Seabird in the Cretaceous, with a species called "Tytthostonyx glauconiticus", which seems allied to the Procellariiformes and Pelecaniformes. In the Paleogene both pterosaurs and marine reptiles became extinct, allowing seabirds to expand ecologically. These post-extinction seas were dominated by early Procellariidae, giant penguins and two extinct families, the Pelagornithidae and the Plotopteridae (a group of large seabirds that looked like the penguins). Modern genera began their wide radiation in the Miocene, although the genus "Puffinus" (which includes today's Manx shearwater and sooty shearwater) might date back to the Oligocene. The highest diversity of seabirds apparently existed during the Late Miocene and
Calonectris the Early Pliocene and "Calonectris wingatei" from the Middle Pleistocene, have also been described from fossils. "Calonectris kurodai", another fossil from the Middle Miocene Calvert Formation of Chesapeake Bay is named after the Japanese ornithologist Nagahisa Kuroda. Calonectris Calonectris is a genus of seabirds. The genus name comes from Ancient Greek "kalos", "good" and "nectris", "swimmer". The genus comprises three large shearwaters. There are two other shearwater genera. "Puffinus", which comprises about twenty small to medium-sized shearwaters, and "Procellaria "with another four large species. The latter are usually named as "petrels", although they are thought to be more closely related