I recently paid my second visit to the exhibit Ultimate Dinosaurs at the Cincinnati Museum Center. This time I brought my camera. The exhibit crafted by the Royal Ontario Museum, features many recently discovered dinosaurs from Argentina, Africa and even one from Antarctica. It showcases the assembled casts of the largest predators known to walk the earth. It also features the story of continental drift, and how the super-continents slowly exploded during the age of dinosaurs creating new environments for separate species. The exhibit will be open until January 5, 2014.
I brought my two grand daughters who were four and five years old and around 42 inches high for scale. Subsequently, I returned without the kids. Photography was somewhat touch and go, but mostly successful. In order to dramatize the photos, and to remove confusing background of other dinosaur bones, I usually deleted the background unless it was relevant. On a couple of pictures, I pasted moons which I had previously photographed. While using my smudge tool to remove lights and door that intersected with the skeletons, I could imagine myself as a real paleontologist cleaning the host rock from real fossils.
Around 275 million years ago, during the Permian Period, a super-continent called Pangaea had over hundreds of millions of years become assembled from previous continents. At that time the land that would become New York City was near the equator, with the eastern United States and Spain huddled together with northwest Africa and South America spooning against south east Africa. At southwest Africa, Australia and Antarctica surrounded India, which had not yet met China. The first conifers appeared on land, and the Dimetrodon, a sail-backed precursor but not ancestor to the dinosaurs, lived in what is now Texas, Oklahoma and eastern Ohio. By the end of the Permian, an estimated 70% of the land flora and fauna plus 90% of sea life was extinct. Extensive volcanic activity in Siberia released carbon dioxide, hydrogen sulfide and methane. Previously a cool, dry time, the earth’s temperature reached 115 F on land and 105 on the surface of the sea.
Into this wounded world, the dinosaurs were born, the Triassic period of the Mesozoic era, some 251million years ago. Within the first 25 million years the seas had repopulated enough to support the great marine predators such as Ichthyosaurs and Plesiosaurs, and small dinosaurs walked the land. By 205 million years before present, the first known mammals found niches, but four million years later, aggressive volcanism may have driven 20% of sea families extinct, hearkening the Jurassic Period.
The Jurassic was the age of Dinosaurs, both large herbivores and powerful carnivores. One of the earliest, Cryophosaurus was discovered in Antarctica and dated at about 190 million years before present. The Massospondylus, found in South Africa lived at about that same time. (Both are part of this exhibit). It was a warm period with no polar ice, and Antarctica was somewhat north of its present position. Flying pterosaurs evolved, and by 150 million years ago, the first birds existed. With late Jurrasic, came the first wave of big sauropods including Apatosaurus, Diplodocus, and Brachiosaurus with Edmontosaurus and Stegasaurus providing meat for the Allosaurus.
At that time Pangaea began to split apart, Laurasia containing North America and Asia creeping north, and Gondwana comprising nearly everything else moving south, but Antarctica, India and Australia began to peel off of Africa. Near the end of the Jurassic, a large meteor impacted South Africa but the big one was yet to come.
The Cretaceous period marked the largest predators such as Tyrannosaurus of Laurasia, the Giganotosaurus of Gondwana (Argentina) and Spinosaurus of North Africa. It was a time of global warming when flowers and crocodiles first appeared. By 105 million years ago, Africa broke away from South America ending Gondwana, but T. rex lived on, and most of the dinosaurs from Argentina inhabited the late Cretaceous. By 67 million years ago, Africa had spun clockwise toward its present position, and India was cruising north leaving a wake of volcanic eruptions.
Two significant meteors left scars 70km (43.5 miles) and 85km (52.8 miles) in diameter during the Jurassic Period, and two more, slightly smaller ones hit during the Cretaceous, but 65.5 years before present, another meteor impacted the coast of Yucatan leaving a crater 170 km (105.6 miles) in diameter causing the estimated extinction of 80% to 90% of marine species and 85% of terrestrial species. It also left an iridium layer in sediments around the world to mark the demise of the dinosaurs.
The following is a list of specimens from oldest to most recent with a short summery of their characteristics. Some, are so recently discovered or rare, there is little information about them. I have included several specimens from the collections of the Cincinnati Museum Center which were on display to augment this exhibit, and an assembled Allosaurus which has been a on display at the museum previous to the current exhibit.
