Spinosaurus

Spinosaurus aegyptiacus ("Egyptian spine lizard") is a theropod dinosaur genus from the Albian to early Cenomanian stages of the Cretaceous time, about 95 to 93 million years ago. Its distinctions comprise being the biggest meat-eating of all dinosaurs, rivaling even Tyrannosaurus rex (at somewhere between 40 and 60 feet (12 to 20 meters) long, 16 to 20 feet (4.8 to 6 meters) tall, and 5 to 7 tons), having large bones extending from the vertebrae up to 6 feet long. These spines most probable had skin or a membrane stretching between them, forming a sail-like arrangement. Spinosaurus provides the name of a family of dinosaurs, the Spinosauridae, of which other members include Angaturama (probably synonymous with Irritator), Baryonyx, Irritator, Suchomimus, and Siamosaurus.

Much mystery environs the nature of this animal. First of all, although it has been well-known to dinosaur enthusiasts because of its strange features, even before it was popularized by its role as main rival in Jurassic Park III, it is mostly known through remains that have been destroyed, aside from a few more newly discovered teeth. Unpublished jaw and skull material suggest that it may have had one of the longest skulls of any carnivorous dinosaur. Initially found in the Baharija Valley of Egypt in 1912, it was named by German paleontologist Ernst Stromer in 1915. Some of the fossils were damaged during convey back to the Munich Museum in Germany, and the remaining bones were completely lost due to Allied bombing in 1944.

Aside from its sail, notable individuality of Spinosaurus includes:

* Long, narrow snout similar to other Spinosaurids, and like them overflowing with conical teeth.
* Slender build.
* One enlarged, hook-like claw on each of its front limbs, perhaps for infectious fish.
* Relatively short legs and long arms, leading some paleontologists to propose it may have been quadrupedal, rather than severely bipedal (though it was undoubtedly capable of at least facultative bipedality).
* Much of this is conjecture based on Baryonyx and other Spinosaurids, as no limb material has ever been credited to Spinosaurus.

Scientists differ whether Spinosaurus was a cursorial predator (like Tyrannosaurus rex) or a docile fisher, sitting lazily by riverbanks and snatching up powerless prey as they swam by. In Jurassic Park III, it is portrayed as a lethal and unsafe killer, even winning a battle with a Tyrannosaurus. However as noted above, in spite of its length, it was more lightly built than Tyrannosaurus and other theropods, and its stretched out jaws and conical teeth suggest it may have mainly eaten fish, or else fed on carrion, rather than being a hunter of large prey like Tyrannosaurus.

Also, the reason of its sail is unclear. Scientists have optional it could have been used to regulate temperature, or to attract mates, or to intimidate rivals. However, the use of such an odd structure can almost certainly only be based on speculation. The fact that other dinosaurs of the same time and area, namely the ornithopod Ouranosaurus and the sauropod Rebbachisaurus, possessed a alike structure is interesting. The sail is possible analogous (not homologous) to that of the Permian mammal-like reptile, Dimetrodon, who lived previous to the dinosaurs even appeared, strongly points in the direction of parallel evolution.

It is very likely that the sail was very vascular and used by the animal to heat itself up when sunrise took place, by rotating the sail at a 90 degree angle to the rising sun. This would entail that the animal was only partly warm-blooded at best and lived in climates where nighttime temperatures were cool or near to the ground and the sky usually not cloudy. It is consideration that Spinosaurus and Ouranosaurus both lived in or at the margins of an earlier version of the Sahara Desert, which would explain this.

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Megalosaurus

Megalosaurus was a species of large meat-eating dinosaurs of the Jurassic period.

Megalosaurus was one of the primary dinosaurs to be described. Part of a bone was improved from a limestone quarry at Cornwell near Oxford, England in 1676. The fragment was sent to Robert Plot, Professor of Chemistry at the University of Oxford and first guardian of the Ashmolean Museum, who published a description in his Natural History of Oxfordshire in 1677. He correctly identified the bone as the lower extremity of the femur of a large animal, and he documented that it was too large to belong to any known species; he measured it to be the thigh bone of a giant. The bone has since been lost but the depiction is detailed enough to identify it clearly as the femur of a Megalosaurus.

The Cornwell bone was described again by Joshua Brookes in 1763, who named it Scrotum humane based on the similarity of appearance to a pair of human testicles. (Although this name theoretically has priority, succeeding authors have chosen to treat it is as joke rather than a serious effort to propose a scientific name, or possibly not compliant with binomial nomenclature but rather with the old, descriptive approach).

More discoveries were made preliminary in 1815, this time at the Stones field quarry north of Oxford, and they were acquired by William Buckland, Professor of Geology at the University of Oxford and dean of Christ Church.

Engraving from William Buckland's "Notice on the Megalosaurus or huge Fossil Lizard of Stonesfield", 1824. Caption reads "anterior edge of the right lower jaw of the Megalosaurus from Stones field near Oxford”. Physician James Parkinson described them in an article in 1822, and two years later Buckland published his own paper. By 1824, he had a part of a lower jaw with teeth, some vertebrae, and fragments of pelvis, scapula and hind limbs, almost certainly not all from the same individual. Buckland recognized the organism as being a giant animal related to the Sauria (lizards), and he named the genus Megalosaurus, estimating it to be 40 feet (12 m) long. In 1826 Georges Cuvier gave this dinosaur its species name: Megalosaurus bucklandi ("Buckland's big lizard").


Since those first finds, many other Megalosaurus bones have been improved, but still no complete skeleton has been establish. Therefore we cannot be certain about the details of Megalosaurus's physical look. Early paleontologists, never having seen such a creature before, reconstructed it like the dragons of well-liked mythology, with a huge head and walking on all fours. It was not until the middle of the nineteenth century, when other theropods began to be discovered in North America, that a more accurate picture was developed. Some bewilderment still exists, for at one time (before classification of dinosaurs became the serious business it is today) all theropods from Europe were given the title Megalosaurus.

Since then, these have been characteristically reclassified but older papers are often the cause of confusion. For further confusion, the most reproduced anatomy diagram of Megalosaurus' skeleton was shaped before any vertebrae had been recovered. While drawing it, Friedrich von Huene of the University of Tubingen, Germany, instead used the backbones of Altispinax, a mysterious big theropod known from high-spined dorsal vertebrae and at times secret as a spinosaur. Hence, many later drawings based on his original show Megalosaurus with a deep spinal ridge or even a small sail like that of Spinosaurus.

