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Mesozoic
The Mesozoic era began 251 mya ago, right after the Permian mass extinction. It's divided into three periods - Triassic, Jurassic and Cretaceous. Mesozoic is usually refered as the "Age of the Reptiles", though it's more accurate to say it was the "Age of the Archosaurs".
Archosauria is group of diapsid amniotes that dominated Mesozoic terrestrial (and some aquatic) ecosystems, and is still playing important role in today's ecosystems. There are two main lineages, or branches, of archosaurs - crocodilian one and bird one. The croc-line archosaurs include modern crocodiles and alligators, along with their numerous extinct relatives, while the bird-line is represented by two major groups - the pterosaurs and the dinosaurs. The birds evolved sometime during the middle Jurassic, as a group of derived coelurosaurian theropod dinosaurs - the Avialae (or Aves, if you like). Although dinosaurs first appeared toward the end of the middle Triassic, they were not major part of the ecocsystems up until the Triassic-Jurassic boundary, when a mass extinction wiped out the dominant until then croc-line archosaurs. Since Jurassic times, dinosaurs are the most numerous group of tetrapod animals.
Besides the archosaurs, there were many other group of animals living through the Mesozoic. Many groups of marine sauropsids lived in mesozoic seas and oceans - nothosaurs, placoderms, ichthyosaurs, plesiosaurs and mosasaurs among others. Invertebrate animals also flourished - countless species of ammonites, belemnites, bivalves, gastropods, echinoids, brachiopods, foraminifers, etc., evolved during this era. On land first mammals appeared. The plant life went through serious changes in the early Cretaceous, when flowering plants evolved. This led to co-evolution of many new insects, like butterflies and bees, whos way of life was tightly connected to the new plants.
During the Triassic there was one supercontinent - Pangaea. The climates were warm and arid. Big parts of Pangaea were deserts where life hardly managed to survive. There were no ice caps on the poles, but the sea levels were the lowest since the Precambrian. The oxygen levels were also pretty low, an aftermath of the cataclysms that marked the end of the Paleozoic era.
In the next period, the Jurassic, conditions on Earth stabilized. The climates were warm and the temperature gradient towards the poles was more gradual than today's. Also overal climates were moister than those in the Triassic. Sea levels rised, so did the oxygen levels. Plant life in different latitudes was more uniform than it's today. With the onset of the Jurassic, Pangaea started to break up. This led to the forming of two major continental masses - the northern Laurassia and the southern Gondwana. In middle Jurassic times the North Atlantic ocean started to open. Eastern from the newly forming Atlantic was the mesozoic Tethys ocean - a complex system of ocean and sea basins that existed from the late Paleozoic to the Cenozoic.
For the last 550 mya the highest sea leves were during the mid-Cretaceous times - back then oceans were 250 meters above the modern levels. At the same time the temperatures hit their maximum too - the mean global temperatures were well above 30 degrees celsius. This led to series of global anoxia (lack of oxygen) events in the oceans. There were no glaciers on the poles. But not all of the Cretaceous was like this. There were time intervals (like early Cretaceous China or maastrichtian North America) when the climates were more like todays though the temperatures were still somewhat higher. The levels of carbon dioxide were few times higher than todays. In the early Cretaceous the South Atlantic and Indian oceans started to open, due to the breaking up of Gondwana. The continents moved slowly to more familiar positions. Late Cretaceous was time of wide spread volcanism and magmatism.
The Mesozoic era closed when 10 kilometers wide meteorite (asteroid or less likely a comet) hit the Earth and led to the most famous of all mass extinctions - Cretaceous-Paleogene mass extinction. The impact happened near what's now Yucatan peninsula, forming the Chixulub crater. The aftermaths of this collision, along with the intensive late Certaceous volcanism, wiped out big part of the life on Earth. The most notable victims of this cataclysm were the non-avian dinosaurs, followed by the pterosaurs. Many other groups like plesiosaurs, mosasaurs, ammonites, belemnites, etc., were also wiped out without leaving descendants. The stage for the beginning of Cenozoic era was set.
Dicynodont therapsid that lived in the souther part of the supercontinent Pangaea (modern South Africa, India and Antarctica). It was the most common terrestrial vertebrate animal in the begging of the Triassic period. Lystrosaurus was a herbivore. Media: Watercolours Done: 2008
Marasuchus is a dinosauriform archosaur from the middle Triassic of Argentina. It was 40 cm in lenght. The common ancestor of all dinosaurs was an animal that probably looked pretty much like Marasuchus. Media: Pencils Done: 2010
Saurosuchus galilei (on top) is stalking a sleeping Herrerasaurus. Saurosuchus is a rauisuchian archosaur, distant relative of the crocodylian group. With it's lenght of about 7 meters it was the top predator of its environment. Media: Ink Done: 2008
This is one of the oldest known dinosaurs to date. It lived 228 mya in Argentina, and was carnivore. Herrerasaurus, with its lenght of over 4 meters, was the biggest dinosaur for its time. Most paleontologists classify it as very primitive theropod. Theropods are dinosaurian group which gave rise to birds in the Jurassic. Media: Pencils Done: 2011
Vancleavea campi is unusual archosauriform from the Late Triassic of North America (Ghost Ranch). This animal is characterized by its extensive armor composited of imbricated osteoderms covering the entire body. The tail is deep because of the elongated osteoderms located on its dorsal part. Limbs are very short. Media: Ink Done: 2011
Plateosaurus engelhardti is a "prosauropod" that lived 214-204 mya. It was herbivourous bipedal animal. This is one of the best known dinosaurs - remains from over 100 individuals are found to date. Media: Watercolours Done: 2009
Melanorosaurus is a 8 meters long sauropodomorph, lying very close to the origin of Sauropoda- the group of the biggest terrestrial animals to ever walk of Earth. Media: Pencils Done: 2010
One of the most complete early Jurassic theropods known to date. It's easily distinguished from other theropods by the two crests running along its skull. Dilophosaurus grew up to 6 meters in lenght. Media: Watercolours Done: 2008
Cryolophosaurus is an early Jurassic theropod, one of the few dinosaurs found in Antarctica. It was carnivore feeding on the primitive sauropodomorph Glacialisaurus. Some paleontologists suggest close relationship between Cryolophosaurus and Dilophosaurus. Media: Watercolours Done: 2008
A male “Omeisaurus” tianfuensis is defending a female attacked by sinraptorid theropod. The scene takes place in China during the late middle Jurassic. Media: Watercolours and pencils Done: 2012
Epidexipteryx hui is a member of Scansoriopterygidae, an unusual group of theropod dinosaurs most probably closely related to birds (according to some paleontologists these animals fall into Avialae). It lived during the middle or late Jurassic period in China, and was probably an arboreal animal. The function of its extra long third finger is still debated. Media: Pencils Done: 2008
Primitive sauropod from the middle Jurassic period, found in Africa (Niger). Interesting characteristic of this sauropod are the spike osteoderms at the tip of the tail. They form a structure similar to the thagomizer of stegosaurs. Media: Pencils Done: 2009
Large theropod from the late Jurassic of North America. It lived with another, even bigger theropod - Allosaurus fragilis. Ceratosaurus is typical for its nasal horn and pair of horn-like ridges in front each eye, and the presence of small osteoderms along its back. Media: Pencils Done: 2010
Barosaurus lentus is a diplodocid sauropod very similar to the famous Diplodocus. It had longer neck than the latter but its overal lenght was about the same - 26 meters (though some individuals of Diplodocus were over 30 meters). Two theropods from the species Allosaurus fragilis are running by. Media: Watercolours Done: 2009
Reconstruction of the theropod Allosaurus fragilis. Allosaurus was the biggest meat-eating dinosaur for its time - its average length was about 8 to 9 meters, but some individuals may have reached 12 meters. It lived during the late Jurassic, 155-150 mya. Media: Watercolours and ink Done: 2008
Formerly knowns as Brontosaurus excelsus, A. excelsus was a heavily build diplodocid sauropod. It lived 154-150 mya, in North America. This sauropod was about 23 meters long and weighted over 20 tons - one of the biggest terrestrial animals for its time. Media: Watercolours Done: 2009
