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Reptile History
Dragon History


trexmuseumReptiles of the Past

There are many ways to study reptiles of the past. But as we are geared for children you will find our views are not like many other museums. We are not a collection of bones, we are a way of looking at things. We are about fun and edutainment and the wonder of a child's mind.

All dinosaurs are reptiles...
But all reptiles were not dinosaurs.

Click on the stamp to read about the dinosaur

trexmuseum Palaeosaniwa Ornithomimus Corythosaurus Daspletosaurus Einiosaurus Edmontonia Parasaurolophis Opisthias Goniopholis Allosaurus Stegosaurus Brachiosaurus Camarasaurus camptosaurus ceratosaurus


This medium sized carnivore measured around 20 feet long and weighed up to 1,200 pounds. We do not know its exact range but fossils or indications seem to place it in the Colorado, Wyoming, and Utah area during the Jurassic at 150 million years or so ago.

What is unusual about this dinosaur is that it had a distinctive horn and two bony ridges on its skull that gave it a very fierce appearance. Its name means "Horned reptile." We do not know the exact reason for these horns, but it is somewhat likely that they served as displays to impress the females and possibly acquire either a "harem" or better breading rights through prime territories or some such much like Elk do today. In the same unusual vein this ancient reptile also was the only meat eater to have some armor. The exact function of the smallish armored bumps is unknown and again may have been due to a selection process of the females of the species who may have simply "liked it."

Another unusual feature is that unlike the T rex with two fingers or the Allosaurus with three fingers the Ceratosaurus had four fingers. They do not appear to be strong enough for grasping or tearing so they likely had the same function that those of the T rex did.

The teeth were very sharp and the structure of the jaws tells us this species likely sliced off large sections of its victim and possibly let them bleed to death before feeding.

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This early member of the iguanodontids has only one recognized species from North America, Camptosaurus dispar. It reached lengths over 20 feet and maybe weighed up to 1 1/4 tons. Later relatives included the Iquanodon's and Hadrosaur's.

It is highly likely that this late Jurassic plant eater was a favorite prey of the carnivores like Allosaurus. It's name means "bent lizard" which is referring to the fact that the large thigh bone in the leg is curved in order to keep its legs further apart so that they could clear the wide rib cage. This dinosaur because of its anatomy and lifestyle probably spent most of its life walking on two legs. Its shape was rather bottom heavy but because of this the Camptosaurus was likely fairly maneuverable.

The teeth were much like grinders and likely preferred leafy vegetation which must have been retained in the cheek pouches until it was well chewed. They have often been found in the vicinity of Stegosaur and Camarasaur fossils so likely did not compete for food with them but liked the more sparsely available vegetation in this type of habitat so as not to compete with the much larger sauropods.


A close relative of the brachiosaurs and titanosaurs, this late Jurassic dinosaur was apparently quite common in North America and some areas of Europe and Africa. Never as big as its closest relatives this dinosaur was 50 to 60 feet in length and weighed 30 or 40 tons. Its name means "chambered lizard" which is referring to the hollowed chambers found in the vertebrae, most likely to cut down on weight.

This sauropod was very heavily built and its head looked a bit like a cross between a bulldog and a horse. Its teeth were very unique in that they looked like ivory spoons and this dinosaur was obviously adapted to eating hard and fibrous plant materials. It likely bit off large portions of trees and bushes and swallowed them hole. The stomach was adapted to grinding up these large bites with the aid of stones. One prominent paleontologist commented that the Camarasaurus should be likened to an elephant but with its head on the end of its trunk and its teeth in its stomach.

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One of the largest of all the sauropods was the Brachiosaurus. Who can forget that moment in Jurassic park when they first saw these magnificent creatures walk out of the water and stand up to browse from the top of a tall tree. The name means "arm lizard" which refers to the fact that its front legs or "arms" were longer than the rear legs. In size we find a true giant with lengths to 30 feet and weights of up to 80 ton with heads as tall as 50 feet above the ground.