In the Late Triassic, 230 million years ago Prestosuchus walked like a crocodile with a body reaching 15 to 22 feet in length and long predatory teeth. It is considered an archosaur rather than a dinosaur and closer to a crocodile although not a direct ancestor.
Living in the swamps of what is now Brazil, it may have fed on smaller lizards amphibians and fish.
Eoraptor, was one of the earliest dinosaurs living in the late Triassic around 231.4 million years before present. It was found in Argentina. An omnivore, Eoraptor had both sharp serrated teeth in the upper jaws and leaf-shaped teeth in the lower. It ran on two legs and was about three feet long. The forearms which had five fingers, each with three long claws, were about half the length of the legs. Its long bones all had hollow shafts, and the vertebrae were also hollow.
In the same time period and location as Eoraptor, a larger carnivorous biped named Herrerasaurus reached as much as ten feet long and is thought to have weighed from 450 to 750 pounds. Skulls of this predator varied between one and two feet long.
Herrerasaurus had three extra pairs of openings in its skull besides the two for eyes and nostrils enabling the long head to be strong but less heavy on its vertebrae. The lower jaw also had these fenestrae. Its jaw had a flexible joint for grasping prey in its sharp serrated teeth. Puncture wounds in one Herrerasaurus skull suggest it may have been attacked by other predators like Saurosuchus or another Herrerasaurus. Samples of coprolites (fossil feces) prove it could digest bones.
The Simosuchus lived between 130 and 125 million years ago and was about four feet long weighing 10 to 20 pounds. Although thought to be crocodilian, it ate plants and walked on land. Its skull was short and muzzle blunted with leaf shaped teeth. Its body and legs were covered in boney armor, its tail short and not flattened. Simosuchus was discovered in the rich fossil beds of Madagascar.
To read more about this and other Madagascar fossils see:
A single partial skeleton 228 to 216.5 million years old, found in Late Triassic rock of Argentina, may be the oldest known ornithischian (bird hipped) dinosaur. The bipedal herbivore was called Pisanosaurus. At about three feet long and 15 pounds, its head was more ornithischian, but its body was more saurischian (lizard hipped). The exact classification is still undecided. It lived in a forested, volcanically active flood plane in a warm humid climate along with the two previously described dinosaurs, and may have been prey for the Herrerasaurus.
Also in the late Triassic, the Keichousaurus with a length of about 6 to 12 inches, was the smallest marine reptile found so far. Living in Mongolia and China, 245-210 million years before present, its five toed web feet may have allowed it to venture onto land. Of the family, pachypleurosauria, there is some speculation that it was an ancestor of the huge plesiosaurs that looked like sea serpents. This specimen was displayed by the Cincinnati Museum Center.
Massospodylus, lived in South Africa during the early Jurassic, about 200 to 183 million years ago, and was an herbivore or omnivore that walked on two legs. It grew from thirteen to twenty feet long and weighed 300 lbs. With a long neck and tail, its front limbs were about half the length of the back, each hand or foot had five digits, the thumb being the largest with a sickle-shaped claw, but the front limbs were not long enough to reach the mouth. The head was small for the body size with pointed teeth in the front and spade-shaped teeth in the back. As the teeth wore down they were replaced.
Clutches of eggs from the Massospodylus have been found containing six-inch long embryos. Some ten clutches were found with as many as 34 eggs per clutch near an area that had once been a lake. Most of the eggs in these clutches were arranged in rows. It is thought that a newly hatched Massospodylus walked on four legs, and since the near hatchling embryos had no teeth, they may have needed to be fed. For more info and pictures see:
Living 190 million years ago, Crylophosaurus was an early Jurassic theropod which displayed a curled crest of bone on its head. The length was estimated from the single known specimen at 21 feet and the weight at 1000 pounds. It was found in the mountains of Antarctica some 400 miles from the present South Pole but lived at a time when the continent was some 600 miles closer to the equator and the climate was temperate. Crylophosaurus was probably a predator and a scavenger. The theropod sub-order of dinosaurs walked on two feet and was usually carnivorous. One branch of theropods included ancestors of the birds.