Modern reconstructions

In fact, Megalosaurus did have a comparatively large head and the teeth were clearly that of a carnivore. However, the long tail would have balanced the body and head and so Megalosaurus is now restored as a bipedal beast like all other theropods, and about nine meters in length. The structure of the cervical vertebrae suggests that its neck would have been very supple. To support its weight of around one tonne, the legs were large and muscular. Like all theropods, it had three onward facing toes and a single reversed one. Although they had not reached the minuscule size of later theropods like Tyrannosaurus, Megalosaurus' arms were small and almost certainly had three or four fingers.

Living in what is now Europe throughout the Jurassic Period (181 to 169 million years ago), Megalosaurus may have hunted stegosaurs and sauropods. Repeated descriptions of Megalosaurus hunting Iguanodon (another of the earliest dinosaurs named) through the forests that then enclosed the continent are probably inaccurate, because Iguanodon skeletons are found in much younger Early Cretaceous formations. No fossils transferable to Megalosaurus have been discovered in Africa, contrary to some outdated dinosaur books.

Although Megalosaurus was an influential carnivore and could probably have attacked even the largest sauropods, it is also probable that it gained some of its food by scavenging. That is not to detract from its ability as a hunter - Tyrannosaurus probably did much the same. Efficiency was essential to feed such a large body.

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Ceratosaurus

Ceratosaurus ("horned lizard") is a greedy dinosaur from the Late Jurassic Morrison Formation of North America. It is characterized by huge jaws with enormous, bladelike teeth, a large, bladelike horn on the snout, and a pair horn lets over the eyes. The forelimbs were strongly built but very short. The type species is Ceratosaurus nasicornis, although numerous other species have been named, including C. dentisulcatus and C. magnicornis.

Ceratosaurus is known from the Cleveland-Lloyd quarry in central Utah and Dry Mesa in Colorado. It lived next to dinosaurs such as Allosaurus, Torvosaurus, Apatosaurus, Diplodocus, and Stegosaurus. Some propose it was a rival to Allosaurus.

Ceratosaurus was around 4.5–6 m in size, weighing 500 kg up to 1 tonne. The African C. ingens may have been much better, with size estimates ranging up to 5 tonnes, which if right would make it one of the largest of the Theropoda.

Relatives of Ceratosaurus contain Elaphrosaurus and the abelisaur Carnotaurus.
Filmography

A Ceratosaurus battles a Triceratops in the 1966 remake of 1 Million Years B.C. In Jurassic Park III, a Ceratosaurus has a brief look. In the film When Dinosaurs Roamed America, a Ceratosaurus makes a small number of appearances but is later killed by an Allosaurus and eaten.

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Dilophosaurus

Dilophosaurus wetherilli is an near the beginning Jurassic theropod dinosaur. It had paired curved crests on its skull, mostly likely for display. The actual dinosaur deliberate around 6 meters long and may have weighed half a ton. The fossils of Dilophosaurus come from the Navajo Indian Reservation, just west of Tuba City, Arizona. Remains were also established in Schenectady, New York. Just a few tens of feet below the level of the bones, large footprints of carnivorous dinosaurs are found, and these may fit in to Dilophosaurus. The unique description was published in 1954 by the renowned paleontologist Samuel Welles; however, at the time, it was thought to be another genus of theropod (Megalosaurus). In 1970, it was documented to be distinct and given its own generic name Dilophosaurus (meaning "two-crested lizard"). Welles later redescribed the entire taxon in 1984 in a much more total paper. Dilophosaurus may be a primitive member of the clade containing together ceratosaurian and tetanuran theropods. Alternatively, some paleontologists classify this genus as a large coelophysoid.

There is an additional species of Dilophosaurus (D. sinensis) which may or may not belong to this genus. It is possibly closer to the bizarre Antarctic theropod Cryolophosaurus, based on fact that the anterior end of the jugal does not contribute in the internal antorbital fenestra and that the maxillary tooth row is totally in front of the orbit and ends anterior to the vertical strut of the lacrimal. This species was recovered from the Yunnan Province of China in 1987 with the prosauropod Yunnanosaurus, and later described and named in 1993 by Shaojin Hu.

Dilophosaurus was also fitted in the 1993 movie Jurassic Park (and the book by Michael Crichton on which the film was based). It sported a retractable frill around its neck, much like a frilled lizard, and was clever to spit poison, aiming for the eyes to blind and paralyze its prey. There is no proof to support this representation. In the film, director Steven Spielberg also abridged its size, from moderately large to about 3 feet tall and 5 feet long - this was to keep rivalry low for the main star of the movie, Tyrannosaurus rex. Paleontologists, however, have exposed that Dilophosaurus had very weak mandibles, making it not possible for it to kill its prey by biting it without sustaining severe wounds (breaking of the jaw). This might be the basis for the theory of the poison, a way to debilitate its prey without putting itself at risk, which is in attendance in the book. The frill is possible, but no evidence has been found to hold up it.

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Dromiceiomimus

Dromiceiomimus dinosaur (meaning "emu mimic") was a very fast-moving (perhaps over 40 mph = 64 km/h) bipedal dinosaur from the late Cretaceous time, about 75 to 70 million years ago.

It was about 12 feet (3.6 m) long and weighed concerning 220 to 330 pounds (100 to 150 kg). Its femur (thigh bone) was 468 mm long. This ornithomimid (a bird-like theropod) had extremely long limbs and large eyes. It had a toothless, beaked mouth, and weak jaws; it may have eaten insects, eggs and some meat.

It was named by D. A. Russell in 1972 and now displayed in the natural history museum, london. The type class is D. brevitertius. Fossils of adults and juveniles have been established in Alberta, Canada. Trivia Dinosaur Comics contains a dromiceiomimus as a major character. It most probably hunted after dark, chasing small mammals and lizards through the deciduous woods.
Dromiceiomimus facts:
Name: Dromiceiomimus ("emu mimic")
Size: 11 ft long
Main Facts: The size of brain cavity and eye sockets in the skull shows Dromiceiomimus had exceptionally large brain and huge eyes.


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Elaphrosaurus

Elaphrosaurus ("lightweight lizard") from the Late Jurassic of Tanzania was about 20 ft long and weighed about 210 kilograms.

Elaphrosaurus Dinosaur was probably a Ceratosaur and its skeleton was found in the Tendaguru Beds of Tanzania, which also yields the Giraffatitan, Allosaurus, and Kentrosaurus. A related animal, perhaps the same species, was found in the Morrison Formation.

Unfortunately the skull was missing and only one skeleton of Elaphrosaurus has been found. It was very much longer than its thigh bone, which shows that it could probably run very fast. The characteristic features of Elaphrosaurus were that they had no teeth and it’s impossible to say whether it might belong to this family. Loose teeth have been found in same sediment and that may belongs to that dinosaur family.

Elaphrosaurus was discovered by Werner Janensch in 1920 and it’s displayed in Natural History Museum
Elaphrosaurus facts:
Name: Elaphrosaurus "lightweight lizard"
Size: 20 ft long
Main Facts: Elaphrosaurus was very much longer than its thigh bone, which shows that it could probably run very fast.

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Coelurus

Coelurus had a small, low head like all the members of coelurid family which is about 8 in/20 cm long. Coelurus a genus of coelurosaur dinosaur from the Late Jurassic period means "hollow tail". Only one species is currently familiar, C. fragilis, described by Othniel Charles Marsh in 1879 and it’s displayed in the Natural History Museum, London.

Coelurus Dinosaur was a small bipedal carnivore with elongated legs and the hollow, birdlike bones (slender and considerably more elongate respect to fumur length) that characterized all early dinosaurs. The neural canal is also large in coelurus, although it is not elliptical but square.

The bone is 7.9 cm long and 1.1 cm tall, its vertebrae were long and low and thin walls to the bodies of the vertebrae.

The three best-known small theropods are Coelurus, Ornitholestes, and Tanycolagreus. Now Coelurus is possible to distinguish from Ornitholestes by various characteristics of their anatomy were Coelurus had a longer back and neck than Ornitholestes, and longer, more slender legs and feet. Coelurus and Tanycolagreus are more similar, but differ in a variety of details like shape of the upper arm, forearm, and thigh bones.

This active predator lived in forests of North America where prey was rich. Its three clawed fingers were long and strong which is designed for grasping the flesh of small animals like lizards and mammals.

Name: Coelurus (hollow tail)
Size: 140cm long and 70cm tall
Main Facts: Coelurus had a small, low head that charecerized all early dinosaurs.

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Procompsognathus

Procompsognathus is a genus of small theropod dinosaur, meat eating dinosaur and also one of the earliest dinosaur which is lived during Triassic times.

Procompsognathus Dinosaur is about 1.2 meters long (4 ft), had long hind legs, short arms, large clawed hands, a long slight snout with many small teeth, and also had a stiff tail. It’s lived in inland environment and would have chased after small lizards and insects and other small prey on its long legs running with only 3 of its 4 toes touching the ground.

Name: Procompsognathus (small theropod dinosaur)
Size: 4ft long and 10 inches tall
Main Facts: Procompsognathus was a earliest dinosaur that covered northern Europe during Triassic period.

Procompsognathus was named by Eberhard Fraas in 1913 and it was found in the Natural History Museum in London. The primitive features like each hand of Procompsognathus had 5 fingers, since the trend in the more advanced dinosaurs was to have fewer fingers and toes.

It has historically been considered a theropod dinosaur, although some have found Procompsognathus to be a primitive, non-dinosaurian ornithodiran.

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Ornithomimus

Ornithomimus ('bird mimic') is a genus of dinosaur from the Late Cretaceous which is mainly characterized by a three-toed foot, long slender arms and a long neck with a birdlike skull. It also had a small, thin boned head with a large brain cavity and beaklike jaws.

Ornithomimus Dinosaur differs from other ornithomimids, like Struthiomimus, in having very slender, straight hand and foot claws and fingers of related lengths. It had sprinted along with its body parallel to ground, balanced by its long and out-stretched tail and it was kept stiff by strong ligaments that lashed the vertebrae to form a rigid structure. Its neck have curved upward in a long bend and holding the head for good visibility by means of large eyes.

The arms of Ornithomimus have dangled above the ground with dexterous and clawed fingers which is held ready to grasp potential food. It was bipedal and resembled an ostrich, which is 12 ft (3.5 meters) long, 7 feet (2.10 meters) high and weighed around 100–150 kg. It also seems to have feeding habits more like that of a duck than an ostrich.

Like other ornithomimids, it may also eat leaves, fruits, insects and other small animals like lizards and mammals and it even raided the nests of other dinosaurs and eaten their eggs, pecking through shells with its horny beak. It might run away at a speed of upto 30mph/50 kmph. Ornithomimus was first discovered by J.B.Hatcher in Denver Colorado. Its now displayed at the Royal Ontario Museum, Toronto.

Name: Ornithomimus (bird mimic)
Size: 20 ft long and 8 ft tall
Main Facts: Ornithomimus was a meat and plant eaters and could probably run like an Ostritch.

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Dinosaur struthiomimus

Struthiomimus Dinosaur (ostrich mimic) is a genus of ornithomimid dinosaur from the late Cretaceous period of Alberta, Canada. Struthiomimus was discovered in the year 1914 which was thought to be as like Ornithomimus. But after research in 1972, it shows that both were differ. It had longer arms and stronger, curved claws on its fingers. It’s now displayed at the American Museum of Natural History.

The first known fossils of Struthiomimus were named as Ornithomimus sedens by Othniel Charles Marsh. The bipedal Struthiomimus was about 4.3mts long and 1.4mts tall and weighed around 150 kilograms.

Struthiomimus had a usual build and skeletal structure for an ornithomimid and its eyes were large, jaws were toothless. Its vertebral column had ten neck vertebrae, sixteen back vertebrae, six hip vertebrae, and an unknown number of tail vertebrae. Its legs were only moderately elongate and its feet were elongate with three toes tipped by claws.

Struthiomimus, being a member of Coelurosauria, most likely had feathers especially if the Ornithomimosauria and the alvarezsauridae are closely related. It appears like modern ground birds such as ostriches and emus. It’s believed to be the fastest dinosaurs and it may able to run faster than ostriches.

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Adasaurus Dinosaur

Adasaurus Dinosaur (Ada Lizard) was a bird-like carnivorous dinosaur that lived 70 million years ago, throughout the late Cretaceous Period. (The name comes from the name of a mythological evil demon of Mongolia.)

Adasaurus is found in The Field Museum which was named by Rinchen Barsbold in 1983. It has been described as being very alike to Archeopteryx and its discovery added fuel to the present debate concerning dinosaurs and birds. Only unfinished fossils have been found, all in Mongolia, but based mainly in the Gobi desert region.

At six feet (two meters) long and two feet (.7 meters) tall, normally about he size of a large dog, Adasaurus weighed only 33 pounds (15 kilograms) and may have had feathers. Like Velociraptor dinosaurs, it was bipedal with a big, sickle-like claw on each foot.

Aspects of the Adasaurus dinosaurs pelvis, which is very alike to that of ornithischians, lead some scientists to believe that it is actually more closely connected to birds than to dinosaurs.

Name: Adasaurus Dinosaur (Ada Lizard)
Size: 6 feet long and 2 feet tall.
Main Facts: Its very likely to that of ornithischians, lead some scientists to believe that it is actually more closely connected to birds than to dinosaurs

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Abelisaurus Dinosaur

Abelisaurus (Abelisaurus comahuensis), meaning "Abel's lizard", was a type of dinosaur. It was discovered by Othenio Abel, the director of the Argentinian Museum of Natural Science, and named by J.F. Bonaparte and F.E. Novas in 1985.

Abelisaurus Dinosaur has been establish in Rio Negro in Argentina, and is supposed to have lived around 75 to 70 million years ago, during the late Cretaceous period. It is known from a single incomplete, 33-inch (85 cm) long skull. It had strangely heavy teeth, and thus was possibly in part a scavenger.

Abelisaurus Dinosaur was a bipedal carnivore, a primitive theropod dinosaurs, standing roughly 6.6 feet (2 metres) tall at the hips, 21 to 26 feet (almost 8 meters) long and weighing 1.4 tons. Large fenestrations (window-like openings) in the Abelisaurus's skull meant that its skull was lighter than most dinosaurs.

Abelisaurus Dinosaur may have been connected to carnotaurus dinosaurs, which also lived in Argentina over 70 million years ago, and perhaps to indosuchus.

Name: Abelisaurus "Abel's lizard"
Size: 25 to 30 feet in length
Main Facts: Standing roughly 6.6 feet (2 metres) tall at the hips and weighing 1.4 tons.

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Gasosaurus

Gasosaurus was a tetanuran dinosaur exposed in Dashanpu, China. It had strong legs but short arms, and powerful jaws point to that it was a carnivore. It measured between 3.5 and 4 meters in length and 1.3m in height, with a weight of approximately 150[kg], placing it in the midrange of carnivores by size. However, some estimates put its weight as high as 400kg, as very little is known about this dinosaur. It lived throughout Bathonian and Callovian periods (mid-late Jurassic), around 164 million years ago. By analogy with additional tetanurans, it probably hunted in packs.

The first and to date only fossils, albeit postcranial (missing the skull), were healthier in 1985 during the construction of a gas facility. This explains the unusual name, which literally means gas lizard. These fossils were defined as the category species Gasosaurus constructs by the paleontologists Dong Zhiming and Tang Zilu. There have still been very few fossils retrieved, so its precise details are unknown. Specifically, no skull has been established, and some paleobotanists have speculated that Gasosaurus and Kaijiangosaurus may be one and the same species. A relation to Megalosaurus has also been suggested. Also, although present consensus is to place Gasosaurus in the group Carnosauria, it may in fact be the most basal Coelurosaurian yet known, or even be a common ancestor of the two groups.

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Saurornitholestes

Saurornitholestes langstoni (Langston's lizard-bird thief) is a coyote-sized carnivorous dromaeosaurid dinosaur genus from the Upper Cretaceous (Upper Campanian) of Alberta, Canada. Several incomplete skeletons, dozens of isolated bones, and scores of teeth are known from the badlands of Dinosaur Provincial Park in Alberta; most of these are housed at the Royal Tyrrell Museum of Palaeontology, in Drumheller, Alberta.

Like other theropods in the family Dromaeosauridae, Saurornitholestes had a extended, curving, bladelike claw on the second toe. Saurornitholestes was more long-legged and flippantly built than other dromaeosaurids such as Velociraptor and Dromaeosaurus. It resembles Velociraptor in having large, fanglike teeth in the face of the jaws. Saurornitholestes most intimately resembles Velociraptor, although the precise relationships of the Dromaeosauridae are still comparatively poorly understood.

Saurornitholestes appears to have been the most ordinary small theropod in dinosaur Provincial Park and teeth and bones are much more ordinary than those of its more massive contemporary, Dromaeosaurus. Little is known about what it ate and how it lived, but a tooth of Saurornitholestes has been found entrenched in the wing bone of the pterosaur Quetzalcoatlus. Whether it in fact killed the pterosaur or merely scavenged an already dead animal is unknown.

Similar teeth are established in younger deposits, but whether they stand for S. langstoni or a different, related species is unknown.

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Noasaurus Dinosaur

Noasaurus belongs to the family Noasauridae where Noasaurids be a grouping of theropod dinosaurs from the Cretaceous Period. It’s generally small in size and very much similar to the Abelisauridae.


The theropod family’s Abelisauridae and Noasauridae were closely interrelated because of shared derived characters such as the preantorbital fenestra, the short anterior area of the maxilla, the quadrate fused to the quadratojugal and cervical vertebrae with vestigial neural spines and hypertrophied epipophyses.


Basically it was small (fewer than eight feet long) theropod, particularly a ceratosaur, discovered by Jaime Powell and José Bonaparte from the Lecho Formation of Salta Province, Argentina. It was a close comparative of the larger abelisaurids. They both were derived from the same basal abelisauroid ancestor.Noasaurus situated distant prey by smell, would come near and wait in trap, judge distance, then rush in rapid explode of speed. It mainly attack using kicks and lacerate with huge pedal claw.


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Saltopus

Saltopus is the smallest and lightest dinosaurs which is similar to procompsognathus, was not tall as domestic cat which is weighed as 21b/1 kg.

Saltopus elginensis is considered to be Scotland's oldest dinosaur. It was discovered by chemist William Taylor, but was donated to the Natural History Museum in London. It was a very little bipedal reptile, roughly 23 inches (60 centimeters) long, discovered in Scotland. It was a late Triassic carnivore and it may have weighed in at approximately two pounds (one kilogram), and had five-fingered hands and a long head with dozens of sharp teeth. None of this can be recognized for certain, as Saltopus is known only from very poor fabric (mostly hind limb fragments).

As small as it was, its carnivorous diet must have consisted first and foremost of scavenged carcasses or insects. It has been variously recognized as a saurischian (lizard-hipped) dinosaur; a theropod (a fast-moving bipedal carnivore with clawed digits and hands on the forelimbs); and a close family member of the Herrerasaurus of the Herrerasauria infraorder, but its taxonomy is in argument because only fragmentary remains have been recovered. It may also have been a lagosuchid (a primitive reptile from which the dinosaurs arose) or an ornithosuchian (closely connected cousins of dinosaurs) instead of a true dinosaur. It has also been optional that the supposed Saltopus remains may, in fact, be incomplete remains of some already-identified animal.

Name: Saltopus elginensis
Size: 2 ft/60cm long
Main Facts: Four of the spine’s sacral vertebrae were fused to its hips and this is a fairly solid anchor for the long running legs.

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Buitreraptor

Buitreraptor gonzalezorum is a newly exposed fossil species, a small rooster-size predatory dinosaur belonging to the dromaeosaurid family. The discover occurred in Argentina in 2005.

Buitreraptor gonzalezorum is the only known species of the genus Buitreraptor. The genus name means "Vulture-raptor", from the Spanish word buitre gist vulture.

Buitreraptor lived about 90 million years ago, when South America was a remote continent like Australia today. Buitreraptor has some different physical features than typical northern dromaeosaurs, like Velociraptor .Buitreraptor has a slim snout with teeth that lack meat-tearing serrations. From this scientists end that this dinosaur was not a big-game hunter like most other dromaeosaurs, but a seeker of small animals such as lizards and mammals. Its long bird-like arms confirm such a life of greedy fast-moving small prey. It has long legs and must have been an nimble runner. It most likely had feathers. This dromaeosaur occupied a niche like that of modern secretarybirds or even the dinosaur Troodon from North America.

Other than Buitreraptor, the only other known dromaeosaurs from the southern continents are Neuquenraptor argentinus from South America (discovered earlier in 2005), Rahonavis (once thought to be a primitive bird) from Madagascar, and nameless dromaeosaur-like teeth from Australia. The bones in both Buitreraptor and Rahonavis show that motorized flight likely evolved separately in two different groups of dinosaurs: birds and southern dromaeosaurs.

This discovery in the Southern-Hemisphere confirms that dinosaurs were more extensively dispersed around the world than previously thought. Scientists now believe that dromaeosaurs date back to Jurassic times, when all the continents were much closer together. Possibly they originated on the ancient continent Laurasia.

The fossilized bones were found in 2005 in sandstone in Patagonia, Argentina - by an dig lead by Peter Makovicky, curator of dinosaurs at the Field Museum in Chicago). Buitreraptor was discovered in the same fossil site that had earlier yielded Giganotosaurus, the largest carnivorous dinosaur known to science since 1995.

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Bruhathkayosaurus

Bruhathkayosaurus (brew-HATH-kah-yo-SORE-us, meaning "huge bodied lizard") might have been the biggest dinosaur ever lived.

The accuracy of this claim, however, has been mired in controversy and debate: all the estimates are based on Yadagiri and Ayyasami's 1989 paper, which announced the find. Their technical description is so poor that the authors originally confidential the dinosaur as a theropod, a member a large group of bipedal, carnivorous dinosaurs that includes the Tyrannosaurus; but a review of their data in 1995 exposed that the remains actually belonged to a sauropod (specifically, a titanosaurid), a member of a very dissimilar group of quadrupedal, herbivorous dinosaurs with lengthy necks and tails, like the Brachiosaurus.
Classification
The Bruhathkayosaurus genus has only one known species, the Bruhathkayosaurus matleyi. The species is represented by the holotype specimen GSI PAL/SR/20, which was described by Yadagiri and Ayyasami in 1989 (not 1987, as some sources indicate).

It was initially classified as a carnosaur (like the Allosaurus) of an unidentified (incertae sedis) family, which is a collection of theropods. In 1995 Chatterjee reclassified it as a titanosaur. The reclassification was based on the enormous size of the limbs, and the structure of the pelvis.

The original magazine described little in the way of diagnostic characteristics, and was only supported by a few line drawings. This has led to conjecture that the bones might actually be petrified wood, akin to the way the unique discoverers of the Sauroposeidon initially supposed their find to be fossilized tree trunks.

The name chose, Bruhathkayosaurus, is derived from the Hindi bruhath (huge or heavy) and kaya (body); and the Greek sauros (lizard).

Discovery
The Bruhathkayosaurus was establishing near the southern tip of India, specifically in the Tiruchirapalli district of Tamil Nadu, to the northeast of Kallamedu village. It was improved from the rocks of the Kallemedu Formation, which are dated to the Maastrichtian faunal stage of the late Cretaceous period. It lived in the direction of the end of Mesozoic era, about 70 million years ago.

The fossilized remains include hip bones (the ilium and ischium), part of a leg bone (femur), a shin bone (tibia), a forearm (radius), and a tail bone (a vertebrae, specifically a platycoelous caudal centrum).
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Carcharodontosaurus

Carcharodontosaurus ("shark-toothed reptile") was a gigantic carnivorous allosaurid dinosaur that lived approximately 98 to 93 million years ago, during the Cretaceous period. It rival Tyrannosaurus rex in size, growing to a predictable length of 45 feet (13.5 meters) and weighing up to eight tons.

Paleontologists once thought that Carcharodontosaurus had the longest skull of any of the theropod dinosaurs. However, the premaxilla and quadrate bones were missing from the original African skull, which led to misinterpretation of its actual size by researchers. A more self-effacing length of five feet, four inches (1.6 meters) has now been proposed. Thus, the honor of the largest theropod skull now belongs to another huge allosaurid dinosaur, Carcharodontosaurus's close relative Giganotosaurus.

Carcharodontosaurus fossils were first established by Charles Deperet and J. Savornin in North Africa in 1927.

Originally called Megalosaurus saharicus, its name was changed in 1931 by Ernst Stromer von Reichenbach to that used today.These first fossils of Carcharodontosaurus were shattered during World War II. However, cranial material from a Carcharodontosaurus was once more discovered in North Africa in 1996 by paleontologist Paul Sereno.

Carcharodontosaurus was a carnivore, with huge jaws and long, serrated teeth up to eight inches long. It may have hunted in packs like other Allosaurs, but no fossil proof of this exists. It may have been a scavenger as well as an active predator.

Carcharodontosaurus had long, muscular legs and fossilized track ways indicate that it could run about 20 miles per hour, although there is some controversy as to whether it actually did. At eight tons, a forward fall would have been poisonous to Carcharodontosaurus, due to the inability of its small arms to brace the animal when it landed.

According to its Encephalization Quotient (brain to body weight ratio), Carcharodontosaurus may have been comparatively intelligent. Ongoing discoveries and investigate by scientists will certainly shed further light on the physiology, behavior, and ecological circumstances and interactions of Carcharodontosaurus.

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Aublysodon Dinosaur

The Aublysodon is a carnivorous dinosaur. Even before the badlands of North America started enlightening the bones of Tyrannosaurus rex, many paleontologists from the late nineteenth century decided that long, pointed teeth turning up in many localities in the Western United States belonged to the deadliest, most ferocious dinosaurs that ever lived. Problematically, at this time, many dinosaur taxons were named for isolated teeth; such genera include Trachodon, Paleoscincus, and Troodon. Scientists named are particular taxon Aublysodon. Since then, over a dozen type of this supposedly fearsome theropod have been described.