Like many other large sauropods wherever weight could be saved it was. The head of brachiosaurs were very light weight and had many hollow areas throughout. This creature when full grow would have no competition for food and it is unlikely any carnivore or even a pack of carnivores would not even try and tackle this formidable plant eater.

The species were undoubtedly restricted to areas where tall trees grew in profusion. Fossil recorders from North America are scarce and no complete skeleton has ever been recovered. It is likely that its range was restricted to riverine areas of Utah and Colorado. A slightly more slender species has been found in some numbers in Africa.

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A late Jurassic reptile closely related to the dinosaurs with relatives still living today is the Goniopholis which means "angled scutes." This ancient crocodilian looked very much like many of the crocs found today.

Many people think only that various dinosaurs populate the Mesozoic, but this actually a great distortion. As far as numbers and species count most of the know ancient world was likely to be very much like today in terms of turtles, tortoises, frogs, lizards, crocodilians, and their prey which consisted of insects, salamanders, and even small dinosaurs. The big boys of the dinosaurian persuasion were truly awesome and terrifying, but they were a very small part of the total picture ecological.

Ancient crocodiles have been around as long as the dinosaurs and from their first beginnings about 235 million years ago as long legged running archosaurs they have evolved out into a myriad of forms.

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A Middle Jurassic to late Cretaceous dinosaur that almost everyone knows is the Stegosaurus who's name means "roof lizard" in mention of its plates running down its back that actually grew right out of its skin. In size we find a 20 to 30 foot length with body size similar to present day rhino's.

What a traumatic but fascinating scene in Walt Disney's Fantasia scene where the Stegesaurs gets killed to dramatic music by a Rex. Like its close relatives the ankylsaurs, this was a veritable tank when it came to defense. The plates on it's back likely served the function of both heating & cooling as well as protection. They were apparently covered only with skin and many blood vessels rather than the horny protection originally thought. Around its throat were a network of bony studs. And its sideways pointing spikes that were over 3 1/2 feet long served as a powerful deterrent to any would be predator and may have been used as displays of dominance or courtship for mate selection.

For food these ornithischians most likely cropped low growing vegetation and possibly reared up to get higher growth in trees. Likely they were like a high lawn mower in that they ate everything within their reach before moving in any other plane or direction. Their stomachs have been described as being "moving fermentation vats that gave off enormous amounts of heat. This may explain another use of its plates, "as heat exchangers."

There were actually two species of Stegosaurs found in North America and the Realm of the Rattlesnake. This is the smaller of the two called Stegosaurus stenops. The other was half again larger and called Stegosaurus ungulatus. There other species found in other parts of the world at different time periods and they were eventually replaced by their relatives the Ankylosaurs.

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Allosaurus was a very successful and abundant theropod dinosaur found through out the world from the middle Jurassic to late Cretaceous. In fact the largest carnivores ever found have been Allosaurs. In North America this ferocious hunter who's name means "different lizard" came in sizes between 30 and 40 feet in length and weighed 2 to 5 tons.

The fossils have been plentiful and South Dakota, Wyoming, Utah, Montana, New Mexico, and Oklahoma have all weighed in with some. One site in the Dinosaur Quarry from Utah contained 44 different individuals from babies to adults. This and other evidence suggests that these animals were highly social and possibly hunted in packs.

It is speculated that the habitats frequented by North American Allosaurs was similar the plains of Amboseli in Africa. These are hot with monsoons and dry periods every year. There would be lots of prey species and often herds would wander in search of water or foliage. this would prompt the carnivores to follow the game. Likely this also meant some established though seasonal home territories for the Allosaurs family, but the ability to seasonally follow their prey if necessary.

