In a late Cretaceous period 70 – 68 millions of years ago on territory of modern North America and Mongolia ( probably, in other areas of the world too ) lived duck billed dinosaurssaurolophus with small crest located at 45 degrees on the back of the head. They were herbivorous and were able to eat plants on ground level and up to 4 m above it; they moved on 2 and 4 legs; their maximal length was 12 m and maximal mass was 1.9 tons. Crest may had many functions : thermoregulation, gender determination and as basement of skin flaps, as modern basilisk lizards have.
Skull of saurolophus allowed to perform chew-like movements and grind food with large amount of teeth, which were replaced as they wear; on the sides of jaws they had cheeks, that helped them to keep food in mouth. Juvenile saurolophus had much smaller crests, then adults animals had, and it reached as they grow approximately 20% of a skull length. For the first time dinosaurs of this species were found in 1912 year by paleontologist Barnum Brown in Canada; also large amount of complete skeletons and their fragments were discovered in Gobi desert area in 1946 – 1949 years by expedition of Russian and Mongolian scientists, which later were described by Anatoly Rozhdestvenskiy.
Pterosaurs began their existence on the Earth in Triassic period, now it is not known for sure from which animals they evolved, presumably, from small carnivore dinosaurs; one of the earliest know flying reptiles is a eudimorphodon. Name of species means “True dimorpho teethed” or “Having two types of teeth“; at front sides of jaws they had fangs, at middle and back sides small teeth with 5 cusps, such teeth are specialized for hunting on fishes and insects. They differ animal very much from all later pterosaurs, so eudimorphodon is not their ancestor, but a spin off branch from main one. Their wingspan was 1 m, length was the same, mass was around 10 kg; they lived in late Triassic period around 210 – 200 millions of years ago.
For the first time eudimorphodon skeleton were found in Italy in 1973 by explorer Mario Pandolfi near Bergamo city. Maybe on ends of tails of animals diamond-shaped flap were located, like later rhamphorhynchus had, but for now there is no exact data. Teeth of eudimorphodons came into tight contact, when jaws closed, on some of them there are wearing and friction traces, which means, that they were able to chew food and not only ate it whole or in a large chunks. Currently a couple of animals skeletons were found at different locations of the world, including Greenland and Texas ( USA ), which makes them one of the most studied pterosaurs, initially found in Italy.
Among dinosaurs there were flying species, for example, rhamphorhynchus – toothy reptiles with long tail, vane from skin and hollow bones. They reached 1.26 m in length and 1.81 m in wingspan, wherein their mass was small, thanks to hollow bones. Rhamphorhynchus lived on Earth in Jurassic Period 170 – 140 millions of years ago; hunted on fishes and insects ( their forward-looking teeth were adapted for hunting on them ) and during flying held their heads parallel to the ground.
Rhamphorhynchus pterosaur
Currently there are no exact data on whether they were warm or cold blooded; soon after hatching from eggs they were able to fly and reached adult sizes by age of 2 – 3 years. They were able to live in nocturnal lifestyle, but there are also no exact information about this; they were hunted by other animals, for example, were found skeletons of flying reptile and large fish, which tangled in skin membranes of reptile, they drowned together and went to the bottom, where they were covered by the silt and preserved in such state for hundreds of millions of years up to ours days. Fossils of Rhamphorhynchus were found in Europe and Northern Africa, the most well-preserved and complete ones were found in BavariaGermany. Their skeletons were described for the first time in 1825 year by collector Georg Graf zu Münster and scientists Samuel Thomas von Soemmerring and Georg August Goldfuss.
One of the first discovered and scientifically described dinosaurs is an iguanodon, which was first described by fossilized teeth, that look like iguana‘s, but much larger, in 1820ies in England by Gideon Mantell. First it were reconstructed as massive animal, that looks like iguana with elephant size and spike on a nose, later findings showed, that spike located not on the nose, but on the hands of reptile, on a thumbs, and was used for protection from predators and food gathering. Also, findings showed, that iguanodons are not so massive and they were placed in upright vertical position, with basement on back paws and tile. Researches of 20th century made it clear, that this reconstruction is also not right, because at such position tile would be broken; and now animal is shown with horizontal body position and straight tile, which mainly moves on 4 legs and sometimes goes to running on 2 back paws.
