Dinosaur Institute Origin of Dinosaurs | Natural History Museum of Los Angeles

Follow us on FacebookFollow us on TwitterFollow us on FlickrFollow us on YouTubeFollow us on PinterestFollow us on Instagram

Current Research

This 99-million-year-old amber piece with bird feathers is part of the NHMLA's growing collection of Cretaceous amber.  Scientists are currently studying the plumage of avian and nonavian dinosaurs to understand the evolution of flight among other characteristics of birds. Specimens like the one shown here give us one more piece of evidence.

Join the NHM Next Campaign

The NHM Next campaign is transforming the Museum into one of the coolest destinations in Southern California. Want to get involved in our final phase?  
Learn More

L.A. Theatre Works and KPCC present "The Lost World"

"The Lost World" broadcast includes a conversation with Leonard Nimoy and a special insider's tour of the Dino Lab at the Natural History Museum of L.A. County.

Listen to the MP3 [11MB] >
(or right-click to download and save)

Visit the L.A. Theatre Works site >


Origin of Dinosaurs

The ancestry of dinosaurs can be traced back some 230 million years ago to the Late Triassic. At this time, all landmasses were united into a gigantic continent called Pangea. The breakup of this enormous landmass together with significant changes in global climate, and the disappearance of primitive lineages of archosaurs provided impetus for the divergence of dinosaurs. Afterwards, the rapid evolution of critical physical innovations equipped these animals with the specializations required to rule over all Mesozoic terrestrial ecosystems.

All dinosaurs belong to a group of reptiles called archosaurs-a group that also includes crocodiles and a variety of Mesozoic reptiles (pterodactyls and others) that are often misinterpreted as dinosaurs. The anatomical characteristics of both the earliest known dinosaurs and their archosaurian relatives suggest that the common ancestor of all dinosaurs was a small bipedal predator, which had forelimbs shorter than hind limbs. This ancestor was probably similar to the 235-million-year-old Lagosuchus from Argentina, pictured below.

From the most primitive Triassic forms to the most advanced ones of the latest Cretaceous, all dinosaurs share defining traits that distinguish them from their closest archosaurian relatives. Among these innovations, the femur (or upper leg bone) developed a distinct head for a tied attachment into a hollow hip socket. These and other changes resulted in a hind limb that was tucked directly underneath the body, providing upright, pillar-like support of the body and also enhancing locomotive abilities. The changes that led to the erect posture of dinosaurs from the sprawling posture of their reptilian predecessors had a profound effect on the evolutionary success of these animals. These transformations may have also been coupled with the evolution of a higher metabolism (a step towards warm bloodedness) that endowed them with a greater capacity for sustained activities such as running.