Why did some dinosaurs grow so big?

Paleontologists don't know for certain, but perhaps a large body size protected them from most predators, helped to regulate internal body temperature, or let them reach new sources of food (some probably browsed treetops, as giraffes do today). No modern animals except whales are even close in size to the largest dinosaurs; therefore, paleontologists think that the dinosaurs' world was much different from the world today and that climate and food supplies must have been favorable for reaching great size.

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Where did dinosaurs live?

Dinosaurs lived on all of the continents. At the beginning of the age of dinosaurs (during the Triassic Period, about 230 million years ago), the continents were arranged together as a single supercontinent called Pangea. During the 165 million years of dinosaur existence this supercontinent slowly broke apart. Its pieces then spread across the...

When did dinosaurs become extinct?

Dinosaurs went extinct about 65 million years ago (at the end of the Cretaceous Period), after living on Earth for about 165 million years. If all of Earth time from the very beginning of the dinosaurs to today were compressed into 365 days (one calendar year), the dinosaurs appeared January 1 and became extinct the third week of September. (Using...

What was Pangea?

From about 280-230 million years ago (Late Paleozoic Era until the Late Triassic), the continent we now know as North America was continuous with Africa, South America, and Europe. They all existed as a single continent called Pangea. Pangea first began to be torn apart when a three-pronged fissure grew between Africa, South America, and North...

Were dinosaurs warm-blooded or cold-blooded?

Scientists have conflicting opinions on this subject. Some paleontologists think that all dinosaurs were 'warm-blooded' in the same sense that modern birds and mammals are: that is, they had rapid metabolic rates. Other scientists think it unlikely that any dinosaur could have had a rapid metabolic rate. Some scientists think that very big...

Did people and dinosaurs live at the same time?

No! After the dinosaurs died out, nearly 65 million years passed before people appeared on Earth. However, small mammals (including shrew-sized primates) were alive at the time of the dinosaurs. Many scientists who study dinosaurs (vertebrate paleontologists) now think that birds are direct descendants of one line of carnivorous dinosaurs, and...

Did all the dinosaurs live together, and at the same time?

Dinosaur communities were separated by both time and geography. The 'Age of Dinosaurs' (the Mesozoic Era ) included three consecutive geologic time periods (the Triassic, Jurassic, and Cretaceous Periods). Different dinosaur species lived during each of these three periods. For example, the Jurassic dinosaur Stegosaurus had already been extinct...

Do any mass extinctions correlate with magnetic reversals?

No. There is no evidence of a correlation between mass extinctions and magnetic pole reversals. Earth’s magnetic field and its atmosphere protect us from solar radiation. It’s not clear whether a weak magnetic field during a polarity transition would allow enough solar radiation to reach the Earth's surface that it would cause extinctions. But...

Can USGS photos of fossils be downloaded or viewed online?

Some fossil photos can be viewed and downloaded from the USGS Photographic Library and our Multimedia Gallery . Fossil photos can also be viewed as published plates within many online USGS publications. Visit the USGS Publications Warehouse to search for publications. The best keywords for searches are author names, such as William Cobban, Norm...
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Image: Juvenile Mammoth Bones in Tule Springs Fossil Beds National Monument (TUSK)
March 15, 2016

Juvenile Mammoth Bones in Tule Springs Fossil Beds National Monument (TUSK)

Bones of a juvenile mammoth spilling out of the ground in Tule Springs Fossil Beds National Monument (TUSK). USGS scientists are currently investigating geologic deposits exposed throughout TUSK to determine how the springs and marshes that attracted the animals responded to climate change in the past.

Attribution: Land Resources
USGS
July 5, 2011

Earth History of the National Capital Region – Volcanoes, Earthquakes & Dinosaurs… Oh My!

Reston, Virginia, was founded 47 years ago & Europeans first settled in the National Capital region 403 years ago. This human footprint can't compare to the dynamic Earth history of this region, extending back as early as 1,180 million years ago and continuing today. For over 120 years, USGS has studied and mapped the region revealing a rich and diverse geologic past.

USGS CoreCast
December 7, 2010

Fossil Discovery Makes History: Studying a Prehistoric Climate and Ecosystem in Colorado

A trio of USGS scientists has been involved in the excavation and study of a major animal and plant fossil discovery in Snowmass Village, Colo., which provides more than 100,000 years of vegetation and climate records for the area. This recent find includes Columbian mammoths, mastodons, extinct bison, Ice Age deer, and a 9-foot ground sloth, and the USGS team is studying

USGS
July 10, 2008

How are dinosaurs named?

Listen to hear the answer.

USGS
February 27, 2008

Which was the smartest dinosaur?

Listen to hear the answer.

Image: Fossil Fish (Jiang Hanichthys)
February 20, 2008

Fossil Fish (Jiang Hanichthys)

Fossilized Jiang Hanichthys, an extinct fish that lived fromthe Cretaceaous to 100 million years ago. Item originally from Hubai Province, China.

Attribution: Ecosystems
Image: Fossil Fish (Jiang Hanichthys)
February 20, 2008

Fossil Fish (Jiang Hanichthys)

Fossilized Jiang Hanichthys, an extinct fish that lived from the Cretaceaous to 100 million years ago. Item originally from Hubai Province, China.

Attribution: Ecosystems
Image: Trilobite Fossil (Phacops rana africana)
February 20, 2008

Trilobite Fossil (Phacops rana africana)

A fossilized Trilobite, Phacops rana africana, an extinct marine invertebrate. Item originally from Alnif, Morocco.

Attribution: Ecosystems
Image: Trilobite Fossil
February 20, 2008

Trilobite Fossil

Trilobite fossil, an extinct marine invertebrate. Item originally from Alnif, Morocco.

Attribution: Ecosystems
Image: Dinosaur Tracks
July 27, 2006

Dinosaur Tracks

Dinosaur tracks in the Jurassic Moenave Formation. It is a popular site for tourists to stop and meet local Navajo and Moenkopi Hopi guides who lead short tours through the tracks area.

Attribution: Ecosystems
Image: Fossilized Tree Trunk
August 1, 2004

Fossilized Tree Trunk

Fossilized tree trunk on a a ridge along the Missouri River, near Fort Kipp, MT.

Image: USGS Snowmastodon Research

USGS Snowmastodon Research

USGS scientists working at Ziegler Reservoir near Snowmass Village, Colorado. 

Attribution: Land Resources