Palaeontologists have recently researched and found a new type of iguanadontid dinosaur, after conducting further research on a breastbone that was discovered in 1999, according to the Times of India.
The bone was found over 20 years ago in the Iwaki City Ammonite Center in Fukushima prefecture, where the building is located within the Ashizawa mountain formation. During the Cretaceous period, this area was a shallow marine environment, in an area called the Upper Cretaceous Futaba Group, which was formed about 90-88 million years ago, Phys.org reports. The sternal bone was initially thought to have been part of a hadrosaur, before it was shelved for later study. Many iguanadont fossils usually recovered from Japan are fragments, so their ecology has always been lacking more details.
Why was there a delay?
Museums and other centres for fossil research hold thousands of specimens, many of which were gathered before scientific analysis became updated with new tools and methods to study them. Researchers that have new inquiries then return back to some of these bones and conduct more studies.
The study of this dinosaur, published in Paleontological Research, revealed that the right breastbone of the dinosaur fits more of a unknown variant of a iguanadont called a styracosternan, which is a type of ornithopod known for having fused, hooked thumbs. Species include dinosaurs such as Edmontosaurus and Iguanadon. Compared to previous members of this species found in the Ashizawa formation, this specimen is estimated to have a length of about three metres, or about 9-10 feet. This shows that throughout East Asia, iguanadonts of various sizes lived throughout the region's coastal, shallow environments in the Late Cretaceous area.
What are the Iguandontids?
Iguanadontids, various forms of the dinosaur Iguanadon, were herbivores that roamed the world from the Late Jurassic through the Late Cretaceous period. Their sizes and shapes varied, and included hadrosaurs as well. They migrated across Asia, Europe, and North America back when the continents were part of a larger supercontinent called Laurasia. With the changes in ecosystems, many iguandontids diversified to adapt. While the bone does not show all the details about the dinosaur's life, such as if it was an adult or a juvenile, the study suggests it is a smaller, different animal compared to the other fossils discovered.
The Fukushima region of Japan during this time was a very shallow marine area, a "mixture of plains, wetlands, vegetation-rich shorelines and islands." The larger the herbivore, the further they could travel, and the taller the vegetation they could consume. Smaller ones could access dense areas that would be normally out of reach.
In recent years, Japan has had more significant fossil discoveries, but while they are still not complete, each clue fills gaps in the country, and more specifically the region's fossil record.
For More Information:
The study, "An iguanodontid sternal plate from the Upper Cretaceous Ashizawa Formation (Futaba Group) of Fukushima Prefecture, Japan" can be read here: