The world’s oldest bird eggshells have been verified by Yoichi Azuma, professor of paleontology at Fukui Prefectural University’s Dinosaur Research Institute, and colleagues according to a March 18, 2014, article at the Asahi Shimbum website.
The three shells were originally found in 1990 in Katsuyama in Fukui Prefecture, Japan.
The eggs range in size from two millimeters in circumference to six millimeters in circumference and date to the Cretaceous Period about 120 million yeasr ago.
The eggshells are 0.4 millimeters thick and have three distinct layers.
The conclusion that the fossils are bird eggs is based on the size and shape of the eggs, the thickness of the shell, the material that makes up the shells, and the fact that over 30 fossilized bird foot prints have been found in the same area.
The scientists cannot identify the species of bird that laid the eggs because there is no fossilized organic matter accompanying the shells and the sizes of the shells indicate that no bones had developed in the bird embryo at the time the eggs were broken.
This is the first hard evidence that true birds existed as far back as 120 million years ago and is expected to provide new insights into how birds lived, ate, bred, and nested in the Cretaceous Period.
The fossils were not recognized as bird eggs when they were first discovered.