Thriving in the western United States during late Jurassic Period was a saurapod called Camarasaurus. Because of the abundance of grouped specimens this four legged herbivore was thought to have lived as herds. Between 155 and 145 million years ago, it coexisted with bigger saurapods such as Diplodocus, Apatosaurus and Brachiosaurus. The Camarasaurus itself weighed as much as 51 tons and reached a length between 50 and 75 feet. Its box-like skull with a blunt snout held strong chisel shaped teeth, allowing it to eat tougher plants that would have been difficult for other saurapods such as diplodocus with weaker teeth. These 7.5 inch teeth were worn down and replaced about every two months. As with other sauropods many of the vertebrae were riddled with hollow passages containing a system of air sacs that connected to the lungs.
One Camarasaurus specimen found in Utah revealed gouge marks thought to be from an Allosaurus. A recent study of another specimen suggested a live Camarasaurus would have weighed almost 16 tons, reached sexual maturity after 20 years and died at 26 years. The Camarasaurus specimens photographed here came from the Cincinnati Museum Center specimens which augmented the larger traveling exhibit from the Royal Ontario Museum.
Between 154 and 150 million years before present, near the end of the Jurassic Period, the massive herbivore, Diplodocus roamed what is now western North America. At 115 feet long and 11 to 17.6 tons, it is no longer considered the biggest dinosaur, but was apparently large enough to intimidate its contemporary Allosaurus. The 20 foot long neck is now thought to have held its small head and smaller brain at a low angle rather than the vertical one previously depicted on murals and toys. Its body was more slender than most sauropods. The front legs of the Diplodocus were shorter than the back, an opposite arrangement from the Brachiosaurus, but its large shoulders made the posture of its back nearly horizontal. The hand and finger bones were combined into a column except one detached claw bearing digit of unknown purpose. The Apatosaurus was a member of the Diplodocidae family which while only 75 feet long, is thought to have weighed between 18 and 39 tons, while the Brachiosaurus was 85 feet long and weighed an estimated 31 to 48 tons. All three of these sauropods, as well as the previously described Camarasaurus lived in western North America, during the late Jurrasic Period.
It is thought the Diplodocus may have used the forward tilting, elliptical rod-shaped teeth found in the back of the jaws to strip leaves from low hanging branches but not treetops, although by rearing up on hind legs and tail it could have reached as high as 33 feet. Another proposal is that despite a consensus it was not semi-aquatic, it may have stood on riverbanks feeding on aquatic plants, as well as ferns and bushes. A computer model depicted the Diplodocus as having a resting posture with the neck at 45 degrees and the head hanging downward. Each tooth was continually replaced within 35 days, each socket containing five replacement teeth in the process of developing. Recent bone histology studies suggest the Diplodocus grew quickly maturing to reproductive ability in about ten years. The specimens for illustration came from the collection of the Cincinnati Museum Center displayed to augment the present exhibit of the R.O.M.
Around 155 to 150 million years ago, in the late Jurassic period, the Allosaurus spread throughout the landmass that would become the western United States from Montana to New Mexico. This powerful two-legged predator averaged 28 feet in length and may have reached almost forty feet long. Although this dinosaur was not part of the exhibit, a full assembly can be seen in another part of the museum and it seemed important to compare with other predators in the exhibit.
The Allosaurus is estimated to have weighed from a ton and a half to more than two tons, but could move at speeds from 19 and 34 miles per hour. Vertebrae of the neck and upper back were hollow, and have been compared to birds suggesting they contained air sacks for respiration. Its three fingered forearms were relatively small but strong enough for grabbing and holding prey.
The head was almost three feet long with five teeth each on the upper and lower tip of the snout followed by about 16 more each in the upper and lower jaws. These teeth were serrated and were replaced as they were torn out. The teeth were suited for slicing, and one theory depicts it driving its upper teeth into large prey and pulling away chunks thereby grabbing a meal while only wounding an animal. Another depiction has it grabbing the neck of an ornithopod in a strangle hold. The bite of an Allosaurus has been estimated as less strong than an alligator or lion, capable of slashing flesh but not crushing bones. By the way the head is attached to the spine, it is thought the Allosaurus unlike most theropods, may have been able to tilt its head downward using it to pull flesh apart with upward movements while holding the victim with a foot like some modern birds of prey.
