Comparative study of Pelvic Girdles of vertebrate

Scoliodon Pelvic Girdle and Fins

Comments

• Pelvic girdle : Made up of a simple flattened and transverse cartilaginous rod called ischiopubic bar, having a small blunt iliac process on either side projecting above the acetabular facet for articulation of the basal cartilage of pelvic fin.
• Pelvic fins : Skeleton of a pelvic fin has a single large and curved basal cartilage called as basipterygium. From basipterygium 15 or more slender radials or somactidia are given. Associated with pelvic girdle in male dog-fish are claspers. Each clasper contains accessory piece, dorsal covering plate, ventral sheath plate and style.
• Median fins : Skeleton similar to paired fins. Other structures seen are modified radials, skeleton of clasper, groove of claspers, axial cartilage ceratotrichia cut body wall glandular sac nerve foramin and opening of glandular sac into apopyle.

Pelvic Girdle of Frog

Comments

• Two pelvic girdles form a V -shaped structure. Each half of girdle or innominatum is composed of ilium, ischium and pubis which unite posteriorly into a vertical disc bearing a cup-shaped cavity, called acetabulum, on either side.
• llium
  • It is a long bone meeting with transverse process of ninth vertebra. (ii) Dorsally it contains a distinct iliac crest.
  • Two ilia meet posteriorly at an iliac symphysis.
• Pubis : It is a reduced calcified cartilage forming major part of acetabulum. The pubic cartilages of both sides are completely fused.
• Ischium : Two ischia give rise to one-third of disc and completely fuse together at an ischiatic symphysis.

Pelvic Girdle of Varanus : Left Innominate : Lateral View

Comments :

• It is composed of usual three bones, namely ilium, pubis and ischium.
• Three bones are very hard and solid.
• Externally, at the junction of three bones is a large acetabulum for head of femur. (iv) Joints are distinct.
• llium.
  • It is a rod-shaped bone constituting major part of acetabulum.
  • It articulates with sacral vertebrae.
  • It has a pre-acetabular process.
• Pubis
  • It is a curved bone.
  • Two pubes meet at a pubic symphysis, which contains a cartilage called epipubis.
  • Pubis gives out a small rod-like process called prepubis.
  • Pubis contributes to one-third of acetabulum and is perforated by a small foramen for obturator nerve.
  • Ischium
    • Two ischia are flat and curved bones meeting at an ischiatic symphysis.
    • From ischiatic symphysis, a rod-shaped hypoischium extends backwards to support ventral wall of cloaca.

Pelvic Girdle of Fowl : Outer View

Comments

• Although pelvic girdle of fowl contains usual three parts, namely ilium, ischium and pubis, yet it is noteworthy because of
  • absence of ventral symphysis due to large eggs
  • firm union with vertebral column
  • incomplete ossification of acetabulum.
• Ilium
  • Ilium is a long lamellar bone differentiated into pre-acetabular and postacetabular parts.
  • Ilium forms dorsal part of the perforated acetabulum.
• Ischium
  • It extends behind acetabulum.
  • It is fused with ilium posteriorly and separated anteriorly by an ilio-ischiatic foramen.
• Pubis
  • It is a slender bone forming ventral part of acetabulum.
  • Behind acetabulum pubis is separated from ischium by an obturator foramen.
  • Anteriorly it gives a small prepubic process.

Pelvic Girdle of Rabbit

Comments

• Two halves of pelvic girdles are united at a pubic symphysis. Each half or innominatum contains ilium, ischium and pubis. Three bones are fused together forming hip bone. External to hip bone is a cup-shaped acetabulum
• Ilium
  • It is a blade-like bone.
  • It articulates with sacrum.
• Ischium
  • It forms postero-dorsal part of innominate bone.
  • Posterior most part is thickened fonning an ischial tuberosity.
• Pubis
  • It is a small bone forming ventro-Iateral part of girdle.
  • A small cotyloid bone prevents pubis from reaching upto acetabulum.
  • Pubis is separated from ischium by a large obturator foramen.