The Mesopotamians

It’s official; it is a year today since I wrote my first article on extinctions! To celebrate, I thought I would write about something a bit different and it is something I’ve wanted to write about for a while (but my trip to Germany (article about that soon) and exams has pushed me back a bit). Ancient history is a long period of time covering many different ages and civilisations, from the Early Bronze Age, 3300–1200 BC, to the Coming of Islam in 613CE. This article covers the Mesopotamians, who lived from 4000 B.C. to 332 B.C., when they became part of Alexander the Great’s empire.

 

The Mesopotamians are pretty well known as being the ‘cradle of civilisation in the West’ and included Sumer and the Akkadian, Babylonian, and Assyrian empires (modern day Iraq). The fact that this civilisation was wedged between two rivers (Tigris and the Euphrates) arguably allowed them to be so successful. This meant that the Mesopotamians could use the rivers’ banks for agriculture; irrigation and canals were built to control and direct the flow of water. This gave the people of Mesopotamia a constant and vast food source, allowing them to expand into cities. The climate that they lived in was semi-arid with lots of marshes, lagoons, mud flats and reed banks- a lot of these are opportune places for farming and agriculture. In these areas, nomads herded goats, sheep and camels all year round, moving from place to place with the seasons. The one down-side of this area is that it is lacking in precious metals, building stones and timber, so the people of this land traded with others, swapping their agriculture products for the building essentials they needed. They also frequently fished in the rivers, adding to their trading value. The demand for labour frequently led to drastic population increases.

meso geog

The Sumerians produced some of the earliest writing discovered, on baked clay tablets. However, this writing was not profound, merely tax and accounting records. But, this led to phonetic writing, where writing represented sounds, not objects. Semitic dialects were also spoken in Mesopotamia. Subartuan, a language of the Zagros, is attested in personal names, rivers and mountains and in various crafts. Akkadian came to be the dominant language during the Akkadian Empire and the Assyrian empires, but Sumerian was retained for administration, religious, literary, and scientific purposes. This led to widespread bilingualism. Libraries could be found in towns and temples during the Babylonian Empire and both men and women learnt to read and write. Many of this literature was translated from Sumerian, many of which is still studied today, the most famous of which is the Epic of Gilgamesh, telling the tales of Gilgamesh’s adventures.

epic of gilgamesh

Mesopotamian mathematics is the source of a 60-second minute, 60-minute hour, 24-hour day and 360-degree circle. Their calendar was based on a 7-day week and Babylonians also came up with theorems of many areas of shapes, which we still use today. They learnt how to mathematically predict eclipses and Mesopotamian astronomers used a 12-month calendar based on the cycles of the moon. The origins of astrology and astronomy date from this time. There were only two seasons to Mesopotamians- summer and winter. They used many technologies, such as copper-working, glass making, water storage and textile weaving. opper, bronze, and iron were used for armour as well as for different weapons such as swords, daggers, spears and maces.

 

Mesopotamia also led to possibly the first organised religion, which has led to many beliefs and tales (The Fourth Kind ring any bells?). They believed that the world was flat, surrounded by water and the heavens above. Their polytheistic beliefs had regional variations; the Sumerians believed that Enlil was the most powerful god. He was the chief god of the Pantheon. This religion also led them to think philosophically (Babylonian logic is thought to have greatly influenced Early Greek philosophy).

 

 

Festivals and music were also a key part of their lives, mostly linked to religion and the gods. Hunting, boxing and wrestling were very popular sports, along with a form of polo, but riders would play on the backs of other men instead of horses. Although this is one of the oldest civilisations, there are many aspects which are very similar to modern civilisations. One can see why Mesopotamia was known as the ‘cradle of civilisation’.

mesopotamian goddess

These are just some of the key points of the Mesopotamians. I have focused mostly on what the Mesopotamians brought to future civilisations, such as maths, phonetics and organised religion, rather than their general lifestyles. If you want to research more, click and follow the links below!

 

 

Find out more: http://history.howstuffworks.com/history-vs-myth/mesopotamia-cradle-of-civilization2.htm

http://fax.libs.uga.edu/DS69x5xH236M/

http://en.wikipedia.org/wiki/Mesopotamia

http://books.google.co.uk/books?id=nAemO6HmOgYC&pg=PA2&redir_esc=y#v=onepage&q&f=false

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Modern-Day Extinctions

I know this may be a controversial one, but mass extinctions change the world’s ecosystem drastically and sometimes take the Earth millions of years to recover. But these mass extinctions have always been because of natural disasters; meteors, volcanoes, sea level fall…until now. Every year, countless amounts of species are wiped out because of humans, so much so that some are now labelling our time ‘the 6th mass extinction’. Here are just a few of the organisms that have been wiped out due to the world’s most dangerous predator- us. (By the way I’m not writing about the Dodo. I feel that everyone knows about this animal and I wanted to write about something a bit different).

 

Steller’s sea cow

Sea cows, manatees and dugongs are a group of fully aquatic herbivorous mammals that are part of the order Sirenia, named because sailors thought they were mermaids, be it fat blubbery ones at that. Steller’s sea cow was the largest member of the order but within 27 years of discovery, in 1741, was hunted to extinction. This animal grew to at least 8m and could have either weighed 4 or 24.3 metric tons (the estimates contradict). According to Steller, who this animal was named after, this sea cow was completely tame and a slow swimmer, allowing it to be hunted so easily. Fossils indicate Steller’s sea cow was formerly widespread along the North Pacific coast, reaching south to Japan and California. It is thought that hunting was most likely done by aborigines living in these areas.

stellar sea cow

Atlas bear

The Atlas bear is an extinct subspecies of brown bear, or may have even been a completely different species. It was Africa’s only native bear to live to modern times, and lived in the Atlas Mountains of Libya and Morocco. It was brownish black and lacked a white muzzle, which, with its claws, was a lot shorter than those of the American black bear. These bears were hunted for sport, Roman games or used to execute prisoners of the Roman Empire. The last known specimen was killed in 1890 by hunters in the Rif Mountains of northern Morocco.

atlas bear

Moa

The Moa was a flightless bird, similar to an emu or ostrich, native to New Zealand. The largest reached to 3.6m tall and weighed about 230kg. It is generally considered that most, if not all, species of moa died out by 1400 CE due to overhunting by the Māori, a Polynesian tribe, and habitat decline. Before this, the moa’s only predator was the Haast’s Eagle. By about A.D. 1400, almost all moa were thought to have become extinct, along with the Haast’s Eagle, which had relied on them for food and this extinction is suggested to have taken less that 100 years.

moa

Hokkaidō wolf

This wolf is one of two extinct subspecies of the Japanese wolf. The other is the Honshū wolf. The Honshū wolf occupied the islands of Honshū, Shikoku, and Kyūshū in Japan. The Hokkaidō wolf was native to the island of Hokkaidō. The Hokkaidō wolf was a lot more wolf-looking than its also extinct cousin, with body dimensions similar to that of a grey wolf. The Hokkaidō wolf became extinct during the Meiji restoration period (a chain of events that restored imperial rule to Japan in 1868 under the Meiji Emperor). It was proclaimed that this was a threat to ranching and a chemical extermination campaign was introduced.

Hokkaidō wolf

Hokkaidō wolf

 

The Honshu wolf was fine until rabies was introduced into its habitat. Rabies, deforestation of the wolf’s habitat, and conflict with humans that led to their extinction. The last specimen was officially killed in 1905.

honshu wolf

Honshu Wolf

Eastern elk

This elk inhabited northern and eastern United States, and southern Canada. The last of its kind was shot in Pennsylvania on September 1, 1877. As people continued to settle into their habitat, elk populations decreased due to over-hunting and the loss of their dense woodland habitat. This extinct red deer subspecies has been gleaned from remains and historical references.

eastern elk

Laughing Owl

This owl was only found in 1840 in New Zealand but is now extinct. It was a plentiful owl at first, but many were sent to British museums to be scientifically identified and studied. The species was becoming rare in 1880 and the last specimen was found dead in 1914. The overall extinction of this animal was due to the want for specimens, land use changes, and the introduction of cats and stoats. Its length was 35.5–40 cm, wing length 26.4 cm. Males were smaller than females. They weighed around 600 grams.

laughing owl

Yangtze River dolphin

The baiji was found in the Yangtze River and was eventually killed off by overfishing in the river, transportation and the river’s use for hydroelectricity. Efforts were made to conserve the species, but a late 2006 expedition failed to find any baiji in the river. The last living Yangtze River dolphin was Qiqi (淇淇), who died in 2002. Males were about 2.3 metres long, females 2.5 metres, the longest specimen 2.7 metres. The animal weighed 135–230 kilograms, with a lifespan estimated at 24 years in the wild. Because of its poor vision, the baiji relied mainly on sonar for navigation. Its population was estimated about 6000 individuals in the 1950s but only a few hundred were left by 1970. By 1997 there were only 13 dolphins left and is now extinct, even though there was a possible sighting in 2007. A baiji conservation dolphinarium was established at the Institute of Hydrobiology (IHB) in Wuhan in 1992 in a hope to preserve these animals. However, it did not prove to be very successful, with one captive individual, Su Su, only living for 17 days.

baiji

Small Mauritian flying fox

This is an extinct species of megabat that lived on the islands of Réunion and Mauritius that was nocturnal and fed on small fruit. As it roosted in old trees and caves, it was vulnerable to forest clearance and hunting. It probably vanished in the 19th century. A description by La Nux from 1772 states: “They are hunted for their meat, for their fat, for young individuals, throughout all the summer, all the autumn and part of the winter, by whites with a gun, by Negros with nets. The species must continue to decline, and in a short time… It used to be easy, as far as one can judge, to prevent these animals leaving, than to take them out alive one by one, or to suffocate them with smoke, and in one way or another discover the number of males or females of which the association was composed; I do not know any more about this species.”

flying fox

Western black rhinoceros

This extinct subspecies of the black rhino only went extinct in 2011. They once lived in sub-Saharan Africa but were killed off by poaching. It weighed 800–1,300 kg and had two horns, which were believed to contain medicinal properties, and this is where the heavy poaching began. Obviously, there is no scientific fact to back this notion up. The population of these rhinos rose in the 1930, when conservation was put in place. This was short lived; however, as protection efforts were neglected. Poaching continued and by the millennium, as little as 10 were left in the wild. Punishments for poaching were lacking; individuals caught poaching were never sentenced. The Western black rhinoceros was last seen in Cameroon 2006. It was declared officially extinct in 2011.

black rhino

These are just a handful of animals that have become extinct due to mankind. Since the 1500s at least 358 species of plants and animals have become extinct, changing their ecosystem and causing other individuals in their food chain to also become extinct or endangered. If that doesn’t sound like a mass extinction, I don’t know what does.

 

 

 

 

Blackburn, A. (1982): A 1927 record of the Laughing Owl. Notornis 29(1): 79.

Brett L. Walker, “Meiji Modernization, Scientific: Agriculture, and the Destruction of Japan’s Hokkaidō Wolf,” Environmental History, Vol. 9, No. 2, 2004.

Bruin: The Grand Bear Hunt, Mayne Reid, Ticknor and Fields, 1865

Knight, John (1997). “On the Extinction of the Japanese Wolf”. Asian Folklore Studies (Nanzan University) 56 (1): 129–159

Cheke, A. S.; Hume, J. P. (2008). Lost Land of the Dodo: an Ecological History of Mauritius, Réunion & Rodrigues. T. & A. D. Poyser. ISBN 978-0-7136-6544-4.

Largot, Isabelle. “Probable extinction of the western black rhino, Diceros bicornis longipes: 2006 survey in northern Cameroon”. PACHYDERM

Miller, Gerrit S (1918). “A new river-dolphin from China”. Smithsonian Miscellaneous Collections 68 (9): 1–12

 

Chinese River Dolphin (Baiji) Feared Extinct, Hope Remains for Finless Porpoise”. WWF. December 15, 2006. Retrieved December 15, 2006

“Eastern Elk: Are They Really Extinct?”

 

www.bearsoftheworld.net

www.dailytech.com

www.lhs204.stellpflug.com

www.petermaas.nl

http://www.radionz.co.nz/audio/soundarchives/feature/alice_mckenzie_and_the_moa

“Steller’s SeaCow”. Sirenian.org

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Europe’s Latest Predator!

A new apex predator has been found in Europe that was ten metres long! Torvosaurus gurneyi is Portugal’s answer to T. rex and lived in the Jurassic 150 million years ago. A lucky PhD student in Lisbon discovered this animal by studying bones that were misidentified as Torvosaurus tanneri, a related species that lived in North America’s Rocky Mountain region around the same time. The attributes that distinguish T. gurneyi from T. tanneri and the jaws and the tail vertebrae- the main one being that T. gurneyi had fewer teeth on the upper jaw.

torvosaurus skull

This megalosaur was named after palaeo-illustrator James Gurney and weighed roughly 4 to 5 tons. Strangely enough, megalosaurs are now thought to have‘fuzz’ over their skin; difficult to imagine a giant scary, yet fluffy predator. This giant creature had bigger arms than the famous T. rex, along with thick legs and elongated skull that allowed for a devastating bite. It appears that it did not ambush its prey, but simply used brute strength to kill and disembowel the unlucky victims.

Its claim to fame is that Torvosaurus gurneyi is Europe’s largest known land predator. It was probably so big simply because it lived in an all you can eat buffet environment of sauropods and stegosaurs.

torvosaurus face

Christophe Hendrickx, the main author of the paper said: “The teeth of the T. rex are more banana-shaped, while these are narrower, more blade-shaped.” Its large size is strange seen as, at the time, Europe was an archipelago, so only small animals have been previously found. Maybe it was this closed off environment that allowed Torvosaurus gurneyi to survive and thrive.

torvosaurus

 

http://news.nationalgeographic.com/news/2014/03/140305-dinosaurs-biggest-europe-torvosaurus-gurneyi-animals-science/

http://abcnews.go.com/Technology/remains-europes-biggest-dinosaur-predator-unearthed-portugal/story?id=22804810

portuguese-american-journal.com

topnews.us

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The Origin of Mammals

The evolution of mammals is an interesting one. Mammals are a very diverse group- from the smallest Bumble bee Bat, to us humans, to the largest Blue Whale- mammals have ventured to every habitat, even returning to the sea or learning to fly. But where did it all begin? Here I will tell their story, whilst describing some interesting individuals.

 

Mammals first evolved from a group of ‘mammal-like reptiles’ called synapsids. In fact, all mammals are included in the Synapsida as we have an inferior temporal fenestra in our skulls. The phrase “miss you like a hole in the head” works perfectly here, as it was the loss of other fenestra that allowed this group to evolve! It also allowed new jaw muscle attachment. Synapsids were the largest group of vertebrates in the Permian Age, about 299 to 251 million years ago and some made it through the Great Permian Extinction. However, after this mass extinction, archosaurs truly reigned supreme but synapsids were always there in the background.

Synapsidskull (2)

Synapsids are generally split into two groups; pelycosaurs and therapsids- the latter being the more advanced. ‘Pelycosaurs’ make up the six most primitive families of synapsids. They were all rather lizard-like, with sprawling gait and possibly horny scutes. The therapsids contain the more advanced synapsids, having a more erect pose and possibly hair, at least in some forms. The low-slung pelycosaurs have given rise to the more erect therapsids, who in their turn have given rise to the mammals.

images (2)

Archaeothyris and Clepsydrops, the earliest known synapsids, lived in the Carboniferous Period and belonged to the series of primitive synapsids. Archaeothyris was relatively large, measuring 50 centimetres head to tail. It was more advanced than early reptiles and could open its jaws very wide in comparison. Although its sharp teeth were all of the same shape, it did possess a pair of enlarged canines, suggesting that it was a carnivore.

Clepsydrops also had a diet of small animals and insects, as did most early synapsids. It too had advanced jaws but still possessed the need to lay eggs, unlike modern mammals that give birth to live young (apart from the platypus and the echidna). These pelycosaurs, along with Archaeothyris, grew and diversified so much that they became the largest terrestrial animals in the latest Carboniferous and Early Permian Periods, ranging up to 6 m in length! However, appearance-wise, these animals were nothing like the mammals we know today; they had a sprawled stance and they still had reptilian-like skin (but with some ‘fuzz’). The major difference is that they were still cold-blooded and still had very small brains. Some developed sails to help raise their body temperature, like Dimetrodon. Dimetrodon is often mistaken for some sort of dinosaur in pop culture, but it went extinct 40 million years before dinosaurs even existed. Most Dimetrodon species ranged in length from 1.7 to 4.6 metres and are estimated to have weighed between 28 and 250 kilograms. Unfortunately, by the middle of the Late Permian, all of the pelycosaurs had either died off or evolved into their successors- the therapsids.

Dimetrodon

The more advanced theraspids appeared in the Middle Permian and included meat and plant eaters. Moschops (no, it’s not a Pokémon) lived around 265–260 million years ago and was massive, roughly 2.7-metre-long. Due to the fact that it possessed long-crowned, stout teeth, it is believed that Moschops was a herbivore feeding on nutrient-poor and tough vegetation and probably had to feed very frequently.

Moschops11DB

 Theraspids fell victim to the Great Permian Extinction, with only a few making it through. One synapsid that flourished in the Triassic was Cynognathus-a meter-long predator. It had a particularly large head, 30 centimetres in length, with wide jaws and sharp teeth. Its hind limbs were placed directly beneath the body, but the fore-limbs sprawled outwards in a reptilian fashion. The lack of ribs in the stomach region suggests the presence of an efficient diaphragm, which is an important muscle for mammalian breathing. These creatures were accompanied with archosaurs, (who would give rise to the dinosaurs) who very often overshadowed theraspids.

Cynognathus

There are three groups within the Triassic theraspids: dicynodonts were beaked herbivores; cynodonts were more mammal-like and had a range of diets and therocephalians were carnivores with large skulls. Unlike the dicynodonts, which remained large, the cynodonts became progressively smaller and more mammal-like as the Triassic progressed. The first mammaliaforms evolved from these during the Late Triassic. During the Jurassic and Cretaceous, the remaining nonmammalian cynodonts were small, such as Tritylodon. This creature was one of the most advanced groups of cynodonts. They were about 0.3m long and had a diet much like that of a modern-day rodent and even burrowed like rodents. There were large incisors at the very front of their mouth separated by a gap from the rest of the teeth. Even with their mouth closed the incisors would still stick out slightly visible. The legs were directly beneath the body like mammals, unlike the earlier therapsids with sprawling limbs. They still laid eggs but were now warm blooded.

tritylodon

These animals that lived during the Triassic and Jurassic had high metabolic rates, so they had to eat a lot of food. Therefore, they evolved the ability to chew and their teeth developed to assist them with rapid digestion. Limbs, which were previously sprawling to the side, moved underneath the body, allowing them to breathe more easily when moving.

tetrapoda.clad

Carroll, R.L. (1969). “Problems of the origin of reptiles”. Biological Reviews 44 (3): 393–432

Kardong, K.V. (2002): Vertebrates: Comparative anatomy, function, evolution. 3rd Edition. McGraw-Hill, New York

Ji, Q.; Luo, Z-X, Yuan, C-X, and Tabrum, A.R. (February 2006). “A Swimming Mammaliaform from the Middle Jurassic and Ecomorphological Diversification of Early Mammals”. Science 311 (5764): 1123–7. See also the news item at “Jurassic “Beaver” Found; Rewrites History of Mammals”.

Ruben, J.A.; Jones, T.D. (2000). “Selective Factors Associated with the Origin of Fur and Feathers”. Amer. Zool. 40 (4): 585–596

Carroll, R. L. (1988), Vertebrate Paleontology and Evolution, WH Freeman & Co.

Lambert 2001: 68-69.

Modesto, Sean P.; Smith, Roger M. H.; Campione, Nicolás E.; Reisz, Robert R. (2011). “The last ‘pelycosaur’: a varanopid synapsid from the Pristerognathus Assemblage Zone, Middle Permian of South Africa”. Naturwissenschaften 98 (12): 1027–34.

Bramble and Jenkins 1994.

Laurin, M.; and Reisz, R.R. (2011). “Synapsida. Mammals and their extinct relatives”. The Tree of Life Web Project. Retrieved 26 April 2012.

Kemp, T.S. (2011). “The origin and radiation of therapsids”. In Chinsamy-Turan, A. (ed.). Forerunners of Mammals. Bloomington: Indiana University Press. pp. 3–30

Benson, R.J. (2012). “Interrelationships of basal synapsids: cranial and postcranial morphological partitions suggest different topologies”. Journal of Systematic Paleontology

 

www.luisrey.ndtilda.co.uk

www.hronoblog.com

 

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The Best Dino-discoveries of 2013

Seen as it’s coming up to Christmas and the New Year, I thought I would do a list of the best dinosaur-related discoveries of the year. I have chosen these either because they are an important scientific discovery, or just because I think they’re cool. I will go in chronological order. Enjoy!

 

 

1)      Oldest DinoEggs: At the beginning of April it came out that there had been some wonderful new discoveries of dinosaur embryos in China. China and Mongolia have been at the forefront of dinosaur discoveries for more than a decade now, so this wasn’t surprising. The whole site contained 190 million year old eggs, the oldest egg shells ever known, with non-avian dinosaur embryos inside (poor babies). The study that followed was the first of its kind and showed how dinosaur embryos grew and there was also preserved collagen in the baby bones- which is pretty exciting discovery. The dinosaurs inside turned out to be herbivorous sauropods Lufengosaurus, which was common to the area during the Jurassic period.

egg baby

Read more at http://news.discovery.com/animals/dinosaurs/dinosaur-organic-remains-and-embryos-found-130410.htm

Image from: www.mnn.com

 

2)      Doggy-paddling Dino: I put this in here because it’s interesting and a bit strange. It’s odd to think that dinosaur could have possibly behaved like modern-day mammals, especially domesticated ones like dogs. Surprise, surprise, this discovery was yet again found in China, also in April. The discovery was from a 100 million year old river bed in the Szechuan Province showing claw and scraping marks on the bottom. Stretching over a distance of 50 feet (15 meters), the markings show that the dinosaur had a coordinated, left-right, left-right swimming style. It’s rather difficult from scrape marks alone to determine what dinosaur this was, but the culprit is suspected to be an early tyrannosaur or a Sinocalliopteryx; predators known to have roamed this prehistoric landscape in China. Apparently, this river was like a ‘dinosaur highway’ where many dinosaurs would traipse up for long distances.

doggy paddle

Read more at: http://www.livescience.com/28572-dinosaur-doggy-paddle.html

Image by: Nathan E. Rogers

 

3)      House-cat Dinosaur?! Yet again in China and in April, new discoveries of Microraptor suggest that it hunted like a domestic cat and ate fish, 120 million years ago. Its gut contents consisted of many broken up bones of fish. Its teeth were perfectly designed for eating fish- they were serrated just on one side and were also angled forward. This little dino could then impale fish on its teeth without ripping the fish apart during the inevitable struggle. Now it’s known that Microraptor operated in a varied terrain, hunting different types of prey. Clearly fish was its favourite, but other evidence suggests it also gobbled up birds and terrestrial animals about the size of squirrels.

microraptor

 

Read more at: http://news.discovery.com/animals/dinosaurs/fish-eating-dinosaur-130424.htm

Image from: news.softpedia.com

 

4)      World’s Oldest Known Birds: Lots of people think that dinosaurs and birds are completely different animals, but they are not, birds are dinosaurs and that’s just something we’re going to have to live with. And it often gets very difficult to decide when ‘dinosaur’ ends and ‘bird’ begins (take our friend Microraptor for example). In May a new species has knocked Archaeopteryx off the top spot for being the Earth’s Oldest Bird. Aurornis xui is a 160 million year old feathered dinosaur/bird from, you guessed it…China. It looked like a ground bird, but with a long tail, clawed hands and toothed jaws and came from the Tiaojishan Formation of Liaoning Province in north-eastern China. The fossil is excellently preserved and has clear feather impressions.

1st bird

Read more: http://news.discovery.com/animals/dinosaurs/worlds-oldest-known-bird-1305291.htm

Image by: Jonica Dos Remedios/Claude Desmedt/IRSNB

 

5)      The Mystery Nose: In July in North America (finally, somewhere other than China!) a dinosaur with long horns and a giant nose was unearthed in Utah. The dinosaur, Nasuceratops titusi, aka “Big Nosed Horned Faced,” measured about 15 feet long and weighed about 2.75 tons. This creature lived approximately 76 million years ago and its huge nose remains a mystery. However, it is suspected that its nose was nothing to do with a heightened sense of smell, since olfactory receptors occur further back in the head, adjacent to the brain. This dinosaur was a plant eater and a close relative of our friend Triceratops (Ps, stay tuned for some shocking news about him!). The amazing horns of Nasutoceratops were most likely used as visual signals of dominance and, when that wasn’t enough, as weapons for combating rivals.

big nose

Read more: http://news.discovery.com/animals/dinosaurs/newly-found-american-dinosaur-had-big-nose-huge-horns-130716.htm

Image from: gsenm.org

 

6)      Stiff Necks: A study in mid-August proves that long-necked sauropods had stiffer necks than previously thought. Researchers analysed the movements of ostrich necks in order to gain insight into how long-necked dinosaurs may have moved. It turns out that they probably couldn’t swivel their necks round or even move their heads from ground to treetop. The cartilage and soft tissue of an ostrich neck actually reduces its flexibility, so it is most likely this is the same in long-necked dinosaurs. They probably had to move their large, lumbering bodies a fair amount to access the 880 lbs. (400 kilograms) of food they ate daily. However, more work needs to be done on perhaps giraffes so that the two can be compared.

long necks

 

Read more: http://www.livescience.com/38895-sauropods-had-stiff-necks.html

Image from: www.bbc.co.uk

 

7)      Arctic Footprints: In September a possible new major dinosaur site was found in Alaska near the Tanana and Yukon rivers. Researchers brought back 2,000 pounds (900 kilograms) of dinosaur footprint fossils, an abundance never seen before. They found a great diversity of dinosaurs; evidence of an extinct ecosystem previously unknown to us. The tracks were preserved in natural casts after they had stepped in mud. There is a lot more work to be done on these footprints, so look out for a lot more findings and discoveries to come!

footprint

Read more: http://news.discovery.com/animals/dinosaurs/yukon-dinosaur-tracks-130925.htm

Image by: Pat Druckenmiller

 

8)      King of Gore: In early November, a new discovery of an early T .rex was found. Lythronax argestes, literally ‘King of Gore’ lived in south Utah, in the Late Cretaceous 80 million years ago. Its forward-facing eyes, powerful limbs and large size would have made it an efficient hunter of both duckbilled dinosaurs and horned dinosaurs. Lythoranx also had knife-edged teeth and powerful jaws and would have allowed it to carve out huge chunks of flesh and swallow bone whole. Lythronax is most closely related to T. rex and another dinosaur known as Tarbosaurus bataar however it was smaller than T. rex, reaching 30 feet in length and weighed about 3 tons.

king of gore

Read more: http://news.discovery.com/animals/dinosaurs/toothy-dino-terrorized-utah-before-t-rex-131106.htm

Image from: www.theguardian.com

 

9)      Entombed Baby Dino: At the beginning of December a baby dinosaur fossil was found that was so complete, it was almost lifelike. It is the first Chasmosaurus belli baby fossil and was entombed in the rock which preserved it. This baby lived 72 million years ago and was thought to be three years old when it drowned. This specimen was found in Alberta’s badlands at a place called Dinosaur Provincial Park and was fully intact minus the arms. Researchers hope to study the remains to determine how dinosaur skin ages, and to help solve other palaeontological mysteries.

baby dino

 

Read more: http://news.discovery.com/animals/dinosaurs/baby-dinosaur-fossil-so-intact-its-lifelike-131202.htm

Image from: www.lostateminor.com

 

10)      Goodbye Childhood: Triceratops is one of the most well-known and probably one of the most loved dinosaurs. Now what if I told you that it was all a lie and Triceratops probably wasn’t real? Crushed? Palaeontologists at the Montana State University argue that the Triceratops and its cousin, the Torosaurus, was actually the same dinosaur at different stages of growth. Triceratops had three facial horns and a short, thick neck-frill with a saw-toothed edge. Torosaurus also had three horns, though at different angles, and a much longer, thinner, smooth-edged frill with two large holes in it. Marsh, who discovered both in the late 1800s, considered them to be separate species, probably because he was in a race with Cope to discover as many dinosaurs as possible. There isn’t a whole Triceratops fossil, so Marsh made many assumptions and even used different creatures’ bones to complete specimens. This is an ongoing investigation but I think one of the most important of this year. You may be pleased to know, however, that Torosaurus may be the name getting the boot, not Triceratops, so we don’t have to mourn just yet.

tritoro

 

Read more: http://www.cbsnews.com/news/scientists-triceratops-may-not-have-existed/

Image from: www.design-laorosa.com

So that was my top ten best and most important discoveries of 2013. I’m sure there will be many more to come and I hope you agree with my choices. Merry Christmas and a Happy New Year!

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They did it on Porpoise

 

Cetaceans are an order of animals that include all whales, dolphins and porpoises. They are secondarily aquatic mammals, their ancestors once walked on land; they need to return to the surface to breathe air; they have a pentadactyl limb in the form of flippers and their spines move vertically, rather than side to side. All these features indicate that they indeed are highly derived mammals. Most species are marine, although some dolphin species are found in the Yangtze, Amazon, Paraná, Indus and Ganges Rivers. They have streamlined bodies with highly compressed neck vertebrae, dorsal fins and a tail with two finlike flukes arranged horizontally. Modern whales have greatly elongated anterior skull bones, and the nostrils are located on the top of the head, forming the blowhole. The forelimbs are specialized to form flippers, and the hind limbs and pelvis are extremely small and do not normally extend out of the body wall of the animal (Slijper, 1979). The mystery of how these creatures returned to the sea began to unravel when discoveries were made in the late 1970s, revealing several stages in the transition of cetaceans from land to sea.

whales

The evolution of cetaceans was once thought to originate with mesonychids, an extinct taxon of carnivorous ungulates, which resembled wolves with hooves. These first appeared in the Early Palaeocene and saw a sharp decline at the end of the Eocene. The last genus to go extinct was Mongolestes, who went extinct in the Early Oligocene. Mongolestes is found in the Ulan Gochu formation of Inner Mongolia. This is different to other mesonychids in several dental features, including the loss of the M3, a mandibular symphysis that is steeper and overall large teeth (Szalay and Gould, 1966). Below you can see a restoration along side the fossil of this animal’s jaw. Notice the large canines and the steep mandibular symphysis.

mong

The most primitive mesonychid, Yangtanglestes, is known from the early Palaeocene of Asia (Jehle, Martin, 2006).  These creatures were most likely the dominant predator of Palaeocene Asian environments. However, one genus seemed to have migrated to Europe and North America successfully; Dissacus has been found all over the northern hemisphere (Jehle, Martin, 2006). The fossil record of the European Dissacus, Dissacus europaeus, is fragmentary and includes a mandible, a complete radius and fragments of a humerus. A morphological study of these bones suggests this animal was digitigrade and more cursorial than is usually assumed for the genus. You can see here the fossil mandible.

dissacus

Mesonychids possessed triangular molar teeth, similar to that of whales and dolphins, as well as many other morphological traits. This is why it was believed that mesonychids were direct ancestor of the Cetacea. However, the discovery of preserved hind limbs of ancient cetaceans (Geisler, and Uhen, 2003) now indicate that cetaceans are more closely related to hippopotamids and other ancient whales, than they are to mesonychids (Boisserie et al., 2005). Most palaeontologists now agree that whales probably did not evolve from mesonychids; it is now suggested that whales descended from, or share a common ancestor with the anthracotheres– semi-aquatic hippo ancestors (Geisler, Theodor, 2009).

skulls

Skulls of a 9 million-year-old anthracothere, Merycopotamus medioximus, from Pakistan’s Siwalik Hills (above) and a contemporaneous fossil hippopotamus (Hexaprotodon sivalensis) from the same area exhibit many similarities, including the eye socket, which protrudes above the skull to let the animals see above water while most of their head is submerged. (Anthracothere skull courtesy of Harvard University & Geological Survey of Pakistan; hippo skull from the Natural History Museum, London)

 The oldest genus appeared in the Asian Eocene. After this, they thrived in Eurasia and Africa and even some entered North America in the Oligocene. They saw their demise in the Miocene, probably due to climate change and competition (Lihoreau et al., 2006). There is very little fossil evidence that shows these are the true ancestors of whales. What fossil evidence does show, however, is that they are related to hippos. Below is an image of a Microbunodon skull, an ancestor of modern hippopotamuses. You can see that there are several similar features in the lower jaw, such as the structure of their premolars. The palaeoenvironment that Microbunodon was found in, indicated that this animal was amphibious, just like modern hippos. Gene sequencing now gives us evidence that hippos are close living relatives of whales (Gatesy,1997). Therefore, anthracotheres are ancestors of whales also. Nevertheless, the earliest known anthracotheres appear in the fossil record in the middle Eocene, a long time after archaeocetes became aquatic. Cetaceans arose about 50 million years ago in Asia, whereas the family Hippopotamidae is only 15 million years old (Thewissen et al., 2007); clearly there are still a lot of gaps and unanswered questions in this area.

hippo jaw

  To add to this, there was still not enough strong evidence for a clade combining cetaceans and even-toed ungulates, until the discovery of Pakicetus in 1981. It was found in the Eocene of Pakistan and most palaeontologists consider it to be the most basal whale. The first fossil was an incomplete skull cap and a broken mandible with some teeth. The molars preserved show that this animal could tear flesh and scrapes on the teeth suggested that the food was ground and chewed (Madar, 2007). The key characteristic that links this animal to cetaceans is the large auditory bulla; it is formed from the ectotympanic bone only. The bulla is the bone of the skull that forms the floor of the cavity that houses the middle ear ossicles (Thewissen and Hussain, 1993). The thickened part of the auditory bulla was suspended from the skull, allowing it to vibrate in response to sound waves. Underwater sound would have entered the skull of Pakicetus and caused its bulla to vibrate. The bulla was in turn connected to the chain of middle ear bones, which transmitted the sound to the organ of hearing. Thus the thickened bulla of Pakicetus is interpreted as a specialization for hearing underwater sound.

Pakicetus is the only cetacean in which the mandibular foramen is small, as is the case in all terrestrial animals. It thus lacked the fat pad, and sounds reached its eardrum following the external auditory meatus as in terrestrial mammals. Thus the hearing mechanism of Pakicetus is the only known intermediate between that of land mammals and aquatic cetaceans.” (Thewissen and Hussain, 1993).

Auditory bulla

Auditory bulla that is only loosely attached to the rest of the skull. http://www.geol.umd.edu

Following this, proto-whales had to make the transition from terrestrial and fresh water environments, to fully marine. Ambulocetus natans was discovered in Pakistan and could walk as well as swim. The fossils of ambulocetids are always found in near-shore shallow marine deposits associated with abundant marine plant fossils and littoral molluscs (Thewissen et al., 2002). Its back legs were better equipped for swimming and chemical analysis of its teeth shows that it was able to move between salt and fresh water (Thewissen et al., 1996). Ambulocetus is considered as an early whale because it had an adaptation in the nose that enabled it to swallow underwater and its periotic bones had a structure like those of whales, enabling it to hear well underwater. In addition, its teeth are similar to those of early cetaceans. The mandibular foramen in ambulocetids had increased in size, indicating that a fat pad was likely to be housed in the lower jaw. In modern whales, this fat pad in the mandibular foramen extends posteriorly to the middle ear. This allows sounds to be received in the lower jaw, and then transmitted through the fat pad to the middle ear (Thewissen, 2001). Also, they probably swam by pelvic paddling and caudal undulation. (Thewissen, 1997). Whales swim by caudal oscillation, which is more energy efficient, but this is a clear intermediate stage.

Ambulocetus

  Approximately 48 to 35 million years ago, a diverse and heterogeneous group lived in Eurasia, North America and Africa. Protocetids, unlike earlier cetaceans, include open marine forms (Thewissen and Williams, 2002). These were also the first whales to leave India and disperse to all shallow subtropical oceans of the world (Thewissen and Williams, 2002). It has been suggested that these creatures were still amphibious; this is supported by the discovery of a pregnant Maiacetus fossil, in which the fossilised foetus was positioned for a head-first delivery- suggesting it gave birth on land (Gingerich et al., 2009). Whales generally give birth tail first, whilst land mammals give birth head first. This suggests that this animal would go back and forth to the ocean, like a sea lion. However, J. G. M. Thewissen has questioned this, suggesting that the smaller skeleton could be a partially digested meal. Even if the small skeleton is a foetus, Thewissen writes that it may not have been preserved in its normal in-vivo position (Thewissen and McLellan, 2009). These animals’ orbits moved to the sides of the head and increased in size- suggesting that it caught underwater prey, and are similar to the eyes of modern cetaceans (Thewissen et al., 2001). The nasal openings were also now positioned halfway up the snout and their teeth were varied, showing a broad diet (Fordyce and Barnes; 1994). The external ear canal, which is missing in modern cetaceans, is present here. Hence, the method of sound transmission present in them combines aspects of pakicetids and modern toothed whales (Nummela, 2004).

