Scientists have discovered that what we know about dinosaur origins and phylogeny may have been wrong.
For over 100 years, scientists thought that dinosaurs first evolved 230 million years ago on the ancient continent of Gondwana. A new discovery points to a completely different time and location of origin.
Gondwana was the supercontinent that formed the southern part of Pangaea. Over the Mesozoic and Cenozoic, Gondwana broke up into smaller portions of land, which eventually became some of the continents and countries we know today. Africa, North and South America, Australia, Antarctica, India, and the Balkans were all part of Gondwana.
Scientists found what were the oldest known dinosaur fossils in South America. Because of this discovery, scientists surmised that dinosaurs probably originated in Gondwana. A new study, however, reveals that dinosaurs may have come from Laurasia, the northern supercontinent in Pangaea, instead. Most of Europe and Asia, including China and Siberia, were once parts of Laurasia.
The researchers actually stumbled upon this discovery as they were looking through the phylogeny—or “family tree”, if you will—of dinosaurs. For the past 130 years, paleontologists have thought that they can classify dinosaurs as “bird-hipped” or “lizard-hipped”. One category of dinosaurs have hipbones similar to those of birds, while dinosaurs in the other category have hipbones similar to those of lizards.
The “bird-hipped” dinosaurs were all herbivorous. Meanwhile, the “lizard-hipped” dinosaurs had both herbivores and carnivores. The recent discovery challenges these categorizations.
Of course, more dinosaur bones and species have been discovered in the past 130 years. The researchers for this new study analyzed more dinosaur fossils and bones, as well more recently-discovered species. The researchers argue that the lizard-hipped carnivores should be in the same category as the bird-hipped herbivores. These two groups have 21 anatomical similarities, and the researchers propose the creation of a new group that includes these two.
The researchers also claim that dinosaurs have been around a little earlier than scientists previously thought. They think that they can trace dinosaur origins back to about 245 to 247 million years ago instead of 230 million years. The first dinosaurs may also have been omnivores, and carnivores evolved later on.
"Now we have our evolutionary tree, we can use it as a foundation to understand how dinosaur features evolved over time, and it is already beginning to help us explain some questions that have puzzled us,” says Prof. Paul Barrett, a contributor to the study.
The new information may address inconsistencies in prior knowledge and fill in some missing pieces. Of course, it can also raise new questions, the answers to which will contribute to the existing body of knowledge on dinosaur origins.
These findings are a prime example of science at work. It's always good to challenge older ideas and see if they can withstand the test of time and newer evidence. Studies on dinosaur origins are an ongoing body of work, and there will periodically be new discoveries, theories, and conclusions.
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