Evidence that Allosaurus preyed on Stegasaurus herbivores was discovered in a tail- spike puncture wound on an Allosaurus and a bite mark on a Stegosaurus neck plate matching that of an Allosaurus. Suggestions that Allosaurus hunted in packs is circumstantial and controversial. It may be that individuals competed for the same prey and fought over the kills. Teeth marks on the skulls of individuals made by other of the same species could be evidence of territorial disputes or fights over dominance within a pack. Stress fractures in about six percent of forearms and foot bones examined as well as fractured ribs, humerus and radius, an amputated foot bone and in one individual fourteen separate injuries, suggest that for this top predator, life was still hard.
The Archaeopterx is almost as famous as the Allosaurus. While not the first bird or birdlike dinosaur, it was the first feathered dinosaur specimen discovered. First found in Germany in late Jurassic strata, it lived from 150.8 to 148.5 million years ago. Older avian dinosaurs have since been found in China and the Gobi desert. Archaeopterx was about 1.8 feet long and around 2.2 pounds, around the size of a raven. According to a scanning electron microscope at least one of its feathers was black. The advanced feathers are considered flight feathers, although its lack bone mobility may have denied it upward flapping and strong flight. Besides feathers it had a wishbone and wings like birds, but like a theropod had teeth, three fingered claws and a boney tail. It has been compared to a Rahonavis and like that species, the Archaeopterx may have been a side branch on the limb that reaches from dinosaur and birds. The cast on display is from the collection of the Cincinnati Museum Center.
The Amargasaurus lived 130 to 125 million years ago in Argentina during the early Cretaceous. It had a double row of large spines down its nearly eight foot long neck which would have protected this otherwise most vulnerable spot. An herbivore, it was about thirty feet in length and weighed more than two tons. A sauropod, it had a horse-shaped head with nostrils behind the eyes. Sauropods generally walked on four legs, had long necks and tails and included some of the largest land dinosaurs such as Apatosaurus and Diplodocus.
Some 125 to 115 million years ago, in the early Cretaceous a four legged herbivore of the tianosaurid sauropods called Malawisaurus roamed what is now Malawi, in eastern Africa. It was 40 to fifty feet long and weighed 10 to 15 tons and may have been armored with hardened bumps along its sides and back.
Some 20 million years after the extinction of this sauropod, titanosaurs would reach much greater sizes such as that of the Argentinosaurus and Saltasaurus which also had boney armor, both found in South America. Still another titanosaur which was about half the size of the Malawisaurus would be discovered in Madagascar dating to near the end of the Cretaceous, about 70 million years ago. (See Below.)
Suchomimus means (“crocodile mimic”) for the mouth which resembles a crocodile. It lived in the Cretaceous period, 121–112 million years before present, in Niger, Africa when the Sahara Desert was a swamp. Like the later, larger Spinosaurus it had spine extensions although much shorter and farther back on its hips than its distant cousin.
The only discovered fossils represent about a third of a Suchomimus which is not considered fully grown but has an estimated length of 36 feet and weight between three and six tons. Its long narrow snout contained about 130 teeth with 28 of the longer teeth embedded in an enlarged tip of the snout. Its teeth were curved slightly backward but unlike the Spinosaurus were finely serrated. Like Tyrannosaurus, it had a boney secondary palate which reinforced its skull from the twisting struggles of prey. The body had strong forearms ending in sickle-clawed thumbs. It may have fed on large fish, moderately sized land animals and carrion. Smaller and older species related to Suchomimus have been found in England, and Brazil.
Living in mid-Cretaceous Africa, from 115 to 105 million years ago, Nigersaurus was about 30 feet long with a neck extending six or seven feet from the body, but not long enough to suggest it was a tree browser. Studies indicate it habitually bowed its head grazing on ground plants such as ferns. The jaws of this sauropod were wider than its skull with all its teeth in front. Because it continually replaced teeth about every two weeks, the active and replacement teeth totaled some 500 teeth in its jaws at any one time.
The Nigersaurus, like many dinosaurs had openings in the skull bone called fenestrae. These holes were allowed for a lighter skull without compromised strength, the same way that structural beams in cars and planes often have designed openings. The openings are also useful for paleontologists for identifying and classifying dinosaurs. The skull of the Nigersaurus was unusually delicate with five more fenestrae than other sauropodomorphs. Likewise, the vertebrae between the head and hips were hollow containing air sacks which also conserved weight, a characteristic discovered in a variety of dinosaurs.