Aublysodon DinosaurThe first post-dentary remains of Aublysodon were a partial skull unearthed in Montana in the 1980s. The skull bore the same pointed teeth attached to a long tapered skull the length of an average human arm. This adaption resembles that of theropods designed for eating fish. Famous dinosaurologist and paleoartist Gregory S. Paul decided the skull should belong to a new class, Aublysodon molnari. Unfortunately, with only this partial skull and isolated teeth, very few other details can be given about this elusive animal. We do know that Aublysodon Dinosaurs was extensive; its remains have been found in many locations.

As with some other theropods, many paleontologists no longer use Aublysodo as a valid genus. It is now extensively considered to be just a juvenile Tyrannosaurus rex, due to longer teeth and larger eyes characteristic of younger specimens of that species.

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Dinosaurs Food Types

Food Types

• Herbivore


• Omnivore


• Carnivore

Herbivore




A herbivore is a creature who eats only plants. He may eat many types of plants, including grass, shrubs, fruit, vegetables etc., but he never eats other animals.

This does not mean that they would not be dangerous. Many herbivores were and still are quite dangerous, if approached. They can see no good reason for you to want to approach them, so they go nuts. A wild horse would be a good example. he would never approach you, since he eats grass, apples etc., not humans. But if you approached him, he would probably become quite dangerous because he can't understand what you want with him (and he worries a little that you may want to eat him).



Omnivore




Just like a herbivore, an Omnivore eats only plants. However, an omnivore tends to stick to only one kind of plant, rather than different types. A good example today, is the Koala bear from Australia. He eats only Euculyptus leaves off the Euculyptus trees. He never ventures out of the Euculyptus trees because there's no point, he simply doesn't want to eat anything else.



Carnivore




A carnivore is a creature that lives mainly on meat (they kill and eat other animals). Most humans are carnivores, and many dinosaurs were too. Some carnivores also eat plants as well, but most stick mainly to meat.




A carnivore is a creature that lives mainly on meat (they kill and eat other animals). Most humans are carnivores, and many dinosaurs were too. Some carnivores also eat plants as well, but most stick mainly to meat.


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Velociraptor

A fully grown velociraptor might look something like this if he was in your garden. He survived on small herbivorous dinosaurs and mammals, and may well have enjoyed a human or two for lunch, if we had been around then.

Living in the late Cretaceous Period from 66.4 to 97.5 million years ago, the Velociraptor was from the dromaeosaur family. He had a sickle like claw on each foot. He would use one of these claws to strike at his prey, slashing it's skin with each strike, whilst balancing himself with his extremely strong tail.

He probably fed on small herbivores (plant eating animals), since he is well built for chasing and killing smaller creatures. He was only about 1.8 metres from nose to tail and only weighed 40-50kg.

Source from Great Site : http://www.dinosaurtypes.org

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Triceratops

Triceratopses (plural of Triceratops) was from a group of herbivorous dinosaurs called the ceratopsians, who all had 3 horns. They lived in teh Late Cretaceous Period of from 66.4 to 97.5 million years ago.

Triceratops was one of the last dinosaurs on Earth. By the time of his extinction, most others had already died out. He had survived the Tyrannosaurus and all other predators for millions of years, but whatever killed off most of the other dinosaurs, also finished him off eventually.

He was probably much like a modern day Rhinosorous today, in many ways. He would have spent most of his day grazing on low plants, and would gather in small herds, for safety (as cows do today). However, if approached (like a Rhinosaurus) he would probably become very vicious indeed, and may well have put up a good fight against Tyrannosaurus when cornered.

He could grow up to 8 metres (25 ft) long and had a long skull with a boney frill around his necy, for pretection against bites. Triceratops had 3 long horns, one on his nose, and the 2 longest ones (each more than 1m or 3ft long) above his eyes. His head alone was more than 2 metres (6ft) long, and from nose to tail, he could easily reach 9 metres (30ft). He was BIG, but Tyrannosaurus Rex was even bigger.

His huge, thick boned body made him a little slow, but his huge strength also made him fearsome, if he needed to be. his legs were short and thick, but very strong. His mouth was very much like a beak at the front, excellent for biting off chuks of plant. But in his cheeks he also had flat or rounded teeth, good for chewing plants properly before he swallowed.

Source from Great Site : http://www.dinosaurtypes.org

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Stegosaurus

Stegosaurus was a common plant-eating dinosaur in western North America during the Late Jurassic Period. It had small, simple teeth, and probably fed on vegetation close to the ground.


Stegosaurus also had weak jaw muscles, implying that it could not chew its food very effectively. It may have required a method similar to the one used by sauropods such as Diplodocus and Apatosaurus. These dinosaurs ripped away huge amounts of plant matter which they barely chewed before swallowing. The food would then ferment in the stomach, ground up by small rocks which the dinosaurs swallowed just for that purpose.


Tall bony plates on its back and paired spikes on its tail give Stegosaurus a very distinctive appearance. The spiked tail was almost certainly used for defense against large predators like Allosaurus. In addition to protecting the dinosaur's back, the bony plates were full of channels for blood vessels, and probably also conducted heat to and from the animal's body.


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Source from Great Site : http://www.dinosaurtypes.org

Alectrosaurus

Alectrosaurus was an Asian Theropod dinosaur that is related to Tyrannosaurus rex. It was a carnivore (meat-eater), and lived in what is today the Gobi desert in Mongolia and China, during late Cretaceous period, between about 83 and 74 million years ago.

Alectrosaurus was probably a maximum of about 17 feet (5 meters) long, and probably weighed somewhere between ½ ton and 1 ton. A number of details of the creature are currently unclear, because only partial fossil specimens have so far been found. Additionally, some paleontologists have suggested that Alectrosaurus may actually be a species of Albertosaurus.

The first fossil specimen of Alectrosaurus was discovered by George Olsen in 1923. It was named by Charles W. Gilmore in 1933. Literally translated from the Greek, "Alectrosaurus" means "unmarried lizard" - Gilmore, chose "unmarried" in the sense of "being alone" - at the time Alectrosaurus was discovered, it was thought to be quite unlike other Asian dinosaurs - although part of the reason was this was that a number of fossil bones from an unrelated dinosaur were initially also thought to belong to the animal.

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Source from Great Site : http://www.dinosaurjungle.com

Albertosaurus

Albertosaurus was a carnivorous (meat-eating) dinosaur that lived in the late Cretaceous period, approximately 76 to 74 million years ago, in North America. It was a bipedal (walking on two legs) creature, with tiny two-fingered hands, and a massive head containing dozens of large sharp teeth.

Albertosaurus was around 26 feet (7.9 meters) long, and weighed approximately 3 tons. It was much smaller than its relative Tyrannosaurus Rex.

The first specimen discovered was a partial skull discovered in 1884 from an outcrop near the Red Deer River in Alberta, Canada, and was initially incorrectly assigned to the the species Dryptosaurus (also known at the tim as "Laelaps incrassatus") by Edward D. Cope. The name Albertosaurus was coined by Henry Fairfield Osborn, in a brief note in his 1905 paper describing Tyrannosaurus Rex.

