Weddell Seal (Leptonychotes wedelli) is found primarily around the shores of Antarctica. However, it does range northwards and has been found along much of the coast of Argentina and north to New Zealand. This is a large seal that can weigh over 950 pounds.

True seals or earless seals (Family Phocidae) are found at both poles and in the Mediterranean. The twenty species are organized into thirteen different genera.

A partial list of the seals is as follows:

  SPECIES                  COMMON NAME  LOCATION    

  Cystophora cristata      Hooded       N. Atlantic, Arctic Ocean
  Erignathus barbatus      Bearded      Arctic
    
  Halichoerus grypus       Gray         North Atlantic
  Histriophoca fasciata    Ribbon       Arctic Ocean, Alaska
      
  Hydrurga leptonyx        Sea Leopard  South Pacific
  Leptonychotes weddeli    Weddell's    South Pacific
    
  Lobodon carcinophagus    Crab Eating  Antarctic
  Mirounga angustirostris  Elephant     California
      
  Mirounga leonina         S.Elephant   S. Atlantic & S. Pacific
  Monachus schauinslandi   Hawaii       Hawaiian Islands  
    
  Monachus monachus        Monk         Mediterranean
  Monachus tropicalis      Car. Monk    Caribbean
      
  Pagophilus groenlandicus Harp         Arctic, North Atlantic  
  Phoca vitulina           Harbor       Widespread N Hemisphere
    
  Pusa hispida             Ringed       Arctic Ocean, etcetera
  Pusa sibirica            Nerpa        Lake Baikal in N. Eurasia

Walruses and Seals (Order Pinnipedia) are a group of marine animals that are especially abundant in cold areas particularly near the poles. These animals are characterized by front and rear legs that have modified into flippers for swimming. They spend most of their lives in water, and are not especially adapted for living on land. Most species feed on fish, marine Crustacea, and other vertebrates. Because these animals are closely related to the carnivores, they could be combined with the carnivore group into one large order.

Mammals (Class Mammalia), together with the birds, are among the youngest of the classes of animals. In species count, mammals number about fifty-one hundred, trailing reptiles (approximately fifty-five hundred), fish (approximately eighteen thousand), and birds (approximately eighty-six hundred).

There are three sub-types of mammals:

   monotremes, the most primitive:
      Develop in reptilian-like eggs and suckle milk emerging
      (i.e., spiny anteater, duckbilled platypus)

   marsupials
      Newborn emerges very underdeveloped and continue to
      mature in a pouch on its mother's abdomen (i.e., opossums,
      koala, kangaroo)

   placental  
      Embryo develops within the uterus of the female and is
      dependent on a placenta for nutrition and waste removal
      (i.e., humans, lions, monkeys)  

About sixty-five million years ago, the Tertiary era produced thirty-five orders of mammals. Of this number, eighteen have survived to represent Earth's most diversified as well as its most highly developed classification of animals.

Extinction of mammals is fast becoming a serious issue. Duff and Lawson present a list of forty-one extinct species that reached extinction prior to 1800. These forty-one species are not acknowledged in the counts of the various families. Duff and Lawson also present a list of forty-six species including three gazelles, one zebra, one seal, one deer, and one wolf that have probably gone extinct since 1800. These forty-six species are included in the family counts. Science is adding about forty to fifty new species a year to the list. Many of these are the result of divisions of prior species; some are recent discoveries.

Mammals owe their survival to adaptive capabilities that include the ability to exploit whatever sources of food are available to them, as well as their ability to adjust to various climes. Food specialization influenced evolution to such a great extent that the teeth structure can and has been used to provide extensive information on the food needs and various lifestyles of extinct species.

Despite the vast diversity among mammals in terms of size, habitats and adaptations, they share without exception many characteristics such as:  

    a. body hair
    b. mammary glands
    c. certain skull characteristics
    d. four limbs that permit speed
    e. parallel not perpendicular limbs
    f. compartmentalized internal organs
    g. a four-chambered heart and pulmonary circulation

Backboned Animals (Phylum Chordata) are the most advanced group of animals on earth. These animals are characterized by having a spinal cord or backbone. Most members have a clearly defined brain that controls the organism through a spinal cord. Fish, amphibians, reptiles, birds, and mammals are in this phylum.

Currently, some taxonomists believe that the fish should be divided into two groups (sharks and regular fishes) and that there are some other primitive groups in the phylum such as hagfish or lampreys.

Animal Kingdom contains numerous organisms that feed on other animals or plants. Included in the animal kingdom are the lower marine invertebrates such as sponges and corals, the jointed legged animals such as insects and spiders, and the backboned animals such as fish, amphibians, reptiles, birds, and mammals.