A contender for largest predator is Spinosaurus, named for its long vertebral spines which may have supported a sail-like display or hump. Also from the Cretaceous 112 to 97 million years ago, it was first found in Egypt and Morroco. Although only three skulls have been studied to date, the length of the head is considered to have been as much as 5.7 feet with total length of the body reaching 49 feet. Estimates of its weight vary from four to 23 tons. Although the Spinosaurus is not part of this exhibit, the CMC has displayed some examples of its teeth, and a smaller member of its family, the previously mentioned Suchomimus has been fully assembled.
The Ouranosaurus lived about 110 million years before the present in Niger Africa. It was an ornithopod with a flat beak and two sets of grinding teeth on the sides of its mouth which would have enabled it to eat leaves fruit or seeds. Gaps between teeth were filled with points of replacement teeth. Between each eye and the nasal passage was a low bump. The most prominent feature of the Ouranosaurus was a set of flat vertical protrusions along its spine that may have supported a sail-like display or hump. Its front limbs were nearly as long as the back, and the front feet hoof-like allowing two or four legged locomotion.
It was about 25 feet in length and weighed between two and four tons. An ornithopod (meaning bird footed) generally walked on two feet with three toes each, although some had four digits and some were able to walk on four feet in grazing position or stand to feed on trees. They were herbivores with horny beaks in the front of their mouths, most notably the so called duck-bills.
The Giganotosaurus, lived 100 to 97 million years ago, and was a predator that has been compared to the iconic Tyrannosaurus Rex. The Giganotosaurus, also a theropod, weighed somewhere between seven and fifteen tons with a skull more than five feet long, and a body as long as 43 feet. Its maximum speed is estimated at 31 mph before becoming too instable to keep afoot. Despite having a head at about the same size as a Tyrannosaurus, its bite strength is estimated at about one third of the T. rex, the lower jaw of the Giganotosaurus being more suitable for slicing wounds. It is distantly within the lineage of Allosaurus. Since the Giganotosaurus was only discovered in 1995, other larger or more perfect specimens may yet reveal new data.
Living 100 to 93 million years before present in Middle Cretaceous North Africa, the Carcharodontosaurus was a fearsome carnivore slightly larger than a T. rex and smaller than a Giganotosaurus which was its contemporary and relative. The skull of a Carcharodontosaurus, was measured at 5.2 feet long, about a foot less than the Giganno. Giganotosaurus.
Buitreraptor which lived in Argentina some 94 million years ago was the size of a rooster. With an elongated head sporting numerous teeth, it extended nearly five feet from its nose to the tip of the tail. The forelimbs were long, ending in three fingers each. Although no feathers were found preserved with the Buitreraptor, they discovered on other closely related species, suggesting it may have displayed some feathers.
The Argentinosaurus lived in the late-Cretaceous between 96 and 94 million years ago. From the few fossil parts recovered, some vertebrae, a partial femur and a tibia, estimates have been made of its size at about a hundred feet long and weighing as much as a hundred tons and could have walked five miles an hour without putting destructive stress on its joints. One of the vertebrae was more than five feet high and the tibia two inches shorter. The reconstruction of the tibia and femur were shown in this exhibit as well as a vertebra. Argentinotosaurus was a titanosaur sauropod.
Futalognkosaurus lived around 87 million years ago in the Patagonian region of Argentina when the climate was warm. Another titanosaur, it was thought to be between 85 and 111 feet long with a hip width of ten feet. Three fossil specimens allow a study of 70% of the entire skeleton, but a complete assembly would have been difficult for travel.
Carnotaurus was a late-Cretaceous predator (72-70 million years before present), named for the bull-like horns protruding obliquely from its skull. In addition to the horns, a deep skull and thick neck muscles suggest it may have engaged in rival head butting. The forearms were even shorter in proportion than those of a Tyrannosaurus, and the arms may have even been functionless, but studies show this thirty foot long carnivore was capable of quick, very strong bites for large prey, and a hinged jaw allowing it to swallow small prey whole. Its two-foot long skull contained long slender teeth. Its eyes were small and somewhat binocular. It was also a fast runner but may have had trouble making sharp turns.
