Who was boss before the dinosaurs? Large hippo-like mammal forerunner ("Placerias") that lived, and died off, during the Triassic. (National Park Service Image)
Who was boss before the dinosaurs?
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The Jurassic witnessed a world populated by dinosaurs -- giant plant-eaters munching their way through ferns and conifer forests, while large carnivores chased them down for lunch.
 
At the height of the Age of Dinosaurs, they were found on every continent, flourishing in the warm environments of the time.
 
But, dinosaurs were not always so prominent. Fossil evidence shows that they arose about 230 million years ago during the Triassic period, but remained scarce as other reptiles took center stage. Many mammal forerunners, such as the large plant-eater Placerias, prospered. Huge crocodile-like animals like Smilosuchus were the top predators of the Triassic.
 
Paleontologists who study the fossil record have discovered that something big happened 200 million years ago that radically changed life on land and in the sea, paving the way for dinosaur diversification and prominence.
 
What happened was so momentous that it caused more than half of all life on Earth to go extinct. The large crocodile-like reptiles that had dominated the landscape were eradicated, as were many of the mammal forerunners.
 
Find out more about the events that opened the door for the Age of Dinosaurs. Join us on Thursday, October 8, 2015, for a "Smithsonian Science How" live webcast on How Fossils Explain the Rise of Dinosaurs, airing at 11 a.m. and 2 p.m. EDT on the Q?rius website. Paleontologist Dr. Hans Sues from the National Museum of Natural History will appear live to discuss and answer questions. Get teaching resources to support your webcast experience.

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CRITICAL THINKING QUESTION
To study dinosaurs, why do scientists rely on fossils instead of photographs?
Write your answers in the comments section below


COMMENTS (25)
  • jaredp-lam
    9/23/2015 - 09:45 a.m.

    Very interesting that the large crocodile-like creatures who ruled before dinosaurs were so quickly killed. I wonder if humans could go extinct that fast...

    • logang-1-war
      9/24/2015 - 12:58 p.m.

      nope

  • garrettm1-lam
    9/23/2015 - 10:43 a.m.

    This article is very good at catching your eye and wanting you to read more. If I could, I would try to watch the webcast and learn more about this topic. Although I do wish that the article gave more information rather than just being a short explanation. Altogether, this article is very good at getting you attached to the subject.

  • marekb-lam
    9/23/2015 - 10:48 a.m.

    Dinosaurs weren't always the bosses? Wow! I've never even hear of this "Placerias" that was mentioned as one of the reptiles that were prospering.

  • jacobt-lam
    9/23/2015 - 11:55 a.m.

    We all knew about the nice old dinosaurs but before that, what was there? There was older creatures roaming our Earth with multiple samples from these different creatures. Earlier then dinosaurs there were animal conquerors.

  • briannec-ste
    9/23/2015 - 01:23 p.m.

    Of course, Crocodiles are the one animal that that are related to dinosaurs.

  • sophiew-pla
    9/23/2015 - 09:37 p.m.

    Most people think dinosaurs were the first to roam this planet. However, this article makes it clear that there were other animals before them who dominated the earth. This is can be shown by the research done by the paleontologists. I found this article to be interesting because I also was one who thought the dinosaurs were the first to roam earth. This article shows us the that there were many other species of life not only before us humans, but before the dinosaurs as well.

  • catullo,johnny-cas
    9/24/2015 - 07:26 a.m.

    1) In the Triassic period, there was no technology advanced enough to take a picture. Fossils are the closet thing scientists could get to dinosaur anatomy. The pictures were based and structured upon the dinosaur bones.


    2) I found this article interesting because I did not know how large reptiles ruled over dinosaurs before. One complaint I have for this article is that it is not long enough. I would love to read more.

  • cadet,raphaella-cas
    9/24/2015 - 09:28 a.m.

    1.Scientists rely on fossils instead of photographs because it gives them a clear background of dinosaurs. Scientists use fossils for more detailed findings.

    2.I think this article is very interesting and i would like to know more about what dinosaurs have been through during the decades of time,this articles only gives a brief explanation.

  • ianc-day
    9/24/2015 - 10:49 a.m.

    This is interesting because we've learned that dinosaurs were the biggest population, but this article says this is wrong. Dinosaurs came later than mammals and things like crocodiles. How have they changed over the years? People should watch that show to find out what happened.

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