Stegosaurus is one of the biggest stegosaurid dinosaurs. It's one of the most popular dinosaurs, mainly because of its distinct features - 2 rows of osteoderms that run along the back and thagomizer towards the tip of the tail. Decades ago some paleontologists claimed Stegosaurus had "sacral brain", idea that unfortunately got fairly popular. Today, this is proved to be wrong. Media: Pencils Done: 2010
Diplodocus carnegii reconstructed the way it was seen by paleontologists in the late 19th and early 20th century. Back them it was thought that sauropods were amphibious or even aquatic animals simply because of their gigantic size. Media: Watercolours Date: 2009
3 reconstructions of the sauropod Diplodocus carnegii, which show how the understanding of sauropod's anatomy, behaviour and ecology has changed through the years. The one at the top is based on reconstructions from the early 20th century, the middle one was typical for the period 50's-70's, while the lowermost shows the modern view on sauropods - as active, warm-blooded, terrestrial animals. Media: Watercolours Done: 2009
Small sauropod, related to the diplodocids, from the late Jurassic of Africa (Tanzania). Media: Ink Done: 2009
Europasaurus is a primitive macronarian sauropod from the late Jurassic of Germany. This sauropod was a dwarf - it was only 6 meters long when adult. In comparison, other macronarians are giants with lenght of over 30 meters and weight of atleast 80 tons. The small size of Europasaurus is caused from the living on an relatively small island with limited resources. Media: Ink Done: 2009
A pair of mating Dacentrurus armatus (the depicted behaviour is speculative). Dacentrurus is probably the biggest stegosaurid known to date. It lived in what's now Portugal, some 150 mya. Rhamphorhynchoid pterosaurs are flying around. Media: Pencils Done: 2009
Dinosaurs on portuguese beach during the late Jurassic - Torvosaurus tanneri (left), Lourinhanosaurus antunesi (right) and Lusotitan atalaiensis (in the background). Media: Watercolours Done: 2009
A small ornithopod from the early Cretaceous of England. Media: Pencils Done: 2010
About 10 meters long ornithopod from early Cretaceous of Europe. It has been long time famous for its thumb spike. Iguanodon was the second dinosaur to be named - the name was given by Gideon Mantell, in 1825; although the species named by Mantell is now considered to be diferent dinosaurs. The only valid species of Iguanodon is I. bernissartensis from Belgium. Media: Pencils Done: 2010
Medium sized carcharodontosaurid that lived 130 mya, in Spain. Media: Pencils Done: 2010
Chinese sauropod that lived during the early Cretaceous, 130 mya. Media: Watercolours Done: 2009
130 million years old heterodontosaurid dinosaur that have been covered with filamentous structures similar to primitive feathers. Tianyulong is an ornithischian, while theropods (including birds), the only group known to have feathered members are saurischians - it's as far from birds as a dinosaur can be. If these structures turn out to share common origin, then it would be safe to consider that filamentous feather-like structures are primitive for all dinosaurs. Media: Pencils Done: 2010
Xiaotingia zhengi is attacking a generic lepidosaur. X. zhengi is a newly described archaeopterygid from the Late Jurassic of China which may lead to reconsideration of the relationships at the base of the clades Deinonychosauria and Paraves. Media: Ink Done: 2011
Tyrannosauroid theropod from the early Cretaceous of China. It was "only" 4-5 meters long. Media: Watercolours Done: 2009
Sauroposeidon, from the early Cretaceous of North America, is close relative of the jurassic sauropods Brachiosaurus and Giraffatitan. Only four vertebrates are known from this sauropod, but their size shows it was really big animal with very long neck, among the longest seen in Sauropoda. Media: Watercolours Done: 2009
Very unusual sauropod with uncertain affinities. It lived in South America, around 110 mya. Media: Pencils Done: 2009
Dicraeosaurid sauropod with very specific neck vertebrates. The spines on the neck could have formed a pair of sails but this hypothesis was rejected by the majority of the paleontologists. Spines probably projected like spikes along the neck. Either way, they probably served for visual display among the other functions. Media: Watercolours Done: 2009
Early Cretaceous tapejarid pterosaur with impressive head crest. It lived in what's now Brazil. Media: Pencils Done: 2008
Brazilian pterosaur from the early Cretaceous (108 mya). Media: Pencils Done: 2008
Primitive ceratopsian dinosaur that lived in Asia, during the early Cretaceous. It had filamentous integumentary structures on its tail. Except Tianyulong, Psittacosaurus is the only other ornthischian dinosaur known to have integument different from scales. Rest of the body was covered with typical dinosaurian scales though. Fossil finds suggest that Psittacosaurus took care for its young. Media: Pencil Done: 2010
Titanosaurid sauropod that lived in what's now Africa, during the early Cretaceous. It was around 16 meters long. Media: Pencils Done: 2010
This theropod is one of the biggest meat-eating dinosaurs - it's just slightly longer than T. rex but more lightly build and with not so strong jaws. Its teeth were suited for tearing flesh and not for breaking bones like T. rex's. Carcharodontosaurus lived around 100 to 93 mya, in what's now Sahara desert. This predator shared its habitat with several other big carnivorous theropods. Media: Watercolours Done: 2008
Spinosaurus aegyptiacus is the biggest theropod known to date. Estimations for its total lenght vary between 15 and 18 meters. Some studies suggest that it spent a lot of its time into the water. Spinosaurus probably fed mainly on fishes and small to medium sized dinosaurs. It lived about 100 mya, in Africa. There is no agreement among paleontologists what's the exact function of Spinosaurus' sail. Media: Pencils Done: 2010
Giant titanosaurian sauropod from the early late Cretaceous of Egypt. This large animal was part of mangrove ecosystem. Despite their enormous size, sauropods, like Paralititan, were good swimmers (especially in shallow waters) because of their extensive air-sack system (possesed by theropods too) which gave them positive buoyancy. Media: Watercolours Done: 2009
Unlike most members of the clade Dromaeosauridae, this dromaeosaurid was very big - its estimated lenght is about 6 meters. Achillobator lived about 90 mya, in what's now Mongolia. Media: Charcoal Done: 2009
An allosauroid theropod from the late Cretaceous of Argentina. The fossils of this animal show that it had bird-like respiratory system. Actually all fossil evidence points toward the conclusion that advanced respiratory system is a primitive characteristic for atleast all saurischian dinosaurs (theropods and sauropodomorphs), if not the whole Dinosauria. Media: Watercolours Done: 2008
Shuvuuia deserti is an alvarezsaurid theropod. Due to their extremely bird-like anatomy, alvarezsaurids were once considered being flightless avian-dinosaurs (birds). Lenght - 60 cm. Nemegtbaatar gobiensis was relatively big mammal that lived along side many species of dinosaurs. The scene take place 75 mya, in Mongolia. Media: Pencils Done: 2008
An oviraptorosaur from the late Cretaceous (75 mya) of Mongolia. Probably it was an omnivore. Like all oviraptorosaurs, Khaan was covered with feathers. Media: Watercolours Done: 2009
Although it became famous with its appearance in "Jurassic Park", the real Velociraptor looked nothing like the movie monster - it was turkey sized animal that was covered with feathers and had wings. There are no direct evidence that velociraptors hunted in groups. Velociraptor lived some 75 mya, during the late Cretaceous, in Asia (Mongolia). Media: Pencils Done: 2010
Crested hadrosaurid ornithopod from the late Cretaceous (76-73 mya) of North America. Most probably its unusual crest was used as communication device inside the species or between different species. Like all ornithopods, Parasaurolophus fed on plants. It reached lenght of about 9 meters. Media: Pencils Done: 2010
Ceratopsian dinosaur, relative of the later Triceratops and Torosaurus. It grew up to about 8 meters in lenght. Pentaceratops lived along side the hadrosaurid Parasaurolophus. Media: Pencils Done: 2010
Bambiraptor is 75 million years old dromaeosaurid theropod. This dinosaur is characterized by its long arms with semi-opposable first finger and big brain comparable to those of some modern birds. As all dromaeosaurids, Bambiraptor was covered with feathers. Media: Pencils Done: 2008
Euoplocephalus was one of the biggest ankylosaurian dinosaurs. It lived during the late Cretaceous in North America. As an ankylosaur it had bony tail club which was probably used for defence from predators. Media: Pencils Done: 2010
1.5 meters long dromaeosaurid from the late Cretaceous of Argentina. It had longer snout and much shorter arms in comparision with the northern dromaeosaurids like Velociraptor and Deinonychus. Media: Watercolours Done: 2009
Saltasaurus is a titanosaurid sauropod covered by an armor composed by osteoderms. It lived about 70 mya, on the territory of modern Argentina. Large nesting ground in Argentina, with eggs of sauropod dinosaurs (with preserved embryos), was thought to belong to the species Saltasaurus loricatus. Media: Watercolours Done: 2009
Titanosaurian sauropod from the latest Cretaceous of Madagascar. Estimated lenght - 15 meters. Media: Pencils Done: 2010
Oviraptorid theropod that lived approximately 70 mya, in what's now Mongolia. Media: Watercolours Done: 2009
Tyrannosaurid dinosaur with long and low snout, from the late Cretaceous of Asia (Mongolia). Bony crests along the mid line of the skull were present. It lived in the same area as Tarbosaurus bataar, another tyrannosaurid. The estimated length of Alioramus is around 6 meters. According to the fossil evidence for presence of feathers in primitive tyrannosauroids, Alioramus was probably feathered at some point. Media: Pencils Done: 2009
Late Cretaceous titanosaurian sauropod that lived in India. Its lenght is estimated to 18 meters. Media: Pencils Done: 2010
Titanosaurian sauropod from the late Cretaceous of Europe. Ampelosaurus is characterized by extensive armor of osteoderms covering its back. Estimated lenght - 15 meters. Media: Watercolours Done: 2009
Extremely speculative reconstruction of a putative ornithomimosaur from the late Cretaceous, probably Maastrichtian, of Bulgaria. Mateus et al, 2010, described fragment from left humerus of theropod dinosaur, which they suggested belongs to ornithomimosaur. Media: Schneider Topliner 934, 0.4 mm, red colour Done: 2012
Very unusual dromaeosaurid from the latest Cretaceous of Romania. Its distinctive characteristics are the two fingered hands and the extremely modified hallux (first toe) that was turned into second sickle claw. This theropod lived on island dominated by dwarf dinosaurs. Balaur was more robust in comparison with other dromaeosaurids. Media: Pencils Done: 2010
Alamosaurus is titanosaurian sauropod from southwest North America, and is one of the last sauropods to exist on Earth. Media: Watercolours Done: 2010
Pachycephalosaurus is the biggest "thick-headed" dinosaur and one of the last non-avian dinosaurs before their extinction in the end of the Cretaceous period. Recently it was suggested that this dinosaur had very complex ontogeny, and the other pachycephalosaurid dinosaurs from the Hell Creek Formation, Dracorex and Stygimoloch, are actually young and sub-adult forms, respectively, of Pachycephalosaurus. Media: Pencils Done: 2010
Pachycephalosaurid dinosaur from the latest Cretaceous of North America. Stygimoloch could be a sub-adult individual of the species Pachycephalosaurus wyomingensis. Media: Pencils Done: 2008
Avisaurus archibaldi (left) and Brachychampsa montana (right) are two of the less famous animals in the Hell Creek fossil fauna. They represent the two branchs of the Archosauria - the dinosaur (or bird) one and the crocodylian one. The depicted animals lived at the end of the Mesozoic era along side dinosaurs like Tyrannosaurus and Triceratops. Media: Pencils Done: 2012
Very large, up to 12 meters, crestless hadrosaurid from the latest Cretaceous of North America. Edmontosaurus was the main source of food of adult Tyrannosaurus rex. Although it didn't have horns, armor or other defence weapons, Edmontosaurus was far from defenceless herbivore. Its sheer size and massive tail were formidable obstacle to any predator. Edmontosaurus is only one of the few dinosaurs, from which mummified remains are known. Media: Tempera on canvas Done: 2008
T. rex is the biggest coelurosaurian theropod, with average lenght of 12 meters. It was very specialized predator with bone-crushing jaws. Like all big meat-eating animals it was both hunter and scavenger. Fossil evidence shows that adult T. rex hunted on Edmontosaurus and Triceratops. Young T. rex individuals probably occupied different ecological niche from the adults, and fed on other animals, like pachycephalosaurids, dromaeosaurids, etc. Media: Ink Done: 2009
A pair of tyrannosaurs is attacking an young Edmontosaurus annectens. According to recent discovery of feathered tyrannosauroids, and the rumoured fossilized patches of scaleless skin assigned to T. rex, it's reasonable to say that T. rex was atleast partly feathered. Featherless reconstructions of T. rex, even if they are anatomicaly accurate, should be considered based on outdated information. Media: Pencils Done: 2012