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
Shearwater Shearwater Shearwaters are medium-sized long-winged seabirds. There are more than 30 species of shearwaters, a few larger ones in the genus "Calonectris" and many smaller species in the genus "Puffinus". The "Procellaria" petrels and "Bulweria" were believed to belong to this group, but are only distantly related based on more recent studies, while the "Pseudobulweria" and "Lugensa" "petrels" are more closely related. The genus "Puffinus" can be divided into a group of small species close to "Calonectris" and a few larger ones more distantly related to both. These birds are most common in temperate and cold waters. They are pelagic