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
Galápagos shearwater white. It sometimes has a dark collar. Both sexes are alike, as are the young after fledging. It is a slender-bodied shearwater, about 29–31 cm long, with a wingspan of around 63 cm and weighs 123-225 g. The species closely resembles the tropical shearwater, although the latter is typically blacker and has a longer tail. The Galápagos shearwater is a gregarious species and will feed at sea with other shearwaters and boobies. It flies low over the water and feeds on squid, fish and offal. It intersperses 4-10 stiff wing beats with shallow glides. Galápagos shearwater The Galápagos shearwater ("Puffinus