part of the subfamily Ankylosaurinae (members of which are called ankylosaurines) within Ankylosauridae. Ankylosaurus appears to be most closely related to Anodontosaurus and Euoplocephalus. The following cladogram is based on a 2015 phylogenetic analysis of the Ankylosaurinae conducted by Arbour and Currie:

Phylogenetic analysis of the Ankylosaurinae

Since Ankylosaurus and other Late Cretaceous North American ankylosaurids grouped with Asian genera (in a tribe the authors named Ankylosaurini), Arbour and Currie suggested that earlier North American ankylosaurids had gone extinct by the late Albian or Cenomanian ages of the Middle Cretaceous. Ankylosaurids thereafter recolonised North America from Asia during the Campanian or Turonian ages of the Late Cretaceous, and diversified there again, leading to genera such as AnkylosaurusAnodontosaurus, and Euoplocephalus. This explains a 30 million year gap in the fossil record of North American ankylosaurids between these ages.


Ankylosaurus existed between 68 and 66 million years ago, in the final, or Maastrichtian, stage of the Late Cretaceous Period. It was among the last dinosaur genera that appeared before the Cretaceous–Paleogene extinction event. The type specimen is from the Hell Creek Formation of Montana, while other specimens have been found in the Lance Formation of Wyoming and the Scollard Formation in Alberta, Canada, all of which date to the end of the Cretaceous. Fossils of Ankylosaurus are rare in these sediments, and the distribution of its remains suggest that it was restricted to the uplands of the formations, rather than the coastal lowlands. Another ankylosaur, an indeterminate nodosaur (formerly referred to as Edmontonia sp.), is also found in the same formations, but the range of the two genera does not seem to have overlapped. Their remains have so far not been found in the same localities, and the nodosaur appears to have inhabited the lowlands. The narrow muzzle of the nodosaur suggests it had a more selective diet than Ankylosaurus, further indicating ecological separation.

Map showing where Ankylosaurus fossils have been discovered

The Hell Creek, Lance and Scollard Formations represent different sections of the western shore of the Western Interior Seaway that divided western and eastern North America during the Cretaceous. They represent a broad coastal plain, extending westward from the seaway to the newly formed Rocky Mountains. These formations are composed largely of sandstone and mudstone, which have been attributed to floodplain environments. The regions where Ankylosaurus and other Late Cretaceous ankylosaurs have been found had a warm subtropical/temperate climate, which was monsoonal, had occasional rainfall, tropical storms, and forest fires. In the Hell Creek Formation, many types of plants were supported, primarily angiosperms, with less common conifers, ferns and cycads. An abundance of fossil leaves found at dozens of different sites indicates that the area was largely forested by small trees. Ankylosaurus shared its environment with dinosaurs including the ceratopsids Triceratops and Torosaurus, the hypsilophodont Thescelosaurus, the hadrosaurid Edmontosaurus, an indeterminate nodosaur, the pachycephalosaurian Pachycephalosaurus, and the theropods StruthiomimusOrnithomimusTroodon, and Tyrannosaurus.