The skin of a Carnotaurus left an impression in the mud where it died. A pattern of small, polygonal, non-overlapping scales was divided by parallel grooves. Rows of bumps also ran along the sides of the neck, body and tail. No evidence of feathers was noted.
Rahonavis, a small predatory theropod, was discovered among fossils on Madagascar of the late Cretaceous Period some 70 million years old. Whether it flew or was related to modern birds, as the name suggests is disputed. The raised sickle-like claw on its second toe has persuaded some that is a kin to Buitrerapter, while others believe it may be related to the classic Archaeopteryx. The only specimen of Rahonavis was 2.3 feet long about the size of a modern raven and a little larger than the Archaeopteryx. Evidence of quill knobs on the ulna, a pelvis with adaptations for flight similar to Archaeopteryx and larger more powerful wings than Archaeopteryx, as well as shoulder bones with ligament attachments that could have allowed flapping of wings suggest possibility of flight, which may have been obtained independent of other lineages. Other skeletal evidence points to the dromaeosaurid (raptor) family. A recent citing depicted a bat like stroke similar to a Microrapter, a feathered dinosaur of the early Cretaceous period found in China.
The late Cretaceous Austroraptor, some 70 million years ago, attained the length of 16 feet and had short forearms. The elongated skull reached 2.6 feet in length. It was a bipedal predator with cone shaped teeth and thought to be closely related to the earlier Buitreraptor, both of which were found in Argentina.
The Saltasaurus, was a sauropod and titanosaur that lived in late Cretaceous Argentina, 70 million years ago. It was some 39 feet long and weighed approximately eight tons. A plant eater, it had blunt teeth only in the front of its mouth. Like many sauropods, it didn’t chew its food, allowing it to pack more into its long digestive track. It had bony plates, four to five inches in diameter embedded in its skin similar to those of Ankylosaurus, although not related to that dinosaur. An extensive nesting site was discovered in Patagonia where several hundred Saltasaurus females created holes with there hind legs, laid some 25 eggs in each hole and buried them beneath soil and leaves. The eggs, like the one at this exhibit, were four to five inches in diameter. Fossil embryos were discovered in the eggs with skin impressions that displayed armor and bead-like scales.
First discovered in 2001 in Madagascar, the Masiakasaurus (vicious lizard) had a body length of about seven feet. Its teeth were spoon shaped with hooks, and in front slanted outward as if for catching fish or scavenging. The back teeth were adapted for cutting and slicing. It may have also fed on small vertebrates, invertebrates and fruit. The Masiakasaurus had hollowed neck vertebrae with air filled sacks as with the Nigersaurus, and had air cavities in the brain case as well. It lived about 70 million years before present.
Sometime before 70 million years ago a group of somewhat small titanosaurid sauropods made their way across land bridges from South America to Africa all the way to Madagascar. A single juvenile was excavated nearly intact, the first titanosaur to be found with a complete skull. At 26 feet in length it was estimated to be as heavy as an elephant. It was called Rapetosaurus and thought to reach the length of 49 feet as an adult, still small for a titanosaur. The skull, long and low with nostrils on top resembles that of a Diplodicus which had gone extinct at the end of the Jurassic, 80 million years previously. Rapetosaurus would also go extinct only 5 million years later at the end of the Cretaceous. The study of this skeleton has led paleontologists to believe the titanosaurs were most closely related to the brachiosaurids.
The predator Majungasaurus was also found in northwest Madagascar and lived in the same place and time frame as Rapetosaurus, on which it probably fed. It could reach 26 feet in length and may have weighed more than a ton. It was an abelisaurid, and like those theropods had a blunt nozzle on a short skull which was about 26 inches long and wider than most abelisaurids. This skull was textured with bony bumps, a thickened ridge between nostrils and a domelike horn atop the head. Sinus passages ran beneath the nasal ridge and horn. These extrusions are thought to have been covered by keratin or some other protective coating. The mouth contained 17 short-crowned teeth in both the upper and lower jaw.
The skeleton, resembling its close relative the Carnotaurus, suggests a strong neck and legs with probably useless forearms bearing fused fingers and no claws. The short, thick legs were supported by fused ankle bones and three short toes with one smaller digit that didn’t touch the ground. The Majungasaurus is thought to have attacked prey with a death grip like big cats or bulldogs as implied by its short face, thick skull strong vertebrae and sturdy teeth. Its tooth marks have been found on Rapetosaurus suggesting a struggle like that depicted in the exhibit. Such tooth marks found on other Majungasaurus specimens suggest competition, scavenging and or canabalism.
