The DINO Times

The

DINO

December 2014 #1

Times

t ! s 1ssue i

What are dinosaurs? pg.3

Why even the vegetarian dinosaurs were gigantic? pg.7

Huge Asteroid Is Still the Central Villain in Dinosaurs’ Extinction pg.11

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http://dreamatico.com/dinosaurs/2/

What are dinosaurs?

D

inosaurs are a group of reptiles that dominated the land for over 160 million years. They evolved diverse shapes and sizes, from the fearsome giant Spinosaurus to the turkey-sized Microraptor, able to survive in a variety of ecosystems.

One of the reasons for the dinosaurs’ success is that they had straight legs, perpendicular to their bodies. This allowed them to move faster than other reptiles that had a sprawling stance like today’s lizards and crocodiles. Most dinosaur species became extinct around 65 million years ago, but the descendents of one dinosaur group, birds, are still with us today.

Other prehistoric reptiles Dinosaurs are descended from archosaurs, a large group of reptiles that appeared about 250 million years ago. Archosaurs also gave rise to non-dinosaur reptiles such as the pterosaurs (flying reptiles), now extinct, and the ancestors of modern crocodiles. These and many other types of ancient reptiles are often wrongly called dinosaurs. source:http://internt.nhm.ac.uk/

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When did dinosaurs live?

D

inosaurs lived between 230 and 65 million years ago, in a time known as the Mesozoic Era. This was many millions of years before the first modern humans, Homo sapiens, appeared. Scientists divide the Mesozoic Era into 3 periods: the Triassic, Jurassic and Cretaceous. During this time, the land gradually split up from one huge continent into smaller ones.

The associated changes in the climate and vegetation affected how dinosaurs evolved. Triassic Period (250 – 200 million years ago) All

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continents were part of a single landmass called Pangaea during the Triassic Period.

This meant that there weren’t many differences between the animals or plants found in different areas. The climate was relatively hot and dry, and much of the land was covered with large deserts.

Unlike today, there were no polar ice caps. It was in this environment that the reptiles known as dinosaurs first evolved. Reptiles tend to flourish in hot climates because their skin is less porous than mammal skin, for example, so it loses less water in the heat. Reptile kidneys are also

better at conserving water. Towards the end of the Triassic, a series of earthquakes and volcanic eruptions caused Pangaea to slowly begin to break into two.

This was thebirth of the Atlantic Ocean. Coelophysis, a Triassic dinosaur Jurassic Period (200 – 145 million years ago) At the end of the Triassic Period there was a mass extinction, the causes of which are still hotly debated.

Many large land animals were wiped out but thedinosaurs survived, giving them the opportunity to evolve into a wide variety of forms and increase in number. The single land mass, Pangaea, split into two, creating Laurasia in the north and Gondwana in the south.

Despite this separation, similarities in the fossil records show that there were land bridges between the two continents.

Temperatures fell slightly, although it was still warmer than today due to higher amounts of carbon dioxide in the atmosphere. Rainfall increased as a result of the large seas appearing between the land masses.

These changes allowed plants such as ferns and horsetails to grow over huge areas. Some of this vegetation became the fossil fuels that we

mine today. Elsewhere there were forests of tall conifer trees such as sequoias and monkey puzzles.

The plentiful plant supply allowed the huge plant-eating sauropods – such as Apatosaurus, Diplodocus and Brachiosaurus – to evolve.

These are thelargest animals to have ever walked the Earth. By the end of the Jurassic their herds dominated the landscape.

Diplodocus, a Jurassic dinosaur Cretaceous Period (145 – 65 million years ago) During the Cretaceous the land separated further into some of the continents we know today, although in different positions.

This meant that dinosaurs evolved independently in different parts of the world, becomingmore diverse. Other groups of organisms also diversified. The first snakes evolved during this time, as well as the first flowering plants.

Various insect groups appeared, including bees, which helped increase the spread of flowering plants. And the mammal group now included tree climbers, ground dwellers and even predators of small dinosaurs. source: http://internt.nhm.ac.uk/nature-online/life/dinosaurs-other-extinct-creatures/dino-directory/about-dinosaurs/ when-did-dinosaurs-live.html

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Mark Englert. ‘Its a Dinosaur’

Why even the vegetarian dinosaurs were gigantic?

D

avid Attenborough looks at the skeleton of a brontosaurus, one of the biggest dinosaurs ever. It was over 60 feet long and weighed around 30 tons. But why did these vegetarian dinosaurs grow so big?

There are at least two possible answers. The plants they ate - cycads and ferns - would have been tough, fibrous and difficult to digest. And since the brontosaurus had relatively feeble teeth, it would have needed a huge stomach in which the food could have fermented for very long periods of time. But a huge stomach requires a huge body to carry it.