Iguanodon drawing
Iguanodons reached 12 m in length and 3 tons mass; wherein their maximal running speed was 24 km/h on back limbs; they lived at the beginning of a Cretaceous period 140 – 120 millions of years ago. Animal ate plants, in mouths they had 2 rows of teeth, which replaced each other, with which they chewed food; teeth located deeply in mouths, this tells, that they had some kinds of cheeks : muscular or completely from skin. For now there are no undoubted data on whether these animals lived in large herds or in small families; adult animals preferred to move on all 4 legs, when they obtained size and weight ( by this time length of their arms reached 70% of the back legs length ), while light-weighted juveniles ran mostly on back paws ( their hands was only 60% of legs length ). By this time lots of iguanodons fossils were found in Europe, North America and presumably in Africa and Asia; many of the subspecies, initially placed in relation to iguanodons, now are moved into separate species, part of the others changed their location inside iguanodons genera. To date iguanodons are one of the most studied dinosaurs species and, together with megalosaurus and hylaeosaurus initially formed this genera of ancient reptiles.
Among hadrosauriddinosaurs, living on Earth in Mesozoic era, were Parasaurolophus – large herbivore animals 9.5 m in length and with 2.5 tons mass, which lived in areas, which currently form North America, in late Cretaceous period 76.5 – 66 millions of years ago. Their name means “before” or “near” “saurolophus” – another hadrosaurid dinosaur, and tells about their close relationship. Their notable feature is the crest, growing from the back of the head and reaching 90 cm in length; it was used for many purposes : loud sounds generation ( in support of this its hollowness speak, as well as adult’s animals brain orientation on hearing of high-pitch sounds, which their juveniles with smaller crests were producing ), thermoregulation ( crest was full of blood vessels and helped to warm up on Sun and cool in the shadow ) and gender and species identification. Parasaurolophus were able to move on 4 and 2 legs, probably, they ate grass on 4 legs and ran on 2 of them. They had large and strong bones, which helped them to carry large body mass and stay on 2 legs to reach high trees’ branches with large and juicy leafs.
She-parasaurolophus
Jaws of Parasaurolophus resembled beak of a duck; in a mouth they had lots of teeth, oriented for plants chewing and constantly replacing each other, as they wear off; between jaws there was semblance of checks, which helped to keep food in the mouth. Dinosaurs’ skin had scales of middle size without large formations; no complete skeletons of Parasaurolophus were found, only partially preserved on territory of USA, Canada and Mexico. Among their natural enemies there were large carnivore dinosaurs of that time, from which they protected themselves by living in large herds, signaling each other in case of danger and by fast running. First bones of this dinosaurs species were found in 1920 in Alberta, Canada, by scientists group from Toronto University; species was first described by William Parks in 1922.
Mosasaurs is a group of ancient marine reptiles, that was flourished at the end of Cretaceous period. They occupied free ecological niches after extinction of ichthyosaurs and reduction of plesiosaurs species amount. The smallest of them were 1 m in length and largest grew up to 18 meters; they were the biggest marine predators of their age and hunted on fishes, ammonites ( shelled mollusks ) and other marine reptiles. Their fossils are found around the world, including Antarctic.
Mosasaurs looked like modern day varanus, but were more adapted for marine life and their body was much more streamlined. Skull and lower jaws of mosasaurs were similar to snakes’ ones : they were able to swallow as whole large animals, as snakes do this. Legs of most of them transformed into fins and their tails had upper and lower fins, as sharks and ichthyosaurs had. They swam by moving their tails from side to side and rest of their body remained almost still. Mosasaurs did not laid eggs, like other reptiles : they developed viviparity instead, as ichthyosaurs and modern day dolphins and whales did. They had no gills, so they had to swim to water surface to make air breath. Their hunting tactics was ambush : mosasaurs waited for prey in the hide and made rapid swims to it, when it swam closer to them. Mosasaurs skin scales had diamond form, like snakes have; currently there is not much data about color of their skin, but, presumably, it was dark at the top and light at the bottom to camouflage them in not deep seas waters. Closer to the end of Cretaceous period and whole giant reptiles epoch there were new unique mosasaur species appeared : round toothed forms, that specialized on mollusks shells crushing; fresh-water crocodile alike forms; and very streamlined forms, that moved from ambushes tactics to active and fast swimming in Mesozoic seas. But all mosasaurs went extinct at the end of Cretaceous period, like dinosaurs, ammonites and large amount of other species of animals and plants did.