Thanks to CT scans, it was discovered that most of the vertebrae, and some ribs were hollowed, implying air sacks that provided a flow through respiration similar to some birds. This form of respiration would allow air to travel in a single direction so that fresh air and exhaled air didn’t mix.
Near the end of the late Cretaceous, 73 to 65 million years ago, the Edmontosaurus became one of the most numerous dinosaurs to populate North America from Colorado to Alaska and Alberta, Canada. One site alone is thought to have the scattered remains of more than 10,000 Edmontosaurs. This and other multiple groupings of these fossils suggest that they gathered in herds. There is disagreement as to whether they migrated to avoid northern winters. A hadrasaurid (duck bill) dinosaur, the Edmontosaurs walked on all four legs, could stand and possibly run on two legs. Reaching a length of 39 feet and weight of more than four tons, this herbivore was one of the largest hadrosaurids and one of the few that did not have a boney crest. Unlike early depictions it is not likely to have fed on water plants or to have been suited for swimming.
The skull was between three and four feet long with spoon-shaped keratinous bills that had no teeth. In the back of the mouth replicable teeth grew in columns along cheeks and the jaws. It is thought to have used its bill to strip leaves from bushes and trees, and may have also consumed horsetails and gymnosperms.
Tooth marks and damaged tail and back vertebrae on one specimen suggest an attack by a T. rex which is found in the same strata as the Edmontosaurs. Another specimen shows tooth marks from a smaller predator.
One of the final predatory dinosaurs before the mass extinction, the Tyrannosaurus rex lived around 67 to 66 million years ago near the end of the Cretaceous. Weighing an estimated average of 7.5 tons and standing 13 feet tall at the hips, it was as much as forty feet long. The old walking tripod posture of black & white movies and plastic figures has now been replaced by a racing bicyclist posture with a forward thrust head balanced by an extended tail, both parallel to the ground.
The power of those famous jaws is more wondrous than legend, having an estimated bite three times greater than a great white shark and seven times that of an Allosaurus.
The neck was slightly s-shaped like other theropods but more massive to support the huge head. The skull, measuring up to five feet long, contained large fenestrae, openings in the bone to reduce the weight and support muscle attachment, as did the jawbones. Parts of the skull were honeycombed with small holes containing air also to reduce weight. The disproportionately small forearms with two clawed fingers and a stub each have been called vestigial, but other studies propose that while little more than three feet long, they might have been able to lift more than 400 pounds each and were probably used to grasp struggling prey.
To facilitate the powerful jaws the skull was thick and some of its bones were fused. The palate inside its mouth was boney. The snout was narrow but the back of the skull was wide. The front teeth were chisel-like curving backwards to prevent loss of prey, made for gripping and pulling and scraping meat from bone. The side teeth were for puncture while the back ones were for slicing. Their banana shape was to grip struggling prey without breaking. The longest were in the upper jaw and rear lower jaw, as long as 12 inches including the substantial root so that only four inches were exposed. Its teeth were bone crushers. One was found embedded in an Edmontosaurus fossil, and others of that species as well as Triceratops bore its teeth marks.
Various studies put the T. rex somewhere between birds and reptiles, but probably closer to birds. Fossilized impressions of some patches of scales were found from a Tyrannosaurus in Montana, but similar species such as Yutyrannus and others from China preserved feathers. Studies showing relatively fast growth rates and others comparing oxygen isotopes suggest that the T. rex was either warm blooded or able to maintain core temperatures by sheer size.
Speculation on land speed has yielded wide estimates from 43 to 11 mph. Evidence of hollow bones that would have reduced the weight of an adult Tyrannosaurus to five tons and very strong leg muscles support arguments for increased speed. Although ratio of length between the thigh bone and shin bone indicates slower movement, the long skinny feet may have compensated for the shorter tibia. Most recent studies and computer models suggest speeds lower than 25 miles per hour, which may be irrelevant unless it is chasing you. Even 11 mph is likely faster than most prey of the T. rex such as Triceratops. In attacking such animals it would need to make a quick deadly bite from behind to paralyze, choke or eviscerate.