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One of the most unusual lizards left on this planet is the Tuatara of New Zeland. Opisthias is an ancestor of this true "living fossil" and likely looked very similar. The Sphenodon's are currently represented by only the Tuatara, but that was not always the case. These "lizard-like" reptiles are not true lizards but are in fact a side-path of evolution that started in the Middle Triassic and continue down to the one species left today. Some relatives took to the water and became known as the pleurosaurs. Others were very similar to today's living fossil, in fact the same basic body type and lifestyle has been running virtually unchanged for nearly 200 million years.

Opisthias was a late Jurassic reptile that likely lived on small creatures like insects, worms, and small lizards in a lifestyle similar to modern day New Zealand's last surviving member of the family.

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A member of the Nodosaurs (which lack tail clubs or spikes) the four ton and 20 plus feet Edmontonia, meaning near Edmonton, was the closest thing to invulnerable in the Pacific Northwest dinosaur enclave that existed in the late Cretaceous North America. With its flexible armor, long and sharp shoulder spikes, and a two layer boney head it would be surprising that these subgroup of the ankylosaur dinosaurs were often preyed upon.

Climate and habitat at this time favored certain species of dinosaurs over others. Temperatures were up about 75 million years ago as was humidity. There were peat bogs and bald cypress swamps. Just back from these areas and inland were much flatter areas composed of river systems flowing to the seas. Many feeder and tributary stream channels crisscrossed the region and greatly effected the many dinosaurs in the area. Nearly half the plants found in this region were flowering. Cycads, ferns, katura trees, fern trees, and many types of conifers dominated the flora. The lower and tough members of these plants were preferred by Edmontonia and they were also likely to favor more open scrub land closer to the sea. It would not have been all that usual for them to occasionally see an elasmosaur far up the rivers looking for a fishy meal.

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Among the strangest looking of the ceretopsian dinosaurs was the Einiosaurus meaning "buffalo lizard." This late Cretaceous horned dinosaur has only been found in Northern Montana and in fact may have been relatively rare and in an isolated population separated from its more common contemporaries such as Triceratops or Styracosaurus. Not much is known about this recently discovered dinosaur but it likely behaved as did most of the other horned dinosaurs.

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This coelurosaur, a likely ancestor of T rex, was truly a "frightful lizard." At 3 tons and over 30 feet in length this fast meat eating dinosaur was certainly the king of his late Cretaceous territory. In time Daspletosaurus was earlier than the rex but likely hunted the same prey in much the same manner. Another formidable carnivore at the same time and place was the somewhat more slender tyrannosaurid Albertosaurus. It is likely that little competition existed between these two species, much like lions and leopards coexist on the same African plain.

Like all tyrannosaurids this meat eating creature had only two arms, powerful jaws, and thick sharp teeth able take very large bites out of its prey. The size and depth of these bites may well have killed the victim from shear shock rather than actual attach trauma or blood loss.

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A close relative of monitor lizards Palaeosaniwa "before Saniwa" (another true lizard form the start of the mammals reign) was roughly the size of the more modern Komodo Dragon. This puts it in the 10 to 11 foot and 350 pound range. The varanoid lizards of the past included forms like the ocean going mosasaurus which grew to lengths up to nearly 50 feet and Estesia which is believed to be venomous and related to today's Gila Monsters. Some scientists believe that snakes evolved from varanids like Palaeosaniwa but currently there is debate on whether that is the case or not.

Monitor lizards are true opportunists. They will usually eat almost anything from worms and fish to mammals and carrion. Some like the Komodo are ambush hunters and some are simply opportunists that will eat literally anything that is edible and will fit in the mouth. It is very likely that Palaeosaniwa lived a lifestyle very much like today's more modern but not very much changed from their earlier ancestors.

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This hadrosaur from the late has a crest much like Grecian warriors and thus its name means "Corinthian helmet lizard." It is closely related to Iguanodon and is called a duckbill dinosaur because it had no teeth in the front of its mouth and instead had a horny duckbill look. The teeth started way back in the jaw which is highly unusual as plant eating dinosaurs as a whole just swallowed plants whole and let the stomach digest the mass. In addition these teeth were self sharpening and self renewing.

There has been a little debate as to how much time the duckbill dinosaurs spent walking on 2 legs versus all 4 and no real determination has been made. But the shape of the front feet indicate that they certainly could walk on all fours. There has also been much speculation on exactly what the high crest on the head was for. Modern research with catscan x rays seem to show that the hadrosaurs used these unusual shaped head ornaments to produce various sounds for either communicating or attracting mates or both. One can well imagine that several herds of different hadrosaurs may well have sounded like an unruly orchestra warming up with a clashing of different sounds. It was likely to either attract or drive of the meat eaters of the day depending on whether they were very hungry or music critics.

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Meaning "bird mimic" this extremely fleet ostrich dinosaur was about the size of or slightly larger than today's flightless ratite ostriches. At fifteen feet or so in length and over 300 pounds of speed these Cretaceous omnivores were perhaps the fastest family of dinosaurs ever seen on this planet. Close relatives were Struthiomimus, and who can forget that scene in the movie Jurassic Park where T rex grabbed the Gallimimus from ambush. This was a very good idea of how an ostrich dinosaur could become prey as they could easily outrun even the fast Tyrannosaurs.

Ornithomimus had a toothless jaw and what can only be described as a horny bird like beak. Because of their large brain size relative to other dinosaurs and their large eyes it is thought that they were among the most advanced dinosaurs ever to come onto the scene.

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Truly one of the most unusual looking of all dinosaurs this duckbill dinosaur's name means "like or beside Saurolophus" and was a member of the hadrosaur lambeosaurid family. Very few skeletons of this trombone crested late Cretaceous dinosaur have been found and it may have been much rarer than its more common cousins but was definitely in parts of Western Canada, Utah, and New Mexico. This plant eating Ornithopod ran on two legs but likely browsed on all four and was at least 33 feet long and a head crest of 5 to 6 feet that was possibly attached to the neck or back with a skin frill.

It is highly likely that the crests on all the hadrosaur family dinosaurs was used to sound alarms, troll for mates, and generally communicate with each other. It is thought that they were all very social animals and possibly migrated together in large herds for protection from the many hungry carnivores just waiting for an opportunity for a duckbill steak.

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More Extict Reptiles


The discovery of this small flesh eating dinosaur Troodon and its relatives was really a milestone in changing thinking about the behavior of dinosaurs. This fierce and intelligent hunter is pronounced Troo-o-don and its name means "wound tooth."

This fascinating carnivore was likely to be closely related in lifestyle to the more well known "raptors" and were more or less of the same size category or slightly smaller. They were likely to be ground-dwelling protobirds. Fossil remains are still limited and we will know more as more are discovered.

It is likely that they were fast, intelligent, pack hunters, and possibly nocturnal. The best approximation is that of a pack of small wolves. Remains suggest that they were social and raised their young in a family atmosphere. They had the sickle-clawed toes found in the velociraptors and likely lived a very similar life although they may have hunted different prey much like coexisting leopards and cheetahs.


It has been said that the herbivores and carnivores forced each other to evolve in a rapidly escalating battle of armor vs. firepower. If this is the case, and it seems very likely it is, then a very successful biological armored vehicle was Euoplocephalus.

Pronounced you-op-luh-SEF-uh-lus the name means "well protected head. This tank-like creature was from the late Cretaceous and is in the Ankylosaur family. It was believed to weigh in the 3 to 5 ton range and averaged 20 feet in length and maybe 8 or 9 feet in width.

What is unusual is that this heavily armored dinosaur was very likely totally immune to the attack of the large carnivores like T rex. It's strategy may well have been to first try and use it's bony and spiked tail to dissuade its attacker and then if that didn't work to simply hunker down in the sand or earth, protect its head and just out-wait its adversary. As a side note there have been T rex leg bones found that were fractured in just the manner that Euop would have done if it connected.

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