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
Chagos Archipelago fuscata"), brown and lesser noddies ("Anous stolidus" and "Anous tenuirostris") wedge-tailed shearwaters ("Puffinus pacificus") and red-footed boobies ("Sula sula"). Land bird fauna is poor and consists of introduced species and recent natural colonisers. Red fody had been introduced and now widespread. Environments of Chagos Archipelago provides rich biodiversity and support varieties of cetacean species within the vicinity, such as three populations of blue whales and toothed whales (sperm, pilot, orca, pseudo-orca, risso's and other dolphins such as spinners, and so on). Dugongs, being locally extinct today, once thrived in the archipelago and the Sea Cow Island was named after the