Dark matter is different from baryonic matter.
The diving petrels are seabirds in the bird order Procellariiformes .. Procellariiformes. Procellariiformes. bird. bird. There are four very similar species all in the family Procellariidae and genus Pelecanoides -LRB- Lacepede , 1799 -RRB- , distinguished only by small differences in the coloration of their plumage and their bill construction .. Procellariidae. Procellariidae. Lacepede. Bernard Germain Etienne de la Ville, Comte de Lacepede. plumage. plumage. bill. beak. They are only found in the Southern Hemisphere .. Diving petrels are auk-like small petrels of the southern oceans .. auk. auk. The resemblances with the auks are due to convergent evolution , since both families feed by pursuit diving , although some researchers have in the past suggested that the similarities are due to relatedness .. convergent evolution. convergent evolution. families. family ( biology ). Among the Procellariiformes the diving petrels are the family most adapted to life in the sea rather than flying over it , and are generally found closer inshore than other families in the order .. Procellariiformes. Procellariiformes. families. family ( biology ). Diving petrels are plankton feeders , taking mostly crustacean prey such as krill , copepods and the amphipod Themisto gaudichaudii , also taking small fish and squid .. plankton. plankton. crustacean. crustacean. krill. krill. amphipod. amphipod. Themisto gaudichaudii. Themisto gaudichaudii. squid. squid. They have several adaptations for obtaining their prey including short powerful wings , a gular pouch for storing food , and their nostrils open upwards rather than pointing forward as in other tubenoses .. gular pouch. gular pouch