Another reason why they grew so large may have been to do with the recurring problem for all reptiles: temperature control. The bigger the body, the less susceptible it is to variations in temperature because a big body retains its heat for longer.

Temperature control may have also been the reason for the bizarre body shape of another type of dinosaur - the stegosaurus. The stegosaurus had plates on its back that people used to think were a kind of armour. But scientists have now discovered that the plates would have been covered by skin that was thick with blood.

The plates therefore acted as solar panels to heat the animal’s blood.

If the animal overheated then all it needed to do was turn away from the sun for them to act as very efficient cooling radiators.

This ability to influence temperature would have been invaluable. In Texas, the muds of an ancient estuary have now turned to rock and preserve the yard-wide footprints of a giant herbivorous dinosaur - a vivid record of these creatures. Also visible are the footprints of a flesh-eating dinosaur that was 10 to 12 feet tall. source: http://www.bbc.co.uk/programmes/

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Huuge Asteroid Is Still the Ceentral Villain in Dinosaurs’ Exxtinction

F

or some

30

years , scientists have

debated what sealed the fate of the dinosaurs .

Was

an asteroid impact

more or less solely responsible for

the catastrophic mass extinction at the end

Cretaceous geological period, 65 million years ago ? O r were the dinosaurs already undergoing a long - term decline , of the

and the asteroid was merely the coup de grâce ?

S o three young researchers , led by S tephen L. Brusatte , a graduate student at C oluцмmbia U niversity who is affiliated with the A merican M useum of N atural History , decided to test this hypothesis with

a

close

examination

of

the

fossil

12 million years leading up to the mass extinction .

F or the study , the researchers departed record over the

from

the

practice

of

focusing

almost

exclusively on raw counts of the number of species over time .

Instead ,

they analyzed

changes in the anatomies and body plans of seven large groups of late dinosaurs

for

insights

evolutionary trajectory .

C retaceous

into

their

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G roups that show an increase in variability , for example , might have been evolving into more species , giving them an ecological edge . B ut decreasing variability might be a warning sign of approaching doom .

In science , alas, not all projects fulfill researchers ’ ambitions .

The findings of

this

one

inconclusive ,

were

mixed

and

generally

Mr. Brusatte ’s team reported in an article published online last week by the journal N ature C ommunications . A t best , striking a positive note , the team wrote that the “ calculations paint a more

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nuanced picture of the last of dinosaur history .”

12 million years

As M r. Brusatte explained, the late C retaceous “ wasn ’t a static ‘lost world’ that

was

violently

“ were

undergoing dramatic changes during

asteroid impact .”

interrupted

by

an

Some dinosaurs , he noted ,

this time , and large herbivores seem to have

been mired in a long - term decline , at least in

N orth A merica.”

The findings showed

that duck - billed

hadrosaurs and horned ceratopsids , two

groups of large - bodied , bulk - feeding plant

eaters ( meaning they ate just about anything

Asia. The

diversity at this time .

that the extinction debate will continue .

and everything ) might have declined in

In

contrast , small

fossil record in many regions was

insufficient for reliable analysis , meaning

While hadrosaurs A merica, their diversity

M r. Brusatte , the other Richard J. Butler of the U niversity of Munich, Albert Prieto M árquez of the Bavarian State C ollection for P aleontology and G eology in M unich , and M ark A. N orell , an A merican M useum paleontologist who is M r . B rusatte ’ s doctoral adviser .

D r. N orell said the study of skeletal

seemed to have been increasing in parts of

changes in groups of species over time was

herbivores

like

pachycephalosaurs ,

the and

ankylosaurs the

and

meat - eating

tyrannosaurs and coelurosaurs , appeared to be holding steady or perhaps increasing in diversity .

So,

too , were the enormous

herbivorous sauropods like apatosaurs .

The

results

different

were

continents .

declined in

N orth

not

uniform

on

Besides

authors were

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“a

novel way ” to assess their prospects for

survival over the long haul .

“It

would be

nice to have more fossils to see how much these results are real ,” he said .

Paul C. S ereno , a paleontologist at the U niversity of C hicago who had no part in the study , agreed that such investigations of life at the end of the C retaceous had been “ limited by the coarseness of the data where you really need it .” H e questioned whether the research technique , though

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useful in studying simpler invertebrates , could be applied successfully to dinosaurs .

“It’s

an interesting study , and they are

quality researchers ,”

I

D r. S ereno

said ,

“ but

don ’ t think it changes the picture over

all :

E xtinctions

aren ’ t a simple process ,

but ultimately the asteroid was the major factor at the end of the

C retaceous.”

source: http://www.nytimes.com/2012/05/08/science/asteroids-impact-still-central-to-dinosaurs-extinctionhtml?_r=0