About 30 fossil specimens of Albertosaurus have been found to date. This includes 22 individuals found at a single site, which is highly suggestive of pack behavior.

Finally, it is worth noting that some paleontologists have suggested that the Asian Tyrannosauroid, Alectrosaurus, may actually be a species of Albertosaurus.

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Anchiornis

Anchiornis was a small dinosaur that lived in China during the late Jurassic period, between about 160 and 155 million years ago.

Anchionris was very small, and had a total length of around 13 inches (34 centimeters). It is believed to have only weighed about 4 ounches (110 grams).

Both of the first two fossil specimens of Anchionris that were discovered show definite evidence of the animal having borne feathers. While the first specimen preserved only faint traces of these feathers, the second specimen discovered showed a much better impression of feathers, even with sufficient detail for scientists to study the number and location of individual feathers. As a result, scientists now know that Anchiornis had flight feathers on both its front and hind limbs. Additionally, we know that feet of Anchiornis (except the claws) were also covered with feathers, and that the head, neck, torso, and first part of the tail were covered wth downy feathers, and the rear of the tail bore tail feathers ("rectrices").

It has been suggested that the Anchiornis might have been able to fly or glide. The main reasons for this suggestion are that Anchiornis had a particularly bird-like wrist, and that it also had relatively long front limbs. Additionally, since Anchiornis had relatively short hind limbs, it does not seem to have been well adapted to a fast-running lifestyle.

Scientific Classification
Kingdom : Animalia
Phylum : Chordata
Class : Sauropsida
Superorder : Dinosauria
Order : Saurischia
Suborder : Theropoda
(unranked) : Coelurosauria
Infraorder : Deinonychosauria
Family : Troodontidae
Genus : Anchiornis

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Deinonychus Dinosaurs

Deinonychus meaning 'terrible claw' was a 7-10 foot long, carnivorous dromaeosaurid dinosaur species from the Early Cretaceous Period. Its name refers to the unusually large, sickle-shaped talon (on the second toe of each hind foot), which was probably held retracted while the dinosaur walked on the third and fourth toes. It was commonly thought that Deinonychus would kick with the sickle claw to slash at its prey but recent tests on reconstructions of similar Velociraptor talons suggest that the claw was used to stab, not slash. As in other dromaeosaurids, the tail was stiffened by a series of ossified tendons. This might have given Deinonychus greater balance and turning ability, and lends it its specific name, D. antirrhopus, which means 'counterbalancing'.

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Acanthopholis Dinosaurs

Pronunciation: a-kan-THOF-o-liss
Translation: Spine Bearer
Order: Ornithischia
Suborder: Thyreophora
Infraorder: Ankylosauria
Family: Nodosauridae
Height: 6 feet (1.8 meters)
Period: Early-Late Cretaceous
Description: Herbivore, Quadrupedal
Notes: Fragmentary remains were discovered in England. Because its remainsare distributed among several museums, it is difficult now to form an accuratepicture of its appearance. Acanthopholis was one of the armored dinosaurs.The shoulders and neck of its slender body were armed with spikes. Possiblytoo fragmentary to base the genus on.

Types of rabbits: Dwarf Hotot

The Dwarf Hotot, as the name implies, is compact and small, a docile, stocky little bunny. The rabbit's head is round, with a rather broad skull. Rabbit's neck should not be seen. Eyes are round, bright and bold. Ears are short, of good substance, and very well furred.

They should balance with the body and head. The body should be of uniform width from hips to shoulders, with well rounded hindquarters. There should be very slight gradual curve on the topline from the base of the ear to the highest spot over the hips.

It should fall in a curve to the base of the rabbit's tail. Ideal weight is 2 1/2 lbs, and maximum weight is 3 lbs., . Rabbit's fur should be dense, soft, fine with good luster. When stroked, the fur must be rolled back gently back into position. Color must be uniform and, except for eye bands, of pure white over the whole body. Rabbit's eyes are dark brown. Eyebands are must be narrow, well defined and of black color, forming an outline of the eye. It's color must be as dark and intense as possible. Eyeband width must be 2 pennies thick.

This breed was almost simultaneously created by two different German breeders in the 1970s.The breed first entered the United States in the early 1980s. These dwarf rabbits are affectionate and sweet. They tend to be of curious and playful personalities, and most of them are eager for your attention.They are very loving and make great children's pets.

White Lemuroid Possum

Bison bonasus

Rare breed

A rare breed is defined as a breed of livestock or poultry that is not common in modern agriculture, though it may have been in the past. Various national and international organizations, such as the UN Food and Agriculture Organization, the American Livestock Breeds Conservancy or the Rare Breeds Survival Trust of the United Kingdom, each define the exact parameters of what defines a rare breed. Many breeds that qualify as rare by these standards may only have a few thousand or even just a few hundred breeding individuals.


These organizations pursue conservation of heritage livestock and poultry for their unique traits, which can contribute to genetic diversity among animals important to human food supplies and economies, as well as general biodiversity and improvements in animal husbandry. The parallel of rare animal breeds are heirloom plants, which are rare cultivars.

STUDY SUPPORTS QUICK END OF DINOSAURS FROM ASTEROID IMPACT

Dinosaurs died quickly, snuffed out by the impact of an asteroid that sent a wall of fire and death racing across North America, an analysis of fossils found in Montana and North Dakota concludes. The finding casts doubt on a theory the dinosaurs died out slowly and that the asteroid impact was simply an end-the-misery trauma for an almost-vanished species, said Peter M. Sheehan of the Milwaukee Public Museum, first author of the study appearing Thursday in the journal Geology.

Researchers analyzed the number and distribution of fossils across large parts of the two states, where the animals roamed some 65 million years ago. "What we found suggests that the dinosaurs were thriving, that they were doing extremely well during that time," Sheehan said. "The asteroid impact bought a sudden and very abrupt demise to species that were healthy and doing well."

The research adds weight on one side of a debate among experts who study the dinosaur and how the huge animals died. One group, often called the gradualists, believes the dinosaurs were slowly dying out, that they were weak and beginning to disappear when the asteroid hit. William A. Clemens of the University of California, Berkeley, a leader of the gradualists, said the Sheehan study fails to prove the asteroid theory of dinosaur extinction. Sheehan and others believe it was the asteroid impact alone that killed the dinosaurs in one, swift fiery eruption, followed by weeks of deep cold.

