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The World - 144 - 65 MY: a period of dramatic changes and a transition towards the modern world -

Jarðsaga 1 - Saga Lífs og Lands – Ólafur Ingólfsson Late -Early Cretaceous: Pangea is ripping apart, creating new landscapes and and changing evolutionary conditions Continental drift and Ocean spreading causes transgressions in N America and Europe Texas (93.5-88.5 million ago)

Large scale trans- gression from both north and south connects Arctic to Gulf region, dividing into two landmasses. Europe undergoes a of transgression- regression events Climate and landscapes during the early Cretaceous

No major mountain- building episode for 100 MY. Erosion and deposition prevailed. Widespread plains and lowlands, deltas, swamps and warm, shallow seas. There were no glaciers anywhere on Earth, and global sea level was 60m + Early Cretaceous: A world steaming under near-tropical conditions... (cool temperate climates at very high latitudes, >70oN and S)

... with incredible diversity of both fauna and flora, as well as optimal conditions for evolution and occupation of new evolutionary niches... Oceanic circulation The fossil story reflecting warm conditions

Finds of Cretaceous fossil tree-trunks The fossil story reflecting warm conditions Cretaceous vs modern temperatures

http://www.clas.ufl.edu/users/emartin/GLY3074S01/figures/cretgradient.htm Laterite and Laterite Bauxite Bauxite Thick, red, greatly The chief ore of Residual deposits formed weathered and aluminium, under tropical climate altered strata of consisting of conditions, where sili- tropical ground. hydrous aluminium cate-rich rocks are Laterites are red oxides and leched during a wet because silicates aluminous laterite. season and subject to have been leached It is a claylike strong evaporation during out, and iron and amorphous dry season... aluminium salts now material formed predominate. by the weathering Horizons are unclear of silicate rocks and the nutrient under tropical status of the soil is conditions. The low. Laterite is soft chief producers but hardens rapidly are Australia, when to the air until Guinea, Jamaica, it has a brick-like Russia, Brazil, and hardness. Surinam. Deltas and swamps...

Crocodile-like appeared in the Late , and true croc´s in Jurassic times. Some Cretaceous crocodiles were awesome: the giant Deionsuchus ('terrible crocodile') was 12-14 m long and had a skull 1.8 m long The crocodile is believed to have reached 14 m in length. The lived about 110 million years ago in what is now the windswept Ténéré Desert in central Niger. The snout and > 100 teeth were designed for grabbing prey–fish, turtles and that strayed too close. This enormous reptile would have made Africa’s ancient riverbanks a dangerous place, even for a Fossil remains of one of the largest crocodilian species . The fossils belong to an ever to live have been extinct creature named found in the Sahara by a Sarcosuchus imperator ("flesh team led by Paul Sereno (University of Chicago). crocodile emperor") Metriorhynchus – purely aquatic crocodile Metriorhynchus was ca. 3 m long. It was a highly modi- fied aquatic predator which had evolved from its cousins, the land living crocodiles. Apart from its long snout,it bears little resemblance to Metriorhyncus probably moved the conventional crocodile by sideways beatings of its tail shape. Metriorhynchus was and it had evolved to be more flexible and mobile than its land- specially adapted to an living relatives, making it faster aquatic way of life with in water. Its skin was also less flippers to replace the legs scaly and more flexible than that of the land-crocodiles, reducing and a vertical fin at the end its resistance through the water. of its tail to help it swim. Snakes and lizzards

Snakes are uncommon as fossils: They have lightly constructed skeletons and skulls comprised of separate moveable sections and so are generally too fragile to preserve well. The more They were the last major group of specialised reptiles to appear in the fossil record. poisonous snakes One of the earliest known forms was are not thought Dinilysia, meaning 'terrible destroyer', to have evolved which lived in the Early Cretaceous until the middle period. It seems likely that snakes of the Tertiary evolved from aquatic , although period, perhaps most have now returned to life on land. 30 MY ago. And then there were the dinosaurs... Cretaceous dinosaurs lived on all - continents, except Antarctica Development towards heavier herbivorae armour and more vicious predators The break-up of Pangea affected dinosaur evolution

Dinosaurian paleobiogeography: Temporally calibrated areagram showing the breakup of into 10 major land areas by the end of the Cretaceous. Checkered bars indicate high-latitude con- nections that may have persisted into the . Five paleogeographic reconstructions divide continental areas into dry land (black) and shallow (epieric) seas (unshaded). Different lines of evolution among the allosaurs

Dinosaurian paleobiogeography. , , and , living on N America, S America, and Africa, respectively, approximately 90-110 MY. Dino´s walked across existing land bridges...

The geographic distribution of ceratops and some other groups during Late Cretaceous can only be explained by dispersal across Beringia. The Dino´s... The dinosaurs came in all varieties including carnivores (meat-eaters), herbivores (plant eaters) and omnivores (all-eaters). Some were small as a chicken and others as big as a house, some of them flew like . They occupied almost every nisch...

Within the last decaded there has been a transformation in our under- standing of dinosaur paleobiology. They now are regarded as active, agile, and adaptable, as opposed to huge, awkward, lumbering versions of large reptiles. HERBIVORES: Plant-eating dinosaurs were the most common large animals in the Cretaceous ecosystems

A group of , medium-sized sauropods, are reconstructed browsing in a conifer forest. Their physology is poorly understood, and some aspects are widely debated:

• Biomechanical problems. Some paleobiologists argue that the mechanics of muscle and tendon attachment would not permit these animals to raise their long necks that far above the horizontal. • Blood pressure. It is difficult to imagine how sufficient blood could have been provided to the head at extreme elevation to avoid unconsciousness when the head was held up for any extended period. The huge sauropods, so typical for dinosaurs, continued to live in Gondwana, but died out in Laurassia

Paralititan stromeri, a , Madagaskar new, giant sauropod dinosaur from Upper Cretaceous mangrove deposits in Egypt. Laurassic herbivores relatively small and heavily armed Ankylosaurs: They were relatively small, heavily armored Cretaceous herbivores. Their ecology is poorly understood, but their build suggests that they fed primarily on vegetation at ground level.

Hadrosaurs: A small group of Telmatosaurus, hadrosaurs from the Upper Cretaceous of central Europe. Hadrosaurs were a very diverse group of bipedal herbivores and were the most important herbivore group during the Cretaceous. Ceratopsians

The most widely recognized ceratopsian dinosaur is Triceratops, but this was a very diverse group of Creta- ceous herbivores and the only group that may have been adaptively radiating near the end of the period. No armour, quick and agile: an alternative strategy...

Curiously, the most abundant and diverse of the Cretaceous herbivores were the unarmoured ornithopod dinosaurs, specifically the hypsilophodontids and iguanodontian lines, all of which achieved cosmopolitan distribution. Dinosaur Carnivores Given the relatively large size of most dinosaur carnivores, they would have required significant numbers of large prey animals to sustain their populations. Carnivores would thus be much less numerous than herbivores in any ecosystem.

An Ornithomimus, Cretaceous, USA. These animals were probably very quick and agile and may have preyed largely on the eggs of other dinosaurs. The Therapods

The theropod (meaning "beast-footed") dinosaurs are a diverse group of bipedal saurischian dinosaurs. They include the largest terrestrial carnivores ever. Birds are the descendants of small nonflying theropods. http://www.ucmp.berkeley.edu/diapsids/saurischia/theropoda.html T-Rex and friends...

Tyrannosaurus rex was a huge (12 m long, about 6 m tall, 5-7 tons) meat-eating dinosaur that lived during the late Cretaceous, 85-65 MY ago. T. rex lived in a humid, semi-tropical environment, in open forests with nearby rivers and in coastal forested swamps. Until recently, Tyrannosaurus rex was the biggest known carnivorous dinosaur; Gigan- otosaurus and Carcharodontosaurus were slightly bigger. How fast did the dinosaurs move:

There is a general relationship between speed and stride length in living animals. This can be used to estimate how fast the dinosaurs were:

• Sauropods and ankylosaurs were slowest, ~ 3-5 km/hr • Most ornithopods were faster, ~ 5-7 km/hr • Theropod predators were fastest, ~ 10 km/hr, bursts up to 40-50 km/hr Velociraptor ("Speedy Thief“) Velociraptor was a fast- running, two-legged dinosaur. This meat-eater had about 80 very sharp, curved teeth in a long, flat snout; some of the teeth were over 2.5 cm long. This predator had an s-shaped neck, arms with three-fingered clawed hands, long thin legs, and four-toed clawed feet. Velociraptor's head was about 18 cm long. Velociraptor may have been able to run up to roughly 40 km/hr for short bursts. Velociraptor’s murder weapon

A 9 cm long, sickle-like, retractible claw was on the middle toe of each foot. This claw was its main weapon, and could probably kill most of its prey (plant-eaters like hadrosaurs) easily. A small but smart killer

Velociraptor was 1.5-2 m long, and 1 m tall. It may have weighed about 7-15 kg. It had a stiff tail that worked as a counterbalance and let it make very quick turns. Velociraptor's brain was relatively large in comparison to its body size (this is true for all the Dromaeosaurid dinosaurs, who were the most intelligent dinosaurs). How brainy were the dinosaurs?

• Big Sauropods and Stegosaurs: EQ of ~0.1-0.6 • Ceratopsians and Ornithopods: EQ of 0.5-1.5 • Big Theropods: 0.9-1.9 • Some smaller Theropods, like velociraptor: EQ 5-5.8

EQ is the ratio of the brain weight of the animal to the brain weight of a "typical" animal of the same body weight. We are comparing dinosaurs to reptiles, but even the “dumbest” has twice the brain size of a similar sized reptile

Are the dinosaurs still around (as birds)? During Late Creta- ceous, there was an extraordinary range of birds and dinosaur-like protobirds. It is impos- sible to tell where dinosaurs ended and birds began...

There are numerous striking similarities between carnivorous dinosaurs and birds. Oviraptor

Oviraptor (“Egg thief”), Upper Cretaceous (85-75 MY); Length (up to) 1.8 m; omnivorous; Found in Mongolia (" Mimics")

Ornithomimids were a distinctive group of theropod dinosaurs, who are a good example of convergent evolution with the birds such as ostriches. Ornithomimids were generally slender, lightly-framed, and reached huge sizes (some attaining lengths of 7 m). Feathered dinosaurs A new range of fossil finds, mostly from China, are revealing that a large number of small dinosaurs were covered by feathers

Sinornithosaurus was a small dinosaur that probably fed on animals such as reptiles and . Like larger raptors the animal may have attacked with a jumping stance, as shown here. Although quite bird- like, this dinosaur could not glide or fly, which raises the issue as to why it evolved feathers. Why Feathers? • Sexual Display. One possibility is that feathers may have served to enhance sexual display as part of mating behaviour. • Insulation. One important role for feathers may well have been insulation. If some dinosaurs were warm blooded, small individuals would face a problem of significant heat loss due to an unfavorable (high) surface to volume ratio. • Large vs. Small Bodies. The hatchling has a covering of feathers to assist in retaining body heat, but the feathers are lost as the animal grows to adult size. inosaur/bird d feathered nother a

Caudipteryx Yet from China... Uenlagia (“half-bird”)

Several features of Unenlagia (originally described from Upper Cretaceous of Argentina) are more birdlike than in any other non-avian theropod so far discovered. The evidence suggests that it could flap its arm, although Unenlagia was much too heavy to fly with such a short wing. The development of birds... The Jurassic Archaeopteryx was one tran- sitional form between birds and reptiles. Unlike all living birds, Archaeopteryx had a full set of teeth, a flat breastbone, a long, bony tail, and three claws on the wing which could have still been used to grasp prey (or maybe trees). However, its feathers, wings, wishbone and reduced fingers are all characteristics of birds.

Ichthyornis: This ‘fish bird’ was an 30 cm long bird of the Cretaceous period that dived to catch fish. Ichthyornis could probably fly and had long wings. It had teeth in its jaws, unlike modern birds. Its remains were found in Kansas, USA. Ichthyornis

Ichthyornis was first described in 1872, from sedi- ments in Kansas, and originally thought to be a marine reptile. Birds of the Cretaceous The evolution of birds is not well known, since they preserve badly as fossils

Hesperornis or ‘western bird’ was a >1 m long flightless bird of the Late Cretaceous period. Fossil skeletons have been found in Kansas and Alberta, Canada. This fish-eating bird had large, possibly webbed feet and may have been a good swimmer and diver.

http://www.sino-collector.com/eng/_private/cjyd/zjlt/hjs-hs/hjs02-3.htm Action in the skies

A flock of Criorhynchus soars above a long- necked Elasmosaurus, while the ternlike Ichthyornis skims the waves at lower left. ...action in the skies...

The Quetzalcoatlus northropi had a wingspan of 12- 13 m, making it the largest known flyer of all time...

The giant Quetzalcoatlus has been compared with large modern birds such as condors and eagles and it has been concluded that, like them, it ate carrion. But the anatomical evidence does not support this. Quetzalcoatlus had a long inflexible neck that would not have been desirable for vulture-like feeding. Its long, tweezer-pointed, and toothless jaws were not suited for tearing apart dinosaur cadavers, and are more suggestive of a diet of fish or molluscs and arthropods in shallow flood basins. The diatoms (kísilþörungar) appear

They are among the most important aquatic micro-organisms today: they are extremely abundant both in the plankton and in sediments in marine and freshwater ecosystems, and because they are photosyn- thetic they are an important food source for marine organisms. Some Cretaceous rocks are formed almost entirely of fossil diatoms, and are known as diatomite or diatomaceous earth. These deposits are mined commercially as abrasives and filtering aids. Analysis of fossil diatom assemblages may also provide important information on past environmental conditions. Enormous Cretaceous chalk deposisits

The massive chalk deposits (>200 m) of NW-Europe (Denmark, England, N France) are composed of the armour plates of calacareous nannoplankton (kalkþörungar) Life on the sea floor

Life on the sea-floor began to take on a modern appearance during the Cretaceous Period.

Cretaceous Oysters – some grew to very large sizes Rudists build reefs Rudists were the dominating Cretaceous reef-builders, at the expense of the corals

Rudist: An extinct bivalve mollusk from the Jurassic and Cretaceous that had two different sized and shaped shells; they usually were attached to the substrate and were either solitary or in reeflike masses. Reef builders since the The shallow seas

A gigantic (0.3 m) ammonite shell of Placenticeras Helioceras was a loosely-coiled cephalopod that lived in the shallow seas that bisected North America in the Cretaceous. The shallow seas...

Plesiosaurs were marine A very large Cretaceous reptiles with a stocky body, marine turtle four large flippers, and a (Archelon) long tail.

Mosasaurs were large marine lizards up to 9 m in length. They preyed largely on fish A mosasaur in action

The mosasaurs are distinct relatives of modern snakes and perhaps the Komodo Dragon of Indonesia

http://www.oceansofkansas.com/mosasaur.html http://www.oceansofkansas.com/Greatrep.html Reconstruction of marine life in upper Cretaceous of USA The fishes (beinfiskar) develop are characterized by symmetrical tails, round scales, specialized fins and short jaws

By Late Cretaceous time, a wide variety of tele- osts existed, including close relatives of the Diplomystus brevissimus modern sunfish (“tungl- fiskur”), carp (“vatna- karpi”), swordfish (“sverðfiskur”), eel (“áll”) and salmon (“lax”). Fish-in-a-fish

Xiphactinus audax, (Bulldog Fish), was a species of very large (5 m) predatory fish that lived in the ocean during the Late Cretaceous. Enter the mammals... The three modern mammal groups: (nefdýr), marsupials (pungdýr), and placentals (legkökudýr) originate during the Cretaceous.

The earliest mammals, such as started to develop during latest Triassic and early Echydna and Platyphus Jurassic. Most Mesozoic animals were small and would remain so until the extintion of the dino- saurs opened niches that permitted the adaptive radiation of mammals in the early . Bandycoot, a small Koala marsupial Geological ranges for mammals Insects develop before the appearance of flowering plants

Insects make up over three- fourths of all known animal species on the planet...

A 95 million old fossil insect (a ) in from the Raritan formation of New Jersey

The oldest true flies are Triassic in age; butterflies appear in the Jurassic; and by the end of the Cretaceous, almost all the familiar true flies groups had appeared. Insects and flies, as far as we can tell, were completely unaffected by the extinction event at the end of the Cretaceous... , , , ... They all originated during the Cretaceous The sudden emergence of flowering plants

More than one-hundred years ago, Darwin called the origin of angiosperms an "abominable mystery". One of the biggest questions about early angiosperms, besides their origin, is the nature of their growth habit. Were the first angiosperms woody trees and shrubs, or were they small herbs?

First appearing in the tropics during the Lower Cretaceous, around 125 MY ago, the flowering plants first radiated in the middle Creta- ceous, about 100 million years ago. By the end of the Cretaceous, a number of forms had evolved that any modern botanist would recognize. No fossils showing a transition from gymnosperm to angiosperm have been discovered. The flowering plants little secrets of success... 1. Double fertilization. First fertilization produces egg within the ovary (eggleg); second fertilization produces a storey of food for the seed.

The rapid manufacturing of this food supply allows for the quick release of a well fortified seed.

Most gymnosperms have reproductive cycles of 18- 24 months; angiosperms have reproductive cycles of few weeks!

A photomicrograph of lily (lilja) double fertilization. Pollinating by insects... 2. Symbiotic relationships between flowering plants and insects. Isects benefit from the nutritious nectar that the flowers provide; The flowers benefit because the insects (unknowingly) carry pollen from one flower to another, fertilizing the plants on which they feed -Gymnosperms dominated the Mesozoic landscape, but are today mostly confined to cooler temperate climates - Angiosperms dominate since the Late Mesozoic Oldest in the world Chinese and U.S. scientists have identified what is believed to be the world's oldest flowering plant. The 140-million-year-old fossil was found in northeastern China. Sun Ge, a researcher with the Academia Sinica in Nanjing, China, and David Dilcher with the University of Florida, worked together earlier this year to identify the specimen, which predates the previous oldest-known flower by 25 million years. Did dinosaur grazing boost flowering plants? Angiosperms and the modern world...

• Nearly all of our food comes from flowering plants: grains, beans, nuts, fruits, vegetables, herbs and spices; as do tea, coffee, chocolate, wine, beer, tequila... • Angiosperms are the staple for herbivores that we in turn eat: sheep, cattle, goats, pigs... you name it... • Much of our clothing comes from them as well: cotton and linen are made from "fibers" of flowering plants, as are rope and many commercial dyes are extracted from other flowering plants. • We also owe them credit for a large number of our drugs, including aspirin, numerous prescribed drugs and controlled drugs such as opium, cocaine, marijuana, and tobacco. Late Cretaceous: Active plate boundaries and mountain building start changing the scene... The Rockies were formed in the Mesozoic and Early The Cordilleran Cenozoic eras during the Cordilleran orogeny. They orogeny are geologically complex, with remnants of an ancestral Rocky Mt. system and evidence that uplift, which involved almost all mountain- building processes, occurred as a series of pulses over millions of years. The mountains have since been eroded to expose ancient crystalline cores flanked by thick upturned layers of sedimentary rocks. • Cordilleran orogeny: A protracted episode of deformation affecting the western margin of North America from Jurassic to Early Cenozoic time; typically divided into three separate phases called the Nevadan, Sevier, and Laramide orogenies. •CretaceousInteriorSeaway:An interior seaway that existed during the Late Cretaceous; formed when northward-transgressing waters from the Gulf of Mexico joined with southward-transgressing water from the Arctic; effectively divided North America into two large landmasses. • Laramide orogeny: The Late Cretaceous to Early Cenozoic phase of the Cordilleran orogeny; responsible for many of the structural features of the present-day Rocky Mountains. The Laramide orogeny

A series of mountain-building events that affected much of western North America in Late Cretaceous and Early Tertiary time. Evidence of the Laramide orogeny is present from Mexico to Alaska. Laramide thrusts

The Keystone thrust. This fault shows the Bonanza King formation (gray) over folded Jurassic Nugget sandstone (red). Rocky Mts landscapes Summing up the Cretaceous • Latitudional temperature gradients were gentle – warm even at high latitudes and no glaciers • The Cretaceous was an extreme greenhouse situation • Gondwana broke apart during the Cretaceous Period, forming the South . The Tethys seaway existed, that carried warm waters through the Mediterranean region • On land, flowering plants diversified and evolved, together with the insects • The mammals evolve and diversify • In the sea, the phytoplankton assumes a modern character, and crabs and teleost fishes evolve and diversify significantly K/T Boundary The Cretaceous-Tertiary boundary is marked by a mass extinction: 50-60% of all living species of animals and plants became extinct. Caused by a large meteorite impact? Causes-effects of the 65 MY K/T extinction During the K-T extinction (65 MY ago) 85% of all species disappeared. The dinosaurs perished in the K-T extinction, and several other terrestrial and marine groups were also severely affected or eliminated. Evidence for catastrophism Among those that perished at the K/T boundary is found were the , belemnids, in a layer containing unusually many species of plants, ammon- high concentrations of ides and marine reptiles. Groups which were severly affected Iridium, originating either included planktonic foramini- from the earth's mantle or fera, diatoms, molluscs and fish. from extra-terrestrial Remarkably, most mammals, meteors. This layer has been birds, turtles, crocodiles, found found in both marine lizards, snakes, and amphibians were primarily unaffected by and terrestrial sediments, at the K/T extinction... many sites around the world. ?

Cretaceous extinctions 90 million years ago 80 70 65 60

Figure 15.5 Meteorite Impact or Volcanic Eruptions?

• The widespread distribution of the Iridium layer may have been caused by a meteorite impact. Recent research suggests that the impact site may have been in the Yucatan Peninsula of Mexico. • The high concentrations of Iridium in the boundary layer could be result of massive volcanic eruptions at the K/T boundary: either in the Deccan Traps (India and Pakistan) or at the Iceland hot spot. These eruptions produced thousands of km3 of lava and enormous amounts of ash. They could have affected global climate and ocean chemistry. • Both volcanic and meteorite impact hypotheses are viable mechanisms for causing the K/T mass extinction, although the latter is more popular... Major events of the Cretaceous Period References, web resources

• Stanley, Earth System History, chapter 17. • http://www.ucmp.berkeley.edu/mesozoic/cretaceous/cretaceous.html • http://www.bbc.co.uk/dinosaurs/fact_files/ • http://www.ucmp.berkeley.edu/diapsids/saurischia/theropoda.html • http://www.sino-collector.com/eng/_private/cjyd/zjlt/hjs-hs/hjs02-3.htm • http://www.palaeos.com/Mesozoic/Cretaceous/Cretaceous.htm • http://www.oceansofkansas.com/ • http://www.scotese.com/ • http://jan.ucc.nau.edu/~rcb7/globaltext2.html • http://www.nytimes.com/library/national/science/122199sci-archaeo- flowers.html • http://www.napa.ufl.edu/98news/flowerph.htm • http://www.colby.edu/~ragastal/Paleobotany/angiorigins.htm • http://www.pbs.org/wgbh/evolution/library/03/4/l_034_01.html