Edentata-Artiodactyla-Cetacea, Biology tutorial

Eutherians: edentata, artiodactyla, cetacea

Features of Order Edentata (armadillos, sloths):

Members of the eutherian order are known to:

  • contain reduced or no teeth
  • lack enamel (hard thin calcium-containing covering of crown of tooth)
  • contain heavily clawed forelimbs for burrowing.

All Armadillos are hard bone-plated animals. Hard armour-plated carapace that covers the bodies may just be one-solid armour in some while in others; armour is constructed of hinged bands that permit creature to roll in ball. Most are about size of cat but giant armadillo reaches 0.9 m (3 ft) in length and can weigh 59kg (130 lbs).

Armadillos are found in southern part of United States and in Central and South America. Sloths are normally known as lazy animals on account of the slow movement. Certainly, they are slowest mammals. Sloth spends most of days alone, hanging upturned from tree branches, feasting on leaves. On account of the sedentary habit, algae grow in fur and this assists animal to camouflage from its predators like birds. Pale-throated three-toed sloth, Bradypus variegatus, with the black face and white band across forehead, is found in Honduras and Argentina.

Characteristics of Order Artiodactyla (like pigs,sheep, cattle, antelopes, deer, giraffes, hippopotamus) Members of this order have:

  • Hooves with even number of toes (like 2, 4)
  • Bone in the ankle joint (astragalus) with the double-pulley structure which gives foot greater flexibility.

Artiodactyls are the large and extraordinarily diverse group of mammals. Majority live in relatively open habitats, like plains and savannahs, but others live in forests, and one group is semi-aquatic.

Within this order are some of the fastest-running mammals like antelopes and deer, and comparatively slow moving species like pigs and hippopotamus. Artiodactyls are paraxonic (that is plane of symmetry passes between third and fourth digits). In all species number of digits is decreased at least by loss of first digit, and second and fifth digits are small in many. Third and fourth digits, though, remain large and bear weight in all artiodactyls. This pattern has earned them their name Artiodactyla, that means even-toed.

Features of Order Cetacea (like whales, dolphins) Members of order Cetacea contain the following features:

  • they are aquatic
  • Have blowholes on their heads
  • Have flipper-like forelimbs
  • Hind limbs are vestigial
  • Tails are elongated to flukes (like a caudal fin)

Cetaceans are comparatively large, usually characterized by streamlined bodies which glide effortlessly through marine environment. Cetacea are one of the most characteristic and highly specialized orders of mammals. They comprise largest animal which has ever lived, blue whale; highly intelligent and communicative dolphins; tusked narwhals and blind river dolphins and singing humpback whales - almost 80 living species in all. Though hunting and other human activities have endangered most cetacean species, outlook for several is improving. Whales are extremely specialized for life in water. Many species are marine but dolphin species are found in Yangtze, Amazon, Parana, Indus and Ganges Rivers. Whales have stream-like bodies with extremely compressed neck vertebrae, dorsal fins, and tail with two finlike flukes set horizontally. Modern whales have really lengthened anterior skull bones, and nostrils are located on top of head, creating blowhole. Forelimbs are specialized to form flippers, and hind limbs and pelvis are very small and don't normally extend out of body wall of animal.

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