The gradualists base their argument on a 20-year-old study that found few dinosaur fossils in the top 9 feet of a rock deposit, called the Hell Creek Formation, that was laid down in North Dakota and Montana during the last two million years before the asteroid impact. Based on the scarcity of fossils, the gradualists believe the 200-million-year reign of the terrible lizard was already drawing to a close when the asteroid arrived.

But Sheehan said a three-year survey of outcroppings of the Hell Creek Formation shows fossils throughout the deposit and that dinosaurs lived there in vigorous numbers and varieties until the very end.

"We looked at the community of dinosaurs in the Hell Creek formation and found they were not changing," Sheehan said. "If they were going through a gradual extinction, we would have expected to see some change. We found no evidence of a decline.'" Sheehan said that through the whole 180-foot depth of the Hell Creek formation, the species mix and numbers of dinosaurs were the same, with Tyrannosaurus as the most common carnivore and the Triceratops the most common plant eater. This was true, he said, right up to the 2 centimeter layer that marks the impact.

This layer, found virtually everywhere on Earth, is rich in iridium, a rare element brought to Earth by the asteroid. The iridium layer sits atop the Hell Creek formation. "The abundance of dinosaur fossils in the upper three meters of sediment immediately underlying the impact layer is well within the range of many intervals lower in the Hell Creek formation," the study says. After the impact layer, there are no dinosaur fossils.

To gather the data, scores of volunteers spent three summers combing more than 11 million square meters of North Dakota and Montana, walking shoulder-to-shoulder in a search for dinosaur fossils. They found the bones of almost a thousand dinosaurs sprinkled throughout the exposed levels of the Hell Creek formation. Clemens said that the weakness of the Sheehan study is that it fails to go back far enough in history. He said that deposits five million and six million years old contain a much richer variety and number of dinosaur fossils, suggesting the animals were declining when the Hell Creek formation was deposited. Clemens also said the Sheehan study does not consider the effect an asteroid extinction would have on other species. ``You need to consider the whole fauna,'' Clemens said. "Why did amphibians go through this period unaffected? There was a diversity of birds and they go through this period unaffected."

Early Carnivorous Dinosaurs Crossed Continents

Did the first dinosaurs wander across continents or stay put where they first evolved? The first dinosaurs evolved 230 million years ago when the continents were assembled into one landmass called Pangea. The question of early dinosaur movements remained unclear until the discovery of some exciting new dinosaurs fossils.

In the Dec. 11, 2009, issue of Science, a team of paleontologists presents the 213-million-year-old fossils of previously unknown carnivorous dinosaur Tawa hallae, including several of the best preserved dinosaur skeletons from the Triassic Period.

Fossil bones of Tawa, named after the Hopi word for the Puebloan sun god, were recovered from a dig site in northern New Mexico known as Hayden Quarry. The quarry is located on Ghost Ranch, where late painter Georgia O'Keefe once lived. Fossil bones of several individuals were recovered, but the type specimen is a nearly complete skeleton of a juvenile that stood about 28 inches (70 centimeters) tall at the hips and was approximately 6 feet (about 2 meters) long, from snout to tail. Its body was about the size of a large dog, but with a much longer tail.

Based on an analysis of the relationships among Tawa and other early dinosaurs, the researchers hypothesize that dinosaurs originated in a part of Pangea that is now South America, diverging into theropods (like Tyrannosaurus rex), sauropodomorphs (like Apatosaurus) and ornithischians (like Triceratops); and then dispersed more than 220 million years ago across parts of Pangea that later became separate continents.

"This new dinosaur Tawa hallae changes our understanding of the relationships of early dinosaurs, and provides fantastic insight into the evolution of the skeleton of the first carnivorous dinosaurs" said Randall Irmis of the Utah Museum of Natural History and University of Utah, a co-author of the study.

In addition to Irmis, authors of the study included lead author Sterling Nesbit of the University of Texas at Austin; Nathan Smith of the University of Chicago and the Field Museum of Natural History; Alan Turner of Stony Brook University; Alex Downs of the Ruth Hall Museum of Paleontology in Abiquiu, N.M.; and Mark Norell of the American Museum of Natural History.

"If you have continents splitting apart, you get isolation," said Nesbitt. "So when barriers develop, you would expect that multiple carnivorous dinosaurs in a region should represent a closely related endemic radiation. But that is what we don't see in early dinosaur evolution."

Instead, the research team found three distinct carnivorous dinosaurs – including the newly discovered Tawa – in the fossil-rich, Late Triassic beds they investigated at Ghost Ranch. "When we analyzed the evolutionary relationships of these dinosaurs, we discovered that they were only distantly related, and that each species had close relatives in South America," said Irmis. "This implies that each carnivorous dinosaur species descended from a separate lineage before arriving in [the part of Pangea that is now] North America, instead of all evolving from a local ancestor."

At Ghost Ranch, the researchers found fossils from a carnivorous dinosaur related to Coelophysis, common to that region, and fossils from a carnivore closely related to Herrerasaurus, which lived in South America. The 6.6- to 13-foot-long (2- to 4-meter-long) skeletons of Tawa display characteristics that exist in both species and features found in neither, implying a separate lineage.

"The discovery of multiple dinosaur species in one place that emigrated from elsewhere got us wondering whether other Late Triassic reptiles show similar patterns" said Irmis. "It turns out a variety of other reptile groups made multiple trips from the northern and southern continents [then parts of Pangea] and back again during the Late Triassic, including other dinosaurs."

Because so many different groups with different life modes were able to move freely across Pangea, the research team concluded that during the Late Triassic, there were no major physical barriers, such as large mountain ranges, to the movement of reptiles between parts of Pangea that later separated into distinct continents.

But this presented a paradox to the team: "We wondered: if reptiles, including dinosaurs, were able to freely move around Pangea during the Late Triassic, then why aren't there any sauropodomorph and ornithischian dinosaurs in North America during the Triassic?" said Irmis. "Our conclusion is that climate, possibly related to latitude, controlled the distributions of some reptile species."

"We think that all the major dinosaur groups had the ability to get to North America [part of Pangea] during the Late Triassic, and may have even passed through, but for some reason, only the carnivorous dinosaurs found the North American climate to be hospitable during this time," concluded Irmis.

The first Tawa fossils were discovered in 2004 by volunteers taking a paleontology seminar at the Ruth Hall Museum of Paleontology in New Mexico. Museum scientists invited the team of paleontologists to come and take a look.

"The specimens are unusual because they are so well preserved," said Irmis. "Because dinosaur bones are hollow, they are usually broken and crushed, but those of Tawa are nearly pristine."

Irmis and the rest of the team began a full-scale archaeology excavation in 2006 and have continued to unearth new material every summer since then. The fossil bone bed extends for tens of yards along a hillside, promising many years of potential significant finds.