A Tyrannosaurus skull reconstructed in 2006 measured 59 inches. Tyrannosaurus has had over a hundred years of study, numerous specimens and more than thirty skeletons found from New Mexico into Canada, as well as similar species in Asia. With this widespread and deeply probed knowledge, numerous debates and differences of opinion have sparked over possible weight, running speed, use of forearms warm or cold blooded, bird or reptile, skin or feathers, predator or scavenger.
Like many predators Tyrannosaurus had front facing eyes indicating a keen depth perception, and studies of the skull and brain casing support a vision that allowed it to see 13 times better than a human. Large olfactory bulbs also are evidence of a sense of smell greater than most other non-avian dinosaurs, comparable to a modern vulture. The long cochlea of its ear implies sensitive hearing particularly in low frequencies. The brain to body size was three times that of other dinosaurs near its size.
Evidence based on the large brain size and groups of T. rex fossilized together has led to controversial speculation that they may have hunted in packs. Another scenario imagines a Tyrannosaurus using a cow-tipping strategy on a Triceratops which would have immobilized it allowing access to the underbelly. The study concluded that a Tyrannosaurus moving at a speed of 17 mph could have head-butted the Triceratops onto its side within a few seconds.
Recent discoveries suggest soft tissue preserved in Tyrannosaurus fossils is collagen. For more information see:
Although the history of the dinosaurs is literally written in stone, we have still only discovered a few of those sedimentary pages, so the facts that should seem obvious, are often estimates and subject to revision. Sometimes fossils are found with species entangled in a bone pile causing a mix up called a chimera, where one species or more is mistakenly placed with another. The date of the animal’s existence on earth is subject to revision due to new discoveries in more widespread places, older and more recent strata. Length of an animal is sometimes a matter of conjecture due to missing tail vertebrae or other bones. Weight is almost always debatable, as calculated from head size, bone mass and other factors. When bones are missing, estimates are usually completed using other closely related species.
In trying to find the head length of the Spinosaurus reputed to be the largest walking carnivore, I ran into many dead ends, but finally came upon a on the web site called Prehistoric Wildlife. There, scaled drawing which is probably highly approximate, showed the head length at three meters. The details on that site are highly informative and well worth reading. The same site showed the head of Suchomimus as two meters:
Large Sauropods Mentioned in this Text
Estimated Lengths Weights Ages *
Camarasaurus: 50 to 75 ft 20 to 25 tons 155 to 145 MYA
Diplodicus: 115 ft 11 to 16 tons 154 to 150 MYA
Apatosaurus: 75 ft 18 to 40 tons 154 to 150 MYA
Brachiosaurus: 85 ft 31 to 48 tons 154 to 153 MYA
Amargasaurus 33 ft 2.0 to 4.0 tons 130 to 125 MYA
Nigersaurus 30 ft 5.0 tons 119 to 99 MYA
Argentinosaurus 115 –130 ft 80 to 110 tons 97 to 94 MYA
Futalognkosaurus 105 -111 ft 50 to 75 tons 87 MYA
Saltosaurus 39 ft 8 tons 70 MYA
Rapetosaurus 49 ft 20 to 30 tons 70 to 66 MYA
* From Smithsonian.com:
“Contrary to what you might expect given their skeletal sturdiness, the biggest sauropods are often found as partial skeletons. Our knowledge of Argentinosaurus, Puertasaurus, Supersaurus, Diplodocus hallorum and other giants is frustratingly incomplete, and figuring out how large they truly were relies on estimation from more complete representatives of other species.
The lack of complete tails from these dinosaurs makes the matter even more problematic. Dinosaur tails varied in length from individual to individual, and different subgroups had proportionally longer or shorter tails. In the case of Diplodocus hallorum, for example, a great deal of the dinosaur’s estimated 100-foot-plus length comes from the fact that other Diplodocus species had very long, tapering tails.
We don’t really know how long Futalognkosaurus was because, with the exception of a single vertebra, the dinosaur’s tail is entirely missing. Nevertheless, the sauropod that Calvo and coauthors described is remarkable for encompassing the entire neck, back and associated ribs, and the majority of the hips. Together, these elements represent over half the skeleton and comprise the most complete giant sauropod individual yet known.”
For more general information about dinosaurs:
For the USGS animation on continental drift see:
For the Cincinnati Museum Center: