Tag: Dinosaur History

When Did the Dinosaurs Live?

This blog is the first in a series that will explore the timeline of Earth’s history, from the formation of the planet to the dominance and eventual extinction of dinosaurs.

           This blog is about dinosaurs in time; that is, dinosaurs in the timeline of Earth’s history. Not dinosaurs on time, because dinosaurs were hardly ever on time seeing they didn’t have clocks.

           Scientists say the Earth was formed 4.6 billion years ago. At first it was just molten lava, hundreds of miles deep. Over millions of years the Earth cooled and a crust appeared.

Artist’s impression of the Hadean Eon.
Tim Bertelink, CC BY-SA 4.0, via Wikimedia Commons

            The first lifeform that existed was a sort of blue-green algae. Then other lifeforms appeared, including shellfish. That whole time period of more than four billion years is called the Precambrian Eon. From 542 million years ago to the present age is the Phanerozoic Eon. It’s divided into three eras, the Paleozoic, the Mesozoic, and the Cenozoic. During the Paleozoic (from 541 to 252 million years ago) life began to bloom. The first fish, first amphibians, and the first reptiles appeared. The first plants also began to grow. But then a massive extinction wiped out 90% of life on Earth. Its cause is not known, but it ended the Paleozoic Era making way for the Mesozoic Era (from 252 to 66 million years ago).

           That’s when we get to the good stuff: Dinosaurs! The Mesozoic is divided into three time periods: the Triassic, the Jurassic, and the Cretaceous. And about halfway through the Triassic Period a new kind of animal evolved: a dinosaur.

Timeline of Earth (MYA means millions years ago))
Thanaben, CC BY-SA 3.0, via Wikimedia Commons

           During the Triassic the Earth was warm and fairly dry, with ice at the north and south poles. (Although Santa Claus hadn’t moved in yet.) Most of the large island masses gathered together in a supercontinent called Pangaea. Conifers, cycads (which looked like mutant pineapples), and ferns were the most common plants, and reptiles ruled the planet. It was about 240 million years ago that the first dinosaurs appeared. They were small and walked on two legs. Over millions of years, they began to change, and many varieties of dinosaurs appeared. Some were meat eaters; others, plant eaters. Some grew to large sizes. These included Riojasaurus and Lessemsaurus. But then 201 million years ago, another mass extinction took place, probably caused by volcanic action in the Atlantic Ocean, rising sea levels, and climate change.

Pangaea breaking up
Public Domain U.S. Dept. of the Interior

           Some dinosaurs survived and moved into the Jurassic Period. Pangaea broke apart and, over millions of years, formed the continents we know today. Their environment ranged from arid deserts to lush tropical forests. Conifers and ferns were the main plants. Most importantly, dinosaurs dominated each new continent. Some of the largest of all dinosaurs evolved during this time, including Alamosaurus, Argentinosaurus, and Dreadnaughtus. The fierce predator Allosaurus also lived in this time period. And the earliest known bird, Archaeopteryx, emerged in the late Jurassic.

USGS; Diarama by Masato Hattori. Map courtesy of Colorado Plateau Geosystems Inc., Public domain, via Wikimedia Commons

           About 140 million years ago, life on Earth began to change dramatically. Many new life forms emerged while others went extinct. There doesn’t seem to have been any big extinction event, but scientists date this as the beginning of the Cretaceous Period (my favorite time period!). Flowering plants appeared, but there were still a lot of the familiar conifers and ferns. Many new, strange-looking dinosaurs dominated the environment. Tyrannosaurus became an apex predator and weird dinosaurs, such as Parasaurolophus, Ankylosaurus, Triceratops and Pachycephalosaurus roamed around.

           Dinosaurs were so abundant it seemed they would rule Earth forever – but an asteroid colliding with Earth 66 million years ago brought their world to an end. The Cenozoic Era began, with an opening for mammals to dominate the world. The asteroid collision will be the subject of my next blog.

Sources (Click Me!)

Davis, Josh. “The Triassic Period: The Rise of the Dinosaurs.” London Natural History Museum, n.d., https://www.nhm.ac.uk/discover/the-triassic-period-the-rise-of-the-dinosaurs.html

“Hadean Eon: The Formation of Earth (4.6 to 4.0 billion years ago).” EarthHow, 2024. https://earthhow.com/hadean-eon/

“Mesozoic.” U.S. Dept. of the Interior. https://www.usgs.gov/youth-and-education-in-science/mesozoic

Title Image of Triceratops facing Tyrannosaurus
Marcin Chady, CC BY 2.0, via Wikimedia Commons

How the Brontosaurus Lost its Name

Ever wonder how the Brontosaurus lost its name? Commonly known as the icon of Sinclair Oil, this sauropod’s history is complex and newsworthy.

           The Brontosaurus is one of the most famous dinosaurs in the world. Millions of people know its name. Most can recognize its huge shape. It’s been on lunch boxes, made into countless toys, and was featured on a U.S. postage stamp. It even served as the official icon of Sinclair Oil company. However, there is one problem: there is no dinosaur named Brontosaurus.

           How did this happen? When dinosaurs were first discovered in the 1820s, the idea of those huge reptiles stalking the earth caught people’s imagination. Every museum in the world wanted to display a huge skeleton of a dinosaur. But it takes many years to find dinosaur bones, dig them up and put together a dinosaur skeleton. Over the next sixty years the competition to discover dinosaur bones grew, and then it became especially fierce during the 1880s. In fact, that time is now known as the “Bone War.”

           From 1877 to 1892, two paleontologists in particular, Edward Cope of the Academy of Natural Sciences in Philadelphia and Othniel C. Marsh of the Peabody Museum in Connecticut, were the fiercest competitors. They used their own money to finance expeditions and to buy dinosaur bones from other fossil hunters.

           In the beginning Cope and Marsh just paid collectors to send them fossils. But this was only the start. As the rivalry intensified, each side spied on the other, stole bones when they could, bribed workers, and even blew up fossils with dynamite so that the other side couldn’t get them. As soon as either dinosaur hunter got new bones, he rushed to get a description into print. Whoever publishes a description of a new dinosaur first gets to name it, and each man wanted to be the one to name the most. In the end Cope lost. He named 56 new dinosaur species, while Marsh named 80. And by the end of the Bone Wars in 1892, both men had gone nearly bankrupt trying to be the best (or most famous) paleontologist. And the hurry of both men led to mistakes.

Tadek Kurpaski from London, Poland, CC BY 2.0, via Wikimedia Commons

           In 1877 Marsh published a papernaming a new dinosaur, Apatosaurus ajax. Its name means “deceptive lizard,” which turned out to be the truth. The description was based on only a few bones. Two years later Marsh published another article describing what he thought was a different dinosaur, Brontosaurus excelsius.  This description was based on one of the most complete skeletons of a long-necked dinosaur ever found. Brontosaurus means “thunder lizard,” and the catchy name became popular. The mount of that Brontosaurus skeleton in the Yale Peabody Museum of Natural History increased its popularity. Unfortunately, one of the missing pieces of the skeleton was its skull. Not to worry. Marsh just put a Camarasaurus skull on it.

           But, in 1903, Chicago paleontologist Elmer Riggs took a look at both dinosaurs. He determined that the two dinosaurs were actually the same dinosaur. It was given the name Apatosaurus first, and the International Code of Zoological Nomenclature states that the oldest name has priority, so that is the name used by scientists. Brontosaurus became Apatosaurus. And in 1979 scientists finally put the right skull on the skeleton. Still, the general public didn’t let go of the name Brontosaurus until about the 1990s. It was just too cool a name to let go.

           However, all is not lost. There is a movement to resurrect the name Brontosaurus. In 2015 paleontologists studied hundreds of bones from Apatosaurus and the dinosaur called Brontosaurus and found differences in the neck, back, and shoulder bones. Originally scientists thought those difference were because one of the dinosaurs was a juvenile. Now some feel these differences are enough to say Brontosaurus and Apatosaurus are different dinosaurs. But this has not gained wide acceptance. More research may resolve the problem. But a lot of people who are just dinosaur lovers would welcome the return of the “thunder lizard.”

Cover Image Source: An Errant Knight, CC BY-SA 4.0, via Wikimedia Commons