Maiacetus

Adult female and fetal (in blue) Maiacetus

Rodhocetus

It is possible that some protocetids had flukes. However, it is clear that they are adapted even further to an aquatic life-style. But, the pelvis was still connected to one of the sacral vertebrae. The ungulate ancestry of these early whales is still underlined by characteristics like the presence of hooves at the ends of the toes in animals such as Rodhocetus. Terrestrial locomotion of Rodhocetus was very limited due to their hindlimb structure. It is thought that they moved in a way similar to how eared seals move on land.

Basilosaurids were initially mistaken for reptiles, hence the name. These lived in the late Eocene and are the oldest obligate aquatic cetaceans (Thewissen et al., 2001). Basilosaur fossils are usually found in fully marine deposits lacking any freshwater influx. Basilosaurus is significant because it is known to have retained small but well-developed hind limbs that projected from the body, although there was no joint between the pelvic bones and the vertebrae. Living whales retain only tiny splint-like bones as remnants of the pelvis and hind limbs (Gingerich et al., 1994). Modern toothed whales have a melon in their skulls- a mass of fat tissue found in the forehead that is focus and modulate the animal’s vocalisations, which basilosaurids did not have. Basilosaurs also had a smaller brain, suggesting that these animals did not have social skills, like modern Cetacea. In 2011, Fahlke et al. concluded that Basilosaurus’ skull was asymmetrical, just like modern toothed whales, and not symmetrical like in baleen whales and artiodactyls. This asymmetry is associated with high-frequency sound production and echolocation, neither of which is thought to present in Basilosaurus. This cranial torsion probably evolved in protocetids and basilosaurids together with directional underwater hearing and the sound receiving apparatus in the mandible (Falke et al., 2011). Basilosaurs could also hear directionally in water and the ear is much more derived than that of its ancestors. They did, however, have a large external auditory meatus, which is very much reduced in modern cetaceans (Nummela et al., 2004). The anatomy of this creatures tail, suggests there was probably a fluke, which would have aided vertical motion and restoration either show a small dorsal fin or ridge.

basil skull

Skull and neck of Basilosaurus as reconstructed by Gidley 1913. Notice the heterodont teeth. The synapomorphic cetacean air sinus system is partially present in basilosaurids, including the pterygoid, peribullary, maxillary, and frontal sinuses.

basilosaur

Restoration of Basilosaurus cetoides from carnivoraforum.com . It has an elongate, eel-like body with a fluked tail.

As previously mentioned, toothed whales, or the Odontocetes, have the ability to echolocate by creating clicks at different frequencies and this is what the melon in the forehead is used for. The first fossil evidence of this is in the skull of a 33-14 million year old Squalodon (below is a partial skull of Squalodon bariensis). This animal shows both ancestral and modern features, the teeth being the most ancestral; they are widely spaced apart; their cheek teeth are triangular and serrated for grasping and cutting. In comparison to toothed whales at that time, the squalodontids were likely more mobile. It is believed that the dorsal fins were reduced but larger than that of the ancestors (Kowinsky, J.). Squalodontids also possessed many modern features. Their crania were well compressed, their rostrums were telescoped outward, and their skulls show proof of the origin of echolocation (Kowinsky, J.).

Squalodon   All modern whales are split into two subgroups- the Odontoceti, or the toothed whale, and the Mysticeti, or the baleen whales. Odontocetes have numerous, peg like teeth, although sometimes this is modified, such as the narwhals tusk. Examples of odontocetes are Dolphins, porpoises, belugas, narwhals, killer whales, sperm whales, and beaked whales. Baleen whales lack teeth completely as adults. They feed by straining small marine organisms out of the water using plates of baleen- a hornlike substance that forms filaments that hang down from the roof of the mouth. Blue, right, humpback, minke, gray, and fin whales are well-known examples of baleen whales. Some baleen whales, most famously the humpack whales, are known for the strange and complex songs they produce; their function is not clear, but unlike toothed whales, baleen whales do not use their songs for echolocation (Feldhamer et al., 1999). Different baleen whales use their baleen for different methods of feeding such as gulp-feeding with balaenopterids, skim-feeding with balaenids, and bottom plowing with eschrichtiids. Some members of modern baleens appeared in the middle Miocene. The demise of archaic forms and the radiation of modern ones may have been due to a change in ocean current and temperature. The early baleen whales still had teeth and a baleen and Aetiocetus cotylalveus is considered to have the transition between teeth and the baleen (Fordyce, 1998).

Aetiocetus

Aetiocetus skull, evolution.berkeley.edu

Another transitional feature is that the blowhole was located half way up its snout, rather than on the top of its head (Berkeley University, 2008). The genus, though more cranially reminiscent of archaic whales, with its pronounced snout and flat cranium, had a loose jaw like later baleen whales (Wallace, 2007). Fossil evidence of Janjucetus hunderi showed that baleen whales were predators, feeding on squid, fish and dolphin-like cetaceans, and that they evolved into gentle, toothless whales. The first true toothless baleen whales appeared in the late Oligocene and lacked the ability to echolocate.

whale line

During the Miocene, echolocation developed into its modern form and lots of dolphin-like fauna flourished. Early dolphins belong to Kentriodontidae, which were small to medium-sized toothed cetaceans with largely symmetrical skulls, and thought likely to include ancestors of some modern species. In October 2006, an unusual bottlenose dolphin was captured in Japan with small fins on each side of its genital slit, which scientists believe to be an unusually pronounced development of these vestigial hind limbs (Lovett, 2006).

The sad part is that this dolphin was found in Taji, an area notorious for dolphin fishing. This poor dolphin was sent straight to the ‘whale museum’.

poor dolphin

  The evolution of cetaceans seems to have an excellent fossil record, apart from linking them to hippo ancestors. Luckily, genetic information has bridged this gap. All whales differ from land mammals in having ear bones encased in structures attached to their jaws only by a flange of bone. This lets them perceive underwater sounds, an incredible adaptation for underwater life. Ceteacea are overall very well equipped for an aquatic lifestyle; their bodies are padded out and streamlined, they have lost substantial body hair and they have developed a fluke at the end of their tail, allowing them to swim with great energy efficiency. Some of the fossil ancestors of these creatures were thought to be sea serpents, but, after studying their clearly mammalian teeth and even a preserved pregnant ancestor, it is obvious that these creatures returned to the sea after millions of years on land. Even in modern whales and dolphins, we can still find the reduced pelvis and hind limbs- remnants of their terrestrial past.

 whale cladogram

Cladogram of Cetacea within Artiodactyla

http://phys.org/news2806.html

Geisler, J.H., Theodor, J.M., 2009. Hippopotamus and whale phylogeny. Nature 458:E1-E4

Lihoreau, Fabrice and Jean-Renaud Boisserie, et alia. (2006). “Anthracothere dental anatomy reveals a late Miocene Chado-Libyan bioprovince” (PDF). Proceedings of the National Academy of Sciences 103

 

Gatesy, J. (1 May 1997). “More DNA support for a Cetacea/Hippopotamidae clade: the blood-clotting protein gene gamma-fibrinogen”. Molecular Biology and Evolution 14 (5): 537–543.

Thewissen, JGM; Cooper, Lisa Noelle; Clementz, Mark T; Bajpai, Sunil; Tiwari, BN (20 December 2007). “Whales originated from aquatic artiodactyls in the Eocene epoch of India”. Nature 450 (7173): 1190–4.

Madar, S. I. 2007. The postcranial skeleton of early Eocene pakicetid cetaceans. Journal of Paleontology 81:176-200.

Thewissen, J.G.M and Hussain, S.T. 1993. Origins of underwater hearing in whales. Nature 361:444-445.

Thewissen, J. G. M.; Williams, E. M. (1 November 2002). “THE EARLY RADIATIONS OF CETACEA (MAMMALIA): Evolutionary Pattern and Developmental Correlations”. Annual Review of Ecology and Systematics 33 (1): 73–90.

Thewissen, J.G.M.; Madar, S.I.; Hussain, S.T. (1996). Ambulocetus natans, an Eocene cetacean (Mammalia) from Pakistan. Courier Forschungsinstitut Senckenberg 191. pp. 1–86.

THEWISSEN, J. G. M.; BAJPAI, SUNIL (1 January 2001). “Whale Origins as a Poster Child for Macroevolution”. BioScience 51 (12): 1037.

Thewissen, J. G. M; F.E.Fish (8 1997). “Locomotor Evolution in the Earliest Cetaceans: Functional Model, Modern Analogues, and Paleontological Evidence”. Paleobiology 23: 482-490.

Gingerich PD, ul-Haq M, von Koenigswald W, Sanders WJ, Smith BH, et al. “New Protocetid Whale from the Middle Eocene of Pakistan: Birth on Land, Precocial Development, and Sexual Dimorphism”. PLoS one. Retrieved 2009-02-04.

J. G. M. Thewissen and William A. McLellan (2009) Maiacetus: displaced fetus or last meal? PLoS ONE.

THEWISSEN, J. G. M.; BAJPAI, SUNIL (1 January 2001). “Whale Origins as a Poster Child for Macroevolution”. BioScience 51 (12): 1037.

Fordyce, R E; Barnes, L G (30 April 1994). “The Evolutionary History of Whales and Dolphins”. Annual Review of Earth and Planetary Sciences 22 (1): 419–455.

Nummela, Sirpa; Thewissen, J. G. M., Bajpai, Sunil, Hussain, S. Taseer, Kumar, Kishor (11 August 2004). “Eocene evolution of whale hearing”. Nature 430 (7001): 776–778.

J. G. M. Thewissen, E. M. Williams, L. J. Roe and S. T. Hussain (2001). “Skeletons of terrestrial cetaceans and the relationship of whales to artiodactyls”. Nature 413 (6853): 277–281

Fahlke, Julia M.; Gingerich, Philip D.; Welsh, Robert C.; Wood, Aaron R. (2011). “Cranial asymmetry in Eocene archaeocete whales and the evolution of directional hearing in water”. PNAS 108 (35): 14545–14548

On the systematic position of the species of Squalodon and Zeuglodon described from Australia and New Zealand

TS Hall – Proceedings of the Royal Society of Victoria, 1911

“The Origins and Adaptations of Mysticetes”. Robert Ewan Fordyce. 1998-06-07.

“Lines of Evidence:Transitional Forms (1 of 2)”. Understanding Evolution. Berkeley University. Archived from the original on 18 April 2008.

Neptune’s Ark: From Ichthyosaurs to Orcas By David Rains Wallace. Published 2007 University of California Press

Lovett, Richard A. (8 November 2006). “Dolphin With Four Fins May Prove Terrestrial Origins”. National Geographic. Retrieved 27 July 2012.

Szalay, Frederick S.; Gould, S. J. (1966). “Asiatic Mesonychidae (Mammalia, Condylarthra)” (PDF. 37Mb). Bulletin of the American Museum of Natural History 132 (2). Retrieved August 2013.

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www.morphobank.org

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Slijper, E.J. 1979. Whales. 2nd ed. Cornell University Press, Ithaca, New York.

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Greenhouse Cretaceous Climates

‘The Cretaceous Greenhouse World’ refers to a part of geological history that lasted from about 110 to 90 million years ago. During this period, submarine volcanic carbon dioxide emissions were released high enough to cause atmospheric CO2 concentrations in excess of 1000ppm. (Caldeira, K.,Rampino, M.R., 1991) This then caused rapid sea-floor spreading and the break up of continents. This lasted for ten million years and the global warming led to major radiation in the diversity of flowering plants, insects, birds and mammals. At the beginning of the Cretaceous, the super-continent, Pangaea, had broken up into two continents; the northern one being Laurasia and the southern one being Gondwana, which intern broke up even further into Africa, South America, India, Antarctica, and Australia. The Gondwanan break-up led to an increase in seaways and shorelines, which may have affected the diversification of terrestrial plants and animals by creating several isolated continental regions. (Lovett, Richard, 2008)

greenhouse cretaceous

Wonderfully preserved forminifera from the low-latitude Demerara Rise, mid-latitude Blake Nose and the high-latitude Falkland Plateau in the Atlantic Ocean, have been especially useful for reconstructing temperature gradients of the mid to Late Cretaceous ocean. The isotopic readings of surface-dwelling planktic forams, sea surface temperatures reached a maximum of 42˚C at the Demerara Rise (Bice et al., 2006), 33°C at the Blake Nose (Huber et al., 2002), and 31°C at the Falkland Plateau (Huber et al., 2002; Bice et al., 2003) during the Turonian, which was approximately 93–89 million years ago. It seems that Cretaceous warming was more prominent at the higher latitudes, where the different between the mid-Cretaceous temperature and now is almost 30˚C.

Using a more recent climate model, Bice et al. (2006) conclude that 3500 ppm or greater atmospheric CO2 concentration is required to reproduce the estimated maximum sea surface temperatures of the Mesozoic tropical ocean. Mesozoic palaeotemperatures are based on geochemical proxies and are still insufficient in sediments older than the Albian (112MA). Furthermore, in areas outside of the Atlantic Ocean, more investigation is needed to reconstruct a more accurate climate (Takashima, 2006).

lat variationsThere is also a huge amount of limestone all over the world dating back to the Cretaceous. This shows that there were universal high sea levels and warmer conditions. But, distinct black, laminated organic-rich layers, black shale, are occasionally intercalated within these sequences. Black shales are often an indication of anoxic conditions, so it has been suggested that this is evidence of a widespread anoxic environment, known as ‘Oceanic Anoxic Events’. Two schools of thought have been proposed to explain the black shale in the ‘Oceanic Anoxic Events’.  The ‘stagnant ocean’ model attributes OAE (Oceanic Anoxic Events) to depletion of bottom water oxygen as a result of dense vertical ocean stratification. The ‘expanded oxygen-minimum layer’ model proposes that increased surface ocean productivity caused expansion of the oxygen-minimum layer in the water column. The diagram below shows these two models. The two models predict different vertical thermal gradient profiles of the water column that can be inferred from the oxygen isotopes of planktic and benthic forams. The OAE in the early Albian is characterised by the drastic increase in surface water temperatures and strengthening of the vertical stratification of the water column, which is similar to the stagnant ocean model.

ocean model

However, the OAE 93.5 MA shows sudden warming of deep water and the collapse of vertical stratification (Huber et al., 1999). This probably induced enhanced upwelling and productivity similar to the expanded oxygen-minimum layer model. Warming of deep water could have contributed to depletion in oxygen solubility in the deep ocean and may have triggered the disassociation of large volumes of methane hydrate buried in sediments of the continental margins.  Oxidation of the released methane could have further consumed dissolved oxygen in the water column, while simultaneously releasing CO2 to the atmosphere (Gale, 2000; Jahren, 2002). As one can imagine, OAE have a significant affect on the diversity and evolution of marine organisms. Numerous records demonstrate a high turnover rate of microfossils at or near OAE intervals (Jarvis et al., 1988; Erbacher et al., 1996; Premoli Silva and Sliter, 1999; Leckie et al.,2002; Erba, 2004). For example, during the Cenomanian-Turonian boundary, OAE expanded below the photic zone, (Damsté and Köster, 1998; Pancost et al., 2004) to greater than 3500m depth in the Atlantic Ocean (Thurow et al., 1992). The result was that about 20% of marine organisms became extinct in less than one million years.

water column strat

It is worth a mention that black shales, especially in OAE 1 and 2, yield no calcareous nanofossils, suggesting that these anoxic conditions had expanded to within the euphotic zone (Hart and Leary, 1991; Coccioni and Luciani, 2005). Anoxic conditions also occasionally occurred in very shallow water during the OAE 2.

Furthermore, these Oceanic Anoxic Events served as a natural thermostat for the Cretaceous Greenhouse Earth; because there was greater organic carbon burial in the OAE pelagic sections, this may have drawn down CO2 from the ocean–atmosphere by burying organic carbon in black shales, thereby causing long-term global warmth (McElwain et al., 2005). Organic-rich sediments are formed under anoxic conditions, and many petroleum source rocks were formed during greenhouse warming peaks between the Middle Jurassic to mid-Cretaceous. Isotopic analyses of wood fragments found throughout the section allow correlation to the standard secular marine δ13C curve because of characteristic peaks at the Aptian-Albian and Cenomanian-Turonian boundaries. Consistency of the north-central Texas δ13C curve with the marine standard facilitates correlation among non-marine and marine environments on a global scale (Jacobs et al., 2005). δ13C records provide an interpretation in terms of global partitioning of carbon between reduced and oxidised reservoirs; this provides a fairly reliable marker, although various things can affect it such as diagenesis and local carbon cycle, tend to obscure such chemostratigraphic signals (Bice et al., 2002). There seems to be an abrupt -3 ‰ excursion in δ 13C that immediately preceded a more gradual 3-4‰ positive that is consistently expressed in multiple sections. Pratt et al. discussed how δ 13C studies of lacustrine organic matter could provide better estimates of pCO2 during times when temporal trends in δ 13C or carbonate and organic matter are de-coupled. Mass balance considerations indicate that biomass burning is an under-explored explanation for pronounced negative excursions in Cretaceous d13C records.

world

Many important factors must be taken into account in order to explain such high sea levels. First of all, there was a change in volume of ocean ridges; this is dependent upon sea-floor spreading rates. There was also a contraction of thermal sea water, depending on sea water temperature and a formation of volcanic plateaus. Finally, there were no ice caps during this period, which changed the temperature drastically. Sea levels peaked in mid- to Late

Cretaceous, approximately 100-75 million years ago, when the total land area flooded was more than 40% greater than today, resulting in the expansion of continental shelf environments (Hays and Pitmann III, 1973) (See figure 5). Through integration of data on occurrences of ice-rafted and/or glacial deposits around polar regions, positive oxygen isotope values of forams, and intervals of rapid sea-level fall, it is quite possible that glaciers waxed and waned during the greenhouse climate of the Mesozoic (Miller et al., 2005a). Uncertainty still exists over ice cap volume and age but, several geologically short-term glacial events during the Cretaceous have been proposed, such as middle Cenomanian, middle Turonian,middle Campanian and earliest and late Maastrichtian (Takashima et al., 2006). In contrast to previously proposed models, these proposals imply that greenhouse periods can exhibit short-term climate variability.

Ocean circulation was also affected during this greenhouse world. In the Cretaceous, the westerly winds developed only seasonally. In the absence of these winds, the subtropical ocean gyres would have weakened leading to an ocean circulation dominated by eddies. Circulation in the coastal ocean differs fundamentally from that of the open ocean in that the large ocean basins are under the influence of trade winds and westerlies, whereas coastal regions are much more influenced by passing weather systems (Csanady, 1982).

arctic ocean

There seems to be an abundance of organic plankton in the Cretaceous, suggesting that shelf-break frontal systems that divide shelf and epicontinental seawaters from the open ocean today did not exist then (Hay, 2008). The breakdown of shelf-break fronts, it is argued, occurred because of the increase water exchange between the ocean and epeiric seas, all of which would have had either a positive or negative fresh-water balance relative to the ocean proper (Hay, 2008). However, in many areas the onset of chalk deposition occurs well after the flooding of the epeiric sea began.

Warm deep water is usually associated with high-latitude deep-water sources. Nevertheless, because the sea water density depends on temperature and salinity, it may be questioned whether the deep-ocean water temperature reflects the warm polar surface-ocean regions (Valdes, 2000). The less dense surface water means that convection shuts and reduces meridional overturning. The reduction of overturning leads to a reduction of poleward heat transfer and vice versa, cooling and even sometimes an increase of salinity. This can lead to a stronger overturning and stronger poleward heat transport (Valdes, 2000). It may be assumed that past ocean circulation was sensitive to high-latitude salinity distribution (Stocker et al., 1992); in some instances, the meridional overturning might have behaved as a bipolar seesaw with a periodicity of hundreds to a thousand years or more (Broecker, 1998). In the Cretaceous, warm, ice-free climates, poleward water vapor transport or river runoff are the causes of low salinity, whereas increased evaporation, which is unlikely in high latitudes, might be a cause of increased high-latitude surface salinity (Pond and Pickard, 1983).

As previously mentioned, there were no polar ice caps during the Cretaceous, or if there were, they were temporary and episodic. It is suggested that this may be due to atmospheric feedbacks, in conjunction with the increased greenhouse gases (Haupt and Seidov, 2001). Because the Earth rotates around the Sun on a tilt, it means that in mid-winter the sun would not appear over the horizon for a month or more and that for much of summer the sun didn’t fully set. Quite a lot of fossil discoveries have confirmed that fact that the Polar Regions were indeed, a lot warmer in the Cretaceous. Recently, fossil remains of turtles and a tropical to sub-tropical champsosaur, have been found on Axel Heiberg Island at 79°N in the Queen Elizabeth Islands of north-eastern Canada (Tarundo, 1998). This crocodile-like reptile is said to have had the same living habits as a modern crocodile- being cold blooded and having to live in relatively warm climates. Furthermore, it cannot migrate or hibernate during winter, as is thought possible for some polar dinosaurs and turtles. Therefore, the champsosaur is considered to be an ideal climatic indicator. Therefore, the climate in the Polar Regions must have been sub-tropical to tropical; more specifically, the warm season temperatures very likely ranged from 25°C to 35°C with the coldest month mean temperature of about 5.5°C (Tarundo et al., 1998). This means that the mean annual temperature would have been 14°C, which is drastically warmer to today’s -20°C (for the present annual mean temperature for the area).

champsosaur

The Cretaceous climate was indeed very different to our own; CO2 concentrations were in excess of 1000ppm; the surface temperature was possibly up to 30°C hotter than the present; there were no polar ice caps and sea circulation did not bring cool water to high latitudes. The ocean thermohaline conveyor, although very different to present day, may have operated similarly to the present-day mode. The only difference was that the amplitude might have been lower than today, due to smaller equator-to-pole density gradients, and the driving deep-water sources may have switched roles. It should be noted that during the Turonian several pronounced, yet short-lived, cooler intervals punctuate the extreme warmth and shows that rapid tropical sea surface temperature changed during the Cretaceous Greenhouse World. This implies that even the mid-Cretaceous ‘super greenhouse’ climate may have been less stable than previously thought (Foster et al., 2009).

 

 

 

 

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