In Silurian and Devonian periods Earth was inhabited by placodermi ( from Greek words, that mean “plate skinned” ) fishes, their heads and necks and sometimes tail part was covered by bony armor plates. Most of them had no teeth and had only sharpened bony plates near their mouth. Most of them were seas bottom-dwellers, but there were giant carnivores among them, for example, dunkleosteus, which grew up to 11 meters in length and 4 tons in weight; these fishes ate other placodermi, mollusks and other marine animals ( dunkleosteus is thought to be first super-predator on Earth – predator, which hunted on other predators ). There were also plate-skinned fishes, which ate plankton, like modern day whales. In Silurian and Devonian periods placodermi inhabited most of ecological niches and that was their age in Earth’s history.
Plate-skinned fishes are first know organisms on Earth, that developed viviparity, and they are among the first animals, that had jaws. Many of fishes had bone plates rings in eyes, that protected them from damage and from high pressure of water. Their armor was adapted for protection and some species were so heavily armored, that their head looked like armored box with eyes. This shield was very heavy and most of placodermi lived near seas bottom, but there were also fishes with light and streamlined armors, that were able to swim at high speeds in paleozoic seas. First members of this family appeared on Earth at the beginning of Silurian period; at the end of Devonian period all placodermi were went extinct without leaving ancestors. Earlier it was thought, that this happened due to strong competition from bony fishes and first sharks, but new studies show, that they went extinct, due to ecological and climate changes, that were happened on Earth at the end of Devonian and beginning of Carboniferorus periods on Earth.
In the Mesozoic Eracrocodilomorphs lived on Earth; they had lots of simillarities with modern crocodiles, but their body was very adapted for marine life and looked like fishes’ one. Their tails had fins, some of them had limbs, that were transformed into fins, and their body was far more gidrodynamical, than body of modern days land and freshwater living crocodiles. Most of crocodilomorphs was fish hunters, but there were big species, that hunted on other marine reptiles; dakosaurus ( from Greek words, that “biting lizard” ) was one of them. Their teeth was flat and serrated, such form is not adapted for small fishes hunting and was adapted for hunting on big reptiles, that has comparable sizes to dakosaurus themselve. Many of the crocodilomorphs had grooves in skulls, in which salt glands resided. Salt glands is organ, that helps marine animals to remove from themselves excess of salts, that accumulates in them due to constant contact with salt water. For now there are no direct proves, that crocodilomorphs had exactly salt glands in these grooves, but their presence in them is the most probable assumption. Modern day crocodiles are adapted for ambushes tactics on hunting, but crocodilomorphs of mesozoic seas was far more active hunters : their fast body says about this and they had need to swim to surface for air breaths and there is no possibility to do this without leaving cover.
Dacosaurus maximus
In most of areas of mesozoic seas different species of crocodilomorphs lived on one territory and occupied different ecological niches. Their fossils are found in many countries of the world : in England, France, Switzerland, Germany, Polland, Russia, Argentine and Mexico. Crocodilomorphs was very adapted for living in seas and for now it is not clear whether they oviposited eggs on land or gave birth to already formed posterity. From one side : they were able to move on land on their fins, like turtles ( but their body made them vulnerable to big land carnivores and they were unable to hide in shell, like turtles ); from other side : they were able to develop viviparity, like their contemporaries ichthyosaurus and modern days whales and dolphins. So, untils nests and eggs of crocodilomorphs or evidences of viviparity of crocodilomorphs are found : this question is still open. Species was first described in 1856 year by paleontologist Friedrich August von Quenstedt.
