Fossil shape
The reporter learned from the Zhejiang Museum of Natural History on the 15th that Dr. Jin Xingsheng, a researcher at the museum, and researchers at Montana State University in the United States found a fossil specimen of an early Cretaceous bird egg in a joint field survey in Jinyun, Zhejiang: Jinyun thick helmet egg.
This Jinyun thick helmet egg is long, about 5 cm long, 3.2 cm wide, and the thickness of the eggshell is only 0.17 mm, which is the earliest bird egg fossil found in China, and the first bird egg fossil in Zhejiang Province, because of its unique microscopic characteristics of the eggshell, it also represents a new egg fossil family - the thick helmet egg family. But the jury is still out on which bird the egg belongs. The collaborative research was published in the electronic edition of the latest issue of the American Journal of Vertebrate Paleontology.
Photomicroscopic photo of the longitudinal section of the eggshell
ML is the mastoid layer, CL is the continuous layer, and EL is the outer layer
The reporter later received confirmation from Dr. Kim Seung-sang. Dr. Jin Has been studying fossilized egg of the Hinata for several years, and he recalls that the bird egg fossil was discovered in a quarry in Jinyun a few years ago, when he was working on a field survey project with researchers at Montana State University and researchers at Jinyun Museum.
Where is its particularity? Dr. Jin Xingsheng said that bird egg shells generally have three layers of structure on the radial cut surface, namely the papillary layer, the continuous layer and the outer layer, because the outer layer of the bird egg fossil eggshell accounts for a particularly high proportion of the eggshell, accounting for nearly half of the eggshell thickness, just like the thick armor on the outside of the eggshell, so it is named thick helmet egg.
In ancient birds and modern birds, it is found that the outer layer of the eggshell is greater than or equal to the thickness of the continuous layer of the bird eggs are very few, from the existing research results, only the red-footed sandpiper, crested wheat chicken, the western green bully, Elijah friam and a few other bird egg shells have similar structures, because these living birds belong to different evolutionary branches, they speculate that this special eggshell structure may be the result of convergent evolution.
The restoration of Chinese dragon birds living in the Early Cretaceous period is from the same period as the bird egg fossils found in Jinyun
Birds are known to be one of the most prosperous vertebrates on Earth today, but mesozoic bird fossils are not common. Zhejiang Province has extensive Mesozoic sediments and abundant fossils, but bird fossils are very rare. So far, the bird fossils found in Zhejiang are mainly footprint fossils and suspected bird skeleton fossils, footprint fossils found in Dongyang, Zhejiang, the same era as Jinyun thick helmeted egg; skeleton fossils were unearthed in the northeast of Yandang Mountain, for the long-tailed Goose Dang bird, once considered to be a long-tailed basal bird similar to Archaeopteryx, but since then some scholars believe that it is a non-avian theropod dinosaur. Jinyun thick helmet egg is also the first bird egg fossil found in Zhejiang Province so far.
Why are bird egg fossils so rare? Dr. Jin Xingsheng said that unlike dinosaur eggs, which are a nest once found, the number of bird egg fossils is small, and they are small, not easy to preserve, and then not easy to obtain.
In addition, Jinyun thick helmet egg belongs to the Early Cretaceous period, and the bird fossils found before belong to the Late Cretaceous period, so its discovery not only enriches the species of early Cretaceous bird fossils in Zhejiang Province, but also pushes the appearance time of bird egg fossils forward to the Early Cretaceous period, and the strange three-layer structure of the thick helmet egg shell will also provide evidence for future egg fossil evolution models.