Mengapa dinosaurus menyeberangi khatulistiwa ?--T-REC-komunitas reptil-semarang--KSE-komunitas satwa eksotik

SILAHKAN MENGGUNAKAN " MESIN TRANSLATE "..GOOGLE TRANSLATE
DISAMPING KANAN INI.............

PLEASE USE ........ "TRANSLATE MACHINE" .. GOOGLE TRANSLATE BESIDE RIGHT THIS

.................


T-REC -TUGUMUDA REPTILES COMMUNITY-INDONESIA


More info :
www.trecsemarang2011.blogspot.com
minat gabung : ( menerima keanggotaan seluruh kota dan daerah di Indonesia )
08995557626
..................................
KSE – KOMUNITAS SATWA EKSOTIK – EXOTIC PETS COMMUNITY-- INDONESIA
Visit Our Community and Joint W/ Us....Welcome All Over The World
www.facebook.com/groups/komunitassatwaeksotik/
 KSE = KOMUNITAS SATWA EKSOTIK

MENGATASI KENDALA MINAT DAN JARAK

KAMI ADA DI TIAP KOTA DI INDONESIA
DETAIL TENTANG KSE-----KLIK : www.komunitassatwaeksotik-pendaftaran.blogspot.com

GABUNG......... ( menerima keanggotaan seluruh kota dan daerah di Indonesia )
HUBUNGI   :  089617123865-08995557626

.........................

Mengapa dinosaurus menyeberangi khatulistiwa ?

Perubahan iklim liar - bertahan puluhan juta tahun - terlalu lama  untuk dinosaurus

Date:

June 15, 2015

Source:

University of Utah

Summary:

Sebuah gambaran  yang sangat rinci tentang iklim dan ekologi selama Periode Triassic menjelaskan mengapa dinosaurus gagal membangun dominasi dekat khatulistiwa selama 30 juta tahun ....more

Why did the
dinosaur cross the equator, then not stay there?

Wild climate swings -- persisting tens of millions of years -- were too
much for the dinos

Date:

June 15, 2015

Source:

University of Utah

Summary:

A remarkably detailed picture of the climate and ecology during the
Triassic Period explains why dinosaurs failed to establish dominance near the
equator for 30 million years.

............

For more than 30 million years after dinosaurs first appeared, they
remained inexplicably rare near the equator, where only a few small-bodied
meat-eating dinosaurs eked out a living. The age-long absence of big
plant-eaters at low latitudes is one of the great, unanswered questions about
the rise of the dinosaurs.

And now the mystery has a solution, according to an international team of
scientists who pieced together a remarkably detailed picture of the climate and
ecology more than 200 million years ago at Ghost Ranch in northern New Mexico,
a site rich with fossils from the Late Triassic Period.

The new findings show that the tropical climate swung wildly with extremes
of drought and intense heat. Wildfires swept the landscape during arid regimes
and continually reshaped the vegetation available for plant-eating animals.

"Our data suggest it was not a fun place," says study co-author
Randall Irmis, curator of paleontology at the Natural History Museum of Utah
and assistant professor at the University of Utah. "It was a time of
climate extremes that went back and forth unpredictably and large, warm-blooded
dinosaurian herbivores weren't able to exist nearer to the equator -- there was
not enough dependable plant food."

The study, led by geochemist Jessica Whiteside, lecturer at the University
of Southampton, is the first to provide a detailed look at the climate and ecology
during the emergence of the dinosaurs. The results are important, also, for
understanding human-caused climate change. Atmospheric carbon dioxide levels
during the Late Triassic were four to six times current levels. "If we
continue along our present course, similar conditions in a high-CO2 world may
develop, and suppress low-latitude ecosystems," Irmis says.

The other authors are Sofie Lindström, Ian Glasspool, Morgan Schaller,
Maria Dunlavey, Sterling Nesbitt, Nathan Smith and Alan Turner. They report the
findings today in the Proceedings of the National Academy of Sciences.

Reconstructing the deep past

The earliest known dinosaur fossils, found in Argentina, date from around
230 million years ago. Within 15 million years, multitudes of species with
different diets and body sizes had evolved and were abundant beyond the
tropical latitudes. In the tropics, the only dinosaurs present were small
carnivores. This pattern persisted for 30 million years after the first
dinosaurs appeared.

In the new study, the authors focused on Chinle Formation rocks, which were
deposited by rivers and streams between 205 and 215 million years ago at Ghost
Ranch (better known to many outside of paleontology as the place where artist
Georgia O'Keeffe lived and painted for much of her career). The multi-colored
rocks of the Chinle Formation are a common sight on the Colorado Plateau at
places such as the Painted Desert at Petrified Forest National Park in Arizona.
During the Late Triassic, North America and other land masses of the world were
bound together in the supercontinent Pangea. The Ghost Ranch site stood close
to the equator at roughly the same latitude as present-day southern India.

The researchers reconstructed the deep past by analyzing several kinds of
data: fossils, charcoal left by ancient wildfires, and stable isotopes from
organic matter and carbonate nodules that formed in ancient soils. "Each
dataset complements the others, and they all point towards similar
conditions," Whiteside says. "I think this is one of the major
strengths of our study."

Fossilized bones, pollen grains and fern spores revealed the types of
animals and plants living at different times, marked by layers of sediment.
Dinosaurs remained rare among the fossils, accounting for less than 15 percent
of vertebrate animal remains. They were outnumbered in diversity, abundance and
body size by the reptiles known as Pseudosuchian archosaurs, the lineage that
gave rise to crocodiles and alligators.

The sparse dinosaurs consisted mostly of small, carnivorous theropods. Big,
long-necked dinosaurs, or sauropodomorphs -- already the dominant plant-eaters
at higher latitudes -- did not exist at the study site or any other
low-latitude site in Triassic Pangaea, as far as the fossil record shows.

Abrupt changes in climate left a record in the shifting abundance of
different types of pollen and fern spores between sediment layers. Fossilized
organic matter from decaying plants provided another window on climate shifts.
Changes in the ratio of stable isotopes of carbon in the organic matter
bookmarked times when plant productivity declined during extended droughts.

Drought and fire

Wildfire burn temperatures varied drastically, the researchers found,
consistent with a fluctuating environment in which the amount of combustible
plant matter rose and fell over time. The researchers estimated the intensity
of wildfires using bits of charcoal recovered in the sediment layers. The
amount of light reflected from the fossil charcoal under a light microscope
relates directly to the burn temperature of the wood. The overall picture, the
authors say, is that of a climate punctuated by extreme shifts in precipitation
in which plant die-offs fueled hotter fires, which in turn killed more plants,
damaged soils and increased erosion.

Atmospheric carbon dioxide levels, calculated from stable isotope analyses
of soil carbonate and preserved organic matter, rose from about 1,200 parts per
million at the base of the section, to about 2,400 parts per million near the
top. At these high CO2 concentrations, climate models predict more frequent and
more extreme weather fluctuations consistent with the fossil and charcoal
evidence.

Continuing shifts between extremes of dry and wet likely prevented the
establishment of dinosaur-dominated communities found in the fossil record at
higher-latitudes across South America, Europe and southern Africa, where
aridity and temperatures were less extreme and humidity was consistently
higher. Resource-limited conditions could not support a diverse community of
fast-growing, warm-blooded, large dinosaurs, which require a productive and
stable environment to thrive.

"The conditions would have been something similar to the arid western
United States today, although there would have been trees and smaller plants
near streams and rivers and forests during humid times," says Whiteside.
"The fluctuating and harsh climate with widespread wild fires meant that
only small two-legged carnivorous dinosaurs, such as Coelophysis,
could survive."







Story Source:

The above post is reprinted from materials provided byUniversity
of Utah. Note: Materials may be edited for content and length.







Journal Reference:

1.   
Jessica H. Whiteside, Sofie Lindström, Randall B. Irmis, Ian J. Glasspool,
Morgan F. Schaller, Maria Dunlavey, Sterling J. Nesbitt, Nathan D. Smith, and
Alan H. Turner. Extreme ecosystem instability suppressed tropical
dinosaur dominance for 30 million years. PNAS, 2015 DOI:10.1073/pnas.1505252112

http://www.sciencedaily.com/releases/2015/06/150615152436.htm

Share this: