Continuing with the dinosaur theme, this week an international team of scientists announced that they had uncovered the oldest dinosaur embryos and that they contained organic material. The team, led by University of Toronto Missasauga paleontologist Robert Reisz, included scientists from Canada, Australia, Germany, Taiwan and the People’s Republic of China. The fossil site outside the city of Lufeng, in Yunan, China is about 197 to 190 million years old, or from the early Jurassic period.
Both the age and preservation of the embryos make these fossils remarkable. Most dinosaur embryo fossils are from the Cretaceous, meaning this discovery pushes the date of the oldest well-preserved embryos back by over 100 million years. That means that there is more time between when these newly discovered embryos died and the next oldest embryo than between the extinction of dinosaurs and the modern day!
The team found the remains of about 20 embryos in different developmental stages, including eggshells and more than 200 disarticulated bones, from several nests. This variety allowed the scientists to study the embryonic development of these extinct creatures. The remains are thought to be from the sauropodomorph Lufengosaurus, which was common in the region at that time and as an adult was approximately 8 meters long (26 feet).
The scientists focused on the largest embryonic bone, the femur, in their analysis. They noted that the bones grew very quickly, suggesting a short incubation period. Closer inspection showed that the bones had also been reshaped while in the egg, suggesting the embryos were moving around much like the embryos of modern birds.
Utilizing infrared spectroscopy, the team was able to analyze bone-tissue samples and found evidence of collagen fibers, an essential protein found in connective tissues including bone. This breakthrough is all the more impressive because embryonic bones are porous and fragile, making them more vulnerable to the environmental processes during fossilization. This suggests that perhaps other dinosaur fossils could also have organic material.
The picture above is from a cross-section of a femur used to analyze the collagen fibers. The composition of collagen varies between species, so studying these fibers could help scientists to learn more about these extinct creatures. The characteristics of the collagen as well as the embryonic development could help to explain how sauropodomorphs and their descendants, the sauropods, were able to grow to such extreme size.
To learn more about this discovery and what it means to be a dinosaur, check out my Word Wednesday post and the links below.