So far, no ostrich fossils have been found in China, and there are few in other parts of the world. So far, the first reliable record is Eocene, about 60-40 million years ago, which is even older than the eagle raptors. Some people speculate that ostriches occurred earlier than this, perhaps in the Paleocene 70-60 million years ago, or even earlier to the late Mesozoic, but the existing data can not fully explain the early evolution of Mesozoic ostriches, nor can they determine what kind of birds their ancestors were.
At the end of Mesozoic Cretaceous, flowering plants were dominant, and large dinosaurs among animals were almost extinct. At this time, a bird appeared, probably the ancestor of an owl, which was found in the upper Cretaceous siltation in Romania. It was identified as a kind of pelican in 19 13, but the recent re-study results show that this fossil specimen has many characteristics of carnivorous birds. If this new view can be established, then it is the ancestor of the earliest known ostriches.
Since then, in the Eocene strata of North America, the fossils of the original owl have been found, belonging to the original owl family, with 5 species. In the Miocene strata of France, there are species of grass owl, and in the Miocene strata of Germany, there are fossils of the genus Hornowl. Fossils of the genus Gallus are found in the upper Eocene or lower Oligocene and Miocene strata in France. The earliest fossils of Zanthoxylum were also found in Miocene strata in Germany and North America. The earliest earowl fossils were found in the Upper Eocene or the Lower Oligocene in France.
By the Quaternary Pleistocene, 300- 1000 years ago, the climate was greatly cooled and the world entered the ice age. However, the cold climate during this period did not completely cover the whole world, making the earth a big moraine. In fact, many areas have not been attacked by glaciers, and even the affected areas are often hot and cold. In this geological era, the number of bird fossils has increased significantly. * * * There are 46 species of passerine birds found in the world, and 40 species of passerine birds, of which 10 has been extinct. There are 6 species of birds in the family Fagaceae, 5 of which are extinct, and most of them continue to this day, indicating that the birds in the family Fagaceae began to adapt to radiation, differentiated into a large number of different species and spread to the whole world. During this period, the diversity of modern mammals has been established. There are many small mammals that are nocturnal in the newly emerging grasslands and forests. Therefore, ostriches whose main food is ostrich gradually become nocturnal birds.