Ichthyosaurus ( from Greek words fish and lizard ) are marine reptiles, that lived in Mesozoic Era, almost in all its time span 250 – 90 millions years ago. Ichthyosaurus reached in length 2 – 20 meters ( members of their family was the biggest marine reptiles, that lived on Earth to date ); their skin was scaleless; they were warm-blooded; and had very big eyes, this says, that ichthyosaurus hunted at night time or dived deep in Mesozoic seas. As all reptiles, they had lungs and had need to swim to surface to make air breathes. They were unable to lay eggs in seas and their body was not adapted for land walking, so they developed viviparity, like modern dolphins have. Ichthyosaurus are very similar to modern whales and dolphins in their shape and way of life, this is the result of convergent evolution, when animals of different species develop similar shapes and way of life in close living conditions. Ancestors of whales and dolphins made the same way, as ancestors of ichthyosaurus did 200 millions years before them.
Ichthyosaurus skeleton
For now no transitional forms between land reptiles and ichthyosaurus are found : the earliest of know already lived in seas. Previously it was thought, that they originated straight from amphibia, but later studies show, that they originated from reptiles, whose ancestors were amphibia. Ichthyosaurus was the most diverse in late Triassic Period, they occupied lots of ecological niches : from biggest marine predators to small fish hunters. In Jurassic their diversity was still high, but there were no such big species, like in previous period. Probably, this was caused by increased competition from sharks and first plesiosaurs. Previously it was thought, that in early Cretaceous Period amount of ichthyosaurus species abruptly decreased, but new studies show, that they were still diverse at that time. And only at the middle of Cretaceous they went extinct from Earth’s surface.
Ichthyosaurus
Ichthyosaurus had 4 limbs with big amount of phalanges, that were completely transformed into fins. Many species had back and tail fins, that were not present in any form in their ancestors – reptiles. Earlier scientists reconstructed ichthyosaurus without back and tail spins, because there are no bones, that support them. But later fossils were found, which contain prints of fins and animals were reconstructed from that time with these parts of bodies. Ichthyosaurus had circle of bone plates in each eye, that protected eyes from high pressure of deep waters. They had the biggest eyes from all vertebrates in both relative and absolute meanings. Their hearing was weakly developed, but smelling was advanced and, probably, they had some kind of bio electricity sensors on surface of their skin. Earlier it was thought, that their skin had colors, like modern dolphins have : dark on top and light at bottom to camouflage them closer to water surface; but new studies show, that they had dark pigment all around surface of their skin. This camouflaged them in deep waters and helped to perform thermoregulation. First fossilized bones of ichthyosaurus were found at the end of 18th century and during 19th and 20th centuries amount of found fossilized bones increased each year.
Allosaurus ( “strange dinosaur” ) are carnivorous dinosaurs from theropod family, they lived in Jurassic Period 155 – 145 millions years ago. They was named so, because their vertebrae was very different from vertebrae of other dinosaurs, that was know at that time. Allosaurus reached 11 – 12 m in length and 2,5 – 3 m in height ; their maximal weight was 1 – 2 tons. They were biggest predators of their time and hunted on plant-eating dinosaurs, like stegosaurus and iguanodons. Fossils of allosaurus were found in North America, Europe, Africa and Australia; in total there were found 60 fossilized skeletons of allosaurus. First almost complete skeleton of allosaurus was found by farmer M. P. Felch in 1883 year in Colorado, USA. Dinosaur was described first time by paleontologist O. C. Marsh in 1877 year.
Allosaurus Fragilis
They moved on their 2 legs, their forelegs was small and mainly used for hunting. They were able to run fast on their legs, despite their big size and weight, because there were found lots of allosaurus skeletons with ribs, that were broken during falls at high speed running. Also, their vertebrae had special holes, that allowed them to breath through skin at high physical exercise; modern birds also has such adaptations in their skeletons. Probably, allosaurus lived and hunted in groups, because there are lots of their fossilized footprints found together. Their brain was big relative to their body size; and allosaurus was able to perform social interactions and care about their youth. Their inner ear was relatively big and they was able to perceive low frequencies; but they had problems in perceiving high frequencies. Their smelling was developed to high level and they was able to use it for hunting and to determine other animals of their kind.
