The staff of the Paleontological Institute named after A. A. borisyak RAS shells of various species of extinct ostrich-like found that the first owls of the modern type came about eight million years ago in the North-Western black sea and from there migrated to Africa. Interestingly, the first members of the order appeared 23 million years ago in Africa. Thus, it appears that the ostrich-like during its existence has made the migration from the dark continent and back (now they are not found anywhere except in Africa), reported in Earth-Science Reviews.
Compared to many other groups of birds, ostrich-like are well represented in the fossil record, and not primarily by the skeletal fragments, and a thick egg shell (some species are known only by her, their bones remained). It has microscopic pores, the location of which differs depending on the species or even subspecies of a bird. This feature of the eggs can be used to establish the relationship between the modern and fossil species of ostriches. And if you know the age of each sample, you can also understand when one of them arose.
Nikita Zelenkov and Konstantin Mikhailov, from the Paleontological Institute named after A. A. borisyakn Academy of Sciences compared the patterns on the shells of extinct and extant ostriches and arrangement, and the form of indentations on it and on its thickness divided them into several groups (A, S, As, Sn, Sd, Ss). In addition, the researchers also collected data on the existing bones of these birds.