PELVIC GIRDLES IN VARIOUS VERTEBRATE GROUPS

• PELVIC GIRDLES IN VARIOUS VERTEBRATE GROUPS

  FISHES

  ● their pelvic girdles consist of a pair of simple cartilaginous or bony pelvic (ischiopubic) plates that meets in midventral pelvic symphysis and braces the pelvic fins.

  
• PELVIC GIRDLES IN VARIOUS VERTEBRATE GROUPS

  TETRAPODS

  ● also develops cartilaginous pelvic plates, forming a pubis (pubic bone) and more posterior ischium.

  ● ilium arises dorsal to the pelvic plate.

  ● pubis, ischium, ilium, a socket, and acetabulum accommodate the head of the femur.

  A) ISHIOPUBIC FENESTRA

  B) PUBIS

  C) ILIUM

  D) ACETABULUM

  E) ISCHIUM

  F) EPIPUBIS

  G) SYMPHYSIS

  H) HYPOISCHIUM

  
• PELVIC GIRDLES IN VARIOUS VERTEBRATE GROUPS

  AMNIOTES

  ● they also have three paired elements in their pelvic girdle: the ilium, pubis, and ischium.

  ● the sacrum and girdle are often united, forming a bony structure called the pelvis that encircles the caudal end of their coelom.

  ● the pelvic cavity then holds the urogenital organs and end portion of intestines.

  A) EPIPUBIS

  B) ILIUM

  C) TRANSVERSE PROCESS

  D) LUMBAR VERTEBRA

  E) SACRAL VERTEBRA

  F) CAUDAL VERTEBRA

  G) HYPOISCHIUM

  H) ISCHIUM

  I) PUBIS

  
• PELVIC GIRDLES IN VARIOUS VERTEBRATE GROUPS


  MAMMALS

  ● the ilium, ischium, and pubis ankylose form a left and right innominate (coxal) bone.

  ● the pubis and ischia meet in a pubic or ischiopubic symphysis to complete the walls of a pelvic activity.

  ● young mammals are delivered through the pelvic outlet and relaxin, an ovarian hormone, softens the fibrocartilage separating the bones, permitting expansion for delivery.

  
• KEY POINTS TO REMEMBER:

  ● There are no dermal bones in pelvic girdle.

  ● The pelvic girdle consists of two pelvic (ischiopubic) plates.

  ● In tetrapods, two ossification centers in each pelvic plate become ischial and pubic bones.

  ● An ilium braces the girdle against the vertebral column.

  ● Ilium, ischium, and pubis unite to form an innominate bone (coxa) in mammals.

  ● The sacrum and pelvic girdle of mammals and some reptiles constitute a pelvis that encompasses a pelvic cavity.
• FINS AND LIMBS

  FINS

  Lepidotrichia - fins of bony fishes

  Ceratotrichia - fins of cartilaginous fishes

  Actinotrichia - can occur in both.

  
• PAIRED FINS

  1. Lobed fins
  2. Fin fold fins
  3. Ray fins
• MEDIAN FINS


  MEDIAN FINS

  • One or 2 or a series of median dorsal fins, midventral anal fin.
  • Act as keels, keep motionless fish from rolling, rarely used for locomotion

  
• CAUDAL FINS

  CAUDAL FINS Classified by shape and direction taken by terminal portion of the notochord and ventral column. Types:

  1. Heterocercal - notochord turns upward
  2. Hypocercal - vertebral column turns downward

  Conventionally

  1. Diphycercal - vertebral column end with little upbending (Dipnoans and Latemria)
  2. Homocercal - the notochord encased in urostyle turns far dorsal.
• ORIGINS OF FINS

  ● Fin fold hypothesis - derived from a pair of continuous fleshy folds of lateral body wall.

  ● Gill arch hypothesis - pectoral and pelvic girdles are modified gill arches.

  ● Fin spine hypothesis - paired fins goes back to Ostracoderms which are regarded as the ancestors of the existing cyclostomes.
• TETRAPOD LIMBS

  ● Typically, four limbs, some lost one or both pairs, modified in some as wings or paddles.

  ● Early limbs were short.

  ● Other reptiles and mammals modified limbs.

  ● From aquatic to terrestrial adaptations

  3 segments:

  1. Propodium
  2. Epipodium
  3. Autopodium

  
• PROPODIUM & EPIPODIUM

  ● Humerus, variates in different tetrapods

  ● Radius, ulna bones in forearm

  ● Femur, tibia, fibula, both may unite to form tibiofibula, in frogs, reduced to splinter in birds, lost in deer.

  ● Sessamoid bone - patella / kneecap, developed in birds and mammals, ossifies in the tendon.

  ● Tibiotarsus in birds
• MANUS

  ● Manus: the hand ● Wrist palm, digits ● Adaptation Devonian species:

  1. Complete hind limbs of Ichytostega has 7 digits
  2. Complete forelimb Acanthostega 8 digits.
  3. Tulerpeton 6 digits ▪ wrist, radiale, ulnare, intermedium ▪ pisiform, centralia, distal carpals, metacarpals, phalanges

  
• FLIGHT 


  FLIGHT

  ● Adaptations for flight

  ● Bats, gliding lemurs

  
• LIFE IN OCEAN 


  LIFE IN OCEAN The hands have become paddle like flippers in well adapted marine amniotes.

  • flat and stout flippers

  
• NEED FOR SPEED

  ● Plantigrade - mammals with wrist, ankles, digits rest on the ground.

  ● Digitigrade - mammals with only the 1st digit reduces, Ungulata.

  ● Artiodactyl - weight distributed between digits.

  ● Paraxonic -weight is distributed on 2 parallel axes.

  
• GRASPING


  Many mammals can flex their hand at the joint between palm and fingers like rodents.

  ● opposable thumbs in Old World Monkeys

  
• PES: HIND FOOT


  ● The pes is comparable bone for bone with the manus.

  ● Early tetrapods had four centralia in the ankle.

  ● the number of central bones diminished over time.

  
• PINNIPEDS' MANEUVER ON LAND

  ● fur seals, sea lions, walruses come to land more often than wriggling seals.

  
• ORIGIN OF LIMBS

  ● ancient, paired fins precursors to tetrapod limbs.

  ● transition from fins to limbs:

  ▪ elongation of bones

  ▪ formation of hinge joints ▪ rotation of humerus and femur

  ● occurred during the devonian period.

  
• LIMBLESS LOCOMOTION

  • Adaptation for limbless tetrapods:

  ▪ modified vertebral column.

  ▪ modified ribs

  ▪ body wall musculature.

  • move by forming irregular loops.
  • serpentine or lateral undulation.
  • Sidewinding